linux-kernel - Re: [patch V3 00/12] uaccess: Provide and use scopes for user masked access

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Message-ID: <20251017103755.GZ4067720@noisy.programming.kicks-ass.net>
Date: Fri, 17 Oct 2025 12:37:55 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, kernel test robot <lkp@...el.com>,
	Russell King <linux@...linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	linuxppc-dev@...ts.ozlabs.org, Paul Walmsley <pjw@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	linux-riscv@...ts.infradead.org, Heiko Carstens <hca@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Julia Lawall <Julia.Lawall@...ia.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	André Almeida <andrealmeid@...lia.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [patch V3 00/12] uaccess: Provide and use scopes for user masked
 access

On Fri, Oct 17, 2025 at 12:08:54PM +0200, Thomas Gleixner wrote:

> After some back and forth discussion Linus suggested to put the local label
> workaround into the user access functions themself.

> Andrew thankfully pointed me to nested for() loops and after some head
> scratching I managed to get all of it hidden in that construct.

These two hacks are awesome and made my day; thanks!

> Thomas Gleixner (12):
>       ARM: uaccess: Implement missing __get_user_asm_dword()
>       uaccess: Provide ASM GOTO safe wrappers for unsafe_*_user()
>       x86/uaccess: Use unsafe wrappers for ASM GOTO
>       powerpc/uaccess: Use unsafe wrappers for ASM GOTO
>       riscv/uaccess: Use unsafe wrappers for ASM GOTO
>       s390/uaccess: Use unsafe wrappers for ASM GOTO
>       uaccess: Provide scoped masked user access regions
>       uaccess: Provide put/get_user_masked()
>       futex: Convert to scoped masked user access
>       x86/futex: Convert to scoped masked user access

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

>       select: Convert to scoped masked user access

Basically okay on this one too, except see the comment.

>       coccinelle: misc: Add scoped_masked_$MODE_access() checker script

And that's just pure magic, I can't seem to get me head around
coccinelle syntax.