[Intel-gfx] [PATCH] drm/i915: Use GEM_WARN_ON to catch invalid engine indices.

[Michal Wajdeczko]

On Thu, Mar 02, 2017 at 07:33:26AM +0000, Tvrtko Ursulin wrote:
> 
> On 01/03/2017 20:27, Michal Wajdeczko wrote:
> > Engine related definitions are located in different files
> > and it is easy to break their cross dependency.
> > 
> > v2: compare against array size
> > v3: don't use BUILD_BUG (Tvrtko)
> > 
> > Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> > Cc: Jani Nikula <jani.nikula at intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_engine_cs.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> > index a238304..8675164 100644
> > --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> > @@ -89,7 +89,11 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
> >  	const struct engine_info *info = &intel_engines[id];
> 
> Just need to move this assignment after the assert.

I was thinking about it, but decided to leave as is, as this is just
pointer assignment and there is no read/write from this pointer.
But I'll move it, to make this code even more robust ;)

> 
> >  	struct intel_engine_cs *engine;
> > 
> > -	GEM_BUG_ON(dev_priv->engine[id]);
> > +	if (GEM_WARN_ON((unsigned)id >= ARRAY_SIZE(intel_engines)))
> > +		return -EINVAL;
> > +	if (GEM_WARN_ON((unsigned)id >= ARRAY_SIZE(dev_priv->engine)))
> > +		return -EINVAL;
> > +
> >  	engine = kzalloc(sizeof(*engine), GFP_KERNEL);
> >  	if (!engine)
> >  		return -ENOMEM;
> > @@ -105,6 +109,7 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
> >  	/* Nothing to do here, execute in order of dependencies */
> >  	engine->schedule = NULL;
> > 
> > +	GEM_BUG_ON(dev_priv->engine[id]);
> 
> It doesn't really matter but I think moving this one was not needed.

Moved here just to correlate this assert with the actual critical assignment
from the line below. I can revert it if you prefer old way.

> 
> >  	dev_priv->engine[id] = engine;
> >  	return 0;
> >  }
> > 
>