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SubjectRe: [PATCH 5.8 35/99] tools/libbpf: Avoid counting local symbols in ABI check
On Tue, Sep 29, 2020 at 6:53 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> From: Tony Ambardar <tony.ambardar@gmail.com>
>
> [ Upstream commit 746f534a4809e07f427f7d13d10f3a6a9641e5c3 ]
>
> Encountered the following failure building libbpf from kernel 5.8.5 sources
> with GCC 8.4.0 and binutils 2.34: (long paths shortened)
>
> Warning: Num of global symbols in sharedobjs/libbpf-in.o (234) does NOT
> match with num of versioned symbols in libbpf.so (236). Please make sure
> all LIBBPF_API symbols are versioned in libbpf.map.
> # --- libbpf_global_syms.tmp 2020-09-02 07:30:58.920084380 +0000
> # +++ libbpf_versioned_syms.tmp 2020-09-02 07:30:58.924084388 +0000
> @@ -1,3 +1,5 @@
> +_fini
> +_init
> bpf_btf_get_fd_by_id
> bpf_btf_get_next_id
> bpf_create_map
> make[4]: *** [Makefile:210: check_abi] Error 1
>
> Investigation shows _fini and _init are actually local symbols counted
> amongst global ones:
>
> $ readelf --dyn-syms --wide libbpf.so|head -10
>
> Symbol table '.dynsym' contains 343 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 0: 00000000 0 NOTYPE LOCAL DEFAULT UND
> 1: 00004098 0 SECTION LOCAL DEFAULT 11
> 2: 00004098 8 FUNC LOCAL DEFAULT 11 _init@@LIBBPF_0.0.1
> 3: 00023040 8 FUNC LOCAL DEFAULT 14 _fini@@LIBBPF_0.0.1
> 4: 00000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.0.4
> 5: 00000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.0.1
> 6: 0000ffa4 8 FUNC GLOBAL DEFAULT 12 bpf_object__find_map_by_offset@@LIBBPF_0.0.1
>
> A previous commit filtered global symbols in sharedobjs/libbpf-in.o. Do the
> same with the libbpf.so DSO for consistent comparison.
>
> Fixes: 306b267cb3c4 ("libbpf: Verify versioned symbols")
> Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
> Link: https://lore.kernel.org/bpf/20200905214831.1565465-1-Tony.Ambardar@gmail.com
> Signed-off-by: Sasha Levin <sashal@kernel.org>

This seems to work everywhere else, but breaks PPC64LE.

Justin

> ---
> tools/lib/bpf/Makefile | 2 ++
> 1 file changed, 2 insertions(+)
>
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -152,6 +152,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --
> awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
> sort -u | wc -l)
> VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> + awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
> grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
>
> CMD_TARGETS = $(LIB_TARGET) $(PC_FILE)
> @@ -219,6 +220,7 @@ check_abi: $(OUTPUT)libbpf.so
> awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
> sort -u > $(OUTPUT)libbpf_global_syms.tmp; \
> readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> + awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
> grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | \
> sort -u > $(OUTPUT)libbpf_versioned_syms.tmp; \
> diff -u $(OUTPUT)libbpf_global_syms.tmp \
>
>

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