--- /dev/null
+/*
+ * CUSE: Character device in Userspace
+ *
+ * Copyright (C) 2008-2009 SUSE Linux Products GmbH
+ * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ * CUSE enables character devices to be implemented from userland much
+ * like FUSE allows filesystems. On initialization /dev/cuse is
+ * created. By opening the file and replying to the CUSE_INIT request
+ * userland CUSE server can create a character device. After that the
+ * operation is very similar to FUSE.
+ *
+ * A CUSE instance involves the following objects.
+ *
+ * cuse_conn : contains fuse_conn and serves as bonding structure
+ * channel : file handle connected to the userland CUSE server
+ * cdev : the implemented character device
+ * dev : generic device for cdev
+ *
+ * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with
+ * devices, it's called 'channel' to reduce confusion.
+ *
+ * channel determines when the character device dies. When channel is
+ * closed, everything begins to destruct. The cuse_conn is taken off
+ * the lookup table preventing further access from cdev, cdev and
+ * generic device are removed and the base reference of cuse_conn is
+ * put.
+ *
+ * On each open, the matching cuse_conn is looked up and if found an
+ * additional reference is taken which is released when the file is
+ * closed.
+ */
+
+#include <linux/fuse.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kdev_t.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/magic.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+#include <linux/module.h>
+#include <linux/uio.h>
+
+#include "fuse_i.h"
+
+#define CUSE_CONNTBL_LEN 64
+
+struct cuse_conn {
+ struct list_head list; /* linked on cuse_conntbl */
+ struct fuse_conn fc; /* fuse connection */
+ struct cdev *cdev; /* associated character device */
+ struct device *dev; /* device representing @cdev */
+
+ /* init parameters, set once during initialization */
+ bool unrestricted_ioctl;
+};
+
+static DEFINE_MUTEX(cuse_lock); /* protects registration */
+static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
+static struct class *cuse_class;
+
+static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
+{
+ return container_of(fc, struct cuse_conn, fc);
+}
+
+static struct list_head *cuse_conntbl_head(dev_t devt)
+{
+ return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
+}
+
+
+/**************************************************************************
+ * CUSE frontend operations
+ *
+ * These are file operations for the character device.
+ *
+ * On open, CUSE opens a file from the FUSE mnt and stores it to
+ * private_data of the open file. All other ops call FUSE ops on the
+ * FUSE file.
+ */
+
+static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
+{
+ struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
+ loff_t pos = 0;
+
+ return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE);
+}
+
+static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from)
+{
+ struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
+ loff_t pos = 0;
+ /*
+ * No locking or generic_write_checks(), the server is
+ * responsible for locking and sanity checks.
+ */
+ return fuse_direct_io(&io, from, &pos,
+ FUSE_DIO_WRITE | FUSE_DIO_CUSE);
+}
+
+static int cuse_open(struct inode *inode, struct file *file)
+{
+ dev_t devt = inode->i_cdev->dev;
+ struct cuse_conn *cc = NULL, *pos;
+ int rc;
+
+ /* look up and get the connection */
+ mutex_lock(&cuse_lock);
+ list_for_each_entry(pos, cuse_conntbl_head(devt), list)
+ if (pos->dev->devt == devt) {
+ fuse_conn_get(&pos->fc);
+ cc = pos;
+ break;
+ }
+ mutex_unlock(&cuse_lock);
+
+ /* dead? */
+ if (!cc)
+ return -ENODEV;
+
+ /*
+ * Generic permission check is already done against the chrdev
+ * file, proceed to open.
+ */
+ rc = fuse_do_open(&cc->fc, 0, file, 0);
+ if (rc)
+ fuse_conn_put(&cc->fc);
+ return rc;
+}
+
+static int cuse_release(struct inode *inode, struct file *file)
+{
+ struct fuse_file *ff = file->private_data;
+ struct fuse_conn *fc = ff->fc;
+
+ fuse_sync_release(ff, file->f_flags);
+ fuse_conn_put(fc);
+
+ return 0;
+}
+
+static long cuse_file_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct fuse_file *ff = file->private_data;
+ struct cuse_conn *cc = fc_to_cc(ff->fc);
+ unsigned int flags = 0;
+
+ if (cc->unrestricted_ioctl)
+ flags |= FUSE_IOCTL_UNRESTRICTED;
+
+ return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct fuse_file *ff = file->private_data;
+ struct cuse_conn *cc = fc_to_cc(ff->fc);
+ unsigned int flags = FUSE_IOCTL_COMPAT;
+
+ if (cc->unrestricted_ioctl)
+ flags |= FUSE_IOCTL_UNRESTRICTED;
+
+ return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static const struct file_operations cuse_frontend_fops = {
+ .owner = THIS_MODULE,
+ .read_iter = cuse_read_iter,
+ .write_iter = cuse_write_iter,
+ .open = cuse_open,
+ .release = cuse_release,
+ .unlocked_ioctl = cuse_file_ioctl,
+ .compat_ioctl = cuse_file_compat_ioctl,
+ .poll = fuse_file_poll,
+ .llseek = noop_llseek,
+};
+
+
+/**************************************************************************
+ * CUSE channel initialization and destruction
+ */
+
+struct cuse_devinfo {
+ const char *name;
+};
+
+/**
+ * cuse_parse_one - parse one key=value pair
+ * @pp: i/o parameter for the current position
+ * @end: points to one past the end of the packed string
+ * @keyp: out parameter for key
+ * @valp: out parameter for value
+ *
+ * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
+ * at @end - 1. This function parses one pair and set *@keyp to the
+ * start of the key and *@valp to the start of the value. Note that
+ * the original string is modified such that the key string is
+ * terminated with '\0'. *@pp is updated to point to the next string.
+ *
+ * RETURNS:
+ * 1 on successful parse, 0 on EOF, -errno on failure.
+ */
+static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
+{
+ char *p = *pp;
+ char *key, *val;
+
+ while (p < end && *p == '\0')
+ p++;
+ if (p == end)
+ return 0;
+
+ if (end[-1] != '\0') {
+ printk(KERN_ERR "CUSE: info not properly terminated\n");
+ return -EINVAL;
+ }
+
+ key = val = p;
+ p += strlen(p);
+
+ if (valp) {
+ strsep(&val, "=");
+ if (!val)
+ val = key + strlen(key);
+ key = strstrip(key);
+ val = strstrip(val);
+ } else
+ key = strstrip(key);
+
+ if (!strlen(key)) {
+ printk(KERN_ERR "CUSE: zero length info key specified\n");
+ return -EINVAL;
+ }
+
+ *pp = p;
+ *keyp = key;
+ if (valp)
+ *valp = val;
+
+ return 1;
+}
+
+/**
+ * cuse_parse_dev_info - parse device info
+ * @p: device info string
+ * @len: length of device info string
+ * @devinfo: out parameter for parsed device info
+ *
+ * Parse @p to extract device info and store it into @devinfo. String
+ * pointed to by @p is modified by parsing and @devinfo points into
+ * them, so @p shouldn't be freed while @devinfo is in use.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
+{
+ char *end = p + len;
+ char *uninitialized_var(key), *uninitialized_var(val);
+ int rc;
+
+ while (true) {
+ rc = cuse_parse_one(&p, end, &key, &val);
+ if (rc < 0)
+ return rc;
+ if (!rc)
+ break;
+ if (strcmp(key, "DEVNAME") == 0)
+ devinfo->name = val;
+ else
+ printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
+ key);
+ }
+
+ if (!devinfo->name || !strlen(devinfo->name)) {
+ printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static void cuse_gendev_release(struct device *dev)
+{
+ kfree(dev);
+}
+
+/**
+ * cuse_process_init_reply - finish initializing CUSE channel
+ *
+ * This function creates the character device and sets up all the
+ * required data structures for it. Please read the comment at the
+ * top of this file for high level overview.
+ */
+static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
+{
+ struct cuse_conn *cc = fc_to_cc(fc), *pos;
+ struct cuse_init_out *arg = req->out.args[0].value;
+ struct page *page = req->pages[0];
+ struct cuse_devinfo devinfo = { };
+ struct device *dev;
+ struct cdev *cdev;
+ dev_t devt;
+ int rc, i;
+
+ if (req->out.h.error ||
+ arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
+ goto err;
+ }
+
+ fc->minor = arg->minor;
+ fc->max_read = max_t(unsigned, arg->max_read, 4096);
+ fc->max_write = max_t(unsigned, arg->max_write, 4096);
+
+ /* parse init reply */
+ cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
+
+ rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
+ &devinfo);
+ if (rc)
+ goto err;
+
+ /* determine and reserve devt */
+ devt = MKDEV(arg->dev_major, arg->dev_minor);
+ if (!MAJOR(devt))
+ rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
+ else
+ rc = register_chrdev_region(devt, 1, devinfo.name);
+ if (rc) {
+ printk(KERN_ERR "CUSE: failed to register chrdev region\n");
+ goto err;
+ }
+
+ /* devt determined, create device */
+ rc = -ENOMEM;
+ dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+ if (!dev)
+ goto err_region;
+
+ device_initialize(dev);
+ dev_set_uevent_suppress(dev, 1);
+ dev->class = cuse_class;
+ dev->devt = devt;
+ dev->release = cuse_gendev_release;
+ dev_set_drvdata(dev, cc);
+ dev_set_name(dev, "%s", devinfo.name);
+
+ mutex_lock(&cuse_lock);
+
+ /* make sure the device-name is unique */
+ for (i = 0; i < CUSE_CONNTBL_LEN; ++i) {
+ list_for_each_entry(pos, &cuse_conntbl[i], list)
+ if (!strcmp(dev_name(pos->dev), dev_name(dev)))
+ goto err_unlock;
+ }
+
+ rc = device_add(dev);
+ if (rc)
+ goto err_unlock;
+
+ /* register cdev */
+ rc = -ENOMEM;
+ cdev = cdev_alloc();
+ if (!cdev)
+ goto err_unlock;
+
+ cdev->owner = THIS_MODULE;
+ cdev->ops = &cuse_frontend_fops;
+
+ rc = cdev_add(cdev, devt, 1);
+ if (rc)
+ goto err_cdev;
+
+ cc->dev = dev;
+ cc->cdev = cdev;
+
+ /* make the device available */
+ list_add(&cc->list, cuse_conntbl_head(devt));
+ mutex_unlock(&cuse_lock);
+
+ /* announce device availability */
+ dev_set_uevent_suppress(dev, 0);
+ kobject_uevent(&dev->kobj, KOBJ_ADD);
+out:
+ kfree(arg);
+ __free_page(page);
+ return;
+
+err_cdev:
+ cdev_del(cdev);
+err_unlock:
+ mutex_unlock(&cuse_lock);
+ put_device(dev);
+err_region:
+ unregister_chrdev_region(devt, 1);
+err:
+ fuse_abort_conn(fc);
+ goto out;
+}
+
+static int cuse_send_init(struct cuse_conn *cc)
+{
+ int rc;
+ struct fuse_req *req;
+ struct page *page;
+ struct fuse_conn *fc = &cc->fc;
+ struct cuse_init_in *arg;
+ void *outarg;
+
+ BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
+
+ req = fuse_get_req_for_background(fc, 1);
+ if (IS_ERR(req)) {
+ rc = PTR_ERR(req);
+ goto err;
+ }
+
+ rc = -ENOMEM;
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ goto err_put_req;
+
+ outarg = kzalloc(sizeof(struct cuse_init_out), GFP_KERNEL);
+ if (!outarg)
+ goto err_free_page;
+
+ arg = &req->misc.cuse_init_in;
+ arg->major = FUSE_KERNEL_VERSION;
+ arg->minor = FUSE_KERNEL_MINOR_VERSION;
+ arg->flags |= CUSE_UNRESTRICTED_IOCTL;
+ req->in.h.opcode = CUSE_INIT;
+ req->in.numargs = 1;
+ req->in.args[0].size = sizeof(struct cuse_init_in);
+ req->in.args[0].value = arg;
+ req->out.numargs = 2;
+ req->out.args[0].size = sizeof(struct cuse_init_out);
+ req->out.args[0].value = outarg;
+ req->out.args[1].size = CUSE_INIT_INFO_MAX;
+ req->out.argvar = 1;
+ req->out.argpages = 1;
+ req->pages[0] = page;
+ req->page_descs[0].length = req->out.args[1].size;
+ req->num_pages = 1;
+ req->end = cuse_process_init_reply;
+ fuse_request_send_background(fc, req);
+
+ return 0;
+
+err_free_page:
+ __free_page(page);
+err_put_req:
+ fuse_put_request(fc, req);
+err:
+ return rc;
+}
+
+static void cuse_fc_release(struct fuse_conn *fc)
+{
+ struct cuse_conn *cc = fc_to_cc(fc);
+ kfree_rcu(cc, fc.rcu);
+}
+
+/**
+ * cuse_channel_open - open method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being opened
+ *
+ * Userland CUSE server can create a CUSE device by opening /dev/cuse
+ * and replying to the initialization request kernel sends. This
+ * function is responsible for handling CUSE device initialization.
+ * Because the fd opened by this function is used during
+ * initialization, this function only creates cuse_conn and sends
+ * init. The rest is delegated to a kthread.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_open(struct inode *inode, struct file *file)
+{
+ struct cuse_conn *cc;
+ int rc;
+
+ /* set up cuse_conn */
+ cc = kzalloc(sizeof(*cc), GFP_KERNEL);
+ if (!cc)
+ return -ENOMEM;
+
+ fuse_conn_init(&cc->fc);
+
+ INIT_LIST_HEAD(&cc->list);
+ cc->fc.release = cuse_fc_release;
+
+ cc->fc.connected = 1;
+ cc->fc.initialized = 1;
+ rc = cuse_send_init(cc);
+ if (rc) {
+ fuse_conn_put(&cc->fc);
+ return rc;
+ }
+ file->private_data = &cc->fc; /* channel owns base reference to cc */
+
+ return 0;
+}
+
+/**
+ * cuse_channel_release - release method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being closed
+ *
+ * Disconnect the channel, deregister CUSE device and initiate
+ * destruction by putting the default reference.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_release(struct inode *inode, struct file *file)
+{
+ struct cuse_conn *cc = fc_to_cc(file->private_data);
+ int rc;
+
+ /* remove from the conntbl, no more access from this point on */
+ mutex_lock(&cuse_lock);
+ list_del_init(&cc->list);
+ mutex_unlock(&cuse_lock);
+
+ /* remove device */
+ if (cc->dev)
+ device_unregister(cc->dev);
+ if (cc->cdev) {
+ unregister_chrdev_region(cc->cdev->dev, 1);
+ cdev_del(cc->cdev);
+ }
+
+ rc = fuse_dev_release(inode, file); /* puts the base reference */
+
+ return rc;
+}
+
+static struct file_operations cuse_channel_fops; /* initialized during init */
+
+
+/**************************************************************************
+ * Misc stuff and module initializatiion
+ *
+ * CUSE exports the same set of attributes to sysfs as fusectl.
+ */
+
+static ssize_t cuse_class_waiting_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cuse_conn *cc = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
+}
+static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL);
+
+static ssize_t cuse_class_abort_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct cuse_conn *cc = dev_get_drvdata(dev);
+
+ fuse_abort_conn(&cc->fc);
+ return count;
+}
+static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);
+
+static struct attribute *cuse_class_dev_attrs[] = {
+ &dev_attr_waiting.attr,
+ &dev_attr_abort.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(cuse_class_dev);
+
+static struct miscdevice cuse_miscdev = {
+ .minor = CUSE_MINOR,
+ .name = "cuse",
+ .fops = &cuse_channel_fops,
+};
+
+MODULE_ALIAS_MISCDEV(CUSE_MINOR);
+MODULE_ALIAS("devname:cuse");
+
+static int __init cuse_init(void)
+{
+ int i, rc;
+
+ /* init conntbl */
+ for (i = 0; i < CUSE_CONNTBL_LEN; i++)
+ INIT_LIST_HEAD(&cuse_conntbl[i]);
+
+ /* inherit and extend fuse_dev_operations */
+ cuse_channel_fops = fuse_dev_operations;
+ cuse_channel_fops.owner = THIS_MODULE;
+ cuse_channel_fops.open = cuse_channel_open;
+ cuse_channel_fops.release = cuse_channel_release;
+
+ cuse_class = class_create(THIS_MODULE, "cuse");
+ if (IS_ERR(cuse_class))
+ return PTR_ERR(cuse_class);
+
+ cuse_class->dev_groups = cuse_class_dev_groups;
+
+ rc = misc_register(&cuse_miscdev);
+ if (rc) {
+ class_destroy(cuse_class);
+ return rc;
+ }
+
+ return 0;
+}
+
+static void __exit cuse_exit(void)
+{
+ misc_deregister(&cuse_miscdev);
+ class_destroy(cuse_class);
+}
+
+module_init(cuse_init);
+module_exit(cuse_exit);
+
+MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
+MODULE_DESCRIPTION("Character device in Userspace");
+MODULE_LICENSE("GPL");
Code Review / kvmfornfv.git / blobdiff