1// SPDX-License-Identifier: GPL-2.0
 2#include <errno.h>
 3#include <sched.h>
 4#include "util.h" // for sched_getcpu()
 5#include "../perf-sys.h"
 6#include "cloexec.h"
 7#include "event.h"
 8#include "asm/bug.h"
 9#include "debug.h"
10#include <unistd.h>
 
11#include <sys/syscall.h>
12#include <linux/string.h>
13
14static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
15
 
 
 
 
 
 
 
 
 
 
 
 
 
16static int perf_flag_probe(void)
17{
18	/* use 'safest' configuration as used in evsel__fallback() */
19	struct perf_event_attr attr = {
20		.type = PERF_TYPE_SOFTWARE,
21		.config = PERF_COUNT_SW_CPU_CLOCK,
22		.exclude_kernel = 1,
23	};
24	int fd;
25	int err;
26	int cpu;
27	pid_t pid = -1;
28	char sbuf[STRERR_BUFSIZE];
29
30	cpu = sched_getcpu();
31	if (cpu < 0)
32		cpu = 0;
33
34	/*
35	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
36	 * changes.
37	 */
38	while (1) {
39		/* check cloexec flag */
40		fd = sys_perf_event_open(&attr, pid, cpu, -1,
41					 PERF_FLAG_FD_CLOEXEC);
42		if (fd < 0 && pid == -1 && errno == EACCES) {
43			pid = 0;
44			continue;
45		}
46		break;
47	}
48	err = errno;
49
50	if (fd >= 0) {
51		close(fd);
52		return 1;
53	}
54
55	WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
56		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
57		  err, str_error_r(err, sbuf, sizeof(sbuf)));
58
59	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
60	while (1) {
61		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
62		if (fd < 0 && pid == -1 && errno == EACCES) {
63			pid = 0;
64			continue;
65		}
66		break;
67	}
68	err = errno;
69
70	if (fd >= 0)
71		close(fd);
72
73	if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
74		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
75		      err, str_error_r(err, sbuf, sizeof(sbuf))))
76		return -1;
77
78	return 0;
79}
80
81unsigned long perf_event_open_cloexec_flag(void)
82{
83	static bool probed;
84
85	if (!probed) {
86		if (perf_flag_probe() <= 0)
87			flag = 0;
88		probed = true;
89	}
90
91	return flag;
92}

  1// SPDX-License-Identifier: GPL-2.0
  2#include <errno.h>
  3#include <sched.h>
  4#include "util.h"
  5#include "../perf.h"
  6#include "cloexec.h"
 
  7#include "asm/bug.h"
  8#include "debug.h"
  9#include <unistd.h>
 10#include <asm/unistd.h>
 11#include <sys/syscall.h>
 
 12
 13static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
 14
 15int __weak sched_getcpu(void)
 16{
 17#ifdef __NR_getcpu
 18	unsigned cpu;
 19	int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
 20	if (!err)
 21		return cpu;
 22#else
 23	errno = ENOSYS;
 24#endif
 25	return -1;
 26}
 27
 28static int perf_flag_probe(void)
 29{
 30	/* use 'safest' configuration as used in perf_evsel__fallback() */
 31	struct perf_event_attr attr = {
 32		.type = PERF_TYPE_SOFTWARE,
 33		.config = PERF_COUNT_SW_CPU_CLOCK,
 34		.exclude_kernel = 1,
 35	};
 36	int fd;
 37	int err;
 38	int cpu;
 39	pid_t pid = -1;
 40	char sbuf[STRERR_BUFSIZE];
 41
 42	cpu = sched_getcpu();
 43	if (cpu < 0)
 44		cpu = 0;
 45
 46	/*
 47	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
 48	 * changes.
 49	 */
 50	while (1) {
 51		/* check cloexec flag */
 52		fd = sys_perf_event_open(&attr, pid, cpu, -1,
 53					 PERF_FLAG_FD_CLOEXEC);
 54		if (fd < 0 && pid == -1 && errno == EACCES) {
 55			pid = 0;
 56			continue;
 57		}
 58		break;
 59	}
 60	err = errno;
 61
 62	if (fd >= 0) {
 63		close(fd);
 64		return 1;
 65	}
 66
 67	WARN_ONCE(err != EINVAL && err != EBUSY,
 68		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 69		  err, str_error_r(err, sbuf, sizeof(sbuf)));
 70
 71	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
 72	while (1) {
 73		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
 74		if (fd < 0 && pid == -1 && errno == EACCES) {
 75			pid = 0;
 76			continue;
 77		}
 78		break;
 79	}
 80	err = errno;
 81
 82	if (fd >= 0)
 83		close(fd);
 84
 85	if (WARN_ONCE(fd < 0 && err != EBUSY,
 86		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 87		      err, str_error_r(err, sbuf, sizeof(sbuf))))
 88		return -1;
 89
 90	return 0;
 91}
 92
 93unsigned long perf_event_open_cloexec_flag(void)
 94{
 95	static bool probed;
 96
 97	if (!probed) {
 98		if (perf_flag_probe() <= 0)
 99			flag = 0;
100		probed = true;
101	}
102
103	return flag;
104}