| 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 | |
| 8 | static unsigned long flag = PERF_FLAG_FD_CLOEXEC; |
| 9 | |
| 10 | #ifdef __GLIBC_PREREQ |
| 11 | #if !__GLIBC_PREREQ(2, 6) |
| 12 | int __weak sched_getcpu(void) |
| 13 | { |
| 14 | errno = ENOSYS; |
| 15 | return -1; |
| 16 | } |
| 17 | #endif |
| 18 | #endif |
| 19 | |
| 20 | static 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 | |
| 85 | unsigned 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 | } |