1 files changed, 547 insertions, 0 deletions

diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
new file mode 100644
index 000000000000..55720dc6ec43
--- /dev/null
+++ b/drivers/oprofile/buffer_sync.c
@@ -0,0 +1,547 @@
+/**
+ * @file buffer_sync.c
+ *
+ * @remark Copyright 2002 OProfile authors
+ * @remark Read the file COPYING
+ *
+ * @author John Levon <levon@movementarian.org>
+ *
+ * This is the core of the buffer management. Each
+ * CPU buffer is processed and entered into the
+ * global event buffer. Such processing is necessary
+ * in several circumstances, mentioned below.
+ *
+ * The processing does the job of converting the
+ * transitory EIP value into a persistent dentry/offset
+ * value that the profiler can record at its leisure.
+ *
+ * See fs/dcookies.c for a description of the dentry/offset
+ * objects.
+ */
+
+#include <linux/mm.h>
+#include <linux/workqueue.h>
+#include <linux/notifier.h>
+#include <linux/dcookies.h>
+#include <linux/profile.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+ 
+#include "oprofile_stats.h"
+#include "event_buffer.h"
+#include "cpu_buffer.h"
+#include "buffer_sync.h"
+ 
+static LIST_HEAD(dying_tasks);
+static LIST_HEAD(dead_tasks);
+static cpumask_t marked_cpus = CPU_MASK_NONE;
+static DEFINE_SPINLOCK(task_mortuary);
+static void process_task_mortuary(void);
+
+
+/* Take ownership of the task struct and place it on the
+ * list for processing. Only after two full buffer syncs
+ * does the task eventually get freed, because by then
+ * we are sure we will not reference it again.
+ */
+static int task_free_notify(struct notifier_block * self, unsigned long val, void * data)
+{
+        struct task_struct * task = data;
+        spin_lock(&task_mortuary);
+        list_add(&task->tasks, &dying_tasks);
+        spin_unlock(&task_mortuary);
+        return NOTIFY_OK;
+}
+
+
+/* The task is on its way out. A sync of the buffer means we can catch
+ * any remaining samples for this task.
+ */
+static int task_exit_notify(struct notifier_block * self, unsigned long val, void * data)
+{
+        /* To avoid latency problems, we only process the current CPU,
+         * hoping that most samples for the task are on this CPU
+         */
+        sync_buffer(_smp_processor_id());
+        return 0;
+}
+
+
+/* The task is about to try a do_munmap(). We peek at what it's going to
+ * do, and if it's an executable region, process the samples first, so
+ * we don't lose any. This does not have to be exact, it's a QoI issue
+ * only.
+ */
+static int munmap_notify(struct notifier_block * self, unsigned long val, void * data)
+{
+        unsigned long addr = (unsigned long)data;
+        struct mm_struct * mm = current->mm;
+        struct vm_area_struct * mpnt;
+
+        down_read(&mm->mmap_sem);
+
+        mpnt = find_vma(mm, addr);
+        if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
+                up_read(&mm->mmap_sem);
+                /* To avoid latency problems, we only process the current CPU,
+                 * hoping that most samples for the task are on this CPU
+                 */
+                sync_buffer(_smp_processor_id());
+                return 0;
+        }
+
+        up_read(&mm->mmap_sem);
+        return 0;
+}
+
+ 
+/* We need to be told about new modules so we don't attribute to a previously
+ * loaded module, or drop the samples on the floor.
+ */
+static int module_load_notify(struct notifier_block * self, unsigned long val, void * data)
+{
+#ifdef CONFIG_MODULES
+        if (val != MODULE_STATE_COMING)
+                return 0;
+
+        /* FIXME: should we process all CPU buffers ? */
+        down(&buffer_sem);
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(MODULE_LOADED_CODE);
+        up(&buffer_sem);
+#endif
+        return 0;
+}
+
+ 
+static struct notifier_block task_free_nb = {
+        .notifier_call  = task_free_notify,
+};
+
+static struct notifier_block task_exit_nb = {
+        .notifier_call  = task_exit_notify,
+};
+
+static struct notifier_block munmap_nb = {
+        .notifier_call  = munmap_notify,
+};
+
+static struct notifier_block module_load_nb = {
+        .notifier_call = module_load_notify,
+};
+
+ 
+static void end_sync(void)
+{
+        end_cpu_work();
+        /* make sure we don't leak task structs */
+        process_task_mortuary();
+        process_task_mortuary();
+}
+
+
+int sync_start(void)
+{
+        int err;
+
+        start_cpu_work();
+
+        err = task_handoff_register(&task_free_nb);
+        if (err)
+                goto out1;
+        err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
+        if (err)
+                goto out2;
+        err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
+        if (err)
+                goto out3;
+        err = register_module_notifier(&module_load_nb);
+        if (err)
+                goto out4;
+
+out:
+        return err;
+out4:
+        profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
+out3:
+        profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
+out2:
+        task_handoff_unregister(&task_free_nb);
+out1:
+        end_sync();
+        goto out;
+}
+
+
+void sync_stop(void)
+{
+        unregister_module_notifier(&module_load_nb);
+        profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
+        profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
+        task_handoff_unregister(&task_free_nb);
+        end_sync();
+}
+
+ 
+/* Optimisation. We can manage without taking the dcookie sem
+ * because we cannot reach this code without at least one
+ * dcookie user still being registered (namely, the reader
+ * of the event buffer). */
+static inline unsigned long fast_get_dcookie(struct dentry * dentry,
+        struct vfsmount * vfsmnt)
+{
+        unsigned long cookie;
+ 
+        if (dentry->d_cookie)
+                return (unsigned long)dentry;
+        get_dcookie(dentry, vfsmnt, &cookie);
+        return cookie;
+}
+
+ 
+/* Look up the dcookie for the task's first VM_EXECUTABLE mapping,
+ * which corresponds loosely to "application name". This is
+ * not strictly necessary but allows oprofile to associate
+ * shared-library samples with particular applications
+ */
+static unsigned long get_exec_dcookie(struct mm_struct * mm)
+{
+        unsigned long cookie = 0;
+        struct vm_area_struct * vma;
+ 
+        if (!mm)
+                goto out;
+ 
+        for (vma = mm->mmap; vma; vma = vma->vm_next) {
+                if (!vma->vm_file)
+                        continue;
+                if (!(vma->vm_flags & VM_EXECUTABLE))
+                        continue;
+                cookie = fast_get_dcookie(vma->vm_file->f_dentry,
+                        vma->vm_file->f_vfsmnt);
+                break;
+        }
+
+out:
+        return cookie;
+}
+
+
+/* Convert the EIP value of a sample into a persistent dentry/offset
+ * pair that can then be added to the global event buffer. We make
+ * sure to do this lookup before a mm->mmap modification happens so
+ * we don't lose track.
+ */
+static unsigned long lookup_dcookie(struct mm_struct * mm, unsigned long addr, off_t * offset)
+{
+        unsigned long cookie = 0;
+        struct vm_area_struct * vma;
+
+        for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
+ 
+                if (!vma->vm_file)
+                        continue;
+
+                if (addr < vma->vm_start || addr >= vma->vm_end)
+                        continue;
+
+                cookie = fast_get_dcookie(vma->vm_file->f_dentry,
+                        vma->vm_file->f_vfsmnt);
+                *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr - vma->vm_start; 
+                break;
+        }
+
+        return cookie;
+}
+
+
+static unsigned long last_cookie = ~0UL;
+ 
+static void add_cpu_switch(int i)
+{
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(CPU_SWITCH_CODE);
+        add_event_entry(i);
+        last_cookie = ~0UL;
+}
+
+static void add_kernel_ctx_switch(unsigned int in_kernel)
+{
+        add_event_entry(ESCAPE_CODE);
+        if (in_kernel)
+                add_event_entry(KERNEL_ENTER_SWITCH_CODE); 
+        else
+                add_event_entry(KERNEL_EXIT_SWITCH_CODE); 
+}
+ 
+static void
+add_user_ctx_switch(struct task_struct const * task, unsigned long cookie)
+{
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(CTX_SWITCH_CODE); 
+        add_event_entry(task->pid);
+        add_event_entry(cookie);
+        /* Another code for daemon back-compat */
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(CTX_TGID_CODE);
+        add_event_entry(task->tgid);
+}
+
+ 
+static void add_cookie_switch(unsigned long cookie)
+{
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(COOKIE_SWITCH_CODE);
+        add_event_entry(cookie);
+}
+
+ 
+static void add_trace_begin(void)
+{
+        add_event_entry(ESCAPE_CODE);
+        add_event_entry(TRACE_BEGIN_CODE);
+}
+
+
+static void add_sample_entry(unsigned long offset, unsigned long event)
+{
+        add_event_entry(offset);
+        add_event_entry(event);
+}
+
+
+static int add_us_sample(struct mm_struct * mm, struct op_sample * s)
+{
+        unsigned long cookie;
+        off_t offset;
+ 
+        cookie = lookup_dcookie(mm, s->eip, &offset);
+ 
+        if (!cookie) {
+                atomic_inc(&oprofile_stats.sample_lost_no_mapping);
+                return 0;
+        }
+
+        if (cookie != last_cookie) {
+                add_cookie_switch(cookie);
+                last_cookie = cookie;
+        }
+
+        add_sample_entry(offset, s->event);
+
+        return 1;
+}
+
+ 
+/* Add a sample to the global event buffer. If possible the
+ * sample is converted into a persistent dentry/offset pair
+ * for later lookup from userspace.
+ */
+static int
+add_sample(struct mm_struct * mm, struct op_sample * s, int in_kernel)
+{
+        if (in_kernel) {
+                add_sample_entry(s->eip, s->event);
+                return 1;
+        } else if (mm) {
+                return add_us_sample(mm, s);
+        } else {
+                atomic_inc(&oprofile_stats.sample_lost_no_mm);
+        }
+        return 0;
+}
+ 
+
+static void release_mm(struct mm_struct * mm)
+{
+        if (!mm)
+                return;
+        up_read(&mm->mmap_sem);
+        mmput(mm);
+}
+
+
+static struct mm_struct * take_tasks_mm(struct task_struct * task)
+{
+        struct mm_struct * mm = get_task_mm(task);
+        if (mm)
+                down_read(&mm->mmap_sem);
+        return mm;
+}
+
+
+static inline int is_code(unsigned long val)
+{
+        return val == ESCAPE_CODE;
+}
+ 
+
+/* "acquire" as many cpu buffer slots as we can */
+static unsigned long get_slots(struct oprofile_cpu_buffer * b)
+{
+        unsigned long head = b->head_pos;
+        unsigned long tail = b->tail_pos;
+
+        /*
+         * Subtle. This resets the persistent last_task
+         * and in_kernel values used for switching notes.
+         * BUT, there is a small window between reading
+         * head_pos, and this call, that means samples
+         * can appear at the new head position, but not
+         * be prefixed with the notes for switching
+         * kernel mode or a task switch. This small hole
+         * can lead to mis-attribution or samples where
+         * we don't know if it's in the kernel or not,
+         * at the start of an event buffer.
+         */
+        cpu_buffer_reset(b);
+
+        if (head >= tail)
+                return head - tail;
+
+        return head + (b->buffer_size - tail);
+}
+
+
+static void increment_tail(struct oprofile_cpu_buffer * b)
+{
+        unsigned long new_tail = b->tail_pos + 1;
+
+        rmb();
+
+        if (new_tail < b->buffer_size)
+                b->tail_pos = new_tail;
+        else
+                b->tail_pos = 0;
+}
+
+
+/* Move tasks along towards death. Any tasks on dead_tasks
+ * will definitely have no remaining references in any
+ * CPU buffers at this point, because we use two lists,
+ * and to have reached the list, it must have gone through
+ * one full sync already.
+ */
+static void process_task_mortuary(void)
+{
+        struct list_head * pos;
+        struct list_head * pos2;
+        struct task_struct * task;
+
+        spin_lock(&task_mortuary);
+
+        list_for_each_safe(pos, pos2, &dead_tasks) {
+                task = list_entry(pos, struct task_struct, tasks);
+                list_del(&task->tasks);
+                free_task(task);
+        }
+
+        list_for_each_safe(pos, pos2, &dying_tasks) {
+                task = list_entry(pos, struct task_struct, tasks);
+                list_del(&task->tasks);
+                list_add_tail(&task->tasks, &dead_tasks);
+        }
+
+        spin_unlock(&task_mortuary);
+}
+
+
+static void mark_done(int cpu)
+{
+        int i;
+
+        cpu_set(cpu, marked_cpus);
+
+        for_each_online_cpu(i) {
+                if (!cpu_isset(i, marked_cpus))
+                        return;
+        }
+
+        /* All CPUs have been processed at least once,
+         * we can process the mortuary once
+         */
+        process_task_mortuary();
+
+        cpus_clear(marked_cpus);
+}
+
+
+/* FIXME: this is not sufficient if we implement syscall barrier backtrace
+ * traversal, the code switch to sb_sample_start at first kernel enter/exit
+ * switch so we need a fifth state and some special handling in sync_buffer()
+ */
+typedef enum {
+        sb_bt_ignore = -2,
+        sb_buffer_start,
+        sb_bt_start,
+        sb_sample_start,
+} sync_buffer_state;
+
+/* Sync one of the CPU's buffers into the global event buffer.
+ * Here we need to go through each batch of samples punctuated
+ * by context switch notes, taking the task's mmap_sem and doing
+ * lookup in task->mm->mmap to convert EIP into dcookie/offset
+ * value.
+ */
+void sync_buffer(int cpu)
+{
+        struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[cpu];
+        struct mm_struct *mm = NULL;
+        struct task_struct * new;
+        unsigned long cookie = 0;
+        int in_kernel = 1;
+        unsigned int i;
+        sync_buffer_state state = sb_buffer_start;
+        unsigned long available;
+
+        down(&buffer_sem);
+ 
+        add_cpu_switch(cpu);
+
+        /* Remember, only we can modify tail_pos */
+
+        available = get_slots(cpu_buf);
+
+        for (i = 0; i < available; ++i) {
+                struct op_sample * s = &cpu_buf->buffer[cpu_buf->tail_pos];
+ 
+                if (is_code(s->eip)) {
+                        if (s->event <= CPU_IS_KERNEL) {
+                                /* kernel/userspace switch */
+                                in_kernel = s->event;
+                                if (state == sb_buffer_start)
+                                        state = sb_sample_start;
+                                add_kernel_ctx_switch(s->event);
+                        } else if (s->event == CPU_TRACE_BEGIN) {
+                                state = sb_bt_start;
+                                add_trace_begin();
+                        } else {
+                                struct mm_struct * oldmm = mm;
+
+                                /* userspace context switch */
+                                new = (struct task_struct *)s->event;
+
+                                release_mm(oldmm);
+                                mm = take_tasks_mm(new);
+                                if (mm != oldmm)
+                                        cookie = get_exec_dcookie(mm);
+                                add_user_ctx_switch(new, cookie);
+                        }
+                } else {
+                        if (state >= sb_bt_start &&
+                            !add_sample(mm, s, in_kernel)) {
+                                if (state == sb_bt_start) {
+                                        state = sb_bt_ignore;
+                                        atomic_inc(&oprofile_stats.bt_lost_no_mapping);
+                                }
+                        }
+                }
+
+                increment_tail(cpu_buf);
+        }
+        release_mm(mm);
+
+        mark_done(cpu);
+
+        up(&buffer_sem);
+}