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 1ZEXva-0007bZ-Fp for barebox@lists.infradead.org; Mon, 13 Jul 2015 07:13:27 +0000 Date: Mon, 13 Jul 2015 09:13:04 +0200 From: Sascha Hauer Message-ID: <20150713071304.GG18700@pengutronix.de> References: <1436353060-22497-1-git-send-email-s.hauer@pengutronix.de> <559D4C69.8080001@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <559D4C69.8080001@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] Build with -fno-delete-null-pointer-checks To: Marc Kleine-Budde Cc: Michael Olbrich , Barebox List On Wed, Jul 08, 2015 at 06:14:33PM +0200, Marc Kleine-Budde wrote: > On 07/08/2015 12:57 PM, Sascha Hauer wrote: > > This becomes important with gcc-4.9. Without this gcc assumes > > that accessing NULL pointers traps and everything that happens > > behind the access is not executed. This recently happened with > > i.MX53 which has: > > > > static int imx53_silicon_revision(void) > > { > > void __iomem *rom = MX53_IROM_BASE_ADDR; > > > > rev = readl(rom + SI_REV); > > ... > > } > > > > This resulted in object code in which the last instruction is > > the readl, the reset of the function is missing because gcc assumes this > > is never executed. > > > > Disable this optimization with -fno-delete-null-pointer-checks since > > in barebox NULL pointers can indeed be valid. > > > > Signed-off-by: Sascha Hauer > > --- > > Makefile | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/Makefile b/Makefile > > index e7db67a..0fe9274 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -301,7 +301,8 @@ CPPFLAGS := -D__KERNEL__ -D__BAREBOX__ $(LINUXINCLUDE) -fno-builtin -ffre > > > > CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ > > -Werror-implicit-function-declaration \ > > - -fno-strict-aliasing -fno-common -Os -pipe > > + -fno-strict-aliasing -fno-common -Os -pipe \ > > + -fno-delete-null-pointer-checks > The kernel uses: > $(call cc-option,-fno-delete-null-pointer-checks,) Changed it to do the same. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox