This patch series introduces a new char misc driver, /dev/ntsync, which is used
to implement Windows NT synchronization primitives.
== Background ==
The Wine project emulates the Windows API in user space. One particular part of
that API, namely the NT synchronization primitives, have historically been
implemented via RPC to a dedicated "kernel" process. However, more recent
applications use these APIs more strenuously, and the overhead of RPC has become
a bottleneck.
The NT synchronization APIs are too complex to implement on top of existing
primitives without sacrificing correctness. Certain operations, such as
NtPulseEvent() or the "wait-for-all" mode of NtWaitForMultipleObjects(), require
direct control over the underlying wait queue, and implementing a wait queue
sufficiently robust for Wine in user space is not possible. This proposed
driver, therefore, implements the problematic interfaces directly in the Linux
kernel.
This driver was presented at Linux Plumbers Conference 2023. For those further
interested in the history of synchronization in Wine and past attempts to solve
this problem in user space, a recording of the presentation can be viewed here:
https://www.youtube.com/watch?v=NjU4nyWyhU8
== Performance ==
The gain in performance varies wildly depending on the application in question
and the user's hardware. For some games NT synchronization is not a bottleneck
and no change can be observed, but for others frame rate improvements of 50 to
150 percent are not atypical. The following table lists frame rate measurements
from a variety of games on a variety of hardware, taken by users Dmitry
Skvortsov, FuzzyQuils, OnMars, and myself:
Game Upstream ntsync improvement
===========================================================================
Anger Foot 69 99 43%
Call of Juarez 99.8 224.1 125%
Dirt 3 110.6 860.7 678%
Forza Horizon 5 108 160 48%
Lara Croft: Temple of Osiris 141 326 131%
Metro 2033 164.4 199.2 21%
Resident Evil 2 26 77 196%
The Crew 26 51 96%
Tiny Tina's Wonderlands 130 360 177%
Total War Saga: Troy 109 146 34%
===========================================================================
== Patches ==
The intended semantics of the patches are broadly intended to match those of the
corresponding Windows functions. For those not already familiar with the Windows
functions (or their undocumented behaviour), patch 31/31 provides a detailed
specification, and individual patches also include a brief description of the
API they are implementing.
The patches making use of this driver in Wine can be retrieved or browsed here:
https://repo.or.cz/wine/zf.git/shortlog/refs/heads/ntsync5
== Implementation ==
Some aspects of the implementation may deserve particular comment:
* In the interest of performance, each object is governed only by a single
spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
objects be changed as a single atomic operation. In order to achieve this, we
first take a device-wide lock ("wait_all_lock") any time we are going to lock
more than one object at a time.
The maximum number of objects that can be used in a vectored wait, and
therefore the maximum that can be locked simultaneously, is 64. This number is
NT's own limit.
The acquisition of multiple spinlocks will degrade performance. This is a
conscious choice, however. Wait-for-all is known to be a very rare operation
in practice, especially with counts that approach the maximum, and it is the
intent of the ntsync driver to optimize wait-for-any at the expense of
wait-for-all as much as possible.
* NT mutexes are tied to their threads on an OS level, and the kernel includes
builtin support for "robust" mutexes. In order to keep the ntsync driver
self-contained and avoid touching more code than necessary, it does not hook
into task exit nor use pids.
Instead, the user space emulator is expected to manage thread IDs and pass
them as an argument to any relevant functions; this is the "owner" field of
ntsync_wait_args and ntsync_mutex_args.
When the emulator detects that a thread dies, it should therefore call
NTSYNC_IOC_MUTEX_KILL on any open mutexes.
* ntsync is module-capable mostly because there was nothing preventing it, and
because it aided development. It is not a hard requirement, though.
== Previous versions ==
Changes from v2:
* Check the result of fget() for NULL.
* Squash patch 31 (introducing the NTSYNC_WAIT_REALTIME flag) into patch 4, per
Arnd Bergmann.
* Use atomic_try_cmpxchg() instead of atomic_cmpxchg(), per off-list review from
Uros Bizjak.
* Link to v2: https://lore.kernel.org/lkml/[email protected]/
* Link to v1: https://lore.kernel.org/lkml/[email protected]/
* Link to RFC v2: https://lore.kernel.org/lkml/[email protected]/
* Link to RFC v1: https://lore.kernel.org/lkml/[email protected]/
Elizabeth Figura (30):
ntsync: Introduce the ntsync driver and character device.
ntsync: Introduce NTSYNC_IOC_CREATE_SEM.
ntsync: Introduce NTSYNC_IOC_SEM_POST.
ntsync: Introduce NTSYNC_IOC_WAIT_ANY.
ntsync: Introduce NTSYNC_IOC_WAIT_ALL.
ntsync: Introduce NTSYNC_IOC_CREATE_MUTEX.
ntsync: Introduce NTSYNC_IOC_MUTEX_UNLOCK.
ntsync: Introduce NTSYNC_IOC_MUTEX_KILL.
ntsync: Introduce NTSYNC_IOC_CREATE_EVENT.
ntsync: Introduce NTSYNC_IOC_EVENT_SET.
ntsync: Introduce NTSYNC_IOC_EVENT_RESET.
ntsync: Introduce NTSYNC_IOC_EVENT_PULSE.
ntsync: Introduce NTSYNC_IOC_SEM_READ.
ntsync: Introduce NTSYNC_IOC_MUTEX_READ.
ntsync: Introduce NTSYNC_IOC_EVENT_READ.
ntsync: Introduce alertable waits.
selftests: ntsync: Add some tests for semaphore state.
selftests: ntsync: Add some tests for mutex state.
selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ANY.
selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ALL.
selftests: ntsync: Add some tests for wakeup signaling with
WINESYNC_IOC_WAIT_ANY.
selftests: ntsync: Add some tests for wakeup signaling with
WINESYNC_IOC_WAIT_ALL.
selftests: ntsync: Add some tests for manual-reset event state.
selftests: ntsync: Add some tests for auto-reset event state.
selftests: ntsync: Add some tests for wakeup signaling with events.
selftests: ntsync: Add tests for alertable waits.
selftests: ntsync: Add some tests for wakeup signaling via alerts.
selftests: ntsync: Add a stress test for contended waits.
maintainers: Add an entry for ntsync.
docs: ntsync: Add documentation for the ntsync uAPI.
Documentation/userspace-api/index.rst | 1 +
.../userspace-api/ioctl/ioctl-number.rst | 2 +
Documentation/userspace-api/ntsync.rst | 399 +++++
MAINTAINERS | 9 +
drivers/misc/Kconfig | 11 +
drivers/misc/Makefile | 1 +
drivers/misc/ntsync.c | 1166 ++++++++++++++
include/uapi/linux/ntsync.h | 62 +
tools/testing/selftests/Makefile | 1 +
.../testing/selftests/drivers/ntsync/Makefile | 8 +
tools/testing/selftests/drivers/ntsync/config | 1 +
.../testing/selftests/drivers/ntsync/ntsync.c | 1407 +++++++++++++++++
12 files changed, 3068 insertions(+)
create mode 100644 Documentation/userspace-api/ntsync.rst
create mode 100644 drivers/misc/ntsync.c
create mode 100644 include/uapi/linux/ntsync.h
create mode 100644 tools/testing/selftests/drivers/ntsync/Makefile
create mode 100644 tools/testing/selftests/drivers/ntsync/config
create mode 100644 tools/testing/selftests/drivers/ntsync/ntsync.c
base-commit: 4cece764965020c22cff7665b18a012006359095
--
2.43.0
This corresponds to the NT syscall NtQueryMutant().
This returns the recursion count, owner, and abandoned state of the mutex.
Signed-off-by: Elizabeth Figura <[email protected]>
---
drivers/misc/ntsync.c | 23 +++++++++++++++++++++++
include/uapi/linux/ntsync.h | 1 +
2 files changed, 24 insertions(+)
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 961e8d241602..bd043dccc9fa 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -551,6 +551,27 @@ 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;
@@ -576,6 +597,8 @@ 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:
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index e298400bf25a..797e8df10a3a 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -56,5 +56,6 @@ 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
--
2.43.0
NT waits can optionally be made "alertable". This is a special channel for
thread wakeup that is mildly similar to SIGIO. A thread has an internal single
bit of "alerted" state, and if a thread is alerted while an alertable wait, the
wait will return a special value, consume the "alerted" state, and will not
consume any of its objects.
Alerts are implemented using events; the user-space NT emulator is expected to
create an internal ntsync event for each thread and pass that event to wait
functions.
Signed-off-by: Elizabeth Figura <[email protected]>
---
drivers/misc/ntsync.c | 68 ++++++++++++++++++++++++++++++++-----
include/uapi/linux/ntsync.h | 2 +-
2 files changed, 60 insertions(+), 10 deletions(-)
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index a03c6fceb518..19fd70ac3f50 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -819,25 +819,32 @@ static int setup_wait(struct ntsync_device *dev,
const struct ntsync_wait_args *args, bool all,
struct ntsync_q **ret_q)
{
+ int fds[NTSYNC_MAX_WAIT_COUNT + 1];
const __u32 count = args->count;
- int fds[NTSYNC_MAX_WAIT_COUNT];
struct ntsync_q *q;
+ __u32 total_count;
__u32 i, j;
if (!args->owner)
return -EINVAL;
- if (args->pad || args->pad2 || (args->flags & ~NTSYNC_WAIT_REALTIME))
+ if (args->pad || (args->flags & ~NTSYNC_WAIT_REALTIME))
return -EINVAL;
if (args->count > NTSYNC_MAX_WAIT_COUNT)
return -EINVAL;
+ total_count = count;
+ if (args->alert)
+ total_count++;
+
if (copy_from_user(fds, u64_to_user_ptr(args->objs),
array_size(count, sizeof(*fds))))
return -EFAULT;
+ if (args->alert)
+ fds[count] = args->alert;
- q = kmalloc(struct_size(q, entries, count), GFP_KERNEL);
+ q = kmalloc(struct_size(q, entries, total_count), GFP_KERNEL);
if (!q)
return -ENOMEM;
q->task = current;
@@ -847,7 +854,7 @@ static int setup_wait(struct ntsync_device *dev,
q->ownerdead = false;
q->count = count;
- for (i = 0; i < count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = get_obj(dev, fds[i]);
@@ -897,9 +904,9 @@ static void try_wake_any_obj(struct ntsync_obj *obj)
static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
{
struct ntsync_wait_args args;
+ __u32 i, total_count;
struct ntsync_q *q;
int signaled;
- __u32 i;
int ret;
if (copy_from_user(&args, argp, sizeof(args)))
@@ -909,9 +916,13 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
if (ret < 0)
return ret;
+ total_count = args.count;
+ if (args.alert)
+ total_count++;
+
/* queue ourselves */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = entry->obj;
@@ -920,9 +931,15 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
spin_unlock(&obj->lock);
}
- /* check if we are already signaled */
+ /*
+ * Check if we are already signaled.
+ *
+ * Note that the API requires that normal objects are checked before
+ * the alert event. Hence we queue the alert event last, and check
+ * objects in order.
+ */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_obj *obj = q->entries[i].obj;
if (atomic_read(&q->signaled) != -1)
@@ -939,7 +956,7 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
/* and finally, unqueue */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = entry->obj;
@@ -999,6 +1016,14 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
*/
list_add_tail(&entry->node, &obj->all_waiters);
}
+ if (args.alert) {
+ struct ntsync_q_entry *entry = &q->entries[args.count];
+ struct ntsync_obj *obj = entry->obj;
+
+ spin_lock_nest_lock(&obj->lock, &dev->wait_all_lock);
+ list_add_tail(&entry->node, &obj->any_waiters);
+ spin_unlock(&obj->lock);
+ }
/* check if we are already signaled */
@@ -1006,6 +1031,21 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
spin_unlock(&dev->wait_all_lock);
+ /*
+ * Check if the alert event is signaled, making sure to do so only
+ * after checking if the other objects are signaled.
+ */
+
+ if (args.alert) {
+ struct ntsync_obj *obj = q->entries[args.count].obj;
+
+ if (atomic_read(&q->signaled) == -1) {
+ spin_lock(&obj->lock);
+ try_wake_any_obj(obj);
+ spin_unlock(&obj->lock);
+ }
+ }
+
/* sleep */
ret = ntsync_schedule(q, &args);
@@ -1028,6 +1068,16 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
put_obj(obj);
}
+ if (args.alert) {
+ struct ntsync_q_entry *entry = &q->entries[args.count];
+ struct ntsync_obj *obj = entry->obj;
+
+ spin_lock_nest_lock(&obj->lock, &dev->wait_all_lock);
+ list_del(&entry->node);
+ spin_unlock(&obj->lock);
+
+ put_obj(obj);
+ }
spin_unlock(&dev->wait_all_lock);
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index 80f36de46a75..f21dbac42164 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -37,8 +37,8 @@ struct ntsync_wait_args {
__u32 owner;
__u32 index;
__u32 flags;
+ __u32 alert;
__u32 pad;
- __u32 pad2;
};
#define NTSYNC_MAX_WAIT_COUNT 64
--
2.43.0
ntsync uses a misc device as the simplest and least intrusive uAPI interface.
Each file description on the device represents an isolated NT instance, intended
to correspond to a single NT virtual machine.
Signed-off-by: Elizabeth Figura <[email protected]>
---
drivers/misc/Kconfig | 11 +++++++++
drivers/misc/Makefile | 1 +
drivers/misc/ntsync.c | 52 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+)
create mode 100644 drivers/misc/ntsync.c
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 4fb291f0bf7c..801ed229ed7d 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -506,6 +506,17 @@ config OPEN_DICE
If unsure, say N.
+config NTSYNC
+ tristate "NT synchronization primitive emulation"
+ help
+ This module provides kernel support for emulation of Windows NT
+ synchronization primitives. It is not a hardware driver.
+
+ To compile this driver as a module, choose M here: the
+ module will be called ntsync.
+
+ If unsure, say N.
+
config VCPU_STALL_DETECTOR
tristate "Guest vCPU stall detector"
depends on OF && HAS_IOMEM
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index ea6ea5bbbc9c..153a3f4837e8 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_PVPANIC) += pvpanic/
obj-$(CONFIG_UACCE) += uacce/
obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
obj-$(CONFIG_HISI_HIKEY_USB) += hisi_hikey_usb.o
+obj-$(CONFIG_NTSYNC) += ntsync.o
obj-$(CONFIG_HI6421V600_IRQ) += hi6421v600-irq.o
obj-$(CONFIG_OPEN_DICE) += open-dice.o
obj-$(CONFIG_GP_PCI1XXXX) += mchp_pci1xxxx/
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
new file mode 100644
index 000000000000..bd76e653d83e
--- /dev/null
+++ b/drivers/misc/ntsync.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ntsync.c - Kernel driver for NT synchronization primitives
+ *
+ * Copyright (C) 2024 Elizabeth Figura <[email protected]>
+ */
+
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+
+#define NTSYNC_NAME "ntsync"
+
+static int ntsync_char_open(struct inode *inode, struct file *file)
+{
+ return nonseekable_open(inode, file);
+}
+
+static int ntsync_char_release(struct inode *inode, struct file *file)
+{
+ return 0;
+}
+
+static long ntsync_char_ioctl(struct file *file, unsigned int cmd,
+ unsigned long parm)
+{
+ switch (cmd) {
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
+static const struct file_operations ntsync_fops = {
+ .owner = THIS_MODULE,
+ .open = ntsync_char_open,
+ .release = ntsync_char_release,
+ .unlocked_ioctl = ntsync_char_ioctl,
+ .compat_ioctl = compat_ptr_ioctl,
+ .llseek = no_llseek,
+};
+
+static struct miscdevice ntsync_misc = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = NTSYNC_NAME,
+ .fops = &ntsync_fops,
+};
+
+module_misc_device(ntsync_misc);
+
+MODULE_AUTHOR("Elizabeth Figura <[email protected]>");
+MODULE_DESCRIPTION("Kernel driver for NT synchronization primitives");
+MODULE_LICENSE("GPL");
--
2.43.0
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.
Objects hold a pointer to the ntsync_device that created them. The device's
reference count is driven by struct file.
Signed-off-by: Elizabeth Figura <[email protected]>
---
.../userspace-api/ioctl/ioctl-number.rst | 2 +
drivers/misc/ntsync.c | 131 ++++++++++++++++++
include/uapi/linux/ntsync.h | 21 +++
3 files changed, 154 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 c472423412bf..a141e8e65c5d 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -174,6 +174,8 @@ 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:[email protected]>
'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 bd76e653d83e..20158ec148bc 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -5,26 +5,157 @@
* Copyright (C) 2024 Elizabeth Figura <[email protected]>
*/
+#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,
+};
+
+/*
+ * Individual synchronization primitives are represented by
+ * struct ntsync_obj, and each primitive is backed by a file.
+ *
+ * The whole namespace is represented by a struct ntsync_device also
+ * backed by a file.
+ *
+ * Both rely on struct file for reference counting. Individual
+ * ntsync_obj objects take a reference to the device when created.
+ */
+
+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;
+};
+
+static int ntsync_obj_release(struct inode *inode, struct file *file)
+{
+ struct ntsync_obj *obj = file->private_data;
+
+ fput(obj->dev->file);
+ kfree(obj);
+
+ return 0;
+}
+
+static const struct file_operations ntsync_obj_fops = {
+ .owner = THIS_MODULE,
+ .release = ntsync_obj_release,
+ .llseek = no_llseek,
+};
+
+static struct ntsync_obj *ntsync_alloc_obj(struct ntsync_device *dev,
+ enum ntsync_type type)
+{
+ struct ntsync_obj *obj;
+
+ obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+ if (!obj)
+ return NULL;
+ obj->type = type;
+ obj->dev = dev;
+ get_file(dev->file);
+
+ return obj;
+}
+
+static int ntsync_obj_get_fd(struct ntsync_obj *obj)
+{
+ struct file *file;
+ int fd;
+
+ fd = get_unused_fd_flags(O_CLOEXEC);
+ if (fd < 0)
+ return fd;
+ file = anon_inode_getfile("ntsync", &ntsync_obj_fops, obj, O_RDWR);
+ if (IS_ERR(file)) {
+ put_unused_fd(fd);
+ return PTR_ERR(file);
+ }
+ obj->file = file;
+ fd_install(fd, file);
+
+ return fd;
+}
+
+static int ntsync_create_sem(struct ntsync_device *dev, void __user *argp)
+{
+ struct ntsync_sem_args __user *user_args = argp;
+ struct ntsync_sem_args args;
+ struct ntsync_obj *sem;
+ int fd;
+
+ if (copy_from_user(&args, argp, sizeof(args)))
+ return -EFAULT;
+
+ if (args.count > args.max)
+ return -EINVAL;
+
+ sem = ntsync_alloc_obj(dev, NTSYNC_TYPE_SEM);
+ if (!sem)
+ return -ENOMEM;
+ sem->u.sem.count = args.count;
+ sem->u.sem.max = args.max;
+ fd = ntsync_obj_get_fd(sem);
+ if (fd < 0) {
+ kfree(sem);
+ return fd;
+ }
+
+ return put_user(fd, &user_args->sem);
+}
+
static int ntsync_char_open(struct inode *inode, struct file *file)
{
+ struct ntsync_device *dev;
+
+ dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+ if (!dev)
+ return -ENOMEM;
+
+ file->private_data = dev;
+ dev->file = file;
return nonseekable_open(inode, file);
}
static int ntsync_char_release(struct inode *inode, struct file *file)
{
+ struct ntsync_device *dev = file->private_data;
+
+ kfree(dev);
+
return 0;
}
static long ntsync_char_ioctl(struct file *file, unsigned int cmd,
unsigned long parm)
{
+ struct ntsync_device *dev = file->private_data;
+ void __user *argp = (void __user *)parm;
+
switch (cmd) {
+ case NTSYNC_IOC_CREATE_SEM:
+ return ntsync_create_sem(dev, argp);
default:
return -ENOIOCTLCMD;
}
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
new file mode 100644
index 000000000000..6a4867a6c97b
--- /dev/null
+++ b/include/uapi/linux/ntsync.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Kernel support for NT synchronization primitive emulation
+ *
+ * Copyright (C) 2021-2022 Elizabeth Figura <[email protected]>
+ */
+
+#ifndef __LINUX_NTSYNC_H
+#define __LINUX_NTSYNC_H
+
+#include <linux/types.h>
+
+struct ntsync_sem_args {
+ __u32 sem;
+ __u32 count;
+ __u32 max;
+};
+
+#define NTSYNC_IOC_CREATE_SEM _IOWR('N', 0x80, struct ntsync_sem_args)
+
+#endif
--
2.43.0