lib/iov_iter.c

   1 #include <linux/export.h>
   2 #include <linux/uio.h>
   3 #include <linux/pagemap.h>
   4 #include <linux/slab.h>
   5 #include <linux/vmalloc.h>
   6 #include <net/checksum.h>
   7
   8 #define iterate_iovec(i, n, __v, __p, skip, STEP) {     \
   9         size_t left;                                    \
  10         size_t wanted = n;                              \
  11         __p = i->iov;                                   \
  12         __v.iov_len = min(n, __p->iov_len - skip);      \
  13         if (likely(__v.iov_len)) {                      \
  14                 __v.iov_base = __p->iov_base + skip;    \
  15                 left = (STEP);                          \
  16                 __v.iov_len -= left;                    \
  17                 skip += __v.iov_len;                    \
  18                 n -= __v.iov_len;                       \
  19         } else {                                        \
  20                 left = 0;                               \
  21         }                                               \
  22         while (unlikely(!left && n)) {                  \
  23                 __p++;                                  \
  24                 __v.iov_len = min(n, __p->iov_len);     \
  25                 if (unlikely(!__v.iov_len))             \
  26                         continue;                       \
  27                 __v.iov_base = __p->iov_base;           \
  28                 left = (STEP);                          \
  29                 __v.iov_len -= left;                    \
  30                 skip = __v.iov_len;                     \
  31                 n -= __v.iov_len;                       \
  32         }                                               \
  33         n = wanted - n;                                 \
  34 }
  35
  36 #define iterate_kvec(i, n, __v, __p, skip, STEP) {      \
  37         size_t wanted = n;                              \
  38         __p = i->kvec;                                  \
  39         __v.iov_len = min(n, __p->iov_len - skip);      \
  40         if (likely(__v.iov_len)) {                      \
  41                 __v.iov_base = __p->iov_base + skip;    \
  42                 (void)(STEP);                           \
  43                 skip += __v.iov_len;                    \
  44                 n -= __v.iov_len;                       \
  45         }                                               \
  46         while (unlikely(n)) {                           \
  47                 __p++;                                  \
  48                 __v.iov_len = min(n, __p->iov_len);     \
  49                 if (unlikely(!__v.iov_len))             \
  50                         continue;                       \
  51                 __v.iov_base = __p->iov_base;           \
  52                 (void)(STEP);                           \
  53                 skip = __v.iov_len;                     \
  54                 n -= __v.iov_len;                       \
  55         }                                               \
  56         n = wanted;                                     \
  57 }
  58
  59 #define iterate_bvec(i, n, __v, __p, skip, STEP) {      \
  60         size_t wanted = n;                              \
  61         __p = i->bvec;                                  \
  62         __v.bv_len = min_t(size_t, n, __p->bv_len - skip);      \
  63         if (likely(__v.bv_len)) {                       \
  64                 __v.bv_page = __p->bv_page;             \
  65                 __v.bv_offset = __p->bv_offset + skip;  \
  66                 (void)(STEP);                           \
  67                 skip += __v.bv_len;                     \
  68                 n -= __v.bv_len;                        \
  69         }                                               \
  70         while (unlikely(n)) {                           \
  71                 __p++;                                  \
  72                 __v.bv_len = min_t(size_t, n, __p->bv_len);     \
  73                 if (unlikely(!__v.bv_len))              \
  74                         continue;                       \
  75                 __v.bv_page = __p->bv_page;             \
  76                 __v.bv_offset = __p->bv_offset;         \
  77                 (void)(STEP);                           \
  78                 skip = __v.bv_len;                      \
  79                 n -= __v.bv_len;                        \
  80         }                                               \
  81         n = wanted;                                     \
  82 }
  83
  84 #define iterate_all_kinds(i, n, v, I, B, K) {                   \
  85         size_t skip = i->iov_offset;                            \
  86         if (unlikely(i->type & ITER_BVEC)) {                    \
  87                 const struct bio_vec *bvec;                     \
  88                 struct bio_vec v;                               \
  89                 iterate_bvec(i, n, v, bvec, skip, (B))          \
  90         } else if (unlikely(i->type & ITER_KVEC)) {             \
  91                 const struct kvec *kvec;                        \
  92                 struct kvec v;                                  \
  93                 iterate_kvec(i, n, v, kvec, skip, (K))          \
  94         } else {                                                \
  95                 const struct iovec *iov;                        \
  96                 struct iovec v;                                 \
  97                 iterate_iovec(i, n, v, iov, skip, (I))          \
  98         }                                                       \
  99 }
 100
 101 #define iterate_and_advance(i, n, v, I, B, K) {                 \
 102         size_t skip = i->iov_offset;                            \
 103         if (unlikely(i->type & ITER_BVEC)) {                    \
 104                 const struct bio_vec *bvec;                     \
 105                 struct bio_vec v;                               \
 106                 iterate_bvec(i, n, v, bvec, skip, (B))          \
 107                 if (skip == bvec->bv_len) {                     \
 108                         bvec++;                                 \
 109                         skip = 0;                               \
 110                 }                                               \
 111                 i->nr_segs -= bvec - i->bvec;                   \
 112                 i->bvec = bvec;                                 \
 113         } else if (unlikely(i->type & ITER_KVEC)) {             \
 114                 const struct kvec *kvec;                        \
 115                 struct kvec v;                                  \
 116                 iterate_kvec(i, n, v, kvec, skip, (K))          \
 117                 if (skip == kvec->iov_len) {                    \
 118                         kvec++;                                 \
 119                         skip = 0;                               \
 120                 }                                               \
 121                 i->nr_segs -= kvec - i->kvec;                   \
 122                 i->kvec = kvec;                                 \
 123         } else {                                                \
 124                 const struct iovec *iov;                        \
 125                 struct iovec v;                                 \
 126                 iterate_iovec(i, n, v, iov, skip, (I))          \
 127                 if (skip == iov->iov_len) {                     \
 128                         iov++;                                  \
 129                         skip = 0;                               \
 130                 }                                               \
 131                 i->nr_segs -= iov - i->iov;                     \
 132                 i->iov = iov;                                   \
 133         }                                                       \
 134         i->count -= n;                                          \
 135         i->iov_offset = skip;                                   \
 136 }
 137
 138 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
 139                          struct iov_iter *i)
 140 {
 141         size_t skip, copy, left, wanted;
 142         const struct iovec *iov;
 143         char __user *buf;
 144         void *kaddr, *from;
 145
 146         if (unlikely(bytes > i->count))
 147                 bytes = i->count;
 148
 149         if (unlikely(!bytes))
 150                 return 0;
 151
 152         wanted = bytes;
 153         iov = i->iov;
 154         skip = i->iov_offset;
 155         buf = iov->iov_base + skip;
 156         copy = min(bytes, iov->iov_len - skip);
 157
 158         if (!fault_in_pages_writeable(buf, copy)) {
 159                 kaddr = kmap_atomic(page);
 160                 from = kaddr + offset;
 161
 162                 /* first chunk, usually the only one */
 163                 left = __copy_to_user_inatomic(buf, from, copy);
 164                 copy -= left;
 165                 skip += copy;
 166                 from += copy;
 167                 bytes -= copy;
 168
 169                 while (unlikely(!left && bytes)) {
 170                         iov++;
 171                         buf = iov->iov_base;
 172                         copy = min(bytes, iov->iov_len);
 173                         left = __copy_to_user_inatomic(buf, from, copy);
 174                         copy -= left;
 175                         skip = copy;
 176                         from += copy;
 177                         bytes -= copy;
 178                 }
 179                 if (likely(!bytes)) {
 180                         kunmap_atomic(kaddr);
 181                         goto done;
 182                 }
 183                 offset = from - kaddr;
 184                 buf += copy;
 185                 kunmap_atomic(kaddr);
 186                 copy = min(bytes, iov->iov_len - skip);
 187         }
 188         /* Too bad - revert to non-atomic kmap */
 189         kaddr = kmap(page);
 190         from = kaddr + offset;
 191         left = __copy_to_user(buf, from, copy);
 192         copy -= left;
 193         skip += copy;
 194         from += copy;
 195         bytes -= copy;
 196         while (unlikely(!left && bytes)) {
 197                 iov++;
 198                 buf = iov->iov_base;
 199                 copy = min(bytes, iov->iov_len);
 200                 left = __copy_to_user(buf, from, copy);
 201                 copy -= left;
 202                 skip = copy;
 203                 from += copy;
 204                 bytes -= copy;
 205         }
 206         kunmap(page);
 207 done:
 208         if (skip == iov->iov_len) {
 209                 iov++;
 210                 skip = 0;
 211         }
 212         i->count -= wanted - bytes;
 213         i->nr_segs -= iov - i->iov;
 214         i->iov = iov;
 215         i->iov_offset = skip;
 216         return wanted - bytes;
 217 }
 218
 219 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
 220                          struct iov_iter *i)
 221 {
 222         size_t skip, copy, left, wanted;
 223         const struct iovec *iov;
 224         char __user *buf;
 225         void *kaddr, *to;
 226
 227         if (unlikely(bytes > i->count))
 228                 bytes = i->count;
 229
 230         if (unlikely(!bytes))
 231                 return 0;
 232
 233         wanted = bytes;
 234         iov = i->iov;
 235         skip = i->iov_offset;
 236         buf = iov->iov_base + skip;
 237         copy = min(bytes, iov->iov_len - skip);
 238
 239         if (!fault_in_pages_readable(buf, copy)) {
 240                 kaddr = kmap_atomic(page);
 241                 to = kaddr + offset;
 242
 243                 /* first chunk, usually the only one */
 244                 left = __copy_from_user_inatomic(to, buf, copy);
 245                 copy -= left;
 246                 skip += copy;
 247                 to += copy;
 248                 bytes -= copy;
 249
 250                 while (unlikely(!left && bytes)) {
 251                         iov++;
 252                         buf = iov->iov_base;
 253                         copy = min(bytes, iov->iov_len);
 254                         left = __copy_from_user_inatomic(to, buf, copy);
 255                         copy -= left;
 256                         skip = copy;
 257                         to += copy;
 258                         bytes -= copy;
 259                 }
 260                 if (likely(!bytes)) {
 261                         kunmap_atomic(kaddr);
 262                         goto done;
 263                 }
 264                 offset = to - kaddr;
 265                 buf += copy;
 266                 kunmap_atomic(kaddr);
 267                 copy = min(bytes, iov->iov_len - skip);
 268         }
 269         /* Too bad - revert to non-atomic kmap */
 270         kaddr = kmap(page);
 271         to = kaddr + offset;
 272         left = __copy_from_user(to, buf, copy);
 273         copy -= left;
 274         skip += copy;
 275         to += copy;
 276         bytes -= copy;
 277         while (unlikely(!left && bytes)) {
 278                 iov++;
 279                 buf = iov->iov_base;
 280                 copy = min(bytes, iov->iov_len);
 281                 left = __copy_from_user(to, buf, copy);
 282                 copy -= left;
 283                 skip = copy;
 284                 to += copy;
 285                 bytes -= copy;
 286         }
 287         kunmap(page);
 288 done:
 289         if (skip == iov->iov_len) {
 290                 iov++;
 291                 skip = 0;
 292         }
 293         i->count -= wanted - bytes;
 294         i->nr_segs -= iov - i->iov;
 295         i->iov = iov;
 296         i->iov_offset = skip;
 297         return wanted - bytes;
 298 }
 299
 300 /*
 301  * Fault in the first iovec of the given iov_iter, to a maximum length
 302  * of bytes. Returns 0 on success, or non-zero if the memory could not be
 303  * accessed (ie. because it is an invalid address).
 304  *
 305  * writev-intensive code may want this to prefault several iovecs -- that
 306  * would be possible (callers must not rely on the fact that _only_ the
 307  * first iovec will be faulted with the current implementation).
 308  */
 309 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 310 {
 311         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 312                 char __user *buf = i->iov->iov_base + i->iov_offset;
 313                 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
 314                 return fault_in_pages_readable(buf, bytes);
 315         }
 316         return 0;
 317 }
 318 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 319
 320 /*
 321  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 322  * bytes.  For each iovec, fault in each page that constitutes the iovec.
 323  *
 324  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 325  * because it is an invalid address).
 326  */
 327 int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes)
 328 {
 329         size_t skip = i->iov_offset;
 330         const struct iovec *iov;
 331         int err;
 332         struct iovec v;
 333
 334         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 335                 iterate_iovec(i, bytes, v, iov, skip, ({
 336                         err = fault_in_multipages_readable(v.iov_base,
 337                                         v.iov_len);
 338                         if (unlikely(err))
 339                         return err;
 340                 0;}))
 341         }
 342         return 0;
 343 }
 344 EXPORT_SYMBOL(iov_iter_fault_in_multipages_readable);
 345
 346 void iov_iter_init(struct iov_iter *i, int direction,
 347                         const struct iovec *iov, unsigned long nr_segs,
 348                         size_t count)
 349 {
 350         /* It will get better.  Eventually... */
 351         if (segment_eq(get_fs(), KERNEL_DS)) {
 352                 direction |= ITER_KVEC;
 353                 i->type = direction;
 354                 i->kvec = (struct kvec *)iov;
 355         } else {
 356                 i->type = direction;
 357                 i->iov = iov;
 358         }
 359         i->nr_segs = nr_segs;
 360         i->iov_offset = 0;
 361         i->count = count;
 362 }
 363 EXPORT_SYMBOL(iov_iter_init);
 364
 365 static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
 366 {
 367         char *from = kmap_atomic(page);
 368         memcpy(to, from + offset, len);
 369         kunmap_atomic(from);
 370 }
 371
 372 static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 373 {
 374         char *to = kmap_atomic(page);
 375         memcpy(to + offset, from, len);
 376         kunmap_atomic(to);
 377 }
 378
 379 static void memzero_page(struct page *page, size_t offset, size_t len)
 380 {
 381         char *addr = kmap_atomic(page);
 382         memset(addr + offset, 0, len);
 383         kunmap_atomic(addr);
 384 }
 385
 386 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 387 {
 388         const char *from = addr;
 389         if (unlikely(bytes > i->count))
 390                 bytes = i->count;
 391
 392         if (unlikely(!bytes))
 393                 return 0;
 394
 395         iterate_and_advance(i, bytes, v,
 396                 __copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
 397                                v.iov_len),
 398                 memcpy_to_page(v.bv_page, v.bv_offset,
 399                                (from += v.bv_len) - v.bv_len, v.bv_len),
 400                 memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
 401         )
 402
 403         return bytes;
 404 }
 405 EXPORT_SYMBOL(copy_to_iter);
 406
 407 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 408 {
 409         char *to = addr;
 410         if (unlikely(bytes > i->count))
 411                 bytes = i->count;
 412
 413         if (unlikely(!bytes))
 414                 return 0;
 415
 416         iterate_and_advance(i, bytes, v,
 417                 __copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
 418                                  v.iov_len),
 419                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 420                                  v.bv_offset, v.bv_len),
 421                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 422         )
 423
 424         return bytes;
 425 }
 426 EXPORT_SYMBOL(copy_from_iter);
 427
 428 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 429 {
 430         char *to = addr;
 431         if (unlikely(bytes > i->count))
 432                 bytes = i->count;
 433
 434         if (unlikely(!bytes))
 435                 return 0;
 436
 437         iterate_and_advance(i, bytes, v,
 438                 __copy_from_user_nocache((to += v.iov_len) - v.iov_len,
 439                                          v.iov_base, v.iov_len),
 440                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 441                                  v.bv_offset, v.bv_len),
 442                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 443         )
 444
 445         return bytes;
 446 }
 447 EXPORT_SYMBOL(copy_from_iter_nocache);
 448
 449 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 450                          struct iov_iter *i)
 451 {
 452         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 453                 void *kaddr = kmap_atomic(page);
 454                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 455                 kunmap_atomic(kaddr);
 456                 return wanted;
 457         } else
 458                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 459 }
 460 EXPORT_SYMBOL(copy_page_to_iter);
 461
 462 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 463                          struct iov_iter *i)
 464 {
 465         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 466                 void *kaddr = kmap_atomic(page);
 467                 size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
 468                 kunmap_atomic(kaddr);
 469                 return wanted;
 470         } else
 471                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 472 }
 473 EXPORT_SYMBOL(copy_page_from_iter);
 474
 475 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 476 {
 477         if (unlikely(bytes > i->count))
 478                 bytes = i->count;
 479
 480         if (unlikely(!bytes))
 481                 return 0;
 482
 483         iterate_and_advance(i, bytes, v,
 484                 __clear_user(v.iov_base, v.iov_len),
 485                 memzero_page(v.bv_page, v.bv_offset, v.bv_len),
 486                 memset(v.iov_base, 0, v.iov_len)
 487         )
 488
 489         return bytes;
 490 }
 491 EXPORT_SYMBOL(iov_iter_zero);
 492
 493 size_t iov_iter_copy_from_user_atomic(struct page *page,
 494                 struct iov_iter *i, unsigned long offset, size_t bytes)
 495 {
 496         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 497         iterate_all_kinds(i, bytes, v,
 498                 __copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
 499                                           v.iov_base, v.iov_len),
 500                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 501                                  v.bv_offset, v.bv_len),
 502                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 503         )
 504         kunmap_atomic(kaddr);
 505         return bytes;
 506 }
 507 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 508
 509 void iov_iter_advance(struct iov_iter *i, size_t size)
 510 {
 511         iterate_and_advance(i, size, v, 0, 0, 0)
 512 }
 513 EXPORT_SYMBOL(iov_iter_advance);
 514
 515 /*
 516  * Return the count of just the current iov_iter segment.
 517  */
 518 size_t iov_iter_single_seg_count(const struct iov_iter *i)
 519 {
 520         if (i->nr_segs == 1)
 521                 return i->count;
 522         else if (i->type & ITER_BVEC)
 523                 return min(i->count, i->bvec->bv_len - i->iov_offset);
 524         else
 525                 return min(i->count, i->iov->iov_len - i->iov_offset);
 526 }
 527 EXPORT_SYMBOL(iov_iter_single_seg_count);
 528
 529 void iov_iter_kvec(struct iov_iter *i, int direction,
 530                         const struct kvec *kvec, unsigned long nr_segs,
 531                         size_t count)
 532 {
 533         BUG_ON(!(direction & ITER_KVEC));
 534         i->type = direction;
 535         i->kvec = kvec;
 536         i->nr_segs = nr_segs;
 537         i->iov_offset = 0;
 538         i->count = count;
 539 }
 540 EXPORT_SYMBOL(iov_iter_kvec);
 541
 542 void iov_iter_bvec(struct iov_iter *i, int direction,
 543                         const struct bio_vec *bvec, unsigned long nr_segs,
 544                         size_t count)
 545 {
 546         BUG_ON(!(direction & ITER_BVEC));
 547         i->type = direction;
 548         i->bvec = bvec;
 549         i->nr_segs = nr_segs;
 550         i->iov_offset = 0;
 551         i->count = count;
 552 }
 553 EXPORT_SYMBOL(iov_iter_bvec);
 554
 555 unsigned long iov_iter_alignment(const struct iov_iter *i)
 556 {
 557         unsigned long res = 0;
 558         size_t size = i->count;
 559
 560         if (!size)
 561                 return 0;
 562
 563         iterate_all_kinds(i, size, v,
 564                 (res |= (unsigned long)v.iov_base | v.iov_len, 0),
 565                 res |= v.bv_offset | v.bv_len,
 566                 res |= (unsigned long)v.iov_base | v.iov_len
 567         )
 568         return res;
 569 }
 570 EXPORT_SYMBOL(iov_iter_alignment);
 571
 572 ssize_t iov_iter_get_pages(struct iov_iter *i,
 573                    struct page **pages, size_t maxsize, unsigned maxpages,
 574                    size_t *start)
 575 {
 576         if (maxsize > i->count)
 577                 maxsize = i->count;
 578
 579         if (!maxsize)
 580                 return 0;
 581
 582         iterate_all_kinds(i, maxsize, v, ({
 583                 unsigned long addr = (unsigned long)v.iov_base;
 584                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
 585                 int n;
 586                 int res;
 587
 588                 if (len > maxpages * PAGE_SIZE)
 589                         len = maxpages * PAGE_SIZE;
 590                 addr &= ~(PAGE_SIZE - 1);
 591                 n = DIV_ROUND_UP(len, PAGE_SIZE);
 592                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
 593                 if (unlikely(res < 0))
 594                         return res;
 595                 return (res == n ? len : res * PAGE_SIZE) - *start;
 596         0;}),({
 597                 /* can't be more than PAGE_SIZE */
 598                 *start = v.bv_offset;
 599                 get_page(*pages = v.bv_page);
 600                 return v.bv_len;
 601         }),({
 602                 return -EFAULT;
 603         })
 604         )
 605         return 0;
 606 }
 607 EXPORT_SYMBOL(iov_iter_get_pages);
 608
 609 static struct page **get_pages_array(size_t n)
 610 {
 611         struct page **p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
 612         if (!p)
 613                 p = vmalloc(n * sizeof(struct page *));
 614         return p;
 615 }
 616
 617 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 618                    struct page ***pages, size_t maxsize,
 619                    size_t *start)
 620 {
 621         struct page **p;
 622
 623         if (maxsize > i->count)
 624                 maxsize = i->count;
 625
 626         if (!maxsize)
 627                 return 0;
 628
 629         iterate_all_kinds(i, maxsize, v, ({
 630                 unsigned long addr = (unsigned long)v.iov_base;
 631                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
 632                 int n;
 633                 int res;
 634
 635                 addr &= ~(PAGE_SIZE - 1);
 636                 n = DIV_ROUND_UP(len, PAGE_SIZE);
 637                 p = get_pages_array(n);
 638                 if (!p)
 639                         return -ENOMEM;
 640                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
 641                 if (unlikely(res < 0)) {
 642                         kvfree(p);
 643                         return res;
 644                 }
 645                 *pages = p;
 646                 return (res == n ? len : res * PAGE_SIZE) - *start;
 647         0;}),({
 648                 /* can't be more than PAGE_SIZE */
 649                 *start = v.bv_offset;
 650                 *pages = p = get_pages_array(1);
 651                 if (!p)
 652                         return -ENOMEM;
 653                 get_page(*p = v.bv_page);
 654                 return v.bv_len;
 655         }),({
 656                 return -EFAULT;
 657         })
 658         )
 659         return 0;
 660 }
 661 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
 662
 663 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 664                                struct iov_iter *i)
 665 {
 666         char *to = addr;
 667         __wsum sum, next;
 668         size_t off = 0;
 669         if (unlikely(bytes > i->count))
 670                 bytes = i->count;
 671
 672         if (unlikely(!bytes))
 673                 return 0;
 674
 675         sum = *csum;
 676         iterate_and_advance(i, bytes, v, ({
 677                 int err = 0;
 678                 next = csum_and_copy_from_user(v.iov_base,
 679                                                (to += v.iov_len) - v.iov_len,
 680                                                v.iov_len, 0, &err);
 681                 if (!err) {
 682                         sum = csum_block_add(sum, next, off);
 683                         off += v.iov_len;
 684                 }
 685                 err ? v.iov_len : 0;
 686         }), ({
 687                 char *p = kmap_atomic(v.bv_page);
 688                 next = csum_partial_copy_nocheck(p + v.bv_offset,
 689                                                  (to += v.bv_len) - v.bv_len,
 690                                                  v.bv_len, 0);
 691                 kunmap_atomic(p);
 692                 sum = csum_block_add(sum, next, off);
 693                 off += v.bv_len;
 694         }),({
 695                 next = csum_partial_copy_nocheck(v.iov_base,
 696                                                  (to += v.iov_len) - v.iov_len,
 697                                                  v.iov_len, 0);
 698                 sum = csum_block_add(sum, next, off);
 699                 off += v.iov_len;
 700         })
 701         )
 702         *csum = sum;
 703         return bytes;
 704 }
 705 EXPORT_SYMBOL(csum_and_copy_from_iter);
 706
 707 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
 708                              struct iov_iter *i)
 709 {
 710         const char *from = addr;
 711         __wsum sum, next;
 712         size_t off = 0;
 713         if (unlikely(bytes > i->count))
 714                 bytes = i->count;
 715
 716         if (unlikely(!bytes))
 717                 return 0;
 718
 719         sum = *csum;
 720         iterate_and_advance(i, bytes, v, ({
 721                 int err = 0;
 722                 next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
 723                                              v.iov_base,
 724                                              v.iov_len, 0, &err);
 725                 if (!err) {
 726                         sum = csum_block_add(sum, next, off);
 727                         off += v.iov_len;
 728                 }
 729                 err ? v.iov_len : 0;
 730         }), ({
 731                 char *p = kmap_atomic(v.bv_page);
 732                 next = csum_partial_copy_nocheck((from += v.bv_len) - v.bv_len,
 733                                                  p + v.bv_offset,
 734                                                  v.bv_len, 0);
 735                 kunmap_atomic(p);
 736                 sum = csum_block_add(sum, next, off);
 737                 off += v.bv_len;
 738         }),({
 739                 next = csum_partial_copy_nocheck((from += v.iov_len) - v.iov_len,
 740                                                  v.iov_base,
 741                                                  v.iov_len, 0);
 742                 sum = csum_block_add(sum, next, off);
 743                 off += v.iov_len;
 744         })
 745         )
 746         *csum = sum;
 747         return bytes;
 748 }
 749 EXPORT_SYMBOL(csum_and_copy_to_iter);
 750
 751 int iov_iter_npages(const struct iov_iter *i, int maxpages)
 752 {
 753         size_t size = i->count;
 754         int npages = 0;
 755
 756         if (!size)
 757                 return 0;
 758
 759         iterate_all_kinds(i, size, v, ({
 760                 unsigned long p = (unsigned long)v.iov_base;
 761                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
 762                         - p / PAGE_SIZE;
 763                 if (npages >= maxpages)
 764                         return maxpages;
 765         0;}),({
 766                 npages++;
 767                 if (npages >= maxpages)
 768                         return maxpages;
 769         }),({
 770                 unsigned long p = (unsigned long)v.iov_base;
 771                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
 772                         - p / PAGE_SIZE;
 773                 if (npages >= maxpages)
 774                         return maxpages;
 775         })
 776         )
 777         return npages;
 778 }
 779 EXPORT_SYMBOL(iov_iter_npages);
 780
 781 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 782 {
 783         *new = *old;
 784         if (new->type & ITER_BVEC)
 785                 return new->bvec = kmemdup(new->bvec,
 786                                     new->nr_segs * sizeof(struct bio_vec),
 787                                     flags);
 788         else
 789                 /* iovec and kvec have identical layout */
 790                 return new->iov = kmemdup(new->iov,
 791                                    new->nr_segs * sizeof(struct iovec),
 792                                    flags);
 793 }
 794 EXPORT_SYMBOL(dup_iter);
 795
 796 int import_iovec(int type, const struct iovec __user * uvector,
 797                  unsigned nr_segs, unsigned fast_segs,
 798                  struct iovec **iov, struct iov_iter *i)
 799 {
 800         ssize_t n;
 801         struct iovec *p;
 802         n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
 803                                   *iov, &p);
 804         if (n < 0) {
 805                 if (p != *iov)
 806                         kfree(p);
 807                 *iov = NULL;
 808                 return n;
 809         }
 810         iov_iter_init(i, type, p, nr_segs, n);
 811         *iov = p == *iov ? NULL : p;
 812         return 0;
 813 }
 814 EXPORT_SYMBOL(import_iovec);
 815
 816 #ifdef CONFIG_COMPAT
 817 #include <linux/compat.h>
 818
 819 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 820                  unsigned nr_segs, unsigned fast_segs,
 821                  struct iovec **iov, struct iov_iter *i)
 822 {
 823         ssize_t n;
 824         struct iovec *p;
 825         n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
 826                                   *iov, &p);
 827         if (n < 0) {
 828                 if (p != *iov)
 829                         kfree(p);
 830                 *iov = NULL;
 831                 return n;
 832         }
 833         iov_iter_init(i, type, p, nr_segs, n);
 834         *iov = p == *iov ? NULL : p;
 835         return 0;
 836 }
 837 #endif
 838
 839 int import_single_range(int rw, void __user *buf, size_t len,
 840                  struct iovec *iov, struct iov_iter *i)
 841 {
 842         if (len > MAX_RW_COUNT)
 843                 len = MAX_RW_COUNT;
 844         if (unlikely(!access_ok(!rw, buf, len)))
 845                 return -EFAULT;
 846
 847         iov->iov_base = buf;
 848         iov->iov_len = len;
 849         iov_iter_init(i, rw, iov, 1, len);
 850         return 0;
 851 }
 852 EXPORT_SYMBOL(import_single_range);