CUSE: implement CUSE - Character device in Userspace (151060ac) · Commits · 戴 / test

fs/Kconfig

+10 −0

Original line number	Diff line number	Diff line
		@@ -62,6 +62,16 @@ source "fs/autofs/Kconfig"
		source "fs/autofs4/Kconfig"
		source "fs/fuse/Kconfig"

		config CUSE
		tristate "Character device in Userpace support"
		depends on FUSE_FS
		help
		This FUSE extension allows character devices to be
		implemented in userspace.

		If you want to develop or use userspace character device
		based on CUSE, answer Y or M.

		config GENERIC_ACL
		bool
		select FS_POSIX_ACL

fs/fuse/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -3,5 +3,6 @@
		#

		obj-$(CONFIG_FUSE_FS) += fuse.o
		obj-$(CONFIG_CUSE) += cuse.o

		fuse-objs := dev.o dir.o file.o inode.o control.o

fs/fuse/cuse.c

0 → 100644

+610 −0

Original line number	Diff line number	Diff line
		/*
		* 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/spinlock.h>
		#include <linux/stat.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_SPINLOCK(cuse_lock); /* protects cuse_conntbl */
		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(struct file file, char __user buf, size_t count,
		loff_t *ppos)
		{
		loff_t pos = 0;

		return fuse_direct_io(file, buf, count, &pos, 0);
		}

		static ssize_t cuse_write(struct file file, const char __user buf,
		size_t count, loff_t *ppos)
		{
		loff_t pos = 0;
		/*
		* No locking or generic_write_checks(), the server is
		* responsible for locking and sanity checks.
		*/
		return fuse_direct_io(file, buf, count, &pos, 1);
		}

		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 */
		spin_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;
		}
		spin_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 = cuse_read,
		.write = cuse_write,
		.open = cuse_open,
		.release = cuse_release,
		.unlocked_ioctl = cuse_file_ioctl,
		.compat_ioctl = cuse_file_compat_ioctl,
		.poll = fuse_file_poll,
		};


		/**************************************************************************
		* 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 key, 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);
		struct cuse_init_out *arg = &req->misc.cuse_init_out;
		struct page *page = req->pages[0];
		struct cuse_devinfo devinfo = { };
		struct device *dev;
		struct cdev *cdev;
		dev_t devt;
		int rc;

		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);

		rc = device_add(dev);
		if (rc)
		goto err_device;

		/* register cdev */
		rc = -ENOMEM;
		cdev = cdev_alloc();
		if (!cdev)
		goto err_device;

		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 */
		spin_lock(&cuse_lock);
		list_add(&cc->list, cuse_conntbl_head(devt));
		spin_unlock(&cuse_lock);

		/* announce device availability */
		dev_set_uevent_suppress(dev, 0);
		kobject_uevent(&dev->kobj, KOBJ_ADD);
		out:
		__free_page(page);
		return;

		err_cdev:
		cdev_del(cdev);
		err_device:
		put_device(dev);
		err_region:
		unregister_chrdev_region(devt, 1);
		err:
		fc->conn_error = 1;
		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;

		BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);

		req = fuse_get_req(fc);
		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;

		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 = &req->misc.cuse_init_out;
		req->out.args[1].size = CUSE_INIT_INFO_MAX;
		req->out.argvar = 1;
		req->out.argpages = 1;
		req->pages[0] = page;
		req->num_pages = 1;
		req->end = cuse_process_init_reply;
		fuse_request_send_background(fc, req);

		return 0;

		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(cc);
		}

		/**
		* 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 initilaization 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.blocked = 0;
		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 */
		spin_lock(&cuse_lock);
		list_del_init(&cc->list);
		spin_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);
		}

		/* kill connection and shutdown channel */
		fuse_conn_kill(&cc->fc);
		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 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 struct device_attribute cuse_class_dev_attrs[] = {
		__ATTR(waiting, S_IFREG \| 0400, cuse_class_waiting_show, NULL),
		__ATTR(abort, S_IFREG \| 0200, NULL, cuse_class_abort_store),
		{ }
		};

		static struct miscdevice cuse_miscdev = {
		.minor = MISC_DYNAMIC_MINOR,
		.name = "cuse",
		.fops = &cuse_channel_fops,
		};

		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_attrs = cuse_class_dev_attrs;

		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");

include/linux/fuse.h

+31 −0

Original line number	Diff line number	Diff line
		@@ -120,6 +120,13 @@ struct fuse_file_lock {
		#define FUSE_EXPORT_SUPPORT (1 << 4)
		#define FUSE_BIG_WRITES (1 << 5)

		/**
		* CUSE INIT request/reply flags
		*
		* CUSE_UNRESTRICTED_IOCTL: use unrestricted ioctl
		*/
		#define CUSE_UNRESTRICTED_IOCTL (1 << 0)

		/**
		* Release flags
		*/
		@@ -210,6 +217,9 @@ enum fuse_opcode {
		FUSE_DESTROY = 38,
		FUSE_IOCTL = 39,
		FUSE_POLL = 40,

		/* CUSE specific operations */
		CUSE_INIT = 4096,
		};

		enum fuse_notify_code {
		@@ -401,6 +411,27 @@ struct fuse_init_out {
		__u32 max_write;
		};

		#define CUSE_INIT_INFO_MAX 4096

		struct cuse_init_in {
		__u32 major;
		__u32 minor;
		__u32 unused;
		__u32 flags;
		};

		struct cuse_init_out {
		__u32 major;
		__u32 minor;
		__u32 unused;
		__u32 flags;
		__u32 max_read;
		__u32 max_write;
		__u32 dev_major; /* chardev major */
		__u32 dev_minor; /* chardev minor */
		__u32 spare[10];
		};

		struct fuse_interrupt_in {
		__u64 unique;
		};

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