1// SPDX-License-Identifier: GPL-2.0
2#include <stdio.h>
3#include <stdlib.h>
4#include <unistd.h>
5#include <linux/filter.h>
6#include <linux/seccomp.h>
7#include <sys/prctl.h>
8#include <bpf/bpf.h>
9#include <bpf/libbpf.h>
10#include <sys/resource.h>
11#include "trace_helpers.h"
12
13#ifdef __mips__
14#define	MAX_ENTRIES  6000 /* MIPS n64 syscalls start at 5000 */
15#else
16#define	MAX_ENTRIES  1024
17#endif
18
19/* install fake seccomp program to enable seccomp code path inside the kernel,
20 * so that our kprobe attached to seccomp_phase1() can be triggered
21 */
22static void install_accept_all_seccomp(void)
23{
24	struct sock_filter filter[] = {
25		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
26	};
27	struct sock_fprog prog = {
28		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
29		.filter = filter,
30	};
31	if (prctl(PR_SET_SECCOMP, 2, &prog))
32		perror("prctl");
33}
34
35int main(int ac, char **argv)
36{
37	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
38	struct bpf_link *link = NULL;
39	struct bpf_program *prog;
40	struct bpf_object *obj;
41	int key, fd, progs_fd;
42	const char *section;
43	char filename[256];
44	FILE *f;
45
46	setrlimit(RLIMIT_MEMLOCK, &r);
47
48	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
49	obj = bpf_object__open_file(filename, NULL);
50	if (libbpf_get_error(obj)) {
51		fprintf(stderr, "ERROR: opening BPF object file failed\n");
52		return 0;
53	}
54
55	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
56	if (!prog) {
57		printf("finding a prog in obj file failed\n");
58		goto cleanup;
59	}
60
61	/* load BPF program */
62	if (bpf_object__load(obj)) {
63		fprintf(stderr, "ERROR: loading BPF object file failed\n");
64		goto cleanup;
65	}
66
67	link = bpf_program__attach(prog);
68	if (libbpf_get_error(link)) {
69		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
70		link = NULL;
71		goto cleanup;
72	}
73
74	progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
75	if (progs_fd < 0) {
76		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
77		goto cleanup;
78	}
79
80	bpf_object__for_each_program(prog, obj) {
81		section = bpf_program__section_name(prog);
82		/* register only syscalls to PROG_ARRAY */
83		if (sscanf(section, "kprobe/%d", &key) != 1)
84			continue;
85
86		fd = bpf_program__fd(prog);
87		bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
88	}
89
90	install_accept_all_seccomp();
91
92	f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
93	(void) f;
94
95	read_trace_pipe();
96
97cleanup:
98	bpf_link__destroy(link);
99	bpf_object__close(obj);
100	return 0;
101}
102