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.
This driver depends on the tee-supplicant. When the tee-supplicant stops, this driver needs to be unbound from user-space script or tool, relevant patch is posted[1].
[1] https://lore.kernel.org/all/20231102073056.174480-2-sumit.garg@linaro.org/
Changelog: v9 -> v10 - patch #6 "tee: optee: restore efivars ops when tee-supplicant stops" is removed
v8 -> v9 - patch #6 "tee: optee: restore efivars ops when tee-supplicant stops" is newly added - remove !EFI_VARS_PSTORE Kconfig dependency, we have added a non-blocking set_variable and it just returns EFI_UNSUPPORTED. - remove obvious comments
v7 -> v8 Only patch #3 "efi: Add tee-based EFI variable driver" is updated. - fix typos - refactor error handling, direct return if applicable - use devm_add_action_or_reset() for closing of tee context/session - remove obvious comment
v6 -> v7 Patch #1-#4 are not updated. Patch #5 is added into this series, original patch is here: https://lore.kernel.org/all/20230609094532.562934-1-ilias.apalodimas@linaro....
There are two issues in the v6 series and v7 series addresses those.
1) efivar ops is not restored when the tee-supplicant daemon terminates. -> As the following patch says, user must remove the device before terminating tee-supplicant daemon. https://lore.kernel.org/all/20230728134832.326467-1-sumit.garg@linaro.org/
2) cause panic when someone remounts the efivarfs as RW even if SetVariable is not supported -> The fifth patch addresses this issue. "[PATCH v7 5/5] efivarfs: force RO when remounting if SetVariable is not supported"
v5 -> v6 - new patch #4 is added in this series, #1-#3 patches are unchanged. automatically update super block flag when the efivarops support SetVariable runtime service, so that user does not need to manually remount the efivarfs as RW.
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 EFI_UNSUPPORTED - 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. - PTA_STMM_CMD_COMMUNICATE -> PTA_STMM_CMD_COMMUNICATE - 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
Ilias Apalodimas (1): efivarfs: force RO when remounting if SetVariable is not supported
Masahisa Kojima (4): efi: expose efivar generic ops register function efi: Add EFI_ACCESS_DENIED status code efi: Add tee-based EFI variable driver efivarfs: automatically update super block flag
drivers/firmware/efi/Kconfig | 15 + drivers/firmware/efi/Makefile | 1 + drivers/firmware/efi/efi.c | 18 + drivers/firmware/efi/stmm/mm_communication.h | 236 +++++++ drivers/firmware/efi/stmm/tee_stmm_efi.c | 616 +++++++++++++++++++ drivers/firmware/efi/vars.c | 8 + fs/efivarfs/super.c | 45 ++ include/linux/efi.h | 12 + 8 files changed, 951 insertions(+) create mode 100644 drivers/firmware/efi/stmm/mm_communication.h create mode 100644 drivers/firmware/efi/stmm/tee_stmm_efi.c
base-commit: 5329aa5101f73c451bcd48deaf3f296685849d9c