Messages in this thread | | | Date | Fri, 13 Jul 2018 10:07:41 +0200 | From | Stefan Agner <> | Subject | Re: [PATCH v2 3/6] ARM: trusted_foundations: do not use naked function |
| |
On 13.07.2018 01:01, Russell King - ARM Linux wrote: > On Thu, Jul 12, 2018 at 03:43:10PM -0700, Kees Cook wrote: >> On Tue, Apr 17, 2018 at 1:11 AM, Thierry Reding <treding@nvidia.com> wrote: >> > 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 <digetx@gmail.com> >> >> >>>>>> Cc: Stephen Warren <swarren@nvidia.com> >> >> >>>>>> Cc: Thierry Reding <treding@nvidia.com> >> >> >>>>>> Signed-off-by: Stefan Agner <stefan@agner.ch> >> >> >>>>>> --- >> >> >>>>>> 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? >> >> Please take this -- without it I'm seeing build failures on the arm >> allmodconfig under gcc 7.3.0: > > Sorry, I'd completely missed this... now replied on the original patch.
Thierry merged this patch just two days ago, so it is already in -next.
-- Stefan
| |