6 files changed, 403 insertions, 0 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 8f006f96ff53..ee377270beb9 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -8,6 +8,31 @@ config UEVENT_HELPER_PATH
           Path to uevent helper program forked by the kernel for
           every uevent.
 
+config DEVTMPFS
+        bool "Create a kernel maintained /dev tmpfs (EXPERIMENTAL)"
+        depends on HOTPLUG && SHMEM && TMPFS
+        help
+          This creates a tmpfs filesystem, and mounts it at bootup
+          and mounts it at /dev. The kernel driver core creates device
+          nodes for all registered devices in that filesystem. All device
+          nodes are owned by root and have the default mode of 0600.
+          Userspace can add and delete the nodes as needed. This is
+          intended to simplify bootup, and make it possible to delay
+          the initial coldplug at bootup done by udev in userspace.
+          It should also provide a simpler way for rescue systems
+          to bring up a kernel with dynamic major/minor numbers.
+          Meaningful symlinks, permissions and device ownership must
+          still be handled by userspace.
+          If unsure, say N here.
+
+config DEVTMPFS_MOUNT
+        bool "Automount devtmpfs at /dev"
+        depends on DEVTMPFS
+        help
+          This will mount devtmpfs at /dev if the kernel mounts the root
+          filesystem. It will not affect initramfs based mounting.
+          If unsure, say N here.
+
 config STANDALONE
         bool "Select only drivers that don't need compile-time external firmware" if EXPERIMENTAL
         default y
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 1b2640ce74f0..c12c7f2f2a6f 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -4,6 +4,7 @@ obj-y			:= core.o sys.o bus.o dd.o \
                            driver.o class.o platform.o \
                            cpu.o firmware.o init.o map.o devres.o \
                            attribute_container.o transport_class.o
+obj-$(CONFIG_DEVTMPFS)  += devtmpfs.o
 obj-y                   += power/
 obj-$(CONFIG_HAS_DMA)   += dma-mapping.o
 obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
diff --git a/drivers/base/base.h b/drivers/base/base.h
index 503d59c57501..2ca7f5b7b824 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -139,3 +139,9 @@ static inline void module_add_driver(struct module *mod,
                                      struct device_driver *drv) { }
 static inline void module_remove_driver(struct device_driver *drv) { }
 #endif
+
+#ifdef CONFIG_DEVTMPFS
+extern int devtmpfs_init(void);
+#else
+static inline int devtmpfs_init(void) { return 0; }
+#endif
diff --git a/drivers/base/core.c b/drivers/base/core.c
index a992985d1fab..390e664ec1c7 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -929,6 +929,8 @@ int device_add(struct device *dev)
                 error = device_create_sys_dev_entry(dev);
                 if (error)
                         goto devtattrError;
+
+                devtmpfs_create_node(dev);
         }
 
         error = device_add_class_symlinks(dev);
@@ -1075,6 +1077,7 @@ void device_del(struct device *dev)
         if (parent)
                 klist_del(&dev->p->knode_parent);
         if (MAJOR(dev->devt)) {
+                devtmpfs_delete_node(dev);
                 device_remove_sys_dev_entry(dev);
                 device_remove_file(dev, &devt_attr);
         }
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
new file mode 100644
index 000000000000..fd488ad4263a
--- /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;
+}
diff --git a/drivers/base/init.c b/drivers/base/init.c
index 7bd9b6a5b01f..c8a934e79421 100644
--- a/drivers/base/init.c
+++ b/drivers/base/init.c
@@ -20,6 +20,7 @@
 void __init driver_init(void)
 {
         /* These are the core pieces */
+        devtmpfs_init();
         devices_init();
         buses_init();
         classes_init();