linux-kernel - Re: [PATCH] x86: add a crc32 checksum to the kernel image.

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Message-ID: <47A26680.6060500@zytor.com>
Date:	Thu, 31 Jan 2008 16:23:28 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ian Campbell <ijc@...lion.org.uk>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] x86: add a crc32 checksum to the kernel image.

H. Peter Anvin wrote:
> 
> Hm.  I have some minor concerns about this:
> 
> * The classical length field is only available in multiples of 16 (I 
> realize your patches change that to some degree, but I'd hate to make 
> the guarantee that the image payload is the last thing in the image -- 
> it loses flexibility for the future.)  The end of the image isn't 
> available in all cases, so this would require padding it out to a 
> 16-byte boundary before appending the CRC32.  An mmap is guaranteed to 
> be zero-padded out to the next page boundary, so explicitly rounding sz 
> up (instead of when calculating sys_size) should do the job.
> 

Thinking about this more carefully, we should probably have it rounded 
up to a 16-byte boundary *including* the CRC32, so the CRC32 is included 
in the notional image.

	-hpa
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