Commit 424ebaa3 authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Andrii Nakryiko
Browse files

selftests/bpf: extract utility function for BPF disassembly 



struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz);

  Disassembles instruction 'insn' to a text buffer 'buf'.
  Removes insn->code hex prefix added by kernel disassembly routine.
  Returns a pointer to the next instruction
  (increments insn by either 1 or 2).

Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240722233844.1406874-5-eddyz87@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parent 91b7fbf3

tools/testing/selftests/bpf/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -661,6 +661,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c \ 
			 test_loader.c		\

			 xsk.c			\

			 disasm.c		\

			 disasm_helpers.c	\

			 json_writer.c 		\

			 flow_dissector_load.h	\

			 ip_check_defrag_frags.h

tools/testing/selftests/bpf/disasm_helpers.c

0 → 100644
+51 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)



#include <bpf/bpf.h>

#include "disasm.h"



struct print_insn_context {

	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);

}



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,

		.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);

}

tools/testing/selftests/bpf/disasm_helpers.h

0 → 100644
+12 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */



#ifndef __DISASM_HELPERS_H

#define __DISASM_HELPERS_H



#include <stdlib.h>



struct bpf_insn;



struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz);



#endif /* __DISASM_HELPERS_H */

tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c

+10 −64
Original line number Diff line number Diff line
@@ -10,7 +10,8 @@ 
#include "bpf/btf.h"

#include "bpf_util.h"

#include "linux/filter.h"

#include "disasm.h"

#include "linux/kernel.h"

#include "disasm_helpers.h"



#define MAX_PROG_TEXT_SZ (32 * 1024)
@@ -628,63 +629,6 @@ static bool match_pattern(struct btf *btf, char *pattern, char *text, char *reg_ 
	return false;

}



static void print_insn(void *private_data, const char *fmt, ...)

{

	va_list args;



	va_start(args, fmt);

	vfprintf((FILE *)private_data, fmt, args);

	va_end(args);

}



/* Disassemble instructions to a stream */

static void print_xlated(FILE *out, struct bpf_insn *insn, __u32 len)

{

	const struct bpf_insn_cbs cbs = {

		.cb_print	= print_insn,

		.cb_call	= NULL,

		.cb_imm		= NULL,

		.private_data	= out,

	};

	bool double_insn = false;

	int i;



	for (i = 0; i < len; i++) {

		if (double_insn) {

			double_insn = false;

			continue;

		}



		double_insn = insn[i].code == (BPF_LD | BPF_IMM | BPF_DW);

		print_bpf_insn(&cbs, insn + i, true);

	}

}



/* We share code with kernel BPF disassembler, it adds '(FF) ' prefix

 * for each instruction (FF stands for instruction `code` byte).

 * This function removes the prefix inplace for each line in `str`.

 */

static void remove_insn_prefix(char *str, int size)

{

	const int prefix_size = 5;



	int write_pos = 0, read_pos = prefix_size;

	int len = strlen(str);

	char c;



	size = min(size, len);



	while (read_pos < size) {

		c = str[read_pos++];

		if (c == 0)

			break;

		str[write_pos++] = c;

		if (c == '\n')

			read_pos += prefix_size;

	}

	str[write_pos] = 0;

}



struct prog_info {

	char *prog_kind;

	enum bpf_prog_type prog_type;
@@ -699,9 +643,10 @@ static void match_program(struct btf *btf, 
			  char *reg_map[][2],

			  bool skip_first_insn)

{

	struct bpf_insn *buf = NULL;

	struct bpf_insn *buf = NULL, *insn, *insn_end;

	int err = 0, prog_fd = 0;

	FILE *prog_out = NULL;

	char insn_buf[64];

	char *text = NULL;

	__u32 cnt = 0;
@@ -739,12 +684,13 @@ static void match_program(struct btf *btf, 
		PRINT_FAIL("Can't open memory stream\n");

		goto out;

	}

	if (skip_first_insn)

		print_xlated(prog_out, buf + 1, cnt - 1);

	else

		print_xlated(prog_out, buf, cnt);

	insn_end = buf + cnt;

	insn = buf + (skip_first_insn ? 1 : 0);

	while (insn < insn_end) {

		insn = disasm_insn(insn, insn_buf, sizeof(insn_buf));

		fprintf(prog_out, "%s\n", insn_buf);

	}

	fclose(prog_out);

	remove_insn_prefix(text, MAX_PROG_TEXT_SZ);



	ASSERT_TRUE(match_pattern(btf, pattern, text, reg_map),

		    pinfo->prog_kind);

tools/testing/selftests/bpf/testing_helpers.c

+1 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <errno.h>

#include <bpf/bpf.h>

#include <bpf/libbpf.h>

#include "disasm.h"

#include "test_progs.h"

#include "testing_helpers.h"

#include <linux/membarrier.h>