This corresponds to the NT syscall NtQuerySemaphore().

This returns the current count and maximum count of the semaphore.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
 drivers/misc/ntsync.c       | 26 ++++++++++++++++++++++++++
 include/uapi/linux/ntsync.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 6b8352270874..d6e8a4bde1d0 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -583,6 +583,30 @@ static int ntsync_event_reset(struct ntsync_obj *event, void __user *argp)
 	return 0;
 }
 
+static int ntsync_sem_read(struct ntsync_obj *sem, void __user *argp)
+{
+	struct ntsync_sem_args __user *user_args = argp;
+	struct ntsync_device *dev = sem->dev;
+	struct ntsync_sem_args args;
+	bool all;
+
+	if (sem->type != NTSYNC_TYPE_SEM)
+		return -EINVAL;
+
+	args.sem = 0;
+
+	all = ntsync_lock_obj(dev, sem);
+
+	args.count = sem->u.sem.count;
+	args.max = sem->u.sem.max;
+
+	ntsync_unlock_obj(dev, sem, all);
+
+	if (copy_to_user(user_args, &args, sizeof(args)))
+		return -EFAULT;
+	return 0;
+}
+
 static int ntsync_obj_release(struct inode *inode, struct file *file)
 {
 	struct ntsync_obj *obj = file->private_data;
@@ -602,6 +626,8 @@ static long ntsync_obj_ioctl(struct file *file, unsigned int cmd,
 	switch (cmd) {
 	case NTSYNC_IOC_SEM_POST:
 		return ntsync_sem_post(obj, argp);
+	case NTSYNC_IOC_SEM_READ:
+		return ntsync_sem_read(obj, argp);
 	case NTSYNC_IOC_MUTEX_UNLOCK:
 		return ntsync_mutex_unlock(obj, argp);
 	case NTSYNC_IOC_MUTEX_KILL:
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index 5586fadd9bdd..5e922703686f 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -54,5 +54,6 @@ struct ntsync_wait_args {
 #define NTSYNC_IOC_EVENT_SET		_IOR ('N', 0x88, __u32)
 #define NTSYNC_IOC_EVENT_RESET		_IOR ('N', 0x89, __u32)
 #define NTSYNC_IOC_EVENT_PULSE		_IOR ('N', 0x8a, __u32)
+#define NTSYNC_IOC_SEM_READ		_IOR ('N', 0x8b, struct ntsync_sem_args)
 
 #endif
-- 
2.45.2