1 /****************************************************************************** 2 * Talks to Xen Store to figure out what devices we have (backend half). 3 * 4 * Copyright (C) 2005 Rusty Russell, IBM Corporation 5 * Copyright (C) 2005 Mike Wray, Hewlett-Packard 6 * Copyright (C) 2005, 2006 XenSource Ltd 7 * Copyright (C) 2007 Solarflare Communications, Inc. 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License version 2 11 * as published by the Free Software Foundation; or, when distributed 12 * separately from the Linux kernel or incorporated into other 13 * software packages, subject to the following license: 14 * 15 * Permission is hereby granted, free of charge, to any person obtaining a copy 16 * of this source file (the "Software"), to deal in the Software without 17 * restriction, including without limitation the rights to use, copy, modify, 18 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 19 * and to permit persons to whom the Software is furnished to do so, subject to 20 * the following conditions: 21 * 22 * The above copyright notice and this permission notice shall be included in 23 * all copies or substantial portions of the Software. 24 * 25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 31 * IN THE SOFTWARE. 32 */ 33 34 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 35 36 #define DPRINTK(fmt, ...) \ 37 pr_debug("(%s:%d) " fmt "\n", \ 38 __func__, __LINE__, ##__VA_ARGS__) 39 40 #include <linux/kernel.h> 41 #include <linux/err.h> 42 #include <linux/string.h> 43 #include <linux/ctype.h> 44 #include <linux/fcntl.h> 45 #include <linux/mm.h> 46 #include <linux/notifier.h> 47 #include <linux/export.h> 48 #include <linux/semaphore.h> 49 50 #include <asm/page.h> 51 #include <asm/xen/hypervisor.h> 52 #include <asm/hypervisor.h> 53 #include <xen/xenbus.h> 54 #include <xen/features.h> 55 56 #include "xenbus.h" 57 58 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */ 59 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename) 60 { 61 int domid, err; 62 const char *devid, *type, *frontend; 63 unsigned int typelen; 64 65 type = strchr(nodename, '/'); 66 if (!type) 67 return -EINVAL; 68 type++; 69 typelen = strcspn(type, "/"); 70 if (!typelen || type[typelen] != '/') 71 return -EINVAL; 72 73 devid = strrchr(nodename, '/') + 1; 74 75 err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid, 76 "frontend", NULL, &frontend, 77 NULL); 78 if (err) 79 return err; 80 if (strlen(frontend) == 0) 81 err = -ERANGE; 82 if (!err && !xenbus_exists(XBT_NIL, frontend, "")) 83 err = -ENOENT; 84 kfree(frontend); 85 86 if (err) 87 return err; 88 89 if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s", 90 typelen, type, domid, devid) >= XEN_BUS_ID_SIZE) 91 return -ENOSPC; 92 return 0; 93 } 94 95 static int xenbus_uevent_backend(const struct device *dev, 96 struct kobj_uevent_env *env) 97 { 98 const struct xenbus_device *xdev; 99 const struct xenbus_driver *drv; 100 const struct xen_bus_type *bus; 101 102 DPRINTK(""); 103 104 if (dev == NULL) 105 return -ENODEV; 106 107 xdev = to_xenbus_device(dev); 108 bus = container_of(xdev->dev.bus, struct xen_bus_type, bus); 109 110 if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype)) 111 return -ENOMEM; 112 113 /* stuff we want to pass to /sbin/hotplug */ 114 if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype)) 115 return -ENOMEM; 116 117 if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename)) 118 return -ENOMEM; 119 120 if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root)) 121 return -ENOMEM; 122 123 if (dev->driver) { 124 drv = to_xenbus_driver(dev->driver); 125 if (drv && drv->uevent) 126 return drv->uevent(xdev, env); 127 } 128 129 return 0; 130 } 131 132 /* backend/<typename>/<frontend-uuid>/<name> */ 133 static int xenbus_probe_backend_unit(struct xen_bus_type *bus, 134 const char *dir, 135 const char *type, 136 const char *name) 137 { 138 char *nodename; 139 int err; 140 141 nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name); 142 if (!nodename) 143 return -ENOMEM; 144 145 DPRINTK("%s\n", nodename); 146 147 err = xenbus_probe_node(bus, type, nodename); 148 kfree(nodename); 149 return err; 150 } 151 152 /* backend/<typename>/<frontend-domid> */ 153 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type, 154 const char *domid) 155 { 156 char *nodename; 157 int err = 0; 158 char **dir; 159 unsigned int i, dir_n = 0; 160 161 DPRINTK(""); 162 163 nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid); 164 if (!nodename) 165 return -ENOMEM; 166 167 dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n); 168 if (IS_ERR(dir)) { 169 kfree(nodename); 170 return PTR_ERR(dir); 171 } 172 173 for (i = 0; i < dir_n; i++) { 174 err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]); 175 if (err) 176 break; 177 } 178 kfree(dir); 179 kfree(nodename); 180 return err; 181 } 182 183 static bool frontend_will_handle(struct xenbus_watch *watch, 184 const char *path, const char *token) 185 { 186 return watch->nr_pending == 0; 187 } 188 189 static void frontend_changed(struct xenbus_watch *watch, 190 const char *path, const char *token) 191 { 192 xenbus_otherend_changed(watch, path, token, 0); 193 } 194 195 static struct xen_bus_type xenbus_backend = { 196 .root = "backend", 197 .levels = 3, /* backend/type/<frontend>/<id> */ 198 .get_bus_id = backend_bus_id, 199 .probe = xenbus_probe_backend, 200 .otherend_will_handle = frontend_will_handle, 201 .otherend_changed = frontend_changed, 202 .bus = { 203 .name = "xen-backend", 204 .match = xenbus_match, 205 .uevent = xenbus_uevent_backend, 206 .probe = xenbus_dev_probe, 207 .remove = xenbus_dev_remove, 208 .dev_groups = xenbus_dev_groups, 209 }, 210 }; 211 212 static void backend_changed(struct xenbus_watch *watch, 213 const char *path, const char *token) 214 { 215 DPRINTK(""); 216 217 xenbus_dev_changed(path, &xenbus_backend); 218 } 219 220 static struct xenbus_watch be_watch = { 221 .node = "backend", 222 .callback = backend_changed, 223 }; 224 225 static int read_frontend_details(struct xenbus_device *xendev) 226 { 227 return xenbus_read_otherend_details(xendev, "frontend-id", "frontend"); 228 } 229 230 int xenbus_dev_is_online(struct xenbus_device *dev) 231 { 232 return !!xenbus_read_unsigned(dev->nodename, "online", 0); 233 } 234 EXPORT_SYMBOL_GPL(xenbus_dev_is_online); 235 236 int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner, 237 const char *mod_name) 238 { 239 drv->read_otherend_details = read_frontend_details; 240 241 return xenbus_register_driver_common(drv, &xenbus_backend, 242 owner, mod_name); 243 } 244 EXPORT_SYMBOL_GPL(__xenbus_register_backend); 245 246 static int backend_probe_and_watch(struct notifier_block *notifier, 247 unsigned long event, 248 void *data) 249 { 250 /* Enumerate devices in xenstore and watch for changes. */ 251 xenbus_probe_devices(&xenbus_backend); 252 register_xenbus_watch(&be_watch); 253 254 return NOTIFY_DONE; 255 } 256 257 static int backend_reclaim_memory(struct device *dev, void *data) 258 { 259 const struct xenbus_driver *drv; 260 struct xenbus_device *xdev; 261 262 if (!dev->driver) 263 return 0; 264 drv = to_xenbus_driver(dev->driver); 265 if (drv && drv->reclaim_memory) { 266 xdev = to_xenbus_device(dev); 267 if (down_trylock(&xdev->reclaim_sem)) 268 return 0; 269 drv->reclaim_memory(xdev); 270 up(&xdev->reclaim_sem); 271 } 272 return 0; 273 } 274 275 /* 276 * Returns 0 always because we are using shrinker to only detect memory 277 * pressure. 278 */ 279 static unsigned long backend_shrink_memory_count(struct shrinker *shrinker, 280 struct shrink_control *sc) 281 { 282 bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, 283 backend_reclaim_memory); 284 return 0; 285 } 286 287 static int __init xenbus_probe_backend_init(void) 288 { 289 struct shrinker *backend_memory_shrinker; 290 static struct notifier_block xenstore_notifier = { 291 .notifier_call = backend_probe_and_watch 292 }; 293 int err; 294 295 DPRINTK(""); 296 297 /* Register ourselves with the kernel bus subsystem */ 298 err = bus_register(&xenbus_backend.bus); 299 if (err) 300 return err; 301 302 register_xenstore_notifier(&xenstore_notifier); 303 304 backend_memory_shrinker = shrinker_alloc(0, "xen-backend"); 305 if (!backend_memory_shrinker) { 306 pr_warn("shrinker allocation failed\n"); 307 return 0; 308 } 309 310 backend_memory_shrinker->count_objects = backend_shrink_memory_count; 311 312 shrinker_register(backend_memory_shrinker); 313 314 return 0; 315 } 316 subsys_initcall(xenbus_probe_backend_init); 317