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 <bpf/libbpf.h>
  12#include <bpf/bpf.h>
  13
  14/* This program verifies bpf attachment to tracepoint sys_enter_* and sys_exit_*.
  15 * This requires kernel CONFIG_FTRACE_SYSCALLS to be set.
  16 */
  17
  18static void usage(const char *cmd)
  19{
  20        printf("USAGE: %s [-i num_progs] [-h]\n", cmd);
  21        printf("       -i num_progs      # number of progs of the test\n");
  22        printf("       -h                # help\n");
  23}
  24
  25static void verify_map(int map_id)
  26{
  27        __u32 key = 0;
  28        __u32 val;
  29
  30        if (bpf_map_lookup_elem(map_id, &key, &val) != 0) {
  31                fprintf(stderr, "map_lookup failed: %s\n", strerror(errno));
  32                return;
  33        }
  34        if (val == 0) {
  35                fprintf(stderr, "failed: map #%d returns value 0\n", map_id);
  36                return;
  37        }
  38
  39        printf("verify map:%d val: %d\n", map_id, val);
  40
  41        val = 0;
  42        if (bpf_map_update_elem(map_id, &key, &val, BPF_ANY) != 0) {
  43                fprintf(stderr, "map_update failed: %s\n", strerror(errno));
  44                return;
  45        }
  46}
  47
  48static int test(char *filename, int num_progs)
  49{
  50        int map0_fds[num_progs], map1_fds[num_progs], fd, i, j = 0;
  51        struct bpf_link *links[num_progs * 4];
  52        struct bpf_object *objs[num_progs];
  53        struct bpf_program *prog;
  54
  55        for (i = 0; i < num_progs; i++) {
  56                objs[i] = bpf_object__open_file(filename, NULL);
  57                if (libbpf_get_error(objs[i])) {
  58                        fprintf(stderr, "opening BPF object file failed\n");
  59                        objs[i] = NULL;
  60                        goto cleanup;
  61                }
  62
  63                /* load BPF program */
  64                if (bpf_object__load(objs[i])) {
  65                        fprintf(stderr, "loading BPF object file failed\n");
  66                        goto cleanup;
  67                }
  68
  69                map0_fds[i] = bpf_object__find_map_fd_by_name(objs[i],
  70                                                              "enter_open_map");
  71                map1_fds[i] = bpf_object__find_map_fd_by_name(objs[i],
  72                                                              "exit_open_map");
  73                if (map0_fds[i] < 0 || map1_fds[i] < 0) {
  74                        fprintf(stderr, "finding a map in obj file failed\n");
  75                        goto cleanup;
  76                }
  77
  78                bpf_object__for_each_program(prog, objs[i]) {
  79                        links[j] = bpf_program__attach(prog);
  80                        if (libbpf_get_error(links[j])) {
  81                                fprintf(stderr, "bpf_program__attach failed\n");
  82                                links[j] = NULL;
  83                                goto cleanup;
  84                        }
  85                        j++;
  86                }
  87                printf("prog #%d: map ids %d %d\n", i, map0_fds[i], map1_fds[i]);
  88        }
  89
  90        /* current load_bpf_file has perf_event_open default pid = -1
  91         * and cpu = 0, which permits attached bpf execution on
  92         * all cpus for all pid's. bpf program execution ignores
  93         * cpu affinity.
  94         */
  95        /* trigger some "open" operations */
  96        fd = open(filename, O_RDONLY);
  97        if (fd < 0) {
  98                fprintf(stderr, "open failed: %s\n", strerror(errno));
  99                return 1;
 100        }
 101        close(fd);
 102
 103        /* verify the map */
 104        for (i = 0; i < num_progs; i++) {
 105                verify_map(map0_fds[i]);
 106                verify_map(map1_fds[i]);
 107        }
 108
 109cleanup:
 110        for (j--; j >= 0; j--)
 111                bpf_link__destroy(links[j]);
 112
 113        for (i--; i >= 0; i--)
 114                bpf_object__close(objs[i]);
 115        return 0;
 116}
 117
 118int main(int argc, char **argv)
 119{
 120        int opt, num_progs = 1;
 121        char filename[256];
 122
 123        while ((opt = getopt(argc, argv, "i:h")) != -1) {
 124                switch (opt) {
 125                case 'i':
 126                        num_progs = atoi(optarg);
 127                        break;
 128                case 'h':
 129                default:
 130                        usage(argv[0]);
 131                        return 0;
 132                }
 133        }
 134
 135        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 136
 137        return test(filename, num_progs);
 138}
 139