Re: [PATCH v4 03/10] objtool: Handle different entry size of rodata

[Tiezhu Yang]

On 11/26/2024 03:02 PM, Josh Poimboeuf wrote:
> On Fri, Nov 22, 2024 at 12:49:58PM +0800, Tiezhu Yang wrote:
> > @@ -2107,8 +2112,15 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
> >  		if (reloc != table && reloc == next_table)
> >  			break;
> >
> > +		/* Handle the special cases compiled with Clang on LoongArch */
>
> This comment is not helpful at all.  A comment is only needed if the
> code is not already obvious.  In that case it should describe what is
> being done and why.

Will remove it.

> > +		if (file->elf->ehdr.e_machine == EM_LOONGARCH &&
> > +		    reloc_type(reloc) == R_LARCH_32_PCREL)
> > +			rodata_entry_size = 4;
> > +		else
> > +			rodata_entry_size = 8;
>
> Is this really loongarch-specific or is it only related to the size of
> the reloc?

This is related with the reloc type, but it may be wrong to only
check the reloc type to assign the value of rodata_entry_size,
becasue the value of reloc type for different archs may be same,
so it needs to check ehdr.e_machine and relocation type.

> Can this be abstracted out to a reloc_size() function like
> so?
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/tree/tools/objtool/klp-diff.c?h=objtool-diff#n834
>
> maybe it could live in elf.h.

OK, if I understand your comment correctly, this should be an
arch-specific function defined in 
tools/objtool/arch/*/include/arch/elf.h, otherwise it also needs to 
check ehdr.e_machine
in tools/objtool/include/objtool/elf.h.

Thanks,
Tiezhu