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 #include "tsc.h"
  11
  12 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  13                              struct perf_tsc_conversion *tc)
  14 {
  15         bool cap_user_time_zero;
  16         u32 seq;
  17         int i = 0;
  18
  19         while (1) {
  20                 seq = pc->lock;
  21                 rmb();
  22                 tc->time_mult = pc->time_mult;
  23                 tc->time_shift = pc->time_shift;
  24                 tc->time_zero = pc->time_zero;
  25                 cap_user_time_zero = pc->cap_user_time_zero;
  26                 rmb();
  27                 if (pc->lock == seq && !(seq & 1))
  28                         break;
  29                 if (++i > 10000) {
  30                         pr_debug("failed to get perf_event_mmap_page lock\n");
  31                         return -EINVAL;
  32                 }
  33         }
  34
  35         if (!cap_user_time_zero)
  36                 return -EOPNOTSUPP;
  37
  38         return 0;
  39 }
  40
  41 u64 rdtsc(void)
  42 {
  43         unsigned int low, high;
  44
  45         asm volatile("rdtsc" : "=a" (low), "=d" (high));
  46
  47         return low | ((u64)high) << 32;
  48 }