From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752346AbeCUOKC (ORCPT ); Wed, 21 Mar 2018 10:10:02 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:54388 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751778AbeCUOKB (ORCPT ); Wed, 21 Mar 2018 10:10:01 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Wed, 21 Mar 2018 15:09:58 +0100 From: Stefan Agner To: Robin Murphy , swarren@nvidia.com, thierry.reding@gmail.com, digetx@gmail.com Cc: linux@armlinux.org.uk, ard.biesheuvel@linaro.org, arnd@arndb.de, nicolas.pitre@linaro.org, keescook@chromium.org, marc.zyngier@arm.com, linux-kernel@vger.kernel.org, mka@chromium.org, linux-arm-kernel@lists.infradead.org, Bernhard.Rosenkranzer@linaro.org Subject: Re: [PATCH 3/5] ARM: trusted_foundations: do not use naked function In-Reply-To: <124e16c9-b8ca-9c7e-ade5-b033eed76e14@arm.com> References: <20180320230206.25289-1-stefan@agner.ch> <20180320230206.25289-4-stefan@agner.ch> <124e16c9-b8ca-9c7e-ade5-b033eed76e14@arm.com> Message-ID: <302cfd1a4324e064cd4f189e4e0ffc21@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 21.03.2018 13:13, Robin Murphy wrote: > On 20/03/18 23:02, 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. >> >> Additionally also make sure all callee-saved registers get saved >> as it has been done before. >> >> Signed-off-by: Stefan Agner >> --- >> arch/arm/firmware/trusted_foundations.c | 12 +++++++----- >> 1 file changed, 7 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm/firmware/trusted_foundations.c b/arch/arm/firmware/trusted_foundations.c >> index 3fb1b5a1dce9..426d732e6591 100644 >> --- a/arch/arm/firmware/trusted_foundations.c >> +++ b/arch/arm/firmware/trusted_foundations.c >> @@ -31,21 +31,23 @@ >> 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" >> __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}" >> : >> - : "r" (type), "r" (arg1), "r" (arg2) >> - : "memory"); >> + : "r" (r0), "r" (r1), "r" (r2) >> + : "memory", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10"); > > I may be missing a subtlety, but it looks like we no longer have a > guarantee that r11 will be caller-saved as it was previously. I don't > know the Trusted Foundations ABI to say whether that matters or not, > but if it is the case that it never needed preserving anyway, that > might be worth calling out in the commit message. Adding r11 (fp) to the clobber list causes an error when using gcc and CONFIG_FRAME_POINTER=y: arch/arm/firmware/trusted_foundations.c: In function ‘tf_generic_smc’: arch/arm/firmware/trusted_foundations.c:51:1: error: fp cannot be used in asm here Not sure what ABI Trusted Foundations follow. [adding Stephen, Thierry and Dmitry] Maybe someone more familiar with NVIDIA Tegra SoCs can help? When CONFIG_FRAME_POINTER=y fp gets saved anyway. So we could add r11 to clobber list ifndef CONFIG_FRAME_POINTER... -- Stefan > > Robin. > >> } >> static int tf_set_cpu_boot_addr(int cpu, unsigned long boot_addr) >>