On Fri, Dec 13, 2024 at 5:11 AM Konrad Dybcio
<konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
>
> On 23.11.2024 3:41 AM, Rob Clark wrote:
> > On Fri, Nov 22, 2024 at 4:19 PM Konrad Dybcio
> > <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
> >>
> >> On 22.11.2024 4:51 PM, Rob Clark wrote:
> >>> On Fri, Nov 22, 2024 at 4:21 AM Konrad Dybcio
> >>> <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
> >>>>
> >>>> On 21.11.2024 5:48 PM, Rob Clark wrote:
> >>>>> From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >>>>>
> >>>>> Debugging incorrect UAPI usage tends to be a bit painful, so add a
> >>>>> helper macro to make it easier to add debug logging which can be enabled
> >>>>> at runtime via drm.debug.
> >>>>>
> >>>>> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> >>>>> ---
> >>>>
> >>>> [...]
> >>>>
> >>>>> +/* Helper for returning a UABI error with optional logging which can make
> >>>>> + * it easier for userspace to understand what it is doing wrong.
> >>>>> + */
> >>>>> +#define UERR(err, drm, fmt, ...) \
> >>>>> + ({ DRM_DEV_DEBUG_DRIVER((drm)->dev, fmt, ##__VA_ARGS__); -(err); })
> >>>>> +
> >>>>> #define DBG(fmt, ...) DRM_DEBUG_DRIVER(fmt"\n", ##__VA_ARGS__)
> >>>>> #define VERB(fmt, ...) if (0) DRM_DEBUG_DRIVER(fmt"\n", ##__VA_ARGS__)
> >>>>
> >>>> I'm generally not a fan of adding driver-specific debug prints..
> >>>>
> >>>> Maybe that's something that could be pushed to the drm-common layer
> >>>> or even deeper down the stack?
> >>>
> >>> Even if we had something like DRM_DBG_UABI_ERROR() I'd probably still
> >>> just #define UERR() to be a wrapper for it, since line length/wrapping
> >>> tends to be a bit of a challenge. And I have a fairly substantial
> >>> patch stack on top of this adding sparse/vm_bind support. (Debugging
> >>> that was actually the motivation for this patch.)
> >>
> >> Alright, let's not get in the way then
> >>
> >>> I noticed that xe has something similar, but slightly different shape,
> >>> in the form of XE_IOCTL_DBG().. but that kinda just moves the line
> >>> length problem into the if() conditional. (And doesn't provide the
> >>> benefit of being able to display the incorrect param.)
> >>
> >> Maybe rust comes one day and the lines will start growing vertically ;)
> >
> > Rust for the userspace facing rendernode side of the driver, in
> > particular, would be interesting for me, tbh. Especially if handle
> > related rust<->c layers are designed properly. I've lost track of how
> > many handle lifetime race condition UAF's I've seen ;-)
> >
> > Re-writing entire drivers is a big lift, especially when there is so
> > much hw+features to enable. KMS is limited to drm master (generally a
> > somewhat privileged process), so less of a concern from a security
> > standpoint. Much of the GPU side of things is "boring" power related
> > stuff (suspend/resume/devfreq). But the rendernode ioctls are open to
> > any process that can use the GPU in a typical setup.
>
> The boring part would benefit greatly from automatic scope exit
> cleanup.. We've had lots of issues in the past with that (that are
> hopefully? sorted out now, or should I say, for now)
Maybe some of the cleanup.h stuff would be useful?
BR,
-R
