• Tony Ambardar's avatar
    tools/libbpf: Avoid counting local symbols in ABI check · 746f534a
    Tony Ambardar authored
    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: 306b267c ("libbpf: Verify versioned symbols")
    Signed-off-by: default avatarTony Ambardar <Tony.Ambardar@gmail.com>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
    Link: https://lore.kernel.org/bpf/20200905214831.1565465-1-Tony.Ambardar@gmail.com
    746f534a
Makefile 10.4 KB