linux-kernel - [PATCH v3 7/8] tools bpftool: Fix compilation error with new binutils

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Date:   Sun, 31 Jul 2022 18:38:33 -0700
From:   Andres Freund <andres@...razel.de>
To:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Quentin Monnet <quentin@...valent.com>,
        Ben Hutchings <benh@...ian.org>
Subject: [PATCH v3 7/8] tools bpftool: Fix compilation error with new binutils

binutils changed the signature of init_disassemble_info(), which now causes
compilation to fail for tools/bpf/bpftool/jit_disasm.c, e.g. on debian
unstable. Relevant binutils commit:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=60a3da00bd5407f07

Wire up the feature test and switch to init_disassemble_info_compat(),
which were introduced in prior commits, fixing the compilation failure.

I verified that bpftool can still disassemble bpf programs, both with an
old and new dis-asm.h API. There are no output changes for plain and json
formats. When comparing the output from old binutils (2.35)
to new bintuils with the patch (upstream snapshot) there are a few output
differences, but they are unrelated to this patch. An example hunk is:
   2f:	pop    %r14
   31:	pop    %r13
   33:	pop    %rbx
-  34:	leaveq
-  35:	retq
+  34:	leave
+  35:	ret

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Sedat Dilek <sedat.dilek@...il.com>
Cc: Quentin Monnet <quentin@...valent.com>
Link: http://lore.kernel.org/lkml/20220622181918.ykrs5rsnmx3og4sv@alap3.anarazel.de
Signed-off-by: Andres Freund <andres@...razel.de>
---
 tools/bpf/bpftool/Makefile     |  5 +++-
 tools/bpf/bpftool/jit_disasm.c | 42 +++++++++++++++++++++++++++-------
 2 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index c6d2c77d0252..436e671b2657 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -93,7 +93,7 @@ INSTALL ?= install
 RM ?= rm -f
 
 FEATURE_USER = .bpftool
-FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \
+FEATURE_TESTS = libbfd disassembler-four-args disassembler-init-styled zlib libcap \
 	clang-bpf-co-re
 FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \
 	clang-bpf-co-re
@@ -117,6 +117,9 @@ endif
 ifeq ($(feature-disassembler-four-args), 1)
 CFLAGS += -DDISASM_FOUR_ARGS_SIGNATURE
 endif
+ifeq ($(feature-disassembler-init-styled), 1)
+    CFLAGS += -DDISASM_INIT_STYLED
+endif
 
 LIBS = $(LIBBPF) -lelf -lz
 LIBS_BOOTSTRAP = $(LIBBPF_BOOTSTRAP) -lelf -lz
diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c
index 24734f2249d6..aaf99a0168c9 100644
--- a/tools/bpf/bpftool/jit_disasm.c
+++ b/tools/bpf/bpftool/jit_disasm.c
@@ -24,6 +24,7 @@
 #include <sys/stat.h>
 #include <limits.h>
 #include <bpf/libbpf.h>
+#include <tools/dis-asm-compat.h>
 
 #include "json_writer.h"
 #include "main.h"
@@ -39,15 +40,12 @@ static void get_exec_path(char *tpath, size_t size)
 }
 
 static int oper_count;
-static int fprintf_json(void *out, const char *fmt, ...)
+static int printf_json(void *out, const char *fmt, va_list ap)
 {
-	va_list ap;
 	char *s;
 	int err;
 
-	va_start(ap, fmt);
 	err = vasprintf(&s, fmt, ap);
-	va_end(ap);
 	if (err < 0)
 		return -1;
 
@@ -73,6 +71,32 @@ static int fprintf_json(void *out, const char *fmt, ...)
 	return 0;
 }
 
+static int fprintf_json(void *out, const char *fmt, ...)
+{
+	va_list ap;
+	int r;
+
+	va_start(ap, fmt);
+	r = printf_json(out, fmt, ap);
+	va_end(ap);
+
+	return r;
+}
+
+static int fprintf_json_styled(void *out,
+			       enum disassembler_style style __maybe_unused,
+			       const char *fmt, ...)
+{
+	va_list ap;
+	int r;
+
+	va_start(ap, fmt);
+	r = printf_json(out, fmt, ap);
+	va_end(ap);
+
+	return r;
+}
+
 void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
 		       const char *arch, const char *disassembler_options,
 		       const struct btf *btf,
@@ -99,11 +123,13 @@ void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
 	assert(bfd_check_format(bfdf, bfd_object));
 
 	if (json_output)
-		init_disassemble_info(&info, stdout,
-				      (fprintf_ftype) fprintf_json);
+		init_disassemble_info_compat(&info, stdout,
+					     (fprintf_ftype) fprintf_json,
+					     fprintf_json_styled);
 	else
-		init_disassemble_info(&info, stdout,
-				      (fprintf_ftype) fprintf);
+		init_disassemble_info_compat(&info, stdout,
+					     (fprintf_ftype) fprintf,
+					     fprintf_styled);
 
 	/* Update architecture info for offload. */
 	if (arch) {
-- 
2.37.0.3.g30cc8d0f14