diff options
Diffstat (limited to 'fs/fuse/cuse.c')
| -rw-r--r-- | fs/fuse/cuse.c | 610 |
1 files changed, 610 insertions, 0 deletions
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c new file mode 100644 index 000000000000..de792dcf3274 --- /dev/null +++ b/fs/fuse/cuse.c @@ -0,0 +1,610 @@ +/* + * 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"); |