Re: The trouble with __weak and objtool got worse

[Josh Poimboeuf <jpoimboe@redhat.com>]

On Fri, Apr 15, 2022 at 01:19:04PM +0200, Peter Zijlstra wrote:
> Now, if we do IBT/LTO builds, and run objtool on linked objects only,
> this obvious doesn't happen, because the weak stuff has been resolved by
> then. But ideally we'd not force that since it has a build time
> penalty..
> 
> The other option seems to be to have objtool add section symbols it
> needs, however due to ELF being a total PITA and requiring all LOCAL
> symbols to be before GLOBAL symbols, this would mean re-ordering the
> whole symbol table (I have the code somewhere :-/).
> 
> Alternatively:
> 
>   https://sourceware.org/pipermail/binutils/2020-December/114671.html
> 
> seems to suggest: -Wa,--generate-unused-section-symbols=yes, ought to
> work, except I'm getting:
> 
> $ gcc -O2 -fcf-protection=none -fno-asynchronous-unwind-tables -Wa,--generate-unused-section-symbols=yes -c foo*.c
> as: unrecognized option '--generate-unused-section-symbols=yes'
> as: unrecognized option '--generate-unused-section-symbols=yes'
> 
> $ as --version
> GNU assembler (GNU Binutils for Debian) 2.38

Can we trick the assembler into creating function symbols for all the
static call sites by having some inline asm (or _THIS_IP_) in the static
call macro with a dummy reference to a code location in the function?

-- 
Josh