/****************************************************************************** * 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; } /* 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_KERNEL, "%s", dir); else buffer = kasprintf(GFP_KERNEL, "%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_KERNEL); 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]; 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_KERNEL); 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_KERNEL); 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; }