From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645AbeC0MQJ (ORCPT ); Tue, 27 Mar 2018 08:16:09 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:38140 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752232AbeC0MQH (ORCPT ); Tue, 27 Mar 2018 08:16:07 -0400 X-Google-Smtp-Source: AIpwx48pLWUrsVD0oOoXCLAj86V2pTWECxx3YOzuwgU7MyljUQj9fjHH3Ze+THAwZ8TOQImpWGvwLQ== Subject: Re: [PATCH v2 3/6] ARM: trusted_foundations: do not use naked function To: Robin Murphy , Stefan Agner , linux@armlinux.org.uk, ard.biesheuvel@linaro.org, arnd@arndb.de Cc: 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, Stephen Warren , Thierry Reding 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> From: Dmitry Osipenko Openpgp: preference=signencrypt Autocrypt: addr=digetx@gmail.com; keydata= xsBNBFpX5TwBCADQhg+lBnTunWSPbP5I+rM9q6EKPm5fu2RbqyVAh/W3fRvLyghdb58Yrmjm KpDYUhBIZvAQoFLEL1IPAgJBtmPvemO1XUGPxfYNh/3BlcDFBAgERrI3BfA/6pk7SAFn8u84 p+J1TW4rrPYcusfs44abJrn8CH0GZKt2AZIsGbGQ79O2HHXKHr9V95ZEPWH5AR0UtL6wxg6o O56UNG3rIzSL5getRDQW3yCtjcqM44mz6GPhSE2sxNgqureAbnzvr4/93ndOHtQUXPzzTrYB z/WqLGhPdx5Ouzn0Q0kSVCQiqeExlcQ7i7aKRRrELz/5/IXbCo2O+53twlX8xOps9iMfABEB AAHNIkRtaXRyeSBPc2lwZW5rbyA8ZGlnZXR4QGdtYWlsLmNvbT7CwJQEEwEIAD4WIQSczHcO 3uc4K1eb3yvTNNaPsNRzvAUCWlflPAIbAwUJA8JnAAULCQgHAgYVCgkICwIEFgIDAQIeAQIX gAAKCRDTNNaPsNRzvFjTCACqAh1M9/YPq73/ai5h2ExDquTgJnjegL8KL2yHL3G+XINwzN5E nPI7esoYm+zVWDJbv3UuRqylpookLNSRA01yyvkaMcipB/B128UnqmUiGRqezj9QE20yIauo uHRuwHPE2q+UkfUhRX9iuOaEyQtZDiCa0myMjmRkJ+Z8ZetclEPG8dYZu47w04phuMlu1QAt a0gkZOaMKvXgj21ushALS6nYnvm7HiIPQXfnEXThartatRvFdmbG4PCn0IoICkQBizwJtXrL HEjELIFap0M8krVJlUoZTFaZnaZkGpUDWikeFtAuie2KuIxmVBYPM4X7pM3eP3AVvIPGS7EE UUFuzsBNBFpX5TwBCADFNDou220thijaLLGaQsebWjzc/gPRxMixIpk856MRyRaQin+IbGD6 YskMb5ZSD3nS88LIKNfY4MMH0LwfYztI++ICG2vdFLkbBt78E+LqEa+kZ9072l4W5KO3mWQo +jMfxXbpgGlc7iuEReDgl8iyZ27r51kSW665CYvvu2YJhLqgdj6QM1lN2D1UnhEhkkU+pRAj 1rJVOxdfJaQNQS4+204p3TrURovzNGkN/brqakpNIcqGOAGQqb8F0tuwwuP7ERq/BzDNkbdr qJOrVC/wkHRq1jfabQczWKf8MwYOvivR3HY8d3CpSQxmUXDtdOWfg0XGm1dxYnVfqPjuJaZt ABEBAAHCwHwEGAEIACYWIQSczHcO3uc4K1eb3yvTNNaPsNRzvAUCWlflPAIbDAUJA8JnAAAK CRDTNNaPsNRzvJzuB/9d+sxcwHbO8ZDcgaLX9N+bXFqN9fIRVmBUyWa+qqTSREA4uVAtYcRT lfPE2OQ7aMFxaYPwo+/z5SLpu8HcEhN/FG9uIkfYwK0mdCO0vgvlfvBJm4VHe7C6vyAeEPJQ DKbBvdgeqFqO+PsLkk2sawF/9sontMJ5iFfjNDj4UeAo4VsdlduTBZv5hHFvIbv/p7jKH6OT 90FsgUSVbShh7SH5OzAcgqSy4kxuS1AHizWo6P3f9vei987LZWTyhuEuhJsOfivDsjKIq7qQ c5eR+JJtyLEA0Jt4cQGhpzHtWB0yB3XxXzHVa4QUp00BNVWyiJ/t9JHT4S5mdyLfcKm7ddc9 Message-ID: Date: Tue, 27 Mar 2018 15:16:04 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <263337af-7541-be9e-3db6-6cb987fd08fb@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.