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

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <stdbool.h>
   3 #include <errno.h>
   4
   5 #include <linux/stddef.h>
   6 #include <linux/perf_event.h>
   7
   8 #include "../../perf.h"
   9 #include <linux/types.h>
  10 #include "../../util/debug.h"
  11 #include "../../util/tsc.h"
  12
  13 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  14                              struct perf_tsc_conversion *tc)
  15 {
  16         bool cap_user_time_zero;
  17         u32 seq;
  18         int i = 0;
  19
  20         while (1) {
  21                 seq = pc->lock;
  22                 rmb();
  23                 tc->time_mult = pc->time_mult;
  24                 tc->time_shift = pc->time_shift;
  25                 tc->time_zero = pc->time_zero;
  26                 cap_user_time_zero = pc->cap_user_time_zero;
  27                 rmb();
  28                 if (pc->lock == seq && !(seq & 1))
  29                         break;
  30                 if (++i > 10000) {
  31                         pr_debug("failed to get perf_event_mmap_page lock\n");
  32                         return -EINVAL;
  33                 }
  34         }
  35
  36         if (!cap_user_time_zero)
  37                 return -EOPNOTSUPP;
  38
  39         return 0;
  40 }
  41
  42 u64 rdtsc(void)
  43 {
  44         unsigned int low, high;
  45
  46         asm volatile("rdtsc" : "=a" (low), "=d" (high));
  47
  48         return low | ((u64)high) << 32;
  49 }
  50
  51 int perf_event__synth_time_conv(const struct perf_event_mmap_page *pc,
  52                                 struct perf_tool *tool,
  53                                 perf_event__handler_t process,
  54                                 struct machine *machine)
  55 {
  56         union perf_event event = {
  57                 .time_conv = {
  58                         .header = {
  59                                 .type = PERF_RECORD_TIME_CONV,
  60                                 .size = sizeof(struct time_conv_event),
  61                         },
  62                 },
  63         };
  64         struct perf_tsc_conversion tc;
  65         int err;
  66
  67         if (!pc)
  68                 return 0;
  69         err = perf_read_tsc_conversion(pc, &tc);
  70         if (err == -EOPNOTSUPP)
  71                 return 0;
  72         if (err)
  73                 return err;
  74
  75         pr_debug2("Synthesizing TSC conversion information\n");
  76
  77         event.time_conv.time_mult  = tc.time_mult;
  78         event.time_conv.time_shift = tc.time_shift;
  79         event.time_conv.time_zero  = tc.time_zero;
  80
  81         return process(tool, &event, NULL, machine);
  82 }