1 files changed, 69 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/disasm_helpers.c b/tools/testing/selftests/bpf/disasm_helpers.c
new file mode 100644
index 000000000000..f529f1c8c171
--- /dev/null
+++ b/tools/testing/selftests/bpf/disasm_helpers.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+#include <bpf/bpf.h>
+#include "disasm.h"
+
+struct print_insn_context {
+	char scratch[16];
+	char *buf;
+	size_t sz;
+};
+
+static void print_insn_cb(void *private_data, const char *fmt, ...)
+{
+	struct print_insn_context *ctx = private_data;
+	va_list args;
+
+	va_start(args, fmt);
+	vsnprintf(ctx->buf, ctx->sz, fmt, args);
+	va_end(args);
+}
+
+static const char *print_call_cb(void *private_data, const struct bpf_insn *insn)
+{
+	struct print_insn_context *ctx = private_data;
+
+	/* For pseudo calls verifier.c:jit_subprogs() hides original
+	 * imm to insn->off and changes insn->imm to be an index of
+	 * the subprog instead.
+	 */
+	if (insn->src_reg == BPF_PSEUDO_CALL) {
+		snprintf(ctx->scratch, sizeof(ctx->scratch), "%+d", insn->off);
+		return ctx->scratch;
+	}
+
+	return NULL;
+}
+
+struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz)
+{
+	struct print_insn_context ctx = {
+		.buf = buf,
+		.sz = buf_sz,
+	};
+	struct bpf_insn_cbs cbs = {
+		.cb_print	= print_insn_cb,
+		.cb_call	= print_call_cb,
+		.private_data	= &ctx,
+	};
+	char *tmp, *pfx_end, *sfx_start;
+	bool double_insn;
+	int len;
+
+	print_bpf_insn(&cbs, insn, true);
+	/* We share code with kernel BPF disassembler, it adds '(FF) ' prefix
+	 * for each instruction (FF stands for instruction `code` byte).
+	 * Remove the prefix inplace, and also simplify call instructions.
+	 * E.g.: "(85) call foo#10" -> "call foo".
+	 * Also remove newline in the end (the 'max(strlen(buf) - 1, 0)' thing).
+	 */
+	pfx_end = buf + 5;
+	sfx_start = buf + max((int)strlen(buf) - 1, 0);
+	if (strncmp(pfx_end, "call ", 5) == 0 && (tmp = strrchr(buf, '#')))
+		sfx_start = tmp;
+	len = sfx_start - pfx_end;
+	memmove(buf, pfx_end, len);
+	buf[len] = 0;
+	double_insn = insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+	return insn + (double_insn ? 2 : 1);
+}