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 "libbpf.h"
  13 #include "bpf_load.h"
  14 #include <linux/bpf.h>
  15 #include "cgroup_helpers.h"
  16
  17 #define CGROUP_PATH             "/my-cgroup"
  18
  19 int main(int argc, char **argv)
  20 {
  21         pid_t remote_pid, local_pid = getpid();
  22         int cg2, idx = 0, rc = 0;
  23         char filename[256];
  24
  25         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  26         if (load_bpf_file(filename)) {
  27                 printf("%s", bpf_log_buf);
  28                 return 1;
  29         }
  30
  31         if (setup_cgroup_environment())
  32                 goto err;
  33
  34         cg2 = create_and_get_cgroup(CGROUP_PATH);
  35
  36         if (!cg2)
  37                 goto err;
  38
  39         if (bpf_map_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
  40                 log_err("Adding target cgroup to map");
  41                 goto err;
  42         }
  43
  44         if (join_cgroup(CGROUP_PATH))
  45                 goto err;
  46
  47         /*
  48          * The installed helper program catched the sync call, and should
  49          * write it to the map.
  50          */
  51
  52         sync();
  53         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  54
  55         if (local_pid != remote_pid) {
  56                 fprintf(stderr,
  57                         "BPF Helper didn't write correct PID to map, but: %d\n",
  58                         remote_pid);
  59                 goto err;
  60         }
  61
  62         /* Verify the negative scenario; leave the cgroup */
  63         if (join_cgroup("/"))
  64                 goto err;
  65
  66         remote_pid = 0;
  67         bpf_map_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
  68
  69         sync();
  70         bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
  71
  72         if (local_pid == remote_pid) {
  73                 fprintf(stderr, "BPF cgroup negative test did not work\n");
  74                 goto err;
  75         }
  76
  77         goto out;
  78 err:
  79         rc = 1;
  80
  81 out:
  82         close(cg2);
  83         cleanup_cgroup_environment();
  84         return rc;
  85 }