tools: bpftool: use the kernel's instruction printer

Compile the instruction printer from kernel/bpf and use it
for disassembling "translated" eBPF code.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/bpf/bpftool/Documentation/bpftool-prog.rst

@@ -11,7 +11,7 @@ SYNOPSIS
 ========
 
 |	**bpftool** prog show [*PROG*]
-|	**bpftool** prog dump xlated *PROG*  file *FILE*
+|	**bpftool** prog dump xlated *PROG* [file *FILE*] [opcodes]
 |	**bpftool** prog dump jited  *PROG* [file *FILE*] [opcodes]
 |	**bpftool** prog pin *PROG* *FILE*
 |	**bpftool** prog help
@@ -28,9 +28,12 @@ DESCRIPTION
 		  Output will start with program ID followed by program type and
 		  zero or more named attributes (depending on kernel version).
 
-	**bpftool prog dump xlated** *PROG*  **file** *FILE*
-		  Dump eBPF instructions of the program from the kernel to a
-		  file.
+	**bpftool prog dump xlated** *PROG* [**file** *FILE*] [**opcodes**]
+		  Dump eBPF instructions of the program from the kernel.
+		  If *FILE* is specified image will be written to a file,
+		  otherwise it will be disassembled and printed to stdout.
+
+		  **opcodes** controls if raw opcodes will be printed.
 
 	**bpftool prog dump jited**  *PROG* [**file** *FILE*] [**opcodes**]
 		  Dump jited image (host machine code) of the program.

tools/bpf/bpftool/Makefile

@@ -51,7 +51,7 @@ CC = gcc
 
 CFLAGS += -O2
 CFLAGS += -W -Wall -Wextra -Wno-unused-parameter -Wshadow
-CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/tools/include/uapi -I$(srctree)/tools/include -I$(srctree)/tools/lib/bpf
+CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/tools/include/uapi -I$(srctree)/tools/include -I$(srctree)/tools/lib/bpf -I$(srctree)/kernel/bpf/
 LIBS = -lelf -lbfd -lopcodes $(LIBBPF)
 
 include $(wildcard *.d)
@@ -59,7 +59,10 @@ include $(wildcard *.d)
 all: $(OUTPUT)bpftool
 
 SRCS=$(wildcard *.c)
-OBJS=$(patsubst %.c,$(OUTPUT)%.o,$(SRCS))
+OBJS=$(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o
+
+$(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
+	$(QUIET_CC)$(COMPILE.c) -MMD -o $@ $<
 
 $(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
 	$(QUIET_LINK)$(CC) $(CFLAGS) -o $@ $^ $(LIBS)

tools/bpf/bpftool/main.h

@@ -36,11 +36,12 @@
 #ifndef __BPF_TOOL_H
 #define __BPF_TOOL_H
 
+/* BFD and kernel.h both define GCC_VERSION, differently */
+#undef GCC_VERSION
 #include <stdbool.h>
 #include <stdio.h>
 #include <linux/bpf.h>
-
-#define ARRAY_SIZE(a)	(sizeof(a) / sizeof(a[0]))
+#include <linux/kernel.h>
 
 #define err(msg...)	fprintf(stderr, "Error: " msg)
 #define warn(msg...)	fprintf(stderr, "Warning: " msg)
@@ -48,11 +49,6 @@
 
 #define ptr_to_u64(ptr)	((__u64)(unsigned long)(ptr))
 
-#define min(a, b)							\
-	({ typeof(a) _a = (a); typeof(b) _b = (b); _a > _b ? _b : _a; })
-#define max(a, b)							\
-	({ typeof(a) _a = (a); typeof(b) _b = (b); _a < _b ? _b : _a; })
-
 #define NEXT_ARG()	({ argc--; argv++; if (argc < 0) usage(); })
 #define NEXT_ARGP()	({ (*argc)--; (*argv)++; if (*argc < 0) usage(); })
 #define BAD_ARG()	({ err("what is '%s'?\n", *argv); -1; })

tools/bpf/bpftool/prog.c

@@ -35,6 +35,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -46,6 +47,7 @@
 #include <bpf.h>
 
 #include "main.h"
+#include "disasm.h"
 
 static const char * const prog_type_name[] = {
 	[BPF_PROG_TYPE_UNSPEC]		= "unspec",
@@ -297,11 +299,39 @@ static int do_show(int argc, char **argv)
 	return 0;
 }
 
+static void print_insn(struct bpf_verifier_env *env, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	vprintf(fmt, args);
+	va_end(args);
+}
+
+static void dump_xlated(void *buf, unsigned int len, bool opcodes)
+{
+	struct bpf_insn *insn = buf;
+	unsigned int i;
+
+	for (i = 0; i < len / sizeof(*insn); i++) {
+		printf("% 4d: ", i);
+		print_bpf_insn(print_insn, NULL, insn + i, true);
+
+		if (opcodes) {
+			printf("       ");
+			print_hex(insn + i, 8, " ");
+			printf("\n");
+		}
+
+		if (insn[i].code == (BPF_LD | BPF_IMM | BPF_DW))
+			i++;
+	}
+}
+
 static int do_dump(int argc, char **argv)
 {
 	struct bpf_prog_info info = {};
 	__u32 len = sizeof(info);
-	bool can_disasm = false;
 	unsigned int buf_size;
 	char *filepath = NULL;
 	bool opcodes = false;
@@ -315,7 +345,6 @@ static int do_dump(int argc, char **argv)
 	if (is_prefix(*argv, "jited")) {
 		member_len = &info.jited_prog_len;
 		member_ptr = &info.jited_prog_insns;
-		can_disasm = true;
 	} else if (is_prefix(*argv, "xlated")) {
 		member_len = &info.xlated_prog_len;
 		member_ptr = &info.xlated_prog_insns;
@@ -346,10 +375,6 @@ static int do_dump(int argc, char **argv)
 		NEXT_ARG();
 	}
 
-	if (!filepath && !can_disasm) {
-		err("expected 'file' got %s\n", *argv);
-		return -1;
-	}
 	if (argc) {
 		usage();
 		return -1;
@@ -409,7 +434,10 @@ static int do_dump(int argc, char **argv)
 			goto err_free;
 		}
 	} else {
-		disasm_print_insn(buf, *member_len, opcodes);
+		if (member_len == &info.jited_prog_len)
+			disasm_print_insn(buf, *member_len, opcodes);
+		else
+			dump_xlated(buf, *member_len, opcodes);
 	}
 
 	free(buf);
@@ -430,7 +458,7 @@ static int do_help(int argc, char **argv)
 {
 	fprintf(stderr,
 		"Usage: %s %s show [PROG]\n"
-		"       %s %s dump xlated PROG  file FILE\n"
+		"       %s %s dump xlated PROG [file FILE] [opcodes]\n"
 		"       %s %s dump jited  PROG [file FILE] [opcodes]\n"
 		"       %s %s pin   PROG FILE\n"
 		"       %s %s help\n"