Re: [PATCH] drm/rockchip: use drm_gem_mmap helpers

[Daniel Vetter]

On Tue, Jul 07, 2015 at 05:03:36PM +0800, Daniel Kurtz wrote:
> Rather than (incompletely [0]) re-implementing drm_gem_mmap() and
> drm_gem_mmap_obj() helpers, call them directly from the rockchip mmap
> routines.
> 
> Once the core functions return successfully, the rockchip mmap routines
> can still use dma_mmap_attrs() to simply mmap the entire buffer.
> 
> [0] Previously, we were performing the mmap() without first taking a
> reference on the underlying gem buffer.  This could leak ptes if the gem
> object is destroyed while userspace is still holding the mapping.
> 
> Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Applied to topic/drm-fixes to make sure it won't get lost, but I expect
rockchip maintainers to pick this one up.
-Daniel

> 
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 67 +++++++++++++++--------------
>  1 file changed, 34 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> index eb2282c..eba5f8a 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> @@ -54,55 +54,56 @@ static void rockchip_gem_free_buf(struct rockchip_gem_object *rk_obj)
>  		       &rk_obj->dma_attrs);
>  }
>  
> -int rockchip_gem_mmap_buf(struct drm_gem_object *obj,
> -			  struct vm_area_struct *vma)
> +static int rockchip_drm_gem_object_mmap(struct drm_gem_object *obj,
> +					struct vm_area_struct *vma)
> +
>  {
> +	int ret;
>  	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
>  	struct drm_device *drm = obj->dev;
> -	unsigned long vm_size;
>  
> -	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> -	vm_size = vma->vm_end - vma->vm_start;
> -
> -	if (vm_size > obj->size)
> -		return -EINVAL;
> +	/*
> +	 * dma_alloc_attrs() allocated a struct page table for rk_obj, so clear
> +	 * VM_PFNMAP flag that was set by drm_gem_mmap_obj()/drm_gem_mmap().
> +	 */
> +	vma->vm_flags &= ~VM_PFNMAP;
>  
> -	return dma_mmap_attrs(drm->dev, vma, rk_obj->kvaddr, rk_obj->dma_addr,
> +	ret = dma_mmap_attrs(drm->dev, vma, rk_obj->kvaddr, rk_obj->dma_addr,
>  			     obj->size, &rk_obj->dma_attrs);
> +	if (ret)
> +		drm_gem_vm_close(vma);
> +
> +	return ret;
>  }
>  
> -/* drm driver mmap file operations */
> -int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
> +int rockchip_gem_mmap_buf(struct drm_gem_object *obj,
> +			  struct vm_area_struct *vma)
>  {
> -	struct drm_file *priv = filp->private_data;
> -	struct drm_device *dev = priv->minor->dev;
> -	struct drm_gem_object *obj;
> -	struct drm_vma_offset_node *node;
> +	struct drm_device *drm = obj->dev;
>  	int ret;
>  
> -	if (drm_device_is_unplugged(dev))
> -		return -ENODEV;
> +	mutex_lock(&drm->struct_mutex);
> +	ret = drm_gem_mmap_obj(obj, obj->size, vma);
> +	mutex_unlock(&drm->struct_mutex);
> +	if (ret)
> +		return ret;
>  
> -	mutex_lock(&dev->struct_mutex);
> +	return rockchip_drm_gem_object_mmap(obj, vma);
> +}
>  
> -	node = drm_vma_offset_exact_lookup(dev->vma_offset_manager,
> -					   vma->vm_pgoff,
> -					   vma_pages(vma));
> -	if (!node) {
> -		mutex_unlock(&dev->struct_mutex);
> -		DRM_ERROR("failed to find vma node.\n");
> -		return -EINVAL;
> -	} else if (!drm_vma_node_is_allowed(node, filp)) {
> -		mutex_unlock(&dev->struct_mutex);
> -		return -EACCES;
> -	}
> +/* drm driver mmap file operations */
> +int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct drm_gem_object *obj;
> +	int ret;
>  
> -	obj = container_of(node, struct drm_gem_object, vma_node);
> -	ret = rockchip_gem_mmap_buf(obj, vma);
> +	ret = drm_gem_mmap(filp, vma);
> +	if (ret)
> +		return ret;
>  
> -	mutex_unlock(&dev->struct_mutex);
> +	obj = vma->vm_private_data;
>  
> -	return ret;
> +	return rockchip_drm_gem_object_mmap(obj, vma);
>  }
>  
>  struct rockchip_gem_object *
> -- 
> 2.4.3.573.g4eafbef
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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