On 17.04.2018 10:11, Thierry Reding 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 <dig...@gmail.com>
>> >>>>>> Cc: Stephen Warren <swar...@nvidia.com>
>> >>>>>> Cc: Thierry Reding <tred...@nvidia.com>
>> >>>>>> Signed-off-by: Stefan Agner <ste...@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?
Russel, I think Thierry is waiting for your ok on this.
--
Stefan
