From: Yonghong Song yhs@fb.com
[ 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 --- tools/lib/bpf/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -147,7 +147,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s -- 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_ 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 \