[ 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>
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