/******************************************************************************
* xenbus_xs.c
*
* This is the kernel equivalent of the "xs" library. We don't need everything
* and we use xenbus_comms for communication.
*
* Copyright (C) 2005 Rusty Russell, IBM Corporation
*
* 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.
*/
#include <linux/unistd.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/uio.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/kthread.h>
#include <linux/rwsem.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <xen/xenbus.h>
#include "xenbus_comms.h"
struct xs_stored_msg {
struct list_head list;
struct xsd_sockmsg hdr;
union {
/* Queued replies. */
struct {
char *body;
} reply;
/* Queued watch events. */
struct {
struct xenbus_watch *handle;
char **vec;
unsigned int vec_size;
} watch;
} u;
};
struct xs_handle {
/* A list of replies. Currently only one will ever be outstanding. */
struct list_head reply_list;
spinlock_t reply_lock;
wait_queue_head_t reply_waitq;
/*
* Mutex ordering: transaction_mutex -> watch_mutex -> request_mutex.
* response_mutex is never taken simultaneously with the other three.
*/
/* One request at a time. */
struct mutex request_mutex;
/* Protect xenbus reader thread against save/restore. */
struct mutex response_mutex;
/* Protect transactions against save/restore. */
struct rw_semaphore transaction_mutex;
/* Protect watch (de)register against save/restore. */
struct rw_semaphore watch_mutex;
};
static struct xs_handle xs_state;
/* List of registered watches, and a lock to protect it. */
static LIST_HEAD(watches);
static DEFINE_SPINLOCK(watches_lock);
/* List of pending watch callback events, and a lock to protect it. */
static LIST_HEAD(watch_events);
static DEFINE_SPINLOCK(watch_events_lock);
/*
* Details of the xenwatch callback kernel thread. The thread waits on the
* watch_events_waitq for work to do (queued on watch_events list). When it
* wakes up it acquires the xenwatch_mutex before reading the list and
* carrying out work.
*/
static pid_t xenwatch_pid;
static DEFINE_MUTEX(xenwatch_mutex);
static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq);
static int get_error(const char *errorstring)
{
unsigned int i;
for (i = 0; strcmp(errorstring, xsd_errors[i].errstring) != 0; i++) {
if (i == ARRAY_SIZE(xsd_errors) - 1) {
printk(KERN_WARNING
"XENBUS xen store gave: unknown error %s",
errorstring);
return EINVAL;
}
}
return xsd_errors[i].errnum;
}
static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len)
{
struct xs_stored_msg *msg;
char *body;
spin_lock(&xs_state.reply_lock);
while (list_empty(&xs_state.reply_list)) {
spin_unlock(&xs_state.reply_lock);
/* XXX FIXME: Avoid synchronous wait for response here. */
wait_event(xs_state.reply_waitq,
!list_empty(&xs_state.reply_list));
spin_lock(&xs_state.reply_lock);
}
msg = list_entry(xs_state.reply_list.next,
struct xs_stored_msg, list);
list_del(&msg->list);
spin_unlock(&xs_state.reply_lock);
*type = msg->hdr.type;
if (len)
*len = msg->hdr.len;
body = msg->u.reply.body;
kfree(msg);
return body;
}
void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
{
void *ret;
struct xsd_sockmsg req_msg = *msg;
int err;
if (req_msg.type == XS_TRANSACTION_START)
down_read(&xs_state.transaction_mutex);
mutex_lock(&xs_state.request_mutex);
err = xb_write(msg, sizeof(*msg) + msg->len);
if (err) {
msg->type = XS_ERROR;
ret = ERR_PTR(err);
} else
ret = read_reply(&msg->type, &msg->len);
mutex_unlock(&xs_state.request_mutex);
if ((msg->type == XS_TRANSACTION_END) ||
((req_msg.type == XS_TRANSACTION_START) &&
(msg->type == XS_ERROR)))
up_read(&xs_state.transaction_mutex);
return ret;
}
EXPORT_SYMBOL(xenbus_dev_request_and_reply);
/* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */
static void *xs_talkv(struct xenbus_transaction t,
enum xsd_sockmsg_type type,
const struct kvec *iovec,
unsigned int num_vecs,
unsigned int *len)
{
struct xsd_sockmsg msg;
void *ret = NULL;
unsigned int i;
int err;
msg.tx_id = t.id;
msg.req_id = 0;
msg.type = type;
msg.len = 0;
for (i = 0; i < num_vecs; i++)
msg.len += iovec[i].iov_len;
mutex_lock(&xs_state.request_mutex);
err = xb_write(&msg, sizeof(msg));
if (err) {
mutex_unlock(&xs_state.request_mutex);
return ERR_PTR(err);
}
for (i = 0; i < num_vecs; i++) {
err = xb_write(iovec[i].iov_base, iovec[i].iov_len);
if (err) {
mutex_unlock(&xs_state.request_mutex);
return ERR_PTR(err);
}
}
ret = read_reply(&msg.type, len);
mutex_unlock(&xs_state.request_mutex);
if (IS_ERR(ret))
return ret;
if (msg.type == XS_ERROR) {
err = get_error(ret);
kfree(ret);
return ERR_PTR(-err);
}
if (msg.type != type) {
if (printk_ratelimit())
printk(KERN_WARNING
"XENBUS unexpected type [%d], expected [%d]\n",
msg.type, type);
kfree(ret);
return ERR_PTR(-EINVAL);
}
return ret;
}
/* Simplified version of xs_talkv: single message. */
static void *xs_single(struct xenbus_transaction t,
enum xsd_sockmsg_type type,
const char *string,
unsigned int *len)
{
struct kvec iovec;
iovec.iov_base = (void *)string;
iovec.iov_len = strlen(string) + 1;
return xs_talkv(t, type, &iovec, 1, len);
}
/* Many commands only need an ack, don't care what it says. */
static int xs_error(char *reply)
{
if (IS_ERR(reply))
return PTR_ERR(reply);
kfree(reply);
return 0;
}
static unsigned int count_strings(const char *strings, unsigned int len)
{
unsigned int num;
const char *p;
for (p = strings, num = 0; p < strings + len; p += strlen(p) + 1)
num++;
return num;
}
/* Return the path to dir with /name appended. Buffer must be kfree()'ed. */
static char *join(const char *dir, const char *name)
{
char *buffer;
if (strlen(name) == 0)
buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s", dir);
else
buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/%s", dir, name);
return (!buffer) ? ERR_PTR(-ENOMEM) : buffer;
}
static char **split(char *strings, unsigned int len, unsigned int *num)
{
char *p, **ret;
/* Count the strings. */
*num = count_strings(strings, len);
/* Transfer to one big alloc for easy freeing. */
ret = kmalloc(*num * sizeof(char *) + len, GFP_NOIO | __GFP_HIGH);
if (!ret) {
kfree(strings);
return ERR_PTR(-ENOMEM);
}
memcpy(&ret[*num], strings, len);
kfree(strings);
strings = (char *)&ret[*num];
for (p = strings, *num = 0; p < strings + len; p += strlen(p) + 1)
ret[(*num)++] = p;
return ret;
}
char **xenbus_directory(struct xenbus_transaction t,
const char *dir, const char *node, unsigned int *num)
{
char *strings, *path;
unsigned int len;
path = join(dir, node);
if (IS_ERR(path))
return (char **)path;
strings = xs_single(t, XS_DIRECTORY, path, &len);
kfree(path);
if (IS_ERR(strings))
return (char **)strings;
return split(strings, len, num);
}
EXPORT_SYMBOL_GPL(xenbus_directory);
/* Check if a path exists. Return 1 if it does. */
int xenbus_exists(struct xenbus_transaction t,
const char *dir, const char *node)
{
char **d;
int dir_n;
d = xenbus_directory(t, dir, node, &dir_n);
if (IS_ERR(d))
return 0;
kfree(d);
return 1;
}
EXPORT_SYMBOL_GPL(xenbus_exists);
/* Get the value of a single file.
* Returns a kmalloced value: call free() on it after use.
* len indicates length in bytes.
*/
void *xenbus_read(struct xenbus_transaction t,
const char *dir, const char *node, unsigned int *len)
{
char *path;
void *ret;
path = join(dir, node);
if (IS_ERR(path))
return (void *)path;
ret = xs_single(t, XS_READ, path, len);
kfree(path);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_read);
/* Write the value of a single file.
* Returns -err on failure.
*/
int xenbus_write(struct xenbus_transaction t,
const char *dir, const char *node, const char *string)
{
const char *path;
struct kvec iovec[2];
int ret;
path = join(dir, node);
if (IS_ERR(path))
return PTR_ERR(path);
iovec[0].iov_base = (void *)path;
iovec[0].iov_len = strlen(path) + 1;
iovec[1].iov_base = (void *)string;
iovec[1].iov_len = strlen(string);
ret = xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL));
kfree(path);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_write);
/* Create a new directory. */
int xenbus_mkdir(struct xenbus_transaction t,
const char *dir, const char *node)
{
char *path;
int ret;
path = join(dir, node);
if (IS_ERR(path))
return PTR_ERR(path);
ret = xs_error(xs_single(t, XS_MKDIR, path, NULL));
kfree(path);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_mkdir);
/* Destroy a file or directory (directories must be empty). */
int xenbus_rm(struct xenbus_transaction t, const char *dir, const char *node)
{
char *path;
int ret;
path = join(dir, node);
if (IS_ERR(path))
return PTR_ERR(path);
ret = xs_error(xs_single(t, XS_RM, path, NULL));
kfree(path);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_rm);
/* Start a transaction: changes by others will not be seen during this
* transaction, and changes will not be visible to others until end.
*/
int xenbus_transaction_start(struct xenbus_transaction *t)
{
char *id_str;
down_read(&xs_state.transaction_mutex);
id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL);
if (IS_ERR(id_str)) {
up_read(&xs_state.transaction_mutex);
return PTR_ERR(id_str);
}
t->id = simple_strtoul(id_str, NULL, 0);
kfree(id_str);
return 0;
}
EXPORT_SYMBOL_GPL(xenbus_transaction_start);
/* End a transaction.
* If abandon is true, transaction is discarded instead of committed.
*/
int xenbus_transaction_end(struct xenbus_transaction t, int abort)
{
char abortstr[2];
int err;
if (abort)
strcpy(abortstr, "F");
else
strcpy(abortstr, "T");
err = xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL));
up_read(&xs_state.transaction_mutex);
return err;
}
EXPORT_SYMBOL_GPL(xenbus_transaction_end);
/* Single read and scanf: returns -errno or num scanned. */
int xenbus_scanf(struct xenbus_transaction t,
const char *dir, const char *node, const char *fmt, ...)
{
va_list ap;
int ret;
char *val;
val = xenbus_read(t, dir, node, NULL);
if (IS_ERR(val))
return PTR_ERR(val);
va_start(ap, fmt);
ret = vsscanf(val, fmt, ap);
va_end(ap);
kfree(val);
/* Distinctive errno. */
if (ret == 0)
return -ERANGE;
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_scanf);
/* Single printf and write: returns -errno or 0. */
int xenbus_printf(struct xenbus_transaction t,
const char *dir, const char *node, const char *fmt, ...)
{
va_list ap;
int ret;
#define PRINTF_BUFFER_SIZE 4096
char *printf_buffer;
printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
if (printf_buffer == NULL)
return -ENOMEM;
va_start(ap, fmt);
ret = vsnprintf(printf_buffer, PRINTF_BUFFER_SIZE, fmt, ap);
va_end(ap);
BUG_ON(ret > PRINTF_BUFFER_SIZE-1);
ret = xenbus_write(t, dir, node, printf_buffer);
kfree(printf_buffer);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_printf);
/* Takes tuples of names, scanf-style args, and void **, NULL terminated. */
int xenbus_gather(struct xenbus_transaction t, const char *dir, ...)
{
va_list ap;
const char *name;
int ret = 0;
va_start(ap, dir);
while (ret == 0 && (name = va_arg(ap, char *)) != NULL) {
const char *fmt = va_arg(ap, char *);
void *result = va_arg(ap, void *);
char *p;
p = xenbus_read(t, dir, name, NULL);
if (IS_ERR(p)) {
ret = PTR_ERR(p);
break;
}
if (fmt) {
if (sscanf(p, fmt, result) == 0)
ret = -EINVAL;
kfree(p);
} else
*(char **)result = p;
}
va_end(ap);
return ret;
}
EXPORT_SYMBOL_GPL(xenbus_gather);
static int xs_watch(const char *path, const char *token)
{
struct kvec iov[2];
iov[0].iov_base = (void *)path;
iov[0].iov_len = strlen(path) + 1;
iov[1].iov_base = (void *)token;
iov[1].iov_len = strlen(token) + 1;
return xs_error(xs_talkv(XBT_NIL, XS_WATCH, iov,
ARRAY_SIZE(iov), NULL));
}
static int xs_unwatch(const char *path, const char *token)
{
struct kvec iov[2];
iov[0].iov_base = (char *)path;
iov[0].iov_len = strlen(path) + 1;
iov[1].iov_base = (char *)token;
iov[1].iov_len = strlen(token) + 1;
return xs_error(xs_talkv(XBT_NIL, XS_UNWATCH, iov,
ARRAY_SIZE(iov), NULL));
}
static struct xenbus_watch *find_watch(const char *token)
{
struct xenbus_watch *i, *cmp;
cmp = (void *)simple_strtoul(token, NULL, 16);
list_for_each_entry(i, &watches, list)
if (i == cmp)
return i;
return NULL;
}
/* Register callback to watch this node. */
int register_xenbus_watch(struct xenbus_watch *watch)
{
/* Pointer in ascii is the token. */
char token[sizeof(watch) * 2 + 1];
int err;
sprintf(token, "%lX", (long)watch);
down_read(&xs_state.watch_mutex);
spin_lock(&watches_lock);
BUG_ON(find_watch(token));
list_add(&watch->list, &watches);
spin_unlock(&watches_lock);
err = xs_watch(watch->node, token);
/* Ignore errors due to multiple registration. */
if ((err != 0) && (err != -EEXIST)) {
spin_lock(&watches_lock);
list_del(&watch->list);
spin_unlock(&watches_lock);
}
up_read(&xs_state.watch_mutex);
return err;
}
EXPORT_SYMBOL_GPL(register_xenbus_watch);
void unregister_xenbus_watch(struct xenbus_watch *watch)
{
struct xs_stored_msg *msg, *tmp;
char token[sizeof(watch) * 2 + 1];
int err;
sprintf(token, "%lX", (long)watch);
down_read(&xs_state.watch_mutex);
spin_lock(&watches_lock);
BUG_ON(!find_watch(token));
list_del(&watch->list);
spin_unlock(&watches_lock);
err = xs_unwatch(watch->node, token);
if (err)
printk(KERN_WARNING
"XENBUS Failed to release watch %s: %i\n",
watch->node, err);
up_read(&xs_state.watch_mutex);
/* Make sure there are no callbacks running currently (unless
its us) */
if (current->pid != xenwatch_pid)
mutex_lock(&xenwatch_mutex);
/* Cancel pending watch events. */
spin_lock(&watch_events_lock);
list_for_each_entry_safe(msg, tmp, &watch_events, list) {
if (msg->u.watch.handle != watch)
continue;
list_del(&msg->list);
kfree(msg->u.watch.vec);
kfree(msg);
}
spin_unlock(&watch_events_lock);
if (current->pid != xenwatch_pid)
mutex_unlock(&xenwatch_mutex);
}
EXPORT_SYMBOL_GPL(unregister_xenbus_watch);
void xs_suspend(void)
{
down_write(&xs_state.transaction_mutex);
down_write(&xs_state.watch_mutex);
mutex_lock(&xs_state.request_mutex);
mutex_lock(&xs_state.response_mutex);
}
void xs_resume(void)
{
struct xenbus_watch *watch;
char token[sizeof(watch) * 2 + 1];
xb_init_comms();
mutex_unlock(&xs_state.response_mutex);
mutex_unlock(&xs_state.request_mutex);
up_write(&xs_state.transaction_mutex);
/* No need for watches_lock: the watch_mutex is sufficient. */
list_for_each_entry(watch, &watches, list) {
sprintf(token, "%lX", (long)watch);
xs_watch(watch->node, token);
}
up_write(&xs_state.watch_mutex);
}
void xs_suspend_cancel(void)
{
mutex_unlock(&xs_state.response_mutex);
mutex_unlock(&xs_state.request_mutex);
up_write(&xs_state.watch_mutex);
up_write(&xs_state.transaction_mutex);
}
static int xenwatch_thread(void *unused)
{
struct list_head *ent;
struct xs_stored_msg *msg;
for (;;) {
wait_event_interruptible(watch_events_waitq,
!list_empty(&watch_events));
if (kthread_should_stop())
break;
mutex_lock(&xenwatch_mutex);
spin_lock(&watch_events_lock);
ent = watch_events.next;
if (ent != &watch_events)
list_del(ent);
spin_unlock(&watch_events_lock);
if (ent != &watch_events) {
msg = list_entry(ent, struct xs_stored_msg, list);
msg->u.watch.handle->callback(
msg->u.watch.handle,
(const char **)msg->u.watch.vec,
msg->u.watch.vec_size);
kfree(msg->u.watch.vec);
kfree(msg);
}
mutex_unlock(&xenwatch_mutex);
}
return 0;
}
static int process_msg(void)
{
struct xs_stored_msg *msg;
char *body;
int err;
/*
* We must disallow save/restore while reading a xenstore message.
* A partial read across s/r leaves us out of sync with xenstored.
*/
for (;;) {
err = xb_wait_for_data_to_read();
if (err)
return err;
mutex_lock(&xs_state.response_mutex);
if (xb_data_to_read())
break;
/* We raced with save/restore: pending data 'disappeared'. */
mutex_unlock(&xs_state.response_mutex);
}
msg = kmalloc(sizeof(*msg), GFP_NOIO | __GFP_HIGH);
if (msg == NULL) {
err = -ENOMEM;
goto out;
}
err = xb_read(&msg->hdr, sizeof(msg->hdr));
if (err) {
kfree(msg);
goto out;
}
body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);
if (body == NULL) {
kfree(msg);
err = -ENOMEM;
goto out;
}
err = xb_read(body, msg->hdr.len);
if (err) {
kfree(body);
kfree(msg);
goto out;
}
body[msg->hdr.len] = '\0';
if (msg->hdr.type == XS_WATCH_EVENT) {
msg->u.watch.vec = split(body, msg->hdr.len,
&msg->u.watch.vec_size);
if (IS_ERR(msg->u.watch.vec)) {
err = PTR_ERR(msg->u.watch.vec);
kfree(msg);
goto out;
}
spin_lock(&watches_lock);
msg->u.watch.handle = find_watch(
msg->u.watch.vec[XS_WATCH_TOKEN]);
if (msg->u.watch.handle != NULL) {
spin_lock(&watch_events_lock);
list_add_tail(&msg->list, &watch_events);
wake_up(&watch_events_waitq);
spin_unlock(&watch_events_lock);
} else {
kfree(msg->u.watch.vec);
kfree(msg);
}
spin_unlock(&watches_lock);
} else {
msg->u.reply.body = body;
spin_lock(&xs_state.reply_lock);
list_add_tail(&msg->list, &xs_state.reply_list);
spin_unlock(&xs_state.reply_lock);
wake_up(&xs_state.reply_waitq);
}
out:
mutex_unlock(&xs_state.response_mutex);
return err;
}
static int xenbus_thread(void *unused)
{
int err;
for (;;) {
err = process_msg();
if (err)
printk(KERN_WARNING "XENBUS error %d while reading "
"message\n", err);
if (kthread_should_stop())
break;
}
return 0;
}
int xs_init(void)
{
int err;
struct task_struct *task;
INIT_LIST_HEAD(&xs_state.reply_list);
spin_lock_init(&xs_state.reply_lock);
init_waitqueue_head(&xs_state.reply_waitq);
mutex_init(&xs_state.request_mutex);
mutex_init(&xs_state.response_mutex);
init_rwsem(&xs_state.transaction_mutex);
init_rwsem(&xs_state.watch_mutex);
/* Initialize the shared memory rings to talk to xenstored */
err = xb_init_comms();
if (err)
return err;
task = kthread_run(xenwatch_thread, NULL, "xenwatch");
if (IS_ERR(task))
return PTR_ERR(task);
xenwatch_pid = task->pid;
task = kthread_run(xenbus_thread, NULL, "xenbus");
if (IS_ERR(task))
return PTR_ERR(task);
return 0;
}
