linux-kernel - [PATCH v2 4/5] tools bpf_jit_disasm: Fix compilation error with new binutils

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Date:   Sun,  3 Jul 2022 14:25:50 -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>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH v2 4/5] tools bpf_jit_disasm: Fix compilation error with new binutils

binutils changed the signature of init_disassemble_info(), which now causes
compilation to fail for tools/bpf/bpf_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 bpf_jit_disasm can still disassemble bpf programs, both
with the old and new dis-asm.h API. With old binutils there's no change in
output before/after this patch. 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:
   f4:	mov    %r14,%rsi
   f7:	mov    %r15,%rdx
   fa:	mov    $0x2a,%ecx
-  ff:	callq  0xffffffffea8c4988
+  ff:	call   0xffffffffea8c4988
  104:	test   %rax,%rax
  107:	jge    0x0000000000000110
  109:	xor    %eax,%eax
- 10b:	jmpq   0x0000000000000073
+ 10b:	jmp    0x0000000000000073
  110:	cmp    $0x16,%rax

However, I had to use an older kernel to generate the bpf_jit_enabled = 2
output, as that has been broken since 5.18 / 1022a5498f6f:
https://lore.kernel.org/20220703030210.pmjft7qc2eajzi6c@alap3.anarazel.de

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
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/Makefile         | 7 +++++--
 tools/bpf/bpf_jit_disasm.c | 5 ++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/Makefile b/tools/bpf/Makefile
index b11cfc86a3d0..9c4e61c3a92b 100644
--- a/tools/bpf/Makefile
+++ b/tools/bpf/Makefile
@@ -34,8 +34,8 @@ else
 endif
 
 FEATURE_USER = .bpf
-FEATURE_TESTS = libbfd disassembler-four-args
-FEATURE_DISPLAY = libbfd disassembler-four-args
+FEATURE_TESTS = libbfd disassembler-four-args disassembler-init-styled
+FEATURE_DISPLAY = libbfd disassembler-four-args disassembler-init-styled
 
 check_feat := 1
 NON_CHECK_FEAT_TARGETS := clean bpftool_clean runqslower_clean resolve_btfids_clean
@@ -56,6 +56,9 @@ endif
 ifeq ($(feature-disassembler-four-args), 1)
 CFLAGS += -DDISASM_FOUR_ARGS_SIGNATURE
 endif
+ifeq ($(feature-disassembler-init-styled), 1)
+CFLAGS += -DDISASM_INIT_STYLED
+endif
 
 $(OUTPUT)%.yacc.c: $(srctree)/tools/bpf/%.y
 	$(QUIET_BISON)$(YACC) -o $@ -d $<
diff --git a/tools/bpf/bpf_jit_disasm.c b/tools/bpf/bpf_jit_disasm.c
index c8ae95804728..a90a5d110f92 100644
--- a/tools/bpf/bpf_jit_disasm.c
+++ b/tools/bpf/bpf_jit_disasm.c
@@ -28,6 +28,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <limits.h>
+#include <tools/dis-asm-compat.h>
 
 #define CMD_ACTION_SIZE_BUFFER		10
 #define CMD_ACTION_READ_ALL		3
@@ -64,7 +65,9 @@ static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
 	assert(bfdf);
 	assert(bfd_check_format(bfdf, bfd_object));
 
-	init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
+	init_disassemble_info_compat(&info, stdout,
+				     (fprintf_ftype) fprintf,
+				     fprintf_styled);
 	info.arch = bfd_get_arch(bfdf);
 	info.mach = bfd_get_mach(bfdf);
 	info.buffer = image;
-- 
2.37.0.3.g30cc8d0f14