[PATCH 08/14] kdbus: add code for notifications and matches

[Greg Kroah-Hartman]

From: Daniel Mack <daniel@xxxxxxxxxx>

This patch adds code for matches and notifications.

Notifications are broadcast messages generated by the kernel, which
notify subscribes when connections are created or destroyed, when
well-known-names have been claimed, released or changed ownership,
or when reply messages have timed out.

Matches are used to tell the kernel driver which broadcast messages
a connection is interested in. Matches can either be specific on one
of the kernel-generated notification types, or carry a bloom filter
mask to match against a message from userspace. The latter is a way
to pre-filter messages from other connections in order to mitigate
unnecessary wakeups.

Signed-off-by: Daniel Mack <daniel@xxxxxxxxxx>
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
Signed-off-by: Djalal Harouni <tixxdz@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 ipc/kdbus/match.c  | 559 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 ipc/kdbus/match.h  |  35 ++++
 ipc/kdbus/notify.c | 248 ++++++++++++++++++++++++
 ipc/kdbus/notify.h |  30 +++
 4 files changed, 872 insertions(+)
 create mode 100644 ipc/kdbus/match.c
 create mode 100644 ipc/kdbus/match.h
 create mode 100644 ipc/kdbus/notify.c
 create mode 100644 ipc/kdbus/notify.h

diff --git a/ipc/kdbus/match.c b/ipc/kdbus/match.c
new file mode 100644
index 000000000000..30cec1ca819f
--- /dev/null
+++ b/ipc/kdbus/match.c
@@ -0,0 +1,559 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@xxxxxxxxxx>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@xxxxxxxxx>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@xxxxxxxxxx>
+ *
+ * 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/fs.h>
+#include <linux/hash.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "endpoint.h"
+#include "handle.h"
+#include "item.h"
+#include "match.h"
+#include "message.h"
+#include "names.h"
+
+/**
+ * struct kdbus_match_db - message filters
+ * @entries_list:	List of matches
+ * @mdb_rwlock:		Match data lock
+ * @entries_count:	Number of entries in database
+ */
+struct kdbus_match_db {
+	struct list_head entries_list;
+	struct rw_semaphore mdb_rwlock;
+	unsigned int entries_count;
+};
+
+/**
+ * struct kdbus_match_entry - a match database entry
+ * @cookie:		User-supplied cookie to lookup the entry
+ * @list_entry:		The list entry element for the db list
+ * @rules_list:		The list head for tracking rules of this entry
+ */
+struct kdbus_match_entry {
+	u64 cookie;
+	struct list_head list_entry;
+	struct list_head rules_list;
+};
+
+/**
+ * struct kdbus_bloom_mask - mask to match against filter
+ * @generations:	Number of generations carried
+ * @data:		Array of bloom bit fields
+ */
+struct kdbus_bloom_mask {
+	u64 generations;
+	u64 *data;
+};
+
+/**
+ * struct kdbus_match_rule - a rule appended to a match entry
+ * @type:		An item type to match agains
+ * @bloom_mask:		Bloom mask to match a message's filter against, used
+ *			with KDBUS_ITEM_BLOOM_MASK
+ * @name:		Name to match against, used with KDBUS_ITEM_NAME,
+ *			KDBUS_ITEM_NAME_{ADD,REMOVE,CHANGE}
+ * @old_id:		ID to match against, used with
+ *			KDBUS_ITEM_NAME_{ADD,REMOVE,CHANGE},
+ *			KDBUS_ITEM_ID_REMOVE
+ * @new_id:		ID to match against, used with
+ *			KDBUS_ITEM_NAME_{ADD,REMOVE,CHANGE},
+ *			KDBUS_ITEM_ID_REMOVE
+ * @src_id:		ID to match against, used with KDBUS_ITEM_ID
+ * @rules_entry:	Entry in the entry's rules list
+ */
+struct kdbus_match_rule {
+	u64 type;
+	union {
+		struct kdbus_bloom_mask bloom_mask;
+		struct {
+			char *name;
+			u64 old_id;
+			u64 new_id;
+		};
+		u64 src_id;
+	};
+	struct list_head rules_entry;
+};
+
+static void kdbus_match_rule_free(struct kdbus_match_rule *rule)
+{
+	if (!rule)
+		return;
+
+	switch (rule->type) {
+	case KDBUS_ITEM_BLOOM_MASK:
+		kfree(rule->bloom_mask.data);
+		break;
+
+	case KDBUS_ITEM_NAME:
+	case KDBUS_ITEM_NAME_ADD:
+	case KDBUS_ITEM_NAME_REMOVE:
+	case KDBUS_ITEM_NAME_CHANGE:
+		kfree(rule->name);
+		break;
+
+	case KDBUS_ITEM_ID:
+	case KDBUS_ITEM_ID_ADD:
+	case KDBUS_ITEM_ID_REMOVE:
+		break;
+
+	default:
+		BUG();
+	}
+
+	list_del(&rule->rules_entry);
+	kfree(rule);
+}
+
+static void kdbus_match_entry_free(struct kdbus_match_entry *entry)
+{
+	struct kdbus_match_rule *r, *tmp;
+
+	if (!entry)
+		return;
+
+	list_for_each_entry_safe(r, tmp, &entry->rules_list, rules_entry)
+		kdbus_match_rule_free(r);
+
+	list_del(&entry->list_entry);
+	kfree(entry);
+}
+
+/**
+ * kdbus_match_db_free() - free match db resources
+ * @mdb:		The match database
+ */
+void kdbus_match_db_free(struct kdbus_match_db *mdb)
+{
+	struct kdbus_match_entry *entry, *tmp;
+
+	if (!mdb)
+		return;
+
+	list_for_each_entry_safe(entry, tmp, &mdb->entries_list, list_entry)
+		kdbus_match_entry_free(entry);
+
+	kfree(mdb);
+}
+
+/**
+ * kdbus_match_db_new() - create a new match database
+ *
+ * Return: a new kdbus_match_db on success, ERR_PTR on failure.
+ */
+struct kdbus_match_db *kdbus_match_db_new(void)
+{
+	struct kdbus_match_db *d;
+
+	d = kzalloc(sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return ERR_PTR(-ENOMEM);
+
+	init_rwsem(&d->mdb_rwlock);
+	INIT_LIST_HEAD(&d->entries_list);
+
+	return d;
+}
+
+static bool kdbus_match_bloom(const struct kdbus_bloom_filter *filter,
+			      const struct kdbus_bloom_mask *mask,
+			      const struct kdbus_conn *conn)
+{
+	size_t n = conn->ep->bus->bloom.size / sizeof(u64);
+	const u64 *m;
+	size_t i;
+
+	/*
+	 * The message's filter carries a generation identifier, the
+	 * match's mask possibly carries an array of multiple generations
+	 * of the mask. Select the mask with the closest match of the
+	 * filter's generation.
+	 */
+	m = mask->data + (min(filter->generation, mask->generations - 1) * n);
+
+	/*
+	 * The message's filter contains the messages properties,
+	 * the match's mask contains the properties to look for in the
+	 * message. Check the mask bit field against the filter bit field,
+	 * if the message possibly carries the properties the connection
+	 * has subscribed to.
+	 */
+	for (i = 0; i < n; i++)
+		if ((filter->data[i] & m[i]) != m[i])
+			return false;
+
+	return true;
+}
+
+static bool kdbus_match_rules(const struct kdbus_match_entry *entry,
+			      struct kdbus_conn *conn_src,
+			      struct kdbus_kmsg *kmsg)
+{
+	struct kdbus_match_rule *r;
+
+	if (conn_src)
+		lockdep_assert_held(&conn_src->ep->bus->name_registry->rwlock);
+
+	/*
+	 * Walk all the rules and bail out immediately
+	 * if any of them is unsatisfied.
+	 */
+
+	list_for_each_entry(r, &entry->rules_list, rules_entry) {
+		if (conn_src) {
+			/* messages from userspace */
+
+			switch (r->type) {
+			case KDBUS_ITEM_BLOOM_MASK:
+				if (!kdbus_match_bloom(kmsg->bloom_filter,
+						       &r->bloom_mask,
+						       conn_src))
+					return false;
+				break;
+
+			case KDBUS_ITEM_ID:
+				if (r->src_id != conn_src->id &&
+				    r->src_id != KDBUS_MATCH_ID_ANY)
+					return false;
+
+				break;
+
+			case KDBUS_ITEM_NAME:
+				if (!kdbus_conn_has_name(conn_src, r->name))
+					return false;
+
+				break;
+
+			default:
+				return false;
+			}
+		} else {
+			/* kernel notifications */
+
+			if (kmsg->notify_type != r->type)
+				return false;
+
+			switch (r->type) {
+			case KDBUS_ITEM_ID_ADD:
+				if (r->new_id != KDBUS_MATCH_ID_ANY &&
+				    r->new_id != kmsg->notify_new_id)
+					return false;
+
+				break;
+
+			case KDBUS_ITEM_ID_REMOVE:
+				if (r->old_id != KDBUS_MATCH_ID_ANY &&
+				    r->old_id != kmsg->notify_old_id)
+					return false;
+
+				break;
+
+			case KDBUS_ITEM_NAME_ADD:
+			case KDBUS_ITEM_NAME_CHANGE:
+			case KDBUS_ITEM_NAME_REMOVE:
+				if ((r->old_id != KDBUS_MATCH_ID_ANY &&
+				     r->old_id != kmsg->notify_old_id) ||
+				    (r->new_id != KDBUS_MATCH_ID_ANY &&
+				     r->new_id != kmsg->notify_new_id) ||
+				    (r->name && kmsg->notify_name &&
+				     strcmp(r->name, kmsg->notify_name) != 0))
+					return false;
+
+				break;
+
+			default:
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+/**
+ * kdbus_match_db_match_kmsg() - match a kmsg object agains the database entries
+ * @mdb:		The match database
+ * @conn_src:		The connection object originating the message
+ * @kmsg:		The kmsg to perform the match on
+ *
+ * This function will walk through all the database entries previously uploaded
+ * with kdbus_match_db_add(). As soon as any of them has an all-satisfied rule
+ * set, this function will return true.
+ *
+ * The caller must hold the registry lock of conn_src->ep->bus, in case conn_src
+ * is non-NULL.
+ *
+ * Return: true if there was a matching database entry, false otherwise.
+ */
+bool kdbus_match_db_match_kmsg(struct kdbus_match_db *mdb,
+			       struct kdbus_conn *conn_src,
+			       struct kdbus_kmsg *kmsg)
+{
+	struct kdbus_match_entry *entry;
+	bool matched = false;
+
+	down_read(&mdb->mdb_rwlock);
+	list_for_each_entry(entry, &mdb->entries_list, list_entry) {
+		matched = kdbus_match_rules(entry, conn_src, kmsg);
+		if (matched)
+			break;
+	}
+	up_read(&mdb->mdb_rwlock);
+
+	return matched;
+}
+
+static int kdbus_match_db_remove_unlocked(struct kdbus_match_db *mdb,
+					  u64 cookie)
+{
+	struct kdbus_match_entry *entry, *tmp;
+	bool found = false;
+
+	list_for_each_entry_safe(entry, tmp, &mdb->entries_list, list_entry)
+		if (entry->cookie == cookie) {
+			kdbus_match_entry_free(entry);
+			--mdb->entries_count;
+			found = true;
+		}
+
+	return found ? 0 : -EBADSLT;
+}
+
+/**
+ * kdbus_cmd_match_add() - handle KDBUS_CMD_MATCH_ADD
+ * @conn:		connection to operate on
+ * @argp:		command payload
+ *
+ * One call to this function (or one ioctl(KDBUS_CMD_MATCH_ADD), respectively,
+ * adds one new database entry with n rules attached to it. Each rule is
+ * described with an kdbus_item, and an entry is considered matching if all
+ * its rules are satisfied.
+ *
+ * The items attached to a kdbus_cmd_match struct have the following mapping:
+ *
+ * KDBUS_ITEM_BLOOM_MASK:	A bloom mask
+ * KDBUS_ITEM_NAME:		A connection's source name
+ * KDBUS_ITEM_ID:		A connection ID
+ * KDBUS_ITEM_NAME_ADD:
+ * KDBUS_ITEM_NAME_REMOVE:
+ * KDBUS_ITEM_NAME_CHANGE:	Well-known name changes, carry
+ *				kdbus_notify_name_change
+ * KDBUS_ITEM_ID_ADD:
+ * KDBUS_ITEM_ID_REMOVE:	Connection ID changes, carry
+ *				kdbus_notify_id_change
+ *
+ * For kdbus_notify_{id,name}_change structs, only the ID and name fields
+ * are looked at when adding an entry. The flags are unused.
+ *
+ * Also note that KDBUS_ITEM_BLOOM_MASK, KDBUS_ITEM_NAME and KDBUS_ITEM_ID
+ * are used to match messages from userspace, while the others apply to
+ * kernel-generated notifications.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kdbus_cmd_match_add(struct kdbus_conn *conn, void __user *argp)
+{
+	struct kdbus_match_db *mdb = conn->match_db;
+	struct kdbus_match_entry *entry = NULL;
+	struct kdbus_cmd_match *cmd;
+	struct kdbus_item *item;
+	int ret;
+
+	struct kdbus_arg argv[] = {
+		{ .type = KDBUS_ITEM_NEGOTIATE },
+		{ .type = KDBUS_ITEM_BLOOM_MASK, .multiple = true },
+		{ .type = KDBUS_ITEM_NAME, .multiple = true },
+		{ .type = KDBUS_ITEM_ID, .multiple = true },
+		{ .type = KDBUS_ITEM_NAME_ADD, .multiple = true },
+		{ .type = KDBUS_ITEM_NAME_REMOVE, .multiple = true },
+		{ .type = KDBUS_ITEM_NAME_CHANGE, .multiple = true },
+		{ .type = KDBUS_ITEM_ID_ADD, .multiple = true },
+		{ .type = KDBUS_ITEM_ID_REMOVE, .multiple = true },
+	};
+	struct kdbus_args args = {
+		.allowed_flags = KDBUS_FLAG_NEGOTIATE |
+				 KDBUS_MATCH_REPLACE,
+		.argv = argv,
+		.argc = ARRAY_SIZE(argv),
+	};
+
+	if (!kdbus_conn_is_ordinary(conn))
+		return -EOPNOTSUPP;
+
+	ret = kdbus_args_parse(&args, argp, &cmd);
+	if (ret != 0)
+		return ret;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	entry->cookie = cmd->cookie;
+	INIT_LIST_HEAD(&entry->list_entry);
+	INIT_LIST_HEAD(&entry->rules_list);
+
+	KDBUS_ITEMS_FOREACH(item, cmd->items, KDBUS_ITEMS_SIZE(cmd, items)) {
+		struct kdbus_match_rule *rule;
+		size_t size = item->size - offsetof(struct kdbus_item, data);
+
+		rule = kzalloc(sizeof(*rule), GFP_KERNEL);
+		if (!rule) {
+			ret = -ENOMEM;
+			goto exit;
+		}
+
+		rule->type = item->type;
+		INIT_LIST_HEAD(&rule->rules_entry);
+
+		switch (item->type) {
+		case KDBUS_ITEM_BLOOM_MASK: {
+			u64 bsize = conn->ep->bus->bloom.size;
+			u64 generations;
+			u64 remainder;
+
+			generations = div64_u64_rem(size, bsize, &remainder);
+			if (size < bsize || remainder > 0) {
+				ret = -EDOM;
+				break;
+			}
+
+			rule->bloom_mask.data = kmemdup(item->data,
+							size, GFP_KERNEL);
+			if (!rule->bloom_mask.data) {
+				ret = -ENOMEM;
+				break;
+			}
+
+			rule->bloom_mask.generations = generations;
+			break;
+		}
+
+		case KDBUS_ITEM_NAME:
+			if (!kdbus_name_is_valid(item->str, false)) {
+				ret = -EINVAL;
+				break;
+			}
+
+			rule->name = kstrdup(item->str, GFP_KERNEL);
+			if (!rule->name)
+				ret = -ENOMEM;
+
+			break;
+
+		case KDBUS_ITEM_ID:
+			rule->src_id = item->id;
+			break;
+
+		case KDBUS_ITEM_NAME_ADD:
+		case KDBUS_ITEM_NAME_REMOVE:
+		case KDBUS_ITEM_NAME_CHANGE:
+			rule->old_id = item->name_change.old_id.id;
+			rule->new_id = item->name_change.new_id.id;
+
+			if (size > sizeof(struct kdbus_notify_name_change)) {
+				rule->name = kstrdup(item->name_change.name,
+						     GFP_KERNEL);
+				if (!rule->name)
+					ret = -ENOMEM;
+			}
+
+			break;
+
+		case KDBUS_ITEM_ID_ADD:
+		case KDBUS_ITEM_ID_REMOVE:
+			if (item->type == KDBUS_ITEM_ID_ADD)
+				rule->new_id = item->id_change.id;
+			else
+				rule->old_id = item->id_change.id;
+
+			break;
+		}
+
+		if (ret < 0) {
+			kdbus_match_rule_free(rule);
+			goto exit;
+		}
+
+		list_add_tail(&rule->rules_entry, &entry->rules_list);
+	}
+
+	down_write(&mdb->mdb_rwlock);
+
+	/* Remove any entry that has the same cookie as the current one. */
+	if (cmd->flags & KDBUS_MATCH_REPLACE)
+		kdbus_match_db_remove_unlocked(mdb, entry->cookie);
+
+	/*
+	 * If the above removal caught any entry, there will be room for the
+	 * new one.
+	 */
+	if (++mdb->entries_count > KDBUS_MATCH_MAX) {
+		--mdb->entries_count;
+		ret = -EMFILE;
+	} else {
+		list_add_tail(&entry->list_entry, &mdb->entries_list);
+		entry = NULL;
+	}
+
+	up_write(&mdb->mdb_rwlock);
+
+exit:
+	kdbus_match_entry_free(entry);
+	return kdbus_args_clear(&args, ret);
+}
+
+/**
+ * kdbus_cmd_match_remove() - handle KDBUS_CMD_MATCH_REMOVE
+ * @conn:		connection to operate on
+ * @argp:		command payload
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kdbus_cmd_match_remove(struct kdbus_conn *conn, void __user *argp)
+{
+	struct kdbus_cmd_match *cmd;
+	int ret;
+
+	struct kdbus_arg argv[] = {
+		{ .type = KDBUS_ITEM_NEGOTIATE },
+	};
+	struct kdbus_args args = {
+		.allowed_flags = KDBUS_FLAG_NEGOTIATE,
+		.argv = argv,
+		.argc = ARRAY_SIZE(argv),
+	};
+
+	if (!kdbus_conn_is_ordinary(conn))
+		return -EOPNOTSUPP;
+
+	ret = kdbus_args_parse(&args, argp, &cmd);
+	if (ret != 0)
+		return ret;
+
+	down_write(&conn->match_db->mdb_rwlock);
+	ret = kdbus_match_db_remove_unlocked(conn->match_db, cmd->cookie);
+	up_write(&conn->match_db->mdb_rwlock);
+
+	return kdbus_args_clear(&args, ret);
+}
diff --git a/ipc/kdbus/match.h b/ipc/kdbus/match.h
new file mode 100644
index 000000000000..ea4292938deb
--- /dev/null
+++ b/ipc/kdbus/match.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@xxxxxxxxxx>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@xxxxxxxxx>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@xxxxxxxxxx>
+ *
+ * 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_MATCH_H
+#define __KDBUS_MATCH_H
+
+struct kdbus_conn;
+struct kdbus_kmsg;
+struct kdbus_match_db;
+
+struct kdbus_match_db *kdbus_match_db_new(void);
+void kdbus_match_db_free(struct kdbus_match_db *db);
+int kdbus_match_db_add(struct kdbus_conn *conn,
+		       struct kdbus_cmd_match *cmd);
+int kdbus_match_db_remove(struct kdbus_conn *conn,
+			  struct kdbus_cmd_match *cmd);
+bool kdbus_match_db_match_kmsg(struct kdbus_match_db *db,
+			       struct kdbus_conn *conn_src,
+			       struct kdbus_kmsg *kmsg);
+
+int kdbus_cmd_match_add(struct kdbus_conn *conn, void __user *argp);
+int kdbus_cmd_match_remove(struct kdbus_conn *conn, void __user *argp);
+
+#endif
diff --git a/ipc/kdbus/notify.c b/ipc/kdbus/notify.c
new file mode 100644
index 000000000000..e4a454222f09
--- /dev/null
+++ b/ipc/kdbus/notify.c
@@ -0,0 +1,248 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@xxxxxxxxxx>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@xxxxxxxxx>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@xxxxxxxxxx>
+ *
+ * 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/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "domain.h"
+#include "endpoint.h"
+#include "item.h"
+#include "message.h"
+#include "notify.h"
+
+static inline void kdbus_notify_add_tail(struct kdbus_kmsg *kmsg,
+					 struct kdbus_bus *bus)
+{
+	spin_lock(&bus->notify_lock);
+	list_add_tail(&kmsg->notify_entry, &bus->notify_list);
+	spin_unlock(&bus->notify_lock);
+}
+
+static int kdbus_notify_reply(struct kdbus_bus *bus, u64 id,
+			      u64 cookie, u64 msg_type)
+{
+	struct kdbus_kmsg *kmsg = NULL;
+
+	WARN_ON(id == 0);
+
+	kmsg = kdbus_kmsg_new(bus, 0);
+	if (IS_ERR(kmsg))
+		return PTR_ERR(kmsg);
+
+	/*
+	 * a kernel-generated notification can only contain one
+	 * struct kdbus_item, so make a shortcut here for
+	 * faster lookup in the match db.
+	 */
+	kmsg->notify_type = msg_type;
+	kmsg->msg.flags = KDBUS_MSG_SIGNAL;
+	kmsg->msg.dst_id = id;
+	kmsg->msg.src_id = KDBUS_SRC_ID_KERNEL;
+	kmsg->msg.payload_type = KDBUS_PAYLOAD_KERNEL;
+	kmsg->msg.cookie_reply = cookie;
+	kmsg->msg.items[0].type = msg_type;
+
+	kdbus_notify_add_tail(kmsg, bus);
+
+	return 0;
+}
+
+/**
+ * kdbus_notify_reply_timeout() - queue a timeout reply
+ * @bus:		Bus which queues the messages
+ * @id:			The destination's connection ID
+ * @cookie:		The cookie to set in the reply.
+ *
+ * Queues a message that has a KDBUS_ITEM_REPLY_TIMEOUT item attached.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_notify_reply_timeout(struct kdbus_bus *bus, u64 id, u64 cookie)
+{
+	return kdbus_notify_reply(bus, id, cookie, KDBUS_ITEM_REPLY_TIMEOUT);
+}
+
+/**
+ * kdbus_notify_reply_dead() - queue a 'dead' reply
+ * @bus:		Bus which queues the messages
+ * @id:			The destination's connection ID
+ * @cookie:		The cookie to set in the reply.
+ *
+ * Queues a message that has a KDBUS_ITEM_REPLY_DEAD item attached.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_notify_reply_dead(struct kdbus_bus *bus, u64 id, u64 cookie)
+{
+	return kdbus_notify_reply(bus, id, cookie, KDBUS_ITEM_REPLY_DEAD);
+}
+
+/**
+ * kdbus_notify_name_change() - queue a notification about a name owner change
+ * @bus:		Bus which queues the messages
+ * @type:		The type if the notification; KDBUS_ITEM_NAME_ADD,
+ *			KDBUS_ITEM_NAME_CHANGE or KDBUS_ITEM_NAME_REMOVE
+ * @old_id:		The id of the connection that used to own the name
+ * @new_id:		The id of the new owner connection
+ * @old_flags:		The flags to pass in the KDBUS_ITEM flags field for
+ *			the old owner
+ * @new_flags:		The flags to pass in the KDBUS_ITEM flags field for
+ *			the new owner
+ * @name:		The name that was removed or assigned to a new owner
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_notify_name_change(struct kdbus_bus *bus, u64 type,
+			     u64 old_id, u64 new_id,
+			     u64 old_flags, u64 new_flags,
+			     const char *name)
+{
+	struct kdbus_kmsg *kmsg = NULL;
+	size_t name_len, extra_size;
+
+	name_len = strlen(name) + 1;
+	extra_size = sizeof(struct kdbus_notify_name_change) + name_len;
+	kmsg = kdbus_kmsg_new(bus, extra_size);
+	if (IS_ERR(kmsg))
+		return PTR_ERR(kmsg);
+
+	kmsg->msg.flags = KDBUS_MSG_SIGNAL;
+	kmsg->msg.dst_id = KDBUS_DST_ID_BROADCAST;
+	kmsg->msg.src_id = KDBUS_SRC_ID_KERNEL;
+	kmsg->msg.payload_type = KDBUS_PAYLOAD_KERNEL;
+	kmsg->notify_type = type;
+	kmsg->notify_old_id = old_id;
+	kmsg->notify_new_id = new_id;
+	kmsg->msg.items[0].type = type;
+	kmsg->msg.items[0].name_change.old_id.id = old_id;
+	kmsg->msg.items[0].name_change.old_id.flags = old_flags;
+	kmsg->msg.items[0].name_change.new_id.id = new_id;
+	kmsg->msg.items[0].name_change.new_id.flags = new_flags;
+	memcpy(kmsg->msg.items[0].name_change.name, name, name_len);
+	kmsg->notify_name = kmsg->msg.items[0].name_change.name;
+
+	kdbus_notify_add_tail(kmsg, bus);
+
+	return 0;
+}
+
+/**
+ * kdbus_notify_id_change() - queue a notification about a unique ID change
+ * @bus:		Bus which queues the messages
+ * @type:		The type if the notification; KDBUS_ITEM_ID_ADD or
+ *			KDBUS_ITEM_ID_REMOVE
+ * @id:			The id of the connection that was added or removed
+ * @flags:		The flags to pass in the KDBUS_ITEM flags field
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_notify_id_change(struct kdbus_bus *bus, u64 type, u64 id, u64 flags)
+{
+	struct kdbus_kmsg *kmsg = NULL;
+
+	kmsg = kdbus_kmsg_new(bus, sizeof(struct kdbus_notify_id_change));
+	if (IS_ERR(kmsg))
+		return PTR_ERR(kmsg);
+
+	kmsg->msg.flags = KDBUS_MSG_SIGNAL;
+	kmsg->msg.dst_id = KDBUS_DST_ID_BROADCAST;
+	kmsg->msg.src_id = KDBUS_SRC_ID_KERNEL;
+	kmsg->msg.payload_type = KDBUS_PAYLOAD_KERNEL;
+	kmsg->notify_type = type;
+
+	switch (type) {
+	case KDBUS_ITEM_ID_ADD:
+		kmsg->notify_new_id = id;
+		break;
+
+	case KDBUS_ITEM_ID_REMOVE:
+		kmsg->notify_old_id = id;
+		break;
+
+	default:
+		BUG();
+	}
+
+	kmsg->msg.items[0].type = type;
+	kmsg->msg.items[0].id_change.id = id;
+	kmsg->msg.items[0].id_change.flags = flags;
+
+	kdbus_notify_add_tail(kmsg, bus);
+
+	return 0;
+}
+
+/**
+ * kdbus_notify_flush() - send a list of collected messages
+ * @bus:		Bus which queues the messages
+ *
+ * The list is empty after sending the messages.
+ */
+void kdbus_notify_flush(struct kdbus_bus *bus)
+{
+	LIST_HEAD(notify_list);
+	struct kdbus_kmsg *kmsg, *tmp;
+
+	mutex_lock(&bus->notify_flush_lock);
+	down_read(&bus->name_registry->rwlock);
+
+	spin_lock(&bus->notify_lock);
+	list_splice_init(&bus->notify_list, &notify_list);
+	spin_unlock(&bus->notify_lock);
+
+	list_for_each_entry_safe(kmsg, tmp, &notify_list, notify_entry) {
+		kdbus_meta_conn_collect(kmsg->conn_meta, kmsg, NULL,
+					KDBUS_ATTACH_TIMESTAMP);
+
+		if (kmsg->msg.dst_id != KDBUS_DST_ID_BROADCAST) {
+			struct kdbus_conn *conn;
+
+			conn = kdbus_bus_find_conn_by_id(bus, kmsg->msg.dst_id);
+			if (conn) {
+				kdbus_bus_eavesdrop(bus, NULL, kmsg);
+				kdbus_conn_entry_insert(NULL, conn, kmsg, NULL);
+				kdbus_conn_unref(conn);
+			}
+		} else {
+			kdbus_bus_broadcast(bus, NULL, kmsg);
+		}
+
+		list_del(&kmsg->notify_entry);
+		kdbus_kmsg_free(kmsg);
+	}
+
+	up_read(&bus->name_registry->rwlock);
+	mutex_unlock(&bus->notify_flush_lock);
+}
+
+/**
+ * kdbus_notify_free() - free a list of collected messages
+ * @bus:		Bus which queues the messages
+ */
+void kdbus_notify_free(struct kdbus_bus *bus)
+{
+	struct kdbus_kmsg *kmsg, *tmp;
+
+	list_for_each_entry_safe(kmsg, tmp, &bus->notify_list, notify_entry) {
+		list_del(&kmsg->notify_entry);
+		kdbus_kmsg_free(kmsg);
+	}
+}
diff --git a/ipc/kdbus/notify.h b/ipc/kdbus/notify.h
new file mode 100644
index 000000000000..03df464cb735
--- /dev/null
+++ b/ipc/kdbus/notify.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2013-2015 Kay Sievers
+ * Copyright (C) 2013-2015 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) 2013-2015 Daniel Mack <daniel@xxxxxxxxxx>
+ * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@xxxxxxxxx>
+ * Copyright (C) 2013-2015 Linux Foundation
+ * Copyright (C) 2014-2015 Djalal Harouni <tixxdz@xxxxxxxxxx>
+ *
+ * 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_NOTIFY_H
+#define __KDBUS_NOTIFY_H
+
+struct kdbus_bus;
+
+int kdbus_notify_id_change(struct kdbus_bus *bus, u64 type, u64 id, u64 flags);
+int kdbus_notify_reply_timeout(struct kdbus_bus *bus, u64 id, u64 cookie);
+int kdbus_notify_reply_dead(struct kdbus_bus *bus, u64 id, u64 cookie);
+int kdbus_notify_name_change(struct kdbus_bus *bus, u64 type,
+			     u64 old_id, u64 new_id,
+			     u64 old_flags, u64 new_flags,
+			     const char *name);
+void kdbus_notify_flush(struct kdbus_bus *bus);
+void kdbus_notify_free(struct kdbus_bus *bus);
+
+#endif
-- 
2.3.1

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