hw/virtio-9p.c

   1 /*
   2  * Virtio 9p backend
   3  *
   4  * Copyright IBM, Corp. 2010
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "virtio.h"
  15 #include "pc.h"
  16 #include "qemu_socket.h"
  17 #include "virtio-9p.h"
  18 #include "fsdev/qemu-fsdev.h"
  19 #include "virtio-9p-debug.h"
  20
  21 int dotu = 1;
  22 int debug_9p_pdu;
  23
  24 static int v9fs_do_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
  25 {
  26     return s->ops->lstat(&s->ctx, path->data, stbuf);
  27 }
  28
  29 static int v9fs_do_setuid(V9fsState *s, uid_t uid)
  30 {
  31     return s->ops->setuid(&s->ctx, uid);
  32 }
  33
  34 static ssize_t v9fs_do_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
  35 {
  36     ssize_t len;
  37
  38     buf->data = qemu_malloc(1024);
  39
  40     len = s->ops->readlink(&s->ctx, path->data, buf->data, 1024 - 1);
  41     if (len > -1) {
  42         buf->size = len;
  43         buf->data[len] = 0;
  44     }
  45
  46     return len;
  47 }
  48
  49 static int v9fs_do_close(V9fsState *s, int fd)
  50 {
  51     return s->ops->close(&s->ctx, fd);
  52 }
  53
  54 static int v9fs_do_closedir(V9fsState *s, DIR *dir)
  55 {
  56     return s->ops->closedir(&s->ctx, dir);
  57 }
  58
  59 static int v9fs_do_open(V9fsState *s, V9fsString *path, int flags)
  60 {
  61     return s->ops->open(&s->ctx, path->data, flags);
  62 }
  63
  64 static DIR *v9fs_do_opendir(V9fsState *s, V9fsString *path)
  65 {
  66     return s->ops->opendir(&s->ctx, path->data);
  67 }
  68
  69 static void v9fs_string_init(V9fsString *str)
  70 {
  71     str->data = NULL;
  72     str->size = 0;
  73 }
  74
  75 static void v9fs_string_free(V9fsString *str)
  76 {
  77     qemu_free(str->data);
  78     str->data = NULL;
  79     str->size = 0;
  80 }
  81
  82 static void v9fs_string_null(V9fsString *str)
  83 {
  84     v9fs_string_free(str);
  85 }
  86
  87 static int number_to_string(void *arg, char type)
  88 {
  89     unsigned int ret = 0;
  90
  91     switch (type) {
  92     case 'u': {
  93         unsigned int num = *(unsigned int *)arg;
  94
  95         do {
  96             ret++;
  97             num = num/10;
  98         } while (num);
  99         break;
 100     }
 101     default:
 102         printf("Number_to_string: Unknown number format\n");
 103         return -1;
 104     }
 105
 106     return ret;
 107 }
 108
 109 static int v9fs_string_alloc_printf(char **strp, const char *fmt, va_list ap)
 110 {
 111     va_list ap2;
 112     char *iter = (char *)fmt;
 113     int len = 0;
 114     int nr_args = 0;
 115     char *arg_char_ptr;
 116     unsigned int arg_uint;
 117
 118     /* Find the number of %'s that denotes an argument */
 119     for (iter = strstr(iter, "%"); iter; iter = strstr(iter, "%")) {
 120         nr_args++;
 121         iter++;
 122     }
 123
 124     len = strlen(fmt) - 2*nr_args;
 125
 126     if (!nr_args) {
 127         goto alloc_print;
 128     }
 129
 130     va_copy(ap2, ap);
 131
 132     iter = (char *)fmt;
 133
 134     /* Now parse the format string */
 135     for (iter = strstr(iter, "%"); iter; iter = strstr(iter, "%")) {
 136         iter++;
 137         switch (*iter) {
 138         case 'u':
 139             arg_uint = va_arg(ap2, unsigned int);
 140             len += number_to_string((void *)&arg_uint, 'u');
 141             break;
 142         case 's':
 143             arg_char_ptr = va_arg(ap2, char *);
 144             len += strlen(arg_char_ptr);
 145             break;
 146         case 'c':
 147             len += 1;
 148             break;
 149         default:
 150             fprintf(stderr,
 151                     "v9fs_string_alloc_printf:Incorrect format %c", *iter);
 152             return -1;
 153         }
 154         iter++;
 155     }
 156
 157 alloc_print:
 158     *strp = qemu_malloc((len + 1) * sizeof(**strp));
 159
 160     return vsprintf(*strp, fmt, ap);
 161 }
 162
 163 static void v9fs_string_sprintf(V9fsString *str, const char *fmt, ...)
 164 {
 165     va_list ap;
 166     int err;
 167
 168     v9fs_string_free(str);
 169
 170     va_start(ap, fmt);
 171     err = v9fs_string_alloc_printf(&str->data, fmt, ap);
 172     BUG_ON(err == -1);
 173     va_end(ap);
 174
 175     str->size = err;
 176 }
 177
 178 static void v9fs_string_copy(V9fsString *lhs, V9fsString *rhs)
 179 {
 180     v9fs_string_free(lhs);
 181     v9fs_string_sprintf(lhs, "%s", rhs->data);
 182 }
 183
 184 static size_t v9fs_string_size(V9fsString *str)
 185 {
 186     return str->size;
 187 }
 188
 189 static V9fsFidState *lookup_fid(V9fsState *s, int32_t fid)
 190 {
 191     V9fsFidState *f;
 192
 193     for (f = s->fid_list; f; f = f->next) {
 194         if (f->fid == fid) {
 195             v9fs_do_setuid(s, f->uid);
 196             return f;
 197         }
 198     }
 199
 200     return NULL;
 201 }
 202
 203 static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid)
 204 {
 205     V9fsFidState *f;
 206
 207     f = lookup_fid(s, fid);
 208     if (f) {
 209         return NULL;
 210     }
 211
 212     f = qemu_mallocz(sizeof(V9fsFidState));
 213
 214     f->fid = fid;
 215     f->fd = -1;
 216     f->dir = NULL;
 217
 218     f->next = s->fid_list;
 219     s->fid_list = f;
 220
 221     return f;
 222 }
 223
 224 static int free_fid(V9fsState *s, int32_t fid)
 225 {
 226     V9fsFidState **fidpp, *fidp;
 227
 228     for (fidpp = &s->fid_list; *fidpp; fidpp = &(*fidpp)->next) {
 229         if ((*fidpp)->fid == fid) {
 230             break;
 231         }
 232     }
 233
 234     if (*fidpp == NULL) {
 235         return -ENOENT;
 236     }
 237
 238     fidp = *fidpp;
 239     *fidpp = fidp->next;
 240
 241     if (fidp->fd != -1) {
 242         v9fs_do_close(s, fidp->fd);
 243     }
 244     if (fidp->dir) {
 245         v9fs_do_closedir(s, fidp->dir);
 246     }
 247     v9fs_string_free(&fidp->path);
 248     qemu_free(fidp);
 249
 250     return 0;
 251 }
 252
 253 #define P9_QID_TYPE_DIR         0x80
 254 #define P9_QID_TYPE_SYMLINK     0x02
 255
 256 #define P9_STAT_MODE_DIR        0x80000000
 257 #define P9_STAT_MODE_APPEND     0x40000000
 258 #define P9_STAT_MODE_EXCL       0x20000000
 259 #define P9_STAT_MODE_MOUNT      0x10000000
 260 #define P9_STAT_MODE_AUTH       0x08000000
 261 #define P9_STAT_MODE_TMP        0x04000000
 262 #define P9_STAT_MODE_SYMLINK    0x02000000
 263 #define P9_STAT_MODE_LINK       0x01000000
 264 #define P9_STAT_MODE_DEVICE     0x00800000
 265 #define P9_STAT_MODE_NAMED_PIPE 0x00200000
 266 #define P9_STAT_MODE_SOCKET     0x00100000
 267 #define P9_STAT_MODE_SETUID     0x00080000
 268 #define P9_STAT_MODE_SETGID     0x00040000
 269 #define P9_STAT_MODE_SETVTX     0x00010000
 270
 271 #define P9_STAT_MODE_TYPE_BITS (P9_STAT_MODE_DIR |          \
 272                                 P9_STAT_MODE_SYMLINK |      \
 273                                 P9_STAT_MODE_LINK |         \
 274                                 P9_STAT_MODE_DEVICE |       \
 275                                 P9_STAT_MODE_NAMED_PIPE |   \
 276                                 P9_STAT_MODE_SOCKET)
 277
 278 /* This is the algorithm from ufs in spfs */
 279 static void stat_to_qid(const struct stat *stbuf, V9fsQID *qidp)
 280 {
 281     size_t size;
 282
 283     size = MIN(sizeof(stbuf->st_ino), sizeof(qidp->path));
 284     memcpy(&qidp->path, &stbuf->st_ino, size);
 285     qidp->version = stbuf->st_mtime ^ (stbuf->st_size << 8);
 286     qidp->type = 0;
 287     if (S_ISDIR(stbuf->st_mode)) {
 288         qidp->type |= P9_QID_TYPE_DIR;
 289     }
 290     if (S_ISLNK(stbuf->st_mode)) {
 291         qidp->type |= P9_QID_TYPE_SYMLINK;
 292     }
 293 }
 294
 295 static int fid_to_qid(V9fsState *s, V9fsFidState *fidp, V9fsQID *qidp)
 296 {
 297     struct stat stbuf;
 298     int err;
 299
 300     err = v9fs_do_lstat(s, &fidp->path, &stbuf);
 301     if (err) {
 302         return err;
 303     }
 304
 305     stat_to_qid(&stbuf, qidp);
 306     return 0;
 307 }
 308
 309 static V9fsPDU *alloc_pdu(V9fsState *s)
 310 {
 311     V9fsPDU *pdu = NULL;
 312
 313     if (!QLIST_EMPTY(&s->free_list)) {
 314         pdu = QLIST_FIRST(&s->free_list);
 315         QLIST_REMOVE(pdu, next);
 316     }
 317     return pdu;
 318 }
 319
 320 static void free_pdu(V9fsState *s, V9fsPDU *pdu)
 321 {
 322     if (pdu) {
 323         QLIST_INSERT_HEAD(&s->free_list, pdu, next);
 324     }
 325 }
 326
 327 size_t pdu_packunpack(void *addr, struct iovec *sg, int sg_count,
 328                         size_t offset, size_t size, int pack)
 329 {
 330     int i = 0;
 331     size_t copied = 0;
 332
 333     for (i = 0; size && i < sg_count; i++) {
 334         size_t len;
 335         if (offset >= sg[i].iov_len) {
 336             /* skip this sg */
 337             offset -= sg[i].iov_len;
 338             continue;
 339         } else {
 340             len = MIN(sg[i].iov_len - offset, size);
 341             if (pack) {
 342                 memcpy(sg[i].iov_base + offset, addr, len);
 343             } else {
 344                 memcpy(addr, sg[i].iov_base + offset, len);
 345             }
 346             size -= len;
 347             copied += len;
 348             addr += len;
 349             if (size) {
 350                 offset = 0;
 351                 continue;
 352             }
 353         }
 354     }
 355
 356     return copied;
 357 }
 358
 359 static size_t pdu_unpack(void *dst, V9fsPDU *pdu, size_t offset, size_t size)
 360 {
 361     return pdu_packunpack(dst, pdu->elem.out_sg, pdu->elem.out_num,
 362                          offset, size, 0);
 363 }
 364
 365 static size_t pdu_pack(V9fsPDU *pdu, size_t offset, const void *src,
 366                         size_t size)
 367 {
 368     return pdu_packunpack((void *)src, pdu->elem.in_sg, pdu->elem.in_num,
 369                              offset, size, 1);
 370 }
 371
 372 static int pdu_copy_sg(V9fsPDU *pdu, size_t offset, int rx, struct iovec *sg)
 373 {
 374     size_t pos = 0;
 375     int i, j;
 376     struct iovec *src_sg;
 377     unsigned int num;
 378
 379     if (rx) {
 380         src_sg = pdu->elem.in_sg;
 381         num = pdu->elem.in_num;
 382     } else {
 383         src_sg = pdu->elem.out_sg;
 384         num = pdu->elem.out_num;
 385     }
 386
 387     j = 0;
 388     for (i = 0; i < num; i++) {
 389         if (offset <= pos) {
 390             sg[j].iov_base = src_sg[i].iov_base;
 391             sg[j].iov_len = src_sg[i].iov_len;
 392             j++;
 393         } else if (offset < (src_sg[i].iov_len + pos)) {
 394             sg[j].iov_base = src_sg[i].iov_base;
 395             sg[j].iov_len = src_sg[i].iov_len;
 396             sg[j].iov_base += (offset - pos);
 397             sg[j].iov_len -= (offset - pos);
 398             j++;
 399         }
 400         pos += src_sg[i].iov_len;
 401     }
 402
 403     return j;
 404 }
 405
 406 static size_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
 407 {
 408     size_t old_offset = offset;
 409     va_list ap;
 410     int i;
 411
 412     va_start(ap, fmt);
 413     for (i = 0; fmt[i]; i++) {
 414         switch (fmt[i]) {
 415         case 'b': {
 416             uint8_t *valp = va_arg(ap, uint8_t *);
 417             offset += pdu_unpack(valp, pdu, offset, sizeof(*valp));
 418             break;
 419         }
 420         case 'w': {
 421             uint16_t val, *valp;
 422             valp = va_arg(ap, uint16_t *);
 423             val = le16_to_cpupu(valp);
 424             offset += pdu_unpack(&val, pdu, offset, sizeof(val));
 425             *valp = val;
 426             break;
 427         }
 428         case 'd': {
 429             uint32_t val, *valp;
 430             valp = va_arg(ap, uint32_t *);
 431             val = le32_to_cpupu(valp);
 432             offset += pdu_unpack(&val, pdu, offset, sizeof(val));
 433             *valp = val;
 434             break;
 435         }
 436         case 'q': {
 437             uint64_t val, *valp;
 438             valp = va_arg(ap, uint64_t *);
 439             val = le64_to_cpup(valp);
 440             offset += pdu_unpack(&val, pdu, offset, sizeof(val));
 441             *valp = val;
 442             break;
 443         }
 444         case 'v': {
 445             struct iovec *iov = va_arg(ap, struct iovec *);
 446             int *iovcnt = va_arg(ap, int *);
 447             *iovcnt = pdu_copy_sg(pdu, offset, 0, iov);
 448             break;
 449         }
 450         case 's': {
 451             V9fsString *str = va_arg(ap, V9fsString *);
 452             offset += pdu_unmarshal(pdu, offset, "w", &str->size);
 453             /* FIXME: sanity check str->size */
 454             str->data = qemu_malloc(str->size + 1);
 455             offset += pdu_unpack(str->data, pdu, offset, str->size);
 456             str->data[str->size] = 0;
 457             break;
 458         }
 459         case 'Q': {
 460             V9fsQID *qidp = va_arg(ap, V9fsQID *);
 461             offset += pdu_unmarshal(pdu, offset, "bdq",
 462                         &qidp->type, &qidp->version, &qidp->path);
 463             break;
 464         }
 465         case 'S': {
 466             V9fsStat *statp = va_arg(ap, V9fsStat *);
 467             offset += pdu_unmarshal(pdu, offset, "wwdQdddqsssssddd",
 468                         &statp->size, &statp->type, &statp->dev,
 469                         &statp->qid, &statp->mode, &statp->atime,
 470                         &statp->mtime, &statp->length,
 471                         &statp->name, &statp->uid, &statp->gid,
 472                         &statp->muid, &statp->extension,
 473                         &statp->n_uid, &statp->n_gid,
 474                         &statp->n_muid);
 475             break;
 476         }
 477         default:
 478             break;
 479         }
 480     }
 481
 482     va_end(ap);
 483
 484     return offset - old_offset;
 485 }
 486
 487 static size_t pdu_marshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
 488 {
 489     size_t old_offset = offset;
 490     va_list ap;
 491     int i;
 492
 493     va_start(ap, fmt);
 494     for (i = 0; fmt[i]; i++) {
 495         switch (fmt[i]) {
 496         case 'b': {
 497             uint8_t val = va_arg(ap, int);
 498             offset += pdu_pack(pdu, offset, &val, sizeof(val));
 499             break;
 500         }
 501         case 'w': {
 502             uint16_t val;
 503             cpu_to_le16w(&val, va_arg(ap, int));
 504             offset += pdu_pack(pdu, offset, &val, sizeof(val));
 505             break;
 506         }
 507         case 'd': {
 508             uint32_t val;
 509             cpu_to_le32w(&val, va_arg(ap, uint32_t));
 510             offset += pdu_pack(pdu, offset, &val, sizeof(val));
 511             break;
 512         }
 513         case 'q': {
 514             uint64_t val;
 515             cpu_to_le64w(&val, va_arg(ap, uint64_t));
 516             offset += pdu_pack(pdu, offset, &val, sizeof(val));
 517             break;
 518         }
 519         case 'v': {
 520             struct iovec *iov = va_arg(ap, struct iovec *);
 521             int *iovcnt = va_arg(ap, int *);
 522             *iovcnt = pdu_copy_sg(pdu, offset, 1, iov);
 523             break;
 524         }
 525         case 's': {
 526             V9fsString *str = va_arg(ap, V9fsString *);
 527             offset += pdu_marshal(pdu, offset, "w", str->size);
 528             offset += pdu_pack(pdu, offset, str->data, str->size);
 529             break;
 530         }
 531         case 'Q': {
 532             V9fsQID *qidp = va_arg(ap, V9fsQID *);
 533             offset += pdu_marshal(pdu, offset, "bdq",
 534                         qidp->type, qidp->version, qidp->path);
 535             break;
 536         }
 537         case 'S': {
 538             V9fsStat *statp = va_arg(ap, V9fsStat *);
 539             offset += pdu_marshal(pdu, offset, "wwdQdddqsssssddd",
 540                         statp->size, statp->type, statp->dev,
 541                         &statp->qid, statp->mode, statp->atime,
 542                         statp->mtime, statp->length, &statp->name,
 543                         &statp->uid, &statp->gid, &statp->muid,
 544                         &statp->extension, statp->n_uid,
 545                         statp->n_gid, statp->n_muid);
 546             break;
 547         }
 548         default:
 549             break;
 550         }
 551     }
 552     va_end(ap);
 553
 554     return offset - old_offset;
 555 }
 556
 557 static void complete_pdu(V9fsState *s, V9fsPDU *pdu, ssize_t len)
 558 {
 559     int8_t id = pdu->id + 1; /* Response */
 560
 561     if (len < 0) {
 562         V9fsString str;
 563         int err = -len;
 564
 565         str.data = strerror(err);
 566         str.size = strlen(str.data);
 567
 568         len = 7;
 569         len += pdu_marshal(pdu, len, "s", &str);
 570         if (dotu) {
 571             len += pdu_marshal(pdu, len, "d", err);
 572         }
 573
 574         id = P9_RERROR;
 575     }
 576
 577     /* fill out the header */
 578     pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag);
 579
 580     /* keep these in sync */
 581     pdu->size = len;
 582     pdu->id = id;
 583
 584     /* push onto queue and notify */
 585     virtqueue_push(s->vq, &pdu->elem, len);
 586
 587     /* FIXME: we should batch these completions */
 588     virtio_notify(&s->vdev, s->vq);
 589
 590     free_pdu(s, pdu);
 591 }
 592
 593 static mode_t v9mode_to_mode(uint32_t mode, V9fsString *extension)
 594 {
 595     mode_t ret;
 596
 597     ret = mode & 0777;
 598     if (mode & P9_STAT_MODE_DIR) {
 599         ret |= S_IFDIR;
 600     }
 601
 602     if (dotu) {
 603         if (mode & P9_STAT_MODE_SYMLINK) {
 604             ret |= S_IFLNK;
 605         }
 606         if (mode & P9_STAT_MODE_SOCKET) {
 607             ret |= S_IFSOCK;
 608         }
 609         if (mode & P9_STAT_MODE_NAMED_PIPE) {
 610             ret |= S_IFIFO;
 611         }
 612         if (mode & P9_STAT_MODE_DEVICE) {
 613             if (extension && extension->data[0] == 'c') {
 614                 ret |= S_IFCHR;
 615             } else {
 616                 ret |= S_IFBLK;
 617             }
 618         }
 619     }
 620
 621     if (!(ret&~0777)) {
 622         ret |= S_IFREG;
 623     }
 624
 625     if (mode & P9_STAT_MODE_SETUID) {
 626         ret |= S_ISUID;
 627     }
 628     if (mode & P9_STAT_MODE_SETGID) {
 629         ret |= S_ISGID;
 630     }
 631     if (mode & P9_STAT_MODE_SETVTX) {
 632         ret |= S_ISVTX;
 633     }
 634
 635     return ret;
 636 }
 637
 638 static int donttouch_stat(V9fsStat *stat)
 639 {
 640     if (stat->type == -1 &&
 641         stat->dev == -1 &&
 642         stat->qid.type == -1 &&
 643         stat->qid.version == -1 &&
 644         stat->qid.path == -1 &&
 645         stat->mode == -1 &&
 646         stat->atime == -1 &&
 647         stat->mtime == -1 &&
 648         stat->length == -1 &&
 649         !stat->name.size &&
 650         !stat->uid.size &&
 651         !stat->gid.size &&
 652         !stat->muid.size &&
 653         stat->n_uid == -1 &&
 654         stat->n_gid == -1 &&
 655         stat->n_muid == -1) {
 656         return 1;
 657     }
 658
 659     return 0;
 660 }
 661
 662 static void v9fs_stat_free(V9fsStat *stat)
 663 {
 664     v9fs_string_free(&stat->name);
 665     v9fs_string_free(&stat->uid);
 666     v9fs_string_free(&stat->gid);
 667     v9fs_string_free(&stat->muid);
 668     v9fs_string_free(&stat->extension);
 669 }
 670
 671 static uint32_t stat_to_v9mode(const struct stat *stbuf)
 672 {
 673     uint32_t mode;
 674
 675     mode = stbuf->st_mode & 0777;
 676     if (S_ISDIR(stbuf->st_mode)) {
 677         mode |= P9_STAT_MODE_DIR;
 678     }
 679
 680     if (dotu) {
 681         if (S_ISLNK(stbuf->st_mode)) {
 682             mode |= P9_STAT_MODE_SYMLINK;
 683         }
 684
 685         if (S_ISSOCK(stbuf->st_mode)) {
 686             mode |= P9_STAT_MODE_SOCKET;
 687         }
 688
 689         if (S_ISFIFO(stbuf->st_mode)) {
 690             mode |= P9_STAT_MODE_NAMED_PIPE;
 691         }
 692
 693         if (S_ISBLK(stbuf->st_mode) || S_ISCHR(stbuf->st_mode)) {
 694             mode |= P9_STAT_MODE_DEVICE;
 695         }
 696
 697         if (stbuf->st_mode & S_ISUID) {
 698             mode |= P9_STAT_MODE_SETUID;
 699         }
 700
 701         if (stbuf->st_mode & S_ISGID) {
 702             mode |= P9_STAT_MODE_SETGID;
 703         }
 704
 705         if (stbuf->st_mode & S_ISVTX) {
 706             mode |= P9_STAT_MODE_SETVTX;
 707         }
 708     }
 709
 710     return mode;
 711 }
 712
 713 static int stat_to_v9stat(V9fsState *s, V9fsString *name,
 714                             const struct stat *stbuf,
 715                             V9fsStat *v9stat)
 716 {
 717     int err;
 718     const char *str;
 719
 720     memset(v9stat, 0, sizeof(*v9stat));
 721
 722     stat_to_qid(stbuf, &v9stat->qid);
 723     v9stat->mode = stat_to_v9mode(stbuf);
 724     v9stat->atime = stbuf->st_atime;
 725     v9stat->mtime = stbuf->st_mtime;
 726     v9stat->length = stbuf->st_size;
 727
 728     v9fs_string_null(&v9stat->uid);
 729     v9fs_string_null(&v9stat->gid);
 730     v9fs_string_null(&v9stat->muid);
 731
 732     if (dotu) {
 733         v9stat->n_uid = stbuf->st_uid;
 734         v9stat->n_gid = stbuf->st_gid;
 735         v9stat->n_muid = 0;
 736
 737         v9fs_string_null(&v9stat->extension);
 738
 739         if (v9stat->mode & P9_STAT_MODE_SYMLINK) {
 740             err = v9fs_do_readlink(s, name, &v9stat->extension);
 741             if (err == -1) {
 742                 err = -errno;
 743                 return err;
 744             }
 745             v9stat->extension.data[err] = 0;
 746             v9stat->extension.size = err;
 747         } else if (v9stat->mode & P9_STAT_MODE_DEVICE) {
 748             v9fs_string_sprintf(&v9stat->extension, "%c %u %u",
 749                     S_ISCHR(stbuf->st_mode) ? 'c' : 'b',
 750                     major(stbuf->st_rdev), minor(stbuf->st_rdev));
 751         } else if (S_ISDIR(stbuf->st_mode) || S_ISREG(stbuf->st_mode)) {
 752             v9fs_string_sprintf(&v9stat->extension, "%s %u",
 753                     "HARDLINKCOUNT", stbuf->st_nlink);
 754         }
 755     }
 756
 757     str = strrchr(name->data, '/');
 758     if (str) {
 759         str += 1;
 760     } else {
 761         str = name->data;
 762     }
 763
 764     v9fs_string_sprintf(&v9stat->name, "%s", str);
 765
 766     v9stat->size = 61 +
 767         v9fs_string_size(&v9stat->name) +
 768         v9fs_string_size(&v9stat->uid) +
 769         v9fs_string_size(&v9stat->gid) +
 770         v9fs_string_size(&v9stat->muid) +
 771         v9fs_string_size(&v9stat->extension);
 772     return 0;
 773 }
 774
 775 static struct iovec *adjust_sg(struct iovec *sg, int len, int *iovcnt)
 776 {
 777     while (len && *iovcnt) {
 778         if (len < sg->iov_len) {
 779             sg->iov_len -= len;
 780             sg->iov_base += len;
 781             len = 0;
 782         } else {
 783             len -= sg->iov_len;
 784             sg++;
 785             *iovcnt -= 1;
 786         }
 787     }
 788
 789     return sg;
 790 }
 791
 792 static struct iovec *cap_sg(struct iovec *sg, int cap, int *cnt)
 793 {
 794     int i;
 795     int total = 0;
 796
 797     for (i = 0; i < *cnt; i++) {
 798         if ((total + sg[i].iov_len) > cap) {
 799             sg[i].iov_len -= ((total + sg[i].iov_len) - cap);
 800             i++;
 801             break;
 802         }
 803         total += sg[i].iov_len;
 804     }
 805
 806     *cnt = i;
 807
 808     return sg;
 809 }
 810
 811 static void print_sg(struct iovec *sg, int cnt)
 812 {
 813     int i;
 814
 815     printf("sg[%d]: {", cnt);
 816     for (i = 0; i < cnt; i++) {
 817         if (i) {
 818             printf(", ");
 819         }
 820         printf("(%p, %zd)", sg[i].iov_base, sg[i].iov_len);
 821     }
 822     printf("}\n");
 823 }
 824
 825 static void v9fs_dummy(V9fsState *s, V9fsPDU *pdu)
 826 {
 827     /* Note: The following have been added to prevent GCC from complaining
 828      * They will be removed in the subsequent patches */
 829     (void)pdu_unmarshal;
 830     (void) complete_pdu;
 831     (void) v9fs_string_init;
 832     (void) v9fs_string_free;
 833     (void) v9fs_string_null;
 834     (void) v9fs_string_sprintf;
 835     (void) v9fs_string_copy;
 836     (void) v9fs_string_size;
 837     (void) v9fs_do_lstat;
 838     (void) v9fs_do_setuid;
 839     (void) v9fs_do_readlink;
 840     (void) v9fs_do_close;
 841     (void) v9fs_do_closedir;
 842     (void) alloc_fid;
 843     (void) free_fid;
 844     (void) fid_to_qid;
 845     (void) v9mode_to_mode;
 846     (void) donttouch_stat;
 847     (void) v9fs_stat_free;
 848     (void) stat_to_v9stat;
 849     (void) adjust_sg;
 850     (void) cap_sg;
 851     (void) print_sg;
 852 }
 853
 854 static void v9fs_version(V9fsState *s, V9fsPDU *pdu)
 855 {
 856     int32_t msize;
 857     V9fsString version;
 858     size_t offset = 7;
 859
 860     pdu_unmarshal(pdu, offset, "ds", &msize, &version);
 861
 862     if (strcmp(version.data, "9P2000.u")) {
 863         v9fs_string_sprintf(&version, "unknown");
 864     }
 865
 866     offset += pdu_marshal(pdu, offset, "ds", msize, &version);
 867     complete_pdu(s, pdu, offset);
 868
 869     v9fs_string_free(&version);
 870 }
 871
 872 static void v9fs_attach(V9fsState *s, V9fsPDU *pdu)
 873 {
 874     int32_t fid, afid, n_uname;
 875     V9fsString uname, aname;
 876     V9fsFidState *fidp;
 877     V9fsQID qid;
 878     size_t offset = 7;
 879     ssize_t err;
 880
 881     pdu_unmarshal(pdu, offset, "ddssd", &fid, &afid, &uname, &aname, &n_uname);
 882
 883     fidp = alloc_fid(s, fid);
 884     if (fidp == NULL) {
 885         err = -EINVAL;
 886         goto out;
 887     }
 888
 889     fidp->uid = n_uname;
 890
 891     v9fs_string_sprintf(&fidp->path, "%s", "/");
 892     err = fid_to_qid(s, fidp, &qid);
 893     if (err) {
 894         err = -EINVAL;
 895         free_fid(s, fid);
 896         goto out;
 897     }
 898
 899     offset += pdu_marshal(pdu, offset, "Q", &qid);
 900
 901     err = offset;
 902 out:
 903     complete_pdu(s, pdu, err);
 904     v9fs_string_free(&uname);
 905     v9fs_string_free(&aname);
 906 }
 907
 908 typedef struct V9fsStatState {
 909     V9fsPDU *pdu;
 910     size_t offset;
 911     V9fsStat v9stat;
 912     V9fsFidState *fidp;
 913     struct stat stbuf;
 914 } V9fsStatState;
 915
 916 static void v9fs_stat_post_lstat(V9fsState *s, V9fsStatState *vs, int err)
 917 {
 918     if (err == -1) {
 919         err = -errno;
 920         goto out;
 921     }
 922
 923     err = stat_to_v9stat(s, &vs->fidp->path, &vs->stbuf, &vs->v9stat);
 924     if (err) {
 925         goto out;
 926     }
 927     vs->offset += pdu_marshal(vs->pdu, vs->offset, "wS", 0, &vs->v9stat);
 928     err = vs->offset;
 929
 930 out:
 931     complete_pdu(s, vs->pdu, err);
 932     v9fs_stat_free(&vs->v9stat);
 933     qemu_free(vs);
 934 }
 935
 936 static void v9fs_stat(V9fsState *s, V9fsPDU *pdu)
 937 {
 938     int32_t fid;
 939     V9fsStatState *vs;
 940     ssize_t err = 0;
 941
 942     vs = qemu_malloc(sizeof(*vs));
 943     vs->pdu = pdu;
 944     vs->offset = 7;
 945
 946     memset(&vs->v9stat, 0, sizeof(vs->v9stat));
 947
 948     pdu_unmarshal(vs->pdu, vs->offset, "d", &fid);
 949
 950     vs->fidp = lookup_fid(s, fid);
 951     if (vs->fidp == NULL) {
 952         err = -ENOENT;
 953         goto out;
 954     }
 955
 956     err = v9fs_do_lstat(s, &vs->fidp->path, &vs->stbuf);
 957     v9fs_stat_post_lstat(s, vs, err);
 958     return;
 959
 960 out:
 961     complete_pdu(s, vs->pdu, err);
 962     v9fs_stat_free(&vs->v9stat);
 963     qemu_free(vs);
 964 }
 965
 966 typedef struct V9fsWalkState {
 967     V9fsPDU *pdu;
 968     size_t offset;
 969     int16_t nwnames;
 970     int name_idx;
 971     V9fsQID *qids;
 972     V9fsFidState *fidp;
 973     V9fsFidState *newfidp;
 974     V9fsString path;
 975     V9fsString *wnames;
 976     struct stat stbuf;
 977 } V9fsWalkState;
 978
 979 static void v9fs_walk_complete(V9fsState *s, V9fsWalkState *vs, int err)
 980 {
 981     complete_pdu(s, vs->pdu, err);
 982
 983     if (vs->nwnames) {
 984         for (vs->name_idx = 0; vs->name_idx < vs->nwnames; vs->name_idx++) {
 985             v9fs_string_free(&vs->wnames[vs->name_idx]);
 986         }
 987
 988         qemu_free(vs->wnames);
 989         qemu_free(vs->qids);
 990     }
 991 }
 992
 993 static void v9fs_walk_marshal(V9fsWalkState *vs)
 994 {
 995     int i;
 996     vs->offset = 7;
 997     vs->offset += pdu_marshal(vs->pdu, vs->offset, "w", vs->nwnames);
 998
 999     for (i = 0; i < vs->nwnames; i++) {
1000         vs->offset += pdu_marshal(vs->pdu, vs->offset, "Q", &vs->qids[i]);
1001     }
1002 }
1003
1004 static void v9fs_walk_post_newfid_lstat(V9fsState *s, V9fsWalkState *vs,
1005                                                                 int err)
1006 {
1007     if (err == -1) {
1008         free_fid(s, vs->newfidp->fid);
1009         v9fs_string_free(&vs->path);
1010         err = -ENOENT;
1011         goto out;
1012     }
1013
1014     stat_to_qid(&vs->stbuf, &vs->qids[vs->name_idx]);
1015
1016     vs->name_idx++;
1017     if (vs->name_idx < vs->nwnames) {
1018         v9fs_string_sprintf(&vs->path, "%s/%s", vs->newfidp->path.data,
1019                                             vs->wnames[vs->name_idx].data);
1020         v9fs_string_copy(&vs->newfidp->path, &vs->path);
1021
1022         err = v9fs_do_lstat(s, &vs->newfidp->path, &vs->stbuf);
1023         v9fs_walk_post_newfid_lstat(s, vs, err);
1024         return;
1025     }
1026
1027     v9fs_string_free(&vs->path);
1028     v9fs_walk_marshal(vs);
1029     err = vs->offset;
1030 out:
1031     v9fs_walk_complete(s, vs, err);
1032 }
1033
1034 static void v9fs_walk_post_oldfid_lstat(V9fsState *s, V9fsWalkState *vs,
1035         int err)
1036 {
1037     if (err == -1) {
1038         v9fs_string_free(&vs->path);
1039         err = -ENOENT;
1040         goto out;
1041     }
1042
1043     stat_to_qid(&vs->stbuf, &vs->qids[vs->name_idx]);
1044     vs->name_idx++;
1045     if (vs->name_idx < vs->nwnames) {
1046
1047         v9fs_string_sprintf(&vs->path, "%s/%s",
1048                 vs->fidp->path.data, vs->wnames[vs->name_idx].data);
1049         v9fs_string_copy(&vs->fidp->path, &vs->path);
1050
1051         err = v9fs_do_lstat(s, &vs->fidp->path, &vs->stbuf);
1052         v9fs_walk_post_oldfid_lstat(s, vs, err);
1053         return;
1054     }
1055
1056     v9fs_string_free(&vs->path);
1057     v9fs_walk_marshal(vs);
1058     err = vs->offset;
1059 out:
1060     v9fs_walk_complete(s, vs, err);
1061 }
1062
1063 static void v9fs_walk(V9fsState *s, V9fsPDU *pdu)
1064 {
1065     int32_t fid, newfid;
1066     V9fsWalkState *vs;
1067     int err = 0;
1068     int i;
1069
1070     vs = qemu_malloc(sizeof(*vs));
1071     vs->pdu = pdu;
1072     vs->wnames = NULL;
1073     vs->qids = NULL;
1074     vs->offset = 7;
1075
1076     vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "ddw", &fid,
1077                                             &newfid, &vs->nwnames);
1078
1079     if (vs->nwnames) {
1080         vs->wnames = qemu_mallocz(sizeof(vs->wnames[0]) * vs->nwnames);
1081
1082         vs->qids = qemu_mallocz(sizeof(vs->qids[0]) * vs->nwnames);
1083
1084         for (i = 0; i < vs->nwnames; i++) {
1085             vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "s",
1086                                             &vs->wnames[i]);
1087         }
1088     }
1089
1090     vs->fidp = lookup_fid(s, fid);
1091     if (vs->fidp == NULL) {
1092         err = -ENOENT;
1093         goto out;
1094     }
1095
1096     /* FIXME: is this really valid? */
1097     if (fid == newfid) {
1098
1099         BUG_ON(vs->fidp->fd != -1);
1100         BUG_ON(vs->fidp->dir);
1101         v9fs_string_init(&vs->path);
1102         vs->name_idx = 0;
1103
1104         if (vs->name_idx < vs->nwnames) {
1105             v9fs_string_sprintf(&vs->path, "%s/%s",
1106                 vs->fidp->path.data, vs->wnames[vs->name_idx].data);
1107             v9fs_string_copy(&vs->fidp->path, &vs->path);
1108
1109             err = v9fs_do_lstat(s, &vs->fidp->path, &vs->stbuf);
1110             v9fs_walk_post_oldfid_lstat(s, vs, err);
1111             return;
1112         }
1113     } else {
1114         vs->newfidp = alloc_fid(s, newfid);
1115         if (vs->newfidp == NULL) {
1116             err = -EINVAL;
1117             goto out;
1118         }
1119
1120         vs->newfidp->uid = vs->fidp->uid;
1121         v9fs_string_init(&vs->path);
1122         vs->name_idx = 0;
1123         v9fs_string_copy(&vs->newfidp->path, &vs->fidp->path);
1124
1125         if (vs->name_idx < vs->nwnames) {
1126             v9fs_string_sprintf(&vs->path, "%s/%s", vs->newfidp->path.data,
1127                                 vs->wnames[vs->name_idx].data);
1128             v9fs_string_copy(&vs->newfidp->path, &vs->path);
1129
1130             err = v9fs_do_lstat(s, &vs->newfidp->path, &vs->stbuf);
1131             v9fs_walk_post_newfid_lstat(s, vs, err);
1132             return;
1133         }
1134     }
1135
1136     v9fs_walk_marshal(vs);
1137     err = vs->offset;
1138 out:
1139     v9fs_walk_complete(s, vs, err);
1140 }
1141
1142 typedef struct V9fsOpenState {
1143     V9fsPDU *pdu;
1144     size_t offset;
1145     int8_t mode;
1146     V9fsFidState *fidp;
1147     V9fsQID qid;
1148     struct stat stbuf;
1149
1150 } V9fsOpenState;
1151
1152 enum {
1153     Oread   = 0x00,
1154     Owrite  = 0x01,
1155     Ordwr   = 0x02,
1156     Oexec   = 0x03,
1157     Oexcl   = 0x04,
1158     Otrunc  = 0x10,
1159     Orexec  = 0x20,
1160     Orclose = 0x40,
1161     Oappend = 0x80,
1162 };
1163
1164 static int omode_to_uflags(int8_t mode)
1165 {
1166     int ret = 0;
1167
1168     switch (mode & 3) {
1169     case Oread:
1170         ret = O_RDONLY;
1171         break;
1172     case Ordwr:
1173         ret = O_RDWR;
1174         break;
1175     case Owrite:
1176         ret = O_WRONLY;
1177         break;
1178     case Oexec:
1179         ret = O_RDONLY;
1180         break;
1181     }
1182
1183     if (mode & Otrunc) {
1184         ret |= O_TRUNC;
1185     }
1186
1187     if (mode & Oappend) {
1188         ret |= O_APPEND;
1189     }
1190
1191     if (mode & Oexcl) {
1192         ret |= O_EXCL;
1193     }
1194
1195     return ret;
1196 }
1197
1198 static void v9fs_open_post_opendir(V9fsState *s, V9fsOpenState *vs, int err)
1199 {
1200     if (vs->fidp->dir == NULL) {
1201         err = -errno;
1202         goto out;
1203     }
1204
1205     vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, 0);
1206     err = vs->offset;
1207 out:
1208     complete_pdu(s, vs->pdu, err);
1209     qemu_free(vs);
1210
1211 }
1212
1213 static void v9fs_open_post_open(V9fsState *s, V9fsOpenState *vs, int err)
1214 {
1215     if (vs->fidp->fd == -1) {
1216         err = -errno;
1217         goto out;
1218     }
1219
1220     vs->offset += pdu_marshal(vs->pdu, vs->offset, "Qd", &vs->qid, 0);
1221     err = vs->offset;
1222 out:
1223     complete_pdu(s, vs->pdu, err);
1224     qemu_free(vs);
1225 }
1226
1227 static void v9fs_open_post_lstat(V9fsState *s, V9fsOpenState *vs, int err)
1228 {
1229     if (err) {
1230         err = -errno;
1231         goto out;
1232     }
1233
1234     stat_to_qid(&vs->stbuf, &vs->qid);
1235
1236     if (S_ISDIR(vs->stbuf.st_mode)) {
1237         vs->fidp->dir = v9fs_do_opendir(s, &vs->fidp->path);
1238         v9fs_open_post_opendir(s, vs, err);
1239     } else {
1240         vs->fidp->fd = v9fs_do_open(s, &vs->fidp->path,
1241                                     omode_to_uflags(vs->mode));
1242         v9fs_open_post_open(s, vs, err);
1243     }
1244     return;
1245 out:
1246     complete_pdu(s, vs->pdu, err);
1247     qemu_free(vs);
1248 }
1249
1250 static void v9fs_open(V9fsState *s, V9fsPDU *pdu)
1251 {
1252     int32_t fid;
1253     V9fsOpenState *vs;
1254     ssize_t err = 0;
1255
1256
1257     vs = qemu_malloc(sizeof(*vs));
1258     vs->pdu = pdu;
1259     vs->offset = 7;
1260
1261     pdu_unmarshal(vs->pdu, vs->offset, "db", &fid, &vs->mode);
1262
1263     vs->fidp = lookup_fid(s, fid);
1264     if (vs->fidp == NULL) {
1265         err = -ENOENT;
1266         goto out;
1267     }
1268
1269     BUG_ON(vs->fidp->fd != -1);
1270     BUG_ON(vs->fidp->dir);
1271
1272     err = v9fs_do_lstat(s, &vs->fidp->path, &vs->stbuf);
1273
1274     v9fs_open_post_lstat(s, vs, err);
1275     return;
1276 out:
1277     complete_pdu(s, pdu, err);
1278     qemu_free(vs);
1279 }
1280
1281 static void v9fs_clunk(V9fsState *s, V9fsPDU *pdu)
1282 {
1283     if (debug_9p_pdu) {
1284         pprint_pdu(pdu);
1285     }
1286 }
1287
1288 static void v9fs_read(V9fsState *s, V9fsPDU *pdu)
1289 {
1290     if (debug_9p_pdu) {
1291         pprint_pdu(pdu);
1292     }
1293 }
1294
1295 static void v9fs_write(V9fsState *s, V9fsPDU *pdu)
1296 {
1297     if (debug_9p_pdu) {
1298         pprint_pdu(pdu);
1299     }
1300 }
1301
1302 static void v9fs_create(V9fsState *s, V9fsPDU *pdu)
1303 {
1304     if (debug_9p_pdu) {
1305         pprint_pdu(pdu);
1306     }
1307 }
1308
1309 static void v9fs_flush(V9fsState *s, V9fsPDU *pdu)
1310 {
1311     v9fs_dummy(s, pdu);
1312     if (debug_9p_pdu) {
1313         pprint_pdu(pdu);
1314     }
1315 }
1316
1317 static void v9fs_remove(V9fsState *s, V9fsPDU *pdu)
1318 {
1319     if (debug_9p_pdu) {
1320         pprint_pdu(pdu);
1321     }
1322 }
1323
1324 static void v9fs_wstat(V9fsState *s, V9fsPDU *pdu)
1325 {
1326     if (debug_9p_pdu) {
1327         pprint_pdu(pdu);
1328     }
1329 }
1330
1331 typedef void (pdu_handler_t)(V9fsState *s, V9fsPDU *pdu);
1332
1333 static pdu_handler_t *pdu_handlers[] = {
1334     [P9_TVERSION] = v9fs_version,
1335     [P9_TATTACH] = v9fs_attach,
1336     [P9_TSTAT] = v9fs_stat,
1337     [P9_TWALK] = v9fs_walk,
1338     [P9_TCLUNK] = v9fs_clunk,
1339     [P9_TOPEN] = v9fs_open,
1340     [P9_TREAD] = v9fs_read,
1341 #if 0
1342     [P9_TAUTH] = v9fs_auth,
1343 #endif
1344     [P9_TFLUSH] = v9fs_flush,
1345     [P9_TCREATE] = v9fs_create,
1346     [P9_TWRITE] = v9fs_write,
1347     [P9_TWSTAT] = v9fs_wstat,
1348     [P9_TREMOVE] = v9fs_remove,
1349 };
1350
1351 static void submit_pdu(V9fsState *s, V9fsPDU *pdu)
1352 {
1353     pdu_handler_t *handler;
1354
1355     if (debug_9p_pdu) {
1356         pprint_pdu(pdu);
1357     }
1358
1359     BUG_ON(pdu->id >= ARRAY_SIZE(pdu_handlers));
1360
1361     handler = pdu_handlers[pdu->id];
1362     BUG_ON(handler == NULL);
1363
1364     handler(s, pdu);
1365 }
1366
1367 static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
1368 {
1369     V9fsState *s = (V9fsState *)vdev;
1370     V9fsPDU *pdu;
1371     ssize_t len;
1372
1373     while ((pdu = alloc_pdu(s)) &&
1374             (len = virtqueue_pop(vq, &pdu->elem)) != 0) {
1375         uint8_t *ptr;
1376
1377         BUG_ON(pdu->elem.out_num == 0 || pdu->elem.in_num == 0);
1378         BUG_ON(pdu->elem.out_sg[0].iov_len < 7);
1379
1380         ptr = pdu->elem.out_sg[0].iov_base;
1381
1382         memcpy(&pdu->size, ptr, 4);
1383         pdu->id = ptr[4];
1384         memcpy(&pdu->tag, ptr + 5, 2);
1385
1386         submit_pdu(s, pdu);
1387     }
1388
1389     free_pdu(s, pdu);
1390 }
1391
1392 static uint32_t virtio_9p_get_features(VirtIODevice *vdev, uint32_t features)
1393 {
1394     features |= 1 << VIRTIO_9P_MOUNT_TAG;
1395     return features;
1396 }
1397
1398 static V9fsState *to_virtio_9p(VirtIODevice *vdev)
1399 {
1400     return (V9fsState *)vdev;
1401 }
1402
1403 static void virtio_9p_get_config(VirtIODevice *vdev, uint8_t *config)
1404 {
1405     struct virtio_9p_config *cfg;
1406     V9fsState *s = to_virtio_9p(vdev);
1407
1408     cfg = qemu_mallocz(sizeof(struct virtio_9p_config) +
1409                         s->tag_len);
1410     stw_raw(&cfg->tag_len, s->tag_len);
1411     memcpy(cfg->tag, s->tag, s->tag_len);
1412     memcpy(config, cfg, s->config_size);
1413     qemu_free(cfg);
1414 }
1415
1416 VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
1417  {
1418     V9fsState *s;
1419     int i, len;
1420     struct stat stat;
1421     FsTypeEntry *fse;
1422
1423
1424     s = (V9fsState *)virtio_common_init("virtio-9p",
1425                                     VIRTIO_ID_9P,
1426                                     sizeof(struct virtio_9p_config)+
1427                                     MAX_TAG_LEN,
1428                                     sizeof(V9fsState));
1429
1430     /* initialize pdu allocator */
1431     QLIST_INIT(&s->free_list);
1432     for (i = 0; i < (MAX_REQ - 1); i++) {
1433         QLIST_INSERT_HEAD(&s->free_list, &s->pdus[i], next);
1434     }
1435
1436     s->vq = virtio_add_queue(&s->vdev, MAX_REQ, handle_9p_output);
1437
1438     fse = get_fsdev_fsentry(conf->fsdev_id);
1439
1440     if (!fse) {
1441         /* We don't have a fsdev identified by fsdev_id */
1442         fprintf(stderr, "Virtio-9p device couldn't find fsdev "
1443                     "with the id %s\n", conf->fsdev_id);
1444         exit(1);
1445     }
1446
1447     if (!fse->path || !conf->tag) {
1448         /* we haven't specified a mount_tag or the path */
1449         fprintf(stderr, "fsdev with id %s needs path "
1450                 "and Virtio-9p device needs mount_tag arguments\n",
1451                 conf->fsdev_id);
1452         exit(1);
1453     }
1454
1455     if (lstat(fse->path, &stat)) {
1456         fprintf(stderr, "share path %s does not exist\n", fse->path);
1457         exit(1);
1458     } else if (!S_ISDIR(stat.st_mode)) {
1459         fprintf(stderr, "share path %s is not a directory \n", fse->path);
1460         exit(1);
1461     }
1462
1463     s->ctx.fs_root = qemu_strdup(fse->path);
1464     len = strlen(conf->tag);
1465     if (len > MAX_TAG_LEN) {
1466         len = MAX_TAG_LEN;
1467     }
1468     /* s->tag is non-NULL terminated string */
1469     s->tag = qemu_malloc(len);
1470     memcpy(s->tag, conf->tag, len);
1471     s->tag_len = len;
1472     s->ctx.uid = -1;
1473
1474     s->ops = fse->ops;
1475     s->vdev.get_features = virtio_9p_get_features;
1476     s->config_size = sizeof(struct virtio_9p_config) +
1477                         s->tag_len;
1478     s->vdev.get_config = virtio_9p_get_config;
1479
1480     return &s->vdev;
1481 }