From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1abjxd-0007Fo-Ra for barebox@lists.infradead.org; Fri, 04 Mar 2016 07:15:42 +0000 Date: Fri, 4 Mar 2016 08:15:18 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Message-ID: <20160304071518.GR20323@pengutronix.de> References: <1456959088-9609-1-git-send-email-akurz@blala.de> <20160304070448.GB21869@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160304070448.GB21869@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] arm/cpu/lowlevel: fix: possible processor mode change To: Sascha Hauer Cc: barebox@lists.infradead.org, Alexander Kurz Hello Sascha, On Fri, Mar 04, 2016 at 08:04:48AM +0100, Sascha Hauer wrote: > Hi Alexander, > = > On Wed, Mar 02, 2016 at 11:51:28PM +0100, Alexander Kurz wrote: > > This is a re-application of fix 17644b55. > > arm_cpu_lowlevel_init() will set the processor mode to 0x13 (supervisor= ). > > When this function is entered via a different processor mode, register > > banking will happen to lr (r14), resulting in an invalid return address. > > This fix will preserve the return address manually. > > = > > Signed-off-by: Alexander Kurz > > --- > > arch/arm/cpu/lowlevel.S | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > = > > diff --git a/arch/arm/cpu/lowlevel.S b/arch/arm/cpu/lowlevel.S > > index b76222d..e5baa12 100644 > > --- a/arch/arm/cpu/lowlevel.S > > +++ b/arch/arm/cpu/lowlevel.S > > @@ -4,6 +4,8 @@ > > = > > .section ".text_bare_init_","ax" > > ENTRY(arm_cpu_lowlevel_init) > > + /* save lr, since it may be banked away with a processor mode change = */ > > + mov r2, lr Acked-by: Uwe Kleine-K=F6nig > Thanks for fixing this and for adding a comment why this is done. This > hopefully prevents us from breaking it again. > = > Out of interest, what system are you using where this fix is necesssary? > = > Uwe, now we know why that was done and why e190bcf (arm/cpu/lowlevel: > Don't save the return address in another register) was a bad idea. Right. :-) But even if I had seen 17644b55cae9c234b26213d644e9fd939b0ec815 back then I would have wondered because the commit log isn't that verbose :-( Best regards Uwe -- = Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox