Re: [PATCH v12 RESEND 0/4] generic TEE subsystem

["Andrew F. Davis" <afd@ti.com>]

On 10/29/2016 04:46 AM, Jens Wiklander wrote:
> On Fri, Oct 28, 2016 at 10:43:24AM -0500, Andrew F. Davis wrote:
>> On 10/28/2016 05:19 AM, 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 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.
>>>
>>
>> The above is my biggest concern with this whole subsystem, to me it
>> still feels very OPTEE specific. As much as I would love to believe
>> OPTEE will be the end-all TEE, I'm sure we soon will start to see wider
>> use of vendor TEEs (like TI's own legacy Trustzone thing we are hoping
>> to depreciate with OPTEE moving forward), possibly Google's Trusty TEE,
>> and whatever Intel/AMD are cooking up for x86.
> 
> I'd rather say that it's slightly GlobalPlatform specific, but a bit
> more flexible.
> 
>>
>> As we all know when things are upstreamed we lose the ability to make
>> radical changes easily, especially to full subsystems. What happens when
>> this framework, built with only one existing TEE, built by the one
>> existing TEE's devs, is not as flexible as we need when other TEEs start
>> rolling out?
> 
> Initially the TEE subsystem was much more flexible and was criticized
> for that.
> 

That's rather strange, I haven't been following this from the start so I
will just take your word that this is where the community wants this
subsystem to go.

>>
>> Do we see this as a chicken and egg situation, or is there any harm
>> beyond the pains of supporting an out-of-tree driver for a while, to
>> wait until we have at least one other TEE to add to this subsystem
>> before merging?
> 
> This proposal is the bare minimum to have something useful. On top of
> this there's more things we'd like to add, for example an in-kernel API
> for accessing the TEE and secure buffer handling. The way we're dealing
> with shared memory need to be improved to better support multiple guests
> communicating with one TEE.
> 
> What we can do now with the subsystem now is somewhat limited by the
> fact that we're trying to upstream it and want to do that it in
> manageable increments.
> 

Fair enough.

For now this series is being used in our production SDKs so it has at
least some basic testing from us, so for the whole series:

Tested-by: Andrew F. Davis <afd@ti.com>

> Thanks,
> Jens
> 
>>
>> This may also help with the perceived lack of reviewers for this series.
>>
>> Thanks,
>> Andrew
>>
>>> "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.
>>>
>>> v12-resend:
>>> * Rebased on v4.9-rc2
>>>
>>> v12:
>>> * Rebased on v4.8-rc5
>>> * Addressed review comments from Andrew F. Davis
>>> * Removed Acked-by: Andreas Dannenberg <dannenberg@ti.com> as the
>>>   mail bounces
>>> * Bugfix possible null dereference in error cleanup path of
>>>   optee_probe().
>>> * Bugfix optee_from_msg_param() when calculating offset of memref
>>>   into a shared memory object
>>>
>>> v11:
>>> * Rebased on v4.8-rc3
>>> * Addressed review comments from Nishanth Menon
>>> * Made the TEE framework available as a loadable module.
>>> * Reviewed-by: Javier González <javier@javigon.com>
>>> * Zeroes shared memory on allocation to avoid information leakage
>>> * Links shared memory objects to context to avoid stealing of shared memory
>>>   object from an unrelated process
>>> * Allow RPC interruption if supplicant is unavailable
>>>
>>> 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                                |  18 +
>>>  drivers/tee/Makefile                               |   5 +
>>>  drivers/tee/optee/Kconfig                          |   7 +
>>>  drivers/tee/optee/Makefile                         |   5 +
>>>  drivers/tee/optee/call.c                           | 435 ++++++++++
>>>  drivers/tee/optee/core.c                           | 598 ++++++++++++++
>>>  drivers/tee/optee/optee_msg.h                      | 435 ++++++++++
>>>  drivers/tee/optee/optee_private.h                  | 185 +++++
>>>  drivers/tee/optee/optee_smc.h                      | 446 ++++++++++
>>>  drivers/tee/optee/rpc.c                            | 404 +++++++++
>>>  drivers/tee/optee/supp.c                           | 273 +++++++
>>>  drivers/tee/tee_core.c                             | 901 +++++++++++++++++++++
>>>  drivers/tee/tee_private.h                          | 129 +++
>>>  drivers/tee/tee_shm.c                              | 357 ++++++++
>>>  drivers/tee/tee_shm_pool.c                         | 158 ++++
>>>  include/linux/tee_drv.h                            | 278 +++++++
>>>  include/uapi/linux/tee.h                           | 403 +++++++++
>>>  25 files changed, 5206 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_core.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
>>>