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 <linux/bpf.h>
   8 #include <unistd.h>
   9 #include <bpf/bpf.h>
  10 #include "bpf_load.h"
  11 #include "cgroup_helpers.h"
  12
  13 #define CGROUP_PATH             "/my-cgroup"
  14
  15 int main(int argc, char **argv)
  16 {
  17         pid_t remote_pid, local_pid = getpid();
  18         int cg2, idx = 0, rc = 0;
  19         char filename[256];
  20
  21         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  22         if (load_bpf_file(filename)) {
  23                 printf("%s", bpf_log_buf);
  24                 return 1;
  25         }
  26
  27         if (setup_cgroup_environment())
  28                 goto err;
  29
  30         cg2 = create_and_get_cgroup(CGROUP_PATH);
  31
  32         if (cg2 < 0)
  33                 goto err;
  34
  35         if (bpf_map_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
  36                 log_err("Adding target cgroup to map");
  37                 goto err;
  38         }
  39
  40         if (join_cgroup(CGROUP_PATH))
  41                 goto err;
  42
  43         /*
  44          * The installed helper program catched the sync call, and should
  45          * write it to the map.
  46          */
  47
  48         sync();
  49         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  50
  51         if (local_pid != remote_pid) {
  52                 fprintf(stderr,
  53                         "BPF Helper didn't write correct PID to map, but: %d\n",
  54                         remote_pid);
  55                 goto err;
  56         }
  57
  58         /* Verify the negative scenario; leave the cgroup */
  59         if (join_cgroup("/"))
  60                 goto err;
  61
  62         remote_pid = 0;
  63         bpf_map_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
  64
  65         sync();
  66         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  67
  68         if (local_pid == remote_pid) {
  69                 fprintf(stderr, "BPF cgroup negative test did not work\n");
  70                 goto err;
  71         }
  72
  73         goto out;
  74 err:
  75         rc = 1;
  76
  77 out:
  78         close(cg2);
  79         cleanup_cgroup_environment();
  80         return rc;
  81 }