1a7d7a392SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only
2a92bb546SJakub Kicinski /*
3a92bb546SJakub Kicinski * Minimal BPF assembler
4a92bb546SJakub Kicinski *
5a92bb546SJakub Kicinski * Instead of libpcap high-level filter expressions, it can be quite
6a92bb546SJakub Kicinski * useful to define filters in low-level BPF assembler (that is kept
7a92bb546SJakub Kicinski * close to Steven McCanne and Van Jacobson's original BPF paper).
8a92bb546SJakub Kicinski * In particular for BPF JIT implementors, JIT security auditors, or
9a92bb546SJakub Kicinski * just for defining BPF expressions that contain extensions which are
10a92bb546SJakub Kicinski * not supported by compilers.
11a92bb546SJakub Kicinski *
12a92bb546SJakub Kicinski * How to get into it:
13a92bb546SJakub Kicinski *
14cb3f0d56SMauro Carvalho Chehab * 1) read Documentation/networking/filter.rst
15a92bb546SJakub Kicinski * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
16a92bb546SJakub Kicinski * blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
17a92bb546SJakub Kicinski * pretty print a C-like construct.
18a92bb546SJakub Kicinski *
19a92bb546SJakub Kicinski * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
20a92bb546SJakub Kicinski */
21a92bb546SJakub Kicinski
22a92bb546SJakub Kicinski #include <stdbool.h>
23a92bb546SJakub Kicinski #include <stdio.h>
24a92bb546SJakub Kicinski #include <string.h>
25a92bb546SJakub Kicinski
26a92bb546SJakub Kicinski extern void bpf_asm_compile(FILE *fp, bool cstyle);
27a92bb546SJakub Kicinski
main(int argc,char ** argv)28a92bb546SJakub Kicinski int main(int argc, char **argv)
29a92bb546SJakub Kicinski {
30a92bb546SJakub Kicinski FILE *fp = stdin;
31a92bb546SJakub Kicinski bool cstyle = false;
32a92bb546SJakub Kicinski int i;
33a92bb546SJakub Kicinski
34a92bb546SJakub Kicinski for (i = 1; i < argc; i++) {
35a92bb546SJakub Kicinski if (!strncmp("-c", argv[i], 2)) {
36a92bb546SJakub Kicinski cstyle = true;
37a92bb546SJakub Kicinski continue;
38a92bb546SJakub Kicinski }
39a92bb546SJakub Kicinski
40a92bb546SJakub Kicinski fp = fopen(argv[i], "r");
41a92bb546SJakub Kicinski if (!fp) {
42a92bb546SJakub Kicinski fp = stdin;
43a92bb546SJakub Kicinski continue;
44a92bb546SJakub Kicinski }
45a92bb546SJakub Kicinski
46a92bb546SJakub Kicinski break;
47a92bb546SJakub Kicinski }
48a92bb546SJakub Kicinski
49a92bb546SJakub Kicinski bpf_asm_compile(fp, cstyle);
50a92bb546SJakub Kicinski
51a92bb546SJakub Kicinski return 0;
52a92bb546SJakub Kicinski }
53