tee: add close_context to TEE driver operation

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.

Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Harshal Dev <quic_hdev@quicinc.com>
Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

Author: qc-azarrabi

drivers/tee/tee_core.c

@@ -80,6 +80,7 @@ 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)
 {
@@ -97,11 +98,15 @@ 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);
 }
@@ -1112,6 +1117,7 @@ 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)
 {
@@ -1124,6 +1130,7 @@ 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

drivers/tee/tee_private.h

@@ -23,12 +23,6 @@ struct tee_shm_dmabuf_ref {
 
 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);

include/linux/tee_core.h

@@ -76,8 +76,9 @@ 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
@@ -87,11 +88,17 @@ 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,
@@ -200,6 +207,24 @@ int tee_device_register_dma_heap(struct tee_device *teedev,
 				 struct tee_protmem_pool *pool);
 void tee_device_put_all_dma_heaps(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
@@ -374,4 +399,25 @@ 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*/