SAFE public projects git trees. - safe/jmp/linux-2.6/blob - kernel/trace/trace_event_perf.c

   1 /*
   2  * trace event based perf event profiling/tracing
   3  *
   4  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
   5  * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kprobes.h>
  10 #include "trace.h"
  11
  12 DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
  13 EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);
  14
  15 static char *perf_trace_buf;
  16 static char *perf_trace_buf_nmi;
  17
  18 typedef typeof(char [PERF_MAX_TRACE_SIZE]) perf_trace_t ;
  19
  20 /* Count the events in use (per event id, not per instance) */
  21 static int      total_ref_count;
  22
  23 static int perf_trace_event_enable(struct ftrace_event_call *event)
  24 {
  25         char *buf;
  26         int ret = -ENOMEM;
  27
  28         if (event->perf_refcount++ > 0)
  29                 return 0;
  30
  31         if (!total_ref_count) {
  32                 buf = (char *)alloc_percpu(perf_trace_t);
  33                 if (!buf)
  34                         goto fail_buf;
  35
  36                 rcu_assign_pointer(perf_trace_buf, buf);
  37
  38                 buf = (char *)alloc_percpu(perf_trace_t);
  39                 if (!buf)
  40                         goto fail_buf_nmi;
  41
  42                 rcu_assign_pointer(perf_trace_buf_nmi, buf);
  43         }
  44
  45         ret = event->perf_event_enable(event);
  46         if (!ret) {
  47                 total_ref_count++;
  48                 return 0;
  49         }
  50
  51 fail_buf_nmi:
  52         if (!total_ref_count) {
  53                 free_percpu(perf_trace_buf_nmi);
  54                 free_percpu(perf_trace_buf);
  55                 perf_trace_buf_nmi = NULL;
  56                 perf_trace_buf = NULL;
  57         }
  58 fail_buf:
  59         event->perf_refcount--;
  60
  61         return ret;
  62 }
  63
  64 int perf_trace_enable(int event_id)
  65 {
  66         struct ftrace_event_call *event;
  67         int ret = -EINVAL;
  68
  69         mutex_lock(&event_mutex);
  70         list_for_each_entry(event, &ftrace_events, list) {
  71                 if (event->id == event_id && event->perf_event_enable &&
  72                     try_module_get(event->mod)) {
  73                         ret = perf_trace_event_enable(event);
  74                         break;
  75                 }
  76         }
  77         mutex_unlock(&event_mutex);
  78
  79         return ret;
  80 }
  81
  82 static void perf_trace_event_disable(struct ftrace_event_call *event)
  83 {
  84         char *buf, *nmi_buf;
  85
  86         if (--event->perf_refcount > 0)
  87                 return;
  88
  89         event->perf_event_disable(event);
  90
  91         if (!--total_ref_count) {
  92                 buf = perf_trace_buf;
  93                 rcu_assign_pointer(perf_trace_buf, NULL);
  94
  95                 nmi_buf = perf_trace_buf_nmi;
  96                 rcu_assign_pointer(perf_trace_buf_nmi, NULL);
  97
  98                 /*
  99                  * Ensure every events in profiling have finished before
 100                  * releasing the buffers
 101                  */
 102                 synchronize_sched();
 103
 104                 free_percpu(buf);
 105                 free_percpu(nmi_buf);
 106         }
 107 }
 108
 109 void perf_trace_disable(int event_id)
 110 {
 111         struct ftrace_event_call *event;
 112
 113         mutex_lock(&event_mutex);
 114         list_for_each_entry(event, &ftrace_events, list) {
 115                 if (event->id == event_id) {
 116                         perf_trace_event_disable(event);
 117                         module_put(event->mod);
 118                         break;
 119                 }
 120         }
 121         mutex_unlock(&event_mutex);
 122 }
 123
 124 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 125                                        int *rctxp, unsigned long *irq_flags)
 126 {
 127         struct trace_entry *entry;
 128         char *trace_buf, *raw_data;
 129         int pc, cpu;
 130
 131         pc = preempt_count();
 132
 133         /* Protect the per cpu buffer, begin the rcu read side */
 134         local_irq_save(*irq_flags);
 135
 136         *rctxp = perf_swevent_get_recursion_context();
 137         if (*rctxp < 0)
 138                 goto err_recursion;
 139
 140         cpu = smp_processor_id();
 141
 142         if (in_nmi())
 143                 trace_buf = rcu_dereference(perf_trace_buf_nmi);
 144         else
 145                 trace_buf = rcu_dereference(perf_trace_buf);
 146
 147         if (!trace_buf)
 148                 goto err;
 149
 150         raw_data = per_cpu_ptr(trace_buf, cpu);
 151
 152         /* zero the dead bytes from align to not leak stack to user */
 153         *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
 154
 155         entry = (struct trace_entry *)raw_data;
 156         tracing_generic_entry_update(entry, *irq_flags, pc);
 157         entry->type = type;
 158
 159         return raw_data;
 160 err:
 161         perf_swevent_put_recursion_context(*rctxp);
 162 err_recursion:
 163         local_irq_restore(*irq_flags);
 164         return NULL;
 165 }
 166 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);