On Thu, Mar 01, 2018 at 02:14:41PM +0000, Eric Engestrom wrote:
>
>
> On March 1, 2018 1:31:53 PM UTC, Thierry Reding <thierry.red...@gmail.com>
> wrote:
> > From: Thierry Reding <tred...@nvidia.com>
> >
> > ARM SoCs usually have their DRM/KMS devices on the platform bus, so
> > add
> > support for this bus in order to allow use of the DRI_PRIME
> > environment
> > variable with those devices.
> >
> > While at it, also support the host1x bus, which is effectively the
> > same
> > but uses an additional layer in the bus hierarchy.
> >
> > Note that it isn't enough to support the bus that has the rendering
> > GPU
> > because the loader code will also try to construct an ID path tag for
> > a
> > scanout-only device if it is the default that is being opened.
> >
> > The ID path tag for a device can be obtained by running udevadm info
> > on
> > the device node:
> >
> > $ udevadm info /dev/dri/card0
> >
> > and looking up the ID_PATH_TAG entry in the output.
> >
> > Signed-off-by: Thierry Reding <tred...@nvidia.com>
> > ---
> > src/loader/loader.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/src/loader/loader.c b/src/loader/loader.c
> > index 92b4c5204b19..ca578b8cd232 100644
> > --- a/src/loader/loader.c
> > +++ b/src/loader/loader.c
> > @@ -120,6 +120,33 @@ static char
> > *drm_construct_id_path_tag(drmDevicePtr device)
> > device->businfo.pci->func) < 0) {
> > return NULL;
> > }
> > + } else if (device->bustype == DRM_BUS_PLATFORM ||
> > + device->bustype == DRM_BUS_HOST1X) {
> > + char *fullname, *name, *address;
> > +
> > + if (device->bustype == DRM_BUS_PLATFORM)
> > + fullname = device->businfo.platform->fullname;
> > + else
> > + fullname = device->businfo.host1x->fullname;
> > +
> > + name = strrchr(fullname, '/');
> > + if (!name)
> > + name = strdup(fullname);
> > + else
> > + name = strdup(++name);
>
> Looks like UB to me; how about this instead?
>
> name = strdup(name + 1);I don't think the above is problematic. ++name is guaranteed to be evaluated before the call to strdup(), and name can't be overwritten by the assignment until after strdup() is done. But I have no objection to change this to your suggestion, which is slightly easier to read irrespective of UB or not. I'm honestly not exactly sure why I wrote it in this strange way. I /think/ an earlier version of the patch wasn't assigning to name but another variable and reusing the name variable, which is why it had to be incremented. But that's no longer necessary. > With that: > Reviewed-by: Eric Engestrom <e...@engestrom.ch> Thanks, Thierry
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