util/iov.c

   1 /*
   2  * Helpers for getting linearized buffers from iov / filling buffers into iovs
   3  *
   4  * Copyright IBM, Corp. 2007, 2008
   5  * Copyright (C) 2010 Red Hat, Inc.
   6  *
   7  * Author(s):
   8  *  Anthony Liguori <aliguori@us.ibm.com>
   9  *  Amit Shah <amit.shah@redhat.com>
  10  *  Michael Tokarev <mjt@tls.msk.ru>
  11  *
  12  * This work is licensed under the terms of the GNU GPL, version 2.  See
  13  * the COPYING file in the top-level directory.
  14  *
  15  * Contributions after 2012-01-13 are licensed under the terms of the
  16  * GNU GPL, version 2 or (at your option) any later version.
  17  */
  18
  19 #include "qemu/osdep.h"
  20 #include "qemu/iov.h"
  21 #include "qemu/sockets.h"
  22
  23 size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
  24                     size_t offset, const void *buf, size_t bytes)
  25 {
  26     size_t done;
  27     unsigned int i;
  28     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  29         if (offset < iov[i].iov_len) {
  30             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  31             memcpy(iov[i].iov_base + offset, buf + done, len);
  32             done += len;
  33             offset = 0;
  34         } else {
  35             offset -= iov[i].iov_len;
  36         }
  37     }
  38     assert(offset == 0);
  39     return done;
  40 }
  41
  42 size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
  43                   size_t offset, void *buf, size_t bytes)
  44 {
  45     size_t done;
  46     unsigned int i;
  47     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  48         if (offset < iov[i].iov_len) {
  49             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  50             memcpy(buf + done, iov[i].iov_base + offset, len);
  51             done += len;
  52             offset = 0;
  53         } else {
  54             offset -= iov[i].iov_len;
  55         }
  56     }
  57     assert(offset == 0);
  58     return done;
  59 }
  60
  61 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
  62                   size_t offset, int fillc, size_t bytes)
  63 {
  64     size_t done;
  65     unsigned int i;
  66     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  67         if (offset < iov[i].iov_len) {
  68             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  69             memset(iov[i].iov_base + offset, fillc, len);
  70             done += len;
  71             offset = 0;
  72         } else {
  73             offset -= iov[i].iov_len;
  74         }
  75     }
  76     assert(offset == 0);
  77     return done;
  78 }
  79
  80 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
  81 {
  82     size_t len;
  83     unsigned int i;
  84
  85     len = 0;
  86     for (i = 0; i < iov_cnt; i++) {
  87         len += iov[i].iov_len;
  88     }
  89     return len;
  90 }
  91
  92 /* helper function for iov_send_recv() */
  93 static ssize_t
  94 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
  95 {
  96 #ifdef CONFIG_POSIX
  97     ssize_t ret;
  98     struct msghdr msg;
  99     memset(&msg, 0, sizeof(msg));
 100     msg.msg_iov = iov;
 101     msg.msg_iovlen = iov_cnt;
 102     do {
 103         ret = do_send
 104             ? sendmsg(sockfd, &msg, 0)
 105             : recvmsg(sockfd, &msg, 0);
 106     } while (ret < 0 && errno == EINTR);
 107     return ret;
 108 #else
 109     /* else send piece-by-piece */
 110     /*XXX Note: windows has WSASend() and WSARecv() */
 111     unsigned i = 0;
 112     ssize_t ret = 0;
 113     while (i < iov_cnt) {
 114         ssize_t r = do_send
 115             ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
 116             : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
 117         if (r > 0) {
 118             ret += r;
 119         } else if (!r) {
 120             break;
 121         } else if (errno == EINTR) {
 122             continue;
 123         } else {
 124             /* else it is some "other" error,
 125              * only return if there was no data processed. */
 126             if (ret == 0) {
 127                 ret = -1;
 128             }
 129             break;
 130         }
 131         i++;
 132     }
 133     return ret;
 134 #endif
 135 }
 136
 137 ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
 138                       size_t offset, size_t bytes,
 139                       bool do_send)
 140 {
 141     ssize_t total = 0;
 142     ssize_t ret;
 143     size_t orig_len, tail;
 144     unsigned niov;
 145     struct iovec *local_iov, *iov;
 146
 147     if (bytes <= 0) {
 148         return 0;
 149     }
 150
 151     local_iov = g_new0(struct iovec, iov_cnt);
 152     iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
 153     offset = 0;
 154     iov = local_iov;
 155
 156     while (bytes > 0) {
 157         /* Find the start position, skipping `offset' bytes:
 158          * first, skip all full-sized vector elements, */
 159         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
 160             offset -= iov[niov].iov_len;
 161         }
 162
 163         /* niov == iov_cnt would only be valid if bytes == 0, which
 164          * we already ruled out in the loop condition.  */
 165         assert(niov < iov_cnt);
 166         iov += niov;
 167         iov_cnt -= niov;
 168
 169         if (offset) {
 170             /* second, skip `offset' bytes from the (now) first element,
 171              * undo it on exit */
 172             iov[0].iov_base += offset;
 173             iov[0].iov_len -= offset;
 174         }
 175         /* Find the end position skipping `bytes' bytes: */
 176         /* first, skip all full-sized elements */
 177         tail = bytes;
 178         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
 179             tail -= iov[niov].iov_len;
 180         }
 181         if (tail) {
 182             /* second, fixup the last element, and remember the original
 183              * length */
 184             assert(niov < iov_cnt);
 185             assert(iov[niov].iov_len > tail);
 186             orig_len = iov[niov].iov_len;
 187             iov[niov++].iov_len = tail;
 188             ret = do_send_recv(sockfd, iov, niov, do_send);
 189             /* Undo the changes above before checking for errors */
 190             iov[niov-1].iov_len = orig_len;
 191         } else {
 192             ret = do_send_recv(sockfd, iov, niov, do_send);
 193         }
 194         if (offset) {
 195             iov[0].iov_base -= offset;
 196             iov[0].iov_len += offset;
 197         }
 198
 199         if (ret < 0) {
 200             assert(errno != EINTR);
 201             g_free(local_iov);
 202             if (errno == EAGAIN && total > 0) {
 203                 return total;
 204             }
 205             return -1;
 206         }
 207
 208         if (ret == 0 && !do_send) {
 209             /* recv returns 0 when the peer has performed an orderly
 210              * shutdown. */
 211             break;
 212         }
 213
 214         /* Prepare for the next iteration */
 215         offset += ret;
 216         total += ret;
 217         bytes -= ret;
 218     }
 219
 220     g_free(local_iov);
 221     return total;
 222 }
 223
 224
 225 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 226                  FILE *fp, const char *prefix, size_t limit)
 227 {
 228     int v;
 229     size_t size = 0;
 230     char *buf;
 231
 232     for (v = 0; v < iov_cnt; v++) {
 233         size += iov[v].iov_len;
 234     }
 235     size = size > limit ? limit : size;
 236     buf = g_malloc(size);
 237     iov_to_buf(iov, iov_cnt, 0, buf, size);
 238     qemu_hexdump(buf, fp, prefix, size);
 239     g_free(buf);
 240 }
 241
 242 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 243                  const struct iovec *iov, unsigned int iov_cnt,
 244                  size_t offset, size_t bytes)
 245 {
 246     size_t len;
 247     unsigned int i, j;
 248     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 249         if (offset >= iov[i].iov_len) {
 250             offset -= iov[i].iov_len;
 251             continue;
 252         }
 253         len = MIN(bytes, iov[i].iov_len - offset);
 254
 255         dst_iov[j].iov_base = iov[i].iov_base + offset;
 256         dst_iov[j].iov_len = len;
 257         j++;
 258         bytes -= len;
 259         offset = 0;
 260     }
 261     assert(offset == 0);
 262     return j;
 263 }
 264
 265 /* io vectors */
 266
 267 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 268 {
 269     qiov->iov = g_new(struct iovec, alloc_hint);
 270     qiov->niov = 0;
 271     qiov->nalloc = alloc_hint;
 272     qiov->size = 0;
 273 }
 274
 275 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 276 {
 277     int i;
 278
 279     qiov->iov = iov;
 280     qiov->niov = niov;
 281     qiov->nalloc = -1;
 282     qiov->size = 0;
 283     for (i = 0; i < niov; i++)
 284         qiov->size += iov[i].iov_len;
 285 }
 286
 287 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 288 {
 289     assert(qiov->nalloc != -1);
 290
 291     if (qiov->niov == qiov->nalloc) {
 292         qiov->nalloc = 2 * qiov->nalloc + 1;
 293         qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
 294     }
 295     qiov->iov[qiov->niov].iov_base = base;
 296     qiov->iov[qiov->niov].iov_len = len;
 297     qiov->size += len;
 298     ++qiov->niov;
 299 }
 300
 301 /*
 302  * Concatenates (partial) iovecs from src_iov to the end of dst.
 303  * It starts copying after skipping `soffset' bytes at the
 304  * beginning of src and adds individual vectors from src to
 305  * dst copies up to `sbytes' bytes total, or up to the end
 306  * of src_iov if it comes first.  This way, it is okay to specify
 307  * very large value for `sbytes' to indicate "up to the end
 308  * of src".
 309  * Only vector pointers are processed, not the actual data buffers.
 310  */
 311 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
 312                              struct iovec *src_iov, unsigned int src_cnt,
 313                              size_t soffset, size_t sbytes)
 314 {
 315     int i;
 316     size_t done;
 317
 318     if (!sbytes) {
 319         return 0;
 320     }
 321     assert(dst->nalloc != -1);
 322     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 323         if (soffset < src_iov[i].iov_len) {
 324             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 325             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 326             done += len;
 327             soffset = 0;
 328         } else {
 329             soffset -= src_iov[i].iov_len;
 330         }
 331     }
 332     assert(soffset == 0); /* offset beyond end of src */
 333
 334     return done;
 335 }
 336
 337 /*
 338  * Concatenates (partial) iovecs from src to the end of dst.
 339  * It starts copying after skipping `soffset' bytes at the
 340  * beginning of src and adds individual vectors from src to
 341  * dst copies up to `sbytes' bytes total, or up to the end
 342  * of src if it comes first.  This way, it is okay to specify
 343  * very large value for `sbytes' to indicate "up to the end
 344  * of src".
 345  * Only vector pointers are processed, not the actual data buffers.
 346  */
 347 void qemu_iovec_concat(QEMUIOVector *dst,
 348                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 349 {
 350     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 351 }
 352
 353 /*
 354  * Check if the contents of the iovecs are all zero
 355  */
 356 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
 357 {
 358     int i;
 359     for (i = 0; i < qiov->niov; i++) {
 360         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
 361         uint8_t *ptr = qiov->iov[i].iov_base;
 362         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
 363             return false;
 364         }
 365         for (; offs < qiov->iov[i].iov_len; offs++) {
 366             if (ptr[offs]) {
 367                 return false;
 368             }
 369         }
 370     }
 371     return true;
 372 }
 373
 374 void qemu_iovec_destroy(QEMUIOVector *qiov)
 375 {
 376     assert(qiov->nalloc != -1);
 377
 378     qemu_iovec_reset(qiov);
 379     g_free(qiov->iov);
 380     qiov->nalloc = 0;
 381     qiov->iov = NULL;
 382 }
 383
 384 void qemu_iovec_reset(QEMUIOVector *qiov)
 385 {
 386     assert(qiov->nalloc != -1);
 387
 388     qiov->niov = 0;
 389     qiov->size = 0;
 390 }
 391
 392 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 393                          void *buf, size_t bytes)
 394 {
 395     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 396 }
 397
 398 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 399                            const void *buf, size_t bytes)
 400 {
 401     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 402 }
 403
 404 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 405                          int fillc, size_t bytes)
 406 {
 407     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 408 }
 409
 410 /**
 411  * Check that I/O vector contents are identical
 412  *
 413  * The IO vectors must have the same structure (same length of all parts).
 414  * A typical usage is to compare vectors created with qemu_iovec_clone().
 415  *
 416  * @a:          I/O vector
 417  * @b:          I/O vector
 418  * @ret:        Offset to first mismatching byte or -1 if match
 419  */
 420 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 421 {
 422     int i;
 423     ssize_t offset = 0;
 424
 425     assert(a->niov == b->niov);
 426     for (i = 0; i < a->niov; i++) {
 427         size_t len = 0;
 428         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
 429         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 430
 431         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 432         while (len < a->iov[i].iov_len && *p++ == *q++) {
 433             len++;
 434         }
 435
 436         offset += len;
 437
 438         if (len != a->iov[i].iov_len) {
 439             return offset;
 440         }
 441     }
 442     return -1;
 443 }
 444
 445 typedef struct {
 446     int src_index;
 447     struct iovec *src_iov;
 448     void *dest_base;
 449 } IOVectorSortElem;
 450
 451 static int sortelem_cmp_src_base(const void *a, const void *b)
 452 {
 453     const IOVectorSortElem *elem_a = a;
 454     const IOVectorSortElem *elem_b = b;
 455
 456     /* Don't overflow */
 457     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
 458         return -1;
 459     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
 460         return 1;
 461     } else {
 462         return 0;
 463     }
 464 }
 465
 466 static int sortelem_cmp_src_index(const void *a, const void *b)
 467 {
 468     const IOVectorSortElem *elem_a = a;
 469     const IOVectorSortElem *elem_b = b;
 470
 471     return elem_a->src_index - elem_b->src_index;
 472 }
 473
 474 /**
 475  * Copy contents of I/O vector
 476  *
 477  * The relative relationships of overlapping iovecs are preserved.  This is
 478  * necessary to ensure identical semantics in the cloned I/O vector.
 479  */
 480 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 481 {
 482     IOVectorSortElem sortelems[src->niov];
 483     void *last_end;
 484     int i;
 485
 486     /* Sort by source iovecs by base address */
 487     for (i = 0; i < src->niov; i++) {
 488         sortelems[i].src_index = i;
 489         sortelems[i].src_iov = &src->iov[i];
 490     }
 491     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 492
 493     /* Allocate buffer space taking into account overlapping iovecs */
 494     last_end = NULL;
 495     for (i = 0; i < src->niov; i++) {
 496         struct iovec *cur = sortelems[i].src_iov;
 497         ptrdiff_t rewind = 0;
 498
 499         /* Detect overlap */
 500         if (last_end && last_end > cur->iov_base) {
 501             rewind = last_end - cur->iov_base;
 502         }
 503
 504         sortelems[i].dest_base = buf - rewind;
 505         buf += cur->iov_len - MIN(rewind, cur->iov_len);
 506         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
 507     }
 508
 509     /* Sort by source iovec index and build destination iovec */
 510     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
 511     for (i = 0; i < src->niov; i++) {
 512         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
 513     }
 514 }
 515
 516 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 517                          size_t bytes)
 518 {
 519     size_t total = 0;
 520     struct iovec *cur;
 521
 522     for (cur = *iov; *iov_cnt > 0; cur++) {
 523         if (cur->iov_len > bytes) {
 524             cur->iov_base += bytes;
 525             cur->iov_len -= bytes;
 526             total += bytes;
 527             break;
 528         }
 529
 530         bytes -= cur->iov_len;
 531         total += cur->iov_len;
 532         *iov_cnt -= 1;
 533     }
 534
 535     *iov = cur;
 536     return total;
 537 }
 538
 539 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 540                         size_t bytes)
 541 {
 542     size_t total = 0;
 543     struct iovec *cur;
 544
 545     if (*iov_cnt == 0) {
 546         return 0;
 547     }
 548
 549     cur = iov + (*iov_cnt - 1);
 550
 551     while (*iov_cnt > 0) {
 552         if (cur->iov_len > bytes) {
 553             cur->iov_len -= bytes;
 554             total += bytes;
 555             break;
 556         }
 557
 558         bytes -= cur->iov_len;
 559         total += cur->iov_len;
 560         cur--;
 561         *iov_cnt -= 1;
 562     }
 563
 564     return total;
 565 }
 566
 567 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
 568 {
 569     size_t total;
 570     unsigned int niov = qiov->niov;
 571
 572     assert(qiov->size >= bytes);
 573     total = iov_discard_back(qiov->iov, &niov, bytes);
 574     assert(total == bytes);
 575
 576     qiov->niov = niov;
 577     qiov->size -= bytes;
 578 }