samples/bpf/test_current_task_under_cgroup_user.c

   1 /* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7
   8 #define _GNU_SOURCE
   9 #include <stdio.h>
  10 #include <linux/bpf.h>
  11 #include <unistd.h>
  12 #include <bpf/bpf.h>
  13 #include "bpf_load.h"
  14 #include "cgroup_helpers.h"
  15
  16 #define CGROUP_PATH             "/my-cgroup"
  17
  18 int main(int argc, char **argv)
  19 {
  20         pid_t remote_pid, local_pid = getpid();
  21         int cg2, idx = 0, rc = 0;
  22         char filename[256];
  23
  24         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  25         if (load_bpf_file(filename)) {
  26                 printf("%s", bpf_log_buf);
  27                 return 1;
  28         }
  29
  30         if (setup_cgroup_environment())
  31                 goto err;
  32
  33         cg2 = create_and_get_cgroup(CGROUP_PATH);
  34
  35         if (cg2 < 0)
  36                 goto err;
  37
  38         if (bpf_map_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
  39                 log_err("Adding target cgroup to map");
  40                 goto err;
  41         }
  42
  43         if (join_cgroup(CGROUP_PATH))
  44                 goto err;
  45
  46         /*
  47          * The installed helper program catched the sync call, and should
  48          * write it to the map.
  49          */
  50
  51         sync();
  52         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  53
  54         if (local_pid != remote_pid) {
  55                 fprintf(stderr,
  56                         "BPF Helper didn't write correct PID to map, but: %d\n",
  57                         remote_pid);
  58                 goto err;
  59         }
  60
  61         /* Verify the negative scenario; leave the cgroup */
  62         if (join_cgroup("/"))
  63                 goto err;
  64
  65         remote_pid = 0;
  66         bpf_map_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
  67
  68         sync();
  69         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  70
  71         if (local_pid == remote_pid) {
  72                 fprintf(stderr, "BPF cgroup negative test did not work\n");
  73                 goto err;
  74         }
  75
  76         goto out;
  77 err:
  78         rc = 1;
  79
  80 out:
  81         close(cg2);
  82         cleanup_cgroup_environment();
  83         return rc;
  84 }