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libbpf: Fix build issue with llvm-readelf

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[ Upstream commit 0908a66ad1124c1634c33847ac662106f7f2c198 ]

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>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220204214355.502108-1-yhs@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Yonghong Song 2022-02-04 13:43:55 -08:00 committed by Greg Kroah-Hartman
parent 26a1e4739e
commit 5baf92a2c4
1 changed files with 2 additions and 2 deletions
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4
tools/lib/bpf/Makefile
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@ -147,7 +147,7 @@ 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)
@ -216,7 +216,7 @@ 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 \