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- /*
- * devtmpfs - kernel-maintained tmpfs-based /dev
- *
- * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
- *
- * During bootup, before any driver core device is registered,
- * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
- * device which requests a device node, will add a node in this
- * filesystem.
- * By default, all devices are named after the name of the device,
- * owned by root and have a default mode of 0600. Subsystems can
- * overwrite the default setting if needed.
- */
- #include <linux/kernel.h>
- #include <linux/syscalls.h>
- #include <linux/mount.h>
- #include <linux/device.h>
- #include <linux/genhd.h>
- #include <linux/namei.h>
- #include <linux/fs.h>
- #include <linux/shmem_fs.h>
- #include <linux/ramfs.h>
- #include <linux/sched.h>
- #include <linux/slab.h>
- #include <linux/kthread.h>
- #include "base.h"
- static struct task_struct *thread;
- #if defined CONFIG_DEVTMPFS_MOUNT
- static int mount_dev = 1;
- #else
- static int mount_dev;
- #endif
- static DEFINE_SPINLOCK(req_lock);
- static struct req {
- struct req *next;
- struct completion done;
- int err;
- const char *name;
- umode_t mode; /* 0 => delete */
- kuid_t uid;
- kgid_t gid;
- struct device *dev;
- } *requests;
- static int __init mount_param(char *str)
- {
- mount_dev = simple_strtoul(str, NULL, 0);
- return 1;
- }
- __setup("devtmpfs.mount=", mount_param);
- static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
- const char *dev_name, void *data)
- {
- #ifdef CONFIG_TMPFS
- return mount_single(fs_type, flags, data, shmem_fill_super);
- #else
- return mount_single(fs_type, flags, data, ramfs_fill_super);
- #endif
- }
- static struct file_system_type dev_fs_type = {
- .name = "devtmpfs",
- .mount = dev_mount,
- .kill_sb = kill_litter_super,
- };
- #ifdef CONFIG_BLOCK
- static inline int is_blockdev(struct device *dev)
- {
- return dev->class == &block_class;
- }
- #else
- static inline int is_blockdev(struct device *dev) { return 0; }
- #endif
- int devtmpfs_create_node(struct device *dev)
- {
- const char *tmp = NULL;
- struct req req;
- if (!thread)
- return 0;
- req.mode = 0;
- req.uid = GLOBAL_ROOT_UID;
- req.gid = GLOBAL_ROOT_GID;
- req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
- if (!req.name)
- return -ENOMEM;
- if (req.mode == 0)
- req.mode = 0600;
- if (is_blockdev(dev))
- req.mode |= S_IFBLK;
- else
- req.mode |= S_IFCHR;
- req.dev = dev;
- init_completion(&req.done);
- spin_lock(&req_lock);
- req.next = requests;
- requests = &req;
- spin_unlock(&req_lock);
- wake_up_process(thread);
- wait_for_completion(&req.done);
- kfree(tmp);
- return req.err;
- }
- int devtmpfs_delete_node(struct device *dev)
- {
- const char *tmp = NULL;
- struct req req;
- if (!thread)
- return 0;
- req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
- if (!req.name)
- return -ENOMEM;
- req.mode = 0;
- req.dev = dev;
- init_completion(&req.done);
- spin_lock(&req_lock);
- req.next = requests;
- requests = &req;
- spin_unlock(&req_lock);
- wake_up_process(thread);
- wait_for_completion(&req.done);
- kfree(tmp);
- return req.err;
- }
- static int dev_mkdir(const char *name, umode_t mode)
- {
- struct dentry *dentry;
- struct path path;
- int err;
- dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
- err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
- if (!err)
- /* mark as kernel-created inode */
- dentry->d_inode->i_private = &thread;
- done_path_create(&path, dentry);
- return err;
- }
- static int create_path(const char *nodepath)
- {
- char *path;
- char *s;
- int err = 0;
- /* parent directories do not exist, create them */
- path = kstrdup(nodepath, GFP_KERNEL);
- if (!path)
- return -ENOMEM;
- s = path;
- for (;;) {
- s = strchr(s, '/');
- if (!s)
- break;
- s[0] = '\0';
- err = dev_mkdir(path, 0755);
- if (err && err != -EEXIST)
- break;
- s[0] = '/';
- s++;
- }
- kfree(path);
- return err;
- }
- static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
- kgid_t gid, struct device *dev)
- {
- struct dentry *dentry;
- struct path path;
- int err;
- dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
- if (dentry == ERR_PTR(-ENOENT)) {
- create_path(nodename);
- dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
- }
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
- err = vfs_mknod(path.dentry->d_inode, dentry, mode, dev->devt);
- if (!err) {
- struct iattr newattrs;
- newattrs.ia_mode = mode;
- newattrs.ia_uid = uid;
- newattrs.ia_gid = gid;
- newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
- mutex_lock(&dentry->d_inode->i_mutex);
- notify_change(dentry, &newattrs);
- mutex_unlock(&dentry->d_inode->i_mutex);
- /* mark as kernel-created inode */
- dentry->d_inode->i_private = &thread;
- }
- done_path_create(&path, dentry);
- return err;
- }
- static int dev_rmdir(const char *name)
- {
- struct path parent;
- struct dentry *dentry;
- int err;
- dentry = kern_path_locked(name, &parent);
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
- if (dentry->d_inode) {
- if (dentry->d_inode->i_private == &thread)
- err = vfs_rmdir(parent.dentry->d_inode, dentry);
- else
- err = -EPERM;
- } else {
- err = -ENOENT;
- }
- dput(dentry);
- mutex_unlock(&parent.dentry->d_inode->i_mutex);
- path_put(&parent);
- return err;
- }
- static int delete_path(const char *nodepath)
- {
- const char *path;
- int err = 0;
- path = kstrdup(nodepath, GFP_KERNEL);
- if (!path)
- return -ENOMEM;
- for (;;) {
- char *base;
- base = strrchr(path, '/');
- if (!base)
- break;
- base[0] = '\0';
- err = dev_rmdir(path);
- if (err)
- break;
- }
- kfree(path);
- return err;
- }
- static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
- {
- /* did we create it */
- if (inode->i_private != &thread)
- return 0;
- /* does the dev_t match */
- if (is_blockdev(dev)) {
- if (!S_ISBLK(stat->mode))
- return 0;
- } else {
- if (!S_ISCHR(stat->mode))
- return 0;
- }
- if (stat->rdev != dev->devt)
- return 0;
- /* ours */
- return 1;
- }
- static int handle_remove(const char *nodename, struct device *dev)
- {
- struct path parent;
- struct dentry *dentry;
- int deleted = 1;
- int err;
- dentry = kern_path_locked(nodename, &parent);
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
- if (dentry->d_inode) {
- struct kstat stat;
- struct path p = {.mnt = parent.mnt, .dentry = dentry};
- err = vfs_getattr(&p, &stat);
- if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
- struct iattr newattrs;
- /*
- * before unlinking this node, reset permissions
- * of possible references like hardlinks
- */
- newattrs.ia_uid = GLOBAL_ROOT_UID;
- newattrs.ia_gid = GLOBAL_ROOT_GID;
- newattrs.ia_mode = stat.mode & ~0777;
- newattrs.ia_valid =
- ATTR_UID|ATTR_GID|ATTR_MODE;
- mutex_lock(&dentry->d_inode->i_mutex);
- notify_change(dentry, &newattrs);
- mutex_unlock(&dentry->d_inode->i_mutex);
- err = vfs_unlink(parent.dentry->d_inode, dentry);
- if (!err || err == -ENOENT)
- deleted = 1;
- }
- } else {
- err = -ENOENT;
- }
- dput(dentry);
- mutex_unlock(&parent.dentry->d_inode->i_mutex);
- path_put(&parent);
- if (deleted && strchr(nodename, '/'))
- delete_path(nodename);
- return err;
- }
- /*
- * If configured, or requested by the commandline, devtmpfs will be
- * auto-mounted after the kernel mounted the root filesystem.
- */
- int devtmpfs_mount(const char *mntdir)
- {
- int err;
- if (!mount_dev)
- return 0;
- if (!thread)
- return 0;
- err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
- if (err)
- printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
- else
- printk(KERN_INFO "devtmpfs: mounted\n");
- return err;
- }
- static DECLARE_COMPLETION(setup_done);
- static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
- struct device *dev)
- {
- if (mode)
- return handle_create(name, mode, uid, gid, dev);
- else
- return handle_remove(name, dev);
- }
- static void devtmpfsd(void)
- {
- // char options[] = "mode=0755";
- // int *err = p;
- // *err = sys_unshare(CLONE_NEWNS);
- // if (*err)
- // goto out;
- // *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
- // if (*err)
- // goto out;
- // sys_chdir("/.."); /* will traverse into overmounted root */
- // sys_chroot(".");
- // complete(&setup_done);
- while (1) {
- spin_lock(&req_lock);
- while (requests) {
- struct req *req = requests;
- requests = NULL;
- spin_unlock(&req_lock);
- while (req) {
- struct req *next = req->next;
- req->err = handle(req->name, req->mode,
- req->uid, req->gid, req->dev);
- complete(&req->done);
- req = next;
- }
- spin_lock(&req_lock);
- }
- __set_current_state(TASK_INTERRUPTIBLE);
- spin_unlock(&req_lock);
- schedule();
- }
- }
- static int __init devtmpfsd_run(void *p)
- {
- char options[] = "mode=0755";
- int *err = p;
- *err = sys_unshare(CLONE_NEWNS);
- if (*err)
- goto out;
- *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
- if (*err)
- goto out;
- sys_chdir("/.."); /* will traverse into overmounted root */
- sys_chroot(".");
- complete(&setup_done);
- devtmpfsd();
- return 0;
- out:
- complete(&setup_done);
- return *err;
- }
- /*
- * Create devtmpfs instance, driver-core devices will add their device
- * nodes here.
- */
- int __init devtmpfs_init(void)
- {
- int err = register_filesystem(&dev_fs_type);
- if (err) {
- printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
- "type %i\n", err);
- return err;
- }
- thread = kthread_run(devtmpfsd_run, &err, "kdevtmpfs");
- if (!IS_ERR(thread)) {
- wait_for_completion(&setup_done);
- } else {
- err = PTR_ERR(thread);
- thread = NULL;
- }
- if (err) {
- printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
- unregister_filesystem(&dev_fs_type);
- return err;
- }
- printk(KERN_INFO "devtmpfs: initialized\n");
- return 0;
- }
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