/* * 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 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/cred.h>#include <linux/sched.h>#include <linux/init_task.h> static struct vfsmount *dev_mnt; #if defined CONFIG_DEVTMPFS_MOUNTstatic int dev_mount = 1;#elsestatic int dev_mount;#endif static DEFINE_MUTEX(dirlock); static int __init mount_param(char *str){	dev_mount = simple_strtoul(str, NULL, 0);	return 1;}__setup("devtmpfs.mount=", mount_param); static int dev_get_sb(struct file_system_type *fs_type, int flags,		      const char *dev_name, void *data, struct vfsmount *mnt){	return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt);} static struct file_system_type dev_fs_type = {	.name = "devtmpfs",	.get_sb = dev_get_sb,	.kill_sb = kill_litter_super,}; #ifdef CONFIG_BLOCKstatic inline int is_blockdev(struct device *dev){	return dev->class == &block_class;}#elsestatic inline int is_blockdev(struct device *dev) { return 0; }#endif static int dev_mkdir(const char *name, mode_t mode){	struct nameidata nd;	struct dentry *dentry;	int err; 	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,			      name, LOOKUP_PARENT, &nd);	if (err)		return err; 	dentry = lookup_create(&nd, 1);	if (!IS_ERR(dentry)) {		err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);		if (!err)			/* mark as kernel-created inode */			dentry->d_inode->i_private = &dev_mnt;		dput(dentry);	} else {		err = PTR_ERR(dentry);	} 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);	path_put(&nd.path);	return err;} static int create_path(const char *nodepath){	int err; 	mutex_lock(&dirlock);	err = dev_mkdir(nodepath, 0755);	if (err == -ENOENT) {		char *path;		char *s; 		/* parent directories do not exist, create them */		path = kstrdup(nodepath, GFP_KERNEL);		if (!path) {			err = -ENOMEM;			goto out;		}		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);	}out:	mutex_unlock(&dirlock);	return err;} int devtmpfs_create_node(struct device *dev){	const char *tmp = NULL;	const char *nodename;	const struct cred *curr_cred;	mode_t mode = 0;	struct nameidata nd;	struct dentry *dentry;	int err; 	if (!dev_mnt)		return 0; 	nodename = device_get_devnode(dev, &mode, &tmp);	if (!nodename)		return -ENOMEM; 	if (mode == 0)		mode = 0600;	if (is_blockdev(dev))		mode |= S_IFBLK;	else		mode |= S_IFCHR; 	curr_cred = override_creds(&init_cred); 	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,			      nodename, LOOKUP_PARENT, &nd);	if (err == -ENOENT) {		create_path(nodename);		err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,				      nodename, LOOKUP_PARENT, &nd);	}	if (err)		goto out; 	dentry = lookup_create(&nd, 0);	if (!IS_ERR(dentry)) {		err = vfs_mknod(nd.path.dentry->d_inode,				dentry, mode, dev->devt);		if (!err) {			struct iattr newattrs; 			/* fixup possibly umasked mode */			newattrs.ia_mode = mode;			newattrs.ia_valid = ATTR_MODE;			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 = &dev_mnt;		}		dput(dentry);	} else {		err = PTR_ERR(dentry);	} 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);	path_put(&nd.path);out:	kfree(tmp);	revert_creds(curr_cred);	return err;} static int dev_rmdir(const char *name){	struct nameidata nd;	struct dentry *dentry;	int err; 	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,			      name, LOOKUP_PARENT, &nd);	if (err)		return err; 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);	dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);	if (!IS_ERR(dentry)) {		if (dentry->d_inode) {			if (dentry->d_inode->i_private == &dev_mnt)				err = vfs_rmdir(nd.path.dentry->d_inode,						dentry);			else				err = -EPERM;		} else {			err = -ENOENT;		}		dput(dentry);	} else {		err = PTR_ERR(dentry);	} 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);	path_put(&nd.path);	return err;} static int delete_path(const char *nodepath){	const char *path;	int err = 0; 	path = kstrdup(nodepath, GFP_KERNEL);	if (!path)		return -ENOMEM; 	mutex_lock(&dirlock);	for (;;) {		char *base; 		base = strrchr(path, '/');		if (!base)			break;		base[0] = '\0';		err = dev_rmdir(path);		if (err)			break;	}	mutex_unlock(&dirlock); 	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 != &dev_mnt)		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;} int devtmpfs_delete_node(struct device *dev){	const char *tmp = NULL;	const char *nodename;	const struct cred *curr_cred;	struct nameidata nd;	struct dentry *dentry;	struct kstat stat;	int deleted = 1;	int err; 	if (!dev_mnt)		return 0; 	nodename = device_get_devnode(dev, NULL, &tmp);	if (!nodename)		return -ENOMEM; 	curr_cred = override_creds(&init_cred);	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,			      nodename, LOOKUP_PARENT, &nd);	if (err)		goto out; 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);	dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);	if (!IS_ERR(dentry)) {		if (dentry->d_inode) {			err = vfs_getattr(nd.path.mnt, dentry, &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 = 0;				newattrs.ia_gid = 0;				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(nd.path.dentry->d_inode,						 dentry);				if (!err || err == -ENOENT)					deleted = 1;			}		} else {			err = -ENOENT;		}		dput(dentry);	} else {		err = PTR_ERR(dentry);	}	mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 	path_put(&nd.path);	if (deleted && strchr(nodename, '/'))		delete_path(nodename);out:	kfree(tmp);	revert_creds(curr_cred);	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 (!dev_mount)		return 0; 	if (!dev_mnt)		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;} /* * Create devtmpfs instance, driver-core devices will add their device * nodes here. */int __init devtmpfs_init(void){	int err;	struct vfsmount *mnt;	char options[] = "mode=0755"; 	err = register_filesystem(&dev_fs_type);	if (err) {		printk(KERN_ERR "devtmpfs: unable to register devtmpfs "		       "type %i\n", err);		return err;	} 	mnt = kern_mount_data(&dev_fs_type, options);	if (IS_ERR(mnt)) {		err = PTR_ERR(mnt);		printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);		unregister_filesystem(&dev_fs_type);		return err;	}	dev_mnt = mnt; 	printk(KERN_INFO "devtmpfs: initialized\n");	return 0;}