Re: rep movsb vs. simpler instructions for memcpy/memmove

On Thu, 13 Mar 2025 23:25:23 +0000, Scott Lurndal wrote:

Stefan Monnier <monnier@iro.umontreal.ca> writes:

Scott Lurndal [2025-03-13 21:42:25] wrote:

Michael S <already5chosen@yahoo.com> writes:

On Thu, 13 Mar 2025 19:35:33 +0000
mitchalsup@aol.com (MitchAlsup1) wrote:

Using MTRRs one can switch the kind of memory
to and from point in the middle of a REP MOVs.

How exactly?

The REP MOV straddles the boundary between two MTRRs.

>
Why/when would this happen in practice?
>

Nobody said it was a good idea.

I can envision an attack strategy using this to "confuse"
someone in the higher privilege levels of the "system"