Re: [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW

[Pawan Gupta]

On Wed, Oct 25, 2023 at 08:56:10AM +0200, Peter Zijlstra wrote:
> > config3: 32-bit mode, pre-boot objdump
> > 
> > entry_SYSENTER_32:
> >    ...
> >    c8e:       58                      pop    %eax
> >    c8f:       90                      nop
> >    c90:       90                      nop
> >    c91:       90                      nop
> >    c92:       90                      nop
> >    c93:       90                      nop
> >    c94:       90                      nop
> >    c95:       90                      nop
> >    c96:       fb                      sti
> >    c97:       0f 35                   sysexit
> > 
> 
> If you look at arch/x86/include/asm/nops.h, you'll find (for 32bit):
> 
>  * 7: leal 0x0(%esi,%eiz,1),%esi
> 
> Which reads as:
> 
> 	load-effective-address of %esi[0] into %esi

Wow, never imagined that this would be one of the magician's trick. I
will go read on why is it better than NOPL.