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

From: Andres Freund
Date: Sun Jul 03 2022 - 17:26:07 EST


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@xxxxxxxxxxxxxxxxx

Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Cc: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Link: http://lore.kernel.org/lkml/20220622181918.ykrs5rsnmx3og4sv@xxxxxxxxxxxxxxxxx
Signed-off-by: Andres Freund <andres@xxxxxxxxxxx>
---
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