linux-kernel - RE: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information

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Date:	Mon, 27 Oct 2014 01:43:00 +0000
From:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>
Subject: RE: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound
 violation information



On 2014-10-24, Thomas Gleixner wrote:
> On Sun, 12 Oct 2014, Qiaowei Ren wrote:
> 
>> This patch sets bound violation fields of siginfo struct in #BR
>> exception handler by decoding the user instruction and constructing
>> the faulting pointer.
>> 
>> This patch does't use the generic decoder, and implements a limited
>> special-purpose decoder to decode MPX instructions, simply because
>> the generic decoder is very heavyweight not just in terms of
>> performance but in terms of interface -- because it has to.
> 
> My question still stands why using the existing decoder is an issue.
> Performance is a complete non issue in case of a bounds violation and
> the interface argument is just silly, really.
> 

As hpa said, we only need to decode several mpx instructions including BNDCL/BNDCU, and general decoder looks like a little heavy. Peter, what do you think about it?

Thanks,
Qiaowei

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