/******************************************************************************
 * Talks to Xen Store to figure out what devices we have.
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 * Copyright (C) 2005 Mike Wray, Hewlett-Packard
 * Copyright (C) 2005, 2006 XenSource Ltd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define dev_fmt pr_fmt

#define DPRINTK(fmt, args...)                           \
        pr_debug("xenbus_probe (%s:%d) " fmt ".\n",     \
                 __func__, __LINE__, ##args)

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/module.h>

#include <asm/page.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/xen-ops.h>
#include <xen/page.h>

#include <xen/hvm.h>

#include "xenbus.h"


static int xs_init_irq = -1;
int xen_store_evtchn;
EXPORT_SYMBOL_GPL(xen_store_evtchn);

struct xenstore_domain_interface *xen_store_interface;
EXPORT_SYMBOL_GPL(xen_store_interface);

#define XS_INTERFACE_READY \
        ((xen_store_interface != NULL) && \
         (xen_store_interface->connection == XENSTORE_CONNECTED))

enum xenstore_init xen_store_domain_type;
EXPORT_SYMBOL_GPL(xen_store_domain_type);

static unsigned long xen_store_gfn;

static BLOCKING_NOTIFIER_HEAD(xenstore_chain);

/* If something in array of ids matches this device, return it. */
static const struct xenbus_device_id *
match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
{
        for (; *arr->devicetype != '\0'; arr++) {
                if (!strcmp(arr->devicetype, dev->devicetype))
                        return arr;
        }
        return NULL;
}

int xenbus_match(struct device *_dev, const struct device_driver *_drv)
{
        const struct xenbus_driver *drv = to_xenbus_driver(_drv);

        if (!drv->ids)
                return 0;

        return match_device(drv->ids, to_xenbus_device(_dev)) != NULL;
}
EXPORT_SYMBOL_GPL(xenbus_match);


static void free_otherend_details(struct xenbus_device *dev)
{
        kfree(dev->otherend);
        dev->otherend = NULL;
}


static void free_otherend_watch(struct xenbus_device *dev)
{
        if (dev->otherend_watch.node) {
                unregister_xenbus_watch(&dev->otherend_watch);
                kfree(dev->otherend_watch.node);
                dev->otherend_watch.node = NULL;
        }
}


static int talk_to_otherend(struct xenbus_device *dev)
{
        struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);

        free_otherend_watch(dev);
        free_otherend_details(dev);

        return drv->read_otherend_details(dev);
}



static int watch_otherend(struct xenbus_device *dev)
{
        struct xen_bus_type *bus =
                container_of(dev->dev.bus, struct xen_bus_type, bus);

        return xenbus_watch_pathfmt(dev, &dev->otherend_watch,
                                    bus->otherend_will_handle,
                                    bus->otherend_changed,
                                    "%s/%s", dev->otherend, "state");
}


int xenbus_read_otherend_details(struct xenbus_device *xendev,
                                 char *id_node, char *path_node)
{
        int err = xenbus_gather(XBT_NIL, xendev->nodename,
                                id_node, "%i", &xendev->otherend_id,
                                path_node, NULL, &xendev->otherend,
                                NULL);
        if (err) {
                xenbus_dev_fatal(xendev, err,
                                 "reading other end details from %s",
                                 xendev->nodename);
                return err;
        }
        if (strlen(xendev->otherend) == 0 ||
            !xenbus_exists(XBT_NIL, xendev->otherend, "")) {
                xenbus_dev_fatal(xendev, -ENOENT,
                                 "unable to read other end from %s.  "
                                 "missing or inaccessible.",
                                 xendev->nodename);
                free_otherend_details(xendev);
                return -ENOENT;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(xenbus_read_otherend_details);

void xenbus_otherend_changed(struct xenbus_watch *watch,
                             const char *path, const char *token,
                             int ignore_on_shutdown)
{
        struct xenbus_device *dev =
                container_of(watch, struct xenbus_device, otherend_watch);
        struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
        enum xenbus_state state;

        /* Protect us against watches firing on old details when the otherend
           details change, say immediately after a resume. */
        if (!dev->otherend ||
            strncmp(dev->otherend, path, strlen(dev->otherend))) {
                dev_dbg(&dev->dev, "Ignoring watch at %s\n", path);
                return;
        }

        state = xenbus_read_driver_state(dev, dev->otherend);

        dev_dbg(&dev->dev, "state is %d, (%s), %s, %s\n",
                state, xenbus_strstate(state), dev->otherend_watch.node, path);

        /*
         * Ignore xenbus transitions during shutdown. This prevents us doing
         * work that can fail e.g., when the rootfs is gone.
         */
        if (system_state > SYSTEM_RUNNING) {
                if (ignore_on_shutdown && (state == XenbusStateClosing))
                        xenbus_frontend_closed(dev);
                return;
        }

        if (drv->otherend_changed)
                drv->otherend_changed(dev, state);
}
EXPORT_SYMBOL_GPL(xenbus_otherend_changed);

#define XENBUS_SHOW_STAT(name)                                          \
static ssize_t name##_show(struct device *_dev,                         \
                           struct device_attribute *attr,               \
                           char *buf)                                   \
{                                                                       \
        struct xenbus_device *dev = to_xenbus_device(_dev);             \
                                                                        \
        return sprintf(buf, "%d\n", atomic_read(&dev->name));           \
}                                                                       \
static DEVICE_ATTR_RO(name)

XENBUS_SHOW_STAT(event_channels);
XENBUS_SHOW_STAT(events);
XENBUS_SHOW_STAT(spurious_events);
XENBUS_SHOW_STAT(jiffies_eoi_delayed);

static ssize_t spurious_threshold_show(struct device *_dev,
                                       struct device_attribute *attr,
                                       char *buf)
{
        struct xenbus_device *dev = to_xenbus_device(_dev);

        return sprintf(buf, "%d\n", dev->spurious_threshold);
}

static ssize_t spurious_threshold_store(struct device *_dev,
                                        struct device_attribute *attr,
                                        const char *buf, size_t count)
{
        struct xenbus_device *dev = to_xenbus_device(_dev);
        unsigned int val;
        ssize_t ret;

        ret = kstrtouint(buf, 0, &val);
        if (ret)
                return ret;

        dev->spurious_threshold = val;

        return count;
}

static DEVICE_ATTR_RW(spurious_threshold);

static struct attribute *xenbus_attrs[] = {
        &dev_attr_event_channels.attr,
        &dev_attr_events.attr,
        &dev_attr_spurious_events.attr,
        &dev_attr_jiffies_eoi_delayed.attr,
        &dev_attr_spurious_threshold.attr,
        NULL
};

static const struct attribute_group xenbus_group = {
        .name = "xenbus",
        .attrs = xenbus_attrs,
};

int xenbus_dev_probe(struct device *_dev)
{
        struct xenbus_device *dev = to_xenbus_device(_dev);
        struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
        const struct xenbus_device_id *id;
        int err;

        DPRINTK("%s", dev->nodename);

        if (!drv->probe) {
                err = -ENODEV;
                goto fail;
        }

        id = match_device(drv->ids, dev);
        if (!id) {
                err = -ENODEV;
                goto fail;
        }

        err = talk_to_otherend(dev);
        if (err) {
                dev_warn(&dev->dev, "talk_to_otherend on %s failed.\n",
                         dev->nodename);
                return err;
        }

        if (!try_module_get(drv->driver.owner)) {
                dev_warn(&dev->dev, "failed to acquire module reference on '%s'\n",
                         drv->driver.name);
                err = -ESRCH;
                goto fail;
        }

        down(&dev->reclaim_sem);
        err = drv->probe(dev, id);
        up(&dev->reclaim_sem);
        if (err)
                goto fail_put;

        err = watch_otherend(dev);
        if (err) {
                dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
                       dev->nodename);
                goto fail_remove;
        }

        dev->spurious_threshold = 1;
        if (sysfs_create_group(&dev->dev.kobj, &xenbus_group))
                dev_warn(&dev->dev, "sysfs_create_group on %s failed.\n",
                         dev->nodename);

        return 0;
fail_remove:
        if (drv->remove) {
                down(&dev->reclaim_sem);
                drv->remove(dev);
                up(&dev->reclaim_sem);
        }
fail_put:
        module_put(drv->driver.owner);
fail:
        xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
        return err;
}
EXPORT_SYMBOL_GPL(xenbus_dev_probe);

void xenbus_dev_remove(struct device *_dev)
{
        struct xenbus_device *dev = to_xenbus_device(_dev);
        struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);

        DPRINTK("%s", dev->nodename);

        sysfs_remove_group(&dev->dev.kobj, &xenbus_group);

        free_otherend_watch(dev);

        if (drv->remove) {
                down(&dev->reclaim_sem);
                drv->remove(dev);
                up(&dev->reclaim_sem);
        }

        module_put(drv->driver.owner);

        free_otherend_details(dev);

        /*
         * If the toolstack has forced the device state to closing then set
         * the state to closed now to allow it to be cleaned up.
         * Similarly, if the driver does not support re-bind, set the
         * closed.
         */
        if (!drv->allow_rebind ||
            xenbus_read_driver_state(dev, dev->nodename) == XenbusStateClosing)
                xenbus_switch_state(dev, XenbusStateClosed);
}
EXPORT_SYMBOL_GPL(xenbus_dev_remove);

int xenbus_register_driver_common(struct xenbus_driver *drv,
                                  struct xen_bus_type *bus,
                                  struct module *owner, const char *mod_name)
{
        drv->driver.name = drv->name ? drv->name : drv->ids[0].devicetype;
        drv->driver.bus = &bus->bus;
        drv->driver.owner = owner;
        drv->driver.mod_name = mod_name;

        return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(xenbus_register_driver_common);

void xenbus_unregister_driver(struct xenbus_driver *drv)
{
        driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(xenbus_unregister_driver);

struct xb_find_info {
        struct xenbus_device *dev;
        const char *nodename;
};

static int cmp_dev(struct device *dev, void *data)
{
        struct xenbus_device *xendev = to_xenbus_device(dev);
        struct xb_find_info *info = data;

        if (!strcmp(xendev->nodename, info->nodename)) {
                info->dev = xendev;
                get_device(dev);
                return 1;
        }
        return 0;
}

static struct xenbus_device *xenbus_device_find(const char *nodename,
                                                struct bus_type *bus)
{
        struct xb_find_info info = { .dev = NULL, .nodename = nodename };

        bus_for_each_dev(bus, NULL, &info, cmp_dev);
        return info.dev;
}

static int cleanup_dev(struct device *dev, void *data)
{
        struct xenbus_device *xendev = to_xenbus_device(dev);
        struct xb_find_info *info = data;
        int len = strlen(info->nodename);

        DPRINTK("%s", info->nodename);

        /* Match the info->nodename path, or any subdirectory of that path. */
        if (strncmp(xendev->nodename, info->nodename, len))
                return 0;

        /* If the node name is longer, ensure it really is a subdirectory. */
        if ((strlen(xendev->nodename) > len) && (xendev->nodename[len] != '/'))
                return 0;

        info->dev = xendev;
        get_device(dev);
        return 1;
}

static void xenbus_cleanup_devices(const char *path, struct bus_type *bus)
{
        struct xb_find_info info = { .nodename = path };

        do {
                info.dev = NULL;
                bus_for_each_dev(bus, NULL, &info, cleanup_dev);
                if (info.dev) {
                        dev_warn(&info.dev->dev,
                                 "device forcefully removed from xenstore\n");
                        info.dev->vanished = true;
                        device_unregister(&info.dev->dev);
                        put_device(&info.dev->dev);
                }
        } while (info.dev);
}

static void xenbus_dev_release(struct device *dev)
{
        if (dev)
                kfree(to_xenbus_device(dev));
}

static ssize_t nodename_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%s\n", to_xenbus_device(dev)->nodename);
}
static DEVICE_ATTR_RO(nodename);

static ssize_t devtype_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%s\n", to_xenbus_device(dev)->devicetype);
}
static DEVICE_ATTR_RO(devtype);

static ssize_t modalias_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%s:%s\n", dev->bus->name,
                       to_xenbus_device(dev)->devicetype);
}
static DEVICE_ATTR_RO(modalias);

static ssize_t state_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%s\n",
                        xenbus_strstate(to_xenbus_device(dev)->state));
}
static DEVICE_ATTR_RO(state);

static struct attribute *xenbus_dev_attrs[] = {
        &dev_attr_nodename.attr,
        &dev_attr_devtype.attr,
        &dev_attr_modalias.attr,
        &dev_attr_state.attr,
        NULL,
};

static const struct attribute_group xenbus_dev_group = {
        .attrs = xenbus_dev_attrs,
};

const struct attribute_group *xenbus_dev_groups[] = {
        &xenbus_dev_group,
        NULL,
};
EXPORT_SYMBOL_GPL(xenbus_dev_groups);

int xenbus_probe_node(struct xen_bus_type *bus,
                      const char *type,
                      const char *nodename)
{
        char devname[XEN_BUS_ID_SIZE];
        int err;
        struct xenbus_device *xendev;
        size_t stringlen;
        char *tmpstring;

        enum xenbus_state state = xenbus_read_driver_state(NULL, nodename);

        if (state != XenbusStateInitialising) {
                /* Device is not new, so ignore it.  This can happen if a
                   device is going away after switching to Closed.  */
                return 0;
        }

        stringlen = strlen(nodename) + 1 + strlen(type) + 1;
        xendev = kzalloc(sizeof(*xendev) + stringlen, GFP_KERNEL);
        if (!xendev)
                return -ENOMEM;

        xendev->state = XenbusStateInitialising;

        /* Copy the strings into the extra space. */

        tmpstring = (char *)(xendev + 1);
        strcpy(tmpstring, nodename);
        xendev->nodename = tmpstring;

        tmpstring += strlen(tmpstring) + 1;
        strcpy(tmpstring, type);
        xendev->devicetype = tmpstring;
        init_completion(&xendev->down);

        xendev->dev.bus = &bus->bus;
        xendev->dev.release = xenbus_dev_release;

        err = bus->get_bus_id(devname, xendev->nodename);
        if (err)
                goto fail;

        dev_set_name(&xendev->dev, "%s", devname);
        sema_init(&xendev->reclaim_sem, 1);

        /* Register with generic device framework. */
        err = device_register(&xendev->dev);
        if (err) {
                put_device(&xendev->dev);
                xendev = NULL;
                goto fail;
        }

        return 0;
fail:
        kfree(xendev);
        return err;
}
EXPORT_SYMBOL_GPL(xenbus_probe_node);

static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
{
        int err = 0;
        char **dir;
        unsigned int dir_n = 0;
        int i;

        dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
        if (IS_ERR(dir))
                return PTR_ERR(dir);

        for (i = 0; i < dir_n; i++) {
                err = bus->probe(bus, type, dir[i]);
                if (err)
                        break;
        }

        kfree(dir);
        return err;
}

int xenbus_probe_devices(struct xen_bus_type *bus)
{
        int err = 0;
        char **dir;
        unsigned int i, dir_n;

        dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
        if (IS_ERR(dir))
                return PTR_ERR(dir);

        for (i = 0; i < dir_n; i++) {
                err = xenbus_probe_device_type(bus, dir[i]);
                if (err)
                        break;
        }

        kfree(dir);
        return err;
}
EXPORT_SYMBOL_GPL(xenbus_probe_devices);

static unsigned int char_count(const char *str, char c)
{
        unsigned int i, ret = 0;

        for (i = 0; str[i]; i++)
                if (str[i] == c)
                        ret++;
        return ret;
}

static int strsep_len(const char *str, char c, unsigned int len)
{
        unsigned int i;

        for (i = 0; str[i]; i++)
                if (str[i] == c) {
                        if (len == 0)
                                return i;
                        len--;
                }
        return (len == 0) ? i : -ERANGE;
}

void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
{
        int exists, rootlen;
        struct xenbus_device *dev;
        char type[XEN_BUS_ID_SIZE];
        const char *p, *root;

        if (char_count(node, '/') < 2)
                return;

        exists = xenbus_exists(XBT_NIL, node, "");
        if (!exists) {
                xenbus_cleanup_devices(node, &bus->bus);
                return;
        }

        /* backend/<type>/... or device/<type>/... */
        p = strchr(node, '/') + 1;
        snprintf(type, XEN_BUS_ID_SIZE, "%.*s", (int)strcspn(p, "/"), p);
        type[XEN_BUS_ID_SIZE-1] = '\0';

        rootlen = strsep_len(node, '/', bus->levels);
        if (rootlen < 0)
                return;
        root = kasprintf(GFP_KERNEL, "%.*s", rootlen, node);
        if (!root)
                return;

        dev = xenbus_device_find(root, &bus->bus);
        /*
         * Backend domain crash results in not coordinated frontend removal,
         * without going through XenbusStateClosing. If this is a new instance
         * of the same device Xen tools will have reset the state to
         * XenbusStateInitializing.
         * It might be that the backend crashed early during the init phase of
         * device setup, in which case the known state would have been
         * XenbusStateInitializing. So test the backend domid to match the
         * saved one. In case the new backend happens to have the same domid as
         * the old one, we can just carry on, as there is no inconsistency
         * resulting in this case.
         */
        if (dev && !strcmp(bus->root, "device")) {
                enum xenbus_state state = xenbus_read_driver_state(dev, dev->nodename);
                unsigned int backend = xenbus_read_unsigned(root, "backend-id",
                                                            dev->otherend_id);

                if (state == XenbusStateInitialising &&
                    (state != dev->state || backend != dev->otherend_id)) {
                        /*
                         * State has been reset, assume the old one vanished
                         * and new one needs to be probed.
                         */
                        dev_warn(&dev->dev,
                                 "state reset occurred, reconnecting\n");
                        dev->vanished = true;
                }
                if (dev->vanished) {
                        device_unregister(&dev->dev);
                        put_device(&dev->dev);
                        dev = NULL;
                }
        }
        if (!dev)
                xenbus_probe_node(bus, type, root);
        else
                put_device(&dev->dev);

        kfree(root);
}
EXPORT_SYMBOL_GPL(xenbus_dev_changed);

int xenbus_dev_freeze(struct device *dev)
{
        int err = 0;
        struct xenbus_driver *drv;
        struct xenbus_device *xdev
                = container_of(dev, struct xenbus_device, dev);

        DPRINTK("%s", xdev->nodename);

        if (dev->driver == NULL)
                return 0;
        drv = to_xenbus_driver(dev->driver);
        if (drv->suspend)
                err = drv->suspend(xdev);
        if (err)
                dev_warn(dev, "freeze failed: %i\n", err);
        return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_freeze);

int xenbus_dev_restore(struct device *dev)
{
        int err;
        struct xenbus_driver *drv;
        struct xenbus_device *xdev
                = container_of(dev, struct xenbus_device, dev);

        DPRINTK("%s", xdev->nodename);

        if (dev->driver == NULL)
                return 0;
        drv = to_xenbus_driver(dev->driver);
        err = talk_to_otherend(xdev);
        if (err) {
                dev_warn(dev, "restore (talk_to_otherend) failed: %i\n", err);
                return err;
        }

        xdev->state = XenbusStateInitialising;

        if (drv->resume) {
                err = drv->resume(xdev);
                if (err) {
                        dev_warn(dev, "restore failed: %i\n", err);
                        return err;
                }
        }

        err = watch_otherend(xdev);
        if (err) {
                dev_warn(dev, "restore (watch_otherend) failed: %d\n", err);
                return err;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_restore);

int xenbus_dev_thaw(struct device *dev)
{
        /* Do nothing */
        DPRINTK("thaw");
        return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_thaw);

/* A flag to determine if xenstored is 'ready' (i.e. has started) */
int xenstored_ready;


int register_xenstore_notifier(struct notifier_block *nb)
{
        int ret = 0;

        if (xenstored_ready > 0)
                ret = nb->notifier_call(nb, 0, NULL);
        else
                blocking_notifier_chain_register(&xenstore_chain, nb);

        return ret;
}
EXPORT_SYMBOL_GPL(register_xenstore_notifier);

void unregister_xenstore_notifier(struct notifier_block *nb)
{
        blocking_notifier_chain_unregister(&xenstore_chain, nb);
}
EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);

static void xenbus_probe(void)
{
        xenstored_ready = 1;

        if (!xen_store_interface)
                xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
                                               XEN_PAGE_SIZE, MEMREMAP_WB);
        /*
         * Now it is safe to free the IRQ used for xenstore late
         * initialization. No need to unbind: it is about to be
         * bound again from xb_init_comms. Note that calling
         * unbind_from_irqhandler now would result in xen_evtchn_close()
         * being called and the event channel not being enabled again
         * afterwards, resulting in missed event notifications.
         */
        if (xs_init_irq >= 0)
                free_irq(xs_init_irq, &xb_waitq);

        /*
         * In the HVM case, xenbus_init() deferred its call to
         * xs_init() in case callbacks were not operational yet.
         * So do it now.
         */
        if (xen_store_domain_type == XS_HVM)
                xs_init();

        /* Notify others that xenstore is up */
        blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
}

/*
 * Returns true when XenStore init must be deferred in order to
 * allow the PCI platform device to be initialised, before we
 * can actually have event channel interrupts working.
 */
static bool xs_hvm_defer_init_for_callback(void)
{
#ifdef CONFIG_XEN_PVHVM
        return xen_store_domain_type == XS_HVM &&
                !xen_have_vector_callback;
#else
        return false;
#endif
}

static int xenbus_probe_thread(void *unused)
{
        DEFINE_WAIT(w);

        /*
         * We actually just want to wait for *any* trigger of xb_waitq,
         * and run xenbus_probe() the moment it occurs.
         */
        prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE);
        schedule();
        finish_wait(&xb_waitq, &w);

        DPRINTK("probing");
        xenbus_probe();
        return 0;
}

static int __init xenbus_probe_initcall(void)
{
        if (!xen_domain())
                return -ENODEV;

        /*
         * Probe XenBus here in the XS_PV case, and also XS_HVM unless we
         * need to wait for the platform PCI device to come up or
         * xen_store_interface is not ready.
         */
        if (xen_store_domain_type == XS_PV ||
            (xen_store_domain_type == XS_HVM &&
             !xs_hvm_defer_init_for_callback() &&
             XS_INTERFACE_READY))
                xenbus_probe();

        /*
         * For XS_LOCAL or when xen_store_interface is not ready, spawn a
         * thread which will wait for xenstored or a xenstore-stubdom to be
         * started, then probe.  It will be triggered when communication
         * starts happening, by waiting on xb_waitq.
         */
        if (xen_store_domain_type == XS_LOCAL || !XS_INTERFACE_READY) {
                struct task_struct *probe_task;

                probe_task = kthread_run(xenbus_probe_thread, NULL,
                                         "xenbus_probe");
                if (IS_ERR(probe_task))
                        return PTR_ERR(probe_task);
        }
        return 0;
}
device_initcall(xenbus_probe_initcall);

int xen_set_callback_via(uint64_t via)
{
        struct xen_hvm_param a;
        int ret;

        a.domid = DOMID_SELF;
        a.index = HVM_PARAM_CALLBACK_IRQ;
        a.value = via;

        ret = HYPERVISOR_hvm_op(HVMOP_set_param, &a);
        if (ret)
                return ret;

        /*
         * If xenbus_probe_initcall() deferred the xenbus_probe()
         * due to the callback not functioning yet, we can do it now.
         */
        if (!xenstored_ready && xs_hvm_defer_init_for_callback())
                xenbus_probe();

        return ret;
}
EXPORT_SYMBOL_GPL(xen_set_callback_via);

/* Set up event channel for xenstored which is run as a local process
 * (this is normally used only in dom0)
 */
static int __init xenstored_local_init(void)
{
        int err = -ENOMEM;
        unsigned long page = 0;
        struct evtchn_alloc_unbound alloc_unbound;

        /* Allocate Xenstore page */
        page = get_zeroed_page(GFP_KERNEL);
        if (!page)
                goto out_err;

        xen_store_gfn = virt_to_gfn((void *)page);

        /* Next allocate a local port which xenstored can bind to */
        alloc_unbound.dom        = DOMID_SELF;
        alloc_unbound.remote_dom = DOMID_SELF;

        err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
                                          &alloc_unbound);
        if (err == -ENOSYS)
                goto out_err;

        BUG_ON(err);
        xen_store_evtchn = alloc_unbound.port;

        return 0;

 out_err:
        if (page != 0)
                free_page(page);
        return err;
}

static int xenbus_resume_cb(struct notifier_block *nb,
                            unsigned long action, void *data)
{
        int err = 0;

        if (xen_hvm_domain()) {
                uint64_t v = 0;

                err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
                if (!err && v)
                        xen_store_evtchn = v;
                else
                        pr_warn("Cannot update xenstore event channel: %d\n",
                                err);
        } else
                xen_store_evtchn = xen_start_info->store_evtchn;

        return err;
}

static struct notifier_block xenbus_resume_nb = {
        .notifier_call = xenbus_resume_cb,
};

static irqreturn_t xenbus_late_init(int irq, void *unused)
{
        int err;
        uint64_t v = 0;

        err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
        if (err || !v || !~v)
                return IRQ_HANDLED;
        xen_store_gfn = (unsigned long)v;

        wake_up(&xb_waitq);
        return IRQ_HANDLED;
}

static int __init xenbus_init(void)
{
        int err;
        uint64_t v = 0;
        bool wait = false;
        xen_store_domain_type = XS_UNKNOWN;

        if (!xen_domain())
                return -ENODEV;

        xenbus_ring_ops_init();

        if (xen_pv_domain())
                xen_store_domain_type = XS_PV;
        if (xen_hvm_domain())
        {
                xen_store_domain_type = XS_HVM;
                err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
                if (err)
                        goto out_error;
                xen_store_evtchn = (int)v;
                if (!v && xen_initial_domain())
                        xen_store_domain_type = XS_LOCAL;
        }
        if (xen_pv_domain() && !xen_start_info->store_evtchn)
                xen_store_domain_type = XS_LOCAL;
        if (xen_pv_domain() && xen_start_info->store_evtchn)
                xenstored_ready = 1;

        switch (xen_store_domain_type) {
        case XS_LOCAL:
                err = xenstored_local_init();
                if (err)
                        goto out_error;
                xen_store_interface = gfn_to_virt(xen_store_gfn);
                break;
        case XS_PV:
                xen_store_evtchn = xen_start_info->store_evtchn;
                xen_store_gfn = xen_start_info->store_mfn;
                xen_store_interface = gfn_to_virt(xen_store_gfn);
                break;
        case XS_HVM:
                err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
                if (err)
                        goto out_error;
                /*
                 * Uninitialized hvm_params are zero and return no error.
                 * Although it is theoretically possible to have
                 * HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is
                 * not zero when valid. If zero, it means that Xenstore hasn't
                 * been properly initialized. Instead of attempting to map a
                 * wrong guest physical address return error.
                 *
                 * Also recognize all bits set as an invalid/uninitialized value.
                 */
                if (!v) {
                        err = -ENOENT;
                        goto out_error;
                }
                if (v == ~0ULL) {
                        wait = true;
                } else {
                        /* Avoid truncation on 32-bit. */
#if BITS_PER_LONG == 32
                        if (v > ULONG_MAX) {
                                pr_err("%s: cannot handle HVM_PARAM_STORE_PFN=%llx > ULONG_MAX\n",
                                       __func__, v);
                                err = -EINVAL;
                                goto out_error;
                        }
#endif
                        xen_store_gfn = (unsigned long)v;
                        xen_store_interface =
                                memremap(xen_store_gfn << XEN_PAGE_SHIFT,
                                         XEN_PAGE_SIZE, MEMREMAP_WB);
                        if (!xen_store_interface) {
                                pr_err("%s: cannot map HVM_PARAM_STORE_PFN=%llx\n",
                                       __func__, v);
                                err = -EINVAL;
                                goto out_error;
                        }
                        if (xen_store_interface->connection != XENSTORE_CONNECTED)
                                wait = true;
                }
                if (wait) {
                        err = bind_evtchn_to_irqhandler(xen_store_evtchn,
                                                        xenbus_late_init,
                                                        0, "xenstore_late_init",
                                                        &xb_waitq);
                        if (err < 0) {
                                pr_err("xenstore_late_init couldn't bind irq err=%d\n",
                                       err);
                                goto out_error;
                        }

                        xs_init_irq = err;
                }
                break;
        default:
                pr_warn("Xenstore state unknown\n");
                break;
        }

        /*
         * HVM domains may not have a functional callback yet. In that
         * case let xs_init() be called from xenbus_probe(), which will
         * get invoked at an appropriate time.
         */
        if (xen_store_domain_type != XS_HVM) {
                err = xs_init();
                if (err) {
                        pr_warn("Error initializing xenstore comms: %i\n", err);
                        goto out_error;
                }
        }

        if ((xen_store_domain_type != XS_LOCAL) &&
            (xen_store_domain_type != XS_UNKNOWN))
                xen_resume_notifier_register(&xenbus_resume_nb);

#ifdef CONFIG_XEN_COMPAT_XENFS
        /*
         * Create xenfs mountpoint in /proc for compatibility with
         * utilities that expect to find "xenbus" under "/proc/xen".
         */
        proc_create_mount_point("xen");
#endif
        return 0;

out_error:
        xen_store_domain_type = XS_UNKNOWN;
        return err;
}

postcore_initcall(xenbus_init);

MODULE_LICENSE("GPL");