LXR linux/samples/bpf/syscall_tp

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* Copyright (c) 2017 Facebook
   3 */
   4#include <stdio.h>
   5#include <unistd.h>
   6#include <fcntl.h>
   7#include <stdlib.h>
   8#include <string.h>
   9#include <linux/perf_event.h>
  10#include <errno.h>
  11#include <sys/resource.h>
  12#include <bpf/libbpf.h>
  13#include <bpf/bpf.h>
  14
  15/* This program verifies bpf attachment to tracepoint sys_enter_* and sys_exit_*.
  16 * This requires kernel CONFIG_FTRACE_SYSCALLS to be set.
  17 */
  18
  19static void usage(const char *cmd)
  20{
  21        printf("USAGE: %s [-i num_progs] [-h]\n", cmd);
  22        printf("       -i num_progs      # number of progs of the test\n");
  23        printf("       -h                # help\n");
  24}
  25
  26static void verify_map(int map_id)
  27{
  28        __u32 key = 0;
  29        __u32 val;
  30
  31        if (bpf_map_lookup_elem(map_id, &key, &val) != 0) {
  32                fprintf(stderr, "map_lookup failed: %s\n", strerror(errno));
  33                return;
  34        }
  35        if (val == 0) {
  36                fprintf(stderr, "failed: map #%d returns value 0\n", map_id);
  37                return;
  38        }
  39        val = 0;
  40        if (bpf_map_update_elem(map_id, &key, &val, BPF_ANY) != 0) {
  41                fprintf(stderr, "map_update failed: %s\n", strerror(errno));
  42                return;
  43        }
  44}
  45
  46static int test(char *filename, int num_progs)
  47{
  48        int map0_fds[num_progs], map1_fds[num_progs], fd, i, j = 0;
  49        struct bpf_link *links[num_progs * 4];
  50        struct bpf_object *objs[num_progs];
  51        struct bpf_program *prog;
  52
  53        for (i = 0; i < num_progs; i++) {
  54                objs[i] = bpf_object__open_file(filename, NULL);
  55                if (libbpf_get_error(objs[i])) {
  56                        fprintf(stderr, "opening BPF object file failed\n");
  57                        objs[i] = NULL;
  58                        goto cleanup;
  59                }
  60
  61                /* load BPF program */
  62                if (bpf_object__load(objs[i])) {
  63                        fprintf(stderr, "loading BPF object file failed\n");
  64                        goto cleanup;
  65                }
  66
  67                map0_fds[i] = bpf_object__find_map_fd_by_name(objs[i],
  68                                                              "enter_open_map");
  69                map1_fds[i] = bpf_object__find_map_fd_by_name(objs[i],
  70                                                              "exit_open_map");
  71                if (map0_fds[i] < 0 || map1_fds[i] < 0) {
  72                        fprintf(stderr, "finding a map in obj file failed\n");
  73                        goto cleanup;
  74                }
  75
  76                bpf_object__for_each_program(prog, objs[i]) {
  77                        links[j] = bpf_program__attach(prog);
  78                        if (libbpf_get_error(links[j])) {
  79                                fprintf(stderr, "bpf_program__attach failed\n");
  80                                links[j] = NULL;
  81                                goto cleanup;
  82                        }
  83                        j++;
  84                }
  85                printf("prog #%d: map ids %d %d\n", i, map0_fds[i], map1_fds[i]);
  86        }
  87
  88        /* current load_bpf_file has perf_event_open default pid = -1
  89         * and cpu = 0, which permits attached bpf execution on
  90         * all cpus for all pid's. bpf program execution ignores
  91         * cpu affinity.
  92         */
  93        /* trigger some "open" operations */
  94        fd = open(filename, O_RDONLY);
  95        if (fd < 0) {
  96                fprintf(stderr, "open failed: %s\n", strerror(errno));
  97                return 1;
  98        }
  99        close(fd);
 100
 101        /* verify the map */
 102        for (i = 0; i < num_progs; i++) {
 103                verify_map(map0_fds[i]);
 104                verify_map(map1_fds[i]);
 105        }
 106
 107cleanup:
 108        for (j--; j >= 0; j--)
 109                bpf_link__destroy(links[j]);
 110
 111        for (i--; i >= 0; i--)
 112                bpf_object__close(objs[i]);
 113        return 0;
 114}
 115
 116int main(int argc, char **argv)
 117{
 118        int opt, num_progs = 1;
 119        char filename[256];
 120
 121        while ((opt = getopt(argc, argv, "i:h")) != -1) {
 122                switch (opt) {
 123                case 'i':
 124                        num_progs = atoi(optarg);
 125                        break;
 126                case 'h':
 127                default:
 128                        usage(argv[0]);
 129                        return 0;
 130                }
 131        }
 132
 133        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 134
 135        return test(filename, num_progs);
 136}
 137