Subject: Re: [RFC PATCH net-next] tools/bpf: fix build with binutils >= 2.28

From: Roman Gushchin <[email-masked]>
Date: Wed, 20 Dec 2017 18:32:36 +0000

On Tue, Dec 19, 2017 at 04:22:51PM +0000, Quentin Monnet wrote:
> 2017-12-19 16:10 UTC+0000 ~ Roman Gushchin <[email-masked]>
> > On Tue, Dec 19, 2017 at 03:57:02PM +0000, Quentin Monnet wrote:
> >> Hi Roman, thanks for working on this!
> >>
> >>
> >> I discussed this issue with Jakub recently, and one suggestion he had
> >> was to look in tools/build/feature to add a new "feature", by trying to
> >> compile short programs, for making the distinction between binutils
> >> versions. It probably requires more work, but could be more robust than
> >> parsing the version from the command line?
> > 
> > Hm, might be an option. Parsing readelf output is pretty ugly, here I agree.
> > In general it feels more like a binutils issue, so we have to workaround it
> > in either way.
> > 
> > Is Jakub or someone else working on it?
> > 
> > Thanks!
> > 
> 
> Jakub isn't. On our side, I noticed last week that there was this change
> in binutils, and started to have a look at how these "features" work.
> But I have nothing that works so far, so feel free to tackle this.
> 
> Quentin

Hi Quentin!

Can you, please, check that the patch below works in your environment.

Thanks!

--

>>From b08deabf42e4c143b9e0eec8c49714e4d2c928e3 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <[email-masked]>
Date: Wed, 20 Dec 2017 13:27:32 +0000
Subject: [RFC PATCH net-next] tools/bpftool: fix bpftool build with bintutils
 >= 2.8

Bpftool build is broken with binutils version 2.28 and later.
The cause is commit 003ca0fd2286 ("Refactor disassembler selection")
in the binutils repo, which changed the disassembler() function
signature.

Fix this by adding a new "feature" to the tools/build/features
infrastructure and make it responsible for decision which
disassembler() function signature to use.

Signed-off-by: Roman Gushchin <[email-masked]>
Cc: Jakub Kicinski <[email-masked]>
Cc: Alexei Starovoitov <[email-masked]>
Cc: Daniel Borkmann <[email-masked]>
---
 tools/bpf/Makefile                      | 18 ++++++++++++++++++
 tools/bpf/bpf_jit_disasm.c              |  7 +++++++
 tools/bpf/bpftool/Makefile              | 13 +++++++++++++
 tools/bpf/bpftool/jit_disasm.c          |  7 +++++++
 tools/build/feature/Makefile            |  4 ++++
 tools/build/feature/test-disassembler.c | 15 +++++++++++++++
 6 files changed, 64 insertions(+)
 create mode 100644 tools/build/feature/test-disassembler.c

diff --git a/tools/bpf/Makefile b/tools/bpf/Makefile
index 07a6697466ef..c62b3a311486 100644
--- a/tools/bpf/Makefile
+++ b/tools/bpf/Makefile
@@ -9,6 +9,24 @@ MAKE = make
 CFLAGS += -Wall -O2
 CFLAGS += -D__EXPORTED_HEADERS__ -I../../include/uapi -I../../include
 
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(CURDIR)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+FEATURE_TESTS = disassembler
+FEATURE_DISPLAY = disassembler
+
+ifeq ($(FEATURES_DUMP),)
+include $(srctree)/tools/build/Makefile.feature
+else
+include $(FEATURES_DUMP)
+endif
+
+ifeq ($(feature-disassembler), 1)
+CFLAGS += -DNEW_DISSASSEMBLER_SIGNATURE
+endif
+
 %.yacc.c: %.y
 	$(YACC) -o $@ -d $<
 
diff --git a/tools/bpf/bpf_jit_disasm.c b/tools/bpf/bpf_jit_disasm.c
index 75bf526a0168..a5f4dbacdb11 100644
--- a/tools/bpf/bpf_jit_disasm.c
+++ b/tools/bpf/bpf_jit_disasm.c
@@ -72,7 +72,14 @@ static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
 
 	disassemble_init_for_target(&info);
 
+#ifdef NEW_DISSASSEMBLER_SIGNATURE
+	disassemble = disassembler(bfd_get_arch(bfdf),
+				   bfd_big_endian(bfdf),
+				   bfd_get_mach(bfdf),
+				   bfdf);
+#else
 	disassemble = disassembler(bfdf);
+#endif
 	assert(disassemble);
 
 	do {
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 3f17ad317512..9c089cfa5f3f 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -43,6 +43,19 @@ LIBS = -lelf -lbfd -lopcodes $(LIBBPF)
 INSTALL ?= install
 RM ?= rm -f
 
+FEATURE_TESTS = disassembler
+FEATURE_DISPLAY = disassembler
+
+ifeq ($(FEATURES_DUMP),)
+include $(srctree)/tools/build/Makefile.feature
+else
+include $(FEATURES_DUMP)
+endif
+
+ifeq ($(feature-disassembler), 1)
+CFLAGS += -DNEW_DISSASSEMBLER_SIGNATURE
+endif
+
 include $(wildcard *.d)
 
 all: $(OUTPUT)bpftool
diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c
index 1551d3918d4c..8295e2f14ed7 100644
--- a/tools/bpf/bpftool/jit_disasm.c
+++ b/tools/bpf/bpftool/jit_disasm.c
@@ -107,7 +107,14 @@ void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes)
 
 	disassemble_init_for_target(&info);
 
+#ifdef NEW_DISSASSEMBLER_SIGNATURE
+	disassemble = disassembler(bfd_get_arch(bfdf),
+				   bfd_big_endian(bfdf),
+				   bfd_get_mach(bfdf),
+				   bfdf);
+#else
 	disassemble = disassembler(bfdf);
+#endif
 	assert(disassemble);
 
 	if (json_output)
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 96982640fbf8..91f937943918 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -13,6 +13,7 @@ FILES=                                          \
          test-hello.bin                         \
          test-libaudit.bin                      \
          test-libbfd.bin                        \
+         test-disassembler.bin                  \
          test-liberty.bin                       \
          test-liberty-z.bin                     \
          test-cplus-demangle.bin                \
@@ -188,6 +189,9 @@ $(OUTPUT)test-libpython-version.bin:
 $(OUTPUT)test-libbfd.bin:
 	$(BUILD) -DPACKAGE='"perf"' -lbfd -lz -liberty -ldl
 
+$(OUTPUT)test-disassembler.bin:
+	$(BUILD) -lopcodes
+
 $(OUTPUT)test-liberty.bin:
 	$(CC) $(CFLAGS) -Wall -Werror -o $@ test-libbfd.c -DPACKAGE='"perf"' $(LDFLAGS) -lbfd -ldl -liberty
 
diff --git a/tools/build/feature/test-disassembler.c b/tools/build/feature/test-disassembler.c
new file mode 100644
index 000000000000..45ce65cfddf0
--- /dev/null
+++ b/tools/build/feature/test-disassembler.c
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <bfd.h>
+#include <dis-asm.h>
+
+int main(void)
+{
+	bfd *abfd = bfd_openr(NULL, NULL);
+
+	disassembler(bfd_get_arch(abfd),
+		     bfd_big_endian(abfd),
+		     bfd_get_mach(abfd),
+		     abfd);
+
+	return 0;
+}
-- 
2.14.3