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