linux/drivers/misc/ntsync.c
Elizabeth Figura dc806bd48a ntsync: Introduce NTSYNC_IOC_SEM_POST.
This corresponds to the NT syscall NtReleaseSemaphore().

This increases the semaphore's internal counter by the given value, and returns
the previous value. If the counter would overflow the defined maximum, the
function instead fails and returns -EOVERFLOW.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
Link: https://lore.kernel.org/r/20240329000621.148791-4-zfigura@codeweavers.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-04-11 15:34:40 +02:00

250 lines
5.0 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* ntsync.c - Kernel driver for NT synchronization primitives
*
* Copyright (C) 2024 Elizabeth Figura <zfigura@codeweavers.com>
*/
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/overflow.h>
#include <linux/slab.h>
#include <linux/spinlock.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 {
spinlock_t lock;
enum ntsync_type type;
struct file *file;
struct ntsync_device *dev;
/* The following fields are protected by the object lock. */
union {
struct {
__u32 count;
__u32 max;
} sem;
} u;
};
struct ntsync_device {
struct file *file;
};
/*
* Actually change the semaphore state, returning -EOVERFLOW if it is made
* invalid.
*/
static int post_sem_state(struct ntsync_obj *sem, __u32 count)
{
__u32 sum;
lockdep_assert_held(&sem->lock);
if (check_add_overflow(sem->u.sem.count, count, &sum) ||
sum > sem->u.sem.max)
return -EOVERFLOW;
sem->u.sem.count = sum;
return 0;
}
static int ntsync_sem_post(struct ntsync_obj *sem, void __user *argp)
{
__u32 __user *user_args = argp;
__u32 prev_count;
__u32 args;
int ret;
if (copy_from_user(&args, argp, sizeof(args)))
return -EFAULT;
if (sem->type != NTSYNC_TYPE_SEM)
return -EINVAL;
spin_lock(&sem->lock);
prev_count = sem->u.sem.count;
ret = post_sem_state(sem, args);
spin_unlock(&sem->lock);
if (!ret && put_user(prev_count, user_args))
ret = -EFAULT;
return ret;
}
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 long ntsync_obj_ioctl(struct file *file, unsigned int cmd,
unsigned long parm)
{
struct ntsync_obj *obj = file->private_data;
void __user *argp = (void __user *)parm;
switch (cmd) {
case NTSYNC_IOC_SEM_POST:
return ntsync_sem_post(obj, argp);
default:
return -ENOIOCTLCMD;
}
}
static const struct file_operations ntsync_obj_fops = {
.owner = THIS_MODULE,
.release = ntsync_obj_release,
.unlocked_ioctl = ntsync_obj_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.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);
spin_lock_init(&obj->lock);
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;
}
}
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 <zfigura@codeweavers.com>");
MODULE_DESCRIPTION("Kernel driver for NT synchronization primitives");
MODULE_LICENSE("GPL");