linux-kernel - Re: [PATCH] lib/decompress_unxz.c: removing all memory helper functions

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Message-ID: <4FBFBDCE.6030104@zytor.com>
Date:	Fri, 25 May 2012 10:13:50 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Thavatchai Makphaibulcboke <thavatchai.makpahibulchoke@...com>
CC:	Lasse Collin <lasse.collin@...aani.org>,
	"lethal@...ux-sh.org" <lethal@...ux-sh.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kaloz@...nwrt.org" <kaloz@...nwrt.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
	"heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
	"linux390@...ibm.com" <linux390@...ibm.com>
Subject: Re: [PATCH] lib/decompress_unxz.c: removing all memory helper functions

On 05/25/2012 10:05 AM, Thavatchai Makphaibulcboke wrote:
>> We could do that.  But according to the comment in the original
>> implementation, there seems to be a concern regarding its performance
>> speed. If you believe all archs' memcpy would give comparable
>> performance to the memmove. then I could do that.
>>
> 
> Also how about the case for overlapping buffer, especially when the
> destination is at a higher address?  I do not believe memcpy guarantee
> to work.

memcpy() is not guaranteed to work for any overlap; that is what
memmove() is for.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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