1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2020 Facebook */
 3#include <errno.h>
 4#include <stdio.h>
 5#include <stdlib.h>
 6#include <string.h>
 7#include <unistd.h>
 8#include <fcntl.h>
 9#include <sys/resource.h>
10#include <bpf/libbpf.h>
11#include <bpf/bpf.h>
12#include <sys/mount.h>
13#include "iterators.skel.h"
14#include "bpf_preload_common.h"
15
16int to_kernel = -1;
17int from_kernel = 0;
18
19static int send_link_to_kernel(struct bpf_link *link, const char *link_name)
20{
21	struct bpf_preload_info obj = {};
22	struct bpf_link_info info = {};
23	__u32 info_len = sizeof(info);
24	int err;
25
26	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);
27	if (err)
28		return err;
29	obj.link_id = info.id;
30	if (strlen(link_name) >= sizeof(obj.link_name))
31		return -E2BIG;
32	strcpy(obj.link_name, link_name);
33	if (write(to_kernel, &obj, sizeof(obj)) != sizeof(obj))
34		return -EPIPE;
35	return 0;
36}
37
38int main(int argc, char **argv)
39{
40	struct rlimit rlim = { RLIM_INFINITY, RLIM_INFINITY };
41	struct iterators_bpf *skel;
42	int err, magic;
43	int debug_fd;
44
45	debug_fd = open("/dev/console", O_WRONLY | O_NOCTTY | O_CLOEXEC);
46	if (debug_fd < 0)
47		return 1;
48	to_kernel = dup(1);
49	close(1);
50	dup(debug_fd);
51	/* now stdin and stderr point to /dev/console */
52
53	read(from_kernel, &magic, sizeof(magic));
54	if (magic != BPF_PRELOAD_START) {
55		printf("bad start magic %d\n", magic);
56		return 1;
57	}
58	setrlimit(RLIMIT_MEMLOCK, &rlim);
59	/* libbpf opens BPF object and loads it into the kernel */
60	skel = iterators_bpf__open_and_load();
61	if (!skel) {
62		/* iterators.skel.h is little endian.
63		 * libbpf doesn't support automatic little->big conversion
64		 * of BPF bytecode yet.
65		 * The program load will fail in such case.
66		 */
67		printf("Failed load could be due to wrong endianness\n");
68		return 1;
69	}
70	err = iterators_bpf__attach(skel);
71	if (err)
72		goto cleanup;
73
74	/* send two bpf_link IDs with names to the kernel */
75	err = send_link_to_kernel(skel->links.dump_bpf_map, "maps.debug");
76	if (err)
77		goto cleanup;
78	err = send_link_to_kernel(skel->links.dump_bpf_prog, "progs.debug");
79	if (err)
80		goto cleanup;
81
82	/* The kernel will proceed with pinnging the links in bpffs.
83	 * UMD will wait on read from pipe.
84	 */
85	read(from_kernel, &magic, sizeof(magic));
86	if (magic != BPF_PRELOAD_END) {
87		printf("bad final magic %d\n", magic);
88		err = -EINVAL;
89	}
90cleanup:
91	iterators_bpf__destroy(skel);
92
93	return err != 0;
94}