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#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}