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From: Chris Friesen <chris.friesen@genband.com>
To: Kumar Gala <galak@kernel.crashing.org>,
	linuxppc-dev@lists.ozlabs.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>
Subject: questions around Book III-E and branch trace
Date: Wed, 17 Apr 2013 12:44:29 -0600	[thread overview]
Message-ID: <516EED8D.3040304@genband.com> (raw)

Hi,

I'm trying to wrap my head around how linux handles branch tracing on 
Book III-E.  I think I understand how we set MSR[DE] and DBCR0[IDM|BT], 
and how we handle fixing things up if an instruction being traced causes 
an exception.

I have a few questions though:

1) Does user_enable_block_step() have a bug in it?  The current code has

task->thread.dbcr0 = DBCR0_IDM | DBCR0_BT;

Should that be as follows (to match the singel-step case)?

task->thread.dbcr0 |= DBCR0_IDM | DBCR0_BT;


2) Why doesn't DBCR0_ACTIVE_EVENTS include DBCR0_BT?


3) In sys_debug_setcontext() why does SIG_DBG_BRANCH_TRACING return 
-EINVAL if CONFIG_PPC_ADV_DEBUG_REGS is set?  Would it not be possible 
to use DBCR0_BT?

Thanks,
Chris


-- 

Chris Friesen
Software Designer

500 Palladium Drive, Suite 2100
Ottawa, Ontario K2N 1C2, Canada
www.genband.com
office:+1.343.883.2717
chris.friesen@genband.com

             reply	other threads:[~2013-04-17 18:44 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-17 18:44 Chris Friesen [this message]
2013-04-17 23:30 ` BUG: branch trace support for 64-bit Book-E (was Re: questions around Book III-E and branch trace) Chris Friesen
2013-04-18  6:28 ` questions around Book III-E and branch trace Benjamin Herrenschmidt

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