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 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
  13
  14 /*
  15  * Force it to be aligned to unsigned long to avoid misaligned accesses
  16  * suprises
  17  */
  18 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
  19         perf_trace_t;
  20
  21 /* Count the events in use (per event id, not per instance) */
  22 static int      total_ref_count;
  23
  24 static int perf_trace_event_init(struct ftrace_event_call *tp_event,
  25                                  struct perf_event *p_event)
  26 {
  27         struct hlist_head __percpu *list;
  28         int ret = -ENOMEM;
  29         int cpu;
  30
  31         p_event->tp_event = tp_event;
  32         if (tp_event->perf_refcount++ > 0)
  33                 return 0;
  34
  35         list = alloc_percpu(struct hlist_head);
  36         if (!list)
  37                 goto fail;
  38
  39         for_each_possible_cpu(cpu)
  40                 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
  41
  42         tp_event->perf_events = list;
  43
  44         if (!total_ref_count) {
  45                 char __percpu *buf;
  46                 int i;
  47
  48                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
  49                         buf = (char __percpu *)alloc_percpu(perf_trace_t);
  50                         if (!buf)
  51                                 goto fail;
  52
  53                         perf_trace_buf[i] = buf;
  54                 }
  55         }
  56
  57         ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
  58         if (ret)
  59                 goto fail;
  60
  61         total_ref_count++;
  62         return 0;
  63
  64 fail:
  65         if (!total_ref_count) {
  66                 int i;
  67
  68                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
  69                         free_percpu(perf_trace_buf[i]);
  70                         perf_trace_buf[i] = NULL;
  71                 }
  72         }
  73
  74         if (!--tp_event->perf_refcount) {
  75                 free_percpu(tp_event->perf_events);
  76                 tp_event->perf_events = NULL;
  77         }
  78
  79         return ret;
  80 }
  81
  82 int perf_trace_init(struct perf_event *p_event)
  83 {
  84         struct ftrace_event_call *tp_event;
  85         int event_id = p_event->attr.config;
  86         int ret = -EINVAL;
  87
  88         mutex_lock(&event_mutex);
  89         list_for_each_entry(tp_event, &ftrace_events, list) {
  90                 if (tp_event->event.type == event_id &&
  91                     tp_event->class && tp_event->class->reg &&
  92                     try_module_get(tp_event->mod)) {
  93                         ret = perf_trace_event_init(tp_event, p_event);
  94                         break;
  95                 }
  96         }
  97         mutex_unlock(&event_mutex);
  98
  99         return ret;
 100 }
 101
 102 int perf_trace_enable(struct perf_event *p_event)
 103 {
 104         struct ftrace_event_call *tp_event = p_event->tp_event;
 105         struct hlist_head __percpu *pcpu_list;
 106         struct hlist_head *list;
 107
 108         pcpu_list = tp_event->perf_events;
 109         if (WARN_ON_ONCE(!pcpu_list))
 110                 return -EINVAL;
 111
 112         list = this_cpu_ptr(pcpu_list);
 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         mutex_lock(&event_mutex);
 129         if (--tp_event->perf_refcount > 0)
 130                 goto out;
 131
 132         tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
 133
 134         /*
 135          * Ensure our callback won't be called anymore. The buffers
 136          * will be freed after that.
 137          */
 138         tracepoint_synchronize_unregister();
 139
 140         free_percpu(tp_event->perf_events);
 141         tp_event->perf_events = NULL;
 142
 143         if (!--total_ref_count) {
 144                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
 145                         free_percpu(perf_trace_buf[i]);
 146                         perf_trace_buf[i] = NULL;
 147                 }
 148         }
 149 out:
 150         mutex_unlock(&event_mutex);
 151 }
 152
 153 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 154                                        struct pt_regs *regs, int *rctxp)
 155 {
 156         struct trace_entry *entry;
 157         unsigned long flags;
 158         char *raw_data;
 159         int pc;
 160
 161         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
 162
 163         pc = preempt_count();
 164
 165         *rctxp = perf_swevent_get_recursion_context();
 166         if (*rctxp < 0)
 167                 return NULL;
 168
 169         raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
 170
 171         /* zero the dead bytes from align to not leak stack to user */
 172         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 173
 174         entry = (struct trace_entry *)raw_data;
 175         local_save_flags(flags);
 176         tracing_generic_entry_update(entry, flags, pc);
 177         entry->type = type;
 178
 179         return raw_data;
 180 }
 181 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);