On Thursday, 15 February 2024 01:28:32 CST Greg Kroah-Hartman wrote:

On Wed, Feb 14, 2024 at 05:36:38PM -0600, Elizabeth Figura wrote:

quoted

This corresponds to the NT syscall NtCreateSemaphore().

Semaphores are one of three types of object to be implemented in this driver,
the others being mutexes and events.

An NT semaphore contains a 32-bit counter, and is signaled and can be acquired
when the counter is nonzero. The counter has a maximum value which is specified
at creation time. The initial value of the semaphore is also specified at
creation time. There are no restrictions on the maximum and initial value.

Each object is exposed as an file, to which any number of fds may be opened.
When all fds are closed, the object is deleted.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
 .../userspace-api/ioctl/ioctl-number.rst      |   2 +
 drivers/misc/ntsync.c                         | 120 ++++++++++++++++++
 include/uapi/linux/ntsync.h                   |  21 +++
 3 files changed, 143 insertions(+)
 create mode 100644 include/uapi/linux/ntsync.h

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 457e16f06e04..2f5c6994f042 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -173,6 +173,8 @@ Code  Seq#    Include File                                           Comments
 'M'   00-0F  drivers/video/fsl-diu-fb.h                              conflict!
 'N'   00-1F  drivers/usb/scanner.h
 'N'   40-7F  drivers/block/nvme.c
+'N'   80-8F  uapi/linux/ntsync.h                                     NT synchronization primitives
+                                                                     <mailto:wine-devel@winehq.org>
 'O'   00-06  mtd/ubi-user.h                                          UBI
 'P'   all    linux/soundcard.h                                       conflict!
 'P'   60-6F  sound/sscape_ioctl.h                                    conflict!

diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index e4969ef90722..3ad86d98b82d 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c

@@ -5,26 +5,146 @@
  * Copyright (C) 2024 Elizabeth Figura
  */
 
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/miscdevice.h>
 #include <linux/module.h>
+#include <linux/slab.h>
+#include <uapi/linux/ntsync.h>
 
 #define NTSYNC_NAME	"ntsync"
 
+enum ntsync_type {
+	NTSYNC_TYPE_SEM,
+};
+
+struct ntsync_obj {
+	enum ntsync_type type;
+
+	union {
+		struct {
+			__u32 count;
+			__u32 max;
+		} sem;
+	} u;
+
+	struct file *file;
+	struct ntsync_device *dev;
+};
+
+struct ntsync_device {
+	struct file *file;
+};

No reference counting is needed for your ntsync_device?  Or are you
relying on the reference counting of struct file here?

You pass around pointers to this structure, and save it off into other
structures, how do you know it is "safe" to do so?

Yes, this relies on the reference counting of struct file. The sync
objects (semaphore etc.) grab a reference when they're created, via
get_file(), and release it when they're destroyed. This reference is
taken from within ioctls on the ntsync_device, so the file must be
valid when we grab a reference. Maybe I'm missing something, though?