Re: [PATCH v4 02/11] tee: add close_context to TEE driver operation

Sumit Garg
2025-05-14T13:46:10Z

On Mon, Apr 28, 2025 at 11:06:23PM -0700, Amirreza Zarrabi wrote:
> The tee_context can be used to manage TEE user resources, including
> those allocated by the driver for the TEE on behalf of the user.
> The release() callback is invoked only when all resources, such as
> tee_shm, are released and there are no references to the tee_context.
>
> When a user closes the device file, the driver should notify the
> TEE to release any resources it may hold and drop the context
> references. To achieve this, a close_context() callback is
> introduced to initiate resource release in the TEE driver when
> the device file is closed.
>
> Relocate teedev_ctx_get, teedev_ctx_put, tee_device_get, and
> tee_device_get functions to tee_core.h to make them accessible
> outside the TEE subsystem.
>
> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>
> ---
> drivers/tee/tee_core.c | 7 +++++++
> drivers/tee/tee_private.h | 6 ------
> include/linux/tee_core.h | 50 +++++++++++++++++++++++++++++++++++++++++++++--
> 3 files changed, 55 insertions(+), 8 deletions(-)

Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>

-Sumit

>
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 24edce4cdbaa..721522fe5c63 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -79,6 +79,7 @@ void teedev_ctx_get(struct tee_context *ctx)
>
> kref_get(&ctx->refcount);
> }
> +EXPORT_SYMBOL_GPL(teedev_ctx_get);
>
> static void teedev_ctx_release(struct kref *ref)
> {
> @@ -96,11 +97,15 @@ void teedev_ctx_put(struct tee_context *ctx)
>
> kref_put(&ctx->refcount, teedev_ctx_release);
> }
> +EXPORT_SYMBOL_GPL(teedev_ctx_put);
>
> void teedev_close_context(struct tee_context *ctx)
> {
> struct tee_device *teedev = ctx->teedev;
>
> + if (teedev->desc->ops->close_context)
> + teedev->desc->ops->close_context(ctx);
> +
> teedev_ctx_put(ctx);
> tee_device_put(teedev);
> }
> @@ -1037,6 +1042,7 @@ void tee_device_put(struct tee_device *teedev)
> }
> mutex_unlock(&teedev->mutex);
> }
> +EXPORT_SYMBOL_GPL(tee_device_put);
>
> bool tee_device_get(struct tee_device *teedev)
> {
> @@ -1049,6 +1055,7 @@ bool tee_device_get(struct tee_device *teedev)
> mutex_unlock(&teedev->mutex);
> return true;
> }
> +EXPORT_SYMBOL_GPL(tee_device_get);
>
> /**
> * tee_device_unregister() - Removes a TEE device
> diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
> index 9bc50605227c..d3f40a03de36 100644
> --- a/drivers/tee/tee_private.h
> +++ b/drivers/tee/tee_private.h
> @@ -14,12 +14,6 @@
>
> int tee_shm_get_fd(struct tee_shm *shm);
>
> -bool tee_device_get(struct tee_device *teedev);
> -void tee_device_put(struct tee_device *teedev);
> -
> -void teedev_ctx_get(struct tee_context *ctx);
> -void teedev_ctx_put(struct tee_context *ctx);
> -
> struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
> struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
> unsigned long addr, size_t length);
> diff --git a/include/linux/tee_core.h b/include/linux/tee_core.h
> index a38494d6b5f4..284ca6b3e03a 100644
> --- a/include/linux/tee_core.h
> +++ b/include/linux/tee_core.h
> @@ -65,8 +65,9 @@ struct tee_device {
> /**
> * struct tee_driver_ops - driver operations vtable
> * @get_version: returns version of driver
> - * @open: called when the device file is opened
> - * @release: release this open file
> + * @open: called for a context when the device file is opened
> + * @close_context: called when the device file is closed
> + * @release: called to release the context
> * @open_session: open a new session
> * @close_session: close a session
> * @system_session: declare session as a system session
> @@ -76,11 +77,17 @@ struct tee_device {
> * @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
> + *
> + * The context given to @open might last longer than the device file if it is
> + * tied to other resources in the TEE driver. @close_context is called when the
> + * client closes the device file, even if there are existing references to the
> + * context. The TEE driver can use @close_context to start cleaning up.
> */
> struct tee_driver_ops {
> void (*get_version)(struct tee_device *teedev,
> struct tee_ioctl_version_data *vers);
> int (*open)(struct tee_context *ctx);
> + void (*close_context)(struct tee_context *ctx);
> void (*release)(struct tee_context *ctx);
> int (*open_session)(struct tee_context *ctx,
> struct tee_ioctl_open_session_arg *arg,
> @@ -154,6 +161,24 @@ int tee_device_register(struct tee_device *teedev);
> */
> void tee_device_unregister(struct tee_device *teedev);
>
> +/**
> + * tee_device_get() - Increment the user count for a tee_device
> + * @teedev: Pointer to the tee_device
> + *
> + * If tee_device_unregister() has been called and the final user of @teedev
> + * has already released the device, this function will fail to prevent new users
> + * from accessing the device during the unregistration process.
> + *
> + * Returns: true if @teedev remains valid, otherwise false
> + */
> +bool tee_device_get(struct tee_device *teedev);
> +
> +/**
> + * tee_device_put() - Decrease the user count for a tee_device
> + * @teedev: pointer to the tee_device
> + */
> +void tee_device_put(struct tee_device *teedev);
> +
> /**
> * tee_device_set_dev_groups() - Set device attribute groups
> * @teedev: Device to register
> @@ -315,4 +340,25 @@ struct tee_context *teedev_open(struct tee_device *teedev);
> */
> void teedev_close_context(struct tee_context *ctx);
>
> +/**
> + * teedev_ctx_get() - Increment the reference count of a context
> + * @ctx: Pointer to the context
> + *
> + * This function increases the refcount of the context, which is tied to
> + * resources shared by the same tee_device. During the unregistration process,
> + * the context may remain valid even after tee_device_unregister() has returned.
> + *
> + * Users should ensure that the context's refcount is properly decreased before
> + * calling tee_device_put(), typically within the context's release() function.
> + * Alternatively, users can call tee_device_get() and teedev_ctx_get() together
> + * and release them simultaneously (see shm_alloc_helper()).
> + */
> +void teedev_ctx_get(struct tee_context *ctx);
> +
> +/**
> + * teedev_ctx_put() - Decrease reference count on a context
> + * @ctx: pointer to the context
> + */
> +void teedev_ctx_put(struct tee_context *ctx);
> +
> #endif /*__TEE_CORE_H*/
>
> --
> 2.34.1
>