From 746f534a4809e07f427f7d13d10f3a6a9641e5c3 Mon Sep 17 00:00:00 2001

From: Tony Ambardar <tony.ambardar@gmail.com>

Date: Sat, 5 Sep 2020 14:48:31 -0700

Subject: [PATCH] tools/libbpf: Avoid counting local symbols in ABI check

Encountered the following failure building libbpf from kernel 5.8.5 sources

with GCC 8.4.0 and binutils 2.34: (long paths shortened)

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

---

 tools/lib/bpf/Makefile | 2 ++

 1 file changed, 2 insertions(+)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile

index b78484e7a608..9ae8f4ef0aac 100644

--- a/tools/lib/bpf/Makefile

+++ b/tools/lib/bpf/Makefile

@@ -152,6 +152,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \

 			   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			 \

-- 

2.28.0