From mboxrd@z Thu Jan  1 00:00:00 1970
From: pavel@ucw.cz (Pavel Machek)
Date: Thu, 4 Feb 2010 23:46:46 +0100
Subject: 32-bit Thumb-2 breakpoints
In-Reply-To: <20100203174426.GA10898@caradoc.them.org>
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	<20100111223503.GD7925@n2100.arm.linux.org.uk>
	<20100111225436.GA7408@caradoc.them.org>
	<20100111231027.GA30714@shareable.org>
	<20100111231702.GA9485@caradoc.them.org>
	<20100203172301.GD19037@shareable.org>
	<20100203174426.GA10898@caradoc.them.org>
Message-ID: <20100204224646.GC1436@ucw.cz>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed 2010-02-03 12:44:26, Daniel Jacobowitz wrote:
> On Wed, Feb 03, 2010 at 05:23:01PM +0000, Jamie Lokier wrote:
> > Daniel Jacobowitz wrote:
> > > Thankfully, both branches into IT blocks and branches
> > > leaving IT blocks not at the last instruction are forbidden.
> > 
> > Forbidden as in throws a fault, or forbidden as in "can we use this to
> > break out of GDB single-stepping to give third-parties a hard time
> > tracing my secret code"?
> 
> Forbidden as in "the architecture documentation says it has
> unpredictable behavior".
> 
> That's generally where I draw the line at trying to handle bad code.
> In practice, I will make a wild guess that current processors fault
> branches during an IT block and don't do anything fancy for branches
> into an IT block, or else it messes up in some hard-to-reproduce way.

So it seems the second kind of forbidden :-(.
									Pavel

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