kdbus: add driver skeleton, ioctl entry points and utility functions

Add the basic driver structure.

handle.c is the main ioctl command dispatcher that calls into other parts
of the driver.

main.c contains the code that creates the initial domain at startup, and
util.c has utility functions such as item iterators that are shared with
other files.

limits.h describes limits on things like maximum data structure sizes,
number of messages per users and suchlike. Some of the numbers currently
picked are rough ideas of what what might be sufficient and are probably
rather conservative.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

7 files changed, 1167 insertions, 0 deletions

diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 8136e1fd30fd..54e091ebb862 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -292,6 +292,7 @@ Code  Seq#(hex)	Include File		Comments
 0x92	00-0F	drivers/usb/mon/mon_bin.c
 0x93	60-7F	linux/auto_fs.h
 0x94	all	fs/btrfs/ioctl.h
+0x95	all	uapi/linux/kdbus.h	kdbus IPC driver
 0x97	00-7F	fs/ceph/ioctl.h		Ceph file system
 0x99	00-0F				537-Addinboard driver
 					<mailto:buk@buks.ipn.de>
diff --git a/ipc/kdbus/handle.c b/ipc/kdbus/handle.c
new file mode 100644
index 000000000000..f72dbe513b4a
--- /dev/null
+++ b/ipc/kdbus/handle.c
@@ -0,0 +1,617 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@opendz.org>
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kdev_t.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "endpoint.h"
+#include "fs.h"
+#include "handle.h"
+#include "item.h"
+#include "match.h"
+#include "message.h"
+#include "names.h"
+#include "domain.h"
+#include "policy.h"
+
+static int kdbus_args_verify(struct kdbus_args *args)
+{
+	struct kdbus_item *item;
+	size_t i;
+	int ret;
+
+	KDBUS_ITEMS_FOREACH(item, args->items, args->items_size) {
+		struct kdbus_arg *arg = NULL;
+
+		if (!KDBUS_ITEM_VALID(item, args->items, args->items_size))
+			return -EINVAL;
+
+		for (i = 0; i < args->argc; ++i)
+			if (args->argv[i].type == item->type)
+				break;
+		if (i >= args->argc)
+			return -EINVAL;
+
+		arg = &args->argv[i];
+
+		ret = kdbus_item_validate(item);
+		if (ret < 0)
+			return ret;
+
+		if (arg->item && !arg->multiple)
+			return -EINVAL;
+
+		arg->item = item;
+	}
+
+	if (!KDBUS_ITEMS_END(item, args->items, args->items_size))
+		return -EINVAL;
+
+	for (i = 0; i < args->argc; ++i)
+		if (args->argv[i].mandatory && !args->argv[i].item)
+			return -EINVAL;
+
+	return 0;
+}
+
+static int kdbus_args_negotiate(struct kdbus_args *args)
+{
+	struct kdbus_item __user *user;
+	struct kdbus_item *negotiation;
+	size_t i, j, num;
+
+	/*
+	 * If KDBUS_FLAG_NEGOTIATE is set, we overwrite the flags field with
+	 * the set of supported flags. Furthermore, if an KDBUS_ITEM_NEGOTIATE
+	 * item is passed, we iterate its payload (array of u64, each set to an
+	 * item type) and clear all unsupported item-types to 0.
+	 * The caller might do this recursively, if other flags or objects are
+	 * embedded in the payload itself.
+	 */
+
+	if (args->cmd->flags & KDBUS_FLAG_NEGOTIATE) {
+		if (put_user(args->allowed_flags & ~KDBUS_FLAG_NEGOTIATE,
+			     &args->user->flags))
+			return -EFAULT;
+	}
+
+	if (args->argc < 1 || args->argv[0].type != KDBUS_ITEM_NEGOTIATE ||
+	    !args->argv[0].item)
+		return 0;
+
+	negotiation = args->argv[0].item;
+	user = (struct kdbus_item __user *)
+		((u8 __user *)args->user +
+		 ((u8 *)negotiation - (u8 *)args->cmd));
+	num = KDBUS_ITEM_PAYLOAD_SIZE(negotiation) / sizeof(u64);
+
+	for (i = 0; i < num; ++i) {
+		for (j = 0; j < args->argc; ++j)
+			if (negotiation->data64[i] == args->argv[j].type)
+				break;
+
+		if (j < args->argc)
+			continue;
+
+		/* this item is not supported, clear it out */
+		negotiation->data64[i] = 0;
+		if (put_user(negotiation->data64[i], &user->data64[i]))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/**
+ * __kdbus_args_parse() - parse payload of kdbus command
+ * @args:		object to parse data into
+ * @argp:		user-space location of command payload to parse
+ * @type_size:		overall size of command payload to parse
+ * @items_offset:	offset of items array in command payload
+ * @out:		output variable to store pointer to copied payload
+ *
+ * This parses the ioctl payload at user-space location @argp into @args. @args
+ * must be pre-initialized by the caller to reflect the supported flags and
+ * items of this command. This parser will then copy the command payload into
+ * kernel-space, verify correctness and consistency and cache pointers to parsed
+ * items and other data in @args.
+ *
+ * If this function succeeded, you must call kdbus_args_clear() to release
+ * allocated resources before destroying @args.
+ *
+ * Return: On failure a negative error code is returned. Otherwise, 1 is
+ * returned if negotiation was requested, 0 if not.
+ */
+int __kdbus_args_parse(struct kdbus_args *args, void __user *argp,
+		       size_t type_size, size_t items_offset, void **out)
+{
+	int ret;
+
+	args->cmd = kdbus_memdup_user(argp, type_size, KDBUS_CMD_MAX_SIZE);
+	if (IS_ERR(args->cmd))
+		return PTR_ERR(args->cmd);
+
+	args->cmd->return_flags = 0;
+	args->user = argp;
+	args->items = (void *)((u8 *)args->cmd + items_offset);
+	args->items_size = args->cmd->size - items_offset;
+
+	if (args->cmd->flags & ~args->allowed_flags) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	ret = kdbus_args_verify(args);
+	if (ret < 0)
+		goto error;
+
+	ret = kdbus_args_negotiate(args);
+	if (ret < 0)
+		goto error;
+
+	*out = args->cmd;
+	return !!(args->cmd->flags & KDBUS_FLAG_NEGOTIATE);
+
+error:
+	return kdbus_args_clear(args, ret);
+}
+
+/**
+ * kdbus_args_clear() - release allocated command resources
+ * @args:	object to release resources of
+ * @ret:	return value of this command
+ *
+ * This frees all allocated resources on @args and copies the command result
+ * flags into user-space. @ret is usually returned unchanged by this function,
+ * so it can be used in the final 'return' statement of the command handler.
+ *
+ * Return: -EFAULT if return values cannot be copied into user-space, otherwise
+ *         @ret is returned unchanged.
+ */
+int kdbus_args_clear(struct kdbus_args *args, int ret)
+{
+	if (!args)
+		return ret;
+
+	if (!IS_ERR_OR_NULL(args->cmd)) {
+		if (put_user(args->cmd->return_flags,
+			     &args->user->return_flags))
+			ret = -EFAULT;
+		kfree(args->cmd);
+		args->cmd = NULL;
+	}
+
+	return ret;
+}
+
+/**
+ * enum kdbus_handle_type - type an handle can be of
+ * @KDBUS_HANDLE_NONE:		no type set, yet
+ * @KDBUS_HANDLE_BUS_OWNER:	bus owner
+ * @KDBUS_HANDLE_EP_OWNER:	endpoint owner
+ * @KDBUS_HANDLE_CONNECTED:	endpoint connection after HELLO
+ */
+enum kdbus_handle_type {
+	KDBUS_HANDLE_NONE,
+	KDBUS_HANDLE_BUS_OWNER,
+	KDBUS_HANDLE_EP_OWNER,
+	KDBUS_HANDLE_CONNECTED,
+};
+
+/**
+ * struct kdbus_handle - handle to the kdbus system
+ * @rwlock:		handle lock
+ * @type:		type of this handle (KDBUS_HANDLE_*)
+ * @bus_owner:		bus this handle owns
+ * @ep_owner:		endpoint this handle owns
+ * @conn:		connection this handle owns
+ * @privileged:		Flag to mark a handle as privileged
+ */
+struct kdbus_handle {
+	struct rw_semaphore rwlock;
+
+	enum kdbus_handle_type type;
+	union {
+		struct kdbus_bus *bus_owner;
+		struct kdbus_ep *ep_owner;
+		struct kdbus_conn *conn;
+	};
+
+	bool privileged:1;
+};
+
+static int kdbus_handle_open(struct inode *inode, struct file *file)
+{
+	struct kdbus_handle *handle;
+	struct kdbus_node *node;
+	int ret;
+
+	node = kdbus_node_from_inode(inode);
+	if (!kdbus_node_acquire(node))
+		return -ESHUTDOWN;
+
+	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
+	if (!handle) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	init_rwsem(&handle->rwlock);
+	handle->type = KDBUS_HANDLE_NONE;
+
+	if (node->type == KDBUS_NODE_ENDPOINT) {
+		struct kdbus_ep *ep = kdbus_ep_from_node(node);
+		struct kdbus_bus *bus = ep->bus;
+
+		/*
+		 * A connection is privileged if it is opened on an endpoint
+		 * without custom policy and either:
+		 *   * the user has CAP_IPC_OWNER in the domain user namespace
+		 * or
+		 *   * the callers euid matches the uid of the bus creator
+		 */
+		if (!ep->user &&
+		    (ns_capable(bus->domain->user_namespace, CAP_IPC_OWNER) ||
+		     uid_eq(file->f_cred->euid, bus->node.uid)))
+			handle->privileged = true;
+	}
+
+	file->private_data = handle;
+	ret = 0;
+
+exit:
+	kdbus_node_release(node);
+	return ret;
+}
+
+static int kdbus_handle_release(struct inode *inode, struct file *file)
+{
+	struct kdbus_handle *handle = file->private_data;
+
+	switch (handle->type) {
+	case KDBUS_HANDLE_BUS_OWNER:
+		if (handle->bus_owner) {
+			kdbus_node_deactivate(&handle->bus_owner->node);
+			kdbus_bus_unref(handle->bus_owner);
+		}
+		break;
+	case KDBUS_HANDLE_EP_OWNER:
+		if (handle->ep_owner) {
+			kdbus_node_deactivate(&handle->ep_owner->node);
+			kdbus_ep_unref(handle->ep_owner);
+		}
+		break;
+	case KDBUS_HANDLE_CONNECTED:
+		kdbus_conn_disconnect(handle->conn, false);
+		kdbus_conn_unref(handle->conn);
+		break;
+	case KDBUS_HANDLE_NONE:
+		/* nothing to clean up */
+		break;
+	}
+
+	kfree(handle);
+
+	return 0;
+}
+
+static long kdbus_handle_ioctl_control(struct file *file, unsigned int cmd,
+				       void __user *argp)
+{
+	struct kdbus_handle *handle = file->private_data;
+	struct kdbus_node *node = file_inode(file)->i_private;
+	struct kdbus_domain *domain;
+	int ret = 0;
+
+	if (!kdbus_node_acquire(node))
+		return -ESHUTDOWN;
+
+	/*
+	 * The parent of control-nodes is always a domain, make sure to pin it
+	 * so the parent is actually valid.
+	 */
+	domain = kdbus_domain_from_node(node->parent);
+	if (!kdbus_node_acquire(&domain->node)) {
+		kdbus_node_release(node);
+		return -ESHUTDOWN;
+	}
+
+	switch (cmd) {
+	case KDBUS_CMD_BUS_MAKE: {
+		struct kdbus_bus *bus;
+
+		bus = kdbus_cmd_bus_make(domain, argp);
+		if (IS_ERR_OR_NULL(bus)) {
+			ret = PTR_ERR_OR_ZERO(bus);
+			break;
+		}
+
+		handle->type = KDBUS_HANDLE_BUS_OWNER;
+		handle->bus_owner = bus;
+		break;
+	}
+
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+	kdbus_node_release(&domain->node);
+	kdbus_node_release(node);
+	return ret;
+}
+
+static long kdbus_handle_ioctl_ep(struct file *file, unsigned int cmd,
+				  void __user *buf)
+{
+	struct kdbus_handle *handle = file->private_data;
+	struct kdbus_node *node = file_inode(file)->i_private;
+	struct kdbus_ep *ep, *file_ep = kdbus_ep_from_node(node);
+	struct kdbus_conn *conn;
+	int ret = 0;
+
+	if (!kdbus_node_acquire(node))
+		return -ESHUTDOWN;
+
+	switch (cmd) {
+	case KDBUS_CMD_ENDPOINT_MAKE:
+		/* creating custom endpoints is a privileged operation */
+		if (!handle->privileged) {
+			ret = -EPERM;
+			break;
+		}
+
+		ep = kdbus_cmd_ep_make(file_ep->bus, buf);
+		if (IS_ERR_OR_NULL(ep)) {
+			ret = PTR_ERR_OR_ZERO(ep);
+			break;
+		}
+
+		handle->type = KDBUS_HANDLE_EP_OWNER;
+		handle->ep_owner = ep;
+		break;
+
+	case KDBUS_CMD_HELLO:
+		conn = kdbus_cmd_hello(file_ep, handle->privileged, buf);
+		if (IS_ERR_OR_NULL(conn)) {
+			ret = PTR_ERR_OR_ZERO(conn);
+			break;
+		}
+
+		handle->type = KDBUS_HANDLE_CONNECTED;
+		handle->conn = conn;
+		break;
+
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+	kdbus_node_release(node);
+	return ret;
+}
+
+static long kdbus_handle_ioctl_ep_owner(struct file *file, unsigned int command,
+					void __user *buf)
+{
+	struct kdbus_handle *handle = file->private_data;
+	struct kdbus_ep *ep = handle->ep_owner;
+	int ret;
+
+	if (!kdbus_node_acquire(&ep->node))
+		return -ESHUTDOWN;
+
+	switch (command) {
+	case KDBUS_CMD_ENDPOINT_UPDATE:
+		ret = kdbus_cmd_ep_update(ep, buf);
+		break;
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+	kdbus_node_release(&ep->node);
+	return ret;
+}
+
+static long kdbus_handle_ioctl_connected(struct file *file,
+					 unsigned int command, void __user *buf)
+{
+	struct kdbus_handle *handle = file->private_data;
+	struct kdbus_conn *conn = handle->conn;
+	struct kdbus_conn *release_conn = NULL;
+	int ret;
+
+	release_conn = conn;
+	ret = kdbus_conn_acquire(release_conn);
+	if (ret < 0)
+		return ret;
+
+	switch (command) {
+	case KDBUS_CMD_BYEBYE:
+		/*
+		 * BYEBYE is special; we must not acquire a connection when
+		 * calling into kdbus_conn_disconnect() or we will deadlock,
+		 * because kdbus_conn_disconnect() will wait for all acquired
+		 * references to be dropped.
+		 */
+		kdbus_conn_release(release_conn);
+		release_conn = NULL;
+		ret = kdbus_cmd_byebye_unlocked(conn, buf);
+		break;
+	case KDBUS_CMD_NAME_ACQUIRE:
+		ret = kdbus_cmd_name_acquire(conn, buf);
+		break;
+	case KDBUS_CMD_NAME_RELEASE:
+		ret = kdbus_cmd_name_release(conn, buf);
+		break;
+	case KDBUS_CMD_LIST:
+		ret = kdbus_cmd_list(conn, buf);
+		break;
+	case KDBUS_CMD_CONN_INFO:
+		ret = kdbus_cmd_conn_info(conn, buf);
+		break;
+	case KDBUS_CMD_BUS_CREATOR_INFO:
+		ret = kdbus_cmd_bus_creator_info(conn, buf);
+		break;
+	case KDBUS_CMD_UPDATE:
+		ret = kdbus_cmd_update(conn, buf);
+		break;
+	case KDBUS_CMD_MATCH_ADD:
+		ret = kdbus_cmd_match_add(conn, buf);
+		break;
+	case KDBUS_CMD_MATCH_REMOVE:
+		ret = kdbus_cmd_match_remove(conn, buf);
+		break;
+	case KDBUS_CMD_SEND:
+		ret = kdbus_cmd_send(conn, file, buf);
+		break;
+	case KDBUS_CMD_RECV:
+		ret = kdbus_cmd_recv(conn, buf);
+		break;
+	case KDBUS_CMD_FREE:
+		ret = kdbus_cmd_free(conn, buf);
+		break;
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+	kdbus_conn_release(release_conn);
+	return ret;
+}
+
+static long kdbus_handle_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long arg)
+{
+	struct kdbus_handle *handle = file->private_data;
+	struct kdbus_node *node = kdbus_node_from_inode(file_inode(file));
+	void __user *argp = (void __user *)arg;
+	long ret = -EBADFD;
+
+	switch (cmd) {
+	case KDBUS_CMD_BUS_MAKE:
+	case KDBUS_CMD_ENDPOINT_MAKE:
+	case KDBUS_CMD_HELLO:
+		/* bail out early if already typed */
+		if (handle->type != KDBUS_HANDLE_NONE)
+			break;
+
+		down_write(&handle->rwlock);
+		if (handle->type == KDBUS_HANDLE_NONE) {
+			if (node->type == KDBUS_NODE_CONTROL)
+				ret = kdbus_handle_ioctl_control(file, cmd,
+								 argp);
+			else if (node->type == KDBUS_NODE_ENDPOINT)
+				ret = kdbus_handle_ioctl_ep(file, cmd, argp);
+		}
+		up_write(&handle->rwlock);
+		break;
+
+	case KDBUS_CMD_ENDPOINT_UPDATE:
+	case KDBUS_CMD_BYEBYE:
+	case KDBUS_CMD_NAME_ACQUIRE:
+	case KDBUS_CMD_NAME_RELEASE:
+	case KDBUS_CMD_LIST:
+	case KDBUS_CMD_CONN_INFO:
+	case KDBUS_CMD_BUS_CREATOR_INFO:
+	case KDBUS_CMD_UPDATE:
+	case KDBUS_CMD_MATCH_ADD:
+	case KDBUS_CMD_MATCH_REMOVE:
+	case KDBUS_CMD_SEND:
+	case KDBUS_CMD_RECV:
+	case KDBUS_CMD_FREE:
+		down_read(&handle->rwlock);
+		if (handle->type == KDBUS_HANDLE_EP_OWNER)
+			ret = kdbus_handle_ioctl_ep_owner(file, cmd, argp);
+		else if (handle->type == KDBUS_HANDLE_CONNECTED)
+			ret = kdbus_handle_ioctl_connected(file, cmd, argp);
+		up_read(&handle->rwlock);
+		break;
+	default:
+		ret = -ENOTTY;
+		break;
+	}
+
+	return ret < 0 ? ret : 0;
+}
+
+static unsigned int kdbus_handle_poll(struct file *file,
+				      struct poll_table_struct *wait)
+{
+	struct kdbus_handle *handle = file->private_data;
+	unsigned int mask = POLLOUT | POLLWRNORM;
+	int ret;
+
+	/* Only a connected endpoint can read/write data */
+	down_read(&handle->rwlock);
+	if (handle->type != KDBUS_HANDLE_CONNECTED) {
+		up_read(&handle->rwlock);
+		return POLLERR | POLLHUP;
+	}
+	up_read(&handle->rwlock);
+
+	ret = kdbus_conn_acquire(handle->conn);
+	if (ret < 0)
+		return POLLERR | POLLHUP;
+
+	poll_wait(file, &handle->conn->wait, wait);
+
+	if (!list_empty(&handle->conn->queue.msg_list) ||
+	    atomic_read(&handle->conn->lost_count) > 0)
+		mask |= POLLIN | POLLRDNORM;
+
+	kdbus_conn_release(handle->conn);
+
+	return mask;
+}
+
+static int kdbus_handle_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct kdbus_handle *handle = file->private_data;
+	int ret = -EBADFD;
+
+	if (down_read_trylock(&handle->rwlock)) {
+		if (handle->type == KDBUS_HANDLE_CONNECTED)
+			ret = kdbus_pool_mmap(handle->conn->pool, vma);
+		up_read(&handle->rwlock);
+	}
+	return ret;
+}
+
+const struct file_operations kdbus_handle_ops = {
+	.owner =		THIS_MODULE,
+	.open =			kdbus_handle_open,
+	.release =		kdbus_handle_release,
+	.poll =			kdbus_handle_poll,
+	.llseek =		noop_llseek,
+	.unlocked_ioctl =	kdbus_handle_ioctl,
+	.mmap =			kdbus_handle_mmap,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl =		kdbus_handle_ioctl,
+#endif
+};
diff --git a/ipc/kdbus/handle.h b/ipc/kdbus/handle.h
new file mode 100644
index 000000000000..93a372d554a2
--- /dev/null
+++ b/ipc/kdbus/handle.h
@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#ifndef __KDBUS_HANDLE_H
+#define __KDBUS_HANDLE_H
+
+#include <linux/fs.h>
+#include <uapi/linux/kdbus.h>
+
+extern const struct file_operations kdbus_handle_ops;
+
+/**
+ * kdbus_arg - information and state of a single ioctl command item
+ * @type:		item type
+ * @item:		set by the parser to the first found item of this type
+ * @multiple:		whether multiple items of this type are allowed
+ * @mandatory:		whether at least one item of this type is required
+ *
+ * This structure describes a single item in an ioctl command payload. The
+ * caller has to pre-fill the type and flags, the parser will then use this
+ * information to verify the ioctl payload. @item is set by the parser to point
+ * to the first occurrence of the item.
+ */
+struct kdbus_arg {
+	u64 type;
+	struct kdbus_item *item;
+	bool multiple : 1;
+	bool mandatory : 1;
+};
+
+/**
+ * kdbus_args - information and state of ioctl command parser
+ * @allowed_flags:	set of flags this command supports
+ * @argc:		number of items in @argv
+ * @argv:		array of items this command supports
+ * @user:		set by parser to user-space location of current command
+ * @cmd:		set by parser to kernel copy of command payload
+ * @items:		points to item array in @cmd
+ * @items_size:		size of @items in bytes
+ *
+ * This structure is used to parse ioctl command payloads on each invocation.
+ * The ioctl handler has to pre-fill the flags and allowed items before passing
+ * the object to kdbus_args_parse(). The parser will copy the command payload
+ * into kernel-space and verify the correctness of the data.
+ */
+struct kdbus_args {
+	u64 allowed_flags;
+	size_t argc;
+	struct kdbus_arg *argv;
+
+	struct kdbus_cmd __user *user;
+	struct kdbus_cmd *cmd;
+
+	struct kdbus_item *items;
+	size_t items_size;
+};
+
+int __kdbus_args_parse(struct kdbus_args *args, void __user *argp,
+		       size_t type_size, size_t items_offset, void **out);
+int kdbus_args_clear(struct kdbus_args *args, int ret);
+
+#define kdbus_args_parse(_args, _argp, _v)                              \
+	({                                                              \
+		BUILD_BUG_ON(offsetof(typeof(**(_v)), size) !=          \
+			     offsetof(struct kdbus_cmd, size));         \
+		BUILD_BUG_ON(offsetof(typeof(**(_v)), flags) !=         \
+			     offsetof(struct kdbus_cmd, flags));        \
+		BUILD_BUG_ON(offsetof(typeof(**(_v)), return_flags) !=  \
+			     offsetof(struct kdbus_cmd, return_flags)); \
+		__kdbus_args_parse((_args), (_argp), sizeof(**(_v)),    \
+				   offsetof(typeof(**(_v)), items),     \
+				   (void **)(_v));                      \
+	})
+
+#endif
diff --git a/ipc/kdbus/limits.h b/ipc/kdbus/limits.h
new file mode 100644
index 000000000000..6450f58cffcf
--- /dev/null
+++ b/ipc/kdbus/limits.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#ifndef __KDBUS_DEFAULTS_H
+#define __KDBUS_DEFAULTS_H
+
+#include <linux/kernel.h>
+
+/* maximum size of message header and items */
+#define KDBUS_MSG_MAX_SIZE		SZ_8K
+
+/* maximum number of message items */
+#define KDBUS_MSG_MAX_ITEMS		128
+
+/* maximum number of memfd items per message */
+#define KDBUS_MSG_MAX_MEMFD_ITEMS	16
+
+/* max size of ioctl command data */
+#define KDBUS_CMD_MAX_SIZE		SZ_32K
+
+/* maximum number of inflight fds in a target queue per user */
+#define KDBUS_CONN_MAX_FDS_PER_USER	16
+
+/* maximum message payload size */
+#define KDBUS_MSG_MAX_PAYLOAD_VEC_SIZE		SZ_2M
+
+/* maximum size of bloom bit field in bytes */
+#define KDBUS_BUS_BLOOM_MAX_SIZE		SZ_4K
+
+/* maximum length of well-known bus name */
+#define KDBUS_NAME_MAX_LEN			255
+
+/* maximum length of bus, domain, ep name */
+#define KDBUS_SYSNAME_MAX_LEN			63
+
+/* maximum number of matches per connection */
+#define KDBUS_MATCH_MAX				256
+
+/* maximum number of queued messages from the same individual user */
+#define KDBUS_CONN_MAX_MSGS			256
+
+/* maximum number of well-known names per connection */
+#define KDBUS_CONN_MAX_NAMES			256
+
+/* maximum number of queued requests waiting for a reply */
+#define KDBUS_CONN_MAX_REQUESTS_PENDING		128
+
+/* maximum number of connections per user in one domain */
+#define KDBUS_USER_MAX_CONN			1024
+
+/* maximum number of buses per user in one domain */
+#define KDBUS_USER_MAX_BUSES			16
+
+#endif
diff --git a/ipc/kdbus/main.c b/ipc/kdbus/main.c
new file mode 100644
index 000000000000..785f529d98b7
--- /dev/null
+++ b/ipc/kdbus/main.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#define pr_fmt(fmt)    KBUILD_MODNAME ": " fmt
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+#include "util.h"
+#include "fs.h"
+#include "handle.h"
+#include "metadata.h"
+#include "node.h"
+
+/*
+ * This is a simplified outline of the internal kdbus object relations, for
+ * those interested in the inner life of the driver implementation.
+ *
+ * From a mount point's (domain's) perspective:
+ *
+ * struct kdbus_domain
+ *   |» struct kdbus_user *user (many, owned)
+ *   '» struct kdbus_node node (embedded)
+ *       |» struct kdbus_node children (many, referenced)
+ *       |» struct kdbus_node *parent (pinned)
+ *       '» struct kdbus_bus (many, pinned)
+ *           |» struct kdbus_node node (embedded)
+ *           '» struct kdbus_ep (many, pinned)
+ *               |» struct kdbus_node node (embedded)
+ *               |» struct kdbus_bus *bus (pinned)
+ *               |» struct kdbus_conn conn_list (many, pinned)
+ *               |   |» struct kdbus_ep *ep (pinned)
+ *               |   |» struct kdbus_name_entry *activator_of (owned)
+ *               |   |» struct kdbus_match_db *match_db (owned)
+ *               |   |» struct kdbus_meta *meta (owned)
+ *               |   |» struct kdbus_match_db *match_db (owned)
+ *               |   |    '» struct kdbus_match_entry (many, owned)
+ *               |   |
+ *               |   |» struct kdbus_pool *pool (owned)
+ *               |   |    '» struct kdbus_pool_slice *slices (many, owned)
+ *               |   |       '» struct kdbus_pool *pool (pinned)
+ *               |   |
+ *               |   |» struct kdbus_user *user (pinned)
+ *               |   `» struct kdbus_queue_entry entries (many, embedded)
+ *               |        |» struct kdbus_pool_slice *slice (pinned)
+ *               |        |» struct kdbus_conn_reply *reply (owned)
+ *               |        '» struct kdbus_user *user (pinned)
+ *               |
+ *               '» struct kdbus_user *user (pinned)
+ *                   '» struct kdbus_policy_db policy_db (embedded)
+ *                        |» struct kdbus_policy_db_entry (many, owned)
+ *                        |   |» struct kdbus_conn (pinned)
+ *                        |   '» struct kdbus_ep (pinned)
+ *                        |
+ *                        '» struct kdbus_policy_db_cache_entry (many, owned)
+ *                            '» struct kdbus_conn (pinned)
+ *
+ * For the life-time of a file descriptor derived from calling open() on a file
+ * inside the mount point:
+ *
+ * struct kdbus_handle
+ *  |» struct kdbus_meta *meta (owned)
+ *  |» struct kdbus_ep *ep (pinned)
+ *  |» struct kdbus_conn *conn (owned)
+ *  '» struct kdbus_ep *ep (owned)
+ */
+
+/* kdbus mount-point /sys/fs/kdbus */
+static struct kobject *kdbus_dir;
+
+/* global module option to apply a mask to exported metadata */
+unsigned long long kdbus_meta_attach_mask = KDBUS_ATTACH_TIMESTAMP |
+					    KDBUS_ATTACH_CREDS |
+					    KDBUS_ATTACH_PIDS |
+					    KDBUS_ATTACH_AUXGROUPS |
+					    KDBUS_ATTACH_NAMES |
+					    KDBUS_ATTACH_SECLABEL |
+					    KDBUS_ATTACH_CONN_DESCRIPTION;
+MODULE_PARM_DESC(attach_flags_mask, "Attach-flags mask for exported metadata");
+module_param_named(attach_flags_mask, kdbus_meta_attach_mask, ullong, 0644);
+
+static int __init kdbus_init(void)
+{
+	int ret;
+
+	kdbus_dir = kobject_create_and_add(KBUILD_MODNAME, fs_kobj);
+	if (!kdbus_dir)
+		return -ENOMEM;
+
+	ret = kdbus_fs_init();
+	if (ret < 0) {
+		pr_err("cannot register filesystem: %d\n", ret);
+		goto exit_dir;
+	}
+
+	pr_info("initialized\n");
+	return 0;
+
+exit_dir:
+	kobject_put(kdbus_dir);
+	return ret;
+}
+
+static void __exit kdbus_exit(void)
+{
+	kdbus_fs_exit();
+	kobject_put(kdbus_dir);
+}
+
+module_init(kdbus_init);
+module_exit(kdbus_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("D-Bus, powerful, easy to use interprocess communication");
+MODULE_ALIAS_FS(KBUILD_MODNAME "fs");
diff --git a/ipc/kdbus/util.c b/ipc/kdbus/util.c
new file mode 100644
index 000000000000..eaa806a27997
--- /dev/null
+++ b/ipc/kdbus/util.c
@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@opendz.org>
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#include <linux/capability.h>
+#include <linux/cred.h>
+#include <linux/ctype.h>
+#include <linux/err.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <linux/uio.h>
+#include <linux/user_namespace.h>
+
+#include "limits.h"
+#include "util.h"
+
+/**
+ * kdbus_copy_from_user() - copy aligned data from user-space
+ * @dest:	target buffer in kernel memory
+ * @user_ptr:	user-provided source buffer
+ * @size:	memory size to copy from user
+ *
+ * This copies @size bytes from @user_ptr into the kernel, just like
+ * copy_from_user() does. But we enforce an 8-byte alignment and reject any
+ * unaligned user-space pointers.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kdbus_copy_from_user(void *dest, void __user *user_ptr, size_t size)
+{
+	if (!KDBUS_IS_ALIGNED8((uintptr_t)user_ptr))
+		return -EFAULT;
+
+	if (copy_from_user(dest, user_ptr, size))
+		return -EFAULT;
+
+	return 0;
+}
+
+/**
+ * kdbus_memdup_user() - copy dynamically sized object from user-space
+ * @user_ptr:	user-provided source buffer
+ * @sz_min:	minimum object size
+ * @sz_max:	maximum object size
+ *
+ * This copies a dynamically sized object from user-space into kernel-space. We
+ * require the object to have a 64bit size field at offset 0. We read it out
+ * first, allocate a suitably sized buffer and then copy all data.
+ *
+ * The @sz_min and @sz_max parameters define possible min and max object sizes
+ * so user-space cannot trigger un-bound kernel-space allocations.
+ *
+ * The same alignment-restrictions as described in kdbus_copy_from_user() apply.
+ *
+ * Return: pointer to dynamically allocated copy, or ERR_PTR() on failure.
+ */
+void *kdbus_memdup_user(void __user *user_ptr, size_t sz_min, size_t sz_max)
+{
+	void *ptr;
+	u64 size;
+	int ret;
+
+	ret = kdbus_copy_from_user(&size, user_ptr, sizeof(size));
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	if (size < sz_min)
+		return ERR_PTR(-EINVAL);
+
+	if (size > sz_max)
+		return ERR_PTR(-EMSGSIZE);
+
+	ptr = memdup_user(user_ptr, size);
+	if (IS_ERR(ptr))
+		return ptr;
+
+	if (*(u64 *)ptr != size) {
+		kfree(ptr);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return ptr;
+}
+
+/**
+ * kdbus_verify_uid_prefix() - verify UID prefix of a user-supplied name
+ * @name:	user-supplied name to verify
+ * @user_ns:	user-namespace to act in
+ * @kuid:	Kernel internal uid of user
+ *
+ * This verifies that the user-supplied name @name has their UID as prefix. This
+ * is the default name-spacing policy we enforce on user-supplied names for
+ * public kdbus entities like buses and endpoints.
+ *
+ * The user must supply names prefixed with "<UID>-", whereas the UID is
+ * interpreted in the user-namespace of the domain. If the user fails to supply
+ * such a prefixed name, we reject it.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int kdbus_verify_uid_prefix(const char *name, struct user_namespace *user_ns,
+			    kuid_t kuid)
+{
+	uid_t uid;
+	char prefix[16];
+
+	/*
+	 * The kuid must have a mapping into the userns of the domain
+	 * otherwise do not allow creation of buses nor endpoints.
+	 */
+	uid = from_kuid(user_ns, kuid);
+	if (uid == (uid_t) -1)
+		return -EINVAL;
+
+	snprintf(prefix, sizeof(prefix), "%u-", uid);
+	if (strncmp(name, prefix, strlen(prefix)) != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * kdbus_sanitize_attach_flags() - Sanitize attach flags from user-space
+ * @flags:		Attach flags provided by userspace
+ * @attach_flags:	A pointer where to store the valid attach flags
+ *
+ * Convert attach-flags provided by user-space into a valid mask. If the mask
+ * is invalid, an error is returned. The sanitized attach flags are stored in
+ * the output parameter.
+ *
+ * Return: 0 on success, negative error on failure.
+ */
+int kdbus_sanitize_attach_flags(u64 flags, u64 *attach_flags)
+{
+	/* 'any' degrades to 'all' for compatibility */
+	if (flags == _KDBUS_ATTACH_ANY)
+		flags = _KDBUS_ATTACH_ALL;
+
+	/* reject unknown attach flags */
+	if (flags & ~_KDBUS_ATTACH_ALL)
+		return -EINVAL;
+
+	*attach_flags = flags;
+	return 0;
+}
+
+/**
+ * kdbus_kvec_set - helper utility to assemble kvec arrays
+ * @kvec:	kvec entry to use
+ * @src:	Source address to set in @kvec
+ * @len:	Number of bytes in @src
+ * @total_len:	Pointer to total length variable
+ *
+ * Set @src and @len in @kvec, and increase @total_len by @len.
+ */
+void kdbus_kvec_set(struct kvec *kvec, void *src, size_t len, u64 *total_len)
+{
+	kvec->iov_base = src;
+	kvec->iov_len = len;
+	*total_len += len;
+}
+
+static const char * const zeros = "\0\0\0\0\0\0\0";
+
+/**
+ * kdbus_kvec_pad - conditionally write a padding kvec
+ * @kvec:	kvec entry to use
+ * @len:	Total length used for kvec array
+ *
+ * Check if the current total byte length of the array in @len is aligned to
+ * 8 bytes. If it isn't, fill @kvec with padding information and increase @len
+ * by the number of bytes stored in @kvec.
+ *
+ * Return: the number of added padding bytes.
+ */
+size_t kdbus_kvec_pad(struct kvec *kvec, u64 *len)
+{
+	size_t pad = KDBUS_ALIGN8(*len) - *len;
+
+	if (!pad)
+		return 0;
+
+	kvec->iov_base = (void *)zeros;
+	kvec->iov_len = pad;
+
+	*len += pad;
+
+	return pad;
+}
diff --git a/ipc/kdbus/util.h b/ipc/kdbus/util.h
new file mode 100644
index 000000000000..9caadb337912
--- /dev/null
+++ b/ipc/kdbus/util.h
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@opendz.org>
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#ifndef __KDBUS_UTIL_H
+#define __KDBUS_UTIL_H
+
+#include <linux/dcache.h>
+#include <linux/ioctl.h>
+
+#include "kdbus.h"
+
+/* all exported addresses are 64 bit */
+#define KDBUS_PTR(addr) ((void __user *)(uintptr_t)(addr))
+
+/* all exported sizes are 64 bit and data aligned to 64 bit */
+#define KDBUS_ALIGN8(s) ALIGN((s), 8)
+#define KDBUS_IS_ALIGNED8(s) (IS_ALIGNED(s, 8))
+
+/**
+ * kdbus_member_set_user - write a structure member to user memory
+ * @_s:		Variable to copy from
+ * @_b:		Buffer to write to
+ * @_t:		Structure type
+ * @_m:		Member name in the passed structure
+ *
+ * Return: the result of copy_to_user()
+ */
+#define kdbus_member_set_user(_s, _b, _t, _m)				\
+({									\
+	u64 __user *_sz =						\
+		(void __user *)((u8 __user *)(_b) + offsetof(_t, _m));	\
+	copy_to_user(_sz, _s, sizeof(((_t *)0)->_m));			\
+})
+
+/**
+ * kdbus_strhash - calculate a hash
+ * @str:	String
+ *
+ * Return: hash value
+ */
+static inline unsigned int kdbus_strhash(const char *str)
+{
+	unsigned long hash = init_name_hash();
+
+	while (*str)
+		hash = partial_name_hash(*str++, hash);
+
+	return end_name_hash(hash);
+}
+
+int kdbus_verify_uid_prefix(const char *name, struct user_namespace *user_ns,
+			    kuid_t kuid);
+int kdbus_sanitize_attach_flags(u64 flags, u64 *attach_flags);
+
+int kdbus_copy_from_user(void *dest, void __user *user_ptr, size_t size);
+void *kdbus_memdup_user(void __user *user_ptr, size_t sz_min, size_t sz_max);
+
+struct kvec;
+
+void kdbus_kvec_set(struct kvec *kvec, void *src, size_t len, u64 *total_len);
+size_t kdbus_kvec_pad(struct kvec *kvec, u64 *len);
+
+#endif