On Wed, Feb 14, 2018 at 11:48:38AM -0800, Kees Cook wrote:

On Wed, Feb 14, 2018 at 11:06 AM, Laura Abbott [off-list ref] wrote:

quoted

fixed. Modules yes are not fully protected. The conclusion from past
experience has been that we cannot safely break down larger page sizes
at runtime like x86 does. We could theoretically
add support for fixing up the alias if PAGE_POISONING is enabled but
I don't know who would actually use that in production. Performance
is very poor at that point.

XPFO forces 4K pages on the physmap[1] for similar reasons. I have no
doubt about performance changes, but I'd be curious to see real
numbers. Did anyone do benchmarks on just the huge/4K change? (Without
also the XPFO overhead?)

If this, XPFO, and PAGE_POISONING all need it, I think we have to
start a closer investigation. :)

I haven't but it shouldn't be too hard. What benchmarks are you
thinking?

Tycho
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