1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-only
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Minimal BPF assembler
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Instead of libpcap high-level filter expressions, it can be quite
6*4882a593Smuzhiyun * useful to define filters in low-level BPF assembler (that is kept
7*4882a593Smuzhiyun * close to Steven McCanne and Van Jacobson's original BPF paper).
8*4882a593Smuzhiyun * In particular for BPF JIT implementors, JIT security auditors, or
9*4882a593Smuzhiyun * just for defining BPF expressions that contain extensions which are
10*4882a593Smuzhiyun * not supported by compilers.
11*4882a593Smuzhiyun *
12*4882a593Smuzhiyun * How to get into it:
13*4882a593Smuzhiyun *
14*4882a593Smuzhiyun * 1) read Documentation/networking/filter.rst
15*4882a593Smuzhiyun * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
16*4882a593Smuzhiyun * blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
17*4882a593Smuzhiyun * pretty print a C-like construct.
18*4882a593Smuzhiyun *
19*4882a593Smuzhiyun * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
20*4882a593Smuzhiyun */
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun #include <stdbool.h>
23*4882a593Smuzhiyun #include <stdio.h>
24*4882a593Smuzhiyun #include <string.h>
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun extern void bpf_asm_compile(FILE *fp, bool cstyle);
27*4882a593Smuzhiyun
main(int argc,char ** argv)28*4882a593Smuzhiyun int main(int argc, char **argv)
29*4882a593Smuzhiyun {
30*4882a593Smuzhiyun FILE *fp = stdin;
31*4882a593Smuzhiyun bool cstyle = false;
32*4882a593Smuzhiyun int i;
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun for (i = 1; i < argc; i++) {
35*4882a593Smuzhiyun if (!strncmp("-c", argv[i], 2)) {
36*4882a593Smuzhiyun cstyle = true;
37*4882a593Smuzhiyun continue;
38*4882a593Smuzhiyun }
39*4882a593Smuzhiyun
40*4882a593Smuzhiyun fp = fopen(argv[i], "r");
41*4882a593Smuzhiyun if (!fp) {
42*4882a593Smuzhiyun fp = stdin;
43*4882a593Smuzhiyun continue;
44*4882a593Smuzhiyun }
45*4882a593Smuzhiyun
46*4882a593Smuzhiyun break;
47*4882a593Smuzhiyun }
48*4882a593Smuzhiyun
49*4882a593Smuzhiyun bpf_asm_compile(fp, cstyle);
50*4882a593Smuzhiyun
51*4882a593Smuzhiyun return 0;
52*4882a593Smuzhiyun }
53