[PATCH 0/4] gas: Add support for LLVM addrsig and addrsig_sym.

[Fangrui Song]

On Wed, May 25, 2022 at 12:34 AM Alan Modra <amodra@gmail.com> wrote:
>
> On Wed, May 25, 2022 at 12:19:24AM -0700, Fangrui Song wrote:
> > I have to be fair, the design of SHT_LLVM_ADDRSIG has a major problem
> > that it does not work with objcopy and ld -r:
>
> So, discard the section on ld -r and objcopy if symbols change?

In llvm-project, llvm-objcopy does not recognize/discard SHT_LLVM_ADDRSIG.
Both GNU objcopy and llvm-objcopy will set sh_link to 0 for the
unrecognized section.

ld.lld --icf=safe prints a warning [1] for SHT_LLVM_ADDRSIG when
sh_link==0 (--icf=all does not need SHT_LLVM_ADDRSIG).
The users I need to serve use -Wl,--fatal-warnings to convert warnings
to errors, so we need to do   `objcopy --remove-section=.llvm_addrsig`
in a few places.

objcopy discarding SHT_LLVM_ADDRSIG would be more ergonomic, but it
raises a question whether it is better for the user to be aware of the
problem and discard the section by themselves.

[1]: https://github.com/llvm/llvm-project/blob/main/lld/test/ELF/icf-safe.s#L92