linux-kernel - Re: [RFC PATCH] Fix: x86 unaligned _

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Message-ID: <CA+55aFy8Mc2RMtLeEt48ckufVQQE7MtTntg80wRyG3UF6ajiYA@mail.gmail.com>
Date:	Wed, 24 Jun 2015 17:37:54 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory

On Wed, Jun 24, 2015 at 4:54 PM, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com> wrote:
>
> OK, see below. This time the fault occurred at an unaligned address.
> It fails on the !pte_present(*pte_ref) check.

So every time, %rcx is 0x001fb.

Once, your rdx value (which is remaining bytes after the movsq) was 3,
the other two times it's 0.

What's so magical about that 4056-byte copy (+3 bytes once)? Are you
*sure* that copy is valid?

                   Linus
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