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 <unistd.h>
8 #include <bpf/bpf.h>
9 #include <bpf/libbpf.h>
10 #include "cgroup_helpers.h"
11 
12 #define CGROUP_PATH		"/my-cgroup"
13 
main(int argc,char ** argv)14 int main(int argc, char **argv)
15 {
16 	pid_t remote_pid, local_pid = getpid();
17 	struct bpf_link *link = NULL;
18 	struct bpf_program *prog;
19 	int cg2, idx = 0, rc = 1;
20 	struct bpf_object *obj;
21 	char filename[256];
22 	int map_fd[2];
23 
24 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
25 	obj = bpf_object__open_file(filename, NULL);
26 	if (libbpf_get_error(obj)) {
27 		fprintf(stderr, "ERROR: opening BPF object file failed\n");
28 		return 0;
29 	}
30 
31 	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
32 	if (!prog) {
33 		printf("finding a prog in obj file failed\n");
34 		goto cleanup;
35 	}
36 
37 	/* load BPF program */
38 	if (bpf_object__load(obj)) {
39 		fprintf(stderr, "ERROR: loading BPF object file failed\n");
40 		goto cleanup;
41 	}
42 
43 	map_fd[0] = bpf_object__find_map_fd_by_name(obj, "cgroup_map");
44 	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "perf_map");
45 	if (map_fd[0] < 0 || map_fd[1] < 0) {
46 		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
47 		goto cleanup;
48 	}
49 
50 	link = bpf_program__attach(prog);
51 	if (libbpf_get_error(link)) {
52 		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
53 		link = NULL;
54 		goto cleanup;
55 	}
56 
57 	if (setup_cgroup_environment())
58 		goto err;
59 
60 	cg2 = create_and_get_cgroup(CGROUP_PATH);
61 
62 	if (cg2 < 0)
63 		goto err;
64 
65 	if (bpf_map_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
66 		log_err("Adding target cgroup to map");
67 		goto err;
68 	}
69 
70 	if (join_cgroup(CGROUP_PATH))
71 		goto err;
72 
73 	/*
74 	 * The installed helper program catched the sync call, and should
75 	 * write it to the map.
76 	 */
77 
78 	sync();
79 	bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
80 
81 	if (local_pid != remote_pid) {
82 		fprintf(stderr,
83 			"BPF Helper didn't write correct PID to map, but: %d\n",
84 			remote_pid);
85 		goto err;
86 	}
87 
88 	/* Verify the negative scenario; leave the cgroup */
89 	if (join_cgroup("/"))
90 		goto err;
91 
92 	remote_pid = 0;
93 	bpf_map_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
94 
95 	sync();
96 	bpf_map_lookup_elem(map_fd[1], &idx, &remote_pid);
97 
98 	if (local_pid == remote_pid) {
99 		fprintf(stderr, "BPF cgroup negative test did not work\n");
100 		goto err;
101 	}
102 
103 	rc = 0;
104 
105 err:
106 	close(cg2);
107 	cleanup_cgroup_environment();
108 
109 cleanup:
110 	bpf_link__destroy(link);
111 	bpf_object__close(obj);
112 	return rc;
113 }
114