On Wed, 2009-08-05 at 10:50 +0200, Thomas Hellström wrote:
> Michel Dänzer wrote:
> > From: Michel Dänzer <daen...@vmware.com>
> >
> > Make sure bo->vm_node is valid, to prevent crashes in the fault handler, and
> > adjust vma->vm_pgoff according to it, so userspace attempts to access
> > /dev/fb*
> > mappings don't always result in SIGBUS.
> >
> > Signed-off-by: Michel Dänzer <daen...@vmware.com>
> > ---
> > drivers/gpu/drm/ttm/ttm_bo_vm.c | 6 ++++++
> > 1 files changed, 6 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > index 27b146c..57d0c94 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > @@ -282,7 +282,13 @@ int ttm_fbdev_mmap(struct vm_area_struct *vma, struct
> > ttm_buffer_object *bo)
> > if (vma->vm_pgoff != 0)
> > return -EACCES;
> >
> > + if (!bo->vm_node) {
> > + printk(KERN_ERR TTM_PFX "bo->vm_node == NULL\n");
> > + return -EACCES;
> > + }
> >
>
> Michel,
> Did you actually hit a bo with an invalid vm_node?
See patch 3 - the radeon driver used to create the fbcon BO as
kernel-only, so when I tried passing that to ttm_fbdev_mmap()
all /dev/fb* userspace mappings mysteriously caught SIGBUS on access. It
took me a while to track that down, this is basically a debugging aid
for bugs like that.
--
Earthling Michel Dänzer | http://www.vmware.com
Libre software enthusiast | Debian, X and DRI developer
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