linux-kernel - Re: [PATCH] x86: make DR*

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Message-ID: <20130425144818.GA25921@redhat.com>
Date:	Thu, 25 Apr 2013 16:48:18 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Miller <davem@...emloft.net>,
	"Theodore Ts'o" <tytso@....edu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Network Development <netdev@...r.kernel.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] x86: make DR*_RESERVED unsigned long

On 04/24, H. Peter Anvin wrote:
>
> On 04/24/2013 10:07 AM, Oleg Nesterov wrote:
> > DR6_RESERVED and DR_CONTROL_RESERVED are used to clear the set
> > bits in the "unsigned long" data, make them long to ensure that
> > "&~" doesn't clear the upper bits.
> >
> > do_debug() and ptrace_write_dr7() which use DR*_RESERVED look
> > safe, but probably it makes sense to cleanup anyway.
> >
> > Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
>
> Can you please put in the description if this is a manifest or
> non-manifest bug and, if manifest, what the issues are?  It greatly
> affects what we otherwise have to do to address the bug.

Sorry if it was not clear, I tried to explain in the changelog that
this is only cleanup. Yes, dr6 should have all zeroes in 32-64 so
the usage of DR6_RESERVED is safe.

> Also, the -UL suffix is usually capitalized in our codebase.

OK, iiuc otherwise you agree with this change. I'll send v2.

Oleg.

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