On 10/29/2018 11:32 PM, Yonghong Song wrote:
> With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE.
> -bash-4.4$ cat t.c
> __attribute__((section("maps"))) int g;
> -bash-4.4$ clang -target bpf -O2 -c t.c
> -bash-4.4$ readelf -s t.o
>
> Symbol table '.symtab' contains 2 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g
> -bash-4.4$
>
> The following llvm commit enables BPF target to generate
> proper symbol type and size.
> commit bf6ec206615b9718869d48b4e5400d0c6e3638dd
> Author: Yonghong Song <y...@fb.com>
> Date: Wed Sep 19 16:04:13 2018 +0000
>
> [bpf] Symbol sizes and types in object file
>
> Clang-compiled object files currently don't include the symbol sizes and
> types. Some tools however need that information. For example,
> ctfconvert
> uses that information to generate FreeBSD's CTF representation from ELF
> files.
> With this patch, symbol sizes and types are included in object files.
>
> Signed-off-by: Paul Chaignon <paul.chaig...@orange.com>
> Reported-by: Yutaro Hayakawa <yhayakawa3...@gmail.com>
>
> Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but
> OBJECT.
> -bash-4.4$ clang -target bpf -O2 -c t.c
> -bash-4.4$ readelf -s t.o
>
> Symbol table '.symtab' contains 3 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c
> 2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g
> -bash-4.4$
>
> This patch makes sure bpf library accepts both NOTYPE and OBJECT types
> of global map symbols.
>
> Signed-off-by: Yonghong Song <y...@fb.com>
Thanks!
Acked-by: Daniel Borkmann <dan...@iogearbox.net>
