diff options
Diffstat (limited to 'drivers/base/devtmpfs.c')
| -rw-r--r-- | drivers/base/devtmpfs.c | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c new file mode 100644 index 00000000000..fd488ad4263 --- /dev/null +++ b/drivers/base/devtmpfs.c @@ -0,0 +1,367 @@ +/* + * 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; +} |