[Intel-gfx] [PATCH] drm: Warn if plane/crtc/encoder/connector index exceeds our 32bit bitmasks

[Harry Wentland]

On 2018-01-24 01:37 PM, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We use 32bit bitmasks to track planes/crtcs/encoders/connectors.
> Naturally we can only do that if the index of those objects stays
> below 32. Issue a warning whenever we exceed that limit, hopefully
> prompting someone to fix the problem.
> 
> Or should we just outright fail the object initializatio perhaps?
> 

This would make sense in my opinion. index >= 32 looks like it would lead to completely undefined behavior when trying to attach objects to each other.

Harry

> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 3 +++
>  drivers/gpu/drm/drm_crtc.c      | 3 +++
>  drivers/gpu/drm/drm_encoder.c   | 3 +++
>  drivers/gpu/drm/drm_plane.c     | 3 +++
>  4 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index b85a7749709d..9278a81c5d54 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -211,6 +211,9 @@ int drm_connector_init(struct drm_device *dev,
>  	connector->index = ret;
>  	ret = 0;
>  
> +	/* we have 32bit connector bitmasks */
> +	WARN_ON(connector->index >= 32);
> +
>  	connector->connector_type = connector_type;
>  	connector->connector_type_id =
>  		ida_simple_get(connector_ida, 1, 0, GFP_KERNEL);
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index f0556e654116..e27ffa3561af 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -318,6 +318,9 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
>  	list_add_tail(&crtc->head, &config->crtc_list);
>  	crtc->index = config->num_crtc++;
>  
> +	/* we have 32bit crtc bitmasks */
> +	WARN_ON(crtc->index >= 32);
> +
>  	crtc->primary = primary;
>  	crtc->cursor = cursor;
>  	if (primary && !primary->possible_crtcs)
> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> index 59e0ebe733f8..66d0cdd217fa 100644
> --- a/drivers/gpu/drm/drm_encoder.c
> +++ b/drivers/gpu/drm/drm_encoder.c
> @@ -136,6 +136,9 @@ int drm_encoder_init(struct drm_device *dev,
>  	list_add_tail(&encoder->head, &dev->mode_config.encoder_list);
>  	encoder->index = dev->mode_config.num_encoder++;
>  
> +	/* we have 32bit encoder bitmasks */
> +	WARN_ON(encoder->index >= 32);
> +
>  out_put:
>  	if (ret)
>  		drm_mode_object_unregister(dev, &encoder->base);
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 2c90519576a3..0a8d807603c1 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -242,6 +242,9 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
>  	list_add_tail(&plane->head, &config->plane_list);
>  	plane->index = config->num_total_plane++;
>  
> +	/* we have 32bit plane bitmasks */
> +	WARN_ON(plane->index >= 32);
> +
>  	drm_object_attach_property(&plane->base,
>  				   config->plane_type_property,
>  				   plane->type);
>