[PATCH v5 0/3] introduce tee-based EFI Runtime Variable Service

From: Masahisa Kojima
Date: Thu May 25 2023 - 21:08:59 EST

This series introduces the 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.

v4 -> v5
- rebase to efi-next based on v6.4-rc1
- set generic_ops.query_variable_info, it works as expected as follows.
$ df -h /sys/firmware/efi/efivars/
Filesystem Size Used Avail Use% Mounted on
efivarfs 16K 1.3K 15K 8% /sys/firmware/efi/efivars

v3 -> v4:
- replace the reference from EDK2 to PI Specification
- remove EDK2 source code reference comments
- prepare nonblocking variant of set_variable, it just returns
- remove redundant buffer size check
- argument name change in mm_communicate
- function interface changes in setup_mm_hdr to remove (void **) cast

v2 -> v3:
- add CONFIG_EFI dependency to TEE_STMM_EFI
- add missing return code check for tee_client_invoke_func()
- directly call efivars_register/unregister from tee_stmm_efi.c

rfc v1 -> v2:
- split patch into three patches, one for drivers/tee,
one for include/linux/efi.h, and one for the driver/firmware/efi/stmm
- context/session management into probe() and remove() same as other tee
client driver
- StMM variable driver is moved from driver/tee/optee to driver/firmware/efi
- use "tee" prefix instead of "optee" in driver/firmware/efi/stmm/tee_stmm_efi.c,
this file does not contain op-tee specific code, abstracted by tee layer and
StMM variable driver will work on other tee implementation.
- implement query_variable_store() but currently not used
- no use of TEEC_SUCCESS, it is defined in driver/tee/optee/optee_private.h.
Other tee client drivers use 0 instead of using TEEC_SUCCESS
- remove TEEC_ERROR_EXCESS_DATA status, it is referred just to output
error message

Masahisa Kojima (3):
efi: expose efivar generic ops register function
efi: Add EFI_ACCESS_DENIED status code
efi: Add tee-based EFI variable driver

drivers/firmware/efi/Kconfig | 15 +
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/efi.c | 12 +
drivers/firmware/efi/stmm/mm_communication.h | 236 +++++++
drivers/firmware/efi/stmm/tee_stmm_efi.c | 638 +++++++++++++++++++
include/linux/efi.h | 4 +
6 files changed, 906 insertions(+)
create mode 100644 drivers/firmware/efi/stmm/mm_communication.h
create mode 100644 drivers/firmware/efi/stmm/tee_stmm_efi.c