linux-kernel - Re: [PATCH RFC 0/3] arm64/gcs: Allow reuse of user managed shadow stacks

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Message-ID: <5c616340-2767-48f0-8727-326deebf718f@sirena.org.uk>
Date: Fri, 26 Sep 2025 17:03:43 +0100
From: Mark Brown <broonie@...nel.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "yury.khrustalev@....com" <yury.khrustalev@....com>,
	"adhemerval.zanella@...aro.org" <adhemerval.zanella@...aro.org>,
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	"libc-alpha@...rceware.org" <libc-alpha@...rceware.org>
Subject: Re: [PATCH RFC 0/3] arm64/gcs: Allow reuse of user managed shadow
 stacks

On Fri, Sep 26, 2025 at 03:39:46PM +0000, Edgecombe, Rick P wrote:
> On Fri, 2025-09-26 at 16:07 +0100, Yury Khrustalev wrote:

> > What do you mean by "a fuller solution from the glibc side"? A
> > solution
> > for re-using shadow stacks? 

> I mean some code or a fuller explained solution that uses this new
> kernel functionality. I think the scheme that Florian suggested in the
> thread linked above (longjmp() to the start of the stack) will have
> trouble if the thread pivots to a new shadow stack before exiting (e.g.
> ucontext).

Is that supported even without user managed stacks?

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