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

 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}