Scripted performance counting for side channel attacks

perf.c

#define _GNU_SOURCE
#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include <linux/perf_event.h>
#include <sched.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>

static inline uint64_t readu64(int fd) {
    uint64_t result;
    syscall(__NR_read, fd, &result, sizeof(result));
    return result;
}

int main(int argc, char** argv) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <args ...>\n", argv[0]);
        return 1;
    }

    cpu_set_t set;
    CPU_ZERO(&set);
    CPU_SET(0, &set);
    sched_setaffinity(0, sizeof(set), &set);

    struct perf_event_attr attr;
    memset(&attr, 0, sizeof(struct perf_event_attr));
    attr.type = PERF_TYPE_HARDWARE;
    attr.size = sizeof(struct perf_event_attr);
    attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
    attr.exclude_kernel = 1;
    attr.exclude_hv = 1;
    attr.exclude_idle = 1;
    int perfFd = syscall(__NR_perf_event_open, &attr, 0, 0, -1, 0);
    if (perfFd < 0) {
        perror("perf_event_open");
        return 1;
    }

    int pipes[2];
    pipe(pipes);
    dup2(pipes[0], 0);

    for (size_t n = 0; n < 100; ++n) {
        if (write(pipes[1], "testing123\n", 12) != 12) {
            perror("write");
            return 1;
        }

        uint64_t start = readu64(perfFd);

        pid_t pid = vfork();
        if (pid == 0) {
            execve(argv[1], &argv[1], 0);
            perror("execve");
            _exit(1);
        }

        int status;
        waitpid(pid, &status, 0);

        uint64_t delta = readu64(perfFd) - start;
        fprintf(stderr, "%llu\n", delta);

        if (!WIFEXITED(status)) {
            fprintf(stderr, "Child did not exit\n");
            return 1;
        }
    }

    return 0;
}