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 EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
  13
  14 static char *perf_trace_buf[4];
  15
  16 /*
  17  * Force it to be aligned to unsigned long to avoid misaligned accesses
  18  * suprises
  19  */
  20 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
  21         perf_trace_t;
  22
  23 /* Count the events in use (per event id, not per instance) */
  24 static int      total_ref_count;
  25
  26 static int perf_trace_event_init(struct ftrace_event_call *tp_event,
  27                                  struct perf_event *p_event)
  28 {
  29         struct hlist_head *list;
  30         int ret = -ENOMEM;
  31         int cpu;
  32
  33         p_event->tp_event = tp_event;
  34         if (tp_event->perf_refcount++ > 0)
  35                 return 0;
  36
  37         list = alloc_percpu(struct hlist_head);
  38         if (!list)
  39                 goto fail;
  40
  41         for_each_possible_cpu(cpu)
  42                 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
  43
  44         tp_event->perf_events = list;
  45
  46         if (!total_ref_count) {
  47                 char *buf;
  48                 int i;
  49
  50                 for (i = 0; i < 4; i++) {
  51                         buf = (char *)alloc_percpu(perf_trace_t);
  52                         if (!buf)
  53                                 goto fail;
  54
  55                         perf_trace_buf[i] = buf;
  56                 }
  57         }
  58
  59         ret = tp_event->perf_event_enable(tp_event);
  60         if (ret)
  61                 goto fail;
  62
  63         total_ref_count++;
  64         return 0;
  65
  66 fail:
  67         if (!total_ref_count) {
  68                 int i;
  69
  70                 for (i = 0; i < 4; i++) {
  71                         free_percpu(perf_trace_buf[i]);
  72                         perf_trace_buf[i] = NULL;
  73                 }
  74         }
  75
  76         if (!--tp_event->perf_refcount) {
  77                 free_percpu(tp_event->perf_events);
  78                 tp_event->perf_events = NULL;
  79         }
  80
  81         return ret;
  82 }
  83
  84 int perf_trace_init(struct perf_event *p_event)
  85 {
  86         struct ftrace_event_call *tp_event;
  87         int event_id = p_event->attr.config;
  88         int ret = -EINVAL;
  89
  90         mutex_lock(&event_mutex);
  91         list_for_each_entry(tp_event, &ftrace_events, list) {
  92                 if (tp_event->id == event_id && tp_event->perf_event_enable &&
  93                     try_module_get(tp_event->mod)) {
  94                         ret = perf_trace_event_init(tp_event, p_event);
  95                         break;
  96                 }
  97         }
  98         mutex_unlock(&event_mutex);
  99
 100         return ret;
 101 }
 102
 103 int perf_trace_enable(struct perf_event *p_event)
 104 {
 105         struct ftrace_event_call *tp_event = p_event->tp_event;
 106         struct hlist_head *list;
 107
 108         list = tp_event->perf_events;
 109         if (WARN_ON_ONCE(!list))
 110                 return -EINVAL;
 111
 112         list = per_cpu_ptr(list, smp_processor_id());
 113         hlist_add_head_rcu(&p_event->hlist_entry, list);
 114
 115         return 0;
 116 }
 117
 118 void perf_trace_disable(struct perf_event *p_event)
 119 {
 120         hlist_del_rcu(&p_event->hlist_entry);
 121 }
 122
 123 void perf_trace_destroy(struct perf_event *p_event)
 124 {
 125         struct ftrace_event_call *tp_event = p_event->tp_event;
 126         int i;
 127
 128         if (--tp_event->perf_refcount > 0)
 129                 return;
 130
 131         tp_event->perf_event_disable(tp_event);
 132
 133         free_percpu(tp_event->perf_events);
 134         tp_event->perf_events = NULL;
 135
 136         if (!--total_ref_count) {
 137                 for (i = 0; i < 4; i++) {
 138                         free_percpu(perf_trace_buf[i]);
 139                         perf_trace_buf[i] = NULL;
 140                 }
 141         }
 142 }
 143
 144 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 145                                        struct pt_regs *regs, int *rctxp)
 146 {
 147         struct trace_entry *entry;
 148         char *raw_data;
 149         int pc;
 150
 151         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
 152
 153         pc = preempt_count();
 154
 155         *rctxp = perf_swevent_get_recursion_context();
 156         if (*rctxp < 0)
 157                 return NULL;
 158
 159         raw_data = per_cpu_ptr(perf_trace_buf[*rctxp], smp_processor_id());
 160
 161         /* zero the dead bytes from align to not leak stack to user */
 162         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 163
 164         entry = (struct trace_entry *)raw_data;
 165         tracing_generic_entry_update(entry, regs->flags, pc);
 166         entry->type = type;
 167
 168         return raw_data;
 169 }
 170 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);