Re: [PATCH v3 1/2] tee: system invocation

From: Sumit Garg
Date: Wed Feb 22 2023 - 04:00:49 EST

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On Wed, 15 Feb 2023 at 16:34, Etienne Carriere
<etienne.carriere@xxxxxxxxxx> wrote:
>
> 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>
> ---
> 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_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
> +

Just for the record, this is being parallely discussed here [1]. So we
need to handle all the OP-TEE SMC call cases as per Jens suggestion
here [1].

[1] https://github.com/OP-TEE/optee_os/pull/5789#discussion_r1106922714

-Sumit

> +/*
> + * 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
>

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