1 files changed, 455 insertions, 0 deletions
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
new file mode 100644
index 00000000..8493536e
--- /dev/null
+++ b/drivers/base/devtmpfs.c
@@ -0,0 +1,455 @@
+/*
+ * 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/ramfs.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/kthread.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 */
+	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.name = device_get_devnode(dev, &req.mode, &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, &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, 1);
+	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;
+	dput(dentry);
+	mutex_unlock(&path.dentry->d_inode->i_mutex);
+	path_put(&path);
+	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, 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;
+
+		/* 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 = &thread;
+	}
+	dput(dentry);
+
+	mutex_unlock(&path.dentry->d_inode->i_mutex);
+	path_put(&path);
+	return err;
+}
+
+static int dev_rmdir(const char *name)
+{
+	struct nameidata nd;
+	struct dentry *dentry;
+	int err;
+
+	err = kern_path_parent(name, &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 == &thread)
+				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;
+
+	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 nameidata nd;
+	struct dentry *dentry;
+	struct kstat stat;
+	int deleted = 1;
+	int err;
+
+	err = kern_path_parent(nodename, &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_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);
+	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, struct device *dev)
+{
+	if (mode)
+		return handle_create(name, mode, dev);
+	else
+		return handle_remove(name, dev);
+}
+
+static int devtmpfsd(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);
+	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->dev);
+				complete(&req->done);
+				req = next;
+			}
+			spin_lock(&req_lock);
+		}
+		__set_current_state(TASK_INTERRUPTIBLE);
+		spin_unlock(&req_lock);
+		schedule();
+	}
+	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, &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;
+}