| Message ID | 20220723224949.1089973-1-luzmaximilian@gmail.com |
|---|---|
| Headers | show |
| Series | firmware: Add support for Qualcomm UEFI Secure Application | expand |
On Sun, Jul 24, 2022 at 12:49:45AM +0200, Maximilian Luz wrote: > On modern Qualcomm platforms, access to EFI variables is restricted to > the secure world / TrustZone, i.e. the Trusted Execution Environment > (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we > therefore need to talk to the UEFI Secure Application (uefisecapp), > residing in the TrEE. The whole point of UEFI is providing a standard interface. Why can't the UEFI implementation call the TEE itself? I'm not sure custom interfaces is something we want. > This series adds support for accessing EFI variables on those platforms. > > To do this, we first need to add some SCM call functions used to manage > and talk to Secure Applications. A very small subset of this interface > is added in the second patch (whereas the first one exports the required > functions for that). Interface specifications are extracted from [1]. > While this does not (yet) support re-entrant SCM calls (including > callbacks and listeners), this is enough to talk to the aforementioned > uefisecapp on a couple of platforms (I've tested this on a Surface Pro X > and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo > Yoga C630 devices). What does Windows do on these devices? I'm surprised something like this would fly with Microsoft. Rob
On 7/25/22 21:27, Rob Herring wrote: > On Sun, Jul 24, 2022 at 12:49:45AM +0200, Maximilian Luz wrote: >> On modern Qualcomm platforms, access to EFI variables is restricted to >> the secure world / TrustZone, i.e. the Trusted Execution Environment >> (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we >> therefore need to talk to the UEFI Secure Application (uefisecapp), >> residing in the TrEE. > > The whole point of UEFI is providing a standard interface. Why can't the > UEFI implementation call the TEE itself? > > I'm not sure custom interfaces is something we want. Unfortunately, I'm not a Qualcomm engineer and in no way affiliated with them. So I probably can't convince them otherwise. Believe me, I'd like to :/ First: The uefisecapp-driver is based on reverse-engineering. So please take things below with a grain of salt, I may be wrong. I've tried to lay this out in a bit more detail in patch 3, but I'll try to be more precise here: For some reason unknown to me, Qualcomm decided to lock away UEFI variable access via their TrEE framework for applications running in the TrustZone (or whatever that is exactly). To call to TrEE applications (like uefisecapp), they use SCM calls. Those SCM calls unfortunately can be a bit more complex. As far as I can tell, you essentially call to some hypervisor in the TrustZone which redistributes them (if necessary) to the respective application. Their downstream driver for that is at [1] and supports callbacks and re-entrant calls. As far as I can tell, the latter means that you can't run multiple SCM calls in parallel (at least not to that TzOS/TrEE interface) and can only ever have one "client" performing them. And as you can only ever have one entity performing those SCM calls, you cannot have both UEFI and the kernel doing them. To me, it seems to be a deliberate decision by Qualcomm to return EFI_UNSUPPORTED from the GetVariable etc. calls after exiting boot services. They do work just fine before that. Essentially exiting boot services transfers ownership of that SCM interface from UEFI to the kernel. Note: uefisecapp is also not the only TrEE application in use by those kinds of devices. For example, on the SC8180X based Surface Pro X that I'm using, there are at least an app for the TPM, a bunch of apps for HDCP, some winsecapp, and as far as I can tell also other cryptographic interfaces. I've tried to collect my findings about those in [2]. >> This series adds support for accessing EFI variables on those platforms. >> >> To do this, we first need to add some SCM call functions used to manage >> and talk to Secure Applications. A very small subset of this interface >> is added in the second patch (whereas the first one exports the required >> functions for that). Interface specifications are extracted from [1]. >> While this does not (yet) support re-entrant SCM calls (including >> callbacks and listeners), this is enough to talk to the aforementioned >> uefisecapp on a couple of platforms (I've tested this on a Surface Pro X >> and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo >> Yoga C630 devices). > > What does Windows do on these devices? I'm surprised something like this > would fly with Microsoft. It looks like Microsoft accepts this. They even seem to have some sort of interface for EFI variables via trusted execution environments: [3]. This is essentially what the QcTrEE8180.sys driver I've reverse engineered this from seems to provide. So unless there's some way to make EFI variables work via the standard functions that I've missed, I don't see any alternatives. I think it's fairly unlikely that we can convince Qualcomm to make their UEFI implementation behave properly (variables are not the only issue, it seems that other functions are either partially or completely broken in some way or another...) and then also push updates for a bunch of devices (e.g. the Lenovo C630 also using this stuff is discontinued, as far as I can tell). I am open to suggestions though... Note that this series also doesn't really introduce a new interface for EFI variables themselves to the kernel. It relies on the existing efivars_register() / efivars_unregister() functions and the interface provided by them to enable access to EFI variables. So we already do have a "workaround" for broken UEFI variable access in the kernel. Regards, Max [1]: https://git.codelinaro.org/clo/la/kernel/msm-4.14/-/blob/auto-kernel.lnx.4.14.c34/drivers/misc/qseecom.c [2]: https://github.com/linux-surface/surface-pro-x/issues/37 [3]: https://github.com/tpn/winsdk-10/blob/9b69fd26ac0c7d0b83d378dba01080e93349c2ed/Include/10.0.16299.0/km/treevariableservice.h#L11-L12
Hi Maximilian, On 23/07/2022 23:49, Maximilian Luz wrote: > On modern Qualcomm platforms, access to EFI variables is restricted to > the secure world / TrustZone, i.e. the Trusted Execution Environment > (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we > therefore need to talk to the UEFI Secure Application (uefisecapp), > residing in the TrEE. > > This series adds support for accessing EFI variables on those platforms. > > To do this, we first need to add some SCM call functions used to manage > and talk to Secure Applications. A very small subset of this interface > is added in the second patch (whereas the first one exports the required > functions for that). Interface specifications are extracted from [1]. > While this does not (yet) support re-entrant SCM calls (including > callbacks and listeners), this is enough to talk to the aforementioned > uefisecapp on a couple of platforms (I've tested this on a Surface Pro X > and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo > Yoga C630 devices). > > The third patch adds a client driver for uefisecapp, installing the > respective efivar operations. The application interface has been reverse > engineered from the Windows QcTrEE8180.sys driver. > > Apart from uefisecapp, there are more Secure Applications running that > we might want to support in the future. For example, on the Surface Pro > X (sc8180x-based), the TPM is also managed via one. > > I'm not sure whether this should go to drivers/firmware or to > drivers/soc/qcom. I've put this into firmware as all of this is > essentially an interface to the secure firmware running in the TrustZone > (and SCM stuff is handled here already), but please let me know if I > should move this. From what I see so far is that this is adapted from downstream qseecom driver, this approach could work for a limited usecases but not scalable, as we cannot add drivers for each Qualcomm specific TA in kernel. This has to be handled in much generic way using Linux TEE framework, and let the userspace side deal with TA specific bits. AFAIU, Qualcomm is moving away from qseecom interface to new smc-invoke interface, most of Qualcomm SoCs starting from SDM660 already have support to this. This interface provides a better abstracted IPC mechanism to talk to TA. Most of these TA specific interfaces are packed in closed userspace source. Having said that QTEE smcinvoke driver can be modeled as a proper TEE driver with Userspace driving the TA specific bits using existing tee uapis. This also brings in other features like loading, Listeners aka callbacks, secure memory allocations..etc. In the past, I have tried to do a prototype of this smcinvoke driver as a proper tee driver, incase you are interested patches are at https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/log/?h=tracking-qcomlt-qcomtee Plan is to discuss with Qualcomm and send it for upstream review. I think its worth exploring if uefisecapp can talk smcinvoke. I can ping Qualcomm engineers to see if that is doable. thanks, Srini > > Regards, > Max > > [1]: https://git.codelinaro.org/clo/la/kernel/msm-4.14/-/blob/auto-kernel.lnx.4.14.c34/drivers/misc/qseecom.c > > Maximilian Luz (4): > firmware: qcom_scm: Export SCM call functions > firmware: Add support for Qualcomm Trusted Execution Environment SCM > calls > firmware: Add support for Qualcomm UEFI Secure Application > dt-bindings: firmware: Add Qualcomm UEFI Secure Application client > > .../firmware/qcom,tee-uefisecapp.yaml | 38 + > MAINTAINERS | 14 + > drivers/firmware/Kconfig | 20 + > drivers/firmware/Makefile | 2 + > drivers/firmware/qcom_scm.c | 118 ++- > drivers/firmware/qcom_scm.h | 47 -- > drivers/firmware/qcom_tee.c | 213 +++++ > drivers/firmware/qcom_tee_uefisecapp.c | 761 ++++++++++++++++++ > include/linux/qcom_scm.h | 49 ++ > include/linux/qcom_tee.h | 179 ++++ > 10 files changed, 1355 insertions(+), 86 deletions(-) > create mode 100644 Documentation/devicetree/bindings/firmware/qcom,tee-uefisecapp.yaml > create mode 100644 drivers/firmware/qcom_tee.c > create mode 100644 drivers/firmware/qcom_tee_uefisecapp.c > create mode 100644 include/linux/qcom_tee.h >
On 8/2/22 13:51, Srinivas Kandagatla wrote: > Hi Maximilian, > > On 23/07/2022 23:49, Maximilian Luz wrote: >> On modern Qualcomm platforms, access to EFI variables is restricted to >> the secure world / TrustZone, i.e. the Trusted Execution Environment >> (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we >> therefore need to talk to the UEFI Secure Application (uefisecapp), >> residing in the TrEE. >> >> This series adds support for accessing EFI variables on those platforms. >> >> To do this, we first need to add some SCM call functions used to manage >> and talk to Secure Applications. A very small subset of this interface >> is added in the second patch (whereas the first one exports the required >> functions for that). Interface specifications are extracted from [1]. >> While this does not (yet) support re-entrant SCM calls (including >> callbacks and listeners), this is enough to talk to the aforementioned >> uefisecapp on a couple of platforms (I've tested this on a Surface Pro X >> and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo >> Yoga C630 devices). >> >> The third patch adds a client driver for uefisecapp, installing the >> respective efivar operations. The application interface has been reverse >> engineered from the Windows QcTrEE8180.sys driver. >> >> Apart from uefisecapp, there are more Secure Applications running that >> we might want to support in the future. For example, on the Surface Pro >> X (sc8180x-based), the TPM is also managed via one. >> >> I'm not sure whether this should go to drivers/firmware or to >> drivers/soc/qcom. I've put this into firmware as all of this is >> essentially an interface to the secure firmware running in the TrustZone >> (and SCM stuff is handled here already), but please let me know if I >> should move this. > > From what I see so far is that this is adapted from downstream qseecom driver, this approach could work for a limited usecases but not scalable, as we cannot add drivers for each Qualcomm specific TA in kernel. > This has to be handled in much generic way using Linux TEE framework, and let the userspace side deal with TA specific bits. I generally agree with the sentiment, however UEFI variables should IMHO be handled by the kernel. Moving handling of those to userspace breaks things like EFI-based pstore and efivarfs. The latter will in turn break some user-space tools (most notably efibootmgr used by e.g. GRUB and I think fwupdmgr which needs to set some capsule variables). Ideally, we would find a way to not break these, i.e. have them work out-of-the-box. A similar argumentation might apply to the TPM app. > AFAIU, Qualcomm is moving away from qseecom interface to new smc-invoke interface, most of Qualcomm SoCs starting from SDM660 already have support to this. > > This interface provides a better abstracted IPC mechanism to talk to TA. Most of these TA specific interfaces are packed in closed userspace source. > Having said that QTEE smcinvoke driver can be modeled as a proper TEE driver with Userspace driving the TA specific bits using existing tee uapis. > This also brings in other features like loading, Listeners aka callbacks, secure memory allocations..etc. > > In the past, I have tried to do a prototype of this smcinvoke driver as a proper tee driver, incase you are interested patches are at https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/log/?h=tracking-qcomlt-qcomtee > Plan is to discuss with Qualcomm and send it for upstream review. Thanks for this information! So as far as I understand it, this is currently an interface to user-space only, i.e. does not allow in-kernel drivers for apps? It would be great if this could then be extended to handle (the bare minimum of) in-kernel drivers (i.e. only things that the kernel itself needs, like EFI variables). Alternatively, I'm happy to hear suggestions on how we not break the aforementioned things while moving handling off to userspace. > I think its worth exploring if uefisecapp can talk smcinvoke. > I can ping Qualcomm engineers to see if that is doable. I think that would be great! Thanks! Regards, Max
On Tue, 2 Aug 2022 at 15:22, Maximilian Luz <luzmaximilian@gmail.com> wrote: > > > > On 8/2/22 13:51, Srinivas Kandagatla wrote: > > Hi Maximilian, > > > > On 23/07/2022 23:49, Maximilian Luz wrote: > >> On modern Qualcomm platforms, access to EFI variables is restricted to > >> the secure world / TrustZone, i.e. the Trusted Execution Environment > >> (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we > >> therefore need to talk to the UEFI Secure Application (uefisecapp), > >> residing in the TrEE. > >> > >> This series adds support for accessing EFI variables on those platforms. > >> > >> To do this, we first need to add some SCM call functions used to manage > >> and talk to Secure Applications. A very small subset of this interface > >> is added in the second patch (whereas the first one exports the required > >> functions for that). Interface specifications are extracted from [1]. > >> While this does not (yet) support re-entrant SCM calls (including > >> callbacks and listeners), this is enough to talk to the aforementioned > >> uefisecapp on a couple of platforms (I've tested this on a Surface Pro X > >> and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo > >> Yoga C630 devices). > >> > >> The third patch adds a client driver for uefisecapp, installing the > >> respective efivar operations. The application interface has been reverse > >> engineered from the Windows QcTrEE8180.sys driver. > >> > >> Apart from uefisecapp, there are more Secure Applications running that > >> we might want to support in the future. For example, on the Surface Pro > >> X (sc8180x-based), the TPM is also managed via one. > >> > >> I'm not sure whether this should go to drivers/firmware or to > >> drivers/soc/qcom. I've put this into firmware as all of this is > >> essentially an interface to the secure firmware running in the TrustZone > >> (and SCM stuff is handled here already), but please let me know if I > >> should move this. > > > > From what I see so far is that this is adapted from downstream qseecom driver, this approach could work for a limited usecases but not scalable, as we cannot add drivers for each Qualcomm specific TA in kernel. > > This has to be handled in much generic way using Linux TEE framework, and let the userspace side deal with TA specific bits. > > I generally agree with the sentiment, however UEFI variables should IMHO be > handled by the kernel. Moving handling of those to userspace breaks things like > EFI-based pstore and efivarfs. The latter will in turn break some user-space > tools (most notably efibootmgr used by e.g. GRUB and I think fwupdmgr which > needs to set some capsule variables). Ideally, we would find a way to not break > these, i.e. have them work out-of-the-box. > Only capsule-on-disk requires SetVariable() at runtime, and I doubt whether these platforms implement any of that. > A similar argumentation might apply to the TPM app. > There is a difference, though - the TPM is modeled as a device and runtime access to it is implemented as a device driver, which is only accessed from user space. > > AFAIU, Qualcomm is moving away from qseecom interface to new smc-invoke interface, most of Qualcomm SoCs starting from SDM660 already have support to this. > > > > This interface provides a better abstracted IPC mechanism to talk to TA. Most of these TA specific interfaces are packed in closed userspace source. > > Having said that QTEE smcinvoke driver can be modeled as a proper TEE driver with Userspace driving the TA specific bits using existing tee uapis. > > This also brings in other features like loading, Listeners aka callbacks, secure memory allocations..etc. > > > > In the past, I have tried to do a prototype of this smcinvoke driver as a proper tee driver, incase you are interested patches are at https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/log/?h=tracking-qcomlt-qcomtee > > Plan is to discuss with Qualcomm and send it for upstream review. > > Thanks for this information! So as far as I understand it, this is currently an > interface to user-space only, i.e. does not allow in-kernel drivers for apps? > It would be great if this could then be extended to handle (the bare minimum > of) in-kernel drivers (i.e. only things that the kernel itself needs, like EFI > variables). Alternatively, I'm happy to hear suggestions on how we not break > the aforementioned things while moving handling off to userspace. > > > I think its worth exploring if uefisecapp can talk smcinvoke. > > I can ping Qualcomm engineers to see if that is doable. > > I think that would be great! Thanks! > > Regards, > Max
On modern Qualcomm platforms, access to EFI variables is restricted to the secure world / TrustZone, i.e. the Trusted Execution Environment (TrEE or TEE) as Qualcomm seems to call it. To access EFI variables, we therefore need to talk to the UEFI Secure Application (uefisecapp), residing in the TrEE. This series adds support for accessing EFI variables on those platforms. To do this, we first need to add some SCM call functions used to manage and talk to Secure Applications. A very small subset of this interface is added in the second patch (whereas the first one exports the required functions for that). Interface specifications are extracted from [1]. While this does not (yet) support re-entrant SCM calls (including callbacks and listeners), this is enough to talk to the aforementioned uefisecapp on a couple of platforms (I've tested this on a Surface Pro X and heard reports from Lenovo Flex 5G, Lenovo Thinkpad x13s, and Lenovo Yoga C630 devices). The third patch adds a client driver for uefisecapp, installing the respective efivar operations. The application interface has been reverse engineered from the Windows QcTrEE8180.sys driver. Apart from uefisecapp, there are more Secure Applications running that we might want to support in the future. For example, on the Surface Pro X (sc8180x-based), the TPM is also managed via one. I'm not sure whether this should go to drivers/firmware or to drivers/soc/qcom. I've put this into firmware as all of this is essentially an interface to the secure firmware running in the TrustZone (and SCM stuff is handled here already), but please let me know if I should move this. Regards, Max [1]: https://git.codelinaro.org/clo/la/kernel/msm-4.14/-/blob/auto-kernel.lnx.4.14.c34/drivers/misc/qseecom.c Maximilian Luz (4): firmware: qcom_scm: Export SCM call functions firmware: Add support for Qualcomm Trusted Execution Environment SCM calls firmware: Add support for Qualcomm UEFI Secure Application dt-bindings: firmware: Add Qualcomm UEFI Secure Application client .../firmware/qcom,tee-uefisecapp.yaml | 38 + MAINTAINERS | 14 + drivers/firmware/Kconfig | 20 + drivers/firmware/Makefile | 2 + drivers/firmware/qcom_scm.c | 118 ++- drivers/firmware/qcom_scm.h | 47 -- drivers/firmware/qcom_tee.c | 213 +++++ drivers/firmware/qcom_tee_uefisecapp.c | 761 ++++++++++++++++++ include/linux/qcom_scm.h | 49 ++ include/linux/qcom_tee.h | 179 ++++ 10 files changed, 1355 insertions(+), 86 deletions(-) create mode 100644 Documentation/devicetree/bindings/firmware/qcom,tee-uefisecapp.yaml create mode 100644 drivers/firmware/qcom_tee.c create mode 100644 drivers/firmware/qcom_tee_uefisecapp.c create mode 100644 include/linux/qcom_tee.h