Messages in this thread | | | Date | Fri, 3 Feb 2023 09:29:01 +0100 | From | Jens Wiklander <> | Subject | Re: [RFC PATCH 0/2] introduce op-tee based EFI Runtime Variable Service |
| |
Hi Sumit,
On Thu, Feb 02, 2023 at 05:35:49PM +0530, Sumit Garg wrote: > Hi Masahisa, > > On Thu, 26 Jan 2023 at 18:52, Masahisa Kojima > <masahisa.kojima@linaro.org> wrote: > > > > This RFC series introduces the op-tee based EFI Runtime Variable > > Service. > > > > The eMMC device is typically owned by the non-secure world(linux in > > this case). There is an existing solution utilizing eMMC RPMB partition > > for EFI Variables, it is implemented by interacting with > > OP-TEE, StandaloneMM(as EFI Variable Service Pseudo TA), eMMC driver > > and tee-supplicant. The last piece is the tee-based variable access > > driver to interact with OP-TEE and StandaloneMM. > > > > After an overall look at the APIs, following are some initial comments: > - Is there any reason to have the edk2 specific StandaloneMM stack in > Linux to communicate with OP-TEE pseudo TA? > - I think the OP-TEE pseudo TA should be able to expose a rather > generic invoke commands such as: > TEE_EFI_GET_VARIABLE > TEE_EFI_GET_NEXT_VARIABLE > TEE_EFI_SET_VARIABLE > So it should no longer be tied to StMM stack and other TEE > implementations can re-use the abstracted interface to communicate > with its corresponding secure storage TA.
In the current setup we have the following layers in the kernel: 1. efivar_operations 2. MM 3. PTA_STMM 4. OP-TEE MSG
and in the secure world: S1. internal to StMM S2. MM interface to StMM S3. PTA_STMM S4. OP-TEE MSG
If I understand you correctly you'd like to see this instead: Kernel: 1. efivar_operations 2. PTA_EFIVAR 4. OP-TEE MSG
Since we still have the MM interface with StMM we'd have this in the secure world: S1. internal to StMM S2. MM interface to StMM S3. PTA_EFIVAR S4. OP-TEE MSG
At S3 we'd have to convert between EFIVAR and MM messages. The difference is that we're moving the EFIVAR <-> MM conversion from the non-secure world into the secure world. We're still using OP-TEE specific communication at the fourth layer. So we're only moving problem around, I'd rather avoid growing the OP-TEE part in the secure world.
Cheers, Jens
> > -Sumit > > > Masahisa Kojima (2): > > efi: expose efivar generic ops register function > > tee: Add op-tee helper functions for variable access > > > > drivers/firmware/efi/efi.c | 12 + > > drivers/tee/optee/Kconfig | 10 + > > drivers/tee/optee/Makefile | 1 + > > drivers/tee/optee/mm_communication.h | 249 +++++++++++ > > drivers/tee/optee/optee_private.h | 5 +- > > drivers/tee/optee/optee_stmm_efi.c | 598 +++++++++++++++++++++++++++ > > drivers/tee/tee_core.c | 23 ++ > > include/linux/efi.h | 4 + > > include/linux/tee_drv.h | 23 ++ > > 9 files changed, 924 insertions(+), 1 deletion(-) > > create mode 100644 drivers/tee/optee/mm_communication.h > > create mode 100644 drivers/tee/optee/optee_stmm_efi.c > > > > -- > > 2.30.2 > >
| |