Re: [PATCH v5 03/10] objtool: Handle PC relative relocation type

[Josh Poimboeuf]

On Wed, Dec 11, 2024 at 04:35:27PM -0800, Josh Poimboeuf wrote:
> On Wed, Dec 11, 2024 at 11:16:33AM +0800, Tiezhu Yang wrote:
> > When compiling on LoongArch, there are some PC relative relocation types
> > for rodata, it needs to calculate the symbol offset with "S + A - PC" in
> > this case according to the spec of "ELF for the LoongArch Architecture",
> > the "PC" is the index of each jump table which is equal with the value
> > of reloc_offset(reloc) - reloc_offset(table).
> > 
> > I will add the above description to the commit message to make it clear.
> 
> I understand how PC-relative addressing works.
> 
> The oddity here is that "PC" is the jump table's base address rather
> than the entry address.  That has nothing to do with the ELF spec or
> even how R_LARCH_32_PCREL is implemented.  Rather it seems to be a quirk
> related to how loongarch jump table code expects the entries to be.
> 
> So the arch_adjust_offset() name seems wrong, as this is specific to
> the jump table implementation, rather than relocs in general.
> 
> Instead call it arch_jump_table_sym_offset()?

BTW, do both GCC and Clang have this same behavior for loongarch?

-- 
Josh