Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound violation information

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 11 Sep 2014, H. Peter Anvin wrote:

> On 09/11/2014 03:32 PM, Dave Hansen wrote:
> > On 09/11/2014 03:18 PM, Thomas Gleixner wrote:
> >> On Thu, 11 Sep 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.
> >>
> >> And why is that an argument to add another special purpose decoder?
> > 
> > Peter asked for it to be done this way specifically:
> > 
> > 	https://lkml.org/lkml/2014/6/19/411
> > 
> 
> Specifically because marshaling the data in and out of the generic
> decoder was more complex than a special-purpose decoder.

I did not look at that detail and I trust your judgement here, but
that is in no way explained in the changelog.

This whole patchset is a pain to review due to half baken changelogs
and complete lack of a proper design description.

Thanks,

	tglx