Hi Neal, On Fri, 5 Jun 2020 at 14:40, Neal Liu <neal.liu@xxxxxxxxxxxx> wrote: > > On Fri, 2020-06-05 at 09:09 +0100, Russell King - ARM Linux admin wrote: > > On Fri, Jun 05, 2020 at 03:19:03PM +0800, Neal Liu wrote: > > > On Wed, 2020-06-03 at 17:34 +0800, Russell King - ARM Linux admin wrote: > > > > This kind of thing is something that ARM have seems to shy away from > > > > doing - it's a point I brought up many years ago when the whole > > > > trustzone thing first appeared with its SMC call. Those around the > > > > conference table were not interested - ARM seemed to prefer every > > > > vendor to do off and do their own thing with the SMC interface. > > > > > > Does that mean it make sense to model a sec-rng driver, and get each > > > vendor's SMC function id by DT node? > > > > _If_ vendors have already gone off and decided to use different SMC > > function IDs for this, while keeping the rest of the SMC interface > > the same, then the choice has already been made. > > > > I know on 32-bit that some of the secure world implementations can't > > be changed; they're burnt into the ROM. I believe on 64-bit that isn't > > the case, which makes it easier to standardise. > > > > Do you have visibility of how this SMC is implemented in the secure > > side? Is it in ATF, and is it done as a vendor hack or is there an > > element of generic implementation to it? Has it been submitted > > upstream to the main ATF repository? > > > > Take MediaTek as an example, some SoCs are implemented in ATF, some of > them are implemented in TEE. In case your TEE implementation is derived from OP-TEE, then I will suggest you to re-use OP-TEE based RNG driver [1]. With that, you just need to implement an OP-TEE based pseudo trusted application (similar to this [2]) specific to your platform and need to extend driver UUID config table [3] with UUID of your platform specific pseudo TA. This way you can avoid using hardcoded DT based SMC approach and rather use auto RNG device detection provided by TEE bus. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/hw_random/optee-rng.c [2] https://github.com/OP-TEE/optee_os/blob/master/core/arch/arm/plat-synquacer/rng_pta.c [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/hw_random/optee-rng.c#n273 -Sumit > We have no plan to make generic > implementation in "secure world". > > Due to there must have different implementation in secure world for > vendors, we plan to provide a generic SMC interface in secure rng kernel > driver for more flexibility. > > Vendors can decide which "secure world" they want (HYP/ATF/TEE) by > different smc/hvc and different SMC function IDs in DT node. > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
