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