From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751656AbeCTXbA (ORCPT ); Tue, 20 Mar 2018 19:31:00 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:36280 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751343AbeCTXa6 (ORCPT ); Tue, 20 Mar 2018 19:30:58 -0400 Date: Tue, 20 Mar 2018 23:30:46 +0000 From: Russell King - ARM Linux To: Stefan Agner Cc: ard.biesheuvel@linaro.org, arnd@arndb.de, nicolas.pitre@linaro.org, marc.zyngier@arm.com, behanw@converseincode.com, keescook@chromium.org, Bernhard.Rosenkranzer@linaro.org, mka@chromium.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] bus: arm-cci: use asm unreachable Message-ID: <20180320233046.GL2743@n2100.armlinux.org.uk> References: <20180320230206.25289-1-stefan@agner.ch> <20180320230206.25289-2-stefan@agner.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180320230206.25289-2-stefan@agner.ch> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 21, 2018 at 12:02:02AM +0100, Stefan Agner wrote: > Mixing asm and C code is not recommended in a naked function by > gcc and leads to an error when using clang: > drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked > function is not supported > unreachable(); > ^ > > Instead of using the unreachable() macro use the assember variant > ASM_UNREACHABLE. This will no longer emit __builtin_unreachable(), > but since the function is naked and its return type is void it seems > not to have aversive effects. I think that unreachable() there is rather silly - this function *does* return, and the comments say as much. Just delete the silly "unreachable()", there's no need to put an ASM_UNREACHABLE in there. The function is not declared as not returning, and nothing in this file uses it anyway - it's called from the mcpm code, which also _does_ expect this function to return (if it doesn't, then we're basically saying the CPU that called it is dead.) > > Signed-off-by: Stefan Agner > --- > drivers/bus/arm-cci.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c > index 5426c04fe24b..ee9da86fec47 100644 > --- a/drivers/bus/arm-cci.c > +++ b/drivers/bus/arm-cci.c > @@ -2084,6 +2084,7 @@ asmlinkage void __naked cci_enable_port_for_self(void) > > " mov r0, #0 \n" > " bx lr \n" > + ASM_UNREACHABLE > > " .align 2 \n" > "5: .word cpu_port - . \n" > @@ -2103,8 +2104,6 @@ asmlinkage void __naked cci_enable_port_for_self(void) > [sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)), > [sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)), > [offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) ); > - > - unreachable(); > } > > /** > -- > 2.16.2 > -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up