Re: [PATCH v3 02/11] tee: add close_context to TEE driver operation

[Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>]

Hi Jens,

On 4/8/2025 12:55 AM, Jens Wiklander wrote:
> Hi Amir,
>
> On Fri, Mar 28, 2025 at 3:48 AM Amirreza Zarrabi
> <amirreza.zarrabi@oss.qualcomm.com> 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_drv.h to make them accessible
>> outside the TEE subsystem.
>>
>> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>
>> ---
>>  drivers/tee/tee_core.c    | 39 +++++++++++++++++++++++++++++++++++++++
>>  drivers/tee/tee_private.h |  6 ------
>>  include/linux/tee_core.h  | 11 +++++++++--
>>  include/linux/tee_drv.h   | 40 ++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 88 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
>> index 24edce4cdbaa..22cc7d624b0c 100644
>> --- a/drivers/tee/tee_core.c
>> +++ b/drivers/tee/tee_core.c
>> @@ -72,6 +72,20 @@ struct tee_context *teedev_open(struct tee_device *teedev)
>>  }
>>  EXPORT_SYMBOL_GPL(teedev_open);
>>
>> +/**
>> + * teedev_ctx_get() - Increment the reference count of a 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()).
>> + *
>> + * @ctx: Pointer to the context
> Please move this @ctx line to before the verbose description of the function.
>
> Cheers,
> Jens

Ack.

Best Regards,
Amir

>
>> + */
>>  void teedev_ctx_get(struct tee_context *ctx)
>>  {
>>         if (ctx->releasing)
>> @@ -79,6 +93,7 @@ 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)
>>  {
>> @@ -89,6 +104,10 @@ static void teedev_ctx_release(struct kref *ref)
>>         kfree(ctx);
>>  }
>>
>> +/**
>> + * teedev_ctx_put() - Decrease reference count on a context
>> + * @ctx: pointer to the context
>> + */
>>  void teedev_ctx_put(struct tee_context *ctx)
>>  {
>>         if (ctx->releasing)
>> @@ -96,11 +115,15 @@ 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);
>>  }
>> @@ -1024,6 +1047,10 @@ int tee_device_register(struct tee_device *teedev)
>>  }
>>  EXPORT_SYMBOL_GPL(tee_device_register);
>>
>> +/**
>> + * 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)
>>  {
>>         mutex_lock(&teedev->mutex);
>> @@ -1037,7 +1064,18 @@ void tee_device_put(struct tee_device *teedev)
>>         }
>>         mutex_unlock(&teedev->mutex);
>>  }
>> +EXPORT_SYMBOL_GPL(tee_device_put);
>>
>> +/**
>> + * 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)
>>  {
>>         mutex_lock(&teedev->mutex);
>> @@ -1049,6 +1087,7 @@ 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..8a4c9e30b652 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,
>> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
>> index a54c203000ed..ce23fd42c5d4 100644
>> --- a/include/linux/tee_drv.h
>> +++ b/include/linux/tee_drv.h
>> @@ -96,6 +96,46 @@ struct tee_param {
>>         } u;
>>  };
>>
>> +/**
>> + * 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);
>> +
>> +/**
>> + * teedev_ctx_get() - Increment the reference count of a 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()).
>> + *
>> + * @ctx: Pointer to the context
>> + */
>> +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);
>> +
>>  /**
>>   * tee_shm_alloc_kernel_buf() - Allocate kernel shared memory for a
>>   *                              particular TEE client driver
>>
>> --
>> 2.34.1
>>