linux-kernel - Re: Regression in ptrace (Wine) starting with 2.6.33-rc1

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Date:	Mon, 15 Feb 2010 11:47:24 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Michael Stefaniuc <mstefani@...hat.com>
Cc:	prasad@...ux.vnet.ibm.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org,
	Maneesh Soni <maneesh@...ux.vnet.ibm.com>,
	Alexandre Julliard <julliard@...ehq.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Maciej Rutecki <maciej.rutecki@...il.com>
Subject: Re: Regression in ptrace (Wine) starting with 2.6.33-rc1

> - The other one with 'locally'/'globally' enabled breakpoints.

There is no "local/global" enablement.  That distinction is meaningless
given the way the kernel uses the hardware.  Which of those bits you set
has no material effect on the watchpoint/trap behavior.  

The only regression is in the observed bit pattern read back from dr7.
To be 100% compatible, the hw_breakpoint ptrace-compatibility front-end
should record the state of the useless bits to report back, so the only
differences from the bit pattern written are whatever ones the real
hardware would have shown from writing dr7 and reading it back.

Thanks,
Roland

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