Re: [PATCH v8 0/4] generic TEE subsystem

[Andreas Dannenberg]

On Thu, Feb 11, 2016 at 06:14:33PM +0100, Jens Wiklander wrote:
> Hi,
> 
> 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 havenât been tampered with.
>   Itâs 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 GonzÃlez 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@xxxxxxxxxxxxxxxx (archive at
> https://lists.linaro.org/pipermail/tee-dev/) with people from other
> companies, including Valentin Manea <valentin.manea@xxxxxxxxxx>,
> Emmanuel MICHEL <emmanuel.michel@xxxxxx>,
> Jean-michel DELORME <jean-michel.delorme@xxxxxx>,
> and Joakim Bech <joakim.bech@xxxxxxxxxx>. Our main concern has been to
> agree on something that is generic enough to support many different
> TEEs while still keeping the interface together.
> 
> v8:
> * Rebased on v4.5-rc3
> * dt/bindings: add bindings for optee
>   Acked-by: Rob Herring <robh@xxxxxxxxxx>
> * Fixes build error for X86
> * Fixes spell error in "dt/bindings: add bindings for optee"

Jens,
thanks for the updated series and the continued work on this. I've
recently starting testing/experimenting with this in the context of
Kernel 4.4 (will try latest Kernel as a next step) and have not found any
issues so far. This is an ongoing effort and I'll provide feedback as I
encounter anything notable.

But I also wanted to use this opportunity to express that from a TI and
TI customer point of view (and probably beyond that) this TEE subsystem
support is seen as an important building block for a number real-world
use cases involving security.


Acked-by: Andreas Dannenberg <dannenberg@xxxxxx>


Regards,

--
Andreas Dannenberg
Texas Instruments Inc

> 
> 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                              | 117 +++
>  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                           | 400 ++++++++++
>  drivers/tee/optee/core.c                           | 522 ++++++++++++
>  drivers/tee/optee/optee_msg.h                      | 423 ++++++++++
>  drivers/tee/optee/optee_private.h                  | 146 ++++
>  drivers/tee/optee/optee_smc.h                      | 418 ++++++++++
>  drivers/tee/optee/rpc.c                            | 322 ++++++++
>  drivers/tee/optee/supp.c                           | 212 +++++
>  drivers/tee/tee.c                                  | 873 +++++++++++++++++++++
>  drivers/tee/tee_private.h                          |  80 ++
>  drivers/tee/tee_shm.c                              | 324 ++++++++
>  drivers/tee/tee_shm_pool.c                         | 133 ++++
>  include/linux/tee_drv.h                            | 299 +++++++
>  include/uapi/linux/tee.h                           | 383 +++++++++
>  25 files changed, 4739 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
>