Re: [PATCH v2 18/62] objtool: Fix x86 addend calculation

[Peter Zijlstra]

On Fri, May 09, 2025 at 01:16:42PM -0700, Josh Poimboeuf wrote:
> On x86, arch_dest_reloc_offset() hardcodes the addend adjustment to
> four, but the actual adjustment depends on the relocation type.  Fix
> that.

> +s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
>  {
> -	return addend + 4;
> +	s64 addend = reloc_addend(reloc);
> +
> +	switch (reloc_type(reloc)) {
> +	case R_X86_64_PC32:
> +	case R_X86_64_PLT32:
> +		addend += insn->offset + insn->len - reloc_offset(reloc);
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return addend;
>  }

Should this not be something like:

s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
{
	s64 addend = reloc_addend(reloc);

	if (arch_pc_relative_reloc(reloc))
		addend += insn->offset + insn->len - reloc_offset(reloc);

	return addend;
}

instead?

AFAIU arch_pc_relative_reloc() is the exact same set of relocations.