From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754954AbeEHMTg (ORCPT ); Tue, 8 May 2018 08:19:36 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57640 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754760AbeEHMTf (ORCPT ); Tue, 8 May 2018 08:19:35 -0400 Subject: Re: [RESEND PATCH v2] bus: arm-cci: use asm unreachable To: Stefan Agner , arm@kernel.org, arnd@arndb.de Cc: linux@armlinux.org.uk, ard.biesheuvel@linaro.org, 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 References: <20180508113211.7026-1-stefan@agner.ch> From: Robin Murphy Message-ID: <9925be9a-2e24-7ab4-4d7e-cb8f62c422e7@arm.com> Date: Tue, 8 May 2018 13:19:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180508113211.7026-1-stefan@agner.ch> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/05/18 12:32, 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(); > ^ > > While the function is marked __naked it actually properly return > in asm. There is no need for the unreachable() call. The commit title is a bit out-of-date now (I guess it could just be something like "remove unnecessary unreachable()" now), but the rest looks OK to me - even GCC clearly doesn't expect anything beyond the asm to be reachable anyway since the lack of epilogue includes the lack of any compiler-generated return. I've checked that GCC 7.2 generates identical object files before and after, other than (for obvious reasons) the line numbers generated by WANT_WARN_ON_SLOWPATH for all the WARN()s appearing later in the file. Reviewed-by: Robin Murphy > Suggested-by: Russell King > Signed-off-by: Stefan Agner > Acked-by: Nicolas Pitre > --- > drivers/bus/arm-cci.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c > index 443e4c3fd357..b8184a903583 100644 > --- a/drivers/bus/arm-cci.c > +++ b/drivers/bus/arm-cci.c > @@ -371,8 +371,6 @@ 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(); > } > > /** >