1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun #include <errno.h>
3*4882a593Smuzhiyun #include <sched.h>
4*4882a593Smuzhiyun #include "util.h" // for sched_getcpu()
5*4882a593Smuzhiyun #include "../perf-sys.h"
6*4882a593Smuzhiyun #include "cloexec.h"
7*4882a593Smuzhiyun #include "event.h"
8*4882a593Smuzhiyun #include "asm/bug.h"
9*4882a593Smuzhiyun #include "debug.h"
10*4882a593Smuzhiyun #include <unistd.h>
11*4882a593Smuzhiyun #include <sys/syscall.h>
12*4882a593Smuzhiyun #include <linux/string.h>
13*4882a593Smuzhiyun
14*4882a593Smuzhiyun static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
15*4882a593Smuzhiyun
sched_getcpu(void)16*4882a593Smuzhiyun int __weak sched_getcpu(void)
17*4882a593Smuzhiyun {
18*4882a593Smuzhiyun #ifdef __NR_getcpu
19*4882a593Smuzhiyun unsigned cpu;
20*4882a593Smuzhiyun int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
21*4882a593Smuzhiyun if (!err)
22*4882a593Smuzhiyun return cpu;
23*4882a593Smuzhiyun #else
24*4882a593Smuzhiyun errno = ENOSYS;
25*4882a593Smuzhiyun #endif
26*4882a593Smuzhiyun return -1;
27*4882a593Smuzhiyun }
28*4882a593Smuzhiyun
perf_flag_probe(void)29*4882a593Smuzhiyun static int perf_flag_probe(void)
30*4882a593Smuzhiyun {
31*4882a593Smuzhiyun /* use 'safest' configuration as used in evsel__fallback() */
32*4882a593Smuzhiyun struct perf_event_attr attr = {
33*4882a593Smuzhiyun .type = PERF_TYPE_SOFTWARE,
34*4882a593Smuzhiyun .config = PERF_COUNT_SW_CPU_CLOCK,
35*4882a593Smuzhiyun .exclude_kernel = 1,
36*4882a593Smuzhiyun };
37*4882a593Smuzhiyun int fd;
38*4882a593Smuzhiyun int err;
39*4882a593Smuzhiyun int cpu;
40*4882a593Smuzhiyun pid_t pid = -1;
41*4882a593Smuzhiyun char sbuf[STRERR_BUFSIZE];
42*4882a593Smuzhiyun
43*4882a593Smuzhiyun cpu = sched_getcpu();
44*4882a593Smuzhiyun if (cpu < 0)
45*4882a593Smuzhiyun cpu = 0;
46*4882a593Smuzhiyun
47*4882a593Smuzhiyun /*
48*4882a593Smuzhiyun * Using -1 for the pid is a workaround to avoid gratuitous jump label
49*4882a593Smuzhiyun * changes.
50*4882a593Smuzhiyun */
51*4882a593Smuzhiyun while (1) {
52*4882a593Smuzhiyun /* check cloexec flag */
53*4882a593Smuzhiyun fd = sys_perf_event_open(&attr, pid, cpu, -1,
54*4882a593Smuzhiyun PERF_FLAG_FD_CLOEXEC);
55*4882a593Smuzhiyun if (fd < 0 && pid == -1 && errno == EACCES) {
56*4882a593Smuzhiyun pid = 0;
57*4882a593Smuzhiyun continue;
58*4882a593Smuzhiyun }
59*4882a593Smuzhiyun break;
60*4882a593Smuzhiyun }
61*4882a593Smuzhiyun err = errno;
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun if (fd >= 0) {
64*4882a593Smuzhiyun close(fd);
65*4882a593Smuzhiyun return 1;
66*4882a593Smuzhiyun }
67*4882a593Smuzhiyun
68*4882a593Smuzhiyun WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
69*4882a593Smuzhiyun "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
70*4882a593Smuzhiyun err, str_error_r(err, sbuf, sizeof(sbuf)));
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
73*4882a593Smuzhiyun while (1) {
74*4882a593Smuzhiyun fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
75*4882a593Smuzhiyun if (fd < 0 && pid == -1 && errno == EACCES) {
76*4882a593Smuzhiyun pid = 0;
77*4882a593Smuzhiyun continue;
78*4882a593Smuzhiyun }
79*4882a593Smuzhiyun break;
80*4882a593Smuzhiyun }
81*4882a593Smuzhiyun err = errno;
82*4882a593Smuzhiyun
83*4882a593Smuzhiyun if (fd >= 0)
84*4882a593Smuzhiyun close(fd);
85*4882a593Smuzhiyun
86*4882a593Smuzhiyun if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
87*4882a593Smuzhiyun "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
88*4882a593Smuzhiyun err, str_error_r(err, sbuf, sizeof(sbuf))))
89*4882a593Smuzhiyun return -1;
90*4882a593Smuzhiyun
91*4882a593Smuzhiyun return 0;
92*4882a593Smuzhiyun }
93*4882a593Smuzhiyun
perf_event_open_cloexec_flag(void)94*4882a593Smuzhiyun unsigned long perf_event_open_cloexec_flag(void)
95*4882a593Smuzhiyun {
96*4882a593Smuzhiyun static bool probed;
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun if (!probed) {
99*4882a593Smuzhiyun if (perf_flag_probe() <= 0)
100*4882a593Smuzhiyun flag = 0;
101*4882a593Smuzhiyun probed = true;
102*4882a593Smuzhiyun }
103*4882a593Smuzhiyun
104*4882a593Smuzhiyun return flag;
105*4882a593Smuzhiyun }
106