[Intel-gfx] [PATCH v2] drm: Warn if plane/crtc/encoder/connector index exceeds our 32bit bitmasks

[Ville Syrjälä]

On Thu, Jan 25, 2018 at 10:17:21AM +0100, Maarten Lankhorst wrote:
> Op 24-01-18 om 22:47 schreef Ville Syrjala:
> > 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.
> >
> > For connectors the issue is a bit more complicated as they can
> > be created/destroyed at runtime due to MST. So the problem is no
> > longer a purely theoretical programmer error. As the connector
> > indexes are allocated via ida, we can simply limit the maximum
> > value the ida is allowed to hand out. The error handling is already
> > in place.
> >
> > v2: Return an error to the caller (Harry)
> >
> > Cc: Harry Wentland <harry.wentland at amd.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_connector.c | 3 ++-
> >  drivers/gpu/drm/drm_crtc.c      | 4 ++++
> >  drivers/gpu/drm/drm_encoder.c   | 4 ++++
> >  drivers/gpu/drm/drm_plane.c     | 4 ++++
> >  4 files changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index b85a7749709d..f4a689ab990a 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -205,7 +205,8 @@ int drm_connector_init(struct drm_device *dev,
> >  	connector->dev = dev;
> >  	connector->funcs = funcs;
> >  
> > -	ret = ida_simple_get(&config->connector_ida, 0, 0, GFP_KERNEL);
> > +	/* connector index is used with 32bit bitmasks */
> > +	ret = ida_simple_get(&config->connector_ida, 0, 32, GFP_KERNEL);
> >  	if (ret < 0)
> >  		goto out_put;
> >  	connector->index = ret;
> Could we also put a DRM_DEBUG_KMS in here if allocation fails? Since it's more likely to happen now..

I was actually pondering using DRM_ERROR(), or maybe even WARN(). It
shouldn't be directly user triggerable so I think we want to get the
bugreport if we do run out of bits.

> 
> Otherwise looks good so with that change:
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index f0556e654116..5b4be382a1d7 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -282,6 +282,10 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
> >  	WARN_ON(primary && primary->type != DRM_PLANE_TYPE_PRIMARY);
> >  	WARN_ON(cursor && cursor->type != DRM_PLANE_TYPE_CURSOR);
> >  
> > +	/* crtc index is used with 32bit bitmasks */
> > +	if (WARN_ON(config->num_crtc >= 32))
> > +		return -EINVAL;
> > +
> >  	crtc->dev = dev;
> >  	crtc->funcs = funcs;
> >  
> > diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> > index 59e0ebe733f8..273e1c59c54a 100644
> > --- a/drivers/gpu/drm/drm_encoder.c
> > +++ b/drivers/gpu/drm/drm_encoder.c
> > @@ -110,6 +110,10 @@ int drm_encoder_init(struct drm_device *dev,
> >  {
> >  	int ret;
> >  
> > +	/* encoder index is used with 32bit bitmasks */
> > +	if (WARN_ON(dev->mode_config.num_encoder >= 32))
> > +		return -EINVAL;
> > +
> >  	ret = drm_mode_object_add(dev, &encoder->base, DRM_MODE_OBJECT_ENCODER);
> >  	if (ret)
> >  		return ret;
> > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> > index 2c90519576a3..22b54663b6e7 100644
> > --- a/drivers/gpu/drm/drm_plane.c
> > +++ b/drivers/gpu/drm/drm_plane.c
> > @@ -173,6 +173,10 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
> >  	unsigned int format_modifier_count = 0;
> >  	int ret;
> >  
> > +	/* plane index is used with 32bit bitmasks */
> > +	if (WARN_ON(config->num_total_plane >= 32))
> > +		return -EINVAL;
> > +
> >  	ret = drm_mode_object_add(dev, &plane->base, DRM_MODE_OBJECT_PLANE);
> >  	if (ret)
> >  		return ret;
> 

-- 
Ville Syrjälä
Intel OTC