LXR linux/tools/bpf/bpf

   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
  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