linux-kernel - RE: load_unaligned

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Date:   Sat, 14 Nov 2020 23:17:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: load_unaligned_zeropad() on x86-64

From: Linus Torvalds
> Sent: 14 November 2020 18:02
> 
> On Sat, Nov 14, 2020 at 7:53 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > The change e419b4cc585680940bc42f8ca8a071d6023fb1bb added
> > asm code for load_unaligned_zeropad().
> >
> > However it doesn't look right for 64bit.
> > It masks the address with ~3 not ~7 so the second
> > access could still cross a page boundary and fault.
> 
> Can you explain more what you think is wrong?
> 
> It uses
> 
>                 "and %3,%1\n\t"
> 
> for the masking, but note how that's a "%3", not a "$3".

Maybe I need to get better glasses.

	David

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