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         if (tp_event->class->reg)
  60                 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
  61         else
  62                 ret = tracepoint_probe_register(tp_event->name,
  63                                                 tp_event->class->perf_probe,
  64                                                 tp_event);
  65
  66         if (ret)
  67                 goto fail;
  68
  69         total_ref_count++;
  70         return 0;
  71
  72 fail:
  73         if (!total_ref_count) {
  74                 int i;
  75
  76                 for (i = 0; i < 4; i++) {
  77                         free_percpu(perf_trace_buf[i]);
  78                         perf_trace_buf[i] = NULL;
  79                 }
  80         }
  81
  82         if (!--tp_event->perf_refcount) {
  83                 free_percpu(tp_event->perf_events);
  84                 tp_event->perf_events = NULL;
  85         }
  86
  87         return ret;
  88 }
  89
  90 int perf_trace_init(struct perf_event *p_event)
  91 {
  92         struct ftrace_event_call *tp_event;
  93         int event_id = p_event->attr.config;
  94         int ret = -EINVAL;
  95
  96         mutex_lock(&event_mutex);
  97         list_for_each_entry(tp_event, &ftrace_events, list) {
  98                 if (tp_event->event.type == event_id &&
  99                     tp_event->class &&
 100                     (tp_event->class->perf_probe ||
 101                      tp_event->class->reg) &&
 102                     try_module_get(tp_event->mod)) {
 103                         ret = perf_trace_event_init(tp_event, p_event);
 104                         break;
 105                 }
 106         }
 107         mutex_unlock(&event_mutex);
 108
 109         return ret;
 110 }
 111
 112 int perf_trace_enable(struct perf_event *p_event)
 113 {
 114         struct ftrace_event_call *tp_event = p_event->tp_event;
 115         struct hlist_head *list;
 116
 117         list = tp_event->perf_events;
 118         if (WARN_ON_ONCE(!list))
 119                 return -EINVAL;
 120
 121         list = this_cpu_ptr(list);
 122         hlist_add_head_rcu(&p_event->hlist_entry, list);
 123
 124         return 0;
 125 }
 126
 127 void perf_trace_disable(struct perf_event *p_event)
 128 {
 129         hlist_del_rcu(&p_event->hlist_entry);
 130 }
 131
 132 void perf_trace_destroy(struct perf_event *p_event)
 133 {
 134         struct ftrace_event_call *tp_event = p_event->tp_event;
 135         int i;
 136
 137         mutex_lock(&event_mutex);
 138         if (--tp_event->perf_refcount > 0)
 139                 goto out;
 140
 141         if (tp_event->class->reg)
 142                 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
 143         else
 144                 tracepoint_probe_unregister(tp_event->name,
 145                                             tp_event->class->perf_probe,
 146                                             tp_event);
 147
 148         /*
 149          * Ensure our callback won't be called anymore. See
 150          * tracepoint_probe_unregister() and __DO_TRACE().
 151          */
 152         synchronize_sched();
 153
 154         free_percpu(tp_event->perf_events);
 155         tp_event->perf_events = NULL;
 156
 157         if (!--total_ref_count) {
 158                 for (i = 0; i < 4; i++) {
 159                         free_percpu(perf_trace_buf[i]);
 160                         perf_trace_buf[i] = NULL;
 161                 }
 162         }
 163 out:
 164         mutex_unlock(&event_mutex);
 165 }
 166
 167 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 168                                        struct pt_regs *regs, int *rctxp)
 169 {
 170         struct trace_entry *entry;
 171         unsigned long flags;
 172         char *raw_data;
 173         int pc;
 174
 175         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
 176
 177         pc = preempt_count();
 178
 179         *rctxp = perf_swevent_get_recursion_context();
 180         if (*rctxp < 0)
 181                 return NULL;
 182
 183         raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
 184
 185         /* zero the dead bytes from align to not leak stack to user */
 186         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 187
 188         entry = (struct trace_entry *)raw_data;
 189         local_save_flags(flags);
 190         tracing_generic_entry_update(entry, flags, pc);
 191         entry->type = type;
 192
 193         return raw_data;
 194 }
 195 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);