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1// SPDX-License-Identifier: GPL-2.02#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 label36 * 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}93