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Date: Tue, 6 Feb 2018 14:52:59 -0800
From: Linus Torvalds <>
To: Dan Williams <>
Cc: Andy Lutomirski <>, Luis Henriques <>, 
	Linux Kernel Mailing List <>, linux-arch <>, 
	Kernel Hardening <>, Greg KH <>, 
	X86 ML <>, Ingo Molnar <>, "H. Peter Anvin" <>, 
	Thomas Gleixner <>, Andrew Morton <>, 
	Alan Cox <>
Subject: Re: [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read
 under speculation

On Tue, Feb 6, 2018 at 1:37 PM, Dan Williams <> wrote:
> At that point we're basically just back to the array_ptr() version
> that returned a sanitized pointer to an array element.

.. that one does an extra unnecessary 'andq' instead of the duplicated
cmp.  But at least it avoids comparing that 32-bit integer twice, so
it's probably slightly smaller.

(And your code generation is without the "r" -> "ir" fix for the size argument)

Probably doesn't matter. But a "asm goto" would give you at least
potentially optimal code.


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