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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Minimal BPF assembler
+ *
+ * Instead of libpcap high-level filter expressions, it can be quite
+ * useful to define filters in low-level BPF assembler (that is kept
+ * close to Steven McCanne and Van Jacobson's original BPF paper).
+ * In particular for BPF JIT implementors, JIT security auditors, or
+ * just for defining BPF expressions that contain extensions which are
+ * not supported by compilers.
+ *
+ * How to get into it:
+ *
+ * 1) read Documentation/networking/filter.rst
+ * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
+ * blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
+ * pretty print a C-like construct.
+ *
+ * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+extern void bpf_asm_compile(FILE *fp, bool cstyle);
+
+int main(int argc, char **argv)
+{
+ FILE *fp = stdin;
+ bool cstyle = false;
+ int i;
+
+ for (i = 1; i < argc; i++) {
+ if (!strncmp("-c", argv[i], 2)) {
+ cstyle = true;
+ continue;
+ }
+
+ fp = fopen(argv[i], "r");
+ if (!fp) {
+ fp = stdin;
+ continue;
+ }
+
+ break;
+ }
+
+ bpf_asm_compile(fp, cstyle);
+
+ return 0;
+}