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: BUG: branch trace support for 64-bit Book-E (was Re: questions around Book III-E and branch trace)
Date: Wed, 17 Apr 2013 17:30:46 -0600 [thread overview]
Message-ID: <516F30A6.5070408@genband.com> (raw)
In-Reply-To: <516EED8D.3040304@genband.com>
On 04/17/2013 12:44 PM, Chris Friesen wrote:
> 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.
While poking around looking for answers to my previous questions I seem
to have stumbled over a bug in branch tracing for 64-bit Book-E.
Commit ec097c8 added support for branch tracing for 32-bit code, but
didn't do the 64-bit path. As it stands, debug_crit/debug_debug in
exceptions-64e.S only check DBSR_IC, so branch tracing will not get
fixed up and will die a horrible death (typically in a tbr exception
handler).
I was banging my head trying to figure out why this wasn't working when
I finally clued in to the fact that head_booke.h only applied to the
32-bit implementation. This might be something useful to put in a
comment up at the top of the file.
Chris
next prev parent reply other threads:[~2013-04-17 23:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-17 18:44 questions around Book III-E and branch trace Chris Friesen
2013-04-17 23:30 ` Chris Friesen [this message]
2013-04-18 6:28 ` Benjamin Herrenschmidt
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