kernel/trace/trace_event_profile.c

   1 /*
   2  * trace event based perf counter profiling
   3  *
   4  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
   5  *
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kprobes.h>
  10 #include "trace.h"
  11
  12
  13 static char *perf_trace_buf;
  14 static char *perf_trace_buf_nmi;
  15
  16 typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) perf_trace_t ;
  17
  18 /* Count the events in use (per event id, not per instance) */
  19 static int      total_profile_count;
  20
  21 static int ftrace_profile_enable_event(struct ftrace_event_call *event)
  22 {
  23         char *buf;
  24         int ret = -ENOMEM;
  25
  26         if (event->profile_count++ > 0)
  27                 return 0;
  28
  29         if (!total_profile_count) {
  30                 buf = (char *)alloc_percpu(perf_trace_t);
  31                 if (!buf)
  32                         goto fail_buf;
  33
  34                 rcu_assign_pointer(perf_trace_buf, buf);
  35
  36                 buf = (char *)alloc_percpu(perf_trace_t);
  37                 if (!buf)
  38                         goto fail_buf_nmi;
  39
  40                 rcu_assign_pointer(perf_trace_buf_nmi, buf);
  41         }
  42
  43         ret = event->profile_enable(event);
  44         if (!ret) {
  45                 total_profile_count++;
  46                 return 0;
  47         }
  48
  49 fail_buf_nmi:
  50         if (!total_profile_count) {
  51                 free_percpu(perf_trace_buf_nmi);
  52                 free_percpu(perf_trace_buf);
  53                 perf_trace_buf_nmi = NULL;
  54                 perf_trace_buf = NULL;
  55         }
  56 fail_buf:
  57         event->profile_count--;
  58
  59         return ret;
  60 }
  61
  62 int ftrace_profile_enable(int event_id)
  63 {
  64         struct ftrace_event_call *event;
  65         int ret = -EINVAL;
  66
  67         mutex_lock(&event_mutex);
  68         list_for_each_entry(event, &ftrace_events, list) {
  69                 if (event->id == event_id && event->profile_enable &&
  70                     try_module_get(event->mod)) {
  71                         ret = ftrace_profile_enable_event(event);
  72                         break;
  73                 }
  74         }
  75         mutex_unlock(&event_mutex);
  76
  77         return ret;
  78 }
  79
  80 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
  81 {
  82         char *buf, *nmi_buf;
  83
  84         if (--event->profile_count > 0)
  85                 return;
  86
  87         event->profile_disable(event);
  88
  89         if (!--total_profile_count) {
  90                 buf = perf_trace_buf;
  91                 rcu_assign_pointer(perf_trace_buf, NULL);
  92
  93                 nmi_buf = perf_trace_buf_nmi;
  94                 rcu_assign_pointer(perf_trace_buf_nmi, NULL);
  95
  96                 /*
  97                  * Ensure every events in profiling have finished before
  98                  * releasing the buffers
  99                  */
 100                 synchronize_sched();
 101
 102                 free_percpu(buf);
 103                 free_percpu(nmi_buf);
 104         }
 105 }
 106
 107 void ftrace_profile_disable(int event_id)
 108 {
 109         struct ftrace_event_call *event;
 110
 111         mutex_lock(&event_mutex);
 112         list_for_each_entry(event, &ftrace_events, list) {
 113                 if (event->id == event_id) {
 114                         ftrace_profile_disable_event(event);
 115                         module_put(event->mod);
 116                         break;
 117                 }
 118         }
 119         mutex_unlock(&event_mutex);
 120 }
 121
 122 __kprobes void *ftrace_perf_buf_prepare(int size, unsigned short type,
 123                                         int *rctxp, unsigned long *irq_flags)
 124 {
 125         struct trace_entry *entry;
 126         char *trace_buf, *raw_data;
 127         int pc, cpu;
 128
 129         pc = preempt_count();
 130
 131         /* Protect the per cpu buffer, begin the rcu read side */
 132         local_irq_save(*irq_flags);
 133
 134         *rctxp = perf_swevent_get_recursion_context();
 135         if (*rctxp < 0)
 136                 goto err_recursion;
 137
 138         cpu = smp_processor_id();
 139
 140         if (in_nmi())
 141                 trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
 142         else
 143                 trace_buf = rcu_dereference_sched(perf_trace_buf);
 144
 145         if (!trace_buf)
 146                 goto err;
 147
 148         raw_data = per_cpu_ptr(trace_buf, cpu);
 149
 150         /* zero the dead bytes from align to not leak stack to user */
 151         *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
 152
 153         entry = (struct trace_entry *)raw_data;
 154         tracing_generic_entry_update(entry, *irq_flags, pc);
 155         entry->type = type;
 156
 157         return raw_data;
 158 err:
 159         perf_swevent_put_recursion_context(*rctxp);
 160 err_recursion:
 161         local_irq_restore(*irq_flags);
 162         return NULL;
 163 }
 164 EXPORT_SYMBOL_GPL(ftrace_perf_buf_prepare);