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 <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 }
86