From mboxrd@z Thu Jan 1 00:00:00 1970 From: treding@nvidia.com (Thierry Reding) Date: Tue, 17 Apr 2018 10:11:10 +0200 Subject: [PATCH v2 3/6] ARM: trusted_foundations: do not use naked function In-Reply-To: <507a66ab9ab530a6d71db7a74f11ddfb@agner.ch> 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> <507a66ab9ab530a6d71db7a74f11ddfb@agner.ch> Message-ID: <20180417081109.GA5804@ulmo> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Apr 16, 2018 at 08:21:09PM +0200, Stefan Agner wrote: > 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? I don't mind picking this up into the Tegra tree. Might be a good idea to move this into drivers/firmware, though, since that's where all the other firmware-related drivers reside. Firmware code, such as the BPMP driver, usually goes through ARM-SoC these days. I think this is in the same category. Russell, any objections to me picking this patch up and moving it into drivers/firmware? Thanks, Thierry -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: