1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Kernel/userspace transport abstraction for Hyper-V util driver. 4 * 5 * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com> 6 */ 7 8 #include <linux/slab.h> 9 #include <linux/fs.h> 10 #include <linux/poll.h> 11 12 #include "hyperv_vmbus.h" 13 #include "hv_utils_transport.h" 14 15 static DEFINE_SPINLOCK(hvt_list_lock); 16 static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list); 17 18 static void hvt_reset(struct hvutil_transport *hvt) 19 { 20 kfree(hvt->outmsg); 21 hvt->outmsg = NULL; 22 hvt->outmsg_len = 0; 23 if (hvt->on_reset) 24 hvt->on_reset(); 25 } 26 27 static ssize_t hvt_op_read(struct file *file, char __user *buf, 28 size_t count, loff_t *ppos) 29 { 30 struct hvutil_transport *hvt; 31 int ret; 32 33 hvt = container_of(file->f_op, struct hvutil_transport, fops); 34 35 if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 || 36 hvt->mode != HVUTIL_TRANSPORT_CHARDEV)) 37 return -EINTR; 38 39 mutex_lock(&hvt->lock); 40 41 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) { 42 ret = -EBADF; 43 goto out_unlock; 44 } 45 46 if (!hvt->outmsg) { 47 ret = -EAGAIN; 48 goto out_unlock; 49 } 50 51 if (count < hvt->outmsg_len) { 52 ret = -EINVAL; 53 goto out_unlock; 54 } 55 56 if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len)) 57 ret = hvt->outmsg_len; 58 else 59 ret = -EFAULT; 60 61 kfree(hvt->outmsg); 62 hvt->outmsg = NULL; 63 hvt->outmsg_len = 0; 64 65 if (hvt->on_read) 66 hvt->on_read(); 67 hvt->on_read = NULL; 68 69 out_unlock: 70 mutex_unlock(&hvt->lock); 71 return ret; 72 } 73 74 static ssize_t hvt_op_write(struct file *file, const char __user *buf, 75 size_t count, loff_t *ppos) 76 { 77 struct hvutil_transport *hvt; 78 u8 *inmsg; 79 int ret; 80 81 hvt = container_of(file->f_op, struct hvutil_transport, fops); 82 83 inmsg = memdup_user(buf, count); 84 if (IS_ERR(inmsg)) 85 return PTR_ERR(inmsg); 86 87 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) 88 ret = -EBADF; 89 else 90 ret = hvt->on_msg(inmsg, count); 91 92 kfree(inmsg); 93 94 return ret ? ret : count; 95 } 96 97 static __poll_t hvt_op_poll(struct file *file, poll_table *wait) 98 { 99 struct hvutil_transport *hvt; 100 101 hvt = container_of(file->f_op, struct hvutil_transport, fops); 102 103 poll_wait(file, &hvt->outmsg_q, wait); 104 105 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) 106 return EPOLLERR | EPOLLHUP; 107 108 if (hvt->outmsg_len > 0) 109 return EPOLLIN | EPOLLRDNORM; 110 111 return 0; 112 } 113 114 static int hvt_op_open(struct inode *inode, struct file *file) 115 { 116 struct hvutil_transport *hvt; 117 int ret = 0; 118 bool issue_reset = false; 119 120 hvt = container_of(file->f_op, struct hvutil_transport, fops); 121 122 mutex_lock(&hvt->lock); 123 124 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) { 125 ret = -EBADF; 126 } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) { 127 /* 128 * Switching to CHARDEV mode. We switch bach to INIT when 129 * device gets released. 130 */ 131 hvt->mode = HVUTIL_TRANSPORT_CHARDEV; 132 } 133 else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) { 134 /* 135 * We're switching from netlink communication to using char 136 * device. Issue the reset first. 137 */ 138 issue_reset = true; 139 hvt->mode = HVUTIL_TRANSPORT_CHARDEV; 140 } else { 141 ret = -EBUSY; 142 } 143 144 if (issue_reset) 145 hvt_reset(hvt); 146 147 mutex_unlock(&hvt->lock); 148 149 return ret; 150 } 151 152 static void hvt_transport_free(struct hvutil_transport *hvt) 153 { 154 misc_deregister(&hvt->mdev); 155 kfree(hvt->outmsg); 156 kfree(hvt); 157 } 158 159 static int hvt_op_release(struct inode *inode, struct file *file) 160 { 161 struct hvutil_transport *hvt; 162 int mode_old; 163 164 hvt = container_of(file->f_op, struct hvutil_transport, fops); 165 166 mutex_lock(&hvt->lock); 167 mode_old = hvt->mode; 168 if (hvt->mode != HVUTIL_TRANSPORT_DESTROY) 169 hvt->mode = HVUTIL_TRANSPORT_INIT; 170 /* 171 * Cleanup message buffers to avoid spurious messages when the daemon 172 * connects back. 173 */ 174 hvt_reset(hvt); 175 176 if (mode_old == HVUTIL_TRANSPORT_DESTROY) 177 complete(&hvt->release); 178 179 mutex_unlock(&hvt->lock); 180 181 return 0; 182 } 183 184 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp) 185 { 186 struct hvutil_transport *hvt, *hvt_found = NULL; 187 188 spin_lock(&hvt_list_lock); 189 list_for_each_entry(hvt, &hvt_list, list) { 190 if (hvt->cn_id.idx == msg->id.idx && 191 hvt->cn_id.val == msg->id.val) { 192 hvt_found = hvt; 193 break; 194 } 195 } 196 spin_unlock(&hvt_list_lock); 197 if (!hvt_found) { 198 pr_warn("hvt_cn_callback: spurious message received!\n"); 199 return; 200 } 201 202 /* 203 * Switching to NETLINK mode. Switching to CHARDEV happens when someone 204 * opens the device. 205 */ 206 mutex_lock(&hvt->lock); 207 if (hvt->mode == HVUTIL_TRANSPORT_INIT) 208 hvt->mode = HVUTIL_TRANSPORT_NETLINK; 209 210 if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) 211 hvt_found->on_msg(msg->data, msg->len); 212 else 213 pr_warn("hvt_cn_callback: unexpected netlink message!\n"); 214 mutex_unlock(&hvt->lock); 215 } 216 217 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len, 218 void (*on_read_cb)(void)) 219 { 220 struct cn_msg *cn_msg; 221 int ret = 0; 222 223 if (hvt->mode == HVUTIL_TRANSPORT_INIT || 224 hvt->mode == HVUTIL_TRANSPORT_DESTROY) { 225 return -EINVAL; 226 } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) { 227 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC); 228 if (!cn_msg) 229 return -ENOMEM; 230 cn_msg->id.idx = hvt->cn_id.idx; 231 cn_msg->id.val = hvt->cn_id.val; 232 cn_msg->len = len; 233 memcpy(cn_msg->data, msg, len); 234 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC); 235 kfree(cn_msg); 236 /* 237 * We don't know when netlink messages are delivered but unlike 238 * in CHARDEV mode we're not blocked and we can send next 239 * messages right away. 240 */ 241 if (on_read_cb) 242 on_read_cb(); 243 return ret; 244 } 245 /* HVUTIL_TRANSPORT_CHARDEV */ 246 mutex_lock(&hvt->lock); 247 if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) { 248 ret = -EINVAL; 249 goto out_unlock; 250 } 251 252 if (hvt->outmsg) { 253 /* Previous message wasn't received */ 254 ret = -EFAULT; 255 goto out_unlock; 256 } 257 hvt->outmsg = kzalloc(len, GFP_KERNEL); 258 if (hvt->outmsg) { 259 memcpy(hvt->outmsg, msg, len); 260 hvt->outmsg_len = len; 261 hvt->on_read = on_read_cb; 262 wake_up_interruptible(&hvt->outmsg_q); 263 } else 264 ret = -ENOMEM; 265 out_unlock: 266 mutex_unlock(&hvt->lock); 267 return ret; 268 } 269 270 struct hvutil_transport *hvutil_transport_init(const char *name, 271 u32 cn_idx, u32 cn_val, 272 int (*on_msg)(void *, int), 273 void (*on_reset)(void)) 274 { 275 struct hvutil_transport *hvt; 276 277 hvt = kzalloc(sizeof(*hvt), GFP_KERNEL); 278 if (!hvt) 279 return NULL; 280 281 hvt->cn_id.idx = cn_idx; 282 hvt->cn_id.val = cn_val; 283 284 hvt->mdev.minor = MISC_DYNAMIC_MINOR; 285 hvt->mdev.name = name; 286 287 hvt->fops.owner = THIS_MODULE; 288 hvt->fops.read = hvt_op_read; 289 hvt->fops.write = hvt_op_write; 290 hvt->fops.poll = hvt_op_poll; 291 hvt->fops.open = hvt_op_open; 292 hvt->fops.release = hvt_op_release; 293 294 hvt->mdev.fops = &hvt->fops; 295 296 init_waitqueue_head(&hvt->outmsg_q); 297 mutex_init(&hvt->lock); 298 init_completion(&hvt->release); 299 300 spin_lock(&hvt_list_lock); 301 list_add(&hvt->list, &hvt_list); 302 spin_unlock(&hvt_list_lock); 303 304 hvt->on_msg = on_msg; 305 hvt->on_reset = on_reset; 306 307 if (misc_register(&hvt->mdev)) 308 goto err_free_hvt; 309 310 /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */ 311 if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 && 312 cn_add_callback(&hvt->cn_id, name, hvt_cn_callback)) 313 goto err_free_hvt; 314 315 return hvt; 316 317 err_free_hvt: 318 spin_lock(&hvt_list_lock); 319 list_del(&hvt->list); 320 spin_unlock(&hvt_list_lock); 321 kfree(hvt); 322 return NULL; 323 } 324 325 void hvutil_transport_destroy(struct hvutil_transport *hvt) 326 { 327 int mode_old; 328 329 mutex_lock(&hvt->lock); 330 mode_old = hvt->mode; 331 hvt->mode = HVUTIL_TRANSPORT_DESTROY; 332 wake_up_interruptible(&hvt->outmsg_q); 333 mutex_unlock(&hvt->lock); 334 335 /* 336 * In case we were in 'chardev' mode we still have an open fd so we 337 * have to defer freeing the device. Netlink interface can be freed 338 * now. 339 */ 340 spin_lock(&hvt_list_lock); 341 list_del(&hvt->list); 342 spin_unlock(&hvt_list_lock); 343 if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0) 344 cn_del_callback(&hvt->cn_id); 345 346 if (mode_old == HVUTIL_TRANSPORT_CHARDEV) 347 wait_for_completion(&hvt->release); 348 349 hvt_transport_free(hvt); 350 } 351