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