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SubjectRe: [RFC] x86/speculation: add L1 Terminal Fault / Foreshadow demo
On Mon, Jan 21, 2019 at 10:36:18AM -0800, Andi Kleen wrote:
> > + /* Check the start address: needs to be page-aligned.. */
> > +- if (start & ~PAGE_MASK)
> > ++ if (start & ~PAGE_MASK) {
> > ++
> > ++ /*
> > ++ * XXX Hack
> > ++ *
> > ++ * We re-use this error case to show case a cache load gadget:
> > ++ * There is a mispredicted branch, which leads to prefetching
> > ++ * the cache with attacker controlled data.
> > ++ */
> > ++ asm volatile (
>
> Obviously that can never be added to a standard kernel.

No, that's why it is a patch, right? People want to test things, it's
nice to have a way to easily do this.

> And I don't see much point in shipping test cases that require non
> standard kernel patching. The idea of shipping test cases is that
> you can easily test them, but in this form it can't.

It's better than having nothing at all, which is what we have today. So
I see no harm in it, only benefits.

thanks,

greg k-h

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