On 2020-06-03 08:29, Neal Liu wrote:
On Tue, 2020-06-02 at 21:02 +0800, Marc Zyngier wrote:
On 2020-06-02 13:14, Ard Biesheuvel wrote:
> On Tue, 2 Jun 2020 at 10:15, Neal Liu <neal.liu@xxxxxxxxxxxx> wrote:
>>
>> These patch series introduce a security random number generator
>> which provides a generic interface to get hardware rnd from Secure
>> state. The Secure state can be Arm Trusted Firmware(ATF), Trusted
>> Execution Environment(TEE), or even EL2 hypervisor.
>>
>> Patch #1..2 adds sec-rng kernel driver for Trustzone based SoCs.
>> For security awareness SoCs on ARMv8 with TrustZone enabled,
>> peripherals like entropy sources is not accessible from normal world
>> (linux) and rather accessible from secure world (HYP/ATF/TEE) only.
>> This driver aims to provide a generic interface to Arm Trusted
>> Firmware or Hypervisor rng service.
>>
>>
>> changes since v1:
>> - rename mt67xx-rng to mtk-sec-rng since all MediaTek ARMv8 SoCs can
>> reuse
>> this driver.
>> - refine coding style and unnecessary check.
>>
>> changes since v2:
>> - remove unused comments.
>> - remove redundant variable.
>>
>> changes since v3:
>> - add dt-bindings for MediaTek rng with TrustZone enabled.
>> - revise HWRNG SMC call fid.
>>
>> changes since v4:
>> - move bindings to the arm/firmware directory.
>> - revise driver init flow to check more property.
>>
>> changes since v5:
>> - refactor to more generic security rng driver which
>> is not platform specific.
>>
>> *** BLURB HERE ***
>>
>> Neal Liu (2):
>> dt-bindings: rng: add bindings for sec-rng
>> hwrng: add sec-rng driver
>>
>
> There is no reason to model a SMC call as a driver, and represent it
> via a DT node like this.
+1.
> It would be much better if this SMC interface is made truly generic,
> and wired into the arch_get_random() interface, which can be used much
> earlier.
Wasn't there a plan to standardize a SMC call to rule them all?
M.
Could you give us a hint how to make this SMC interface more generic in
addition to my approach?
There is no (easy) way to get platform-independent SMC function ID,
which is why we encode it into device tree, and provide a generic
driver. In this way, different devices can be mapped and then get
different function ID internally.
The idea is simply to have *one* single ID that caters for all
implementations, just like we did for PSCI at the time. This
requires ARM to edict a standard, which is what I was referring
to above.
There is zero benefit in having a platform-dependent ID. It just
pointlessly increases complexity, and means we cannot use the RNG
before the firmware tables are available (yes, we need it that
early).
M.
--
Jazz is not dead. It just smells funny...
