From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753240AbeDPSVM (ORCPT ); Mon, 16 Apr 2018 14:21:12 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:43540 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752308AbeDPSVL (ORCPT ); Mon, 16 Apr 2018 14:21:11 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Mon, 16 Apr 2018 20:21:09 +0200 From: Stefan Agner To: Thierry Reding , Stephen Warren , linux@armlinux.org.uk Cc: Stephen Warren , Robin Murphy , 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, Dmitry Osipenko Subject: Re: [PATCH v2 3/6] ARM: trusted_foundations: do not use naked function In-Reply-To: <498de826-6e6c-63d8-00d6-f394b2725a34@wwwdotorg.org> References: <20180325180959.28008-1-stefan@agner.ch> <20180325180959.28008-4-stefan@agner.ch> <704c863a-0b5a-6396-d7da-f0ed17b7cca2@gmail.com> <263337af-7541-be9e-3db6-6cb987fd08fb@arm.com> <498de826-6e6c-63d8-00d6-f394b2725a34@wwwdotorg.org> Message-ID: <507a66ab9ab530a6d71db7a74f11ddfb@agner.ch> User-Agent: Roundcube Webmail/1.3.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.04.2018 18:08, Stephen Warren wrote: > On 04/16/2018 09:56 AM, Stefan Agner wrote: >> On 27.03.2018 14:16, Dmitry Osipenko wrote: >>> On 27.03.2018 14:54, Robin Murphy wrote: >>>> On 26/03/18 22:20, Dmitry Osipenko wrote: >>>>> On 25.03.2018 21:09, Stefan Agner wrote: >>>>>> As documented in GCC naked functions should only use Basic asm >>>>>> syntax. The Extended asm or mixture of Basic asm and "C" code is >>>>>> not guaranteed. Currently this works because it was hard coded >>>>>> to follow and check GCC behavior for arguments and register >>>>>> placement. >>>>>> >>>>>> Furthermore with clang using parameters in Extended asm in a >>>>>> naked function is not supported: >>>>>>    arch/arm/firmware/trusted_foundations.c:47:10: error: parameter >>>>>>            references not allowed in naked functions >>>>>>                  : "r" (type), "r" (arg1), "r" (arg2) >>>>>>                         ^ >>>>>> >>>>>> Use a regular function to be more portable. This aligns also with >>>>>> the other smc call implementations e.g. in qcom_scm-32.c and >>>>>> bcm_kona_smc.c. >>>>>> >>>>>> Cc: Dmitry Osipenko >>>>>> Cc: Stephen Warren >>>>>> Cc: Thierry Reding >>>>>> Signed-off-by: Stefan Agner >>>>>> --- >>>>>> Changes in v2: >>>>>> - Keep stmfd/ldmfd to avoid potential ABI issues >>>>>> >>>>>>   arch/arm/firmware/trusted_foundations.c | 14 +++++++++----- >>>>>>   1 file changed, 9 insertions(+), 5 deletions(-) >>>>>> >>>>>> diff --git a/arch/arm/firmware/trusted_foundations.c >>>>>> b/arch/arm/firmware/trusted_foundations.c >>>>>> index 3fb1b5a1dce9..689e6565abfc 100644 >>>>>> --- a/arch/arm/firmware/trusted_foundations.c >>>>>> +++ b/arch/arm/firmware/trusted_foundations.c >>>>>> @@ -31,21 +31,25 @@ >>>>>>     static unsigned long cpu_boot_addr; >>>>>>   -static void __naked tf_generic_smc(u32 type, u32 arg1, u32 arg2) >>>>>> +static void tf_generic_smc(u32 type, u32 arg1, u32 arg2) >>>>>>   { >>>>>> +    register u32 r0 asm("r0") = type; >>>>>> +    register u32 r1 asm("r1") = arg1; >>>>>> +    register u32 r2 asm("r2") = arg2; >>>>>> + >>>>>>       asm volatile( >>>>>>           ".arch_extension    sec\n\t" >>>>>> -        "stmfd    sp!, {r4 - r11, lr}\n\t" >>>>>> +        "stmfd    sp!, {r4 - r11}\n\t" >>>>>>           __asmeq("%0", "r0") >>>>>>           __asmeq("%1", "r1") >>>>>>           __asmeq("%2", "r2") >>>>>>           "mov    r3, #0\n\t" >>>>>>           "mov    r4, #0\n\t" >>>>>>           "smc    #0\n\t" >>>>>> -        "ldmfd    sp!, {r4 - r11, pc}" >>>>>> +        "ldmfd    sp!, {r4 - r11}\n\t" >>>>>>           : >>>>>> -        : "r" (type), "r" (arg1), "r" (arg2) >>>>>> -        : "memory"); >>>>>> +        : "r" (r0), "r" (r1), "r" (r2) >>>>>> +        : "memory", "r3", "r12", "lr"); >>>>> >>>>> Although seems "lr" won't be affected by SMC invocation because it should be >>>>> banked and hence could be omitted entirely from the code. Maybe somebody could >>>>> confirm this. >>>> Strictly per the letter of the architecture, the SMC could be trapped to Hyp >>>> mode, and a hypervisor might clobber LR_usr in the process of forwarding the >>>> call to the firmware secure monitor (since Hyp doesn't have a banked LR of its >>>> own). Admittedly there are probably no real systems with the appropriate >>>> hardware/software combination to hit that, but on the other hand if this gets >>>> inlined where the compiler has already created a stack frame then an LR clobber >>>> is essentially free, so I reckon we're better off keeping it for reassurance. >>>> This isn't exactly a critical fast path anyway. >>> >>> Okay, thank you for the clarification. >> >> So it seems this change is fine? >> >> Stephen, you picked up changes for this driver before, is this patch >> going through your tree? > > You had best ask Thierry; he's taken over Tegra maintenance upstream. > But that said, don't files in arch/arm go through Russell? I think the last patches applied to that file went through your tree. Thierry, Russel, any preferences? -- Stefan