/*
* 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. The node is named after the the name of the device,
* or the susbsytem can provide a custom name. All devices are
* owned by root and have a mode of 0600.
*/
#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/init_task.h>
static struct vfsmount *dev_mnt;
#if defined CONFIG_DEVTMPFS_MOUNT
static int dev_mount = 1;
#else
static int dev_mount;
#endif
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_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
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);
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)
{
char *path;
struct nameidata nd;
int err = 0;
path = kstrdup(nodepath, GFP_KERNEL);
if (!path)
return -ENOMEM;
err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
path, LOOKUP_PARENT, &nd);
if (err == 0) {
struct dentry *dentry;
/* create directory right away */
dentry = lookup_create(&nd, 1);
if (!IS_ERR(dentry)) {
err = vfs_mkdir(nd.path.dentry->d_inode,
dentry, 0755);
dput(dentry);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
} else if (err == -ENOENT) {
char *s;
/* parent directories do not exist, create them */
s = path;
while (1) {
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;
}
int devtmpfs_create_node(struct device *dev)
{
const char *tmp = NULL;
const char *nodename;
const struct cred *curr_cred;
mode_t mode;
struct nameidata nd;
struct dentry *dentry;
int err;
if (!dev_mnt)
return 0;
nodename = device_get_nodename(dev, &tmp);
if (!nodename)
return -ENOMEM;
if (is_blockdev(dev))
mode = S_IFBLK|0600;
else
mode = S_IFCHR|0600;
curr_cred = override_creds(&init_cred);
err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
nodename, LOOKUP_PARENT, &nd);
if (err == -ENOENT) {
/* create missing parent directories */
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);
/* mark as kernel created inode */
if (!err)
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)
err = vfs_rmdir(nd.path.dentry->d_inode, dentry);
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;
while (1) {
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 != &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_nodename(dev, &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)) {
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 *mountpoint)
{
struct path path;
int err;
if (!dev_mount)
return 0;
if (!dev_mnt)
return 0;
err = kern_path(mountpoint, LOOKUP_FOLLOW, &path);
if (err)
return err;
err = do_add_mount(dev_mnt, &path, 0, NULL);
if (err)
printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
else
printk(KERN_INFO "devtmpfs: mounted\n");
path_put(&path);
return err;
}
/*
* Create devtmpfs instance, driver-core devices will add their device
* nodes here.
*/
int __init devtmpfs_init(void)
{
int err;
struct vfsmount *mnt;
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(&dev_fs_type);
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;
}
