// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <sched.h>
#include "util.h" // for sched_getcpu()
#include "../perf-sys.h"
#include "cloexec.h"
#include "event.h"
#include "asm/bug.h"
#include "debug.h"
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/string.h>

static unsigned long flag = PERF_FLAG_FD_CLOEXEC;

static int perf_flag_probe(void)
{
        /* use 'safest' configuration as used in evsel__fallback() */
        struct perf_event_attr attr = {
                .type = PERF_TYPE_SOFTWARE,
                .config = PERF_COUNT_SW_CPU_CLOCK,
                .exclude_kernel = 1,
        };
        int fd;
        int err;
        int cpu;
        pid_t pid = -1;
        char sbuf[STRERR_BUFSIZE];

        cpu = sched_getcpu();
        if (cpu < 0)
                cpu = 0;

        /*
         * Using -1 for the pid is a workaround to avoid gratuitous jump label
         * changes.
         */
        while (1) {
                /* check cloexec flag */
                fd = sys_perf_event_open(&attr, pid, cpu, -1,
                                         PERF_FLAG_FD_CLOEXEC);
                if (fd < 0 && pid == -1 && errno == EACCES) {
                        pid = 0;
                        continue;
                }
                break;
        }
        err = errno;

        if (fd >= 0) {
                close(fd);
                return 1;
        }

        WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
                  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
                  err, str_error_r(err, sbuf, sizeof(sbuf)));

        /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
        while (1) {
                fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
                if (fd < 0 && pid == -1 && errno == EACCES) {
                        pid = 0;
                        continue;
                }
                break;
        }
        err = errno;

        if (fd >= 0)
                close(fd);

        if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
                      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
                      err, str_error_r(err, sbuf, sizeof(sbuf))))
                return -1;

        return 0;
}

unsigned long perf_event_open_cloexec_flag(void)
{
        static bool probed;

        if (!probed) {
                if (perf_flag_probe() <= 0)
                        flag = 0;
                probed = true;
        }

        return flag;
}