From mboxrd@z Thu Jan  1 00:00:00 1970
From: rabin@rab.in (Rabin Vincent)
Date: Tue, 16 Mar 2010 00:02:58 +0530
Subject: [PATCH 06/10] ARM: ftrace: add Thumb-2 support
In-Reply-To: <1268605815.2168.6.camel@e102109-lin.cambridge.arm.com>
References: <1268462987-8271-1-git-send-email-rabin@rab.in>
	<1268462987-8271-7-git-send-email-rabin@rab.in>
	<1268605815.2168.6.camel@e102109-lin.cambridge.arm.com>
Message-ID: <20100315183258.GA2141@debian>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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