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  */
install_accept_all_seccomp(void)22 static 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 
main(int ac,char ** argv)35 int main(int ac, char **argv)
36 {
37 	struct bpf_link *link = NULL;
38 	struct bpf_program *prog;
39 	struct bpf_object *obj;
40 	int key, fd, progs_fd;
41 	const char *section;
42 	char filename[256];
43 	FILE *f;
44 
45 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
46 	obj = bpf_object__open_file(filename, NULL);
47 	if (libbpf_get_error(obj)) {
48 		fprintf(stderr, "ERROR: opening BPF object file failed\n");
49 		return 0;
50 	}
51 
52 	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
53 	if (!prog) {
54 		printf("finding a prog in obj file failed\n");
55 		goto cleanup;
56 	}
57 
58 	/* load BPF program */
59 	if (bpf_object__load(obj)) {
60 		fprintf(stderr, "ERROR: loading BPF object file failed\n");
61 		goto cleanup;
62 	}
63 
64 	link = bpf_program__attach(prog);
65 	if (libbpf_get_error(link)) {
66 		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
67 		link = NULL;
68 		goto cleanup;
69 	}
70 
71 	progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
72 	if (progs_fd < 0) {
73 		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
74 		goto cleanup;
75 	}
76 
77 	bpf_object__for_each_program(prog, obj) {
78 		section = bpf_program__section_name(prog);
79 		/* register only syscalls to PROG_ARRAY */
80 		if (sscanf(section, "kprobe/%d", &key) != 1)
81 			continue;
82 
83 		fd = bpf_program__fd(prog);
84 		bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
85 	}
86 
87 	install_accept_all_seccomp();
88 
89 	f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
90 	(void) f;
91 
92 	read_trace_pipe();
93 
94 cleanup:
95 	bpf_link__destroy(link);
96 	bpf_object__close(obj);
97 	return 0;
98 }
99