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.txt 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