linux-kernel - Re: [PATCH] ARM: fix memset64() on big-endian

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Message-ID: <aVfirJvsYt0-jDRD@casper.infradead.org>
Date: Fri, 2 Jan 2026 15:22:20 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Russell King <linux@...linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <rmk+kernel@...linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, stable@...r.kernel.org
Subject: Re: [PATCH] ARM: fix memset64() on big-endian

On Fri, Jan 02, 2026 at 08:15:46AM +0100, Thomas Weißschuh wrote:
> On big-endian systems the 32-bit low and high halves need to be swapped,
> for the underlying assembly implemenation to work correctly.

Heh.  In my heart, ARM will always be a litte-endian architecture.
I'm not really surprised this bug took, er, 8 years to show up; big-endian
arm is rare enough and memset64() isn't much used on 32-bit systems.
And it turns out that many of the users pass a constant 0 as the value,
which was kind of not the point, but it seems to be an easier API to
use than memset, so whatever ;-)

> Fixes: fd1d362600e2 ("ARM: implement memset32 & memset64")
> Cc: stable@...r.kernel.org
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>