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#include <unistd.h>
  8#include <asm/unistd.h>
  9#include <sys/syscall.h>
 10
 11static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
 12
 13int __weak sched_getcpu(void)
 14{
 15#ifdef __NR_getcpu
 16	unsigned cpu;
 17	int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
 18	if (!err)
 19		return cpu;
 20#else
 21	errno = ENOSYS;
 22#endif
 23	return -1;
 24}
 25
 26static int perf_flag_probe(void)
 27{
 28	/* use 'safest' configuration as used in perf_evsel__fallback() */
 29	struct perf_event_attr attr = {
 30		.type = PERF_TYPE_SOFTWARE,
 31		.config = PERF_COUNT_SW_CPU_CLOCK,
 32		.exclude_kernel = 1,
 33	};
 34	int fd;
 35	int err;
 36	int cpu;
 37	pid_t pid = -1;
 38	char sbuf[STRERR_BUFSIZE];
 39
 40	cpu = sched_getcpu();
 41	if (cpu < 0)
 42		cpu = 0;
 43
 44	/*
 45	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
 46	 * changes.
 47	 */
 48	while (1) {
 49		/* check cloexec flag */
 50		fd = sys_perf_event_open(&attr, pid, cpu, -1,
 51					 PERF_FLAG_FD_CLOEXEC);
 52		if (fd < 0 && pid == -1 && errno == EACCES) {
 53			pid = 0;
 54			continue;
 55		}
 56		break;
 57	}
 58	err = errno;
 59
 60	if (fd >= 0) {
 61		close(fd);
 62		return 1;
 63	}
 64
 65	WARN_ONCE(err != EINVAL && err != EBUSY,
 66		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 67		  err, str_error_r(err, sbuf, sizeof(sbuf)));
 68
 69	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
 70	while (1) {
 71		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
 72		if (fd < 0 && pid == -1 && errno == EACCES) {
 73			pid = 0;
 74			continue;
 75		}
 76		break;
 77	}
 78	err = errno;
 79
 80	if (fd >= 0)
 81		close(fd);
 82
 83	if (WARN_ONCE(fd < 0 && err != EBUSY,
 84		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 85		      err, str_error_r(err, sbuf, sizeof(sbuf))))
 86		return -1;
 87
 88	return 0;
 89}
 90
 91unsigned long perf_event_open_cloexec_flag(void)
 92{
 93	static bool probed;
 94
 95	if (!probed) {
 96		if (perf_flag_probe() <= 0)
 97			flag = 0;
 98		probed = true;
 99	}
100
101	return flag;
102}