[PATCH v4 1/2] tee: system invocation

From: Etienne Carriere
Date: Wed Feb 15 2023 - 12:02:53 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>
---
Changes since v3:
- Fixed new SMC funcIDs to reserved/unreserve OP-TEE thread contexts:
minor renaming + define as fastcall funcIDs.
- Moved system_ctx_count from generic struct tee_context to optee's
private struct optee_context_data. This changes optee smc_abi.c
to release reserved thread contexts when the optee device is released.
- Fixed inline description comments.

No change since v2

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_private.h | 9 ++++-
drivers/tee/optee/optee_smc.h | 60 +++++++++++++++++++++++++++--
drivers/tee/optee/smc_abi.c | 64 ++++++++++++++++++++++++++++++-
drivers/tee/tee_core.c | 18 +++++++++
include/linux/tee_drv.h | 18 +++++++++
5 files changed, 163 insertions(+), 6 deletions(-)

diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
index 04ae58892608..b409ed2acfa6 100644
--- a/drivers/tee/optee/optee_private.h
+++ b/drivers/tee/optee/optee_private.h
@@ -182,10 +182,17 @@ struct optee_session {
u32 session_id;
};

+/*
+ * struct optee_context_data - TEE context private data
+ * @mutex Serializes access to this struct
+ * @sess_list List of TEE sessions opened for this context
+ * @system_ctx_count Number of system invocation contexts provisioned in TEE
+ * for this context
+ */
struct optee_context_data {
- /* Serializes access to this struct */
struct mutex mutex;
struct list_head sess_list;
+ size_t system_ctx_count;
};

struct optee_rpc_param {
diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
index 73b5e7760d10..7d08ccaf47d4 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_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_RESERVE_SYS_THREAD 21
+#define OPTEE_SMC_RESERVE_SYS_THREAD \
+ OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_RESERVE_SYS_THREAD)
+
+/*
+ * Unregister reservation of a system invocation thread context in OP-TEE
+ *
+ * Call register usage:
+ * a0 SMC Function ID: OPTEE_SMC_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_UNRESERVE_SYS_THREAD 22
+#define OPTEE_SMC_UNRESERVE_SYS_THREAD \
+ OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_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..8668ab5f1c8b 100644
--- a/drivers/tee/optee/smc_abi.c
+++ b/drivers/tee/optee/smc_abi.c
@@ -867,6 +867,7 @@ static void optee_handle_rpc(struct tee_context *ctx,
static int optee_smc_do_call_with_arg(struct tee_context *ctx,
struct tee_shm *shm, u_int offs)
{
+ struct optee_context_data *ctxdata = ctx->data;
struct optee *optee = tee_get_drvdata(ctx->teedev);
struct optee_call_waiter w;
struct optee_rpc_param param = { };
@@ -889,7 +890,10 @@ 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 (ctxdata->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 {
@@ -1077,6 +1081,50 @@ static void optee_get_version(struct tee_device *teedev,
*vers = v;
}

+static int optee_request_sys_ctx(struct tee_context *ctx)
+{
+ struct optee_context_data *ctxdata = ctx->data;
+ 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_RESERVE_SYS_THREAD,
+ 0, 0, 0, 0, 0, 0, 0, &res);
+
+ if (res.a0 != OPTEE_SMC_RETURN_OK)
+ return -EINVAL;
+
+ mutex_lock(&ctxdata->mutex);
+ ctxdata->system_ctx_count++;
+ mutex_unlock(&ctxdata->mutex);
+
+ return 0;
+}
+
+static void optee_release_sys_ctx(struct tee_context *ctx)
+{
+ struct optee_context_data *ctxdata = ctx->data;
+ struct optee *optee = tee_get_drvdata(ctx->teedev);
+ struct arm_smccc_res res;
+
+ if (!ctxdata->system_ctx_count)
+ return;
+
+ optee->smc.invoke_fn(OPTEE_SMC_UNRESERVE_SYS_THREAD,
+ 0, 0, 0, 0, 0, 0, 0, &res);
+
+ if (res.a0 != OPTEE_SMC_RETURN_OK) {
+ WARN_ONCE(1, "OP-TEE: Couldn't release reserved context\n");
+ return;
+ }
+
+ mutex_lock(&ctxdata->mutex);
+ ctxdata->system_ctx_count--;
+ mutex_unlock(&ctxdata->mutex);
+}
+
static int optee_smc_open(struct tee_context *ctx)
{
struct optee *optee = tee_get_drvdata(ctx->teedev);
@@ -1085,16 +1133,28 @@ static int optee_smc_open(struct tee_context *ctx)
return optee_open(ctx, sec_caps & OPTEE_SMC_SEC_CAP_MEMREF_NULL);
}

+static void optee_smc_release(struct tee_context *ctx)
+{
+ struct optee_context_data *ctxdata = ctx->data;
+
+ while (ctxdata->system_ctx_count)
+ optee_release_sys_ctx(ctx);
+
+ optee_release(ctx);
+}
+
static const struct tee_driver_ops optee_clnt_ops = {
.get_version = optee_get_version,
.open = optee_smc_open,
- .release = optee_release,
+ .release = optee_smc_release,
.open_session = optee_open_session,
.close_session = optee_close_session,
.invoke_func = optee_invoke_func,
.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..d6593c57f32d 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>
@@ -1145,6 +1146,23 @@ void tee_client_close_context(struct tee_context *ctx)
}
EXPORT_SYMBOL_GPL(tee_client_close_context);

+int tee_client_request_system_context(struct tee_context *ctx)
+{
+ if (!ctx->teedev->desc->ops->system_ctx_request ||
+ !ctx->teedev->desc->ops->system_ctx_release)
+ return -EINVAL;
+
+ return ctx->teedev->desc->ops->system_ctx_request(ctx);
+}
+EXPORT_SYMBOL_GPL(tee_client_request_system_context);
+
+void tee_client_release_system_context(struct tee_context *ctx)
+{
+ if (ctx->teedev->desc->ops->system_ctx_release)
+ ctx->teedev->desc->ops->system_ctx_release(ctx);
+}
+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..99d016eb7353 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h
@@ -90,6 +90,8 @@ 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 +114,8 @@ 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 +401,20 @@ tee_client_open_context(struct tee_context *start,
*/
void tee_client_close_context(struct tee_context *ctx);

+/**
+ * tee_client_request_system_context() - Request reservation of a system context
+ * @ctx: TEE context reference
+ *
+ * @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 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