hw breakpoints: Move to kernel/events/

As part of the events sybsystem unification, relocate hw_breakpoint.c
into its new destination.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

2 files changed, 661 insertions, 1 deletions

diff --git a/kernel/events/Makefile b/kernel/events/Makefile
index 26c00e4570e5..1ce23d3d8394 100644
--- a/kernel/events/Makefile
+++ b/kernel/events/Makefile
@@ -2,4 +2,5 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_core.o = -pg
 endif
 
-obj-y += core.o
+obj-y := core.o
+obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
new file mode 100644
index 000000000000..086adf25a55e
--- /dev/null
+++ b/kernel/events/hw_breakpoint.c
@@ -0,0 +1,659 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) 2007 Alan Stern
+ * Copyright (C) IBM Corporation, 2009
+ * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Thanks to Ingo Molnar for his many suggestions.
+ *
+ * Authors: Alan Stern <stern@rowland.harvard.edu>
+ *          K.Prasad <prasad@linux.vnet.ibm.com>
+ *          Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ * This file contains the arch-independent routines.
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kallsyms.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+
+#include <linux/hw_breakpoint.h>
+
+
+/*
+ * Constraints data
+ */
+
+/* Number of pinned cpu breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned[TYPE_MAX]);
+
+/* Number of pinned task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int *, nr_task_bp_pinned[TYPE_MAX]);
+
+/* Number of non-pinned cpu/task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_bp_flexible[TYPE_MAX]);
+
+static int nr_slots[TYPE_MAX];
+
+/* Keep track of the breakpoints attached to tasks */
+static LIST_HEAD(bp_task_head);
+
+static int constraints_initialized;
+
+/* Gather the number of total pinned and un-pinned bp in a cpuset */
+struct bp_busy_slots {
+        unsigned int pinned;
+        unsigned int flexible;
+};
+
+/* Serialize accesses to the above constraints */
+static DEFINE_MUTEX(nr_bp_mutex);
+
+__weak int hw_breakpoint_weight(struct perf_event *bp)
+{
+        return 1;
+}
+
+static inline enum bp_type_idx find_slot_idx(struct perf_event *bp)
+{
+        if (bp->attr.bp_type & HW_BREAKPOINT_RW)
+                return TYPE_DATA;
+
+        return TYPE_INST;
+}
+
+/*
+ * Report the maximum number of pinned breakpoints a task
+ * have in this cpu
+ */
+static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
+{
+        int i;
+        unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
+
+        for (i = nr_slots[type] - 1; i >= 0; i--) {
+                if (tsk_pinned[i] > 0)
+                        return i + 1;
+        }
+
+        return 0;
+}
+
+/*
+ * Count the number of breakpoints of the same type and same task.
+ * The given event must be not on the list.
+ */
+static int task_bp_pinned(struct perf_event *bp, enum bp_type_idx type)
+{
+        struct task_struct *tsk = bp->hw.bp_target;
+        struct perf_event *iter;
+        int count = 0;
+
+        list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
+                if (iter->hw.bp_target == tsk && find_slot_idx(iter) == type)
+                        count += hw_breakpoint_weight(iter);
+        }
+
+        return count;
+}
+
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void
+fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
+                    enum bp_type_idx type)
+{
+        int cpu = bp->cpu;
+        struct task_struct *tsk = bp->hw.bp_target;
+
+        if (cpu >= 0) {
+                slots->pinned = per_cpu(nr_cpu_bp_pinned[type], cpu);
+                if (!tsk)
+                        slots->pinned += max_task_bp_pinned(cpu, type);
+                else
+                        slots->pinned += task_bp_pinned(bp, type);
+                slots->flexible = per_cpu(nr_bp_flexible[type], cpu);
+
+                return;
+        }
+
+        for_each_online_cpu(cpu) {
+                unsigned int nr;
+
+                nr = per_cpu(nr_cpu_bp_pinned[type], cpu);
+                if (!tsk)
+                        nr += max_task_bp_pinned(cpu, type);
+                else
+                        nr += task_bp_pinned(bp, type);
+
+                if (nr > slots->pinned)
+                        slots->pinned = nr;
+
+                nr = per_cpu(nr_bp_flexible[type], cpu);
+
+                if (nr > slots->flexible)
+                        slots->flexible = nr;
+        }
+}
+
+/*
+ * For now, continue to consider flexible as pinned, until we can
+ * ensure no flexible event can ever be scheduled before a pinned event
+ * in a same cpu.
+ */
+static void
+fetch_this_slot(struct bp_busy_slots *slots, int weight)
+{
+        slots->pinned += weight;
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct perf_event *bp, int cpu, bool enable,
+                                enum bp_type_idx type, int weight)
+{
+        unsigned int *tsk_pinned;
+        int old_count = 0;
+        int old_idx = 0;
+        int idx = 0;
+
+        old_count = task_bp_pinned(bp, type);
+        old_idx = old_count - 1;
+        idx = old_idx + weight;
+
+        /* tsk_pinned[n] is the number of tasks having n breakpoints */
+        tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
+        if (enable) {
+                tsk_pinned[idx]++;
+                if (old_count > 0)
+                        tsk_pinned[old_idx]--;
+        } else {
+                tsk_pinned[idx]--;
+                if (old_count > 0)
+                        tsk_pinned[old_idx]++;
+        }
+}
+
+/*
+ * Add/remove the given breakpoint in our constraint table
+ */
+static void
+toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
+               int weight)
+{
+        int cpu = bp->cpu;
+        struct task_struct *tsk = bp->hw.bp_target;
+
+        /* Pinned counter cpu profiling */
+        if (!tsk) {
+
+                if (enable)
+                        per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
+                else
+                        per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
+                return;
+        }
+
+        /* Pinned counter task profiling */
+
+        if (!enable)
+                list_del(&bp->hw.bp_list);
+
+        if (cpu >= 0) {
+                toggle_bp_task_slot(bp, cpu, enable, type, weight);
+        } else {
+                for_each_online_cpu(cpu)
+                        toggle_bp_task_slot(bp, cpu, enable, type, weight);
+        }
+
+        if (enable)
+                list_add_tail(&bp->hw.bp_list, &bp_task_head);
+}
+
+/*
+ * Function to perform processor-specific cleanup during unregistration
+ */
+__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
+{
+        /*
+         * A weak stub function here for those archs that don't define
+         * it inside arch/.../kernel/hw_breakpoint.c
+         */
+}
+
+/*
+ * Contraints to check before allowing this new breakpoint counter:
+ *
+ *  == Non-pinned counter == (Considered as pinned for now)
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
+ *           + max(per_cpu(nr_task_bp_pinned, cpu)))) < HBP_NUM
+ *
+ *       -> If there are already non-pinned counters in this cpu, it means
+ *          there is already a free slot for them.
+ *          Otherwise, we check that the maximum number of per task
+ *          breakpoints (for this cpu) plus the number of per cpu breakpoint
+ *          (for this cpu) doesn't cover every registers.
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
+ *           + max(per_cpu(nr_task_bp_pinned, *)))) < HBP_NUM
+ *
+ *       -> This is roughly the same, except we check the number of per cpu
+ *          bp for every cpu and we keep the max one. Same for the per tasks
+ *          breakpoints.
+ *
+ *
+ * == Pinned counter ==
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
+ *            + max(per_cpu(nr_task_bp_pinned, cpu))) < HBP_NUM
+ *
+ *       -> Same checks as before. But now the nr_bp_flexible, if any, must keep
+ *          one register at least (or they will never be fed).
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
+ *            + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
+ */
+static int __reserve_bp_slot(struct perf_event *bp)
+{
+        struct bp_busy_slots slots = {0};
+        enum bp_type_idx type;
+        int weight;
+
+        /* We couldn't initialize breakpoint constraints on boot */
+        if (!constraints_initialized)
+                return -ENOMEM;
+
+        /* Basic checks */
+        if (bp->attr.bp_type == HW_BREAKPOINT_EMPTY ||
+            bp->attr.bp_type == HW_BREAKPOINT_INVALID)
+                return -EINVAL;
+
+        type = find_slot_idx(bp);
+        weight = hw_breakpoint_weight(bp);
+
+        fetch_bp_busy_slots(&slots, bp, type);
+        /*
+         * Simulate the addition of this breakpoint to the constraints
+         * and see the result.
+         */
+        fetch_this_slot(&slots, weight);
+
+        /* Flexible counters need to keep at least one slot */
+        if (slots.pinned + (!!slots.flexible) > nr_slots[type])
+                return -ENOSPC;
+
+        toggle_bp_slot(bp, true, type, weight);
+
+        return 0;
+}
+
+int reserve_bp_slot(struct perf_event *bp)
+{
+        int ret;
+
+        mutex_lock(&nr_bp_mutex);
+
+        ret = __reserve_bp_slot(bp);
+
+        mutex_unlock(&nr_bp_mutex);
+
+        return ret;
+}
+
+static void __release_bp_slot(struct perf_event *bp)
+{
+        enum bp_type_idx type;
+        int weight;
+
+        type = find_slot_idx(bp);
+        weight = hw_breakpoint_weight(bp);
+        toggle_bp_slot(bp, false, type, weight);
+}
+
+void release_bp_slot(struct perf_event *bp)
+{
+        mutex_lock(&nr_bp_mutex);
+
+        arch_unregister_hw_breakpoint(bp);
+        __release_bp_slot(bp);
+
+        mutex_unlock(&nr_bp_mutex);
+}
+
+/*
+ * Allow the kernel debugger to reserve breakpoint slots without
+ * taking a lock using the dbg_* variant of for the reserve and
+ * release breakpoint slots.
+ */
+int dbg_reserve_bp_slot(struct perf_event *bp)
+{
+        if (mutex_is_locked(&nr_bp_mutex))
+                return -1;
+
+        return __reserve_bp_slot(bp);
+}
+
+int dbg_release_bp_slot(struct perf_event *bp)
+{
+        if (mutex_is_locked(&nr_bp_mutex))
+                return -1;
+
+        __release_bp_slot(bp);
+
+        return 0;
+}
+
+static int validate_hw_breakpoint(struct perf_event *bp)
+{
+        int ret;
+
+        ret = arch_validate_hwbkpt_settings(bp);
+        if (ret)
+                return ret;
+
+        if (arch_check_bp_in_kernelspace(bp)) {
+                if (bp->attr.exclude_kernel)
+                        return -EINVAL;
+                /*
+                 * Don't let unprivileged users set a breakpoint in the trap
+                 * path to avoid trap recursion attacks.
+                 */
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+        }
+
+        return 0;
+}
+
+int register_perf_hw_breakpoint(struct perf_event *bp)
+{
+        int ret;
+
+        ret = reserve_bp_slot(bp);
+        if (ret)
+                return ret;
+
+        ret = validate_hw_breakpoint(bp);
+
+        /* if arch_validate_hwbkpt_settings() fails then release bp slot */
+        if (ret)
+                release_bp_slot(bp);
+
+        return ret;
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+struct perf_event *
+register_user_hw_breakpoint(struct perf_event_attr *attr,
+                            perf_overflow_handler_t triggered,
+                            struct task_struct *tsk)
+{
+        return perf_event_create_kernel_counter(attr, -1, tsk, triggered);
+}
+EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
+
+/**
+ * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
+ * @bp: the breakpoint structure to modify
+ * @attr: new breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
+{
+        u64 old_addr = bp->attr.bp_addr;
+        u64 old_len = bp->attr.bp_len;
+        int old_type = bp->attr.bp_type;
+        int err = 0;
+
+        perf_event_disable(bp);
+
+        bp->attr.bp_addr = attr->bp_addr;
+        bp->attr.bp_type = attr->bp_type;
+        bp->attr.bp_len = attr->bp_len;
+
+        if (attr->disabled)
+                goto end;
+
+        err = validate_hw_breakpoint(bp);
+        if (!err)
+                perf_event_enable(bp);
+
+        if (err) {
+                bp->attr.bp_addr = old_addr;
+                bp->attr.bp_type = old_type;
+                bp->attr.bp_len = old_len;
+                if (!bp->attr.disabled)
+                        perf_event_enable(bp);
+
+                return err;
+        }
+
+end:
+        bp->attr.disabled = attr->disabled;
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
+
+/**
+ * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
+ * @bp: the breakpoint structure to unregister
+ */
+void unregister_hw_breakpoint(struct perf_event *bp)
+{
+        if (!bp)
+                return;
+        perf_event_release_kernel(bp);
+}
+EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
+
+/**
+ * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ *
+ * @return a set of per_cpu pointers to perf events
+ */
+struct perf_event * __percpu *
+register_wide_hw_breakpoint(struct perf_event_attr *attr,
+                            perf_overflow_handler_t triggered)
+{
+        struct perf_event * __percpu *cpu_events, **pevent, *bp;
+        long err;
+        int cpu;
+
+        cpu_events = alloc_percpu(typeof(*cpu_events));
+        if (!cpu_events)
+                return (void __percpu __force *)ERR_PTR(-ENOMEM);
+
+        get_online_cpus();
+        for_each_online_cpu(cpu) {
+                pevent = per_cpu_ptr(cpu_events, cpu);
+                bp = perf_event_create_kernel_counter(attr, cpu, NULL, triggered);
+
+                *pevent = bp;
+
+                if (IS_ERR(bp)) {
+                        err = PTR_ERR(bp);
+                        goto fail;
+                }
+        }
+        put_online_cpus();
+
+        return cpu_events;
+
+fail:
+        for_each_online_cpu(cpu) {
+                pevent = per_cpu_ptr(cpu_events, cpu);
+                if (IS_ERR(*pevent))
+                        break;
+                unregister_hw_breakpoint(*pevent);
+        }
+        put_online_cpus();
+
+        free_percpu(cpu_events);
+        return (void __percpu __force *)ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
+
+/**
+ * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
+ * @cpu_events: the per cpu set of events to unregister
+ */
+void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
+{
+        int cpu;
+        struct perf_event **pevent;
+
+        for_each_possible_cpu(cpu) {
+                pevent = per_cpu_ptr(cpu_events, cpu);
+                unregister_hw_breakpoint(*pevent);
+        }
+        free_percpu(cpu_events);
+}
+EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+        .notifier_call = hw_breakpoint_exceptions_notify,
+        /* we need to be notified first */
+        .priority = 0x7fffffff
+};
+
+static void bp_perf_event_destroy(struct perf_event *event)
+{
+        release_bp_slot(event);
+}
+
+static int hw_breakpoint_event_init(struct perf_event *bp)
+{
+        int err;
+
+        if (bp->attr.type != PERF_TYPE_BREAKPOINT)
+                return -ENOENT;
+
+        err = register_perf_hw_breakpoint(bp);
+        if (err)
+                return err;
+
+        bp->destroy = bp_perf_event_destroy;
+
+        return 0;
+}
+
+static int hw_breakpoint_add(struct perf_event *bp, int flags)
+{
+        if (!(flags & PERF_EF_START))
+                bp->hw.state = PERF_HES_STOPPED;
+
+        return arch_install_hw_breakpoint(bp);
+}
+
+static void hw_breakpoint_del(struct perf_event *bp, int flags)
+{
+        arch_uninstall_hw_breakpoint(bp);
+}
+
+static void hw_breakpoint_start(struct perf_event *bp, int flags)
+{
+        bp->hw.state = 0;
+}
+
+static void hw_breakpoint_stop(struct perf_event *bp, int flags)
+{
+        bp->hw.state = PERF_HES_STOPPED;
+}
+
+static struct pmu perf_breakpoint = {
+        .task_ctx_nr    = perf_sw_context, /* could eventually get its own */
+
+        .event_init     = hw_breakpoint_event_init,
+        .add            = hw_breakpoint_add,
+        .del            = hw_breakpoint_del,
+        .start          = hw_breakpoint_start,
+        .stop           = hw_breakpoint_stop,
+        .read           = hw_breakpoint_pmu_read,
+};
+
+int __init init_hw_breakpoint(void)
+{
+        unsigned int **task_bp_pinned;
+        int cpu, err_cpu;
+        int i;
+
+        for (i = 0; i < TYPE_MAX; i++)
+                nr_slots[i] = hw_breakpoint_slots(i);
+
+        for_each_possible_cpu(cpu) {
+                for (i = 0; i < TYPE_MAX; i++) {
+                        task_bp_pinned = &per_cpu(nr_task_bp_pinned[i], cpu);
+                        *task_bp_pinned = kzalloc(sizeof(int) * nr_slots[i],
+                                                  GFP_KERNEL);
+                        if (!*task_bp_pinned)
+                                goto err_alloc;
+                }
+        }
+
+        constraints_initialized = 1;
+
+        perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
+
+        return register_die_notifier(&hw_breakpoint_exceptions_nb);
+
+ err_alloc:
+        for_each_possible_cpu(err_cpu) {
+                if (err_cpu == cpu)
+                        break;
+                for (i = 0; i < TYPE_MAX; i++)
+                        kfree(per_cpu(nr_task_bp_pinned[i], cpu));
+        }
+
+        return -ENOMEM;
+}
+
+