linux-kernel - Re: [070/140] x86: Send a SIGTRAP for user icebp traps

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Message-ID: <20100731120451.GA5266@nowhere>
Date:	Sat, 31 Jul 2010 14:04:54 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Chuck Ebbert <cebbert@...hat.com>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	stable@...nel.org, stable-review@...nel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Prasad <prasad@...ux.vnet.ibm.com>
Subject: Re: [070/140] x86: Send a SIGTRAP for user icebp traps

On Sat, Jul 31, 2010 at 01:39:19AM -0400, Chuck Ebbert wrote:
> On Fri, 30 Jul 2010 10:30:35 -0700
> Greg KH <gregkh@...e.de> wrote:
> 
> > 2.6.33-stable review patch.  If anyone has any objections, please let us know.
> > 
> > ------------------
> > 
> > From: Frederic Weisbecker <fweisbec@...il.com>
> > 
> > commit a1e80fafc9f0742a1776a0490258cb64912411b0 upstream.
> > 
> 
> This backport will not work. Instead of fixing up the context of this 
> patch to make it apply, commit 40f9249a73f6c251adea492b1c3d19d39e2a9bda 
> ("x86/debug: Clear reserved bits of DR6 in do_debug()") should be 
> applied first, followed by an unmodified version of this commit.


It works because the 2.6.33 backport is slightly different from the 2.6.34 one.
We are dealing with (dr6 & ~0xffff0ff0) rather than dr6.

Backporting the commit you describe seemed too invasive and risky
for me, so I preferred to use that mask to ignore the dr6 reserved bits while
checking the icebp origin, only.

Thanks.

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