Re: [PATCH v3 21/36] arm64/mm: Implement map_shadow_stack()

From: Mark Brown
Date: Fri Aug 04 2023 - 09:38:51 EST

On Wed, Aug 02, 2023 at 05:27:54PM +0100, Mark Brown wrote:
> On Tue, Aug 01, 2023 at 08:57:59PM +0000, Edgecombe, Rick P wrote:

> > To make sure we are on the same page: What I'm saying is say we do
> > something like add another flag SHADOW_STACK_SET_MARKER that means add
> > a marker at the end (making the token off by one frame). Then you can
> > just reject any flags != (SHADOW_STACK_SET_MARKER |
> > SHADOW_STACK_SET_TOKEN) value, and leave the rest of the code as is. So
> > not really implementing anything new. 

> > Then x86 could use the same flag meanings if/when it implements end
> > markers. If it doesn't seem worth it, it's not a big deal on my end.
> > Just seemed that they were needlessly diverging.

> Yes, my understanding of the flags is the same. I'll definitely
> implement omitting the cap since there's an actual use case for that
> (extending an existing stack, it's marginally safer to not have any
> opportunity to pivot into the newly allocated region).

BTW are you planning to repost the series for this release? We're
almost at -rc5 which is pretty late and I didn't see anything yet. It
looks like there's a branch in tip that's getting some updates but it's
not getting merged for -next.

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