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