tools/perf/util/cloexec.c

   1 #include <sched.h>
   2 #include "util.h"
   3 #include "../perf.h"
   4 #include "cloexec.h"
   5 #include "asm/bug.h"
   6 #include "debug.h"
   7
   8 static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
   9
  10 static int perf_flag_probe(void)
  11 {
  12         /* use 'safest' configuration as used in perf_evsel__fallback() */
  13         struct perf_event_attr attr = {
  14                 .type = PERF_TYPE_SOFTWARE,
  15                 .config = PERF_COUNT_SW_CPU_CLOCK,
  16                 .exclude_kernel = 1,
  17         };
  18         int fd;
  19         int err;
  20         int cpu;
  21         pid_t pid = -1;
  22         char sbuf[STRERR_BUFSIZE];
  23
  24         cpu = sched_getcpu();
  25         if (cpu < 0)
  26                 cpu = 0;
  27
  28         while (1) {
  29                 /* check cloexec flag */
  30                 fd = sys_perf_event_open(&attr, pid, cpu, -1,
  31                                          PERF_FLAG_FD_CLOEXEC);
  32                 if (fd < 0 && pid == -1 && errno == EACCES) {
  33                         pid = 0;
  34                         continue;
  35                 }
  36                 break;
  37         }
  38         err = errno;
  39
  40         if (fd >= 0) {
  41                 close(fd);
  42                 return 1;
  43         }
  44
  45         WARN_ONCE(err != EINVAL && err != EBUSY,
  46                   "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
  47                   err, strerror_r(err, sbuf, sizeof(sbuf)));
  48
  49         /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
  50         fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
  51         err = errno;
  52
  53         if (WARN_ONCE(fd < 0 && err != EBUSY,
  54                       "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
  55                       err, strerror_r(err, sbuf, sizeof(sbuf))))
  56                 return -1;
  57
  58         close(fd);
  59
  60         return 0;
  61 }
  62
  63 unsigned long perf_event_open_cloexec_flag(void)
  64 {
  65         static bool probed;
  66
  67         if (!probed) {
  68                 if (perf_flag_probe() <= 0)
  69                         flag = 0;
  70                 probed = true;
  71         }
  72
  73         return flag;
  74 }