linux-kernel - Re: [PATCH 2/2] hw-breakpoint: Keep track of dr7 local enable bits

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Date:	Fri, 19 Feb 2010 18:41:53 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Michael Stefaniuc <mstefani@...hat.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Maneesh Soni <maneesh@...ux.vnet.ibm.com>,
	Alexandre Julliard <julliard@...ehq.org>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH 2/2] hw-breakpoint: Keep track of dr7 local enable bits

On Fri, Feb 19, 2010 at 02:28:31PM +0530, K.Prasad wrote:
> On Thu, Feb 18, 2010 at 07:00:01PM +0100, Frederic Weisbecker wrote:
> 
> > diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
> > index 017d937..0c1033d 100644
> > --- a/arch/x86/kernel/ptrace.c
> > +++ b/arch/x86/kernel/ptrace.c
> > @@ -702,7 +702,7 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
> >  	} else if (n == 6) {
> >  		val = thread->debugreg6;
> >  	 } else if (n == 7) {
> > -		val = ptrace_get_dr7(thread->ptrace_bps);
> > +		val = thread->ptrace_dr7;
> 
> Some more comments that I missed out in the previous mail...
> 
> Shouldn't ptrace_get_dr7() function be entirely removed now, given that
> its only caller no longer invokes it?
> 
> >  	}
> >  	return val;
> >  }
> > @@ -778,8 +778,11 @@ int ptrace_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
> >  			return rc;
> >  	}
> >  	/* All that's left is DR7 */
> > -	if (n == 7)
> > +	if (n == 7) {
> >  		rc = ptrace_write_dr7(tsk, val);
> 
> And ptrace_write_dr7() should be made to populate thread->ptrace_dr7 if
> it is going to return a success.
> 
> > +		if (!rc)
> > +			thread->ptrace_dr7 = val;
> > +	}
> > 
> >  ret_path:
> >  	return rc;
> > -- 
> > 1.6.2.3
> > 
> 
> Thanks,
> K.Prasad
> 


This is urgent so I'm pushing the two patches right away as they fix the
regression and are not intrusive.

Let's further improve that later, for a merge window, ok?

Thanks.

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