Adds an SMC call that will pass an OP-TEE binary image to EL3 and
instruct it to load it as the BL32 payload. This works in conjunction
with a feature added to Trusted Firmware for ARMv8 and above
architectures that supports this.
The main purpose of this change is to facilitate updating the OP-TEE
component on devices via a rootfs change rather than having to do a
firmware update. Further details are linked to in the Kconfig file.
Signed-off-by: Jeffrey Kardatzke <[email protected]>
Reviewed-by: Sumit Garg <[email protected]>
Signed-off-by: Jeffrey Kardatzke <[email protected]>
---
Changes in v13:
- Documentation formatting changes
Changes in v12:
- Fixed checkpatch strict issues
Changes in v11:
- Fixed typo in tee.rst documentation
Changes in v10:
- Fixed tee.rst documentation formatting
Changes in v9:
- Add CPU hotplug callback to init on all cores at startup
Changes in v8:
- Renamed params and fixed alignment issue
Changes in v7:
- Added documentation to Documentation/staging/tee.rst
Changes in v6:
- Expanded Kconfig documentation
Changes in v5:
- Renamed config option
- Added runtime warning when config is used
Changes in v4:
- Update commit message
- Added more documentation
- Renamed config option, added ARM64 dependency
Changes in v3:
- Removed state tracking for driver reload
- Check UID of service to verify it needs image load
Changes in v2:
- Fixed compile issue when feature is disabled
- Addressed minor comments
- Added state tracking for driver reload
Documentation/staging/tee.rst | 53 +++++++++++++
drivers/tee/optee/Kconfig | 17 +++++
drivers/tee/optee/optee_msg.h | 12 +++
drivers/tee/optee/optee_smc.h | 24 ++++++
drivers/tee/optee/smc_abi.c | 137 ++++++++++++++++++++++++++++++++++
5 files changed, 243 insertions(+)
diff --git a/Documentation/staging/tee.rst b/Documentation/staging/tee.rst
index 498343c7ab08..22baa077a3b9 100644
--- a/Documentation/staging/tee.rst
+++ b/Documentation/staging/tee.rst
@@ -214,6 +214,57 @@ call is done from the thread assisting the interrupt handler. This is a
building block for OP-TEE OS in secure world to implement the top half and
bottom half style of device drivers.
+OPTEE_INSECURE_LOAD_IMAGE Kconfig option
+----------------------------------------
+
+The OPTEE_INSECURE_LOAD_IMAGE Kconfig option enables the ability to load the
+BL32 OP-TEE image from the kernel after the kernel boots, rather than loading
+it from the firmware before the kernel boots. This also requires enabling the
+corresponding option in Trusted Firmware for Arm. The Trusted Firmware for Arm
+documentation [8] explains the security threat associated with enabling this as
+well as mitigations at the firmware and platform level.
+
+There are additional attack vectors/mitigations for the kernel that should be
+addressed when using this option.
+
+1. Boot chain security.
+
+ * Attack vector: Replace the OP-TEE OS image in the rootfs to gain control of
+ the system.
+
+ * Mitigation: There must be boot chain security that verifies the kernel and
+ rootfs, otherwise an attacker can modify the loaded OP-TEE binary by
+ modifying it in the rootfs.
+
+2. Alternate boot modes.
+
+ * Attack vector: Using an alternate boot mode (i.e. recovery mode), the
+ OP-TEE driver isn't loaded, leaving the SMC hole open.
+
+ * Mitigation: If there are alternate methods of booting the device, such as a
+ recovery mode, it should be ensured that the same mitigations are applied
+ in that mode.
+
+3. Attacks prior to SMC invocation.
+
+ * Attack vector: Code that is executed prior to issuing the SMC call to load
+ OP-TEE can be exploited to then load an alternate OS image.
+
+ * Mitigation: The OP-TEE driver must be loaded before any potential attack
+ vectors are opened up. This should include mounting of any modifiable
+ filesystems, opening of network ports or communicating with external
+ devices (e.g. USB).
+
+4. Blocking SMC call to load OP-TEE.
+
+ * Attack vector: Prevent the driver from being probed, so the SMC call to
+ load OP-TEE isn't executed when desired, leaving it open to being executed
+ later and loading a modified OS.
+
+ * Mitigation: It is recommended to build the OP-TEE driver as builtin driver
+ rather than as a module to prevent exploits that may cause the module to
+ not be loaded.
+
AMD-TEE driver
==============
@@ -309,3 +360,5 @@ References
[6] include/linux/psp-tee.h
[7] drivers/tee/amdtee/amdtee_if.h
+
+[8] https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
index f121c224e682..70898bbd5809 100644
--- a/drivers/tee/optee/Kconfig
+++ b/drivers/tee/optee/Kconfig
@@ -7,3 +7,20 @@ config OPTEE
help
This implements the OP-TEE Trusted Execution Environment (TEE)
driver.
+
+config OPTEE_INSECURE_LOAD_IMAGE
+ bool "Load OP-TEE image as firmware"
+ default n
+ depends on OPTEE && ARM64
+ help
+ This loads the BL32 image for OP-TEE as firmware when the driver is
+ probed. This returns -EPROBE_DEFER until the firmware is loadable from
+ the filesystem which is determined by checking the system_state until
+ it is in SYSTEM_RUNNING. This also requires enabling the corresponding
+ option in Trusted Firmware for Arm. The documentation there explains
+ the security threat associated with enabling this as well as
+ mitigations at the firmware and platform level.
+ https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
+
+ Additional documentation on kernel security risks are at
+ Documentation/staging/tee.rst.
diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
index 70e9cc2ee96b..e8840a82b983 100644
--- a/drivers/tee/optee/optee_msg.h
+++ b/drivers/tee/optee/optee_msg.h
@@ -241,11 +241,23 @@ struct optee_msg_arg {
* 384fb3e0-e7f8-11e3-af63-0002a5d5c51b.
* Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1,
* OPTEE_MSG_UID_2, OPTEE_MSG_UID_3.
+ *
+ * In the case where the OP-TEE image is loaded by the kernel, this will
+ * initially return an alternate UID to reflect that we are communicating with
+ * the TF-A image loading service at that time instead of OP-TEE. That UID is:
+ * a3fbeab1-1246-315d-c7c4-06b9c03cbea4.
+ * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0,
+ * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2,
+ * OPTEE_MSG_IMAGE_LOAD_UID_3.
*/
#define OPTEE_MSG_UID_0 0x384fb3e0
#define OPTEE_MSG_UID_1 0xe7f811e3
#define OPTEE_MSG_UID_2 0xaf630002
#define OPTEE_MSG_UID_3 0xa5d5c51b
+#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1
+#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d
+#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9
+#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4
#define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01
/*
diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
index 73b5e7760d10..7d9fa426505b 100644
--- a/drivers/tee/optee/optee_smc.h
+++ b/drivers/tee/optee/optee_smc.h
@@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result {
unsigned long reserved1;
};
+/*
+ * Load Trusted OS from optee/tee.bin in the Linux firmware.
+ *
+ * WARNING: Use this cautiously as it could lead to insecure loading of the
+ * Trusted OS.
+ * This SMC instructs EL3 to load a binary and execute it as the Trusted OS.
+ *
+ * Call register usage:
+ * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE
+ * a1 Upper 32bit of a 64bit size for the payload
+ * a2 Lower 32bit of a 64bit size for the payload
+ * a3 Upper 32bit of the physical address for the payload
+ * a4 Lower 32bit of the physical address for the payload
+ *
+ * The payload is in the OP-TEE image format.
+ *
+ * Returns result in a0, 0 on success and an error code otherwise.
+ */
+#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2
+#define OPTEE_SMC_CALL_LOAD_IMAGE \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
+ ARM_SMCCC_OWNER_TRUSTED_OS_END, \
+ OPTEE_SMC_FUNCID_LOAD_IMAGE)
+
/*
* Call with struct optee_msg_arg as argument
*
diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
index a1c1fa1a9c28..6e1f023d50c6 100644
--- a/drivers/tee/optee/smc_abi.c
+++ b/drivers/tee/optee/smc_abi.c
@@ -7,10 +7,13 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/arm-smccc.h>
+#include <linux/cpuhotplug.h>
#include <linux/errno.h>
+#include <linux/firmware.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irqdomain.h>
+#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -1149,6 +1152,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
return false;
}
+#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
+static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invoke_fn)
+{
+ struct arm_smccc_res res;
+
+ invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res);
+
+ if (res.a0 == OPTEE_MSG_IMAGE_LOAD_UID_0 &&
+ res.a1 == OPTEE_MSG_IMAGE_LOAD_UID_1 &&
+ res.a2 == OPTEE_MSG_IMAGE_LOAD_UID_2 &&
+ res.a3 == OPTEE_MSG_IMAGE_LOAD_UID_3)
+ return true;
+ return false;
+}
+#endif
+
static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn)
{
union {
@@ -1354,6 +1373,120 @@ static void optee_shutdown(struct platform_device *pdev)
optee_disable_shm_cache(optee);
}
+#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
+
+#define OPTEE_FW_IMAGE "optee/tee.bin"
+
+static optee_invoke_fn *cpuhp_invoke_fn;
+
+static int optee_cpuhp_probe(unsigned int cpu)
+{
+ /*
+ * Invoking a call on a CPU will cause OP-TEE to perform the required
+ * setup for that CPU. Just invoke the call to get the UID since that
+ * has no side effects.
+ */
+ if (optee_msg_api_uid_is_optee_api(cpuhp_invoke_fn))
+ return 0;
+ else
+ return -EINVAL;
+}
+
+static int optee_load_fw(struct platform_device *pdev,
+ optee_invoke_fn *invoke_fn)
+{
+ const struct firmware *fw = NULL;
+ struct arm_smccc_res res;
+ phys_addr_t data_pa;
+ u8 *data_buf = NULL;
+ u64 data_size;
+ u32 data_pa_high, data_pa_low;
+ u32 data_size_high, data_size_low;
+ int rc;
+ int hp_state;
+
+ if (!optee_msg_api_uid_is_optee_image_load(invoke_fn))
+ return 0;
+
+ rc = request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev);
+ if (rc) {
+ /*
+ * The firmware in the rootfs will not be accessible until we
+ * are in the SYSTEM_RUNNING state, so return EPROBE_DEFER until
+ * that point.
+ */
+ if (system_state < SYSTEM_RUNNING)
+ return -EPROBE_DEFER;
+ goto fw_err;
+ }
+
+ data_size = fw->size;
+ /*
+ * This uses the GFP_DMA flag to ensure we are allocated memory in the
+ * 32-bit space since TF-A cannot map memory beyond the 32-bit boundary.
+ */
+ data_buf = kmalloc(fw->size, GFP_KERNEL | GFP_DMA);
+ if (!data_buf) {
+ rc = -ENOMEM;
+ goto fw_err;
+ }
+ memcpy(data_buf, fw->data, fw->size);
+ data_pa = virt_to_phys(data_buf);
+ reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa);
+ reg_pair_from_64(&data_size_high, &data_size_low, data_size);
+ goto fw_load;
+
+fw_err:
+ pr_warn("image loading failed\n");
+ data_pa_high = 0;
+ data_pa_low = 0;
+ data_size_high = 0;
+ data_size_low = 0;
+
+fw_load:
+ /*
+ * Always invoke the SMC, even if loading the image fails, to indicate
+ * to EL3 that we have passed the point where it should allow invoking
+ * this SMC.
+ */
+ pr_warn("OP-TEE image loaded from kernel, this can be insecure");
+ invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
+ data_pa_high, data_pa_low, 0, 0, 0, &res);
+ if (!rc)
+ rc = res.a0;
+ if (fw)
+ release_firmware(fw);
+ kfree(data_buf);
+
+ if (!rc) {
+ /*
+ * We need to initialize OP-TEE on all other running cores as
+ * well. Any cores that aren't running yet will get initialized
+ * when they are brought up by the power management functions in
+ * TF-A which are registered by the OP-TEE SPD. Due to that we
+ * can un-register the callback right after registering it.
+ */
+ cpuhp_invoke_fn = invoke_fn;
+ hp_state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "optee:probe",
+ optee_cpuhp_probe, NULL);
+ if (hp_state < 0) {
+ pr_warn("Failed with CPU hotplug setup for OP-TEE");
+ return -EINVAL;
+ }
+ cpuhp_remove_state(hp_state);
+ cpuhp_invoke_fn = NULL;
+ }
+
+ return rc;
+}
+#else
+static inline int optee_load_fw(struct platform_device *pdev,
+ optee_invoke_fn *invoke_fn)
+{
+ return 0;
+}
+#endif
+
static int optee_probe(struct platform_device *pdev)
{
optee_invoke_fn *invoke_fn;
@@ -1372,6 +1505,10 @@ static int optee_probe(struct platform_device *pdev)
if (IS_ERR(invoke_fn))
return PTR_ERR(invoke_fn);
+ rc = optee_load_fw(pdev, invoke_fn);
+ if (rc)
+ return rc;
+
if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
pr_warn("api uid mismatch\n");
return -EINVAL;
--
2.40.0.348.gf938b09366-goog
The corresponding TF-A change is merged now, so the kernel patch
should be all ready to go.
On Fri, Mar 31, 2023 at 11:35 AM Jeffrey Kardatzke
<[email protected]> wrote:
>
> Adds an SMC call that will pass an OP-TEE binary image to EL3 and
> instruct it to load it as the BL32 payload. This works in conjunction
> with a feature added to Trusted Firmware for ARMv8 and above
> architectures that supports this.
>
> The main purpose of this change is to facilitate updating the OP-TEE
> component on devices via a rootfs change rather than having to do a
> firmware update. Further details are linked to in the Kconfig file.
>
> Signed-off-by: Jeffrey Kardatzke <[email protected]>
> Reviewed-by: Sumit Garg <[email protected]>
> Signed-off-by: Jeffrey Kardatzke <[email protected]>
> ---
>
> Changes in v13:
> - Documentation formatting changes
>
> Changes in v12:
> - Fixed checkpatch strict issues
>
> Changes in v11:
> - Fixed typo in tee.rst documentation
>
> Changes in v10:
> - Fixed tee.rst documentation formatting
>
> Changes in v9:
> - Add CPU hotplug callback to init on all cores at startup
>
> Changes in v8:
> - Renamed params and fixed alignment issue
>
> Changes in v7:
> - Added documentation to Documentation/staging/tee.rst
>
> Changes in v6:
> - Expanded Kconfig documentation
>
> Changes in v5:
> - Renamed config option
> - Added runtime warning when config is used
>
> Changes in v4:
> - Update commit message
> - Added more documentation
> - Renamed config option, added ARM64 dependency
>
> Changes in v3:
> - Removed state tracking for driver reload
> - Check UID of service to verify it needs image load
>
> Changes in v2:
> - Fixed compile issue when feature is disabled
> - Addressed minor comments
> - Added state tracking for driver reload
>
> Documentation/staging/tee.rst | 53 +++++++++++++
> drivers/tee/optee/Kconfig | 17 +++++
> drivers/tee/optee/optee_msg.h | 12 +++
> drivers/tee/optee/optee_smc.h | 24 ++++++
> drivers/tee/optee/smc_abi.c | 137 ++++++++++++++++++++++++++++++++++
> 5 files changed, 243 insertions(+)
>
> diff --git a/Documentation/staging/tee.rst b/Documentation/staging/tee.rst
> index 498343c7ab08..22baa077a3b9 100644
> --- a/Documentation/staging/tee.rst
> +++ b/Documentation/staging/tee.rst
> @@ -214,6 +214,57 @@ call is done from the thread assisting the interrupt handler. This is a
> building block for OP-TEE OS in secure world to implement the top half and
> bottom half style of device drivers.
>
> +OPTEE_INSECURE_LOAD_IMAGE Kconfig option
> +----------------------------------------
> +
> +The OPTEE_INSECURE_LOAD_IMAGE Kconfig option enables the ability to load the
> +BL32 OP-TEE image from the kernel after the kernel boots, rather than loading
> +it from the firmware before the kernel boots. This also requires enabling the
> +corresponding option in Trusted Firmware for Arm. The Trusted Firmware for Arm
> +documentation [8] explains the security threat associated with enabling this as
> +well as mitigations at the firmware and platform level.
> +
> +There are additional attack vectors/mitigations for the kernel that should be
> +addressed when using this option.
> +
> +1. Boot chain security.
> +
> + * Attack vector: Replace the OP-TEE OS image in the rootfs to gain control of
> + the system.
> +
> + * Mitigation: There must be boot chain security that verifies the kernel and
> + rootfs, otherwise an attacker can modify the loaded OP-TEE binary by
> + modifying it in the rootfs.
> +
> +2. Alternate boot modes.
> +
> + * Attack vector: Using an alternate boot mode (i.e. recovery mode), the
> + OP-TEE driver isn't loaded, leaving the SMC hole open.
> +
> + * Mitigation: If there are alternate methods of booting the device, such as a
> + recovery mode, it should be ensured that the same mitigations are applied
> + in that mode.
> +
> +3. Attacks prior to SMC invocation.
> +
> + * Attack vector: Code that is executed prior to issuing the SMC call to load
> + OP-TEE can be exploited to then load an alternate OS image.
> +
> + * Mitigation: The OP-TEE driver must be loaded before any potential attack
> + vectors are opened up. This should include mounting of any modifiable
> + filesystems, opening of network ports or communicating with external
> + devices (e.g. USB).
> +
> +4. Blocking SMC call to load OP-TEE.
> +
> + * Attack vector: Prevent the driver from being probed, so the SMC call to
> + load OP-TEE isn't executed when desired, leaving it open to being executed
> + later and loading a modified OS.
> +
> + * Mitigation: It is recommended to build the OP-TEE driver as builtin driver
> + rather than as a module to prevent exploits that may cause the module to
> + not be loaded.
> +
> AMD-TEE driver
> ==============
>
> @@ -309,3 +360,5 @@ References
> [6] include/linux/psp-tee.h
>
> [7] drivers/tee/amdtee/amdtee_if.h
> +
> +[8] https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
> index f121c224e682..70898bbd5809 100644
> --- a/drivers/tee/optee/Kconfig
> +++ b/drivers/tee/optee/Kconfig
> @@ -7,3 +7,20 @@ config OPTEE
> help
> This implements the OP-TEE Trusted Execution Environment (TEE)
> driver.
> +
> +config OPTEE_INSECURE_LOAD_IMAGE
> + bool "Load OP-TEE image as firmware"
> + default n
> + depends on OPTEE && ARM64
> + help
> + This loads the BL32 image for OP-TEE as firmware when the driver is
> + probed. This returns -EPROBE_DEFER until the firmware is loadable from
> + the filesystem which is determined by checking the system_state until
> + it is in SYSTEM_RUNNING. This also requires enabling the corresponding
> + option in Trusted Firmware for Arm. The documentation there explains
> + the security threat associated with enabling this as well as
> + mitigations at the firmware and platform level.
> + https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> +
> + Additional documentation on kernel security risks are at
> + Documentation/staging/tee.rst.
> diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> index 70e9cc2ee96b..e8840a82b983 100644
> --- a/drivers/tee/optee/optee_msg.h
> +++ b/drivers/tee/optee/optee_msg.h
> @@ -241,11 +241,23 @@ struct optee_msg_arg {
> * 384fb3e0-e7f8-11e3-af63-0002a5d5c51b.
> * Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1,
> * OPTEE_MSG_UID_2, OPTEE_MSG_UID_3.
> + *
> + * In the case where the OP-TEE image is loaded by the kernel, this will
> + * initially return an alternate UID to reflect that we are communicating with
> + * the TF-A image loading service at that time instead of OP-TEE. That UID is:
> + * a3fbeab1-1246-315d-c7c4-06b9c03cbea4.
> + * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0,
> + * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2,
> + * OPTEE_MSG_IMAGE_LOAD_UID_3.
> */
> #define OPTEE_MSG_UID_0 0x384fb3e0
> #define OPTEE_MSG_UID_1 0xe7f811e3
> #define OPTEE_MSG_UID_2 0xaf630002
> #define OPTEE_MSG_UID_3 0xa5d5c51b
> +#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1
> +#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d
> +#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9
> +#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4
> #define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01
>
> /*
> diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> index 73b5e7760d10..7d9fa426505b 100644
> --- a/drivers/tee/optee/optee_smc.h
> +++ b/drivers/tee/optee/optee_smc.h
> @@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result {
> unsigned long reserved1;
> };
>
> +/*
> + * Load Trusted OS from optee/tee.bin in the Linux firmware.
> + *
> + * WARNING: Use this cautiously as it could lead to insecure loading of the
> + * Trusted OS.
> + * This SMC instructs EL3 to load a binary and execute it as the Trusted OS.
> + *
> + * Call register usage:
> + * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE
> + * a1 Upper 32bit of a 64bit size for the payload
> + * a2 Lower 32bit of a 64bit size for the payload
> + * a3 Upper 32bit of the physical address for the payload
> + * a4 Lower 32bit of the physical address for the payload
> + *
> + * The payload is in the OP-TEE image format.
> + *
> + * Returns result in a0, 0 on success and an error code otherwise.
> + */
> +#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2
> +#define OPTEE_SMC_CALL_LOAD_IMAGE \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_TRUSTED_OS_END, \
> + OPTEE_SMC_FUNCID_LOAD_IMAGE)
> +
> /*
> * Call with struct optee_msg_arg as argument
> *
> diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> index a1c1fa1a9c28..6e1f023d50c6 100644
> --- a/drivers/tee/optee/smc_abi.c
> +++ b/drivers/tee/optee/smc_abi.c
> @@ -7,10 +7,13 @@
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> #include <linux/arm-smccc.h>
> +#include <linux/cpuhotplug.h>
> #include <linux/errno.h>
> +#include <linux/firmware.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> #include <linux/irqdomain.h>
> +#include <linux/kernel.h>
> #include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -1149,6 +1152,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
> return false;
> }
>
> +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> +static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invoke_fn)
> +{
> + struct arm_smccc_res res;
> +
> + invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res);
> +
> + if (res.a0 == OPTEE_MSG_IMAGE_LOAD_UID_0 &&
> + res.a1 == OPTEE_MSG_IMAGE_LOAD_UID_1 &&
> + res.a2 == OPTEE_MSG_IMAGE_LOAD_UID_2 &&
> + res.a3 == OPTEE_MSG_IMAGE_LOAD_UID_3)
> + return true;
> + return false;
> +}
> +#endif
> +
> static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn)
> {
> union {
> @@ -1354,6 +1373,120 @@ static void optee_shutdown(struct platform_device *pdev)
> optee_disable_shm_cache(optee);
> }
>
> +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> +
> +#define OPTEE_FW_IMAGE "optee/tee.bin"
> +
> +static optee_invoke_fn *cpuhp_invoke_fn;
> +
> +static int optee_cpuhp_probe(unsigned int cpu)
> +{
> + /*
> + * Invoking a call on a CPU will cause OP-TEE to perform the required
> + * setup for that CPU. Just invoke the call to get the UID since that
> + * has no side effects.
> + */
> + if (optee_msg_api_uid_is_optee_api(cpuhp_invoke_fn))
> + return 0;
> + else
> + return -EINVAL;
> +}
> +
> +static int optee_load_fw(struct platform_device *pdev,
> + optee_invoke_fn *invoke_fn)
> +{
> + const struct firmware *fw = NULL;
> + struct arm_smccc_res res;
> + phys_addr_t data_pa;
> + u8 *data_buf = NULL;
> + u64 data_size;
> + u32 data_pa_high, data_pa_low;
> + u32 data_size_high, data_size_low;
> + int rc;
> + int hp_state;
> +
> + if (!optee_msg_api_uid_is_optee_image_load(invoke_fn))
> + return 0;
> +
> + rc = request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev);
> + if (rc) {
> + /*
> + * The firmware in the rootfs will not be accessible until we
> + * are in the SYSTEM_RUNNING state, so return EPROBE_DEFER until
> + * that point.
> + */
> + if (system_state < SYSTEM_RUNNING)
> + return -EPROBE_DEFER;
> + goto fw_err;
> + }
> +
> + data_size = fw->size;
> + /*
> + * This uses the GFP_DMA flag to ensure we are allocated memory in the
> + * 32-bit space since TF-A cannot map memory beyond the 32-bit boundary.
> + */
> + data_buf = kmalloc(fw->size, GFP_KERNEL | GFP_DMA);
> + if (!data_buf) {
> + rc = -ENOMEM;
> + goto fw_err;
> + }
> + memcpy(data_buf, fw->data, fw->size);
> + data_pa = virt_to_phys(data_buf);
> + reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa);
> + reg_pair_from_64(&data_size_high, &data_size_low, data_size);
> + goto fw_load;
> +
> +fw_err:
> + pr_warn("image loading failed\n");
> + data_pa_high = 0;
> + data_pa_low = 0;
> + data_size_high = 0;
> + data_size_low = 0;
> +
> +fw_load:
> + /*
> + * Always invoke the SMC, even if loading the image fails, to indicate
> + * to EL3 that we have passed the point where it should allow invoking
> + * this SMC.
> + */
> + pr_warn("OP-TEE image loaded from kernel, this can be insecure");
> + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
> + data_pa_high, data_pa_low, 0, 0, 0, &res);
> + if (!rc)
> + rc = res.a0;
> + if (fw)
> + release_firmware(fw);
> + kfree(data_buf);
> +
> + if (!rc) {
> + /*
> + * We need to initialize OP-TEE on all other running cores as
> + * well. Any cores that aren't running yet will get initialized
> + * when they are brought up by the power management functions in
> + * TF-A which are registered by the OP-TEE SPD. Due to that we
> + * can un-register the callback right after registering it.
> + */
> + cpuhp_invoke_fn = invoke_fn;
> + hp_state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "optee:probe",
> + optee_cpuhp_probe, NULL);
> + if (hp_state < 0) {
> + pr_warn("Failed with CPU hotplug setup for OP-TEE");
> + return -EINVAL;
> + }
> + cpuhp_remove_state(hp_state);
> + cpuhp_invoke_fn = NULL;
> + }
> +
> + return rc;
> +}
> +#else
> +static inline int optee_load_fw(struct platform_device *pdev,
> + optee_invoke_fn *invoke_fn)
> +{
> + return 0;
> +}
> +#endif
> +
> static int optee_probe(struct platform_device *pdev)
> {
> optee_invoke_fn *invoke_fn;
> @@ -1372,6 +1505,10 @@ static int optee_probe(struct platform_device *pdev)
> if (IS_ERR(invoke_fn))
> return PTR_ERR(invoke_fn);
>
> + rc = optee_load_fw(pdev, invoke_fn);
> + if (rc)
> + return rc;
> +
> if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
> pr_warn("api uid mismatch\n");
> return -EINVAL;
> --
> 2.40.0.348.gf938b09366-goog
>
On Mon, Apr 3, 2023 at 6:57 PM Jeffrey Kardatzke <[email protected]> wrote:
>
> The corresponding TF-A change is merged now, so the kernel patch
> should be all ready to go.
>
> On Fri, Mar 31, 2023 at 11:35 AM Jeffrey Kardatzke
> <[email protected]> wrote:
> >
> > Adds an SMC call that will pass an OP-TEE binary image to EL3 and
> > instruct it to load it as the BL32 payload. This works in conjunction
> > with a feature added to Trusted Firmware for ARMv8 and above
> > architectures that supports this.
> >
> > The main purpose of this change is to facilitate updating the OP-TEE
> > component on devices via a rootfs change rather than having to do a
> > firmware update. Further details are linked to in the Kconfig file.
> >
> > Signed-off-by: Jeffrey Kardatzke <[email protected]>
> > Reviewed-by: Sumit Garg <[email protected]>
> > Signed-off-by: Jeffrey Kardatzke <[email protected]>
I'm picking up this.
Thanks,
Jens
> > ---
> >
> > Changes in v13:
> > - Documentation formatting changes
> >
> > Changes in v12:
> > - Fixed checkpatch strict issues
> >
> > Changes in v11:
> > - Fixed typo in tee.rst documentation
> >
> > Changes in v10:
> > - Fixed tee.rst documentation formatting
> >
> > Changes in v9:
> > - Add CPU hotplug callback to init on all cores at startup
> >
> > Changes in v8:
> > - Renamed params and fixed alignment issue
> >
> > Changes in v7:
> > - Added documentation to Documentation/staging/tee.rst
> >
> > Changes in v6:
> > - Expanded Kconfig documentation
> >
> > Changes in v5:
> > - Renamed config option
> > - Added runtime warning when config is used
> >
> > Changes in v4:
> > - Update commit message
> > - Added more documentation
> > - Renamed config option, added ARM64 dependency
> >
> > Changes in v3:
> > - Removed state tracking for driver reload
> > - Check UID of service to verify it needs image load
> >
> > Changes in v2:
> > - Fixed compile issue when feature is disabled
> > - Addressed minor comments
> > - Added state tracking for driver reload
> >
> > Documentation/staging/tee.rst | 53 +++++++++++++
> > drivers/tee/optee/Kconfig | 17 +++++
> > drivers/tee/optee/optee_msg.h | 12 +++
> > drivers/tee/optee/optee_smc.h | 24 ++++++
> > drivers/tee/optee/smc_abi.c | 137 ++++++++++++++++++++++++++++++++++
> > 5 files changed, 243 insertions(+)
> >
> > diff --git a/Documentation/staging/tee.rst b/Documentation/staging/tee.rst
> > index 498343c7ab08..22baa077a3b9 100644
> > --- a/Documentation/staging/tee.rst
> > +++ b/Documentation/staging/tee.rst
> > @@ -214,6 +214,57 @@ call is done from the thread assisting the interrupt handler. This is a
> > building block for OP-TEE OS in secure world to implement the top half and
> > bottom half style of device drivers.
> >
> > +OPTEE_INSECURE_LOAD_IMAGE Kconfig option
> > +----------------------------------------
> > +
> > +The OPTEE_INSECURE_LOAD_IMAGE Kconfig option enables the ability to load the
> > +BL32 OP-TEE image from the kernel after the kernel boots, rather than loading
> > +it from the firmware before the kernel boots. This also requires enabling the
> > +corresponding option in Trusted Firmware for Arm. The Trusted Firmware for Arm
> > +documentation [8] explains the security threat associated with enabling this as
> > +well as mitigations at the firmware and platform level.
> > +
> > +There are additional attack vectors/mitigations for the kernel that should be
> > +addressed when using this option.
> > +
> > +1. Boot chain security.
> > +
> > + * Attack vector: Replace the OP-TEE OS image in the rootfs to gain control of
> > + the system.
> > +
> > + * Mitigation: There must be boot chain security that verifies the kernel and
> > + rootfs, otherwise an attacker can modify the loaded OP-TEE binary by
> > + modifying it in the rootfs.
> > +
> > +2. Alternate boot modes.
> > +
> > + * Attack vector: Using an alternate boot mode (i.e. recovery mode), the
> > + OP-TEE driver isn't loaded, leaving the SMC hole open.
> > +
> > + * Mitigation: If there are alternate methods of booting the device, such as a
> > + recovery mode, it should be ensured that the same mitigations are applied
> > + in that mode.
> > +
> > +3. Attacks prior to SMC invocation.
> > +
> > + * Attack vector: Code that is executed prior to issuing the SMC call to load
> > + OP-TEE can be exploited to then load an alternate OS image.
> > +
> > + * Mitigation: The OP-TEE driver must be loaded before any potential attack
> > + vectors are opened up. This should include mounting of any modifiable
> > + filesystems, opening of network ports or communicating with external
> > + devices (e.g. USB).
> > +
> > +4. Blocking SMC call to load OP-TEE.
> > +
> > + * Attack vector: Prevent the driver from being probed, so the SMC call to
> > + load OP-TEE isn't executed when desired, leaving it open to being executed
> > + later and loading a modified OS.
> > +
> > + * Mitigation: It is recommended to build the OP-TEE driver as builtin driver
> > + rather than as a module to prevent exploits that may cause the module to
> > + not be loaded.
> > +
> > AMD-TEE driver
> > ==============
> >
> > @@ -309,3 +360,5 @@ References
> > [6] include/linux/psp-tee.h
> >
> > [7] drivers/tee/amdtee/amdtee_if.h
> > +
> > +[8] https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> > diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
> > index f121c224e682..70898bbd5809 100644
> > --- a/drivers/tee/optee/Kconfig
> > +++ b/drivers/tee/optee/Kconfig
> > @@ -7,3 +7,20 @@ config OPTEE
> > help
> > This implements the OP-TEE Trusted Execution Environment (TEE)
> > driver.
> > +
> > +config OPTEE_INSECURE_LOAD_IMAGE
> > + bool "Load OP-TEE image as firmware"
> > + default n
> > + depends on OPTEE && ARM64
> > + help
> > + This loads the BL32 image for OP-TEE as firmware when the driver is
> > + probed. This returns -EPROBE_DEFER until the firmware is loadable from
> > + the filesystem which is determined by checking the system_state until
> > + it is in SYSTEM_RUNNING. This also requires enabling the corresponding
> > + option in Trusted Firmware for Arm. The documentation there explains
> > + the security threat associated with enabling this as well as
> > + mitigations at the firmware and platform level.
> > + https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> > +
> > + Additional documentation on kernel security risks are at
> > + Documentation/staging/tee.rst.
> > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> > index 70e9cc2ee96b..e8840a82b983 100644
> > --- a/drivers/tee/optee/optee_msg.h
> > +++ b/drivers/tee/optee/optee_msg.h
> > @@ -241,11 +241,23 @@ struct optee_msg_arg {
> > * 384fb3e0-e7f8-11e3-af63-0002a5d5c51b.
> > * Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1,
> > * OPTEE_MSG_UID_2, OPTEE_MSG_UID_3.
> > + *
> > + * In the case where the OP-TEE image is loaded by the kernel, this will
> > + * initially return an alternate UID to reflect that we are communicating with
> > + * the TF-A image loading service at that time instead of OP-TEE. That UID is:
> > + * a3fbeab1-1246-315d-c7c4-06b9c03cbea4.
> > + * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0,
> > + * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2,
> > + * OPTEE_MSG_IMAGE_LOAD_UID_3.
> > */
> > #define OPTEE_MSG_UID_0 0x384fb3e0
> > #define OPTEE_MSG_UID_1 0xe7f811e3
> > #define OPTEE_MSG_UID_2 0xaf630002
> > #define OPTEE_MSG_UID_3 0xa5d5c51b
> > +#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1
> > +#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d
> > +#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9
> > +#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4
> > #define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01
> >
> > /*
> > diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> > index 73b5e7760d10..7d9fa426505b 100644
> > --- a/drivers/tee/optee/optee_smc.h
> > +++ b/drivers/tee/optee/optee_smc.h
> > @@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result {
> > unsigned long reserved1;
> > };
> >
> > +/*
> > + * Load Trusted OS from optee/tee.bin in the Linux firmware.
> > + *
> > + * WARNING: Use this cautiously as it could lead to insecure loading of the
> > + * Trusted OS.
> > + * This SMC instructs EL3 to load a binary and execute it as the Trusted OS.
> > + *
> > + * Call register usage:
> > + * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE
> > + * a1 Upper 32bit of a 64bit size for the payload
> > + * a2 Lower 32bit of a 64bit size for the payload
> > + * a3 Upper 32bit of the physical address for the payload
> > + * a4 Lower 32bit of the physical address for the payload
> > + *
> > + * The payload is in the OP-TEE image format.
> > + *
> > + * Returns result in a0, 0 on success and an error code otherwise.
> > + */
> > +#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2
> > +#define OPTEE_SMC_CALL_LOAD_IMAGE \
> > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
> > + ARM_SMCCC_OWNER_TRUSTED_OS_END, \
> > + OPTEE_SMC_FUNCID_LOAD_IMAGE)
> > +
> > /*
> > * Call with struct optee_msg_arg as argument
> > *
> > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> > index a1c1fa1a9c28..6e1f023d50c6 100644
> > --- a/drivers/tee/optee/smc_abi.c
> > +++ b/drivers/tee/optee/smc_abi.c
> > @@ -7,10 +7,13 @@
> > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >
> > #include <linux/arm-smccc.h>
> > +#include <linux/cpuhotplug.h>
> > #include <linux/errno.h>
> > +#include <linux/firmware.h>
> > #include <linux/interrupt.h>
> > #include <linux/io.h>
> > #include <linux/irqdomain.h>
> > +#include <linux/kernel.h>
> > #include <linux/mm.h>
> > #include <linux/module.h>
> > #include <linux/of.h>
> > @@ -1149,6 +1152,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
> > return false;
> > }
> >
> > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > +static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invoke_fn)
> > +{
> > + struct arm_smccc_res res;
> > +
> > + invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res);
> > +
> > + if (res.a0 == OPTEE_MSG_IMAGE_LOAD_UID_0 &&
> > + res.a1 == OPTEE_MSG_IMAGE_LOAD_UID_1 &&
> > + res.a2 == OPTEE_MSG_IMAGE_LOAD_UID_2 &&
> > + res.a3 == OPTEE_MSG_IMAGE_LOAD_UID_3)
> > + return true;
> > + return false;
> > +}
> > +#endif
> > +
> > static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn)
> > {
> > union {
> > @@ -1354,6 +1373,120 @@ static void optee_shutdown(struct platform_device *pdev)
> > optee_disable_shm_cache(optee);
> > }
> >
> > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > +
> > +#define OPTEE_FW_IMAGE "optee/tee.bin"
> > +
> > +static optee_invoke_fn *cpuhp_invoke_fn;
> > +
> > +static int optee_cpuhp_probe(unsigned int cpu)
> > +{
> > + /*
> > + * Invoking a call on a CPU will cause OP-TEE to perform the required
> > + * setup for that CPU. Just invoke the call to get the UID since that
> > + * has no side effects.
> > + */
> > + if (optee_msg_api_uid_is_optee_api(cpuhp_invoke_fn))
> > + return 0;
> > + else
> > + return -EINVAL;
> > +}
> > +
> > +static int optee_load_fw(struct platform_device *pdev,
> > + optee_invoke_fn *invoke_fn)
> > +{
> > + const struct firmware *fw = NULL;
> > + struct arm_smccc_res res;
> > + phys_addr_t data_pa;
> > + u8 *data_buf = NULL;
> > + u64 data_size;
> > + u32 data_pa_high, data_pa_low;
> > + u32 data_size_high, data_size_low;
> > + int rc;
> > + int hp_state;
> > +
> > + if (!optee_msg_api_uid_is_optee_image_load(invoke_fn))
> > + return 0;
> > +
> > + rc = request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev);
> > + if (rc) {
> > + /*
> > + * The firmware in the rootfs will not be accessible until we
> > + * are in the SYSTEM_RUNNING state, so return EPROBE_DEFER until
> > + * that point.
> > + */
> > + if (system_state < SYSTEM_RUNNING)
> > + return -EPROBE_DEFER;
> > + goto fw_err;
> > + }
> > +
> > + data_size = fw->size;
> > + /*
> > + * This uses the GFP_DMA flag to ensure we are allocated memory in the
> > + * 32-bit space since TF-A cannot map memory beyond the 32-bit boundary.
> > + */
> > + data_buf = kmalloc(fw->size, GFP_KERNEL | GFP_DMA);
> > + if (!data_buf) {
> > + rc = -ENOMEM;
> > + goto fw_err;
> > + }
> > + memcpy(data_buf, fw->data, fw->size);
> > + data_pa = virt_to_phys(data_buf);
> > + reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa);
> > + reg_pair_from_64(&data_size_high, &data_size_low, data_size);
> > + goto fw_load;
> > +
> > +fw_err:
> > + pr_warn("image loading failed\n");
> > + data_pa_high = 0;
> > + data_pa_low = 0;
> > + data_size_high = 0;
> > + data_size_low = 0;
> > +
> > +fw_load:
> > + /*
> > + * Always invoke the SMC, even if loading the image fails, to indicate
> > + * to EL3 that we have passed the point where it should allow invoking
> > + * this SMC.
> > + */
> > + pr_warn("OP-TEE image loaded from kernel, this can be insecure");
> > + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
> > + data_pa_high, data_pa_low, 0, 0, 0, &res);
> > + if (!rc)
> > + rc = res.a0;
> > + if (fw)
> > + release_firmware(fw);
> > + kfree(data_buf);
> > +
> > + if (!rc) {
> > + /*
> > + * We need to initialize OP-TEE on all other running cores as
> > + * well. Any cores that aren't running yet will get initialized
> > + * when they are brought up by the power management functions in
> > + * TF-A which are registered by the OP-TEE SPD. Due to that we
> > + * can un-register the callback right after registering it.
> > + */
> > + cpuhp_invoke_fn = invoke_fn;
> > + hp_state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "optee:probe",
> > + optee_cpuhp_probe, NULL);
> > + if (hp_state < 0) {
> > + pr_warn("Failed with CPU hotplug setup for OP-TEE");
> > + return -EINVAL;
> > + }
> > + cpuhp_remove_state(hp_state);
> > + cpuhp_invoke_fn = NULL;
> > + }
> > +
> > + return rc;
> > +}
> > +#else
> > +static inline int optee_load_fw(struct platform_device *pdev,
> > + optee_invoke_fn *invoke_fn)
> > +{
> > + return 0;
> > +}
> > +#endif
> > +
> > static int optee_probe(struct platform_device *pdev)
> > {
> > optee_invoke_fn *invoke_fn;
> > @@ -1372,6 +1505,10 @@ static int optee_probe(struct platform_device *pdev)
> > if (IS_ERR(invoke_fn))
> > return PTR_ERR(invoke_fn);
> >
> > + rc = optee_load_fw(pdev, invoke_fn);
> > + if (rc)
> > + return rc;
> > +
> > if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
> > pr_warn("api uid mismatch\n");
> > return -EINVAL;
> > --
> > 2.40.0.348.gf938b09366-goog
> >