This corresponds to the NT syscall NtCreateMutant().
An NT mutex is recursive, with a 32-bit recursion counter. When acquired via NtWaitForMultipleObjects(), the recursion counter is incremented by one.
The OS records the thread which acquired it. However, in order to keep this driver self-contained, the owning thread ID is managed by user-space, and passed as a parameter to all relevant ioctls.
The initial owner and recursion count, if any, are specified when the mutex is created.
Signed-off-by: Elizabeth Figura zfigura@codeweavers.com --- drivers/misc/ntsync.c | 68 +++++++++++++++++++++++++++++++++++++ include/uapi/linux/ntsync.h | 7 ++++ 2 files changed, 75 insertions(+)
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c index e914d626465a..173513aeeacc 100644 --- a/drivers/misc/ntsync.c +++ b/drivers/misc/ntsync.c @@ -24,6 +24,7 @@
enum ntsync_type { NTSYNC_TYPE_SEM, + NTSYNC_TYPE_MUTEX, };
/* @@ -53,6 +54,10 @@ struct ntsync_obj { __u32 count; __u32 max; } sem; + struct { + __u32 count; + __u32 owner; + } mutex; } u;
/* @@ -132,6 +137,10 @@ static bool is_signaled(struct ntsync_obj *obj, __u32 owner) switch (obj->type) { case NTSYNC_TYPE_SEM: return !!obj->u.sem.count; + case NTSYNC_TYPE_MUTEX: + if (obj->u.mutex.owner && obj->u.mutex.owner != owner) + return false; + return obj->u.mutex.count < UINT_MAX; }
WARN(1, "bad object type %#x\n", obj->type); @@ -175,6 +184,10 @@ static void try_wake_all(struct ntsync_device *dev, struct ntsync_q *q, case NTSYNC_TYPE_SEM: obj->u.sem.count--; break; + case NTSYNC_TYPE_MUTEX: + obj->u.mutex.count++; + obj->u.mutex.owner = q->owner; + break; } } wake_up_process(q->task); @@ -217,6 +230,29 @@ static void try_wake_any_sem(struct ntsync_obj *sem) } }
+static void try_wake_any_mutex(struct ntsync_obj *mutex) +{ + struct ntsync_q_entry *entry; + + lockdep_assert_held(&mutex->lock); + + list_for_each_entry(entry, &mutex->any_waiters, node) { + struct ntsync_q *q = entry->q; + int signaled = -1; + + if (mutex->u.mutex.count == UINT_MAX) + break; + if (mutex->u.mutex.owner && mutex->u.mutex.owner != q->owner) + continue; + + if (atomic_try_cmpxchg(&q->signaled, &signaled, entry->index)) { + mutex->u.mutex.count++; + mutex->u.mutex.owner = q->owner; + wake_up_process(q->task); + } + } +} + /* * Actually change the semaphore state, returning -EOVERFLOW if it is made * invalid. @@ -376,6 +412,33 @@ static int ntsync_create_sem(struct ntsync_device *dev, void __user *argp) return put_user(fd, &user_args->sem); }
+static int ntsync_create_mutex(struct ntsync_device *dev, void __user *argp) +{ + struct ntsync_mutex_args __user *user_args = argp; + struct ntsync_mutex_args args; + struct ntsync_obj *mutex; + int fd; + + if (copy_from_user(&args, argp, sizeof(args))) + return -EFAULT; + + if (!args.owner != !args.count) + return -EINVAL; + + mutex = ntsync_alloc_obj(dev, NTSYNC_TYPE_MUTEX); + if (!mutex) + return -ENOMEM; + mutex->u.mutex.count = args.count; + mutex->u.mutex.owner = args.owner; + fd = ntsync_obj_get_fd(mutex); + if (fd < 0) { + kfree(mutex); + return fd; + } + + return put_user(fd, &user_args->mutex); +} + static struct ntsync_obj *get_obj(struct ntsync_device *dev, int fd) { struct file *file = fget(fd); @@ -505,6 +568,9 @@ static void try_wake_any_obj(struct ntsync_obj *obj) case NTSYNC_TYPE_SEM: try_wake_any_sem(obj); break; + case NTSYNC_TYPE_MUTEX: + try_wake_any_mutex(obj); + break; } }
@@ -693,6 +759,8 @@ static long ntsync_char_ioctl(struct file *file, unsigned int cmd, void __user *argp = (void __user *)parm;
switch (cmd) { + case NTSYNC_IOC_CREATE_MUTEX: + return ntsync_create_mutex(dev, argp); case NTSYNC_IOC_CREATE_SEM: return ntsync_create_sem(dev, argp); case NTSYNC_IOC_WAIT_ALL: diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h index 83784d4438a1..cd7841cdba49 100644 --- a/include/uapi/linux/ntsync.h +++ b/include/uapi/linux/ntsync.h @@ -16,6 +16,12 @@ struct ntsync_sem_args { __u32 max; };
+struct ntsync_mutex_args { + __u32 mutex; + __u32 owner; + __u32 count; +}; + #define NTSYNC_WAIT_REALTIME 0x1
struct ntsync_wait_args { @@ -34,6 +40,7 @@ struct ntsync_wait_args { #define NTSYNC_IOC_CREATE_SEM _IOWR('N', 0x80, struct ntsync_sem_args) #define NTSYNC_IOC_WAIT_ANY _IOWR('N', 0x82, struct ntsync_wait_args) #define NTSYNC_IOC_WAIT_ALL _IOWR('N', 0x83, struct ntsync_wait_args) +#define NTSYNC_IOC_CREATE_MUTEX _IOWR('N', 0x84, struct ntsync_sem_args)
#define NTSYNC_IOC_SEM_POST _IOWR('N', 0x81, __u32)