On Fri, Feb 4, 2022 at 1:13 PM Yonghong Song <yhs@xxxxxx> wrote:
>
> 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.
>
> To fix the issue, let us do proper filtering for LIBBPF_*@@LIBBPF_* symbols.
> The proposed fix works for both binutils readelf and llvm-readelf.
>
> Reported-by: Delyan Kratunov <delyank@xxxxxx>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> tools/lib/bpf/Makefile | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index f947b61b2107..d1577c26c16b 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -132,7 +132,8 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \
> VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> sed 's/\[.*\]//' | \
> awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
have you tried just doing !/UND|ABS/ here?
> - grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
> + grep -Eo '[^ ]+@LIBBPF_' | grep -Ev '^LIBBPF_' | \
> + cut -d@ -f1 | sort -u | wc -l)
>
> CMD_TARGETS = $(LIB_TARGET) $(PC_FILE)
>
> @@ -195,7 +196,8 @@ check_abi: $(OUTPUT)libbpf.so $(VERSION_SCRIPT)
> readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> sed 's/\[.*\]//' | \
> awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
> - grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | \
> + grep -Eo '[^ ]+@LIBBPF_' | grep -Ev '^LIBBPF_' | \
> + cut -d@ -f1 | \
> sort -u > $(OUTPUT)libbpf_versioned_syms.tmp; \
> diff -u $(OUTPUT)libbpf_global_syms.tmp \
> $(OUTPUT)libbpf_versioned_syms.tmp; \
> --
> 2.30.2
>
