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Kernel+Userland: Add ioctl to set process ownership of DisplayConnector

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Now that the infrastructure of the Graphics subsystem is quite stable,
it is time to try to fix a long-standing problem, which is the lack of
locking on display connector devices. Reading and writing from multiple
processes to a framebuffer controlled by the display connector is not a
huge problem - it could be solved with POSIX locking.

The real problem is some program that will try to do ioctl operations on
a display connector without the WindowServer being aware of that which
can lead to very bad situations, for example - assuming a framebuffer is
encoded at a known resolution and certain display timings, but another
process changed the ModeSetting of the display connector, leading to
inconsistency on the properties of the current ModeSetting.

To solve this, there's a new "master" ioctl to take "ownership" and
another one to release that ownership of a display connector device. To
ensure we will not hold a Process object forever just because it has an
ownership over a display connector, we hold it with a weak reference,
and if the process is gone, someone else can take an ownership.
This commit is contained in:
Liav A 2022-06-10 14:16:28 +03:00 • committed by Linus Groh
parent 1968aba69b
commit 977aa81310
5 changed files with 101 additions and 8 deletions
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4
Userland/Libraries/LibC/sys/ioctl_numbers.h
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@ -101,6 +101,8 @@ enum IOCtlNumber {
GRAPHICS_IOCTL_SET_HEAD_MODE_SETTING,
GRAPHICS_IOCTL_GET_HEAD_MODE_SETTING,
GRAPHICS_IOCTL_SET_SAFE_HEAD_MODE_SETTING,
GRAPHICS_IOCTL_SET_RESPONSIBLE,
GRAPHICS_IOCTL_UNSET_RESPONSIBLE,
KEYBOARD_IOCTL_GET_NUM_LOCK,
KEYBOARD_IOCTL_SET_NUM_LOCK,
KEYBOARD_IOCTL_GET_CAPS_LOCK,
@ -160,6 +162,8 @@ enum IOCtlNumber {
#define GRAPHICS_IOCTL_SET_HEAD_MODE_SETTING GRAPHICS_IOCTL_SET_HEAD_MODE_SETTING
#define GRAPHICS_IOCTL_GET_HEAD_MODE_SETTING GRAPHICS_IOCTL_GET_HEAD_MODE_SETTING
#define GRAPHICS_IOCTL_SET_SAFE_HEAD_MODE_SETTING GRAPHICS_IOCTL_SET_SAFE_HEAD_MODE_SETTING
#define GRAPHICS_IOCTL_SET_RESPONSIBLE GRAPHICS_IOCTL_SET_RESPONSIBLE
#define GRAPHICS_IOCTL_UNSET_RESPONSIBLE GRAPHICS_IOCTL_UNSET_RESPONSIBLE
#define KEYBOARD_IOCTL_GET_NUM_LOCK KEYBOARD_IOCTL_GET_NUM_LOCK
#define KEYBOARD_IOCTL_SET_NUM_LOCK KEYBOARD_IOCTL_SET_NUM_LOCK
#define KEYBOARD_IOCTL_GET_CAPS_LOCK KEYBOARD_IOCTL_GET_CAPS_LOCK