Thomas Gleixner | a7d7a39 | 2019-06-03 07:44:48 +0200 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0-only |
Daniel Borkmann | 3f35638 | 2013-12-11 23:43:44 +0100 | [diff] [blame] | 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 | * |
Mauro Carvalho Chehab | cb3f0d5 | 2020-04-28 00:01:36 +0200 | [diff] [blame] | 14 | * 1) read Documentation/networking/filter.rst |
Daniel Borkmann | 3f35638 | 2013-12-11 23:43:44 +0100 | [diff] [blame] | 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> |
Daniel Borkmann | 3f35638 | 2013-12-11 23:43:44 +0100 | [diff] [blame] | 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 | } |