On Wed, Aug 22, 2018 at 10:54:05AM +0200, Daniel Vetter wrote: > For buffer sharing, use dma-buf instead. We can't set smem_start to 0 > unconditionally since that's used by the fbdev mmap default > implementation. And we have plenty of userspace which would like to > keep that working. > > This might break legit userspace - if it does we need to look at a > case-by-cases basis how to handle that. Worst case I expect overrides > for only specific drivers, since anything remotely modern should be > using dma-buf/prime now (which is about 7 years old now for DRM > drivers). > > This issue was uncovered because Noralf's rework to implement a > generic fb_probe also implements it's own fb_mmap callback. Which > means smem_start didn't have to be set anymore, which blew up some > blob in userspace rather badly. > > Cc: Gustavo Padovan <[email protected]> > Cc: Maarten Lankhorst <[email protected]> > Cc: Sean Paul <[email protected]> > Cc: David Airlie <[email protected]> > Cc: John Stultz <[email protected]> > Cc: Noralf Trønnes <[email protected]> > Signed-off-by: Daniel Vetter <[email protected]>
After clarifying on IRC, I think this makes sense. The chance to break userspace requires a very specific configuration that I don't expect will be common. Acked-by: Sean Paul <[email protected]> > --- > drivers/gpu/drm/drm_fb_helper.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > index 4b0dd20bccb8..bcb78693c4f7 100644 > --- a/drivers/gpu/drm/drm_fb_helper.c > +++ b/drivers/gpu/drm/drm_fb_helper.c > @@ -2673,6 +2673,8 @@ __drm_fb_helper_initial_config_and_unlock(struct > drm_fb_helper *fb_helper, > > info = fb_helper->fbdev; > info->var.pixclock = 0; > + /* don't leak any physical addresses to userspace */ > + info->flags |= FBINFO_HIDE_SMEM_START; > > /* Need to drop locks to avoid recursive deadlock in > * register_framebuffer. This is ok because the only thing left to do is > -- > 2.18.0 > -- Sean Paul, Software Engineer, Google / Chromium OS _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
