Kojima-san,
I found some time to do some extended testing here's what I found
Switching the permissions from RO->RW when the supplicant is started works correctly # mount | grep efiv efivarfs on /sys/firmware/efi/efivars type efivarfs (ro,nosuid,nodev,noexec,relatime) # tee-supplicant -d [ 77.374878] efivars: Unregistered efivars operations [ 77.381604] Use tee-based EFI runtime variable services [ 77.386862] efivars: Registered efivars operations # mount | grep efiv efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,nosuid,nodev,noexec,relatime) I didn't test unbinding yet, but I assume it's going to work fine and remove the efivar ops.
Reading an writing non-authenticated EFI variables seems to work fine. I verified this with U-Boot and the BootOrder changed correctly. # efibootmgr -o 0001,0002,0000 BootCurrent: 0002 BootOrder: 0001,0002,0000 Boot0000* nvme 0:1 Boot0001* nvme 0:2 Boot0002* debian # efibootmgr -o 0002,0000,0001 BootCurrent: 0002 BootOrder: 0002,0000,0001 Boot0000* nvme 0:1 Boot0001* nvme 0:2 Boot0002* debian
Writing authenticated EFI variables works the first time. I also dumped those variables from both Linux and U-Boot and they matched # efi-updatevar -f PK.auth PK # efi-updatevar -f KEK.auth KEK # efi-updatevar -f db.auth db
But removing the PK at runtime fails. # efi-updatevar -f noPK.auth PK # Failed to update PK: Operation not permitted My guess is that the EDK2 code prohibits that, but we need to check why this is happening. I also got similar failures trying to update KEK and db.
But the most worrying thing is this. From Linux program KEK and db # efi-updatevar -f KEK.auth KEK # efi-updatevar -f db.auth db
Reboot the machine and U-Boot complains when it tries to populate the runtime vars with: Loading Linux 6.6.0-rc2-00654-g82a013b37495 ... Loading initial ramdisk ... EFI stub: Booting Linux Kernel... EFI stub: Using DTB from configuration table EFI stub: Exiting boot services... Can't populate EFI variables. No runtime variables will be available <-- This
If you rewrite those vars from the U-Boot shell everything seems to come back to normal => tftp $loadaddr 192.168.49.5:noKEK.auth && setenv -e -nv -bs -rt -at -i $loadaddr:$filesize KEK => tftp $loadaddr 192.168.49.5:nodb.auth && setenv -e -nv -bs -rt -at -i $loadaddr:$filesize db => tftp $loadaddr 192.168.49.5:KEK.auth && setenv -e -nv -bs -rt -at -i $loadaddr:$filesize KEK => tftp $loadaddr 192.168.49.5:db.auth && setenv -e -nv -bs -rt -at -i $loadaddr:$filesize db
Loading Linux 6.6.0-rc2-00654-g82a013b37495 ... Loading initial ramdisk ... EFI stub: Booting Linux Kernel... EFI stub: Using DTB from configuration table EFI stub: Exiting boot services...
Let me know if you need any more information
Regards /Ilias On Fri, Oct 13, 2023 at 04:45:33PM +0900, Masahisa Kojima wrote:
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.
Changelog: 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.
- 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/
- 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 (5): 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 tee: optee: restore efivars ops when tee-supplicant stops
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 | 617 +++++++++++++++++++ drivers/firmware/efi/vars.c | 8 + drivers/tee/optee/supp.c | 4 + fs/efivarfs/super.c | 45 ++ include/linux/efi.h | 13 + 9 files changed, 957 insertions(+) create mode 100644 drivers/firmware/efi/stmm/mm_communication.h create mode 100644 drivers/firmware/efi/stmm/tee_stmm_efi.c
base-commit: b691118f2c44d16b84fc65b8147b33620eb18cac
2.30.2