linux-kernel - Re: [PATCH v9 23/42] Documentation/x86: Add CET shadow stack description

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Message-ID: <ZKa+QFKHSyqMlriG@arm.com>
Date:   Thu, 6 Jul 2023 14:14:40 +0100
From:   "szabolcs.nagy@....com" <szabolcs.nagy@....com>
To:     Mark Brown <broonie@...nel.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v9 23/42] Documentation/x86: Add CET shadow stack
 description

The 07/05/2023 20:29, Mark Brown wrote:
> On Wed, Jul 05, 2023 at 07:17:25PM +0000, Edgecombe, Rick P wrote:
> 
> > Ah, interesting, thanks for the extra info. So which features is glibc
> > planning to use? (probably more of a question for Szabolcs). Are push
> > and pop controllable separately?
> 
> Push and pop are one control, you get both or neither.
> 
> I'll defer to Szabolcs on glibc plans.

gcspopm is always available (esentially *ssp++, this is used
for longjmp).

i haven't planned anything yet for other modes (i dont know
anything where writable shadow stack is better than just
turning the feature off, so i expect we at most have a
glibc tunable env var to enable it but it will not affect
glibc behaviour otherwise).