From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>,
Delyan Kratunov <delyank@fb.com>
Subject: [PATCH bpf-next v2] libbpf: fix build issue with llvm-readelf
Date: Fri, 4 Feb 2022 13:43:55 -0800 [thread overview]
Message-ID: <20220204214355.502108-1-yhs@fb.com> (raw)
There are cases where clang compiler is packaged in a way
readelf is a symbolic link to llvm-readelf. In such cases,
llvm-readelf will be used instead of default binutils readelf,
and the following error will appear during libbpf build:
Warning: Num of global symbols in
/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/build/libbpf/sharedobjs/libbpf-in.o (367)
does NOT match with num of versioned symbols in
/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.so libbpf.map (383).
Please make sure all LIBBPF_API symbols are versioned in libbpf.map.
--- /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/build/libbpf/libbpf_global_syms.tmp ...
+++ /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/build/libbpf/libbpf_versioned_syms.tmp ...
@@ -324,6 +324,22 @@
btf__str_by_offset
btf__type_by_id
btf__type_cnt
+LIBBPF_0.0.1
+LIBBPF_0.0.2
+LIBBPF_0.0.3
+LIBBPF_0.0.4
+LIBBPF_0.0.5
+LIBBPF_0.0.6
+LIBBPF_0.0.7
+LIBBPF_0.0.8
+LIBBPF_0.0.9
+LIBBPF_0.1.0
+LIBBPF_0.2.0
+LIBBPF_0.3.0
+LIBBPF_0.4.0
+LIBBPF_0.5.0
+LIBBPF_0.6.0
+LIBBPF_0.7.0
libbpf_attach_type_by_name
libbpf_find_kernel_btf
libbpf_find_vmlinux_btf_id
make[2]: *** [Makefile:184: check_abi] Error 1
make[1]: *** [Makefile:140: all] Error 2
The above failure is due to different printouts for some ABS
versioned symbols. For example, with the same libbpf.so,
$ /bin/readelf --dyn-syms --wide tools/lib/bpf/libbpf.so | grep "LIBBPF" | grep ABS
134: 0000000000000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.5.0
202: 0000000000000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.6.0
...
$ /opt/llvm/bin/readelf --dyn-syms --wide tools/lib/bpf/libbpf.so | grep "LIBBPF" | grep ABS
134: 0000000000000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.5.0@@LIBBPF_0.5.0
202: 0000000000000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.6.0@@LIBBPF_0.6.0
...
The binutils readelf doesn't print out the symbol LIBBPF_* version and llvm-readelf does.
Such a difference caused libbpf build failure with llvm-readelf.
The proposed fix filters out all ABS symbols as they are not part of the comparison.
This works for both binutils readelf and llvm-readelf.
Reported-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
tools/lib/bpf/Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index f947b61b2107..b8b37fe76006 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -131,7 +131,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \
sort -u | wc -l)
VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
sed 's/\[.*\]//' | \
- awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
+ awk '/GLOBAL/ && /DEFAULT/ && !/UND|ABS/ {print $$NF}' | \
grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
CMD_TARGETS = $(LIB_TARGET) $(PC_FILE)
@@ -194,7 +194,7 @@ check_abi: $(OUTPUT)libbpf.so $(VERSION_SCRIPT)
sort -u > $(OUTPUT)libbpf_global_syms.tmp; \
readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
sed 's/\[.*\]//' | \
- awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
+ awk '/GLOBAL/ && /DEFAULT/ && !/UND|ABS/ {print $$NF}'| \
grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | \
sort -u > $(OUTPUT)libbpf_versioned_syms.tmp; \
diff -u $(OUTPUT)libbpf_global_syms.tmp \
--
2.30.2
next reply other threads:[~2022-02-04 21:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 21:43 Yonghong Song [this message]
2022-02-05 2:30 ` [PATCH bpf-next v2] libbpf: fix build issue with llvm-readelf patchwork-bot+netdevbpf
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