[PATCH 2/2] x86/APX: support JMPABS also in assembler

[Hu, Lin1]

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: Thursday, October 10, 2024 3:05 PM
> To: Hu, Lin1 <lin1.hu@intel.com>
> Cc: Binutils <binutils@sourceware.org>; Cui, Lili <lili.cui@intel.com>; H.J. Lu
> <hjl.tools@gmail.com>
> Subject: Re: [PATCH 2/2] x86/APX: support JMPABS also in assembler
> 
> On 10.10.2024 03:53, Hu, Lin1 wrote:
> > I don't think linker currently supports the following forms:
> > label:
> > 	...
> > 	jmpabs label
> 
> Why would it not support this? It doesn't care at all what insn it is; all
> it cares about is the associated relocation (R_X86_64_64 for ELF). And ...
>

I'm not familiar with this part. Does assembler definitely generate R_X86_64_64 rather than R_X86_64_GOTOFF64 or R_X86_64_PLTOFF64?
 
>
> > Same thing we discussed earlier, it's pointless to support this format now. And
> for the form that uses label, maybe we can consider let linker to convert 'jmp
> label''s encoding to jmpabs's. For gas, even if the likelihood of a new instruction
> like 'jmpabs 0x521515' appearing is small, that's no reason for us to accept this
> usage; we think it's safer to let the linker support it.
> 
> ... how does the linker come into the picture here in the first place?
> 

We think it's safer to extend the 'jmp label' functionality in the linker without any conflict with the documentation.

BRs,
Lin