ntsync: Introduce NTSYNC_IOC_MUTEX_READ.

This corresponds to the NT syscall NtQueryMutant().

This returns the recursion count, owner, and abandoned state of the mutex.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
Signed-off-by: Alexandre Frade <kernel@xanmod.org>

drivers/misc/ntsync.c

@@ -547,6 +547,27 @@ static int ntsync_sem_read(struct ntsync_obj *sem, void __user *argp)
 	return 0;
 }
 
+static int ntsync_mutex_read(struct ntsync_obj *mutex, void __user *argp)
+{
+	struct ntsync_mutex_args __user *user_args = argp;
+	struct ntsync_mutex_args args;
+	int ret;
+
+	if (mutex->type != NTSYNC_TYPE_MUTEX)
+		return -EINVAL;
+
+	args.mutex = 0;
+	spin_lock(&mutex->lock);
+	args.count = mutex->u.mutex.count;
+	args.owner = mutex->u.mutex.owner;
+	ret = mutex->u.mutex.ownerdead ? -EOWNERDEAD : 0;
+	spin_unlock(&mutex->lock);
+
+	if (copy_to_user(user_args, &args, sizeof(args)))
+		return -EFAULT;
+	return ret;
+}
+
 static int ntsync_obj_release(struct inode *inode, struct file *file)
 {
 	struct ntsync_obj *obj = file->private_data;
@@ -572,6 +593,8 @@ static long ntsync_obj_ioctl(struct file *file, unsigned int cmd,
 		return ntsync_mutex_unlock(obj, argp);
 	case NTSYNC_IOC_MUTEX_KILL:
 		return ntsync_mutex_kill(obj, argp);
+	case NTSYNC_IOC_MUTEX_READ:
+		return ntsync_mutex_read(obj, argp);
 	case NTSYNC_IOC_EVENT_SET:
 		return ntsync_event_set(obj, argp, false);
 	case NTSYNC_IOC_EVENT_RESET:

include/uapi/linux/ntsync.h

@@ -52,5 +52,6 @@ struct ntsync_wait_args {
 #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)
+#define NTSYNC_IOC_MUTEX_READ		_IOR ('N', 0x8c, struct ntsync_mutex_args)
 
 #endif