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Message-ID: <9c143438-82ee-47ac-acc5-00d58960afe5@oss.qualcomm.com>
Date: Wed, 9 Apr 2025 10:20:47 +1000
From: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
To: Jens Wiklander <jens.wiklander@...aro.org>
Cc: Sumit Garg <sumit.garg@...nel.org>,
Bjorn Andersson
<andersson@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
Apurupa Pattapu <quic_apurupa@...cinc.com>,
Kees Cook <kees@...nel.org>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
linux-arm-msm@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 02/11] tee: add close_context to TEE driver operation
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@....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@....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
>>
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