linux-kernel - RE: [PATCH 3/4] driver: provide sysfs interfaces to access TXT log

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Date:	Thu, 9 May 2013 08:05:25 +0000
From:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	"Wei, Gang" <gang.wei@...el.com>
Subject: RE: [PATCH 3/4] driver: provide sysfs interfaces to access TXT log

On 2013-05-08, Matthew Garrett wrote:
> On Tue, 2013-05-07 at 22:55 +0800, Qiaowei Ren wrote:
> 
>> +What:		/sys/devices/platform/intel_txt/log/log_header
>> +Date:		May 2013
>> +KernelVersion:	3.9
> 
> How different are these logs to the TPM measurements exported via
> securityfs?

These logs come from tboot (Trusted Boot, an open source, pre-kernel/VMM module that uses Intel® Trusted Execution Technology (Intel® TXT) to perform a measured and verified launch of an OS kernel/VMM.), and should be different from those TPM measurements (from BIOS?) exported via security.

>> +What:		/sys/devices/platform/intel_txt/log/block_index
>> +Date:		May 2013
>> +KernelVersion:	3.9
>> +Contact:	"Qiaowei Ren" <qiaowei.ren@...el.com>
>> +Description:	The "block_index" property allows you to set the block
>> +		index for output.
> 
> So I write a value here and then I see different chunks of log? This
> doesn't seem like an optimal interface. What do these logs actually
> contain? How do I know which block I should be reading?

Yes. Since total log size is bigger than one page 4K, the log have to be displayed in 4K-block indexed by block_index.
These logs will be very helpful for txt related debugging.

Thanks,
Qiaowei