net/sunrpc/xdr.c

   1 /*
   2  * linux/net/sunrpc/xdr.c
   3  *
   4  * Generic XDR support.
   5  *
   6  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/types.h>
  11 #include <linux/string.h>
  12 #include <linux/kernel.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/errno.h>
  15 #include <linux/sunrpc/xdr.h>
  16 #include <linux/sunrpc/msg_prot.h>
  17
  18 /*
  19  * XDR functions for basic NFS types
  20  */
  21 u32 *
  22 xdr_encode_netobj(u32 *p, const struct xdr_netobj *obj)
  23 {
  24         unsigned int    quadlen = XDR_QUADLEN(obj->len);
  25
  26         p[quadlen] = 0;         /* zero trailing bytes */
  27         *p++ = htonl(obj->len);
  28         memcpy(p, obj->data, obj->len);
  29         return p + XDR_QUADLEN(obj->len);
  30 }
  31
  32 u32 *
  33 xdr_decode_netobj(u32 *p, struct xdr_netobj *obj)
  34 {
  35         unsigned int    len;
  36
  37         if ((len = ntohl(*p++)) > XDR_MAX_NETOBJ)
  38                 return NULL;
  39         obj->len  = len;
  40         obj->data = (u8 *) p;
  41         return p + XDR_QUADLEN(len);
  42 }
  43
  44 /**
  45  * xdr_encode_opaque_fixed - Encode fixed length opaque data
  46  * @p: pointer to current position in XDR buffer.
  47  * @ptr: pointer to data to encode (or NULL)
  48  * @nbytes: size of data.
  49  *
  50  * Copy the array of data of length nbytes at ptr to the XDR buffer
  51  * at position p, then align to the next 32-bit boundary by padding
  52  * with zero bytes (see RFC1832).
  53  * Note: if ptr is NULL, only the padding is performed.
  54  *
  55  * Returns the updated current XDR buffer position
  56  *
  57  */
  58 u32 *xdr_encode_opaque_fixed(u32 *p, const void *ptr, unsigned int nbytes)
  59 {
  60         if (likely(nbytes != 0)) {
  61                 unsigned int quadlen = XDR_QUADLEN(nbytes);
  62                 unsigned int padding = (quadlen << 2) - nbytes;
  63
  64                 if (ptr != NULL)
  65                         memcpy(p, ptr, nbytes);
  66                 if (padding != 0)
  67                         memset((char *)p + nbytes, 0, padding);
  68                 p += quadlen;
  69         }
  70         return p;
  71 }
  72 EXPORT_SYMBOL(xdr_encode_opaque_fixed);
  73
  74 /**
  75  * xdr_encode_opaque - Encode variable length opaque data
  76  * @p: pointer to current position in XDR buffer.
  77  * @ptr: pointer to data to encode (or NULL)
  78  * @nbytes: size of data.
  79  *
  80  * Returns the updated current XDR buffer position
  81  */
  82 u32 *xdr_encode_opaque(u32 *p, const void *ptr, unsigned int nbytes)
  83 {
  84         *p++ = htonl(nbytes);
  85         return xdr_encode_opaque_fixed(p, ptr, nbytes);
  86 }
  87 EXPORT_SYMBOL(xdr_encode_opaque);
  88
  89 u32 *
  90 xdr_encode_string(u32 *p, const char *string)
  91 {
  92         return xdr_encode_array(p, string, strlen(string));
  93 }
  94
  95 u32 *
  96 xdr_decode_string_inplace(u32 *p, char **sp, int *lenp, int maxlen)
  97 {
  98         unsigned int    len;
  99
 100         if ((len = ntohl(*p++)) > maxlen)
 101                 return NULL;
 102         *lenp = len;
 103         *sp = (char *) p;
 104         return p + XDR_QUADLEN(len);
 105 }
 106
 107 void
 108 xdr_encode_pages(struct xdr_buf *xdr, struct page **pages, unsigned int base,
 109                  unsigned int len)
 110 {
 111         struct kvec *tail = xdr->tail;
 112         u32 *p;
 113
 114         xdr->pages = pages;
 115         xdr->page_base = base;
 116         xdr->page_len = len;
 117
 118         p = (u32 *)xdr->head[0].iov_base + XDR_QUADLEN(xdr->head[0].iov_len);
 119         tail->iov_base = p;
 120         tail->iov_len = 0;
 121
 122         if (len & 3) {
 123                 unsigned int pad = 4 - (len & 3);
 124
 125                 *p = 0;
 126                 tail->iov_base = (char *)p + (len & 3);
 127                 tail->iov_len  = pad;
 128                 len += pad;
 129         }
 130         xdr->buflen += len;
 131         xdr->len += len;
 132 }
 133
 134 void
 135 xdr_inline_pages(struct xdr_buf *xdr, unsigned int offset,
 136                  struct page **pages, unsigned int base, unsigned int len)
 137 {
 138         struct kvec *head = xdr->head;
 139         struct kvec *tail = xdr->tail;
 140         char *buf = (char *)head->iov_base;
 141         unsigned int buflen = head->iov_len;
 142
 143         head->iov_len  = offset;
 144
 145         xdr->pages = pages;
 146         xdr->page_base = base;
 147         xdr->page_len = len;
 148
 149         tail->iov_base = buf + offset;
 150         tail->iov_len = buflen - offset;
 151
 152         xdr->buflen += len;
 153 }
 154
 155
 156 /*
 157  * Helper routines for doing 'memmove' like operations on a struct xdr_buf
 158  *
 159  * _shift_data_right_pages
 160  * @pages: vector of pages containing both the source and dest memory area.
 161  * @pgto_base: page vector address of destination
 162  * @pgfrom_base: page vector address of source
 163  * @len: number of bytes to copy
 164  *
 165  * Note: the addresses pgto_base and pgfrom_base are both calculated in
 166  *       the same way:
 167  *            if a memory area starts at byte 'base' in page 'pages[i]',
 168  *            then its address is given as (i << PAGE_CACHE_SHIFT) + base
 169  * Also note: pgfrom_base must be < pgto_base, but the memory areas
 170  *      they point to may overlap.
 171  */
 172 static void
 173 _shift_data_right_pages(struct page **pages, size_t pgto_base,
 174                 size_t pgfrom_base, size_t len)
 175 {
 176         struct page **pgfrom, **pgto;
 177         char *vfrom, *vto;
 178         size_t copy;
 179
 180         BUG_ON(pgto_base <= pgfrom_base);
 181
 182         pgto_base += len;
 183         pgfrom_base += len;
 184
 185         pgto = pages + (pgto_base >> PAGE_CACHE_SHIFT);
 186         pgfrom = pages + (pgfrom_base >> PAGE_CACHE_SHIFT);
 187
 188         pgto_base &= ~PAGE_CACHE_MASK;
 189         pgfrom_base &= ~PAGE_CACHE_MASK;
 190
 191         do {
 192                 /* Are any pointers crossing a page boundary? */
 193                 if (pgto_base == 0) {
 194                         flush_dcache_page(*pgto);
 195                         pgto_base = PAGE_CACHE_SIZE;
 196                         pgto--;
 197                 }
 198                 if (pgfrom_base == 0) {
 199                         pgfrom_base = PAGE_CACHE_SIZE;
 200                         pgfrom--;
 201                 }
 202
 203                 copy = len;
 204                 if (copy > pgto_base)
 205                         copy = pgto_base;
 206                 if (copy > pgfrom_base)
 207                         copy = pgfrom_base;
 208                 pgto_base -= copy;
 209                 pgfrom_base -= copy;
 210
 211                 vto = kmap_atomic(*pgto, KM_USER0);
 212                 vfrom = kmap_atomic(*pgfrom, KM_USER1);
 213                 memmove(vto + pgto_base, vfrom + pgfrom_base, copy);
 214                 kunmap_atomic(vfrom, KM_USER1);
 215                 kunmap_atomic(vto, KM_USER0);
 216
 217         } while ((len -= copy) != 0);
 218         flush_dcache_page(*pgto);
 219 }
 220
 221 /*
 222  * _copy_to_pages
 223  * @pages: array of pages
 224  * @pgbase: page vector address of destination
 225  * @p: pointer to source data
 226  * @len: length
 227  *
 228  * Copies data from an arbitrary memory location into an array of pages
 229  * The copy is assumed to be non-overlapping.
 230  */
 231 static void
 232 _copy_to_pages(struct page **pages, size_t pgbase, const char *p, size_t len)
 233 {
 234         struct page **pgto;
 235         char *vto;
 236         size_t copy;
 237
 238         pgto = pages + (pgbase >> PAGE_CACHE_SHIFT);
 239         pgbase &= ~PAGE_CACHE_MASK;
 240
 241         do {
 242                 copy = PAGE_CACHE_SIZE - pgbase;
 243                 if (copy > len)
 244                         copy = len;
 245
 246                 vto = kmap_atomic(*pgto, KM_USER0);
 247                 memcpy(vto + pgbase, p, copy);
 248                 kunmap_atomic(vto, KM_USER0);
 249
 250                 pgbase += copy;
 251                 if (pgbase == PAGE_CACHE_SIZE) {
 252                         flush_dcache_page(*pgto);
 253                         pgbase = 0;
 254                         pgto++;
 255                 }
 256                 p += copy;
 257
 258         } while ((len -= copy) != 0);
 259         flush_dcache_page(*pgto);
 260 }
 261
 262 /*
 263  * _copy_from_pages
 264  * @p: pointer to destination
 265  * @pages: array of pages
 266  * @pgbase: offset of source data
 267  * @len: length
 268  *
 269  * Copies data into an arbitrary memory location from an array of pages
 270  * The copy is assumed to be non-overlapping.
 271  */
 272 static void
 273 _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len)
 274 {
 275         struct page **pgfrom;
 276         char *vfrom;
 277         size_t copy;
 278
 279         pgfrom = pages + (pgbase >> PAGE_CACHE_SHIFT);
 280         pgbase &= ~PAGE_CACHE_MASK;
 281
 282         do {
 283                 copy = PAGE_CACHE_SIZE - pgbase;
 284                 if (copy > len)
 285                         copy = len;
 286
 287                 vfrom = kmap_atomic(*pgfrom, KM_USER0);
 288                 memcpy(p, vfrom + pgbase, copy);
 289                 kunmap_atomic(vfrom, KM_USER0);
 290
 291                 pgbase += copy;
 292                 if (pgbase == PAGE_CACHE_SIZE) {
 293                         pgbase = 0;
 294                         pgfrom++;
 295                 }
 296                 p += copy;
 297
 298         } while ((len -= copy) != 0);
 299 }
 300
 301 /*
 302  * xdr_shrink_bufhead
 303  * @buf: xdr_buf
 304  * @len: bytes to remove from buf->head[0]
 305  *
 306  * Shrinks XDR buffer's header kvec buf->head[0] by
 307  * 'len' bytes. The extra data is not lost, but is instead
 308  * moved into the inlined pages and/or the tail.
 309  */
 310 static void
 311 xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
 312 {
 313         struct kvec *head, *tail;
 314         size_t copy, offs;
 315         unsigned int pglen = buf->page_len;
 316
 317         tail = buf->tail;
 318         head = buf->head;
 319         BUG_ON (len > head->iov_len);
 320
 321         /* Shift the tail first */
 322         if (tail->iov_len != 0) {
 323                 if (tail->iov_len > len) {
 324                         copy = tail->iov_len - len;
 325                         memmove((char *)tail->iov_base + len,
 326                                         tail->iov_base, copy);
 327                 }
 328                 /* Copy from the inlined pages into the tail */
 329                 copy = len;
 330                 if (copy > pglen)
 331                         copy = pglen;
 332                 offs = len - copy;
 333                 if (offs >= tail->iov_len)
 334                         copy = 0;
 335                 else if (copy > tail->iov_len - offs)
 336                         copy = tail->iov_len - offs;
 337                 if (copy != 0)
 338                         _copy_from_pages((char *)tail->iov_base + offs,
 339                                         buf->pages,
 340                                         buf->page_base + pglen + offs - len,
 341                                         copy);
 342                 /* Do we also need to copy data from the head into the tail ? */
 343                 if (len > pglen) {
 344                         offs = copy = len - pglen;
 345                         if (copy > tail->iov_len)
 346                                 copy = tail->iov_len;
 347                         memcpy(tail->iov_base,
 348                                         (char *)head->iov_base +
 349                                         head->iov_len - offs,
 350                                         copy);
 351                 }
 352         }
 353         /* Now handle pages */
 354         if (pglen != 0) {
 355                 if (pglen > len)
 356                         _shift_data_right_pages(buf->pages,
 357                                         buf->page_base + len,
 358                                         buf->page_base,
 359                                         pglen - len);
 360                 copy = len;
 361                 if (len > pglen)
 362                         copy = pglen;
 363                 _copy_to_pages(buf->pages, buf->page_base,
 364                                 (char *)head->iov_base + head->iov_len - len,
 365                                 copy);
 366         }
 367         head->iov_len -= len;
 368         buf->buflen -= len;
 369         /* Have we truncated the message? */
 370         if (buf->len > buf->buflen)
 371                 buf->len = buf->buflen;
 372 }
 373
 374 /*
 375  * xdr_shrink_pagelen
 376  * @buf: xdr_buf
 377  * @len: bytes to remove from buf->pages
 378  *
 379  * Shrinks XDR buffer's page array buf->pages by
 380  * 'len' bytes. The extra data is not lost, but is instead
 381  * moved into the tail.
 382  */
 383 static void
 384 xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
 385 {
 386         struct kvec *tail;
 387         size_t copy;
 388         char *p;
 389         unsigned int pglen = buf->page_len;
 390
 391         tail = buf->tail;
 392         BUG_ON (len > pglen);
 393
 394         /* Shift the tail first */
 395         if (tail->iov_len != 0) {
 396                 p = (char *)tail->iov_base + len;
 397                 if (tail->iov_len > len) {
 398                         copy = tail->iov_len - len;
 399                         memmove(p, tail->iov_base, copy);
 400                 } else
 401                         buf->buflen -= len;
 402                 /* Copy from the inlined pages into the tail */
 403                 copy = len;
 404                 if (copy > tail->iov_len)
 405                         copy = tail->iov_len;
 406                 _copy_from_pages((char *)tail->iov_base,
 407                                 buf->pages, buf->page_base + pglen - len,
 408                                 copy);
 409         }
 410         buf->page_len -= len;
 411         buf->buflen -= len;
 412         /* Have we truncated the message? */
 413         if (buf->len > buf->buflen)
 414                 buf->len = buf->buflen;
 415 }
 416
 417 void
 418 xdr_shift_buf(struct xdr_buf *buf, size_t len)
 419 {
 420         xdr_shrink_bufhead(buf, len);
 421 }
 422
 423 /**
 424  * xdr_init_encode - Initialize a struct xdr_stream for sending data.
 425  * @xdr: pointer to xdr_stream struct
 426  * @buf: pointer to XDR buffer in which to encode data
 427  * @p: current pointer inside XDR buffer
 428  *
 429  * Note: at the moment the RPC client only passes the length of our
 430  *       scratch buffer in the xdr_buf's header kvec. Previously this
 431  *       meant we needed to call xdr_adjust_iovec() after encoding the
 432  *       data. With the new scheme, the xdr_stream manages the details
 433  *       of the buffer length, and takes care of adjusting the kvec
 434  *       length for us.
 435  */
 436 void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, uint32_t *p)
 437 {
 438         struct kvec *iov = buf->head;
 439         int scratch_len = buf->buflen - buf->page_len - buf->tail[0].iov_len;
 440
 441         BUG_ON(scratch_len < 0);
 442         xdr->buf = buf;
 443         xdr->iov = iov;
 444         xdr->p = (uint32_t *)((char *)iov->iov_base + iov->iov_len);
 445         xdr->end = (uint32_t *)((char *)iov->iov_base + scratch_len);
 446         BUG_ON(iov->iov_len > scratch_len);
 447
 448         if (p != xdr->p && p != NULL) {
 449                 size_t len;
 450
 451                 BUG_ON(p < xdr->p || p > xdr->end);
 452                 len = (char *)p - (char *)xdr->p;
 453                 xdr->p = p;
 454                 buf->len += len;
 455                 iov->iov_len += len;
 456         }
 457 }
 458 EXPORT_SYMBOL(xdr_init_encode);
 459
 460 /**
 461  * xdr_reserve_space - Reserve buffer space for sending
 462  * @xdr: pointer to xdr_stream
 463  * @nbytes: number of bytes to reserve
 464  *
 465  * Checks that we have enough buffer space to encode 'nbytes' more
 466  * bytes of data. If so, update the total xdr_buf length, and
 467  * adjust the length of the current kvec.
 468  */
 469 uint32_t * xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes)
 470 {
 471         uint32_t *p = xdr->p;
 472         uint32_t *q;
 473
 474         /* align nbytes on the next 32-bit boundary */
 475         nbytes += 3;
 476         nbytes &= ~3;
 477         q = p + (nbytes >> 2);
 478         if (unlikely(q > xdr->end || q < p))
 479                 return NULL;
 480         xdr->p = q;
 481         xdr->iov->iov_len += nbytes;
 482         xdr->buf->len += nbytes;
 483         return p;
 484 }
 485 EXPORT_SYMBOL(xdr_reserve_space);
 486
 487 /**
 488  * xdr_write_pages - Insert a list of pages into an XDR buffer for sending
 489  * @xdr: pointer to xdr_stream
 490  * @pages: list of pages
 491  * @base: offset of first byte
 492  * @len: length of data in bytes
 493  *
 494  */
 495 void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base,
 496                  unsigned int len)
 497 {
 498         struct xdr_buf *buf = xdr->buf;
 499         struct kvec *iov = buf->tail;
 500         buf->pages = pages;
 501         buf->page_base = base;
 502         buf->page_len = len;
 503
 504         iov->iov_base = (char *)xdr->p;
 505         iov->iov_len  = 0;
 506         xdr->iov = iov;
 507
 508         if (len & 3) {
 509                 unsigned int pad = 4 - (len & 3);
 510
 511                 BUG_ON(xdr->p >= xdr->end);
 512                 iov->iov_base = (char *)xdr->p + (len & 3);
 513                 iov->iov_len  += pad;
 514                 len += pad;
 515                 *xdr->p++ = 0;
 516         }
 517         buf->buflen += len;
 518         buf->len += len;
 519 }
 520 EXPORT_SYMBOL(xdr_write_pages);
 521
 522 /**
 523  * xdr_init_decode - Initialize an xdr_stream for decoding data.
 524  * @xdr: pointer to xdr_stream struct
 525  * @buf: pointer to XDR buffer from which to decode data
 526  * @p: current pointer inside XDR buffer
 527  */
 528 void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, uint32_t *p)
 529 {
 530         struct kvec *iov = buf->head;
 531         unsigned int len = iov->iov_len;
 532
 533         if (len > buf->len)
 534                 len = buf->len;
 535         xdr->buf = buf;
 536         xdr->iov = iov;
 537         xdr->p = p;
 538         xdr->end = (uint32_t *)((char *)iov->iov_base + len);
 539 }
 540 EXPORT_SYMBOL(xdr_init_decode);
 541
 542 /**
 543  * xdr_inline_decode - Retrieve non-page XDR data to decode
 544  * @xdr: pointer to xdr_stream struct
 545  * @nbytes: number of bytes of data to decode
 546  *
 547  * Check if the input buffer is long enough to enable us to decode
 548  * 'nbytes' more bytes of data starting at the current position.
 549  * If so return the current pointer, then update the current
 550  * pointer position.
 551  */
 552 uint32_t * xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 553 {
 554         uint32_t *p = xdr->p;
 555         uint32_t *q = p + XDR_QUADLEN(nbytes);
 556
 557         if (unlikely(q > xdr->end || q < p))
 558                 return NULL;
 559         xdr->p = q;
 560         return p;
 561 }
 562 EXPORT_SYMBOL(xdr_inline_decode);
 563
 564 /**
 565  * xdr_read_pages - Ensure page-based XDR data to decode is aligned at current pointer position
 566  * @xdr: pointer to xdr_stream struct
 567  * @len: number of bytes of page data
 568  *
 569  * Moves data beyond the current pointer position from the XDR head[] buffer
 570  * into the page list. Any data that lies beyond current position + "len"
 571  * bytes is moved into the XDR tail[]. The current pointer is then
 572  * repositioned at the beginning of the XDR tail.
 573  */
 574 void xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
 575 {
 576         struct xdr_buf *buf = xdr->buf;
 577         struct kvec *iov;
 578         ssize_t shift;
 579         unsigned int end;
 580         int padding;
 581
 582         /* Realign pages to current pointer position */
 583         iov  = buf->head;
 584         shift = iov->iov_len + (char *)iov->iov_base - (char *)xdr->p;
 585         if (shift > 0)
 586                 xdr_shrink_bufhead(buf, shift);
 587
 588         /* Truncate page data and move it into the tail */
 589         if (buf->page_len > len)
 590                 xdr_shrink_pagelen(buf, buf->page_len - len);
 591         padding = (XDR_QUADLEN(len) << 2) - len;
 592         xdr->iov = iov = buf->tail;
 593         /* Compute remaining message length.  */
 594         end = iov->iov_len;
 595         shift = buf->buflen - buf->len;
 596         if (shift < end)
 597                 end -= shift;
 598         else if (shift > 0)
 599                 end = 0;
 600         /*
 601          * Position current pointer at beginning of tail, and
 602          * set remaining message length.
 603          */
 604         xdr->p = (uint32_t *)((char *)iov->iov_base + padding);
 605         xdr->end = (uint32_t *)((char *)iov->iov_base + end);
 606 }
 607 EXPORT_SYMBOL(xdr_read_pages);
 608
 609 static struct kvec empty_iov = {.iov_base = NULL, .iov_len = 0};
 610
 611 void
 612 xdr_buf_from_iov(struct kvec *iov, struct xdr_buf *buf)
 613 {
 614         buf->head[0] = *iov;
 615         buf->tail[0] = empty_iov;
 616         buf->page_len = 0;
 617         buf->buflen = buf->len = iov->iov_len;
 618 }
 619
 620 /* Sets subiov to the intersection of iov with the buffer of length len
 621  * starting base bytes after iov.  Indicates empty intersection by setting
 622  * length of subiov to zero.  Decrements len by length of subiov, sets base
 623  * to zero (or decrements it by length of iov if subiov is empty). */
 624 static void
 625 iov_subsegment(struct kvec *iov, struct kvec *subiov, int *base, int *len)
 626 {
 627         if (*base > iov->iov_len) {
 628                 subiov->iov_base = NULL;
 629                 subiov->iov_len = 0;
 630                 *base -= iov->iov_len;
 631         } else {
 632                 subiov->iov_base = iov->iov_base + *base;
 633                 subiov->iov_len = min(*len, (int)iov->iov_len - *base);
 634                 *base = 0;
 635         }
 636         *len -= subiov->iov_len;
 637 }
 638
 639 /* Sets subbuf to the portion of buf of length len beginning base bytes
 640  * from the start of buf. Returns -1 if base of length are out of bounds. */
 641 int
 642 xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 643                         int base, int len)
 644 {
 645         int i;
 646
 647         subbuf->buflen = subbuf->len = len;
 648         iov_subsegment(buf->head, subbuf->head, &base, &len);
 649
 650         if (base < buf->page_len) {
 651                 i = (base + buf->page_base) >> PAGE_CACHE_SHIFT;
 652                 subbuf->pages = &buf->pages[i];
 653                 subbuf->page_base = (base + buf->page_base) & ~PAGE_CACHE_MASK;
 654                 subbuf->page_len = min((int)buf->page_len - base, len);
 655                 len -= subbuf->page_len;
 656                 base = 0;
 657         } else {
 658                 base -= buf->page_len;
 659                 subbuf->page_len = 0;
 660         }
 661
 662         iov_subsegment(buf->tail, subbuf->tail, &base, &len);
 663         if (base || len)
 664                 return -1;
 665         return 0;
 666 }
 667
 668 /* obj is assumed to point to allocated memory of size at least len: */
 669 int
 670 read_bytes_from_xdr_buf(struct xdr_buf *buf, int base, void *obj, int len)
 671 {
 672         struct xdr_buf subbuf;
 673         int this_len;
 674         int status;
 675
 676         status = xdr_buf_subsegment(buf, &subbuf, base, len);
 677         if (status)
 678                 goto out;
 679         this_len = min(len, (int)subbuf.head[0].iov_len);
 680         memcpy(obj, subbuf.head[0].iov_base, this_len);
 681         len -= this_len;
 682         obj += this_len;
 683         this_len = min(len, (int)subbuf.page_len);
 684         if (this_len)
 685                 _copy_from_pages(obj, subbuf.pages, subbuf.page_base, this_len);
 686         len -= this_len;
 687         obj += this_len;
 688         this_len = min(len, (int)subbuf.tail[0].iov_len);
 689         memcpy(obj, subbuf.tail[0].iov_base, this_len);
 690 out:
 691         return status;
 692 }
 693
 694 /* obj is assumed to point to allocated memory of size at least len: */
 695 int
 696 write_bytes_to_xdr_buf(struct xdr_buf *buf, int base, void *obj, int len)
 697 {
 698         struct xdr_buf subbuf;
 699         int this_len;
 700         int status;
 701
 702         status = xdr_buf_subsegment(buf, &subbuf, base, len);
 703         if (status)
 704                 goto out;
 705         this_len = min(len, (int)subbuf.head[0].iov_len);
 706         memcpy(subbuf.head[0].iov_base, obj, this_len);
 707         len -= this_len;
 708         obj += this_len;
 709         this_len = min(len, (int)subbuf.page_len);
 710         if (this_len)
 711                 _copy_to_pages(subbuf.pages, subbuf.page_base, obj, this_len);
 712         len -= this_len;
 713         obj += this_len;
 714         this_len = min(len, (int)subbuf.tail[0].iov_len);
 715         memcpy(subbuf.tail[0].iov_base, obj, this_len);
 716 out:
 717         return status;
 718 }
 719
 720 int
 721 xdr_decode_word(struct xdr_buf *buf, int base, u32 *obj)
 722 {
 723         u32     raw;
 724         int     status;
 725
 726         status = read_bytes_from_xdr_buf(buf, base, &raw, sizeof(*obj));
 727         if (status)
 728                 return status;
 729         *obj = ntohl(raw);
 730         return 0;
 731 }
 732
 733 int
 734 xdr_encode_word(struct xdr_buf *buf, int base, u32 obj)
 735 {
 736         u32     raw = htonl(obj);
 737
 738         return write_bytes_to_xdr_buf(buf, base, &raw, sizeof(obj));
 739 }
 740
 741 /* If the netobj starting offset bytes from the start of xdr_buf is contained
 742  * entirely in the head or the tail, set object to point to it; otherwise
 743  * try to find space for it at the end of the tail, copy it there, and
 744  * set obj to point to it. */
 745 int
 746 xdr_buf_read_netobj(struct xdr_buf *buf, struct xdr_netobj *obj, int offset)
 747 {
 748         u32     tail_offset = buf->head[0].iov_len + buf->page_len;
 749         u32     obj_end_offset;
 750
 751         if (xdr_decode_word(buf, offset, &obj->len))
 752                 goto out;
 753         obj_end_offset = offset + 4 + obj->len;
 754
 755         if (obj_end_offset <= buf->head[0].iov_len) {
 756                 /* The obj is contained entirely in the head: */
 757                 obj->data = buf->head[0].iov_base + offset + 4;
 758         } else if (offset + 4 >= tail_offset) {
 759                 if (obj_end_offset - tail_offset
 760                                 > buf->tail[0].iov_len)
 761                         goto out;
 762                 /* The obj is contained entirely in the tail: */
 763                 obj->data = buf->tail[0].iov_base
 764                         + offset - tail_offset + 4;
 765         } else {
 766                 /* use end of tail as storage for obj:
 767                  * (We don't copy to the beginning because then we'd have
 768                  * to worry about doing a potentially overlapping copy.
 769                  * This assumes the object is at most half the length of the
 770                  * tail.) */
 771                 if (obj->len > buf->tail[0].iov_len)
 772                         goto out;
 773                 obj->data = buf->tail[0].iov_base + buf->tail[0].iov_len -
 774                                 obj->len;
 775                 if (read_bytes_from_xdr_buf(buf, offset + 4,
 776                                         obj->data, obj->len))
 777                         goto out;
 778
 779         }
 780         return 0;
 781 out:
 782         return -1;
 783 }
 784
 785 /* Returns 0 on success, or else a negative error code. */
 786 static int
 787 xdr_xcode_array2(struct xdr_buf *buf, unsigned int base,
 788                  struct xdr_array2_desc *desc, int encode)
 789 {
 790         char *elem = NULL, *c;
 791         unsigned int copied = 0, todo, avail_here;
 792         struct page **ppages = NULL;
 793         int err;
 794
 795         if (encode) {
 796                 if (xdr_encode_word(buf, base, desc->array_len) != 0)
 797                         return -EINVAL;
 798         } else {
 799                 if (xdr_decode_word(buf, base, &desc->array_len) != 0 ||
 800                     desc->array_len > desc->array_maxlen ||
 801                     (unsigned long) base + 4 + desc->array_len *
 802                                     desc->elem_size > buf->len)
 803                         return -EINVAL;
 804         }
 805         base += 4;
 806
 807         if (!desc->xcode)
 808                 return 0;
 809
 810         todo = desc->array_len * desc->elem_size;
 811
 812         /* process head */
 813         if (todo && base < buf->head->iov_len) {
 814                 c = buf->head->iov_base + base;
 815                 avail_here = min_t(unsigned int, todo,
 816                                    buf->head->iov_len - base);
 817                 todo -= avail_here;
 818
 819                 while (avail_here >= desc->elem_size) {
 820                         err = desc->xcode(desc, c);
 821                         if (err)
 822                                 goto out;
 823                         c += desc->elem_size;
 824                         avail_here -= desc->elem_size;
 825                 }
 826                 if (avail_here) {
 827                         if (!elem) {
 828                                 elem = kmalloc(desc->elem_size, GFP_KERNEL);
 829                                 err = -ENOMEM;
 830                                 if (!elem)
 831                                         goto out;
 832                         }
 833                         if (encode) {
 834                                 err = desc->xcode(desc, elem);
 835                                 if (err)
 836                                         goto out;
 837                                 memcpy(c, elem, avail_here);
 838                         } else
 839                                 memcpy(elem, c, avail_here);
 840                         copied = avail_here;
 841                 }
 842                 base = buf->head->iov_len;  /* align to start of pages */
 843         }
 844
 845         /* process pages array */
 846         base -= buf->head->iov_len;
 847         if (todo && base < buf->page_len) {
 848                 unsigned int avail_page;
 849
 850                 avail_here = min(todo, buf->page_len - base);
 851                 todo -= avail_here;
 852
 853                 base += buf->page_base;
 854                 ppages = buf->pages + (base >> PAGE_CACHE_SHIFT);
 855                 base &= ~PAGE_CACHE_MASK;
 856                 avail_page = min_t(unsigned int, PAGE_CACHE_SIZE - base,
 857                                         avail_here);
 858                 c = kmap(*ppages) + base;
 859
 860                 while (avail_here) {
 861                         avail_here -= avail_page;
 862                         if (copied || avail_page < desc->elem_size) {
 863                                 unsigned int l = min(avail_page,
 864                                         desc->elem_size - copied);
 865                                 if (!elem) {
 866                                         elem = kmalloc(desc->elem_size,
 867                                                        GFP_KERNEL);
 868                                         err = -ENOMEM;
 869                                         if (!elem)
 870                                                 goto out;
 871                                 }
 872                                 if (encode) {
 873                                         if (!copied) {
 874                                                 err = desc->xcode(desc, elem);
 875                                                 if (err)
 876                                                         goto out;
 877                                         }
 878                                         memcpy(c, elem + copied, l);
 879                                         copied += l;
 880                                         if (copied == desc->elem_size)
 881                                                 copied = 0;
 882                                 } else {
 883                                         memcpy(elem + copied, c, l);
 884                                         copied += l;
 885                                         if (copied == desc->elem_size) {
 886                                                 err = desc->xcode(desc, elem);
 887                                                 if (err)
 888                                                         goto out;
 889                                                 copied = 0;
 890                                         }
 891                                 }
 892                                 avail_page -= l;
 893                                 c += l;
 894                         }
 895                         while (avail_page >= desc->elem_size) {
 896                                 err = desc->xcode(desc, c);
 897                                 if (err)
 898                                         goto out;
 899                                 c += desc->elem_size;
 900                                 avail_page -= desc->elem_size;
 901                         }
 902                         if (avail_page) {
 903                                 unsigned int l = min(avail_page,
 904                                             desc->elem_size - copied);
 905                                 if (!elem) {
 906                                         elem = kmalloc(desc->elem_size,
 907                                                        GFP_KERNEL);
 908                                         err = -ENOMEM;
 909                                         if (!elem)
 910                                                 goto out;
 911                                 }
 912                                 if (encode) {
 913                                         if (!copied) {
 914                                                 err = desc->xcode(desc, elem);
 915                                                 if (err)
 916                                                         goto out;
 917                                         }
 918                                         memcpy(c, elem + copied, l);
 919                                         copied += l;
 920                                         if (copied == desc->elem_size)
 921                                                 copied = 0;
 922                                 } else {
 923                                         memcpy(elem + copied, c, l);
 924                                         copied += l;
 925                                         if (copied == desc->elem_size) {
 926                                                 err = desc->xcode(desc, elem);
 927                                                 if (err)
 928                                                         goto out;
 929                                                 copied = 0;
 930                                         }
 931                                 }
 932                         }
 933                         if (avail_here) {
 934                                 kunmap(*ppages);
 935                                 ppages++;
 936                                 c = kmap(*ppages);
 937                         }
 938
 939                         avail_page = min(avail_here,
 940                                  (unsigned int) PAGE_CACHE_SIZE);
 941                 }
 942                 base = buf->page_len;  /* align to start of tail */
 943         }
 944
 945         /* process tail */
 946         base -= buf->page_len;
 947         if (todo) {
 948                 c = buf->tail->iov_base + base;
 949                 if (copied) {
 950                         unsigned int l = desc->elem_size - copied;
 951
 952                         if (encode)
 953                                 memcpy(c, elem + copied, l);
 954                         else {
 955                                 memcpy(elem + copied, c, l);
 956                                 err = desc->xcode(desc, elem);
 957                                 if (err)
 958                                         goto out;
 959                         }
 960                         todo -= l;
 961                         c += l;
 962                 }
 963                 while (todo) {
 964                         err = desc->xcode(desc, c);
 965                         if (err)
 966                                 goto out;
 967                         c += desc->elem_size;
 968                         todo -= desc->elem_size;
 969                 }
 970         }
 971         err = 0;
 972
 973 out:
 974         kfree(elem);
 975         if (ppages)
 976                 kunmap(*ppages);
 977         return err;
 978 }
 979
 980 int
 981 xdr_decode_array2(struct xdr_buf *buf, unsigned int base,
 982                   struct xdr_array2_desc *desc)
 983 {
 984         if (base >= buf->len)
 985                 return -EINVAL;
 986
 987         return xdr_xcode_array2(buf, base, desc, 0);
 988 }
 989
 990 int
 991 xdr_encode_array2(struct xdr_buf *buf, unsigned int base,
 992                   struct xdr_array2_desc *desc)
 993 {
 994         if ((unsigned long) base + 4 + desc->array_len * desc->elem_size >
 995             buf->head->iov_len + buf->page_len + buf->tail->iov_len)
 996                 return -EINVAL;
 997
 998         return xdr_xcode_array2(buf, base, desc, 1);
 999 }