samples/bpf/test_current_task_under_cgroup_user.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
   3  */
   4
   5 #define _GNU_SOURCE
   6 #include <stdio.h>
   7 #include <unistd.h>
   8 #include <bpf/bpf.h>
   9 #include <bpf/libbpf.h>
  10 #include "cgroup_helpers.h"
  11
  12 #define CGROUP_PATH             "/my-cgroup"
  13
  14 int main(int argc, char **argv)
  15 {
  16         pid_t remote_pid, local_pid = getpid();
  17         int cg2 = -1, idx = 0, rc = 1;
  18         struct bpf_link *link = NULL;
  19         struct bpf_program *prog;
  20         struct bpf_object *obj;
  21         char filename[256];
  22         int map_fd[2];
  23
  24         snprintf(filename, sizeof(filename), "%s.bpf.o", argv[0]);
  25         obj = bpf_object__open_file(filename, NULL);
  26         if (libbpf_get_error(obj)) {
  27                 fprintf(stderr, "ERROR: opening BPF object file failed\n");
  28                 return 0;
  29         }
  30
  31         prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
  32         if (!prog) {
  33                 printf("finding a prog in obj file failed\n");
  34                 goto cleanup;
  35         }
  36
  37         /* load BPF program */
  38         if (bpf_object__load(obj)) {
  39                 fprintf(stderr, "ERROR: loading BPF object file failed\n");
  40                 goto cleanup;
  41         }
  42
  43         map_fd[0] = bpf_object__find_map_fd_by_name(obj, "cgroup_map");
  44         map_fd[1] = bpf_object__find_map_fd_by_name(obj, "perf_map");
  45         if (map_fd[0] < 0 || map_fd[1] < 0) {
  46                 fprintf(stderr, "ERROR: finding a map in obj file failed\n");
  47                 goto cleanup;
  48         }
  49
  50         link = bpf_program__attach(prog);
  51         if (libbpf_get_error(link)) {
  52                 fprintf(stderr, "ERROR: bpf_program__attach failed\n");
  53                 link = NULL;
  54                 goto cleanup;
  55         }
  56
  57         if (setup_cgroup_environment())
  58                 goto err;
  59
  60         cg2 = create_and_get_cgroup(CGROUP_PATH);
  61
  62         if (cg2 < 0)
  63                 goto err;
  64
  65         if (bpf_map_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
  66                 log_err("Adding target cgroup to map");
  67                 goto err;
  68         }
  69
  70         if (join_cgroup(CGROUP_PATH))
  71                 goto err;
  72
  73         /*
  74          * The installed helper program catched the sync call, and should
  75          * write it to the map.
  76          */
  77
  78         sync();
  79         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  80
  81         if (local_pid != remote_pid) {
  82                 fprintf(stderr,
  83                         "BPF Helper didn't write correct PID to map, but: %d\n",
  84                         remote_pid);
  85                 goto err;
  86         }
  87
  88         /* Verify the negative scenario; leave the cgroup */
  89         if (join_cgroup("/"))
  90                 goto err;
  91
  92         remote_pid = 0;
  93         bpf_map_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
  94
  95         sync();
  96         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  97
  98         if (local_pid == remote_pid) {
  99                 fprintf(stderr, "BPF cgroup negative test did not work\n");
 100                 goto err;
 101         }
 102
 103         rc = 0;
 104
 105 err:
 106         if (cg2 != -1)
 107                 close(cg2);
 108
 109         cleanup_cgroup_environment();
 110
 111 cleanup:
 112         bpf_link__destroy(link);
 113         bpf_object__close(obj);
 114         return rc;
 115 }