Re: [PATCH v4 2/5] x86/alternative: add indirect call patching

[Juergen Gross]

On 14.11.23 16:06, Borislav Petkov wrote:
> On Mon, Oct 30, 2023 at 03:25:05PM +0100, Juergen Gross wrote:
> > +#ifdef CONFIG_X86_64
> > +	/* ff 15 00 00 00 00   call   *0x0(%rip) */
> > +	target = *(void **)(instr + a->instrlen + *(s32 *)(instr + 2));
> > +#else
> > +	/* ff 15 00 00 00 00   call   *0x0 */
> > +	target = *(void **)(*(s32 *)(instr + 2));
>
> Yeah, let's document those a bit better. Either with comments above or
> as Peter suggests:
>
> 	/* Add 2 to skip opcode and ModRM byte: */
> 	disp32 = *(s32 *)(instr + 2);
>
> 	rip_rela_ptr = (void **)(instr + a->instrlen + disp32);
> 	target = *rip_rela_ptr;
>
> so that it is crystal clear what we're doing here.

Okay.


Juergen

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