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?
The problem is StMM is not a pseudo-TA and pretending to be one is not easy. It looks like one, but due to the internal ABI, it's compiled and launched differently within OP-TEE. We could still add this but...
- 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.
I talked about this with Jens, but there's an assumption here that every TEE from that point onward will implement this. But without a standard describing this, I don't see how we can convince others. The current code puts the responsibility back to the tee/core subsystem, so any vendor can provide his own callbacks
Regards /Ilias
-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