diff mbox series

[01/22] virtio: store owner from modules with register_virtio_driver()

Message ID 20240327-module-owner-virtio-v1-1-0feffab77d99@linaro.org
State Accepted
Commit ffe6176b7f53ca0c99355f13e14a33a40cf49406
Headers show
Series virtio: store owner from modules with register_virtio_driver() | expand

Commit Message

Krzysztof Kozlowski March 27, 2024, 12:40 p.m. UTC
Modules registering driver with register_virtio_driver() might forget to
set .owner field.  i2c-virtio.c for example has it missing.  The field
is used by some of other kernel parts for reference counting
(try_module_get()), so it is expected that drivers will set it.

Solve the problem by moving this task away from the drivers to the core
amba bus code, just like we did for platform_driver in
commit 9447057eaff8 ("platform_device: use a macro instead of
platform_driver_register").

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
 Documentation/driver-api/virtio/writing_virtio_drivers.rst | 1 -
 drivers/virtio/virtio.c                                    | 6 ++++--
 include/linux/virtio.h                                     | 7 +++++--
 3 files changed, 9 insertions(+), 5 deletions(-)

Comments

Stefano Garzarella March 29, 2024, 11:42 a.m. UTC | #1
On Wed, Mar 27, 2024 at 01:40:54PM +0100, Krzysztof Kozlowski wrote:
>Modules registering driver with register_virtio_driver() might forget to
>set .owner field.  i2c-virtio.c for example has it missing.  The field
>is used by some of other kernel parts for reference counting
>(try_module_get()), so it is expected that drivers will set it.
>
>Solve the problem by moving this task away from the drivers to the core
>amba bus code, just like we did for platform_driver in
>commit 9447057eaff8 ("platform_device: use a macro instead of
>platform_driver_register").
>
>Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>---
> Documentation/driver-api/virtio/writing_virtio_drivers.rst | 1 -
> drivers/virtio/virtio.c                                    | 6 ++++--
> include/linux/virtio.h                                     | 7 +++++--
> 3 files changed, 9 insertions(+), 5 deletions(-)
>
>diff --git a/Documentation/driver-api/virtio/writing_virtio_drivers.rst b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
>index e14c58796d25..e5de6f5d061a 100644
>--- a/Documentation/driver-api/virtio/writing_virtio_drivers.rst
>+++ b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
>@@ -97,7 +97,6 @@ like this::
>
> 	static struct virtio_driver virtio_dummy_driver = {
> 		.driver.name =  KBUILD_MODNAME,
>-		.driver.owner = THIS_MODULE,
> 		.id_table =     id_table,
> 		.probe =        virtio_dummy_probe,
> 		.remove =       virtio_dummy_remove,
>diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
>index f173587893cb..9510c551dce8 100644
>--- a/drivers/virtio/virtio.c
>+++ b/drivers/virtio/virtio.c
>@@ -362,14 +362,16 @@ static const struct bus_type virtio_bus = {
> 	.remove = virtio_dev_remove,
> };
>
>-int register_virtio_driver(struct virtio_driver *driver)
>+int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
> {
> 	/* Catch this early. */
> 	BUG_ON(driver->feature_table_size && !driver->feature_table);
> 	driver->driver.bus = &virtio_bus;
>+	driver->driver.owner = owner;
>+

`.driver.name =  KBUILD_MODNAME` also seems very common, should we put
that in the macro as well?

> 	return driver_register(&driver->driver);
> }
>-EXPORT_SYMBOL_GPL(register_virtio_driver);
>+EXPORT_SYMBOL_GPL(__register_virtio_driver);
>
> void unregister_virtio_driver(struct virtio_driver *driver)
> {
>diff --git a/include/linux/virtio.h b/include/linux/virtio.h
>index b0201747a263..26c4325aa373 100644
>--- a/include/linux/virtio.h
>+++ b/include/linux/virtio.h
>@@ -170,7 +170,7 @@ size_t virtio_max_dma_size(const struct virtio_device *vdev);
>
> /**
>  * struct virtio_driver - operations for a virtio I/O driver
>- * @driver: underlying device driver (populate name and owner).
>+ * @driver: underlying device driver (populate name).
>  * @id_table: the ids serviced by this driver.
>  * @feature_table: an array of feature numbers supported by this driver.
>  * @feature_table_size: number of entries in the feature table array.
>@@ -208,7 +208,10 @@ static inline struct virtio_driver *drv_to_virtio(struct device_driver *drv)
> 	return container_of(drv, struct virtio_driver, driver);
> }
>
>-int register_virtio_driver(struct virtio_driver *drv);
>+/* use a macro to avoid include chaining to get THIS_MODULE */
>+#define register_virtio_driver(drv) \
>+	__register_virtio_driver(drv, THIS_MODULE)
>+int __register_virtio_driver(struct virtio_driver *drv, struct module *owner);
> void unregister_virtio_driver(struct virtio_driver *drv);
>
> /* module_virtio_driver() - Helper macro for drivers that don't do
>
>-- 
>2.34.1
>
Krzysztof Kozlowski March 29, 2024, 12:07 p.m. UTC | #2
On 29/03/2024 12:42, Stefano Garzarella wrote:
>> };
>>
>> -int register_virtio_driver(struct virtio_driver *driver)
>> +int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
>> {
>> 	/* Catch this early. */
>> 	BUG_ON(driver->feature_table_size && !driver->feature_table);
>> 	driver->driver.bus = &virtio_bus;
>> +	driver->driver.owner = owner;
>> +
> 
> `.driver.name =  KBUILD_MODNAME` also seems very common, should we put
> that in the macro as well?

This is a bit different thing. Every driver is expected to set owner to
itself (THIS_MODULE), but is every driver name KBUILD_MODNAME? Remember
that this overrides whatever driver actually put there.

Best regards,
Krzysztof
Stefano Garzarella March 29, 2024, 1:28 p.m. UTC | #3
On Fri, Mar 29, 2024 at 01:07:31PM +0100, Krzysztof Kozlowski wrote:
>On 29/03/2024 12:42, Stefano Garzarella wrote:
>>> };
>>>
>>> -int register_virtio_driver(struct virtio_driver *driver)
>>> +int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
>>> {
>>> 	/* Catch this early. */
>>> 	BUG_ON(driver->feature_table_size && !driver->feature_table);
>>> 	driver->driver.bus = &virtio_bus;
>>> +	driver->driver.owner = owner;
>>> +
>>
>> `.driver.name =  KBUILD_MODNAME` also seems very common, should we put
>> that in the macro as well?
>
>This is a bit different thing. Every driver is expected to set owner to
>itself (THIS_MODULE), but is every driver name KBUILD_MODNAME?

Nope, IIUC we have 2 exceptions:
- drivers/firmware/arm_scmi/virtio.c
- arch/um/drivers/virt-pci.c

>Remember that this overrides whatever driver actually put there.

They can call __register_virtio_driver() where we can add the `name`
parameter. That said, I don't have a strong opinion, we can leave it
as it is.

Thanks,
Stefano
diff mbox series

Patch

diff --git a/Documentation/driver-api/virtio/writing_virtio_drivers.rst b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
index e14c58796d25..e5de6f5d061a 100644
--- a/Documentation/driver-api/virtio/writing_virtio_drivers.rst
+++ b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
@@ -97,7 +97,6 @@  like this::
 
 	static struct virtio_driver virtio_dummy_driver = {
 		.driver.name =  KBUILD_MODNAME,
-		.driver.owner = THIS_MODULE,
 		.id_table =     id_table,
 		.probe =        virtio_dummy_probe,
 		.remove =       virtio_dummy_remove,
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index f173587893cb..9510c551dce8 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -362,14 +362,16 @@  static const struct bus_type virtio_bus = {
 	.remove = virtio_dev_remove,
 };
 
-int register_virtio_driver(struct virtio_driver *driver)
+int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
 {
 	/* Catch this early. */
 	BUG_ON(driver->feature_table_size && !driver->feature_table);
 	driver->driver.bus = &virtio_bus;
+	driver->driver.owner = owner;
+
 	return driver_register(&driver->driver);
 }
-EXPORT_SYMBOL_GPL(register_virtio_driver);
+EXPORT_SYMBOL_GPL(__register_virtio_driver);
 
 void unregister_virtio_driver(struct virtio_driver *driver)
 {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index b0201747a263..26c4325aa373 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -170,7 +170,7 @@  size_t virtio_max_dma_size(const struct virtio_device *vdev);
 
 /**
  * struct virtio_driver - operations for a virtio I/O driver
- * @driver: underlying device driver (populate name and owner).
+ * @driver: underlying device driver (populate name).
  * @id_table: the ids serviced by this driver.
  * @feature_table: an array of feature numbers supported by this driver.
  * @feature_table_size: number of entries in the feature table array.
@@ -208,7 +208,10 @@  static inline struct virtio_driver *drv_to_virtio(struct device_driver *drv)
 	return container_of(drv, struct virtio_driver, driver);
 }
 
-int register_virtio_driver(struct virtio_driver *drv);
+/* use a macro to avoid include chaining to get THIS_MODULE */
+#define register_virtio_driver(drv) \
+	__register_virtio_driver(drv, THIS_MODULE)
+int __register_virtio_driver(struct virtio_driver *drv, struct module *owner);
 void unregister_virtio_driver(struct virtio_driver *drv);
 
 /* module_virtio_driver() - Helper macro for drivers that don't do