[PATCH v10 0/4] generic TEE subsystem

Jens Wiklander
2016-06-01T12:41:43Z

Hi,

[TL;DR; This patch set needs more review, if you're using OP-TEE please
help reviewing.]

This patch set introduces a generic TEE subsystem. The TEE subsystem will
contain drivers for various TEE implementations. A TEE (Trusted Execution
Environment) is a trusted OS running in some secure environment, for
example, TrustZone on ARM CPUs, or a separate secure co-processor etc.

Regarding use cases, TrustZone has traditionally been used for
offloading secure tasks to the secure world. Examples include:
- Secure key handling where the OS may or may not have direct access to key
material.
- E-commerce and payment technologies. Credentials, credit card numbers etc
could be stored in a more secure environment.
- Trusted User Interface (TUI) to ensure that no-one can snoop PIN-codes
etc.
- Secure boot to ensure that loaded binaries haven’t been tampered with.
It’s not strictly needed for secure boot, but you could enhance security
by leveraging a TEE during boot.
- Digital Rights Management (DRM), the studios provides content with
different resolution depending on the security of the device. Higher
security means higher resolution.

A TEE could also be used in existing and new technologies. For example IMA
(Integrity Measurement Architecture) which has been in the kernel for quite
a while. Today you can enhance security by using a TPM-chip to sign the IMA
measurement list. This is something that you also could do by leveraging a
TEE.

Another example could be in 2-factor authentication which is becoming
increasingly more important. FIDO (https://fidoalliance.org) for example
are using public key cryptography in their 2-factor authentication standard
(U2F). With FIDO, a private and public key pair will be generated for every
site you visit and the private key should never leave the local device.
This is an example where you could use secure storage in a TEE for the
private key.

Today you will find a quite a few different out of tree implementations of
TEE drivers which tends to fragment the TEE ecosystem and development. We
think it would be a good idea to have a generic TEE driver integrated in
the kernel which would serve as a base for several different TEE solutions,
no matter if they are on-chip like TrustZone or if they are on a separate
crypto co-processor.

To develop this TEE subsystem we have been using the open source TEE called
OP-TEE (https://github.com/OP-TEE/optee_os) and therefore this would be the
first TEE solution supported by this new subsystem. OP-TEE is a
GlobalPlatform compliant TEE, however this TEE subsystem is not limited to
only GlobalPlatform TEEs, instead we have tried to design it so that it
should work with other TEE solutions also.

"tee: generic TEE subsystem" brings in the generic TEE subsystem which
helps when writing a driver for a specific TEE, for example, OP-TEE.

"tee: add OP-TEE driver" is an OP-TEE driver which uses the subsystem to do
its work.

This patch set has been prepared in cooperation with Javier González who
proposed "Generic TrustZone Driver in Linux Kernel" patches 28 Nov 2014,
https://lwn.net/Articles/623380/ . We've since then changed the scope to
TEE instead of TrustZone.

We have discussed the design on tee-dev@lists.linaro.org (archive at
https://lists.linaro.org/pipermail/tee-dev/) with people from other
companies, including Valentin Manea <valentin.manea@huawei.com>,
Emmanuel MICHEL <emmanuel.michel@st.com>,
Jean-michel DELORME <jean-michel.delorme@st.com>,
and Joakim Bech <joakim.bech@linaro.org>. Our main concern has been to
agree on something that is generic enough to support many different
TEEs while still keeping the interface together.

v10:
* Rebased on v4.7-rc1
* Addressed private review comments from Nishanth Menon
* Optee driver only accepts one supplicant process on the privileged device
* Optee driver avoids long delayed releases of shm objects
* Added more comments on functions and structs

v9:
* Rebased on v4.6-rc1
* Acked-by: Andreas Dannenberg <dannenberg@ti.com>
* Addressed comments from Al Viro how file descriptors are passed to
user space
* Addressed comments from Randy Dunlap on documentation
* Changed license for include/uapi/linux/tee.h

v8:
* Rebased on v4.5-rc3
* dt/bindings: add bindings for optee
Acked-by: Rob Herring <robh@kernel.org>
* Fixes build error for X86
* Fixes spell error in "dt/bindings: add bindings for optee"

v7:
* Rebased on v4.5-rc2
* Moved the ARM SMC Calling Convention support into a separate patch
set, which is now merged

v6:
* Rebased on v4.3-rc7
* Changed smccc interface to let the compiler marshal most of the
parameters
* Added ARCH64 capability for smccc interface
* Changed the PSCI firmware calls (both arm and arm64) to use the new
generic smccc interface instead instead of own assembly functions.
* Move optee DT bindings to below arm/firmware
* Defines method for OP-TEE driver to call secure world in DT, smc or hvc
* Exposes implementation id of a TEE driver in sysfs
to easily spawn corresponding tee-supplicant when device is ready
* Update OP-TEE Message Protocol to better cope with fragmented physical
memory
* Read time directly from OP-TEE driver instead of forwarding the RPC
request to tee-supplicant

v5:
* Replaced kref reference counting for the device with a size_t instead as
the counter is always protected by a mutex

v4:
* Rebased on 4.1
* Redesigned the synchronization around entry exit of normal SMC
* Replaced rwsem on the driver instance with kref and completion since
rwsem wasn't intended to be used in this way
* Expanded the TEE_IOCTL_PARAM_ATTR_TYPE_MASK to make room for
future additional parameter types
* Documents TEE subsystem and OP-TEE driver
* Replaced TEE_IOC_CMD with TEE_IOC_OPEN_SESSION, TEE_IOC_INVOKE,
TEE_IOC_CANCEL and TEE_IOC_CLOSE_SESSION
* DT bindings in a separate patch
* Assembly parts moved to arch/arm and arch/arm64 respectively, in a
separate patch
* Redefined/clarified the meaning of OPTEE_SMC_SHM_CACHED
* Removed CMA usage to limit the scope of the patch set

v3:
* Rebased on 4.1-rc3 (dma_buf_export() API change)
* A couple of small sparse fixes
* Documents bindings for OP-TEE driver
* Updated MAINTAINERS

v2:
* Replaced the stubbed OP-TEE driver with a real OP-TEE driver
* Removed most APIs not needed by OP-TEE in current state
* Update Documentation/ioctl/ioctl-number.txt with correct path to tee.h
* Rename tee_shm_pool_alloc_cma() to tee_shm_pool_alloc()
* Moved tee.h into include/uapi/linux/
* Redefined tee.h IOCTL macros to be directly based on _IOR and friends
* Removed version info on the API to user space, a data blob which
can contain an UUID is left for user space to be able to tell which
protocol to use in TEE_IOC_CMD
* Changed user space exposed structures to only have types with __ prefix
* Dropped THIS_MODULE from tee_fops
* Reworked how the driver is registered and ref counted:
- moved from using an embedded struct miscdevice to an embedded struct
device.
- uses an struct rw_semaphore as synchronization for driver detachment
- uses alloc/register pattern from TPM

Thanks,
Jens

Jens Wiklander (4):
dt/bindings: add bindings for optee
tee: generic TEE subsystem
tee: add OP-TEE driver
Documentation: tee subsystem and op-tee driver

Documentation/00-INDEX | 2 +
.../bindings/arm/firmware/linaro,optee-tz.txt | 31 +
.../devicetree/bindings/vendor-prefixes.txt | 1 +
Documentation/ioctl/ioctl-number.txt | 1 +
Documentation/tee.txt | 118 +++
MAINTAINERS | 13 +
drivers/Kconfig | 2 +
drivers/Makefile | 1 +
drivers/tee/Kconfig | 19 +
drivers/tee/Makefile | 4 +
drivers/tee/optee/Kconfig | 8 +
drivers/tee/optee/Makefile | 5 +
drivers/tee/optee/call.c | 422 ++++++++++
drivers/tee/optee/core.c | 553 +++++++++++++
drivers/tee/optee/optee_msg.h | 435 ++++++++++
drivers/tee/optee/optee_private.h | 181 +++++
drivers/tee/optee/optee_smc.h | 418 ++++++++++
drivers/tee/optee/rpc.c | 401 ++++++++++
drivers/tee/optee/supp.c | 241 ++++++
drivers/tee/tee.c | 877 +++++++++++++++++++++
drivers/tee/tee_private.h | 125 +++
drivers/tee/tee_shm.c | 347 ++++++++
drivers/tee/tee_shm_pool.c | 155 ++++
include/linux/tee_drv.h | 273 +++++++
include/uapi/linux/tee.h | 400 ++++++++++
25 files changed, 5033 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.txt
create mode 100644 Documentation/tee.txt
create mode 100644 drivers/tee/Kconfig
create mode 100644 drivers/tee/Makefile
create mode 100644 drivers/tee/optee/Kconfig
create mode 100644 drivers/tee/optee/Makefile
create mode 100644 drivers/tee/optee/call.c
create mode 100644 drivers/tee/optee/core.c
create mode 100644 drivers/tee/optee/optee_msg.h
create mode 100644 drivers/tee/optee/optee_private.h
create mode 100644 drivers/tee/optee/optee_smc.h
create mode 100644 drivers/tee/optee/rpc.c
create mode 100644 drivers/tee/optee/supp.c
create mode 100644 drivers/tee/tee.c
create mode 100644 drivers/tee/tee_private.h
create mode 100644 drivers/tee/tee_shm.c
create mode 100644 drivers/tee/tee_shm_pool.c
create mode 100644 include/linux/tee_drv.h
create mode 100644 include/uapi/linux/tee.h

--
1.9.1