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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Minimal BPF assembler4 *5 * Instead of libpcap high-level filter expressions, it can be quite6 * useful to define filters in low-level BPF assembler (that is kept7 * close to Steven McCanne and Van Jacobson's original BPF paper).8 * In particular for BPF JIT implementors, JIT security auditors, or9 * just for defining BPF expressions that contain extensions which are10 * not supported by compilers.11 *12 * How to get into it:13 *14 * 1) read Documentation/networking/filter.rst15 * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary16 * blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will17 * 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 26extern void bpf_asm_compile(FILE *fp, bool cstyle);27 28int 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