tools/perf/util/cloexec.c

   1 #include "util.h"
   2 #include "../perf.h"
   3 #include "cloexec.h"
   4 #include "asm/bug.h"
   5
   6 static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
   7
   8 static int perf_flag_probe(void)
   9 {
  10         /* use 'safest' configuration as used in perf_evsel__fallback() */
  11         struct perf_event_attr attr = {
  12                 .type = PERF_COUNT_SW_CPU_CLOCK,
  13                 .config = PERF_COUNT_SW_CPU_CLOCK,
  14         };
  15         int fd;
  16         int err;
  17
  18         /* check cloexec flag */
  19         fd = sys_perf_event_open(&attr, 0, -1, -1,
  20                                  PERF_FLAG_FD_CLOEXEC);
  21         err = errno;
  22
  23         if (fd >= 0) {
  24                 close(fd);
  25                 return 1;
  26         }
  27
  28         WARN_ONCE(err != EINVAL,
  29                   "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
  30                   err, strerror(err));
  31
  32         /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
  33         fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
  34         err = errno;
  35
  36         if (WARN_ONCE(fd < 0,
  37                       "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
  38                       err, strerror(err)))
  39                 return -1;
  40
  41         close(fd);
  42
  43         return 0;
  44 }
  45
  46 unsigned long perf_event_open_cloexec_flag(void)
  47 {
  48         static bool probed;
  49
  50         if (!probed) {
  51                 if (perf_flag_probe() <= 0)
  52                         flag = 0;
  53                 probed = true;
  54         }
  55
  56         return flag;
  57 }