On Fri, May 24, 2019 at 03:12:26PM +0300, Ville Syrjälä wrote:
> On Fri, May 24, 2019 at 11:10:09AM +0000, Brian Starkey wrote:
> > Hi,
> >
> > On Tue, May 21, 2019 at 09:45:58AM +0100, james qian wang (Arm Technology China) wrote:
> > > On Thu, May 16, 2019 at 09:57:49PM +0800, Ayan Halder wrote:
> > > > On Thu, Apr 04, 2019 at 12:06:14PM +0100, james qian wang (Arm Technology China) wrote:
> > > > >
> > > > > +static int
> > > > > +komeda_fb_afbc_size_check(struct komeda_fb *kfb, struct drm_file *file,
> > > > > + const struct drm_mode_fb_cmd2 *mode_cmd)
> > > > > +{
> > > > > + struct drm_framebuffer *fb = &kfb->base;
> > > > > + const struct drm_format_info *info = fb->format;
> > > > > + struct drm_gem_object *obj;
> > > > > + u32 alignment_w = 0, alignment_h = 0, alignment_header;
> > > > > + u32 n_blocks = 0, min_size = 0;
> > > > > +
> > > > > + obj = drm_gem_object_lookup(file, mode_cmd->handles[0]);
> > > > > + if (!obj) {
> > > > > + DRM_DEBUG_KMS("Failed to lookup GEM object\n");
> > > > > + return -ENOENT;
> > > > > + }
> > > > > +
> > > > > + switch (fb->modifier & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) {
> > > > > + case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8:
> > > > > + alignment_w = 32;
> > > > > + alignment_h = 8;
> > > > > + break;
> > > > > + case AFBC_FORMAT_MOD_BLOCK_SIZE_16x16:
> > > > > + alignment_w = 16;
> > > > > + alignment_h = 16;
> > > > > + break;
> > > > > + default:
> > > > Can we have something like a warn here ?
> > >
> > > will add a WARN here.
> > >
> >
> > I think it's better not to. fb->modifier comes from
> > userspace, so a malicious app could spam us with WARNs, effectively
> > dos-ing the system. -EINVAL should be sufficient.
>
> Should probably check that the entire modifier+format is
> actually valid. Otherwise you risk passing on a bogus
> modifier deeper into the driver which may trigger
> interesting bugs.
>
> Also theoretically (however unlikely) some broken userspace
> might start to depend on the ability to create framebuffers
> with crap modifiers, which could later break if you change
> the way you handle the modifiers. Then you're stuck between
> the rock and hard place because you can't break existing
> userspace but you still want to change the way modifiers
> are handled in the kernel.
>
> Best not give userspace too much rope IMO. Two ways to go about
> that:
> 1) drm_any_plane_has_format() (assumes your .format_mod_supported()
> does its job properly)
> 2) roll your own
>
> --
> Ville Syrjälä
> Intel
Hi Brian & Ville:
komed has a format+modifier check before the fb size check.
and for komeda_fb_create, the first step is do the format+modifier
check, the size check is the furthur check after the such format
valid check. and the detailed fb_create is like:
struct drm_framebuffer *
komeda_fb_create(struct drm_device *dev, struct drm_file *file,
const struct drm_mode_fb_cmd2 *mode_cmd)
{
...
/* Step 1: format+modifier valid check, if it can not be support,
* get_format_caps will return a NULL ptr.
*/
kfb->format_caps = komeda_get_format_caps(&mdev->fmt_tbl,
mode_cmd->pixel_format,
mode_cmd->modifier[0]);
if (!kfb->format_caps) {
DRM_DEBUG_KMS("FMT %x is not supported.\n",
mode_cmd->pixel_format);
kfree(kfb);
return ERR_PTR(-EINVAL);
}
drm_helper_mode_fill_fb_struct(dev, &kfb->base, mode_cmd);
/* step 2, do the size check */
if (kfb->base.modifier)
ret = komeda_fb_afbc_size_check(kfb, file, mode_cmd);
else
ret = komeda_fb_none_afbc_size_check(mdev, kfb, file, mode_cmd);
if (ret < 0)
goto err_cleanup;
...
}
So theoretically, the WARN in step2 is redundant if get_format_caps
function has no problem. :). the WARN here is only for reporting
the kernel BUG or code inconsitent with format caps check and the
fb size check. And I agree, basically it will not happene.
@Brian, I'm Ok to remove it. :)
@Ville:
Basically komeda follow the way-1, but a little improvement for
matching komeda's requirement. for komeda which will do two level's
format+modifier check.
1). In fb_create, A roughly check to see if the format+modifier can be
supported by current HW.
2). In plane_atomic_check: to see if the format+modifier can be
supported for a specific layer and with a specific configuration (ROT)
This is a format valid check example for plane_check.
https://patchwork.freedesktop.org/patch/301140/?series=59747&rev=2
James
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
