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From: Thomas Gleixner <tglx@linutronix.de>
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To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: LKML <linux-kernel@vger.kernel.org>, Linus Torvalds
 <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>,
 kernel test robot <lkp@intel.com>, linux-arm-kernel@lists.infradead.org,
 Nathan Chancellor <nathan@kernel.org>, Christophe Leroy
 <christophe.leroy@csgroup.eu>, Darren Hart <dvhart@infradead.org>,
 Davidlohr Bueso <dave@stgolabs.net>, =?utf-8?Q?Andr=C3=A9?= Almeida
 <andrealmeid@igalia.com>, x86@kernel.org, Alexander Viro
 <viro@zeniv.linux.org.uk>, Christian Brauner <brauner@kernel.org>, Jan
 Kara <jack@suse.cz>, linux-fsdevel@vger.kernel.org
Subject: Re: [patch V2 1/6] ARM: uaccess: Implement missing
 __get_user_asm_dword()
In-Reply-To: <aMrREvFIXlZc1W5k@shell.armlinux.org.uk>
References: <aMnV-hAwRnLJflC7@shell.armlinux.org.uk> <875xdhaaun.ffs@tglx>
 <aMqCPVmOArg8dIqR@shell.armlinux.org.uk> <87y0qd89q9.ffs@tglx>
 <aMrREvFIXlZc1W5k@shell.armlinux.org.uk>
Date: Wed, 17 Sep 2025 20:44:12 +0200
Message-ID: <87plbo9awz.ffs@tglx>
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On Wed, Sep 17 2025 at 16:17, Russell King wrote:
> On Wed, Sep 17, 2025 at 03:55:10PM +0200, Thomas Gleixner wrote:
>> But it actually can be solved solvable by switching the casting to:
>> 
>>     (x) = *(__force __typeof__(*(ptr)) *) &__gu_val;
>> 
>> Not pretty, but after upping the frame size limit it builds an
>> allmodconfig kernel.
>
> For me, this produces:
>
> get-user-test.c:41:16: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>    41 |         (x) = *(__force __typeof__(*(ptr)) *) &__gu_val;                \
>       |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> with arm-linux-gnueabihf-gcc (Debian 14.2.0-19) 14.2.0
>
> Maybe you're using a different compiler that doesn't issue that
> warning?

Yes :)

Was this with the one-line change or with the full conversion?

Thanks,

        tglx