linux-kernel - Re: [PATCH v10 23/40] arm64/signal: Set up and restore the GCS context for signal handlers

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Message-ID: <Zr4tdcj8DF92GzVS@e133380.arm.com>
Date: Thu, 15 Aug 2024 17:31:49 +0100
From: Dave Martin <Dave.Martin@....com>
To: Mark Brown <broonie@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Shuah Khan <shuah@...nel.org>,
	"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
	Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>,
	Szabolcs Nagy <Szabolcs.Nagy@....com>, Kees Cook <kees@...nel.org>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Florian Weimer <fweimer@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
	Ross Burton <ross.burton@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-mm@...ck.org,
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	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v10 23/40] arm64/signal: Set up and restore the GCS
 context for signal handlers

On Thu, Aug 15, 2024 at 04:29:54PM +0100, Mark Brown wrote:
> On Thu, Aug 15, 2024 at 04:11:56PM +0100, Dave Martin wrote:
> > On Thu, Aug 15, 2024 at 03:45:45PM +0100, Mark Brown wrote:
> > > On Thu, Aug 15, 2024 at 02:37:22PM +0100, Dave Martin wrote:
> 
> > > > Is there a test for taking and returning from a signal on an alternate
> > > > (main) stack, when a shadow stack is in use?  Sounds like something
> > > > that would be good to check if not.
> 
> > > Not specifically for any of the architectures.
> 
> > Can you see any reason why this shouldn't work?
> 
> No, it's expected to work - I'm just not specifically aware of an
> explicit test for it.  Possibly some of the userspace bringup work
> might've covered it?  Any libc tests for altstack support should've
> exercised it for example.

That's true; if libc is built to use shadow stack, generic API tests
ought to cover this.

> > Maybe I'll hacking up a test if I get around to it, but don't take this
> > as a promise!
> 
> Thanks for your firm commitment!  :P

No problem...

Cheers
---Dave