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 "trace_helpers.h"
11#include "bpf_util.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)ARRAY_SIZE(filter),
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 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(buf: filename, size: sizeof(filename), fmt: "%s.bpf.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
94cleanup:
95 bpf_link__destroy(link);
96 bpf_object__close(obj);
97 return 0;
98}
99

source code of linux/samples/bpf/tracex5_user.c