[PATCH v2 1/2] tee: system invocation

From: Etienne Carriere
Date: Tue Feb 14 2023 - 10:30:17 EST

Adds TEE system invocation context provisioning for a Linux driver
to provision execution contexts for invocation of system service
hosted in TEE. OP-TEE SMC ABI implements such invocation context
provisioning.

This feature is needed when a TEE invocation cannot afford to wait for
a free TEE thread when all TEE threads context are used and suspended
as these may be suspended waiting for a system service, as an SCMI clock
or voltage regulator, to be enabled. An example is when OP-TEE invokes
a Linux OS remote service (RPC) to access an eMMC RPMB partition and
the eMMC device is supplied by an OP-TEE SCMI regulator.

Signed-off-by: Etienne Carriere <etienne.carriere@xxxxxxxxxx>
---
Change since v1
- Addressed comment on Linux client to claim reservation on TEE context.
This brings 2 new operations from client to TEE to request and release
system thread contexts: 2 new tee_drv.h API functions, 2 new ops
functions in struct tee_driver_ops. The OP-TEE implement shall implement
2 new fastcall SMC funcIDs.
- Fixed typos in commit message.
---
drivers/tee/optee/optee_smc.h | 60 +++++++++++++++++++++++++++++++++--
drivers/tee/optee/smc_abi.c | 34 +++++++++++++++++++-
drivers/tee/tee_core.c | 30 ++++++++++++++++++
include/linux/tee_drv.h | 21 ++++++++++++
4 files changed, 141 insertions(+), 4 deletions(-)

diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
index 73b5e7760d10..75b19e1bd185 100644
--- a/drivers/tee/optee/optee_smc.h
+++ b/drivers/tee/optee/optee_smc.h
@@ -108,7 +108,8 @@ struct optee_smc_call_get_os_revision_result {
* Call with struct optee_msg_arg as argument
*
* When called with OPTEE_SMC_CALL_WITH_RPC_ARG or
- * OPTEE_SMC_CALL_WITH_REGD_ARG in a0 there is one RPC struct optee_msg_arg
+ * OPTEE_SMC_CALL_WITH_REGD_ARG or OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG
+ * in a0 there is one RPC struct optee_msg_arg
* following after the first struct optee_msg_arg. The RPC struct
* optee_msg_arg has reserved space for the number of RPC parameters as
* returned by OPTEE_SMC_EXCHANGE_CAPABILITIES.
@@ -130,8 +131,8 @@ struct optee_smc_call_get_os_revision_result {
* a4-6 Not used
* a7 Hypervisor Client ID register
*
- * Call register usage, OPTEE_SMC_CALL_WITH_REGD_ARG:
- * a0 SMC Function ID, OPTEE_SMC_CALL_WITH_REGD_ARG
+ * Call register usage, OPTEE_SMC_CALL_WITH_REGD_ARG and OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG:
+ * a0 SMC Function ID, OPTEE_SMC_CALL_WITH_REGD_ARG or OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG
* a1 Upper 32 bits of a 64-bit shared memory cookie
* a2 Lower 32 bits of a 64-bit shared memory cookie
* a3 Offset of the struct optee_msg_arg in the shared memory with the
@@ -175,6 +176,8 @@ struct optee_smc_call_get_os_revision_result {
OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_RPC_ARG)
#define OPTEE_SMC_CALL_WITH_REGD_ARG \
OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG)
+#define OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG \
+ OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG)

/*
* Get Shared Memory Config
@@ -254,6 +257,8 @@ struct optee_smc_get_shm_config_result {
#define OPTEE_SMC_SEC_CAP_ASYNC_NOTIF BIT(5)
/* Secure world supports pre-allocating RPC arg struct */
#define OPTEE_SMC_SEC_CAP_RPC_ARG BIT(6)
+/* Secure world provisions thread for system service invocation */
+#define OPTEE_SMC_SEC_CAP_SYSTEM_THREAD BIT(7)

#define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES 9
#define OPTEE_SMC_EXCHANGE_CAPABILITIES \
@@ -426,6 +431,55 @@ struct optee_smc_disable_shm_cache_result {
/* See OPTEE_SMC_CALL_WITH_REGD_ARG above */
#define OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG 19

+/* See OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG above */
+#define OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG 20
+
+/*
+ * Request reservation of a system invocation thread context in OP-TEE
+ *
+ * Call register usage:
+ * a0 SMC Function ID: OPTEE_SMC_CALL_RESERVE_SYS_THREAD
+ * a1-6 Not used
+ * a7 Hypervisor Client ID register
+ *
+ * Normal return register usage:
+ * a0 Return value, OPTEE_SMC_RETURN_*
+ * a1-3 Not used
+ * a4-7 Preserved
+ *
+ * Possible return values:
+ * OPTEE_SMC_RETURN_UNKNOWN_FUNCTION Trusted OS does not recognize this
+ * function.
+ * OPTEE_SMC_RETURN_OK Call successfully completed.
+ * OPTEE_SMC_RETURN_ETHREAD_LIMIT Number of Trusted OS threads exceeded
+ * for the request.
+ */
+#define OPTEE_SMC_FUNCID_CALL_RESERVE_SYS_THREAD 21
+#define OPTEE_SMC_CALL_RESERVE_SYS_THREAD \
+ OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_RESERVE_SYS_THREAD)
+
+/*
+ * Unregister reservation of a system invocation thread context in OP-TEE
+ *
+ * Call register usage:
+ * a0 SMC Function ID: OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD
+ * a1-6 Not used
+ * a7 Hypervisor Client ID register
+ *
+ * Normal return register usage:
+ * a0 Return value, OPTEE_SMC_RETURN_*
+ * a1-3 Not used
+ * a4-7 Preserved
+ *
+ * Possible return values:
+ * OPTEE_SMC_RETURN_UNKNOWN_FUNCTION Trusted OS does not recognize this
+ * function.
+ * OPTEE_SMC_RETURN_OK Call successfully completed.
+ */
+#define OPTEE_SMC_FUNCID_CALL_UNRESERVE_SYS_THREAD 22
+#define OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD \
+ OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_UNRESERVE_SYS_THREAD)
+
/*
* Resume from RPC (for example after processing a foreign interrupt)
*
diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
index a1c1fa1a9c28..013b5ae31c0e 100644
--- a/drivers/tee/optee/smc_abi.c
+++ b/drivers/tee/optee/smc_abi.c
@@ -889,7 +889,10 @@ static int optee_smc_do_call_with_arg(struct tee_context *ctx,
}

if (rpc_arg && tee_shm_is_dynamic(shm)) {
- param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG;
+ if (ctx->system_ctx_count)
+ param.a0 = OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG;
+ else
+ param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG;
reg_pair_from_64(&param.a1, &param.a2, (u_long)shm);
param.a3 = offs;
} else {
@@ -1085,6 +1088,33 @@ static int optee_smc_open(struct tee_context *ctx)
return optee_open(ctx, sec_caps & OPTEE_SMC_SEC_CAP_MEMREF_NULL);
}

+static int optee_request_sys_ctx(struct tee_context *ctx)
+{
+ struct optee *optee = tee_get_drvdata(ctx->teedev);
+ struct arm_smccc_res res;
+
+ if (!(optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD))
+ return -EINVAL;
+
+ optee->smc.invoke_fn(OPTEE_SMC_CALL_RESERVE_SYS_THREAD,
+ 0, 0, 0, 0, 0, 0, 0, &res);
+
+ if (res.a0 != OPTEE_SMC_RETURN_OK)
+ return -EINVAL;
+
+ return 0;
+}
+
+static void optee_release_sys_ctx(struct tee_context *ctx)
+{
+ struct optee *optee = tee_get_drvdata(ctx->teedev);
+ struct arm_smccc_res res;
+
+ if (optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD)
+ optee->smc.invoke_fn(OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD,
+ 0, 0, 0, 0, 0, 0, 0, &res);
+}
+
static const struct tee_driver_ops optee_clnt_ops = {
.get_version = optee_get_version,
.open = optee_smc_open,
@@ -1095,6 +1125,8 @@ static const struct tee_driver_ops optee_clnt_ops = {
.cancel_req = optee_cancel_req,
.shm_register = optee_shm_register,
.shm_unregister = optee_shm_unregister,
+ .system_ctx_request = optee_request_sys_ctx,
+ .system_ctx_release = optee_release_sys_ctx,
};

static const struct tee_desc optee_clnt_desc = {
diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 98da206cd761..a7dfdea5d85b 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -5,6 +5,7 @@

#define pr_fmt(fmt) "%s: " fmt, __func__

+#include <linux/bug.h>
#include <linux/cdev.h>
#include <linux/cred.h>
#include <linux/fs.h>
@@ -1141,10 +1142,39 @@ EXPORT_SYMBOL_GPL(tee_client_open_context);

void tee_client_close_context(struct tee_context *ctx)
{
+ while (ctx->system_ctx_count)
+ tee_client_release_system_context(ctx);
+
teedev_close_context(ctx);
}
EXPORT_SYMBOL_GPL(tee_client_close_context);

+int tee_client_request_system_context(struct tee_context *ctx)
+{
+ int ret;
+
+ if (!ctx->teedev->desc->ops->system_ctx_request ||
+ !ctx->teedev->desc->ops->system_ctx_release)
+ return -EINVAL;
+
+ ret = ctx->teedev->desc->ops->system_ctx_request(ctx);
+ if (!ret)
+ ctx->system_ctx_count++;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tee_client_request_system_context);
+
+void tee_client_release_system_context(struct tee_context *ctx)
+{
+ if (ctx->system_ctx_count &&
+ ctx->teedev->desc->ops->system_ctx_release) {
+ ctx->teedev->desc->ops->system_ctx_release(ctx);
+ ctx->system_ctx_count--;
+ }
+}
+EXPORT_SYMBOL_GPL(tee_client_release_system_context);
+
void tee_client_get_version(struct tee_context *ctx,
struct tee_ioctl_version_data *vers)
{
diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
index 17eb1c5205d3..45577256bb71 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h
@@ -47,6 +47,8 @@ struct tee_shm_pool;
* non-blocking in nature.
* @cap_memref_null: flag indicating if the TEE Client support shared
* memory buffer with a NULL pointer.
+ * @system_ctx_count: Number of system invocation contexts provisioned for
+ * this TEE client or 0.
*/
struct tee_context {
struct tee_device *teedev;
@@ -55,6 +57,7 @@ struct tee_context {
bool releasing;
bool supp_nowait;
bool cap_memref_null;
+ unsigned int system_ctx_count;
};

struct tee_param_memref {
@@ -90,6 +93,8 @@ struct tee_param {
* @supp_send: called for supplicant to send a response
* @shm_register: register shared memory buffer in TEE
* @shm_unregister: unregister shared memory buffer in TEE
+ * @system_ctx_request: Request provisioning of a new system context in TEE
+ * @system_ctx_release: Release a provisioned system context in TEE
*/
struct tee_driver_ops {
void (*get_version)(struct tee_device *teedev,
@@ -112,6 +117,8 @@ struct tee_driver_ops {
struct page **pages, size_t num_pages,
unsigned long start);
int (*shm_unregister)(struct tee_context *ctx, struct tee_shm *shm);
+ int (*system_ctx_request)(struct tee_context *ctx);
+ void (*system_ctx_release)(struct tee_context *ctx);
};

/**
@@ -397,6 +404,20 @@ tee_client_open_context(struct tee_context *start,
*/
void tee_client_close_context(struct tee_context *ctx);

+/**
+ * tee_client_request_system_context() - Close a TEE context
+ * @ctx: TEE context to close
+ *
+ * @return 0 on success else an error code
+ */
+int tee_client_request_system_context(struct tee_context *ctx);
+
+/**
+ * tee_client_release_system_context() - Release a reserved system exec context
+ * @ctx: TEE context reference
+ */
+void tee_client_release_system_context(struct tee_context *ctx);
+
/**
* tee_client_get_version() - Query version of TEE
* @ctx: TEE context to TEE to query
--
2.25.1