tools/perf/arch/x86/util/tsc.c

   1 #include <stdbool.h>
   2 #include <errno.h>
   3
   4 #include <linux/perf_event.h>
   5
   6 #include "../../perf.h"
   7 #include <linux/types.h>
   8 #include "../../util/debug.h"
   9 #include "../../util/tsc.h"
  10
  11 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  12                              struct perf_tsc_conversion *tc)
  13 {
  14         bool cap_user_time_zero;
  15         u32 seq;
  16         int i = 0;
  17
  18         while (1) {
  19                 seq = pc->lock;
  20                 rmb();
  21                 tc->time_mult = pc->time_mult;
  22                 tc->time_shift = pc->time_shift;
  23                 tc->time_zero = pc->time_zero;
  24                 cap_user_time_zero = pc->cap_user_time_zero;
  25                 rmb();
  26                 if (pc->lock == seq && !(seq & 1))
  27                         break;
  28                 if (++i > 10000) {
  29                         pr_debug("failed to get perf_event_mmap_page lock\n");
  30                         return -EINVAL;
  31                 }
  32         }
  33
  34         if (!cap_user_time_zero)
  35                 return -EOPNOTSUPP;
  36
  37         return 0;
  38 }
  39
  40 u64 rdtsc(void)
  41 {
  42         unsigned int low, high;
  43
  44         asm volatile("rdtsc" : "=a" (low), "=d" (high));
  45
  46         return low | ((u64)high) << 32;
  47 }
  48
  49 int perf_event__synth_time_conv(const struct perf_event_mmap_page *pc,
  50                                 struct perf_tool *tool,
  51                                 perf_event__handler_t process,
  52                                 struct machine *machine)
  53 {
  54         union perf_event event = {
  55                 .time_conv = {
  56                         .header = {
  57                                 .type = PERF_RECORD_TIME_CONV,
  58                                 .size = sizeof(struct time_conv_event),
  59                         },
  60                 },
  61         };
  62         struct perf_tsc_conversion tc;
  63         int err;
  64
  65         err = perf_read_tsc_conversion(pc, &tc);
  66         if (err == -EOPNOTSUPP)
  67                 return 0;
  68         if (err)
  69                 return err;
  70
  71         pr_debug2("Synthesizing TSC conversion information\n");
  72
  73         event.time_conv.time_mult  = tc.time_mult;
  74         event.time_conv.time_shift = tc.time_shift;
  75         event.time_conv.time_zero  = tc.time_zero;
  76
  77         return process(tool, &event, NULL, machine);
  78 }