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
 16int __weak sched_getcpu(void)
 17{
 18#ifdef __NR_getcpu
 19	unsigned cpu;
 20	int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
 21	if (!err)
 22		return cpu;
 23#else
 24	errno = ENOSYS;
 25#endif
 26	return -1;
 27}
 28
 29static int perf_flag_probe(void)
 30{
 31	/* use 'safest' configuration as used in perf_evsel__fallback() */
 32	struct perf_event_attr attr = {
 33		.type = PERF_TYPE_SOFTWARE,
 34		.config = PERF_COUNT_SW_CPU_CLOCK,
 35		.exclude_kernel = 1,
 36	};
 37	int fd;
 38	int err;
 39	int cpu;
 40	pid_t pid = -1;
 41	char sbuf[STRERR_BUFSIZE];
 42
 43	cpu = sched_getcpu();
 44	if (cpu < 0)
 45		cpu = 0;
 46
 47	/*
 48	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
 49	 * changes.
 50	 */
 51	while (1) {
 52		/* check cloexec flag */
 53		fd = sys_perf_event_open(&attr, pid, cpu, -1,
 54					 PERF_FLAG_FD_CLOEXEC);
 55		if (fd < 0 && pid == -1 && errno == EACCES) {
 56			pid = 0;
 57			continue;
 58		}
 59		break;
 60	}
 61	err = errno;
 62
 63	if (fd >= 0) {
 64		close(fd);
 65		return 1;
 66	}
 67
 68	WARN_ONCE(err != EINVAL && err != EBUSY,
 69		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 70		  err, str_error_r(err, sbuf, sizeof(sbuf)));
 71
 72	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
 73	while (1) {
 74		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
 75		if (fd < 0 && pid == -1 && errno == EACCES) {
 76			pid = 0;
 77			continue;
 78		}
 79		break;
 80	}
 81	err = errno;
 82
 83	if (fd >= 0)
 84		close(fd);
 85
 86	if (WARN_ONCE(fd < 0 && err != EBUSY,
 87		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 88		      err, str_error_r(err, sbuf, sizeof(sbuf))))
 89		return -1;
 90
 91	return 0;
 92}
 93
 94unsigned long perf_event_open_cloexec_flag(void)
 95{
 96	static bool probed;
 97
 98	if (!probed) {
 99		if (perf_flag_probe() <= 0)
100			flag = 0;
101		probed = true;
102	}
103
104	return flag;
105}

 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}