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With the typical model where the display server opens the file descriptor
and then hands it over to the client(*), we were showing stale data in
debugfs.
Fix it by updating the drm_file->pid on ioctl access from a different
process.
The field is also made RCU protected to allow for lockless readers. Update
side is protected with dev->filelist_mutex.
Before:
$ cat /sys/kernel/debug/dri/0/clients
command pid dev master a uid magic
Xorg 2344 0 y y 0 0
Xorg 2344 0 n y 0 2
Xorg 2344 0 n y 0 3
Xorg 2344 0 n y 0 4
After:
$ cat /sys/kernel/debug/dri/0/clients
command tgid dev master a uid magic
Xorg 830 0 y y 0 0
xfce4-session 880 0 n y 0 1
xfwm4 943 0 n y 0 2
neverball 1095 0 n y 0 3
*)
More detailed and historically accurate description of various handover
implementation kindly provided by Emil Velikov:
"""
The traditional model, the server was the orchestrator managing the
primary device node. From the fd, to the master status and
authentication. But looking at the fd alone, this has varied across
the years.
IIRC in the DRI1 days, Xorg (libdrm really) would have a list of open
fd(s) and reuse those whenever needed, DRI2 the client was responsible
for open() themselves and with DRI3 the fd was passed to the client.
Around the inception of DRI3 and systemd-logind, the latter became
another possible orchestrator. Whereby Xorg and Wayland compositors
could ask it for the fd. For various reasons (hysterical and genuine
ones) Xorg has a fallback path going the open(), whereas Wayland
compositors are moving to solely relying on logind... some never had
fallback even.
Over the past few years, more projects have emerged which provide
functionality similar (be that on API level, Dbus, or otherwise) to
systemd-logind.
"""
v2:
* Fixed typo in commit text and added a fine historical explanation
from Emil.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Tested-by: Rob Clark <robdclark@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230621094824.2348732-1-tvrtko.ursulin@linux.intel.com
Signed-off-by: Christian König <christian.koenig@amd.com>
Instead of the per minor directories only create a single debugfs
directory for the whole device directly when the device is initialized.
For DRM devices each minor gets a symlink to the per device directory
for now until we can be sure that this isn't useful any more in any way.
Accel devices create only the per device directory and also drops the mid
layer callback to create driver specific files.
v2: cleanup accel component as well
v3: fix typo when debugfs is disabled
v4: call drm_debugfs_dev_fini() during release as well,
some kerneldoc typos fixed
v5: rebased and one more kerneldoc fix
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829110115.3442-4-christian.koenig@amd.com
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Commit 2c204f3d53 ("accel: add dedicated minor for accelerator
devices") adds link to accelerator nodes section of DRM internals doc
(Documentation/gpu/drm-internals.rst), but the target doesn't exist.
Instead, there is only an introduction doc for computer accelerator
subsytem.
Link to that doc until there is documentation of accelerator internals.
Fixes: 2c204f3d53 ("accel: add dedicated minor for accelerator devices")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
The accelerator devices are exposed to user-space using a dedicated
major. In addition, they are represented in /dev with new, dedicated
device char names: /dev/accel/accel*. This is done to make sure any
user-space software that tries to open a graphic card won't open
the accelerator device by mistake.
The above implies that the minor numbering should be separated from
the rest of the DRM devices. However, to avoid code duplication, we
want the drm_minor structure to be able to represent the accelerator
device.
To achieve this, we add a new drm_minor* to drm_device that represents
the accelerator device. This pointer is initialized for drivers that
declare they handle compute accelerator, using a new driver feature
flag called DRIVER_COMPUTE_ACCEL. It is important to note that this
driver feature is mutually exclusive with DRIVER_RENDER. Devices that
want to expose both graphics and compute device char files should be
handled by two drivers that are connected using the auxiliary bus
framework.
In addition, we define a different IDR to handle the accelerators
minors. This is done to make the minor's index be identical to the
device index in /dev/. Any access to the IDR is done solely
by functions in accel_drv.c, as the IDR is define as static. The
DRM core functions call those functions in case they detect the minor's
type is DRM_MINOR_ACCEL.
We define a separate accel_open function (from drm_open) that the
accel drivers should set as their open callback function. Both these
functions eventually call the same drm_open_helper(), which had to be
changed to be non-static so it can be called from accel_drv.c.
accel_open() only partially duplicates drm_open as I removed some code
from it that handles legacy devices.
To help new drivers, I defined DEFINE_DRM_ACCEL_FOPS macro to easily
set the required function operations pointers structure.
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Tested-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
drm_file->master pointers should be protected by
drm_device.master_mutex or drm_file.master_lookup_lock when being
dereferenced.
However, in drm_lease.c, there are multiple instances where
drm_file->master is accessed and dereferenced while neither lock is
held. This makes drm_lease.c vulnerable to use-after-free bugs.
We address this issue in 2 ways:
1. Add a new drm_file_get_master() function that calls drm_master_get
on drm_file->master while holding on to
drm_file.master_lookup_lock. Since drm_master_get increments the
reference count of master, this prevents master from being freed until
we unreference it with drm_master_put.
2. In each case where drm_file->master is directly accessed and
eventually dereferenced in drm_lease.c, we wrap the access in a call
to the new drm_file_get_master function, then unreference the master
pointer once we are done using it.
Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-6-desmondcheongzx@gmail.com
Currently, drm_file.master pointers should be protected by
drm_device.master_mutex when being dereferenced. This is because
drm_file.master is not invariant for the lifetime of drm_file. If
drm_file is not the creator of master, then drm_file.is_master is
false, and a call to drm_setmaster_ioctl will invoke
drm_new_set_master, which then allocates a new master for drm_file and
puts the old master.
Thus, without holding drm_device.master_mutex, the old value of
drm_file.master could be freed while it is being used by another
concurrent process.
However, it is not always possible to lock drm_device.master_mutex to
dereference drm_file.master. Through the fbdev emulation code, this
might occur in a deep nest of other locks. But drm_device.master_mutex
is also the outermost lock in the nesting hierarchy, so this leads to
potential deadlocks.
To address this, we introduce a new spin lock at the bottom of the
lock hierarchy that only serializes drm_file.master. With this change,
the value of drm_file.master changes only when both
drm_device.master_mutex and drm_file.master_lookup_lock are
held. Hence, any process holding either of those locks can ensure that
the value of drm_file.master will not change concurrently.
Since no lock depends on the new drm_file.master_lookup_lock, when
drm_file.master is dereferenced, but drm_device.master_mutex cannot be
held, we can safely protect the master pointer with
drm_file.master_lookup_lock.
Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-5-desmondcheongzx@gmail.com
The explicit out-fences in crtc are signaled as part of vblank event,
indicating all framebuffers present on the Atomic Commit request are
scanned out on the screen. Though the fence signal and the vblank event
notification happens at the same time, triggered by the same hardware
vsync event, the timestamp set in both are different. With drivers
supporting precise vblank timestamp the difference between the two
timestamps would be even higher. This might have an impact on use-mode
frameworks using these fence timestamps for purposes other than simple
buffer usage. For instance, the Android framework [1] uses the
retire-fences as an alternative to vblank when frame-updates are in
progress. Set the fence timestamp during send vblank event using a new
drm_send_event_timestamp_locked variant to avoid discrepancies.
[1] https://android.googlesource.com/platform/frameworks/native/+/master/
services/surfaceflinger/Scheduler/Scheduler.cpp#397
Changes in v2:
- Use drm_send_event_timestamp_locked to update fence timestamp
- add more information to commit text
Changes in v3:
- use same backend helper function for variants of drm_send_event to
avoid code duplications
Changes in v4:
- remove WARN_ON from drm_send_event_timestamp_locked
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>
Reviewed-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
[sumits: minor parenthesis alignment correction]
Link: https://patchwork.freedesktop.org/patch/msgid/1610757107-11892-2-git-send-email-veeras@codeaurora.org
This commit reworks the permission handling of the two ioctls. In
particular it enforced the CAP_SYS_ADMIN check only, if:
- we're issuing the ioctl from process other than the one which opened
the node, and
- we are, or were master in the past
This ensures that we:
- do not regress the systemd-logind style of DRM_MASTER arbitrator
- allow applications which do not use systemd-logind to drop their
master capabilities (and regain them at later point) ... w/o running as
root.
See the comment above drm_master_check_perm() for more details.
v1:
- Tweak wording, fixup all checks, add igt test
v2:
- Add a few more comments, grammar nitpicks.
Cc: Adam Jackson <ajax@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Testcase: igt/core_setmaster/master-drop-set-user
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200319172930.230583-1-emil.l.velikov@gmail.com
The file is not part of the global drm resource and can be released
prior to take the global mutex to drop the open_count (and potentially
close) the drm device. As the global mutex is indeed global, not only
within the device but across devices, a slow file release mechanism can
bottleneck the entire system.
However, inside drm_close_helper() there are a number of dev->driver
callbacks that take the drm_device as the first parameter... Worryingly
some of those callbacks may be (implicitly) depending on the global
mutex.
v2: Drop the debug message for the open-count, it's included with the
drm_file_free() debug message -- and for good measure make that up as
reading outside of the mutex.
v3: Separate the calling of the filp cleanup outside of
drm_global_mutex into a new drm_release_noglobal() hook, so that we can
phase the transition. drm/savage relies on the global mutex, and there
may be more, so be cautious.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Thomas Hellström (VMware) <thomas_os@shipmail.org>
Reviewed-by: Thomas Hellström (VMware) <thomas_os@shipmail.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200124125627.125042-1-chris@chris-wilson.co.uk
This removes these unless legacy is enabled.
The lock count init is unneeded anyways since it's kzalloc.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Due to the fact that writeback connectors behave in a special way
in DRM (they always report being disconnected) we might confuse some
userspace. Add a client capability for writeback connectors that will
filter them out for clients that don't understand the capability.
Changelog:
- only accept the capability if the client has already set the
DRM_CLIENT_CAP_ATOMIC one.
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Link: https://patchwork.freedesktop.org/patch/229038/
To enable aspect-ratio support in DRM, blindly exposing the aspect
ratio information along with mode, can break things in existing
non-atomic user-spaces which have no intention or support to use this
aspect ratio information.
To avoid this, a new drm client cap is required to enable a non-atomic
user-space to advertise if it supports modes with aspect-ratio. Based
on this cap value, the kernel will take a call on exposing the aspect
ratio info in modes or not.
This patch adds the client cap for aspect-ratio.
Since no atomic-userspaces blow up on receiving aspect-ratio
information, the client cap for aspect-ratio is always enabled
for atomic clients.
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
V3: rebase
V4: As suggested by Marteen Lankhorst modified the commit message
explaining the need to use the DRM cap for aspect-ratio. Also,
tweaked the comment lines in the code for better understanding and
clarity, as recommended by Shashank Sharma.
V5: rebase
V6: rebase
V7: rebase
V8: rebase
V9: rebase
V10: rebase
V11: rebase
V12: As suggested by Daniel Vetter and Ville Syrjala,
always enable aspect-ratio client cap for atomic userspaces,
if no atomic userspace breaks on aspect-ratio bits.
V13: rebase
V14: rebase
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1525777785-9740-7-git-send-email-ankit.k.nautiyal@intel.com
Sync objects are new toplevel drm object, that contain a
pointer to a fence. This fence can be updated via command
submission ioctls via drivers.
There is also a generic wait obj API modelled on the vulkan
wait API (with code modelled on some amdgpu code).
These objects can be converted to an opaque fd that can be
passes between processes.
v2: rename reference/unreference to put/get (Chris)
fix leaked reference (David Zhou)
drop mutex in favour of cmpxchg (Chris)
v3: cleanups from danvet, rebase on drm_fops rename
check fd_flags is 0 in ioctls.
v4: export find/free, change replace fence to take a
syncobj. In order to support lookup first, replace
later semantics which seem in the end to be cleaner.
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Well, mostly drm_file.h, and clean up all related things:
- I didnt' figure out the difference between preclose and postclose.
The existing explanation in drm-internals.rst didn't convince me,
since it's also really outdated - we clean up pending DRM events in
the core nowadays. I put a FIXME in for the future.
- Another FIXME is to have a macro for default fops.
- Lots of links all around, main areas are to tie the overview in
drm_file.c more into the callbacks in struct drm_device, and the
other is to link render/primary node code to the right sections in
drm-uapi.rst.
- Also moved the open/close stuff to drm_drv.h from drm-internals.rst,
seems like the better place for that information. Since that section
was rather outdated this amounted to full-on rewrite.
A big missing piece here is some overview graph, but I think better to
wait with that one until drm_device and drm_driver are also fully
documented.
v2: Nits from Sean.
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-12-daniel.vetter@ffwll.ch
We might as well dump the drm_file pointer, that's about as useful
a cookie as the pid. Noticed while typing docs for drm_file and friends.
Since the only consumer of this is the tracepoints I think we can safely
change this - those tracepoints should not be uapi relevant at all. It
all goes back to
commit b9c2c9ae88
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date: Thu Jul 1 16:48:09 2010 -0700
drm: add per-event vblank event trace points
which doesn't give a special justification for using pid over a pointer.
Also note that the nouveau code setting it is entirely pointless:
Since this isn't a vblank event, it will never hit the vblank
tracepoints.
Cc: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-11-daniel.vetter@ffwll.ch
I'm torn on whether drm_minor really should be here or somewhere else.
Maybe with more clarity after untangling drmP.h more this is easier to
decide, for now I've put a FIXME comment right next to it. Right now
we need struct drm_minor for the inline drm_file type helpers, and so
it does kinda make sense to have them here.
Next patch will kerneldoc-ify the entire pile.
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-10-daniel.vetter@ffwll.ch
