LXR linux/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
  11int 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
  40u64 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
  49int 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        if (!pc)
  66                return 0;
  67        err = perf_read_tsc_conversion(pc, &tc);
  68        if (err == -EOPNOTSUPP)
  69                return 0;
  70        if (err)
  71                return err;
  72
  73        pr_debug2("Synthesizing TSC conversion information\n");
  74
  75        event.time_conv.time_mult  = tc.time_mult;
  76        event.time_conv.time_shift = tc.time_shift;
  77        event.time_conv.time_zero  = tc.time_zero;
  78
  79        return process(tool, &event, NULL, machine);
  80}
  81