linux-kernel - Re: [git pull] "big box" x86 changes, boot protocol

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Message-ID: <48139A35.6050608@zytor.com>
Date:	Sat, 26 Apr 2008 14:10:13 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Adrian Bunk <bunk@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai.lu@....com>,
	Yinghai Lu <yhlu.kernel@...il.com>, jbarnes@...tuousgeek.org
Subject: Re: [git pull] "big box" x86 changes, boot protocol

Adrian Bunk wrote:
>>> +	memcpy(&early_res[i], &early_res[i + 1],
>>> +	       (j - 1 - i) * sizeof(struct early_res));

>> nit: memcpy() shouldn't be used for overlapping copies.  It happens to be
>> OK (for dst<src) in the kernel implementations.  We hope.
>> ...
> 
> We always use the gcc builtin for memcpy() here.
> 

You have to do something pretty weird for memcpy() to not work for
dst <= src even with overlap; this usually involves architectures that 
have explicit cache control instructions to establish the dst in the 
cache, if used before src is read.

This is not an issue on x86, though.

	-hpa
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