1 files changed, 5108 insertions, 0 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
new file mode 100644
index 000000000000..9d0b5c665883
--- /dev/null
+++ b/kernel/perf_event.c
@@ -0,0 +1,5108 @@
+/*
+ * Performance events core code:
+ *
+ *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ *
+ * For licensing details see kernel-base/COPYING
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/sysfs.h>
+#include <linux/dcache.h>
+#include <linux/percpu.h>
+#include <linux/ptrace.h>
+#include <linux/vmstat.h>
+#include <linux/vmalloc.h>
+#include <linux/hardirq.h>
+#include <linux/rculist.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/anon_inodes.h>
+#include <linux/kernel_stat.h>
+#include <linux/perf_event.h>
+
+#include <asm/irq_regs.h>
+
+/*
+ * Each CPU has a list of per CPU events:
+ */
+DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
+
+int perf_max_events __read_mostly = 1;
+static int perf_reserved_percpu __read_mostly;
+static int perf_overcommit __read_mostly = 1;
+
+static atomic_t nr_events __read_mostly;
+static atomic_t nr_mmap_events __read_mostly;
+static atomic_t nr_comm_events __read_mostly;
+static atomic_t nr_task_events __read_mostly;
+
+/*
+ * perf event paranoia level:
+ *  -1 - not paranoid at all
+ *   0 - disallow raw tracepoint access for unpriv
+ *   1 - disallow cpu events for unpriv
+ *   2 - disallow kernel profiling for unpriv
+ */
+int sysctl_perf_event_paranoid __read_mostly = 1;
+
+static inline bool perf_paranoid_tracepoint_raw(void)
+{
+        return sysctl_perf_event_paranoid > -1;
+}
+
+static inline bool perf_paranoid_cpu(void)
+{
+        return sysctl_perf_event_paranoid > 0;
+}
+
+static inline bool perf_paranoid_kernel(void)
+{
+        return sysctl_perf_event_paranoid > 1;
+}
+
+int sysctl_perf_event_mlock __read_mostly = 512; /* 'free' kb per user */
+
+/*
+ * max perf event sample rate
+ */
+int sysctl_perf_event_sample_rate __read_mostly = 100000;
+
+static atomic64_t perf_event_id;
+
+/*
+ * Lock for (sysadmin-configurable) event reservations:
+ */
+static DEFINE_SPINLOCK(perf_resource_lock);
+
+/*
+ * Architecture provided APIs - weak aliases:
+ */
+extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event)
+{
+        return NULL;
+}
+
+void __weak hw_perf_disable(void)               { barrier(); }
+void __weak hw_perf_enable(void)                { barrier(); }
+
+void __weak hw_perf_event_setup(int cpu)        { barrier(); }
+void __weak hw_perf_event_setup_online(int cpu) { barrier(); }
+
+int __weak
+hw_perf_group_sched_in(struct perf_event *group_leader,
+               struct perf_cpu_context *cpuctx,
+               struct perf_event_context *ctx, int cpu)
+{
+        return 0;
+}
+
+void __weak perf_event_print_debug(void)        { }
+
+static DEFINE_PER_CPU(int, perf_disable_count);
+
+void __perf_disable(void)
+{
+        __get_cpu_var(perf_disable_count)++;
+}
+
+bool __perf_enable(void)
+{
+        return !--__get_cpu_var(perf_disable_count);
+}
+
+void perf_disable(void)
+{
+        __perf_disable();
+        hw_perf_disable();
+}
+
+void perf_enable(void)
+{
+        if (__perf_enable())
+                hw_perf_enable();
+}
+
+static void get_ctx(struct perf_event_context *ctx)
+{
+        WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
+}
+
+static void free_ctx(struct rcu_head *head)
+{
+        struct perf_event_context *ctx;
+
+        ctx = container_of(head, struct perf_event_context, rcu_head);
+        kfree(ctx);
+}
+
+static void put_ctx(struct perf_event_context *ctx)
+{
+        if (atomic_dec_and_test(&ctx->refcount)) {
+                if (ctx->parent_ctx)
+                        put_ctx(ctx->parent_ctx);
+                if (ctx->task)
+                        put_task_struct(ctx->task);
+                call_rcu(&ctx->rcu_head, free_ctx);
+        }
+}
+
+static void unclone_ctx(struct perf_event_context *ctx)
+{
+        if (ctx->parent_ctx) {
+                put_ctx(ctx->parent_ctx);
+                ctx->parent_ctx = NULL;
+        }
+}
+
+/*
+ * If we inherit events we want to return the parent event id
+ * to userspace.
+ */
+static u64 primary_event_id(struct perf_event *event)
+{
+        u64 id = event->id;
+
+        if (event->parent)
+                id = event->parent->id;
+
+        return id;
+}
+
+/*
+ * Get the perf_event_context for a task and lock it.
+ * This has to cope with with the fact that until it is locked,
+ * the context could get moved to another task.
+ */
+static struct perf_event_context *
+perf_lock_task_context(struct task_struct *task, unsigned long *flags)
+{
+        struct perf_event_context *ctx;
+
+        rcu_read_lock();
+ retry:
+        ctx = rcu_dereference(task->perf_event_ctxp);
+        if (ctx) {
+                /*
+                 * If this context is a clone of another, it might
+                 * get swapped for another underneath us by
+                 * perf_event_task_sched_out, though the
+                 * rcu_read_lock() protects us from any context
+                 * getting freed.  Lock the context and check if it
+                 * got swapped before we could get the lock, and retry
+                 * if so.  If we locked the right context, then it
+                 * can't get swapped on us any more.
+                 */
+                spin_lock_irqsave(&ctx->lock, *flags);
+                if (ctx != rcu_dereference(task->perf_event_ctxp)) {
+                        spin_unlock_irqrestore(&ctx->lock, *flags);
+                        goto retry;
+                }
+
+                if (!atomic_inc_not_zero(&ctx->refcount)) {
+                        spin_unlock_irqrestore(&ctx->lock, *flags);
+                        ctx = NULL;
+                }
+        }
+        rcu_read_unlock();
+        return ctx;
+}
+
+/*
+ * Get the context for a task and increment its pin_count so it
+ * can't get swapped to another task.  This also increments its
+ * reference count so that the context can't get freed.
+ */
+static struct perf_event_context *perf_pin_task_context(struct task_struct *task)
+{
+        struct perf_event_context *ctx;
+        unsigned long flags;
+
+        ctx = perf_lock_task_context(task, &flags);
+        if (ctx) {
+                ++ctx->pin_count;
+                spin_unlock_irqrestore(&ctx->lock, flags);
+        }
+        return ctx;
+}
+
+static void perf_unpin_context(struct perf_event_context *ctx)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&ctx->lock, flags);
+        --ctx->pin_count;
+        spin_unlock_irqrestore(&ctx->lock, flags);
+        put_ctx(ctx);
+}
+
+/*
+ * Add a event from the lists for its context.
+ * Must be called with ctx->mutex and ctx->lock held.
+ */
+static void
+list_add_event(struct perf_event *event, struct perf_event_context *ctx)
+{
+        struct perf_event *group_leader = event->group_leader;
+
+        /*
+         * Depending on whether it is a standalone or sibling event,
+         * add it straight to the context's event list, or to the group
+         * leader's sibling list:
+         */
+        if (group_leader == event)
+                list_add_tail(&event->group_entry, &ctx->group_list);
+        else {
+                list_add_tail(&event->group_entry, &group_leader->sibling_list);
+                group_leader->nr_siblings++;
+        }
+
+        list_add_rcu(&event->event_entry, &ctx->event_list);
+        ctx->nr_events++;
+        if (event->attr.inherit_stat)
+                ctx->nr_stat++;
+}
+
+/*
+ * Remove a event from the lists for its context.
+ * Must be called with ctx->mutex and ctx->lock held.
+ */
+static void
+list_del_event(struct perf_event *event, struct perf_event_context *ctx)
+{
+        struct perf_event *sibling, *tmp;
+
+        if (list_empty(&event->group_entry))
+                return;
+        ctx->nr_events--;
+        if (event->attr.inherit_stat)
+                ctx->nr_stat--;
+
+        list_del_init(&event->group_entry);
+        list_del_rcu(&event->event_entry);
+
+        if (event->group_leader != event)
+                event->group_leader->nr_siblings--;
+
+        /*
+         * If this was a group event with sibling events then
+         * upgrade the siblings to singleton events by adding them
+         * to the context list directly:
+         */
+        list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
+
+                list_move_tail(&sibling->group_entry, &ctx->group_list);
+                sibling->group_leader = sibling;
+        }
+}
+
+static void
+event_sched_out(struct perf_event *event,
+                  struct perf_cpu_context *cpuctx,
+                  struct perf_event_context *ctx)
+{
+        if (event->state != PERF_EVENT_STATE_ACTIVE)
+                return;
+
+        event->state = PERF_EVENT_STATE_INACTIVE;
+        if (event->pending_disable) {
+                event->pending_disable = 0;
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+        event->tstamp_stopped = ctx->time;
+        event->pmu->disable(event);
+        event->oncpu = -1;
+
+        if (!is_software_event(event))
+                cpuctx->active_oncpu--;
+        ctx->nr_active--;
+        if (event->attr.exclusive || !cpuctx->active_oncpu)
+                cpuctx->exclusive = 0;
+}
+
+static void
+group_sched_out(struct perf_event *group_event,
+                struct perf_cpu_context *cpuctx,
+                struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+
+        if (group_event->state != PERF_EVENT_STATE_ACTIVE)
+                return;
+
+        event_sched_out(group_event, cpuctx, ctx);
+
+        /*
+         * Schedule out siblings (if any):
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry)
+                event_sched_out(event, cpuctx, ctx);
+
+        if (group_event->attr.exclusive)
+                cpuctx->exclusive = 0;
+}
+
+/*
+ * Cross CPU call to remove a performance event
+ *
+ * We disable the event on the hardware level first. After that we
+ * remove it from the context list.
+ */
+static void __perf_event_remove_from_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu. If not it has been
+         * scheduled out before the smp call arrived.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        spin_lock(&ctx->lock);
+        /*
+         * Protect the list operation against NMI by disabling the
+         * events on a global level.
+         */
+        perf_disable();
+
+        event_sched_out(event, cpuctx, ctx);
+
+        list_del_event(event, ctx);
+
+        if (!ctx->task) {
+                /*
+                 * Allow more per task events with respect to the
+                 * reservation:
+                 */
+                cpuctx->max_pertask =
+                        min(perf_max_events - ctx->nr_events,
+                            perf_max_events - perf_reserved_percpu);
+        }
+
+        perf_enable();
+        spin_unlock(&ctx->lock);
+}
+
+
+/*
+ * Remove the event from a task's (or a CPU's) list of events.
+ *
+ * Must be called with ctx->mutex held.
+ *
+ * CPU events are removed with a smp call. For task events we only
+ * call when the task is on a CPU.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This is OK when called from perf_release since
+ * that only calls us on the top-level context, which can't be a clone.
+ * When called from perf_event_exit_task, it's OK because the
+ * context has been detached from its task.
+ */
+static void perf_event_remove_from_context(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Per cpu events are removed via an smp call and
+                 * the removal is always sucessful.
+                 */
+                smp_call_function_single(event->cpu,
+                                         __perf_event_remove_from_context,
+                                         event, 1);
+                return;
+        }
+
+retry:
+        task_oncpu_function_call(task, __perf_event_remove_from_context,
+                                 event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the context is active we need to retry the smp call.
+         */
+        if (ctx->nr_active && !list_empty(&event->group_entry)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can remove the event safely, if the call above did not
+         * succeed.
+         */
+        if (!list_empty(&event->group_entry)) {
+                list_del_event(event, ctx);
+        }
+        spin_unlock_irq(&ctx->lock);
+}
+
+static inline u64 perf_clock(void)
+{
+        return cpu_clock(smp_processor_id());
+}
+
+/*
+ * Update the record of the current time in a context.
+ */
+static void update_context_time(struct perf_event_context *ctx)
+{
+        u64 now = perf_clock();
+
+        ctx->time += now - ctx->timestamp;
+        ctx->timestamp = now;
+}
+
+/*
+ * Update the total_time_enabled and total_time_running fields for a event.
+ */
+static void update_event_times(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        u64 run_end;
+
+        if (event->state < PERF_EVENT_STATE_INACTIVE ||
+            event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
+                return;
+
+        event->total_time_enabled = ctx->time - event->tstamp_enabled;
+
+        if (event->state == PERF_EVENT_STATE_INACTIVE)
+                run_end = event->tstamp_stopped;
+        else
+                run_end = ctx->time;
+
+        event->total_time_running = run_end - event->tstamp_running;
+}
+
+/*
+ * Update total_time_enabled and total_time_running for all events in a group.
+ */
+static void update_group_times(struct perf_event *leader)
+{
+        struct perf_event *event;
+
+        update_event_times(leader);
+        list_for_each_entry(event, &leader->sibling_list, group_entry)
+                update_event_times(event);
+}
+
+/*
+ * Cross CPU call to disable a performance event
+ */
+static void __perf_event_disable(void *info)
+{
+        struct perf_event *event = info;
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = event->ctx;
+
+        /*
+         * If this is a per-task event, need to check whether this
+         * event's task is the current task on this cpu.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        spin_lock(&ctx->lock);
+
+        /*
+         * If the event is on, turn it off.
+         * If it is in error state, leave it in error state.
+         */
+        if (event->state >= PERF_EVENT_STATE_INACTIVE) {
+                update_context_time(ctx);
+                update_group_times(event);
+                if (event == event->group_leader)
+                        group_sched_out(event, cpuctx, ctx);
+                else
+                        event_sched_out(event, cpuctx, ctx);
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Disable a event.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This condition is satisifed when called through
+ * perf_event_for_each_child or perf_event_for_each because they
+ * hold the top-level event's child_mutex, so any descendant that
+ * goes to exit will block in sync_child_event.
+ * When called from perf_pending_event it's OK because event->ctx
+ * is the current context on this CPU and preemption is disabled,
+ * hence we can't get into perf_event_task_sched_out for this context.
+ */
+static void perf_event_disable(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Disable the event on the cpu that it's on
+                 */
+                smp_call_function_single(event->cpu, __perf_event_disable,
+                                         event, 1);
+                return;
+        }
+
+ retry:
+        task_oncpu_function_call(task, __perf_event_disable, event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the event is still active, we need to retry the cross-call.
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * Since we have the lock this context can't be scheduled
+         * in, so we can change the state safely.
+         */
+        if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                update_group_times(event);
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+
+        spin_unlock_irq(&ctx->lock);
+}
+
+static int
+event_sched_in(struct perf_event *event,
+                 struct perf_cpu_context *cpuctx,
+                 struct perf_event_context *ctx,
+                 int cpu)
+{
+        if (event->state <= PERF_EVENT_STATE_OFF)
+                return 0;
+
+        event->state = PERF_EVENT_STATE_ACTIVE;
+        event->oncpu = cpu;     /* TODO: put 'cpu' into cpuctx->cpu */
+        /*
+         * The new state must be visible before we turn it on in the hardware:
+         */
+        smp_wmb();
+
+        if (event->pmu->enable(event)) {
+                event->state = PERF_EVENT_STATE_INACTIVE;
+                event->oncpu = -1;
+                return -EAGAIN;
+        }
+
+        event->tstamp_running += ctx->time - event->tstamp_stopped;
+
+        if (!is_software_event(event))
+                cpuctx->active_oncpu++;
+        ctx->nr_active++;
+
+        if (event->attr.exclusive)
+                cpuctx->exclusive = 1;
+
+        return 0;
+}
+
+static int
+group_sched_in(struct perf_event *group_event,
+               struct perf_cpu_context *cpuctx,
+               struct perf_event_context *ctx,
+               int cpu)
+{
+        struct perf_event *event, *partial_group;
+        int ret;
+
+        if (group_event->state == PERF_EVENT_STATE_OFF)
+                return 0;
+
+        ret = hw_perf_group_sched_in(group_event, cpuctx, ctx, cpu);
+        if (ret)
+                return ret < 0 ? ret : 0;
+
+        if (event_sched_in(group_event, cpuctx, ctx, cpu))
+                return -EAGAIN;
+
+        /*
+         * Schedule in siblings as one group (if any):
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry) {
+                if (event_sched_in(event, cpuctx, ctx, cpu)) {
+                        partial_group = event;
+                        goto group_error;
+                }
+        }
+
+        return 0;
+
+group_error:
+        /*
+         * Groups can be scheduled in as one unit only, so undo any
+         * partial group before returning:
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry) {
+                if (event == partial_group)
+                        break;
+                event_sched_out(event, cpuctx, ctx);
+        }
+        event_sched_out(group_event, cpuctx, ctx);
+
+        return -EAGAIN;
+}
+
+/*
+ * Return 1 for a group consisting entirely of software events,
+ * 0 if the group contains any hardware events.
+ */
+static int is_software_only_group(struct perf_event *leader)
+{
+        struct perf_event *event;
+
+        if (!is_software_event(leader))
+                return 0;
+
+        list_for_each_entry(event, &leader->sibling_list, group_entry)
+                if (!is_software_event(event))
+                        return 0;
+
+        return 1;
+}
+
+/*
+ * Work out whether we can put this event group on the CPU now.
+ */
+static int group_can_go_on(struct perf_event *event,
+                           struct perf_cpu_context *cpuctx,
+                           int can_add_hw)
+{
+        /*
+         * Groups consisting entirely of software events can always go on.
+         */
+        if (is_software_only_group(event))
+                return 1;
+        /*
+         * If an exclusive group is already on, no other hardware
+         * events can go on.
+         */
+        if (cpuctx->exclusive)
+                return 0;
+        /*
+         * If this group is exclusive and there are already
+         * events on the CPU, it can't go on.
+         */
+        if (event->attr.exclusive && cpuctx->active_oncpu)
+                return 0;
+        /*
+         * Otherwise, try to add it if all previous groups were able
+         * to go on.
+         */
+        return can_add_hw;
+}
+
+static void add_event_to_ctx(struct perf_event *event,
+                               struct perf_event_context *ctx)
+{
+        list_add_event(event, ctx);
+        event->tstamp_enabled = ctx->time;
+        event->tstamp_running = ctx->time;
+        event->tstamp_stopped = ctx->time;
+}
+
+/*
+ * Cross CPU call to install and enable a performance event
+ *
+ * Must be called with ctx->mutex held
+ */
+static void __perf_install_in_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *leader = event->group_leader;
+        int cpu = smp_processor_id();
+        int err;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu. If not it has been
+         * scheduled out before the smp call arrived.
+         * Or possibly this is the right context but it isn't
+         * on this cpu because it had no events.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx) {
+                if (cpuctx->task_ctx || ctx->task != current)
+                        return;
+                cpuctx->task_ctx = ctx;
+        }
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        update_context_time(ctx);
+
+        /*
+         * Protect the list operation against NMI by disabling the
+         * events on a global level. NOP for non NMI based events.
+         */
+        perf_disable();
+
+        add_event_to_ctx(event, ctx);
+
+        /*
+         * Don't put the event on if it is disabled or if
+         * it is in a group and the group isn't on.
+         */
+        if (event->state != PERF_EVENT_STATE_INACTIVE ||
+            (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE))
+                goto unlock;
+
+        /*
+         * An exclusive event can't go on if there are already active
+         * hardware events, and no hardware event can go on if there
+         * is already an exclusive event on.
+         */
+        if (!group_can_go_on(event, cpuctx, 1))
+                err = -EEXIST;
+        else
+                err = event_sched_in(event, cpuctx, ctx, cpu);
+
+        if (err) {
+                /*
+                 * This event couldn't go on.  If it is in a group
+                 * then we have to pull the whole group off.
+                 * If the event group is pinned then put it in error state.
+                 */
+                if (leader != event)
+                        group_sched_out(leader, cpuctx, ctx);
+                if (leader->attr.pinned) {
+                        update_group_times(leader);
+                        leader->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+        if (!err && !ctx->task && cpuctx->max_pertask)
+                cpuctx->max_pertask--;
+
+ unlock:
+        perf_enable();
+
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Attach a performance event to a context
+ *
+ * First we add the event to the list with the hardware enable bit
+ * in event->hw_config cleared.
+ *
+ * If the event is attached to a task which is on a CPU we use a smp
+ * call to enable it in the task context. The task might have been
+ * scheduled away, but we check this in the smp call again.
+ *
+ * Must be called with ctx->mutex held.
+ */
+static void
+perf_install_in_context(struct perf_event_context *ctx,
+                        struct perf_event *event,
+                        int cpu)
+{
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Per cpu events are installed via an smp call and
+                 * the install is always sucessful.
+                 */
+                smp_call_function_single(cpu, __perf_install_in_context,
+                                         event, 1);
+                return;
+        }
+
+retry:
+        task_oncpu_function_call(task, __perf_install_in_context,
+                                 event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * we need to retry the smp call.
+         */
+        if (ctx->is_active && list_empty(&event->group_entry)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can add the event safely, if it the call above did not
+         * succeed.
+         */
+        if (list_empty(&event->group_entry))
+                add_event_to_ctx(event, ctx);
+        spin_unlock_irq(&ctx->lock);
+}
+
+/*
+ * Put a event into inactive state and update time fields.
+ * Enabling the leader of a group effectively enables all
+ * the group members that aren't explicitly disabled, so we
+ * have to update their ->tstamp_enabled also.
+ * Note: this works for group members as well as group leaders
+ * since the non-leader members' sibling_lists will be empty.
+ */
+static void __perf_event_mark_enabled(struct perf_event *event,
+                                        struct perf_event_context *ctx)
+{
+        struct perf_event *sub;
+
+        event->state = PERF_EVENT_STATE_INACTIVE;
+        event->tstamp_enabled = ctx->time - event->total_time_enabled;
+        list_for_each_entry(sub, &event->sibling_list, group_entry)
+                if (sub->state >= PERF_EVENT_STATE_INACTIVE)
+                        sub->tstamp_enabled =
+                                ctx->time - sub->total_time_enabled;
+}
+
+/*
+ * Cross CPU call to enable a performance event
+ */
+static void __perf_event_enable(void *info)
+{
+        struct perf_event *event = info;
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *leader = event->group_leader;
+        int err;
+
+        /*
+         * If this is a per-task event, need to check whether this
+         * event's task is the current task on this cpu.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx) {
+                if (cpuctx->task_ctx || ctx->task != current)
+                        return;
+                cpuctx->task_ctx = ctx;
+        }
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        update_context_time(ctx);
+
+        if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                goto unlock;
+        __perf_event_mark_enabled(event, ctx);
+
+        /*
+         * If the event is in a group and isn't the group leader,
+         * then don't put it on unless the group is on.
+         */
+        if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
+                goto unlock;
+
+        if (!group_can_go_on(event, cpuctx, 1)) {
+                err = -EEXIST;
+        } else {
+                perf_disable();
+                if (event == leader)
+                        err = group_sched_in(event, cpuctx, ctx,
+                                             smp_processor_id());
+                else
+                        err = event_sched_in(event, cpuctx, ctx,
+                                               smp_processor_id());
+                perf_enable();
+        }
+
+        if (err) {
+                /*
+                 * If this event can't go on and it's part of a
+                 * group, then the whole group has to come off.
+                 */
+                if (leader != event)
+                        group_sched_out(leader, cpuctx, ctx);
+                if (leader->attr.pinned) {
+                        update_group_times(leader);
+                        leader->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+ unlock:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Enable a event.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This condition is satisfied when called through
+ * perf_event_for_each_child or perf_event_for_each as described
+ * for perf_event_disable.
+ */
+static void perf_event_enable(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Enable the event on the cpu that it's on
+                 */
+                smp_call_function_single(event->cpu, __perf_event_enable,
+                                         event, 1);
+                return;
+        }
+
+        spin_lock_irq(&ctx->lock);
+        if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                goto out;
+
+        /*
+         * If the event is in error state, clear that first.
+         * That way, if we see the event in error state below, we
+         * know that it has gone back into error state, as distinct
+         * from the task having been scheduled away before the
+         * cross-call arrived.
+         */
+        if (event->state == PERF_EVENT_STATE_ERROR)
+                event->state = PERF_EVENT_STATE_OFF;
+
+ retry:
+        spin_unlock_irq(&ctx->lock);
+        task_oncpu_function_call(task, __perf_event_enable, event);
+
+        spin_lock_irq(&ctx->lock);
+
+        /*
+         * If the context is active and the event is still off,
+         * we need to retry the cross-call.
+         */
+        if (ctx->is_active && event->state == PERF_EVENT_STATE_OFF)
+                goto retry;
+
+        /*
+         * Since we have the lock this context can't be scheduled
+         * in, so we can change the state safely.
+         */
+        if (event->state == PERF_EVENT_STATE_OFF)
+                __perf_event_mark_enabled(event, ctx);
+
+ out:
+        spin_unlock_irq(&ctx->lock);
+}
+
+static int perf_event_refresh(struct perf_event *event, int refresh)
+{
+        /*
+         * not supported on inherited events
+         */
+        if (event->attr.inherit)
+                return -EINVAL;
+
+        atomic_add(refresh, &event->event_limit);
+        perf_event_enable(event);
+
+        return 0;
+}
+
+void __perf_event_sched_out(struct perf_event_context *ctx,
+                              struct perf_cpu_context *cpuctx)
+{
+        struct perf_event *event;
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 0;
+        if (likely(!ctx->nr_events))
+                goto out;
+        update_context_time(ctx);
+
+        perf_disable();
+        if (ctx->nr_active)
+                list_for_each_entry(event, &ctx->group_list, group_entry)
+                        group_sched_out(event, cpuctx, ctx);
+
+        perf_enable();
+ out:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Test whether two contexts are equivalent, i.e. whether they
+ * have both been cloned from the same version of the same context
+ * and they both have the same number of enabled events.
+ * If the number of enabled events is the same, then the set
+ * of enabled events should be the same, because these are both
+ * inherited contexts, therefore we can't access individual events
+ * in them directly with an fd; we can only enable/disable all
+ * events via prctl, or enable/disable all events in a family
+ * via ioctl, which will have the same effect on both contexts.
+ */
+static int context_equiv(struct perf_event_context *ctx1,
+                         struct perf_event_context *ctx2)
+{
+        return ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx
+                && ctx1->parent_gen == ctx2->parent_gen
+                && !ctx1->pin_count && !ctx2->pin_count;
+}
+
+static void __perf_event_read(void *event);
+
+static void __perf_event_sync_stat(struct perf_event *event,
+                                     struct perf_event *next_event)
+{
+        u64 value;
+
+        if (!event->attr.inherit_stat)
+                return;
+
+        /*
+         * Update the event value, we cannot use perf_event_read()
+         * because we're in the middle of a context switch and have IRQs
+         * disabled, which upsets smp_call_function_single(), however
+         * we know the event must be on the current CPU, therefore we
+         * don't need to use it.
+         */
+        switch (event->state) {
+        case PERF_EVENT_STATE_ACTIVE:
+                __perf_event_read(event);
+                break;
+
+        case PERF_EVENT_STATE_INACTIVE:
+                update_event_times(event);
+                break;
+
+        default:
+                break;
+        }
+
+        /*
+         * In order to keep per-task stats reliable we need to flip the event
+         * values when we flip the contexts.
+         */
+        value = atomic64_read(&next_event->count);
+        value = atomic64_xchg(&event->count, value);
+        atomic64_set(&next_event->count, value);
+
+        swap(event->total_time_enabled, next_event->total_time_enabled);
+        swap(event->total_time_running, next_event->total_time_running);
+
+        /*
+         * Since we swizzled the values, update the user visible data too.
+         */
+        perf_event_update_userpage(event);
+        perf_event_update_userpage(next_event);
+}
+
+#define list_next_entry(pos, member) \
+        list_entry(pos->member.next, typeof(*pos), member)
+
+static void perf_event_sync_stat(struct perf_event_context *ctx,
+                                   struct perf_event_context *next_ctx)
+{
+        struct perf_event *event, *next_event;
+
+        if (!ctx->nr_stat)
+                return;
+
+        event = list_first_entry(&ctx->event_list,
+                                   struct perf_event, event_entry);
+
+        next_event = list_first_entry(&next_ctx->event_list,
+                                        struct perf_event, event_entry);
+
+        while (&event->event_entry != &ctx->event_list &&
+               &next_event->event_entry != &next_ctx->event_list) {
+
+                __perf_event_sync_stat(event, next_event);
+
+                event = list_next_entry(event, event_entry);
+                next_event = list_next_entry(next_event, event_entry);
+        }
+}
+
+/*
+ * Called from scheduler to remove the events of the current task,
+ * with interrupts disabled.
+ *
+ * We stop each event and update the event value in event->count.
+ *
+ * This does not protect us against NMI, but disable()
+ * sets the disabled bit in the control field of event _before_
+ * accessing the event control register. If a NMI hits, then it will
+ * not restart the event.
+ */
+void perf_event_task_sched_out(struct task_struct *task,
+                                 struct task_struct *next, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+        struct perf_event_context *next_ctx;
+        struct perf_event_context *parent;
+        struct pt_regs *regs;
+        int do_switch = 1;
+
+        regs = task_pt_regs(task);
+        perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, regs, 0);
+
+        if (likely(!ctx || !cpuctx->task_ctx))
+                return;
+
+        update_context_time(ctx);
+
+        rcu_read_lock();
+        parent = rcu_dereference(ctx->parent_ctx);
+        next_ctx = next->perf_event_ctxp;
+        if (parent && next_ctx &&
+            rcu_dereference(next_ctx->parent_ctx) == parent) {
+                /*
+                 * Looks like the two contexts are clones, so we might be
+                 * able to optimize the context switch.  We lock both
+                 * contexts and check that they are clones under the
+                 * lock (including re-checking that neither has been
+                 * uncloned in the meantime).  It doesn't matter which
+                 * order we take the locks because no other cpu could
+                 * be trying to lock both of these tasks.
+                 */
+                spin_lock(&ctx->lock);
+                spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
+                if (context_equiv(ctx, next_ctx)) {
+                        /*
+                         * XXX do we need a memory barrier of sorts
+                         * wrt to rcu_dereference() of perf_event_ctxp
+                         */
+                        task->perf_event_ctxp = next_ctx;
+                        next->perf_event_ctxp = ctx;
+                        ctx->task = next;
+                        next_ctx->task = task;
+                        do_switch = 0;
+
+                        perf_event_sync_stat(ctx, next_ctx);
+                }
+                spin_unlock(&next_ctx->lock);
+                spin_unlock(&ctx->lock);
+        }
+        rcu_read_unlock();
+
+        if (do_switch) {
+                __perf_event_sched_out(ctx, cpuctx);
+                cpuctx->task_ctx = NULL;
+        }
+}
+
+/*
+ * Called with IRQs disabled
+ */
+static void __perf_event_task_sched_out(struct perf_event_context *ctx)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+
+        if (!cpuctx->task_ctx)
+                return;
+
+        if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
+                return;
+
+        __perf_event_sched_out(ctx, cpuctx);
+        cpuctx->task_ctx = NULL;
+}
+
+/*
+ * Called with IRQs disabled
+ */
+static void perf_event_cpu_sched_out(struct perf_cpu_context *cpuctx)
+{
+        __perf_event_sched_out(&cpuctx->ctx, cpuctx);
+}
+
+static void
+__perf_event_sched_in(struct perf_event_context *ctx,
+                        struct perf_cpu_context *cpuctx, int cpu)
+{
+        struct perf_event *event;
+        int can_add_hw = 1;
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        if (likely(!ctx->nr_events))
+                goto out;
+
+        ctx->timestamp = perf_clock();
+
+        perf_disable();
+
+        /*
+         * First go through the list and put on any pinned groups
+         * in order to give them the best chance of going on.
+         */
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (event->state <= PERF_EVENT_STATE_OFF ||
+                    !event->attr.pinned)
+                        continue;
+                if (event->cpu != -1 && event->cpu != cpu)
+                        continue;
+
+                if (group_can_go_on(event, cpuctx, 1))
+                        group_sched_in(event, cpuctx, ctx, cpu);
+
+                /*
+                 * If this pinned group hasn't been scheduled,
+                 * put it in error state.
+                 */
+                if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                        update_group_times(event);
+                        event->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                /*
+                 * Ignore events in OFF or ERROR state, and
+                 * ignore pinned events since we did them already.
+                 */
+                if (event->state <= PERF_EVENT_STATE_OFF ||
+                    event->attr.pinned)
+                        continue;
+
+                /*
+                 * Listen to the 'cpu' scheduling filter constraint
+                 * of events:
+                 */
+                if (event->cpu != -1 && event->cpu != cpu)
+                        continue;
+
+                if (group_can_go_on(event, cpuctx, can_add_hw))
+                        if (group_sched_in(event, cpuctx, ctx, cpu))
+                                can_add_hw = 0;
+        }
+        perf_enable();
+ out:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Called from scheduler to add the events of the current task
+ * with interrupts disabled.
+ *
+ * We restore the event value and then enable it.
+ *
+ * This does not protect us against NMI, but enable()
+ * sets the enabled bit in the control field of event _before_
+ * accessing the event control register. If a NMI hits, then it will
+ * keep the event running.
+ */
+void perf_event_task_sched_in(struct task_struct *task, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+
+        if (likely(!ctx))
+                return;
+        if (cpuctx->task_ctx == ctx)
+                return;
+        __perf_event_sched_in(ctx, cpuctx, cpu);
+        cpuctx->task_ctx = ctx;
+}
+
+static void perf_event_cpu_sched_in(struct perf_cpu_context *cpuctx, int cpu)
+{
+        struct perf_event_context *ctx = &cpuctx->ctx;
+
+        __perf_event_sched_in(ctx, cpuctx, cpu);
+}
+
+#define MAX_INTERRUPTS (~0ULL)
+
+static void perf_log_throttle(struct perf_event *event, int enable);
+
+static void perf_adjust_period(struct perf_event *event, u64 events)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 period, sample_period;
+        s64 delta;
+
+        events *= hwc->sample_period;
+        period = div64_u64(events, event->attr.sample_freq);
+
+        delta = (s64)(period - hwc->sample_period);
+        delta = (delta + 7) / 8; /* low pass filter */
+
+        sample_period = hwc->sample_period + delta;
+
+        if (!sample_period)
+                sample_period = 1;
+
+        hwc->sample_period = sample_period;
+}
+
+static void perf_ctx_adjust_freq(struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+        struct hw_perf_event *hwc;
+        u64 interrupts, freq;
+
+        spin_lock(&ctx->lock);
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (event->state != PERF_EVENT_STATE_ACTIVE)
+                        continue;
+
+                hwc = &event->hw;
+
+                interrupts = hwc->interrupts;
+                hwc->interrupts = 0;
+
+                /*
+                 * unthrottle events on the tick
+                 */
+                if (interrupts == MAX_INTERRUPTS) {
+                        perf_log_throttle(event, 1);
+                        event->pmu->unthrottle(event);
+                        interrupts = 2*sysctl_perf_event_sample_rate/HZ;
+                }
+
+                if (!event->attr.freq || !event->attr.sample_freq)
+                        continue;
+
+                /*
+                 * if the specified freq < HZ then we need to skip ticks
+                 */
+                if (event->attr.sample_freq < HZ) {
+                        freq = event->attr.sample_freq;
+
+                        hwc->freq_count += freq;
+                        hwc->freq_interrupts += interrupts;
+
+                        if (hwc->freq_count < HZ)
+                                continue;
+
+                        interrupts = hwc->freq_interrupts;
+                        hwc->freq_interrupts = 0;
+                        hwc->freq_count -= HZ;
+                } else
+                        freq = HZ;
+
+                perf_adjust_period(event, freq * interrupts);
+
+                /*
+                 * In order to avoid being stalled by an (accidental) huge
+                 * sample period, force reset the sample period if we didn't
+                 * get any events in this freq period.
+                 */
+                if (!interrupts) {
+                        perf_disable();
+                        event->pmu->disable(event);
+                        atomic64_set(&hwc->period_left, 0);
+                        event->pmu->enable(event);
+                        perf_enable();
+                }
+        }
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Round-robin a context's events:
+ */
+static void rotate_ctx(struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+
+        if (!ctx->nr_events)
+                return;
+
+        spin_lock(&ctx->lock);
+        /*
+         * Rotate the first entry last (works just fine for group events too):
+         */
+        perf_disable();
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                list_move_tail(&event->group_entry, &ctx->group_list);
+                break;
+        }
+        perf_enable();
+
+        spin_unlock(&ctx->lock);
+}
+
+void perf_event_task_tick(struct task_struct *curr, int cpu)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+
+        if (!atomic_read(&nr_events))
+                return;
+
+        cpuctx = &per_cpu(perf_cpu_context, cpu);
+        ctx = curr->perf_event_ctxp;
+
+        perf_ctx_adjust_freq(&cpuctx->ctx);
+        if (ctx)
+                perf_ctx_adjust_freq(ctx);
+
+        perf_event_cpu_sched_out(cpuctx);
+        if (ctx)
+                __perf_event_task_sched_out(ctx);
+
+        rotate_ctx(&cpuctx->ctx);
+        if (ctx)
+                rotate_ctx(ctx);
+
+        perf_event_cpu_sched_in(cpuctx, cpu);
+        if (ctx)
+                perf_event_task_sched_in(curr, cpu);
+}
+
+/*
+ * Enable all of a task's events that have been marked enable-on-exec.
+ * This expects task == current.
+ */
+static void perf_event_enable_on_exec(struct task_struct *task)
+{
+        struct perf_event_context *ctx;
+        struct perf_event *event;
+        unsigned long flags;
+        int enabled = 0;
+
+        local_irq_save(flags);
+        ctx = task->perf_event_ctxp;
+        if (!ctx || !ctx->nr_events)
+                goto out;
+
+        __perf_event_task_sched_out(ctx);
+
+        spin_lock(&ctx->lock);
+
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (!event->attr.enable_on_exec)
+                        continue;
+                event->attr.enable_on_exec = 0;
+                if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                        continue;
+                __perf_event_mark_enabled(event, ctx);
+                enabled = 1;
+        }
+
+        /*
+         * Unclone this context if we enabled any event.
+         */
+        if (enabled)
+                unclone_ctx(ctx);
+
+        spin_unlock(&ctx->lock);
+
+        perf_event_task_sched_in(task, smp_processor_id());
+ out:
+        local_irq_restore(flags);
+}
+
+/*
+ * Cross CPU call to read the hardware event
+ */
+static void __perf_event_read(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+        unsigned long flags;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu.  If not it has been
+         * scheduled out before the smp call arrived.  In that case
+         * event->count would have been updated to a recent sample
+         * when the event was scheduled out.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        local_irq_save(flags);
+        if (ctx->is_active)
+                update_context_time(ctx);
+        event->pmu->read(event);
+        update_event_times(event);
+        local_irq_restore(flags);
+}
+
+static u64 perf_event_read(struct perf_event *event)
+{
+        /*
+         * If event is enabled and currently active on a CPU, update the
+         * value in the event structure:
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE) {
+                smp_call_function_single(event->oncpu,
+                                         __perf_event_read, event, 1);
+        } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                update_event_times(event);
+        }
+
+        return atomic64_read(&event->count);
+}
+
+/*
+ * Initialize the perf_event context in a task_struct:
+ */
+static void
+__perf_event_init_context(struct perf_event_context *ctx,
+                            struct task_struct *task)
+{
+        memset(ctx, 0, sizeof(*ctx));
+        spin_lock_init(&ctx->lock);
+        mutex_init(&ctx->mutex);
+        INIT_LIST_HEAD(&ctx->group_list);
+        INIT_LIST_HEAD(&ctx->event_list);
+        atomic_set(&ctx->refcount, 1);
+        ctx->task = task;
+}
+
+static struct perf_event_context *find_get_context(pid_t pid, int cpu)
+{
+        struct perf_event_context *ctx;
+        struct perf_cpu_context *cpuctx;
+        struct task_struct *task;
+        unsigned long flags;
+        int err;
+
+        /*
+         * If cpu is not a wildcard then this is a percpu event:
+         */
+        if (cpu != -1) {
+                /* Must be root to operate on a CPU event: */
+                if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+                        return ERR_PTR(-EACCES);
+
+                if (cpu < 0 || cpu > num_possible_cpus())
+                        return ERR_PTR(-EINVAL);
+
+                /*
+                 * We could be clever and allow to attach a event to an
+                 * offline CPU and activate it when the CPU comes up, but
+                 * that's for later.
+                 */
+                if (!cpu_isset(cpu, cpu_online_map))
+                        return ERR_PTR(-ENODEV);
+
+                cpuctx = &per_cpu(perf_cpu_context, cpu);
+                ctx = &cpuctx->ctx;
+                get_ctx(ctx);
+
+                return ctx;
+        }
+
+        rcu_read_lock();
+        if (!pid)
+                task = current;
+        else
+                task = find_task_by_vpid(pid);
+        if (task)
+                get_task_struct(task);
+        rcu_read_unlock();
+
+        if (!task)
+                return ERR_PTR(-ESRCH);
+
+        /*
+         * Can't attach events to a dying task.
+         */
+        err = -ESRCH;
+        if (task->flags & PF_EXITING)
+                goto errout;
+
+        /* Reuse ptrace permission checks for now. */
+        err = -EACCES;
+        if (!ptrace_may_access(task, PTRACE_MODE_READ))
+                goto errout;
+
+ retry:
+        ctx = perf_lock_task_context(task, &flags);
+        if (ctx) {
+                unclone_ctx(ctx);
+                spin_unlock_irqrestore(&ctx->lock, flags);
+        }
+
+        if (!ctx) {
+                ctx = kmalloc(sizeof(struct perf_event_context), GFP_KERNEL);
+                err = -ENOMEM;
+                if (!ctx)
+                        goto errout;
+                __perf_event_init_context(ctx, task);
+                get_ctx(ctx);
+                if (cmpxchg(&task->perf_event_ctxp, NULL, ctx)) {
+                        /*
+                         * We raced with some other task; use
+                         * the context they set.
+                         */
+                        kfree(ctx);
+                        goto retry;
+                }
+                get_task_struct(task);
+        }
+
+        put_task_struct(task);
+        return ctx;
+
+ errout:
+        put_task_struct(task);
+        return ERR_PTR(err);
+}
+
+static void free_event_rcu(struct rcu_head *head)
+{
+        struct perf_event *event;
+
+        event = container_of(head, struct perf_event, rcu_head);
+        if (event->ns)
+                put_pid_ns(event->ns);
+        kfree(event);
+}
+
+static void perf_pending_sync(struct perf_event *event);
+
+static void free_event(struct perf_event *event)
+{
+        perf_pending_sync(event);
+
+        if (!event->parent) {
+                atomic_dec(&nr_events);
+                if (event->attr.mmap)
+                        atomic_dec(&nr_mmap_events);
+                if (event->attr.comm)
+                        atomic_dec(&nr_comm_events);
+                if (event->attr.task)
+                        atomic_dec(&nr_task_events);
+        }
+
+        if (event->output) {
+                fput(event->output->filp);
+                event->output = NULL;
+        }
+
+        if (event->destroy)
+                event->destroy(event);
+
+        put_ctx(event->ctx);
+        call_rcu(&event->rcu_head, free_event_rcu);
+}
+
+/*
+ * Called when the last reference to the file is gone.
+ */
+static int perf_release(struct inode *inode, struct file *file)
+{
+        struct perf_event *event = file->private_data;
+        struct perf_event_context *ctx = event->ctx;
+
+        file->private_data = NULL;
+
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        perf_event_remove_from_context(event);
+        mutex_unlock(&ctx->mutex);
+
+        mutex_lock(&event->owner->perf_event_mutex);
+        list_del_init(&event->owner_entry);
+        mutex_unlock(&event->owner->perf_event_mutex);
+        put_task_struct(event->owner);
+
+        free_event(event);
+
+        return 0;
+}
+
+static int perf_event_read_size(struct perf_event *event)
+{
+        int entry = sizeof(u64); /* value */
+        int size = 0;
+        int nr = 1;
+
+        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+                size += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+                size += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_ID)
+                entry += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_GROUP) {
+                nr += event->group_leader->nr_siblings;
+                size += sizeof(u64);
+        }
+
+        size += entry * nr;
+
+        return size;
+}
+
+static u64 perf_event_read_value(struct perf_event *event)
+{
+        struct perf_event *child;
+        u64 total = 0;
+
+        total += perf_event_read(event);
+        list_for_each_entry(child, &event->child_list, child_list)
+                total += perf_event_read(child);
+
+        return total;
+}
+
+static int perf_event_read_entry(struct perf_event *event,
+                                   u64 read_format, char __user *buf)
+{
+        int n = 0, count = 0;
+        u64 values[2];
+
+        values[n++] = perf_event_read_value(event);
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        count = n * sizeof(u64);
+
+        if (copy_to_user(buf, values, count))
+                return -EFAULT;
+
+        return count;
+}
+
+static int perf_event_read_group(struct perf_event *event,
+                                   u64 read_format, char __user *buf)
+{
+        struct perf_event *leader = event->group_leader, *sub;
+        int n = 0, size = 0, err = -EFAULT;
+        u64 values[3];
+
+        values[n++] = 1 + leader->nr_siblings;
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = leader->total_time_enabled +
+                        atomic64_read(&leader->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = leader->total_time_running +
+                        atomic64_read(&leader->child_total_time_running);
+        }
+
+        size = n * sizeof(u64);
+
+        if (copy_to_user(buf, values, size))
+                return -EFAULT;
+
+        err = perf_event_read_entry(leader, read_format, buf + size);
+        if (err < 0)
+                return err;
+
+        size += err;
+
+        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+                err = perf_event_read_entry(sub, read_format,
+                                buf + size);
+                if (err < 0)
+                        return err;
+
+                size += err;
+        }
+
+        return size;
+}
+
+static int perf_event_read_one(struct perf_event *event,
+                                 u64 read_format, char __user *buf)
+{
+        u64 values[4];
+        int n = 0;
+
+        values[n++] = perf_event_read_value(event);
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+        }
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        if (copy_to_user(buf, values, n * sizeof(u64)))
+                return -EFAULT;
+
+        return n * sizeof(u64);
+}
+
+/*
+ * Read the performance event - simple non blocking version for now
+ */
+static ssize_t
+perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
+{
+        u64 read_format = event->attr.read_format;
+        int ret;
+
+        /*
+         * Return end-of-file for a read on a event that is in
+         * error state (i.e. because it was pinned but it couldn't be
+         * scheduled on to the CPU at some point).
+         */
+        if (event->state == PERF_EVENT_STATE_ERROR)
+                return 0;
+
+        if (count < perf_event_read_size(event))
+                return -ENOSPC;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->child_mutex);
+        if (read_format & PERF_FORMAT_GROUP)
+                ret = perf_event_read_group(event, read_format, buf);
+        else
+                ret = perf_event_read_one(event, read_format, buf);
+        mutex_unlock(&event->child_mutex);
+
+        return ret;
+}
+
+static ssize_t
+perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+        struct perf_event *event = file->private_data;
+
+        return perf_read_hw(event, buf, count);
+}
+
+static unsigned int perf_poll(struct file *file, poll_table *wait)
+{
+        struct perf_event *event = file->private_data;
+        struct perf_mmap_data *data;
+        unsigned int events = POLL_HUP;
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (data)
+                events = atomic_xchg(&data->poll, 0);
+        rcu_read_unlock();
+
+        poll_wait(file, &event->waitq, wait);
+
+        return events;
+}
+
+static void perf_event_reset(struct perf_event *event)
+{
+        (void)perf_event_read(event);
+        atomic64_set(&event->count, 0);
+        perf_event_update_userpage(event);
+}
+
+/*
+ * Holding the top-level event's child_mutex means that any
+ * descendant process that has inherited this event will block
+ * in sync_child_event if it goes to exit, thus satisfying the
+ * task existence requirements of perf_event_enable/disable.
+ */
+static void perf_event_for_each_child(struct perf_event *event,
+                                        void (*func)(struct perf_event *))
+{
+        struct perf_event *child;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->child_mutex);
+        func(event);
+        list_for_each_entry(child, &event->child_list, child_list)
+                func(child);
+        mutex_unlock(&event->child_mutex);
+}
+
+static void perf_event_for_each(struct perf_event *event,
+                                  void (*func)(struct perf_event *))
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *sibling;
+
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        event = event->group_leader;
+
+        perf_event_for_each_child(event, func);
+        func(event);
+        list_for_each_entry(sibling, &event->sibling_list, group_entry)
+                perf_event_for_each_child(event, func);
+        mutex_unlock(&ctx->mutex);
+}
+
+static int perf_event_period(struct perf_event *event, u64 __user *arg)
+{
+        struct perf_event_context *ctx = event->ctx;
+        unsigned long size;
+        int ret = 0;
+        u64 value;
+
+        if (!event->attr.sample_period)
+                return -EINVAL;
+
+        size = copy_from_user(&value, arg, sizeof(value));
+        if (size != sizeof(value))
+                return -EFAULT;
+
+        if (!value)
+                return -EINVAL;
+
+        spin_lock_irq(&ctx->lock);
+        if (event->attr.freq) {
+                if (value > sysctl_perf_event_sample_rate) {
+                        ret = -EINVAL;
+                        goto unlock;
+                }
+
+                event->attr.sample_freq = value;
+        } else {
+                event->attr.sample_period = value;
+                event->hw.sample_period = value;
+        }
+unlock:
+        spin_unlock_irq(&ctx->lock);
+
+        return ret;
+}
+
+int perf_event_set_output(struct perf_event *event, int output_fd);
+
+static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        struct perf_event *event = file->private_data;
+        void (*func)(struct perf_event *);
+        u32 flags = arg;
+
+        switch (cmd) {
+        case PERF_EVENT_IOC_ENABLE:
+                func = perf_event_enable;
+                break;
+        case PERF_EVENT_IOC_DISABLE:
+                func = perf_event_disable;
+                break;
+        case PERF_EVENT_IOC_RESET:
+                func = perf_event_reset;
+                break;
+
+        case PERF_EVENT_IOC_REFRESH:
+                return perf_event_refresh(event, arg);
+
+        case PERF_EVENT_IOC_PERIOD:
+                return perf_event_period(event, (u64 __user *)arg);
+
+        case PERF_EVENT_IOC_SET_OUTPUT:
+                return perf_event_set_output(event, arg);
+
+        default:
+                return -ENOTTY;
+        }
+
+        if (flags & PERF_IOC_FLAG_GROUP)
+                perf_event_for_each(event, func);
+        else
+                perf_event_for_each_child(event, func);
+
+        return 0;
+}
+
+int perf_event_task_enable(void)
+{
+        struct perf_event *event;
+
+        mutex_lock(&current->perf_event_mutex);
+        list_for_each_entry(event, &current->perf_event_list, owner_entry)
+                perf_event_for_each_child(event, perf_event_enable);
+        mutex_unlock(&current->perf_event_mutex);
+
+        return 0;
+}
+
+int perf_event_task_disable(void)
+{
+        struct perf_event *event;
+
+        mutex_lock(&current->perf_event_mutex);
+        list_for_each_entry(event, &current->perf_event_list, owner_entry)
+                perf_event_for_each_child(event, perf_event_disable);
+        mutex_unlock(&current->perf_event_mutex);
+
+        return 0;
+}
+
+#ifndef PERF_EVENT_INDEX_OFFSET
+# define PERF_EVENT_INDEX_OFFSET 0
+#endif
+
+static int perf_event_index(struct perf_event *event)
+{
+        if (event->state != PERF_EVENT_STATE_ACTIVE)
+                return 0;
+
+        return event->hw.idx + 1 - PERF_EVENT_INDEX_OFFSET;
+}
+
+/*
+ * Callers need to ensure there can be no nesting of this function, otherwise
+ * the seqlock logic goes bad. We can not serialize this because the arch
+ * code calls this from NMI context.
+ */
+void perf_event_update_userpage(struct perf_event *event)
+{
+        struct perf_event_mmap_page *userpg;
+        struct perf_mmap_data *data;
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto unlock;
+
+        userpg = data->user_page;
+
+        /*
+         * Disable preemption so as to not let the corresponding user-space
+         * spin too long if we get preempted.
+         */
+        preempt_disable();
+        ++userpg->lock;
+        barrier();
+        userpg->index = perf_event_index(event);
+        userpg->offset = atomic64_read(&event->count);
+        if (event->state == PERF_EVENT_STATE_ACTIVE)
+                userpg->offset -= atomic64_read(&event->hw.prev_count);
+
+        userpg->time_enabled = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+
+        userpg->time_running = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+
+        barrier();
+        ++userpg->lock;
+        preempt_enable();
+unlock:
+        rcu_read_unlock();
+}
+
+static unsigned long perf_data_size(struct perf_mmap_data *data)
+{
+        return data->nr_pages << (PAGE_SHIFT + data->data_order);
+}
+
+#ifndef CONFIG_PERF_USE_VMALLOC
+
+/*
+ * Back perf_mmap() with regular GFP_KERNEL-0 pages.
+ */
+
+static struct page *
+perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
+{
+        if (pgoff > data->nr_pages)
+                return NULL;
+
+        if (pgoff == 0)
+                return virt_to_page(data->user_page);
+
+        return virt_to_page(data->data_pages[pgoff - 1]);
+}
+
+static struct perf_mmap_data *
+perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
+{
+        struct perf_mmap_data *data;
+        unsigned long size;
+        int i;
+
+        WARN_ON(atomic_read(&event->mmap_count));
+
+        size = sizeof(struct perf_mmap_data);
+        size += nr_pages * sizeof(void *);
+
+        data = kzalloc(size, GFP_KERNEL);
+        if (!data)
+                goto fail;
+
+        data->user_page = (void *)get_zeroed_page(GFP_KERNEL);
+        if (!data->user_page)
+                goto fail_user_page;
+
+        for (i = 0; i < nr_pages; i++) {
+                data->data_pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
+                if (!data->data_pages[i])
+                        goto fail_data_pages;
+        }
+
+        data->data_order = 0;
+        data->nr_pages = nr_pages;
+
+        return data;
+
+fail_data_pages:
+        for (i--; i >= 0; i--)
+                free_page((unsigned long)data->data_pages[i]);
+
+        free_page((unsigned long)data->user_page);
+
+fail_user_page:
+        kfree(data);
+
+fail:
+        return NULL;
+}
+
+static void perf_mmap_free_page(unsigned long addr)
+{
+        struct page *page = virt_to_page((void *)addr);
+
+        page->mapping = NULL;
+        __free_page(page);
+}
+
+static void perf_mmap_data_free(struct perf_mmap_data *data)
+{
+        int i;
+
+        perf_mmap_free_page((unsigned long)data->user_page);
+        for (i = 0; i < data->nr_pages; i++)
+                perf_mmap_free_page((unsigned long)data->data_pages[i]);
+}
+
+#else
+
+/*
+ * Back perf_mmap() with vmalloc memory.
+ *
+ * Required for architectures that have d-cache aliasing issues.
+ */
+
+static struct page *
+perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
+{
+        if (pgoff > (1UL << data->data_order))
+                return NULL;
+
+        return vmalloc_to_page((void *)data->user_page + pgoff * PAGE_SIZE);
+}
+
+static void perf_mmap_unmark_page(void *addr)
+{
+        struct page *page = vmalloc_to_page(addr);
+
+        page->mapping = NULL;
+}
+
+static void perf_mmap_data_free_work(struct work_struct *work)
+{
+        struct perf_mmap_data *data;
+        void *base;
+        int i, nr;
+
+        data = container_of(work, struct perf_mmap_data, work);
+        nr = 1 << data->data_order;
+
+        base = data->user_page;
+        for (i = 0; i < nr + 1; i++)
+                perf_mmap_unmark_page(base + (i * PAGE_SIZE));
+
+        vfree(base);
+}
+
+static void perf_mmap_data_free(struct perf_mmap_data *data)
+{
+        schedule_work(&data->work);
+}
+
+static struct perf_mmap_data *
+perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
+{
+        struct perf_mmap_data *data;
+        unsigned long size;
+        void *all_buf;
+
+        WARN_ON(atomic_read(&event->mmap_count));
+
+        size = sizeof(struct perf_mmap_data);
+        size += sizeof(void *);
+
+        data = kzalloc(size, GFP_KERNEL);
+        if (!data)
+                goto fail;
+
+        INIT_WORK(&data->work, perf_mmap_data_free_work);
+
+        all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
+        if (!all_buf)
+                goto fail_all_buf;
+
+        data->user_page = all_buf;
+        data->data_pages[0] = all_buf + PAGE_SIZE;
+        data->data_order = ilog2(nr_pages);
+        data->nr_pages = 1;
+
+        return data;
+
+fail_all_buf:
+        kfree(data);
+
+fail:
+        return NULL;
+}
+
+#endif
+
+static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+        struct perf_mmap_data *data;
+        int ret = VM_FAULT_SIGBUS;
+
+        if (vmf->flags & FAULT_FLAG_MKWRITE) {
+                if (vmf->pgoff == 0)
+                        ret = 0;
+                return ret;
+        }
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto unlock;
+
+        if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
+                goto unlock;
+
+        vmf->page = perf_mmap_to_page(data, vmf->pgoff);
+        if (!vmf->page)
+                goto unlock;
+
+        get_page(vmf->page);
+        vmf->page->mapping = vma->vm_file->f_mapping;
+        vmf->page->index   = vmf->pgoff;
+
+        ret = 0;
+unlock:
+        rcu_read_unlock();
+
+        return ret;
+}
+
+static void
+perf_mmap_data_init(struct perf_event *event, struct perf_mmap_data *data)
+{
+        long max_size = perf_data_size(data);
+
+        atomic_set(&data->lock, -1);
+
+        if (event->attr.watermark) {
+                data->watermark = min_t(long, max_size,
+                                        event->attr.wakeup_watermark);
+        }
+
+        if (!data->watermark)
+                data->watermark = max_t(long, PAGE_SIZE, max_size / 2);
+
+
+        rcu_assign_pointer(event->data, data);
+}
+
+static void perf_mmap_data_free_rcu(struct rcu_head *rcu_head)
+{
+        struct perf_mmap_data *data;
+
+        data = container_of(rcu_head, struct perf_mmap_data, rcu_head);
+        perf_mmap_data_free(data);
+        kfree(data);
+}
+
+static void perf_mmap_data_release(struct perf_event *event)
+{
+        struct perf_mmap_data *data = event->data;
+
+        WARN_ON(atomic_read(&event->mmap_count));
+
+        rcu_assign_pointer(event->data, NULL);
+        call_rcu(&data->rcu_head, perf_mmap_data_free_rcu);
+}
+
+static void perf_mmap_open(struct vm_area_struct *vma)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+
+        atomic_inc(&event->mmap_count);
+}
+
+static void perf_mmap_close(struct vm_area_struct *vma)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
+                unsigned long size = perf_data_size(event->data);
+                struct user_struct *user = current_user();
+
+                atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
+                vma->vm_mm->locked_vm -= event->data->nr_locked;
+                perf_mmap_data_release(event);
+                mutex_unlock(&event->mmap_mutex);
+        }
+}
+
+static const struct vm_operations_struct perf_mmap_vmops = {
+        .open           = perf_mmap_open,
+        .close          = perf_mmap_close,
+        .fault          = perf_mmap_fault,
+        .page_mkwrite   = perf_mmap_fault,
+};
+
+static int perf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+        struct perf_event *event = file->private_data;
+        unsigned long user_locked, user_lock_limit;
+        struct user_struct *user = current_user();
+        unsigned long locked, lock_limit;
+        struct perf_mmap_data *data;
+        unsigned long vma_size;
+        unsigned long nr_pages;
+        long user_extra, extra;
+        int ret = 0;
+
+        if (!(vma->vm_flags & VM_SHARED))
+                return -EINVAL;
+
+        vma_size = vma->vm_end - vma->vm_start;
+        nr_pages = (vma_size / PAGE_SIZE) - 1;
+
+        /*
+         * If we have data pages ensure they're a power-of-two number, so we
+         * can do bitmasks instead of modulo.
+         */
+        if (nr_pages != 0 && !is_power_of_2(nr_pages))
+                return -EINVAL;
+
+        if (vma_size != PAGE_SIZE * (1 + nr_pages))
+                return -EINVAL;
+
+        if (vma->vm_pgoff != 0)
+                return -EINVAL;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->mmap_mutex);
+        if (event->output) {
+                ret = -EINVAL;
+                goto unlock;
+        }
+
+        if (atomic_inc_not_zero(&event->mmap_count)) {
+                if (nr_pages != event->data->nr_pages)
+                        ret = -EINVAL;
+                goto unlock;
+        }
+
+        user_extra = nr_pages + 1;
+        user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
+
+        /*
+         * Increase the limit linearly with more CPUs:
+         */
+        user_lock_limit *= num_online_cpus();
+
+        user_locked = atomic_long_read(&user->locked_vm) + user_extra;
+
+        extra = 0;
+        if (user_locked > user_lock_limit)
+                extra = user_locked - user_lock_limit;
+
+        lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+        lock_limit >>= PAGE_SHIFT;
+        locked = vma->vm_mm->locked_vm + extra;
+
+        if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
+                !capable(CAP_IPC_LOCK)) {
+                ret = -EPERM;
+                goto unlock;
+        }
+
+        WARN_ON(event->data);
+
+        data = perf_mmap_data_alloc(event, nr_pages);
+        ret = -ENOMEM;
+        if (!data)
+                goto unlock;
+
+        ret = 0;
+        perf_mmap_data_init(event, data);
+
+        atomic_set(&event->mmap_count, 1);
+        atomic_long_add(user_extra, &user->locked_vm);
+        vma->vm_mm->locked_vm += extra;
+        event->data->nr_locked = extra;
+        if (vma->vm_flags & VM_WRITE)
+                event->data->writable = 1;
+
+unlock:
+        mutex_unlock(&event->mmap_mutex);
+
+        vma->vm_flags |= VM_RESERVED;
+        vma->vm_ops = &perf_mmap_vmops;
+
+        return ret;
+}
+
+static int perf_fasync(int fd, struct file *filp, int on)
+{
+        struct inode *inode = filp->f_path.dentry->d_inode;
+        struct perf_event *event = filp->private_data;
+        int retval;
+
+        mutex_lock(&inode->i_mutex);
+        retval = fasync_helper(fd, filp, on, &event->fasync);
+        mutex_unlock(&inode->i_mutex);
+
+        if (retval < 0)
+                return retval;
+
+        return 0;
+}
+
+static const struct file_operations perf_fops = {
+        .release                = perf_release,
+        .read                   = perf_read,
+        .poll                   = perf_poll,
+        .unlocked_ioctl         = perf_ioctl,
+        .compat_ioctl           = perf_ioctl,
+        .mmap                   = perf_mmap,
+        .fasync                 = perf_fasync,
+};
+
+/*
+ * Perf event wakeup
+ *
+ * If there's data, ensure we set the poll() state and publish everything
+ * to user-space before waking everybody up.
+ */
+
+void perf_event_wakeup(struct perf_event *event)
+{
+        wake_up_all(&event->waitq);
+
+        if (event->pending_kill) {
+                kill_fasync(&event->fasync, SIGIO, event->pending_kill);
+                event->pending_kill = 0;
+        }
+}
+
+/*
+ * Pending wakeups
+ *
+ * Handle the case where we need to wakeup up from NMI (or rq->lock) context.
+ *
+ * The NMI bit means we cannot possibly take locks. Therefore, maintain a
+ * single linked list and use cmpxchg() to add entries lockless.
+ */
+
+static void perf_pending_event(struct perf_pending_entry *entry)
+{
+        struct perf_event *event = container_of(entry,
+                        struct perf_event, pending);
+
+        if (event->pending_disable) {
+                event->pending_disable = 0;
+                __perf_event_disable(event);
+        }
+
+        if (event->pending_wakeup) {
+                event->pending_wakeup = 0;
+                perf_event_wakeup(event);
+        }
+}
+
+#define PENDING_TAIL ((struct perf_pending_entry *)-1UL)
+
+static DEFINE_PER_CPU(struct perf_pending_entry *, perf_pending_head) = {
+        PENDING_TAIL,
+};
+
+static void perf_pending_queue(struct perf_pending_entry *entry,
+                               void (*func)(struct perf_pending_entry *))
+{
+        struct perf_pending_entry **head;
+
+        if (cmpxchg(&entry->next, NULL, PENDING_TAIL) != NULL)
+                return;
+
+        entry->func = func;
+
+        head = &get_cpu_var(perf_pending_head);
+
+        do {
+                entry->next = *head;
+        } while (cmpxchg(head, entry->next, entry) != entry->next);
+
+        set_perf_event_pending();
+
+        put_cpu_var(perf_pending_head);
+}
+
+static int __perf_pending_run(void)
+{
+        struct perf_pending_entry *list;
+        int nr = 0;
+
+        list = xchg(&__get_cpu_var(perf_pending_head), PENDING_TAIL);
+        while (list != PENDING_TAIL) {
+                void (*func)(struct perf_pending_entry *);
+                struct perf_pending_entry *entry = list;
+
+                list = list->next;
+
+                func = entry->func;
+                entry->next = NULL;
+                /*
+                 * Ensure we observe the unqueue before we issue the wakeup,
+                 * so that we won't be waiting forever.
+                 * -- see perf_not_pending().
+                 */
+                smp_wmb();
+
+                func(entry);
+                nr++;
+        }
+
+        return nr;
+}
+
+static inline int perf_not_pending(struct perf_event *event)
+{
+        /*
+         * If we flush on whatever cpu we run, there is a chance we don't
+         * need to wait.
+         */
+        get_cpu();
+        __perf_pending_run();
+        put_cpu();
+
+        /*
+         * Ensure we see the proper queue state before going to sleep
+         * so that we do not miss the wakeup. -- see perf_pending_handle()
+         */
+        smp_rmb();
+        return event->pending.next == NULL;
+}
+
+static void perf_pending_sync(struct perf_event *event)
+{
+        wait_event(event->waitq, perf_not_pending(event));
+}
+
+void perf_event_do_pending(void)
+{
+        __perf_pending_run();
+}
+
+/*
+ * Callchain support -- arch specific
+ */
+
+__weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+{
+        return NULL;
+}
+
+/*
+ * Output
+ */
+static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail,
+                              unsigned long offset, unsigned long head)
+{
+        unsigned long mask;
+
+        if (!data->writable)
+                return true;
+
+        mask = perf_data_size(data) - 1;
+
+        offset = (offset - tail) & mask;
+        head   = (head   - tail) & mask;
+
+        if ((int)(head - offset) < 0)
+                return false;
+
+        return true;
+}
+
+static void perf_output_wakeup(struct perf_output_handle *handle)
+{
+        atomic_set(&handle->data->poll, POLL_IN);
+
+        if (handle->nmi) {
+                handle->event->pending_wakeup = 1;
+                perf_pending_queue(&handle->event->pending,
+                                   perf_pending_event);
+        } else
+                perf_event_wakeup(handle->event);
+}
+
+/*
+ * Curious locking construct.
+ *
+ * We need to ensure a later event_id doesn't publish a head when a former
+ * event_id isn't done writing. However since we need to deal with NMIs we
+ * cannot fully serialize things.
+ *
+ * What we do is serialize between CPUs so we only have to deal with NMI
+ * nesting on a single CPU.
+ *
+ * We only publish the head (and generate a wakeup) when the outer-most
+ * event_id completes.
+ */
+static void perf_output_lock(struct perf_output_handle *handle)
+{
+        struct perf_mmap_data *data = handle->data;
+        int cpu;
+
+        handle->locked = 0;
+
+        local_irq_save(handle->flags);
+        cpu = smp_processor_id();
+
+        if (in_nmi() && atomic_read(&data->lock) == cpu)
+                return;
+
+        while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
+                cpu_relax();
+
+        handle->locked = 1;
+}
+
+static void perf_output_unlock(struct perf_output_handle *handle)
+{
+        struct perf_mmap_data *data = handle->data;
+        unsigned long head;
+        int cpu;
+
+        data->done_head = data->head;
+
+        if (!handle->locked)
+                goto out;
+
+again:
+        /*
+         * The xchg implies a full barrier that ensures all writes are done
+         * before we publish the new head, matched by a rmb() in userspace when
+         * reading this position.
+         */
+        while ((head = atomic_long_xchg(&data->done_head, 0)))
+                data->user_page->data_head = head;
+
+        /*
+         * NMI can happen here, which means we can miss a done_head update.
+         */
+
+        cpu = atomic_xchg(&data->lock, -1);
+        WARN_ON_ONCE(cpu != smp_processor_id());
+
+        /*
+         * Therefore we have to validate we did not indeed do so.
+         */
+        if (unlikely(atomic_long_read(&data->done_head))) {
+                /*
+                 * Since we had it locked, we can lock it again.
+                 */
+                while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
+                        cpu_relax();
+
+                goto again;
+        }
+
+        if (atomic_xchg(&data->wakeup, 0))
+                perf_output_wakeup(handle);
+out:
+        local_irq_restore(handle->flags);
+}
+
+void perf_output_copy(struct perf_output_handle *handle,
+                      const void *buf, unsigned int len)
+{
+        unsigned int pages_mask;
+        unsigned long offset;
+        unsigned int size;
+        void **pages;
+
+        offset          = handle->offset;
+        pages_mask      = handle->data->nr_pages - 1;
+        pages           = handle->data->data_pages;
+
+        do {
+                unsigned long page_offset;
+                unsigned long page_size;
+                int nr;
+
+                nr          = (offset >> PAGE_SHIFT) & pages_mask;
+                page_size   = 1UL << (handle->data->data_order + PAGE_SHIFT);
+                page_offset = offset & (page_size - 1);
+                size        = min_t(unsigned int, page_size - page_offset, len);
+
+                memcpy(pages[nr] + page_offset, buf, size);
+
+                len         -= size;
+                buf         += size;
+                offset      += size;
+        } while (len);
+
+        handle->offset = offset;
+
+        /*
+         * Check we didn't copy past our reservation window, taking the
+         * possible unsigned int wrap into account.
+         */
+        WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0);
+}
+
+int perf_output_begin(struct perf_output_handle *handle,
+                      struct perf_event *event, unsigned int size,
+                      int nmi, int sample)
+{
+        struct perf_event *output_event;
+        struct perf_mmap_data *data;
+        unsigned long tail, offset, head;
+        int have_lost;
+        struct {
+                struct perf_event_header header;
+                u64                      id;
+                u64                      lost;
+        } lost_event;
+
+        rcu_read_lock();
+        /*
+         * For inherited events we send all the output towards the parent.
+         */
+        if (event->parent)
+                event = event->parent;
+
+        output_event = rcu_dereference(event->output);
+        if (output_event)
+                event = output_event;
+
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto out;
+
+        handle->data    = data;
+        handle->event   = event;
+        handle->nmi     = nmi;
+        handle->sample  = sample;
+
+        if (!data->nr_pages)
+                goto fail;
+
+        have_lost = atomic_read(&data->lost);
+        if (have_lost)
+                size += sizeof(lost_event);
+
+        perf_output_lock(handle);
+
+        do {
+                /*
+                 * Userspace could choose to issue a mb() before updating the
+                 * tail pointer. So that all reads will be completed before the
+                 * write is issued.
+                 */
+                tail = ACCESS_ONCE(data->user_page->data_tail);
+                smp_rmb();
+                offset = head = atomic_long_read(&data->head);
+                head += size;
+                if (unlikely(!perf_output_space(data, tail, offset, head)))
+                        goto fail;
+        } while (atomic_long_cmpxchg(&data->head, offset, head) != offset);
+
+        handle->offset  = offset;
+        handle->head    = head;
+
+        if (head - tail > data->watermark)
+                atomic_set(&data->wakeup, 1);
+
+        if (have_lost) {
+                lost_event.header.type = PERF_RECORD_LOST;
+                lost_event.header.misc = 0;
+                lost_event.header.size = sizeof(lost_event);
+                lost_event.id          = event->id;
+                lost_event.lost        = atomic_xchg(&data->lost, 0);
+
+                perf_output_put(handle, lost_event);
+        }
+
+        return 0;
+
+fail:
+        atomic_inc(&data->lost);
+        perf_output_unlock(handle);
+out:
+        rcu_read_unlock();
+
+        return -ENOSPC;
+}
+
+void perf_output_end(struct perf_output_handle *handle)
+{
+        struct perf_event *event = handle->event;
+        struct perf_mmap_data *data = handle->data;
+
+        int wakeup_events = event->attr.wakeup_events;
+
+        if (handle->sample && wakeup_events) {
+                int events = atomic_inc_return(&data->events);
+                if (events >= wakeup_events) {
+                        atomic_sub(wakeup_events, &data->events);
+                        atomic_set(&data->wakeup, 1);
+                }
+        }
+
+        perf_output_unlock(handle);
+        rcu_read_unlock();
+}
+
+static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
+{
+        /*
+         * only top level events have the pid namespace they were created in
+         */
+        if (event->parent)
+                event = event->parent;
+
+        return task_tgid_nr_ns(p, event->ns);
+}
+
+static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
+{
+        /*
+         * only top level events have the pid namespace they were created in
+         */
+        if (event->parent)
+                event = event->parent;
+
+        return task_pid_nr_ns(p, event->ns);
+}
+
+static void perf_output_read_one(struct perf_output_handle *handle,
+                                 struct perf_event *event)
+{
+        u64 read_format = event->attr.read_format;
+        u64 values[4];
+        int n = 0;
+
+        values[n++] = atomic64_read(&event->count);
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+        }
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        perf_output_copy(handle, values, n * sizeof(u64));
+}
+
+/*
+ * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
+ */
+static void perf_output_read_group(struct perf_output_handle *handle,
+                            struct perf_event *event)
+{
+        struct perf_event *leader = event->group_leader, *sub;
+        u64 read_format = event->attr.read_format;
+        u64 values[5];
+        int n = 0;
+
+        values[n++] = 1 + leader->nr_siblings;
+
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+                values[n++] = leader->total_time_enabled;
+
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+                values[n++] = leader->total_time_running;
+
+        if (leader != event)
+                leader->pmu->read(leader);
+
+        values[n++] = atomic64_read(&leader->count);
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(leader);
+
+        perf_output_copy(handle, values, n * sizeof(u64));
+
+        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+                n = 0;
+
+                if (sub != event)
+                        sub->pmu->read(sub);
+
+                values[n++] = atomic64_read(&sub->count);
+                if (read_format & PERF_FORMAT_ID)
+                        values[n++] = primary_event_id(sub);
+
+                perf_output_copy(handle, values, n * sizeof(u64));
+        }
+}
+
+static void perf_output_read(struct perf_output_handle *handle,
+                             struct perf_event *event)
+{
+        if (event->attr.read_format & PERF_FORMAT_GROUP)
+                perf_output_read_group(handle, event);
+        else
+                perf_output_read_one(handle, event);
+}
+
+void perf_output_sample(struct perf_output_handle *handle,
+                        struct perf_event_header *header,
+                        struct perf_sample_data *data,
+                        struct perf_event *event)
+{
+        u64 sample_type = data->type;
+
+        perf_output_put(handle, *header);
+
+        if (sample_type & PERF_SAMPLE_IP)
+                perf_output_put(handle, data->ip);
+
+        if (sample_type & PERF_SAMPLE_TID)
+                perf_output_put(handle, data->tid_entry);
+
+        if (sample_type & PERF_SAMPLE_TIME)
+                perf_output_put(handle, data->time);
+
+        if (sample_type & PERF_SAMPLE_ADDR)
+                perf_output_put(handle, data->addr);
+
+        if (sample_type & PERF_SAMPLE_ID)
+                perf_output_put(handle, data->id);
+
+        if (sample_type & PERF_SAMPLE_STREAM_ID)
+                perf_output_put(handle, data->stream_id);
+
+        if (sample_type & PERF_SAMPLE_CPU)
+                perf_output_put(handle, data->cpu_entry);
+
+        if (sample_type & PERF_SAMPLE_PERIOD)
+                perf_output_put(handle, data->period);
+
+        if (sample_type & PERF_SAMPLE_READ)
+                perf_output_read(handle, event);
+
+        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
+                if (data->callchain) {
+                        int size = 1;
+
+                        if (data->callchain)
+                                size += data->callchain->nr;
+
+                        size *= sizeof(u64);
+
+                        perf_output_copy(handle, data->callchain, size);
+                } else {
+                        u64 nr = 0;
+                        perf_output_put(handle, nr);
+                }
+        }
+
+        if (sample_type & PERF_SAMPLE_RAW) {
+                if (data->raw) {
+                        perf_output_put(handle, data->raw->size);
+                        perf_output_copy(handle, data->raw->data,
+                                         data->raw->size);
+                } else {
+                        struct {
+                                u32     size;
+                                u32     data;
+                        } raw = {
+                                .size = sizeof(u32),
+                                .data = 0,
+                        };
+                        perf_output_put(handle, raw);
+                }
+        }
+}
+
+void perf_prepare_sample(struct perf_event_header *header,
+                         struct perf_sample_data *data,
+                         struct perf_event *event,
+                         struct pt_regs *regs)
+{
+        u64 sample_type = event->attr.sample_type;
+
+        data->type = sample_type;
+
+        header->type = PERF_RECORD_SAMPLE;
+        header->size = sizeof(*header);
+
+        header->misc = 0;
+        header->misc |= perf_misc_flags(regs);
+
+        if (sample_type & PERF_SAMPLE_IP) {
+                data->ip = perf_instruction_pointer(regs);
+
+                header->size += sizeof(data->ip);
+        }
+
+        if (sample_type & PERF_SAMPLE_TID) {
+                /* namespace issues */
+                data->tid_entry.pid = perf_event_pid(event, current);
+                data->tid_entry.tid = perf_event_tid(event, current);
+
+                header->size += sizeof(data->tid_entry);
+        }
+
+        if (sample_type & PERF_SAMPLE_TIME) {
+                data->time = perf_clock();
+
+                header->size += sizeof(data->time);
+        }
+
+        if (sample_type & PERF_SAMPLE_ADDR)
+                header->size += sizeof(data->addr);
+
+        if (sample_type & PERF_SAMPLE_ID) {
+                data->id = primary_event_id(event);
+
+                header->size += sizeof(data->id);
+        }
+
+        if (sample_type & PERF_SAMPLE_STREAM_ID) {
+                data->stream_id = event->id;
+
+                header->size += sizeof(data->stream_id);
+        }
+
+        if (sample_type & PERF_SAMPLE_CPU) {
+                data->cpu_entry.cpu             = raw_smp_processor_id();
+                data->cpu_entry.reserved        = 0;
+
+                header->size += sizeof(data->cpu_entry);
+        }
+
+        if (sample_type & PERF_SAMPLE_PERIOD)
+                header->size += sizeof(data->period);
+
+        if (sample_type & PERF_SAMPLE_READ)
+                header->size += perf_event_read_size(event);
+
+        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
+                int size = 1;
+
+                data->callchain = perf_callchain(regs);
+
+                if (data->callchain)
+                        size += data->callchain->nr;
+
+                header->size += size * sizeof(u64);
+        }
+
+        if (sample_type & PERF_SAMPLE_RAW) {
+                int size = sizeof(u32);
+
+                if (data->raw)
+                        size += data->raw->size;
+                else
+                        size += sizeof(u32);
+
+                WARN_ON_ONCE(size & (sizeof(u64)-1));
+                header->size += size;
+        }
+}
+
+static void perf_event_output(struct perf_event *event, int nmi,
+                                struct perf_sample_data *data,
+                                struct pt_regs *regs)
+{
+        struct perf_output_handle handle;
+        struct perf_event_header header;
+
+        perf_prepare_sample(&header, data, event, regs);
+
+        if (perf_output_begin(&handle, event, header.size, nmi, 1))
+                return;
+
+        perf_output_sample(&handle, &header, data, event);
+
+        perf_output_end(&handle);
+}
+
+/*
+ * read event_id
+ */
+
+struct perf_read_event {
+        struct perf_event_header        header;
+
+        u32                             pid;
+        u32                             tid;
+};
+
+static void
+perf_event_read_event(struct perf_event *event,
+                        struct task_struct *task)
+{
+        struct perf_output_handle handle;
+        struct perf_read_event read_event = {
+                .header = {
+                        .type = PERF_RECORD_READ,
+                        .misc = 0,
+                        .size = sizeof(read_event) + perf_event_read_size(event),
+                },
+                .pid = perf_event_pid(event, task),
+                .tid = perf_event_tid(event, task),
+        };
+        int ret;
+
+        ret = perf_output_begin(&handle, event, read_event.header.size, 0, 0);
+        if (ret)
+                return;
+
+        perf_output_put(&handle, read_event);
+        perf_output_read(&handle, event);
+
+        perf_output_end(&handle);
+}
+
+/*
+ * task tracking -- fork/exit
+ *
+ * enabled by: attr.comm | attr.mmap | attr.task
+ */
+
+struct perf_task_event {
+        struct task_struct              *task;
+        struct perf_event_context       *task_ctx;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             ppid;
+                u32                             tid;
+                u32                             ptid;
+                u64                             time;
+        } event_id;
+};
+
+static void perf_event_task_output(struct perf_event *event,
+                                     struct perf_task_event *task_event)
+{
+        struct perf_output_handle handle;
+        int size;
+        struct task_struct *task = task_event->task;
+        int ret;
+
+        size  = task_event->event_id.header.size;
+        ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        task_event->event_id.pid = perf_event_pid(event, task);
+        task_event->event_id.ppid = perf_event_pid(event, current);
+
+        task_event->event_id.tid = perf_event_tid(event, task);
+        task_event->event_id.ptid = perf_event_tid(event, current);
+
+        task_event->event_id.time = perf_clock();
+
+        perf_output_put(&handle, task_event->event_id);
+
+        perf_output_end(&handle);
+}
+
+static int perf_event_task_match(struct perf_event *event)
+{
+        if (event->attr.comm || event->attr.mmap || event->attr.task)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_task_ctx(struct perf_event_context *ctx,
+                                  struct perf_task_event *task_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_task_match(event))
+                        perf_event_task_output(event, task_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_task_event(struct perf_task_event *task_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx = task_event->task_ctx;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_task_ctx(&cpuctx->ctx, task_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        if (!ctx)
+                ctx = rcu_dereference(task_event->task->perf_event_ctxp);
+        if (ctx)
+                perf_event_task_ctx(ctx, task_event);
+        rcu_read_unlock();
+}
+
+static void perf_event_task(struct task_struct *task,
+                              struct perf_event_context *task_ctx,
+                              int new)
+{
+        struct perf_task_event task_event;
+
+        if (!atomic_read(&nr_comm_events) &&
+            !atomic_read(&nr_mmap_events) &&
+            !atomic_read(&nr_task_events))
+                return;
+
+        task_event = (struct perf_task_event){
+                .task     = task,
+                .task_ctx = task_ctx,
+                .event_id    = {
+                        .header = {
+                                .type = new ? PERF_RECORD_FORK : PERF_RECORD_EXIT,
+                                .misc = 0,
+                                .size = sizeof(task_event.event_id),
+                        },
+                        /* .pid  */
+                        /* .ppid */
+                        /* .tid  */
+                        /* .ptid */
+                },
+        };
+
+        perf_event_task_event(&task_event);
+}
+
+void perf_event_fork(struct task_struct *task)
+{
+        perf_event_task(task, NULL, 1);
+}
+
+/*
+ * comm tracking
+ */
+
+struct perf_comm_event {
+        struct task_struct      *task;
+        char                    *comm;
+        int                     comm_size;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             tid;
+        } event_id;
+};
+
+static void perf_event_comm_output(struct perf_event *event,
+                                     struct perf_comm_event *comm_event)
+{
+        struct perf_output_handle handle;
+        int size = comm_event->event_id.header.size;
+        int ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        comm_event->event_id.pid = perf_event_pid(event, comm_event->task);
+        comm_event->event_id.tid = perf_event_tid(event, comm_event->task);
+
+        perf_output_put(&handle, comm_event->event_id);
+        perf_output_copy(&handle, comm_event->comm,
+                                   comm_event->comm_size);
+        perf_output_end(&handle);
+}
+
+static int perf_event_comm_match(struct perf_event *event)
+{
+        if (event->attr.comm)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_comm_ctx(struct perf_event_context *ctx,
+                                  struct perf_comm_event *comm_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_comm_match(event))
+                        perf_event_comm_output(event, comm_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_comm_event(struct perf_comm_event *comm_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+        unsigned int size;
+        char comm[TASK_COMM_LEN];
+
+        memset(comm, 0, sizeof(comm));
+        strncpy(comm, comm_event->task->comm, sizeof(comm));
+        size = ALIGN(strlen(comm)+1, sizeof(u64));
+
+        comm_event->comm = comm;
+        comm_event->comm_size = size;
+
+        comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_comm_ctx(&cpuctx->ctx, comm_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_event_comm_ctx(ctx, comm_event);
+        rcu_read_unlock();
+}
+
+void perf_event_comm(struct task_struct *task)
+{
+        struct perf_comm_event comm_event;
+
+        if (task->perf_event_ctxp)
+                perf_event_enable_on_exec(task);
+
+        if (!atomic_read(&nr_comm_events))
+                return;
+
+        comm_event = (struct perf_comm_event){
+                .task   = task,
+                /* .comm      */
+                /* .comm_size */
+                .event_id  = {
+                        .header = {
+                                .type = PERF_RECORD_COMM,
+                                .misc = 0,
+                                /* .size */
+                        },
+                        /* .pid */
+                        /* .tid */
+                },
+        };
+
+        perf_event_comm_event(&comm_event);
+}
+
+/*
+ * mmap tracking
+ */
+
+struct perf_mmap_event {
+        struct vm_area_struct   *vma;
+
+        const char              *file_name;
+        int                     file_size;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             tid;
+                u64                             start;
+                u64                             len;
+                u64                             pgoff;
+        } event_id;
+};
+
+static void perf_event_mmap_output(struct perf_event *event,
+                                     struct perf_mmap_event *mmap_event)
+{
+        struct perf_output_handle handle;
+        int size = mmap_event->event_id.header.size;
+        int ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        mmap_event->event_id.pid = perf_event_pid(event, current);
+        mmap_event->event_id.tid = perf_event_tid(event, current);
+
+        perf_output_put(&handle, mmap_event->event_id);
+        perf_output_copy(&handle, mmap_event->file_name,
+                                   mmap_event->file_size);
+        perf_output_end(&handle);
+}
+
+static int perf_event_mmap_match(struct perf_event *event,
+                                   struct perf_mmap_event *mmap_event)
+{
+        if (event->attr.mmap)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_mmap_ctx(struct perf_event_context *ctx,
+                                  struct perf_mmap_event *mmap_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_mmap_match(event, mmap_event))
+                        perf_event_mmap_output(event, mmap_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+        struct vm_area_struct *vma = mmap_event->vma;
+        struct file *file = vma->vm_file;
+        unsigned int size;
+        char tmp[16];
+        char *buf = NULL;
+        const char *name;
+
+        memset(tmp, 0, sizeof(tmp));
+
+        if (file) {
+                /*
+                 * d_path works from the end of the buffer backwards, so we
+                 * need to add enough zero bytes after the string to handle
+                 * the 64bit alignment we do later.
+                 */
+                buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);
+                if (!buf) {
+                        name = strncpy(tmp, "//enomem", sizeof(tmp));
+                        goto got_name;
+                }
+                name = d_path(&file->f_path, buf, PATH_MAX);
+                if (IS_ERR(name)) {
+                        name = strncpy(tmp, "//toolong", sizeof(tmp));
+                        goto got_name;
+                }
+        } else {
+                if (arch_vma_name(mmap_event->vma)) {
+                        name = strncpy(tmp, arch_vma_name(mmap_event->vma),
+                                       sizeof(tmp));
+                        goto got_name;
+                }
+
+                if (!vma->vm_mm) {
+                        name = strncpy(tmp, "[vdso]", sizeof(tmp));
+                        goto got_name;
+                }
+
+                name = strncpy(tmp, "//anon", sizeof(tmp));
+                goto got_name;
+        }
+
+got_name:
+        size = ALIGN(strlen(name)+1, sizeof(u64));
+
+        mmap_event->file_name = name;
+        mmap_event->file_size = size;
+
+        mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_mmap_ctx(&cpuctx->ctx, mmap_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_event_mmap_ctx(ctx, mmap_event);
+        rcu_read_unlock();
+
+        kfree(buf);
+}
+
+void __perf_event_mmap(struct vm_area_struct *vma)
+{
+        struct perf_mmap_event mmap_event;
+
+        if (!atomic_read(&nr_mmap_events))
+                return;
+
+        mmap_event = (struct perf_mmap_event){
+                .vma    = vma,
+                /* .file_name */
+                /* .file_size */
+                .event_id  = {
+                        .header = {
+                                .type = PERF_RECORD_MMAP,
+                                .misc = 0,
+                                /* .size */
+                        },
+                        /* .pid */
+                        /* .tid */
+                        .start  = vma->vm_start,
+                        .len    = vma->vm_end - vma->vm_start,
+                        .pgoff  = vma->vm_pgoff,
+                },
+        };
+
+        perf_event_mmap_event(&mmap_event);
+}
+
+/*
+ * IRQ throttle logging
+ */
+
+static void perf_log_throttle(struct perf_event *event, int enable)
+{
+        struct perf_output_handle handle;
+        int ret;
+
+        struct {
+                struct perf_event_header        header;
+                u64                             time;
+                u64                             id;
+                u64                             stream_id;
+        } throttle_event = {
+                .header = {
+                        .type = PERF_RECORD_THROTTLE,
+                        .misc = 0,
+                        .size = sizeof(throttle_event),
+                },
+                .time           = perf_clock(),
+                .id             = primary_event_id(event),
+                .stream_id      = event->id,
+        };
+
+        if (enable)
+                throttle_event.header.type = PERF_RECORD_UNTHROTTLE;
+
+        ret = perf_output_begin(&handle, event, sizeof(throttle_event), 1, 0);
+        if (ret)
+                return;
+
+        perf_output_put(&handle, throttle_event);
+        perf_output_end(&handle);
+}
+
+/*
+ * Generic event overflow handling, sampling.
+ */
+
+static int __perf_event_overflow(struct perf_event *event, int nmi,
+                                   int throttle, struct perf_sample_data *data,
+                                   struct pt_regs *regs)
+{
+        int events = atomic_read(&event->event_limit);
+        struct hw_perf_event *hwc = &event->hw;
+        int ret = 0;
+
+        throttle = (throttle && event->pmu->unthrottle != NULL);
+
+        if (!throttle) {
+                hwc->interrupts++;
+        } else {
+                if (hwc->interrupts != MAX_INTERRUPTS) {
+                        hwc->interrupts++;
+                        if (HZ * hwc->interrupts >
+                                        (u64)sysctl_perf_event_sample_rate) {
+                                hwc->interrupts = MAX_INTERRUPTS;
+                                perf_log_throttle(event, 0);
+                                ret = 1;
+                        }
+                } else {
+                        /*
+                         * Keep re-disabling events even though on the previous
+                         * pass we disabled it - just in case we raced with a
+                         * sched-in and the event got enabled again:
+                         */
+                        ret = 1;
+                }
+        }
+
+        if (event->attr.freq) {
+                u64 now = perf_clock();
+                s64 delta = now - hwc->freq_stamp;
+
+                hwc->freq_stamp = now;
+
+                if (delta > 0 && delta < TICK_NSEC)
+                        perf_adjust_period(event, NSEC_PER_SEC / (int)delta);
+        }
+
+        /*
+         * XXX event_limit might not quite work as expected on inherited
+         * events
+         */
+
+        event->pending_kill = POLL_IN;
+        if (events && atomic_dec_and_test(&event->event_limit)) {
+                ret = 1;
+                event->pending_kill = POLL_HUP;
+                if (nmi) {
+                        event->pending_disable = 1;
+                        perf_pending_queue(&event->pending,
+                                           perf_pending_event);
+                } else
+                        perf_event_disable(event);
+        }
+
+        perf_event_output(event, nmi, data, regs);
+        return ret;
+}
+
+int perf_event_overflow(struct perf_event *event, int nmi,
+                          struct perf_sample_data *data,
+                          struct pt_regs *regs)
+{
+        return __perf_event_overflow(event, nmi, 1, data, regs);
+}
+
+/*
+ * Generic software event infrastructure
+ */
+
+/*
+ * We directly increment event->count and keep a second value in
+ * event->hw.period_left to count intervals. This period event
+ * is kept in the range [-sample_period, 0] so that we can use the
+ * sign as trigger.
+ */
+
+static u64 perf_swevent_set_period(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 period = hwc->last_period;
+        u64 nr, offset;
+        s64 old, val;
+
+        hwc->last_period = hwc->sample_period;
+
+again:
+        old = val = atomic64_read(&hwc->period_left);
+        if (val < 0)
+                return 0;
+
+        nr = div64_u64(period + val, period);
+        offset = nr * period;
+        val -= offset;
+        if (atomic64_cmpxchg(&hwc->period_left, old, val) != old)
+                goto again;
+
+        return nr;
+}
+
+static void perf_swevent_overflow(struct perf_event *event,
+                                    int nmi, struct perf_sample_data *data,
+                                    struct pt_regs *regs)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        int throttle = 0;
+        u64 overflow;
+
+        data->period = event->hw.last_period;
+        overflow = perf_swevent_set_period(event);
+
+        if (hwc->interrupts == MAX_INTERRUPTS)
+                return;
+
+        for (; overflow; overflow--) {
+                if (__perf_event_overflow(event, nmi, throttle,
+                                            data, regs)) {
+                        /*
+                         * We inhibit the overflow from happening when
+                         * hwc->interrupts == MAX_INTERRUPTS.
+                         */
+                        break;
+                }
+                throttle = 1;
+        }
+}
+
+static void perf_swevent_unthrottle(struct perf_event *event)
+{
+        /*
+         * Nothing to do, we already reset hwc->interrupts.
+         */
+}
+
+static void perf_swevent_add(struct perf_event *event, u64 nr,
+                               int nmi, struct perf_sample_data *data,
+                               struct pt_regs *regs)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        atomic64_add(nr, &event->count);
+
+        if (!hwc->sample_period)
+                return;
+
+        if (!regs)
+                return;
+
+        if (!atomic64_add_negative(nr, &hwc->period_left))
+                perf_swevent_overflow(event, nmi, data, regs);
+}
+
+static int perf_swevent_is_counting(struct perf_event *event)
+{
+        /*
+         * The event is active, we're good!
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE)
+                return 1;
+
+        /*
+         * The event is off/error, not counting.
+         */
+        if (event->state != PERF_EVENT_STATE_INACTIVE)
+                return 0;
+
+        /*
+         * The event is inactive, if the context is active
+         * we're part of a group that didn't make it on the 'pmu',
+         * not counting.
+         */
+        if (event->ctx->is_active)
+                return 0;
+
+        /*
+         * We're inactive and the context is too, this means the
+         * task is scheduled out, we're counting events that happen
+         * to us, like migration events.
+         */
+        return 1;
+}
+
+static int perf_swevent_match(struct perf_event *event,
+                                enum perf_type_id type,
+                                u32 event_id, struct pt_regs *regs)
+{
+        if (!perf_swevent_is_counting(event))
+                return 0;
+
+        if (event->attr.type != type)
+                return 0;
+        if (event->attr.config != event_id)
+                return 0;
+
+        if (regs) {
+                if (event->attr.exclude_user && user_mode(regs))
+                        return 0;
+
+                if (event->attr.exclude_kernel && !user_mode(regs))
+                        return 0;
+        }
+
+        return 1;
+}
+
+static void perf_swevent_ctx_event(struct perf_event_context *ctx,
+                                     enum perf_type_id type,
+                                     u32 event_id, u64 nr, int nmi,
+                                     struct perf_sample_data *data,
+                                     struct pt_regs *regs)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_swevent_match(event, type, event_id, regs))
+                        perf_swevent_add(event, nr, nmi, data, regs);
+        }
+        rcu_read_unlock();
+}
+
+static int *perf_swevent_recursion_context(struct perf_cpu_context *cpuctx)
+{
+        if (in_nmi())
+                return &cpuctx->recursion[3];
+
+        if (in_irq())
+                return &cpuctx->recursion[2];
+
+        if (in_softirq())
+                return &cpuctx->recursion[1];
+
+        return &cpuctx->recursion[0];
+}
+
+static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
+                                    u64 nr, int nmi,
+                                    struct perf_sample_data *data,
+                                    struct pt_regs *regs)
+{
+        struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);
+        int *recursion = perf_swevent_recursion_context(cpuctx);
+        struct perf_event_context *ctx;
+
+        if (*recursion)
+                goto out;
+
+        (*recursion)++;
+        barrier();
+
+        perf_swevent_ctx_event(&cpuctx->ctx, type, event_id,
+                                 nr, nmi, data, regs);
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_swevent_ctx_event(ctx, type, event_id, nr, nmi, data, regs);
+        rcu_read_unlock();
+
+        barrier();
+        (*recursion)--;
+
+out:
+        put_cpu_var(perf_cpu_context);
+}
+
+void __perf_sw_event(u32 event_id, u64 nr, int nmi,
+                            struct pt_regs *regs, u64 addr)
+{
+        struct perf_sample_data data = {
+                .addr = addr,
+        };
+
+        do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi,
+                                &data, regs);
+}
+
+static void perf_swevent_read(struct perf_event *event)
+{
+}
+
+static int perf_swevent_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        if (hwc->sample_period) {
+                hwc->last_period = hwc->sample_period;
+                perf_swevent_set_period(event);
+        }
+        return 0;
+}
+
+static void perf_swevent_disable(struct perf_event *event)
+{
+}
+
+static const struct pmu perf_ops_generic = {
+        .enable         = perf_swevent_enable,
+        .disable        = perf_swevent_disable,
+        .read           = perf_swevent_read,
+        .unthrottle     = perf_swevent_unthrottle,
+};
+
+/*
+ * hrtimer based swevent callback
+ */
+
+static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
+{
+        enum hrtimer_restart ret = HRTIMER_RESTART;
+        struct perf_sample_data data;
+        struct pt_regs *regs;
+        struct perf_event *event;
+        u64 period;
+
+        event   = container_of(hrtimer, struct perf_event, hw.hrtimer);
+        event->pmu->read(event);
+
+        data.addr = 0;
+        regs = get_irq_regs();
+        /*
+         * In case we exclude kernel IPs or are somehow not in interrupt
+         * context, provide the next best thing, the user IP.
+         */
+        if ((event->attr.exclude_kernel || !regs) &&
+                        !event->attr.exclude_user)
+                regs = task_pt_regs(current);
+
+        if (regs) {
+                if (perf_event_overflow(event, 0, &data, regs))
+                        ret = HRTIMER_NORESTART;
+        }
+
+        period = max_t(u64, 10000, event->hw.sample_period);
+        hrtimer_forward_now(hrtimer, ns_to_ktime(period));
+
+        return ret;
+}
+
+/*
+ * Software event: cpu wall time clock
+ */
+
+static void cpu_clock_perf_event_update(struct perf_event *event)
+{
+        int cpu = raw_smp_processor_id();
+        s64 prev;
+        u64 now;
+
+        now = cpu_clock(cpu);
+        prev = atomic64_read(&event->hw.prev_count);
+        atomic64_set(&event->hw.prev_count, now);
+        atomic64_add(now - prev, &event->count);
+}
+
+static int cpu_clock_perf_event_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        int cpu = raw_smp_processor_id();
+
+        atomic64_set(&hwc->prev_count, cpu_clock(cpu));
+        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hwc->hrtimer.function = perf_swevent_hrtimer;
+        if (hwc->sample_period) {
+                u64 period = max_t(u64, 10000, hwc->sample_period);
+                __hrtimer_start_range_ns(&hwc->hrtimer,
+                                ns_to_ktime(period), 0,
+                                HRTIMER_MODE_REL, 0);
+        }
+
+        return 0;
+}
+
+static void cpu_clock_perf_event_disable(struct perf_event *event)
+{
+        if (event->hw.sample_period)
+                hrtimer_cancel(&event->hw.hrtimer);
+        cpu_clock_perf_event_update(event);
+}
+
+static void cpu_clock_perf_event_read(struct perf_event *event)
+{
+        cpu_clock_perf_event_update(event);
+}
+
+static const struct pmu perf_ops_cpu_clock = {
+        .enable         = cpu_clock_perf_event_enable,
+        .disable        = cpu_clock_perf_event_disable,
+        .read           = cpu_clock_perf_event_read,
+};
+
+/*
+ * Software event: task time clock
+ */
+
+static void task_clock_perf_event_update(struct perf_event *event, u64 now)
+{
+        u64 prev;
+        s64 delta;
+
+        prev = atomic64_xchg(&event->hw.prev_count, now);
+        delta = now - prev;
+        atomic64_add(delta, &event->count);
+}
+
+static int task_clock_perf_event_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 now;
+
+        now = event->ctx->time;
+
+        atomic64_set(&hwc->prev_count, now);
+        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hwc->hrtimer.function = perf_swevent_hrtimer;
+        if (hwc->sample_period) {
+                u64 period = max_t(u64, 10000, hwc->sample_period);
+                __hrtimer_start_range_ns(&hwc->hrtimer,
+                                ns_to_ktime(period), 0,
+                                HRTIMER_MODE_REL, 0);
+        }
+
+        return 0;
+}
+
+static void task_clock_perf_event_disable(struct perf_event *event)
+{
+        if (event->hw.sample_period)
+                hrtimer_cancel(&event->hw.hrtimer);
+        task_clock_perf_event_update(event, event->ctx->time);
+
+}
+
+static void task_clock_perf_event_read(struct perf_event *event)
+{
+        u64 time;
+
+        if (!in_nmi()) {
+                update_context_time(event->ctx);
+                time = event->ctx->time;
+        } else {
+                u64 now = perf_clock();
+                u64 delta = now - event->ctx->timestamp;
+                time = event->ctx->time + delta;
+        }
+
+        task_clock_perf_event_update(event, time);
+}
+
+static const struct pmu perf_ops_task_clock = {
+        .enable         = task_clock_perf_event_enable,
+        .disable        = task_clock_perf_event_disable,
+        .read           = task_clock_perf_event_read,
+};
+
+#ifdef CONFIG_EVENT_PROFILE
+void perf_tp_event(int event_id, u64 addr, u64 count, void *record,
+                          int entry_size)
+{
+        struct perf_raw_record raw = {
+                .size = entry_size,
+                .data = record,
+        };
+
+        struct perf_sample_data data = {
+                .addr = addr,
+                .raw = &raw,
+        };
+
+        struct pt_regs *regs = get_irq_regs();
+
+        if (!regs)
+                regs = task_pt_regs(current);
+
+        do_perf_sw_event(PERF_TYPE_TRACEPOINT, event_id, count, 1,
+                                &data, regs);
+}
+EXPORT_SYMBOL_GPL(perf_tp_event);
+
+extern int ftrace_profile_enable(int);
+extern void ftrace_profile_disable(int);
+
+static void tp_perf_event_destroy(struct perf_event *event)
+{
+        ftrace_profile_disable(event->attr.config);
+}
+
+static const struct pmu *tp_perf_event_init(struct perf_event *event)
+{
+        /*
+         * Raw tracepoint data is a severe data leak, only allow root to
+         * have these.
+         */
+        if ((event->attr.sample_type & PERF_SAMPLE_RAW) &&
+                        perf_paranoid_tracepoint_raw() &&
+                        !capable(CAP_SYS_ADMIN))
+                return ERR_PTR(-EPERM);
+
+        if (ftrace_profile_enable(event->attr.config))
+                return NULL;
+
+        event->destroy = tp_perf_event_destroy;
+
+        return &perf_ops_generic;
+}
+#else
+static const struct pmu *tp_perf_event_init(struct perf_event *event)
+{
+        return NULL;
+}
+#endif
+
+atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
+
+static void sw_perf_event_destroy(struct perf_event *event)
+{
+        u64 event_id = event->attr.config;
+
+        WARN_ON(event->parent);
+
+        atomic_dec(&perf_swevent_enabled[event_id]);
+}
+
+static const struct pmu *sw_perf_event_init(struct perf_event *event)
+{
+        const struct pmu *pmu = NULL;
+        u64 event_id = event->attr.config;
+
+        /*
+         * Software events (currently) can't in general distinguish
+         * between user, kernel and hypervisor events.
+         * However, context switches and cpu migrations are considered
+         * to be kernel events, and page faults are never hypervisor
+         * events.
+         */
+        switch (event_id) {
+        case PERF_COUNT_SW_CPU_CLOCK:
+                pmu = &perf_ops_cpu_clock;
+
+                break;
+        case PERF_COUNT_SW_TASK_CLOCK:
+                /*
+                 * If the user instantiates this as a per-cpu event,
+                 * use the cpu_clock event instead.
+                 */
+                if (event->ctx->task)
+                        pmu = &perf_ops_task_clock;
+                else
+                        pmu = &perf_ops_cpu_clock;
+
+                break;
+        case PERF_COUNT_SW_PAGE_FAULTS:
+        case PERF_COUNT_SW_PAGE_FAULTS_MIN:
+        case PERF_COUNT_SW_PAGE_FAULTS_MAJ:
+        case PERF_COUNT_SW_CONTEXT_SWITCHES:
+        case PERF_COUNT_SW_CPU_MIGRATIONS:
+                if (!event->parent) {
+                        atomic_inc(&perf_swevent_enabled[event_id]);
+                        event->destroy = sw_perf_event_destroy;
+                }
+                pmu = &perf_ops_generic;
+                break;
+        }
+
+        return pmu;
+}
+
+/*
+ * Allocate and initialize a event structure
+ */
+static struct perf_event *
+perf_event_alloc(struct perf_event_attr *attr,
+                   int cpu,
+                   struct perf_event_context *ctx,
+                   struct perf_event *group_leader,
+                   struct perf_event *parent_event,
+                   gfp_t gfpflags)
+{
+        const struct pmu *pmu;
+        struct perf_event *event;
+        struct hw_perf_event *hwc;
+        long err;
+
+        event = kzalloc(sizeof(*event), gfpflags);
+        if (!event)
+                return ERR_PTR(-ENOMEM);
+
+        /*
+         * Single events are their own group leaders, with an
+         * empty sibling list:
+         */
+        if (!group_leader)
+                group_leader = event;
+
+        mutex_init(&event->child_mutex);
+        INIT_LIST_HEAD(&event->child_list);
+
+        INIT_LIST_HEAD(&event->group_entry);
+        INIT_LIST_HEAD(&event->event_entry);
+        INIT_LIST_HEAD(&event->sibling_list);
+        init_waitqueue_head(&event->waitq);
+
+        mutex_init(&event->mmap_mutex);
+
+        event->cpu              = cpu;
+        event->attr             = *attr;
+        event->group_leader     = group_leader;
+        event->pmu              = NULL;
+        event->ctx              = ctx;
+        event->oncpu            = -1;
+
+        event->parent           = parent_event;
+
+        event->ns               = get_pid_ns(current->nsproxy->pid_ns);
+        event->id               = atomic64_inc_return(&perf_event_id);
+
+        event->state            = PERF_EVENT_STATE_INACTIVE;
+
+        if (attr->disabled)
+                event->state = PERF_EVENT_STATE_OFF;
+
+        pmu = NULL;
+
+        hwc = &event->hw;
+        hwc->sample_period = attr->sample_period;
+        if (attr->freq && attr->sample_freq)
+                hwc->sample_period = 1;
+        hwc->last_period = hwc->sample_period;
+
+        atomic64_set(&hwc->period_left, hwc->sample_period);
+
+        /*
+         * we currently do not support PERF_FORMAT_GROUP on inherited events
+         */
+        if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
+                goto done;
+
+        switch (attr->type) {
+        case PERF_TYPE_RAW:
+        case PERF_TYPE_HARDWARE:
+        case PERF_TYPE_HW_CACHE:
+                pmu = hw_perf_event_init(event);
+                break;
+
+        case PERF_TYPE_SOFTWARE:
+                pmu = sw_perf_event_init(event);
+                break;
+
+        case PERF_TYPE_TRACEPOINT:
+                pmu = tp_perf_event_init(event);
+                break;
+
+        default:
+                break;
+        }
+done:
+        err = 0;
+        if (!pmu)
+                err = -EINVAL;
+        else if (IS_ERR(pmu))
+                err = PTR_ERR(pmu);
+
+        if (err) {
+                if (event->ns)
+                        put_pid_ns(event->ns);
+                kfree(event);
+                return ERR_PTR(err);
+        }
+
+        event->pmu = pmu;
+
+        if (!event->parent) {
+                atomic_inc(&nr_events);
+                if (event->attr.mmap)
+                        atomic_inc(&nr_mmap_events);
+                if (event->attr.comm)
+                        atomic_inc(&nr_comm_events);
+                if (event->attr.task)
+                        atomic_inc(&nr_task_events);
+        }
+
+        return event;
+}
+
+static int perf_copy_attr(struct perf_event_attr __user *uattr,
+                          struct perf_event_attr *attr)
+{
+        u32 size;
+        int ret;
+
+        if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
+                return -EFAULT;
+
+        /*
+         * zero the full structure, so that a short copy will be nice.
+         */
+        memset(attr, 0, sizeof(*attr));
+
+        ret = get_user(size, &uattr->size);
+        if (ret)
+                return ret;
+
+        if (size > PAGE_SIZE)   /* silly large */
+                goto err_size;
+
+        if (!size)              /* abi compat */
+                size = PERF_ATTR_SIZE_VER0;
+
+        if (size < PERF_ATTR_SIZE_VER0)
+                goto err_size;
+
+        /*
+         * If we're handed a bigger struct than we know of,
+         * ensure all the unknown bits are 0 - i.e. new
+         * user-space does not rely on any kernel feature
+         * extensions we dont know about yet.
+         */
+        if (size > sizeof(*attr)) {
+                unsigned char __user *addr;
+                unsigned char __user *end;
+                unsigned char val;
+
+                addr = (void __user *)uattr + sizeof(*attr);
+                end  = (void __user *)uattr + size;
+
+                for (; addr < end; addr++) {
+                        ret = get_user(val, addr);
+                        if (ret)
+                                return ret;
+                        if (val)
+                                goto err_size;
+                }
+                size = sizeof(*attr);
+        }
+
+        ret = copy_from_user(attr, uattr, size);
+        if (ret)
+                return -EFAULT;
+
+        /*
+         * If the type exists, the corresponding creation will verify
+         * the attr->config.
+         */
+        if (attr->type >= PERF_TYPE_MAX)
+                return -EINVAL;
+
+        if (attr->__reserved_1 || attr->__reserved_2 || attr->__reserved_3)
+                return -EINVAL;
+
+        if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))
+                return -EINVAL;
+
+        if (attr->read_format & ~(PERF_FORMAT_MAX-1))
+                return -EINVAL;
+
+out:
+        return ret;
+
+err_size:
+        put_user(sizeof(*attr), &uattr->size);
+        ret = -E2BIG;
+        goto out;
+}
+
+int perf_event_set_output(struct perf_event *event, int output_fd)
+{
+        struct perf_event *output_event = NULL;
+        struct file *output_file = NULL;
+        struct perf_event *old_output;
+        int fput_needed = 0;
+        int ret = -EINVAL;
+
+        if (!output_fd)
+                goto set;
+
+        output_file = fget_light(output_fd, &fput_needed);
+        if (!output_file)
+                return -EBADF;
+
+        if (output_file->f_op != &perf_fops)
+                goto out;
+
+        output_event = output_file->private_data;
+
+        /* Don't chain output fds */
+        if (output_event->output)
+                goto out;
+
+        /* Don't set an output fd when we already have an output channel */
+        if (event->data)
+                goto out;
+
+        atomic_long_inc(&output_file->f_count);
+
+set:
+        mutex_lock(&event->mmap_mutex);
+        old_output = event->output;
+        rcu_assign_pointer(event->output, output_event);
+        mutex_unlock(&event->mmap_mutex);
+
+        if (old_output) {
+                /*
+                 * we need to make sure no existing perf_output_*()
+                 * is still referencing this event.
+                 */
+                synchronize_rcu();
+                fput(old_output->filp);
+        }
+
+        ret = 0;
+out:
+        fput_light(output_file, fput_needed);
+        return ret;
+}
+
+/**
+ * sys_perf_event_open - open a performance event, associate it to a task/cpu
+ *
+ * @attr_uptr:  event_id type attributes for monitoring/sampling
+ * @pid:                target pid
+ * @cpu:                target cpu
+ * @group_fd:           group leader event fd
+ */
+SYSCALL_DEFINE5(perf_event_open,
+                struct perf_event_attr __user *, attr_uptr,
+                pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
+{
+        struct perf_event *event, *group_leader;
+        struct perf_event_attr attr;
+        struct perf_event_context *ctx;
+        struct file *event_file = NULL;
+        struct file *group_file = NULL;
+        int fput_needed = 0;
+        int fput_needed2 = 0;
+        int err;
+
+        /* for future expandability... */
+        if (flags & ~(PERF_FLAG_FD_NO_GROUP | PERF_FLAG_FD_OUTPUT))
+                return -EINVAL;
+
+        err = perf_copy_attr(attr_uptr, &attr);
+        if (err)
+                return err;
+
+        if (!attr.exclude_kernel) {
+                if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+                        return -EACCES;
+        }
+
+        if (attr.freq) {
+                if (attr.sample_freq > sysctl_perf_event_sample_rate)
+                        return -EINVAL;
+        }
+
+        /*
+         * Get the target context (task or percpu):
+         */
+        ctx = find_get_context(pid, cpu);
+        if (IS_ERR(ctx))
+                return PTR_ERR(ctx);
+
+        /*
+         * Look up the group leader (we will attach this event to it):
+         */
+        group_leader = NULL;
+        if (group_fd != -1 && !(flags & PERF_FLAG_FD_NO_GROUP)) {
+                err = -EINVAL;
+                group_file = fget_light(group_fd, &fput_needed);
+                if (!group_file)
+                        goto err_put_context;
+                if (group_file->f_op != &perf_fops)
+                        goto err_put_context;
+
+                group_leader = group_file->private_data;
+                /*
+                 * Do not allow a recursive hierarchy (this new sibling
+                 * becoming part of another group-sibling):
+                 */
+                if (group_leader->group_leader != group_leader)
+                        goto err_put_context;
+                /*
+                 * Do not allow to attach to a group in a different
+                 * task or CPU context:
+                 */
+                if (group_leader->ctx != ctx)
+                        goto err_put_context;
+                /*
+                 * Only a group leader can be exclusive or pinned
+                 */
+                if (attr.exclusive || attr.pinned)
+                        goto err_put_context;
+        }
+
+        event = perf_event_alloc(&attr, cpu, ctx, group_leader,
+                                     NULL, GFP_KERNEL);
+        err = PTR_ERR(event);
+        if (IS_ERR(event))
+                goto err_put_context;
+
+        err = anon_inode_getfd("[perf_event]", &perf_fops, event, 0);
+        if (err < 0)
+                goto err_free_put_context;
+
+        event_file = fget_light(err, &fput_needed2);
+        if (!event_file)
+                goto err_free_put_context;
+
+        if (flags & PERF_FLAG_FD_OUTPUT) {
+                err = perf_event_set_output(event, group_fd);
+                if (err)
+                        goto err_fput_free_put_context;
+        }
+
+        event->filp = event_file;
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        perf_install_in_context(ctx, event, cpu);
+        ++ctx->generation;
+        mutex_unlock(&ctx->mutex);
+
+        event->owner = current;
+        get_task_struct(current);
+        mutex_lock(&current->perf_event_mutex);
+        list_add_tail(&event->owner_entry, &current->perf_event_list);
+        mutex_unlock(&current->perf_event_mutex);
+
+err_fput_free_put_context:
+        fput_light(event_file, fput_needed2);
+
+err_free_put_context:
+        if (err < 0)
+                kfree(event);
+
+err_put_context:
+        if (err < 0)
+                put_ctx(ctx);
+
+        fput_light(group_file, fput_needed);
+
+        return err;
+}
+
+/*
+ * inherit a event from parent task to child task:
+ */
+static struct perf_event *
+inherit_event(struct perf_event *parent_event,
+              struct task_struct *parent,
+              struct perf_event_context *parent_ctx,
+              struct task_struct *child,
+              struct perf_event *group_leader,
+              struct perf_event_context *child_ctx)
+{
+        struct perf_event *child_event;
+
+        /*
+         * Instead of creating recursive hierarchies of events,
+         * we link inherited events back to the original parent,
+         * which has a filp for sure, which we use as the reference
+         * count:
+         */
+        if (parent_event->parent)
+                parent_event = parent_event->parent;
+
+        child_event = perf_event_alloc(&parent_event->attr,
+                                           parent_event->cpu, child_ctx,
+                                           group_leader, parent_event,
+                                           GFP_KERNEL);
+        if (IS_ERR(child_event))
+                return child_event;
+        get_ctx(child_ctx);
+
+        /*
+         * Make the child state follow the state of the parent event,
+         * not its attr.disabled bit.  We hold the parent's mutex,
+         * so we won't race with perf_event_{en, dis}able_family.
+         */
+        if (parent_event->state >= PERF_EVENT_STATE_INACTIVE)
+                child_event->state = PERF_EVENT_STATE_INACTIVE;
+        else
+                child_event->state = PERF_EVENT_STATE_OFF;
+
+        if (parent_event->attr.freq)
+                child_event->hw.sample_period = parent_event->hw.sample_period;
+
+        /*
+         * Link it up in the child's context:
+         */
+        add_event_to_ctx(child_event, child_ctx);
+
+        /*
+         * Get a reference to the parent filp - we will fput it
+         * when the child event exits. This is safe to do because
+         * we are in the parent and we know that the filp still
+         * exists and has a nonzero count:
+         */
+        atomic_long_inc(&parent_event->filp->f_count);
+
+        /*
+         * Link this into the parent event's child list
+         */
+        WARN_ON_ONCE(parent_event->ctx->parent_ctx);
+        mutex_lock(&parent_event->child_mutex);
+        list_add_tail(&child_event->child_list, &parent_event->child_list);
+        mutex_unlock(&parent_event->child_mutex);
+
+        return child_event;
+}
+
+static int inherit_group(struct perf_event *parent_event,
+              struct task_struct *parent,
+              struct perf_event_context *parent_ctx,
+              struct task_struct *child,
+              struct perf_event_context *child_ctx)
+{
+        struct perf_event *leader;
+        struct perf_event *sub;
+        struct perf_event *child_ctr;
+
+        leader = inherit_event(parent_event, parent, parent_ctx,
+                                 child, NULL, child_ctx);
+        if (IS_ERR(leader))
+                return PTR_ERR(leader);
+        list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
+                child_ctr = inherit_event(sub, parent, parent_ctx,
+                                            child, leader, child_ctx);
+                if (IS_ERR(child_ctr))
+                        return PTR_ERR(child_ctr);
+        }
+        return 0;
+}
+
+static void sync_child_event(struct perf_event *child_event,
+                               struct task_struct *child)
+{
+        struct perf_event *parent_event = child_event->parent;
+        u64 child_val;
+
+        if (child_event->attr.inherit_stat)
+                perf_event_read_event(child_event, child);
+
+        child_val = atomic64_read(&child_event->count);
+
+        /*
+         * Add back the child's count to the parent's count:
+         */
+        atomic64_add(child_val, &parent_event->count);
+        atomic64_add(child_event->total_time_enabled,
+                     &parent_event->child_total_time_enabled);
+        atomic64_add(child_event->total_time_running,
+                     &parent_event->child_total_time_running);
+
+        /*
+         * Remove this event from the parent's list
+         */
+        WARN_ON_ONCE(parent_event->ctx->parent_ctx);
+        mutex_lock(&parent_event->child_mutex);
+        list_del_init(&child_event->child_list);
+        mutex_unlock(&parent_event->child_mutex);
+
+        /*
+         * Release the parent event, if this was the last
+         * reference to it.
+         */
+        fput(parent_event->filp);
+}
+
+static void
+__perf_event_exit_task(struct perf_event *child_event,
+                         struct perf_event_context *child_ctx,
+                         struct task_struct *child)
+{
+        struct perf_event *parent_event;
+
+        update_event_times(child_event);
+        perf_event_remove_from_context(child_event);
+
+        parent_event = child_event->parent;
+        /*
+         * It can happen that parent exits first, and has events
+         * that are still around due to the child reference. These
+         * events need to be zapped - but otherwise linger.
+         */
+        if (parent_event) {
+                sync_child_event(child_event, child);
+                free_event(child_event);
+        }
+}
+
+/*
+ * When a child task exits, feed back event values to parent events.
+ */
+void perf_event_exit_task(struct task_struct *child)
+{
+        struct perf_event *child_event, *tmp;
+        struct perf_event_context *child_ctx;
+        unsigned long flags;
+
+        if (likely(!child->perf_event_ctxp)) {
+                perf_event_task(child, NULL, 0);
+                return;
+        }
+
+        local_irq_save(flags);
+        /*
+         * We can't reschedule here because interrupts are disabled,
+         * and either child is current or it is a task that can't be
+         * scheduled, so we are now safe from rescheduling changing
+         * our context.
+         */
+        child_ctx = child->perf_event_ctxp;
+        __perf_event_task_sched_out(child_ctx);
+
+        /*
+         * Take the context lock here so that if find_get_context is
+         * reading child->perf_event_ctxp, we wait until it has
+         * incremented the context's refcount before we do put_ctx below.
+         */
+        spin_lock(&child_ctx->lock);
+        child->perf_event_ctxp = NULL;
+        /*
+         * If this context is a clone; unclone it so it can't get
+         * swapped to another process while we're removing all
+         * the events from it.
+         */
+        unclone_ctx(child_ctx);
+        spin_unlock_irqrestore(&child_ctx->lock, flags);
+
+        /*
+         * Report the task dead after unscheduling the events so that we
+         * won't get any samples after PERF_RECORD_EXIT. We can however still
+         * get a few PERF_RECORD_READ events.
+         */
+        perf_event_task(child, child_ctx, 0);
+
+        /*
+         * We can recurse on the same lock type through:
+         *
+         *   __perf_event_exit_task()
+         *     sync_child_event()
+         *       fput(parent_event->filp)
+         *         perf_release()
+         *           mutex_lock(&ctx->mutex)
+         *
+         * But since its the parent context it won't be the same instance.
+         */
+        mutex_lock_nested(&child_ctx->mutex, SINGLE_DEPTH_NESTING);
+
+again:
+        list_for_each_entry_safe(child_event, tmp, &child_ctx->group_list,
+                                 group_entry)
+                __perf_event_exit_task(child_event, child_ctx, child);
+
+        /*
+         * If the last event was a group event, it will have appended all
+         * its siblings to the list, but we obtained 'tmp' before that which
+         * will still point to the list head terminating the iteration.
+         */
+        if (!list_empty(&child_ctx->group_list))
+                goto again;
+
+        mutex_unlock(&child_ctx->mutex);
+
+        put_ctx(child_ctx);
+}
+
+/*
+ * free an unexposed, unused context as created by inheritance by
+ * init_task below, used by fork() in case of fail.
+ */
+void perf_event_free_task(struct task_struct *task)
+{
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+        struct perf_event *event, *tmp;
+
+        if (!ctx)
+                return;
+
+        mutex_lock(&ctx->mutex);
+again:
+        list_for_each_entry_safe(event, tmp, &ctx->group_list, group_entry) {
+                struct perf_event *parent = event->parent;
+
+                if (WARN_ON_ONCE(!parent))
+                        continue;
+
+                mutex_lock(&parent->child_mutex);
+                list_del_init(&event->child_list);
+                mutex_unlock(&parent->child_mutex);
+
+                fput(parent->filp);
+
+                list_del_event(event, ctx);
+                free_event(event);
+        }
+
+        if (!list_empty(&ctx->group_list))
+                goto again;
+
+        mutex_unlock(&ctx->mutex);
+
+        put_ctx(ctx);
+}
+
+/*
+ * Initialize the perf_event context in task_struct
+ */
+int perf_event_init_task(struct task_struct *child)
+{
+        struct perf_event_context *child_ctx, *parent_ctx;
+        struct perf_event_context *cloned_ctx;
+        struct perf_event *event;
+        struct task_struct *parent = current;
+        int inherited_all = 1;
+        int ret = 0;
+
+        child->perf_event_ctxp = NULL;
+
+        mutex_init(&child->perf_event_mutex);
+        INIT_LIST_HEAD(&child->perf_event_list);
+
+        if (likely(!parent->perf_event_ctxp))
+                return 0;
+
+        /*
+         * This is executed from the parent task context, so inherit
+         * events that have been marked for cloning.
+         * First allocate and initialize a context for the child.
+         */
+
+        child_ctx = kmalloc(sizeof(struct perf_event_context), GFP_KERNEL);
+        if (!child_ctx)
+                return -ENOMEM;
+
+        __perf_event_init_context(child_ctx, child);
+        child->perf_event_ctxp = child_ctx;
+        get_task_struct(child);
+
+        /*
+         * If the parent's context is a clone, pin it so it won't get
+         * swapped under us.
+         */
+        parent_ctx = perf_pin_task_context(parent);
+
+        /*
+         * No need to check if parent_ctx != NULL here; since we saw
+         * it non-NULL earlier, the only reason for it to become NULL
+         * is if we exit, and since we're currently in the middle of
+         * a fork we can't be exiting at the same time.
+         */
+
+        /*
+         * Lock the parent list. No need to lock the child - not PID
+         * hashed yet and not running, so nobody can access it.
+         */
+        mutex_lock(&parent_ctx->mutex);
+
+        /*
+         * We dont have to disable NMIs - we are only looking at
+         * the list, not manipulating it:
+         */
+        list_for_each_entry(event, &parent_ctx->group_list, group_entry) {
+
+                if (!event->attr.inherit) {
+                        inherited_all = 0;
+                        continue;
+                }
+
+                ret = inherit_group(event, parent, parent_ctx,
+                                             child, child_ctx);
+                if (ret) {
+                        inherited_all = 0;
+                        break;
+                }
+        }
+
+        if (inherited_all) {
+                /*
+                 * Mark the child context as a clone of the parent
+                 * context, or of whatever the parent is a clone of.
+                 * Note that if the parent is a clone, it could get
+                 * uncloned at any point, but that doesn't matter
+                 * because the list of events and the generation
+                 * count can't have changed since we took the mutex.
+                 */
+                cloned_ctx = rcu_dereference(parent_ctx->parent_ctx);
+                if (cloned_ctx) {
+                        child_ctx->parent_ctx = cloned_ctx;
+                        child_ctx->parent_gen = parent_ctx->parent_gen;
+                } else {
+                        child_ctx->parent_ctx = parent_ctx;
+                        child_ctx->parent_gen = parent_ctx->generation;
+                }
+                get_ctx(child_ctx->parent_ctx);
+        }
+
+        mutex_unlock(&parent_ctx->mutex);
+
+        perf_unpin_context(parent_ctx);
+
+        return ret;
+}
+
+static void __cpuinit perf_event_init_cpu(int cpu)
+{
+        struct perf_cpu_context *cpuctx;
+
+        cpuctx = &per_cpu(perf_cpu_context, cpu);
+        __perf_event_init_context(&cpuctx->ctx, NULL);
+
+        spin_lock(&perf_resource_lock);
+        cpuctx->max_pertask = perf_max_events - perf_reserved_percpu;
+        spin_unlock(&perf_resource_lock);
+
+        hw_perf_event_setup(cpu);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void __perf_event_exit_cpu(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = &cpuctx->ctx;
+        struct perf_event *event, *tmp;
+
+        list_for_each_entry_safe(event, tmp, &ctx->group_list, group_entry)
+                __perf_event_remove_from_context(event);
+}
+static void perf_event_exit_cpu(int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = &cpuctx->ctx;
+
+        mutex_lock(&ctx->mutex);
+        smp_call_function_single(cpu, __perf_event_exit_cpu, NULL, 1);
+        mutex_unlock(&ctx->mutex);
+}
+#else
+static inline void perf_event_exit_cpu(int cpu) { }
+#endif
+
+static int __cpuinit
+perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
+{
+        unsigned int cpu = (long)hcpu;
+
+        switch (action) {
+
+        case CPU_UP_PREPARE:
+        case CPU_UP_PREPARE_FROZEN:
+                perf_event_init_cpu(cpu);
+                break;
+
+        case CPU_ONLINE:
+        case CPU_ONLINE_FROZEN:
+                hw_perf_event_setup_online(cpu);
+                break;
+
+        case CPU_DOWN_PREPARE:
+        case CPU_DOWN_PREPARE_FROZEN:
+                perf_event_exit_cpu(cpu);
+                break;
+
+        default:
+                break;
+        }
+
+        return NOTIFY_OK;
+}
+
+/*
+ * This has to have a higher priority than migration_notifier in sched.c.
+ */
+static struct notifier_block __cpuinitdata perf_cpu_nb = {
+        .notifier_call          = perf_cpu_notify,
+        .priority               = 20,
+};
+
+void __init perf_event_init(void)
+{
+        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_UP_PREPARE,
+                        (void *)(long)smp_processor_id());
+        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_ONLINE,
+                        (void *)(long)smp_processor_id());
+        register_cpu_notifier(&perf_cpu_nb);
+}
+
+static ssize_t perf_show_reserve_percpu(struct sysdev_class *class, char *buf)
+{
+        return sprintf(buf, "%d\n", perf_reserved_percpu);
+}
+
+static ssize_t
+perf_set_reserve_percpu(struct sysdev_class *class,
+                        const char *buf,
+                        size_t count)
+{
+        struct perf_cpu_context *cpuctx;
+        unsigned long val;
+        int err, cpu, mpt;
+
+        err = strict_strtoul(buf, 10, &val);
+        if (err)
+                return err;
+        if (val > perf_max_events)
+                return -EINVAL;
+
+        spin_lock(&perf_resource_lock);
+        perf_reserved_percpu = val;
+        for_each_online_cpu(cpu) {
+                cpuctx = &per_cpu(perf_cpu_context, cpu);
+                spin_lock_irq(&cpuctx->ctx.lock);
+                mpt = min(perf_max_events - cpuctx->ctx.nr_events,
+                          perf_max_events - perf_reserved_percpu);
+                cpuctx->max_pertask = mpt;
+                spin_unlock_irq(&cpuctx->ctx.lock);
+        }
+        spin_unlock(&perf_resource_lock);
+
+        return count;
+}
+
+static ssize_t perf_show_overcommit(struct sysdev_class *class, char *buf)
+{
+        return sprintf(buf, "%d\n", perf_overcommit);
+}
+
+static ssize_t
+perf_set_overcommit(struct sysdev_class *class, const char *buf, size_t count)
+{
+        unsigned long val;
+        int err;
+
+        err = strict_strtoul(buf, 10, &val);
+        if (err)
+                return err;
+        if (val > 1)
+                return -EINVAL;
+
+        spin_lock(&perf_resource_lock);
+        perf_overcommit = val;
+        spin_unlock(&perf_resource_lock);
+
+        return count;
+}
+
+static SYSDEV_CLASS_ATTR(
+                                reserve_percpu,
+                                0644,
+                                perf_show_reserve_percpu,
+                                perf_set_reserve_percpu
+                        );
+
+static SYSDEV_CLASS_ATTR(
+                                overcommit,
+                                0644,
+                                perf_show_overcommit,
+                                perf_set_overcommit
+                        );
+
+static struct attribute *perfclass_attrs[] = {
+        &attr_reserve_percpu.attr,
+        &attr_overcommit.attr,
+        NULL
+};
+
+static struct attribute_group perfclass_attr_group = {
+        .attrs                  = perfclass_attrs,
+        .name                   = "perf_events",
+};
+
+static int __init perf_event_sysfs_init(void)
+{
+        return sysfs_create_group(&cpu_sysdev_class.kset.kobj,
+                                  &perfclass_attr_group);
+}
+device_initcall(perf_event_sysfs_init);