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Date: Tue, 16 Mar 2010 00:02:58 +0530
From: Rabin Vincent <rabin@rab.in>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
       Steven Rostedt <rostedt@goodmis.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Ingo Molnar <mingo@redhat.com>,
       Abhishek Sagar <sagar.abhishek@gmail.com>,
       Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
	<u.kleine-koenig@pengutronix.de>
Subject: Re: [PATCH 06/10] ARM: ftrace: add Thumb-2 support
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On Sun, Mar 14, 2010 at 10:30:15PM +0000, Catalin Marinas wrote:
> On Sat, 2010-03-13 at 06:49 +0000, Rabin Vincent wrote:
> >  - The problem with the "mov lr, pc", is that it does not set the lsb when
> >    storing the pc in lr.  The called function returns with "bx lr", and the
> >    mode changes to ARM.  The blx is to avoid this.
> 
> I'm not familiar with ftrace but why does the called function returns
> using "bx lr". Is this generated by the compiler? I had the impression
> that if we don't enable interworking, we wouldn't get this instruction
> (but haven't tried this yet).

There's nothing special about the called function: it's just a regular C
function.  GCC uses "bx lr" for the return.

Rabin