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 }
82