On Thu, Jun 17, 2021 at 12:28:00AM +0200, Mark Wielaard wrote: > Hoi, > > On Wed, Jun 16, 2021 at 06:38:33PM +0200, Jiri Olsa wrote: > > > > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c > > > > index d636643ddd35..f32c059fbfb4 100644 > > > > --- a/tools/bpf/resolve_btfids/main.c > > > > +++ b/tools/bpf/resolve_btfids/main.c > > > > @@ -649,6 +649,9 @@ static int symbols_patch(struct object *obj) > > > > if (sets_patch(obj)) > > > > return -1; > > > > + /* Set type to ensure endian translation occurs. */ > > > > + obj->efile.idlist->d_type = ELF_T_WORD; > > > > > > The change makes sense to me as .BTF_ids contains just a list of > > > u32's. > > > > > > Jiri, could you double check on this? > > > > the comment in ELF_T_WORD declaration suggests the size depends on > > elf's class? > > > > ELF_T_WORD, /* Elf32_Word, Elf64_Word, ... */ > > > > data in .BTF_ids section are allways u32 > > > > I have no idea how is this handled in libelf (perhaps it's ok), > > but just that comment above suggests it could be also 64 bits, > > cc-ing Frank and Mark for more insight > > It is correct to use ELF_T_WORD, which means a 32bit unsigned word. > > The comment is meant to explain that, but is really confusing if you > don't know that Elf32_Word and Elf64_Word are the same thing (a 32bit > unsigned word). This comes from being "too consistent" in defining all > data types for both 32bit and 64bit ELF, even if those types are the > same in both formats... > > Only Elf32_Addr/Elf64_Addr and Elf32_Off/Elf64_Off are different > sizes. But Elf32/Elf_64_Half (16 bit), Elf32/Elf64_Word (32 bit), > Elf32/Elf64_Xword (64 bit) and their Sword/Sxword (signed) variants > are all identical data types in both the Elf32 and Elf64 formats. > > I don't really know why. It seems the original ELF spec was 32bit only > and when introducing the ELF64 format "they" simply duplicated all > data types whether or not those data type were actually different > between the 32 and 64 bit format. nice, thanks for details Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> jirka
