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 one or more iovecs of the given iov_iter, to a maximum length of
 302  * bytes.  For each iovec, fault in each page that constitutes the iovec.
 303  *
 304  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 305  * because it is an invalid address).
 306  */
 307 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 308 {
 309         size_t skip = i->iov_offset;
 310         const struct iovec *iov;
 311         int err;
 312         struct iovec v;
 313
 314         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 315                 iterate_iovec(i, bytes, v, iov, skip, ({
 316                         err = fault_in_multipages_readable(v.iov_base,
 317                                         v.iov_len);
 318                         if (unlikely(err))
 319                         return err;
 320                 0;}))
 321         }
 322         return 0;
 323 }
 324 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 325
 326 void iov_iter_init(struct iov_iter *i, int direction,
 327                         const struct iovec *iov, unsigned long nr_segs,
 328                         size_t count)
 329 {
 330         /* It will get better.  Eventually... */
 331         if (segment_eq(get_fs(), KERNEL_DS)) {
 332                 direction |= ITER_KVEC;
 333                 i->type = direction;
 334                 i->kvec = (struct kvec *)iov;
 335         } else {
 336                 i->type = direction;
 337                 i->iov = iov;
 338         }
 339         i->nr_segs = nr_segs;
 340         i->iov_offset = 0;
 341         i->count = count;
 342 }
 343 EXPORT_SYMBOL(iov_iter_init);
 344
 345 static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
 346 {
 347         char *from = kmap_atomic(page);
 348         memcpy(to, from + offset, len);
 349         kunmap_atomic(from);
 350 }
 351
 352 static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)
 353 {
 354         char *to = kmap_atomic(page);
 355         memcpy(to + offset, from, len);
 356         kunmap_atomic(to);
 357 }
 358
 359 static void memzero_page(struct page *page, size_t offset, size_t len)
 360 {
 361         char *addr = kmap_atomic(page);
 362         memset(addr + offset, 0, len);
 363         kunmap_atomic(addr);
 364 }
 365
 366 size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i)
 367 {
 368         char *from = addr;
 369         if (unlikely(bytes > i->count))
 370                 bytes = i->count;
 371
 372         if (unlikely(!bytes))
 373                 return 0;
 374
 375         iterate_and_advance(i, bytes, v,
 376                 __copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
 377                                v.iov_len),
 378                 memcpy_to_page(v.bv_page, v.bv_offset,
 379                                (from += v.bv_len) - v.bv_len, v.bv_len),
 380                 memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
 381         )
 382
 383         return bytes;
 384 }
 385 EXPORT_SYMBOL(copy_to_iter);
 386
 387 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 388 {
 389         char *to = addr;
 390         if (unlikely(bytes > i->count))
 391                 bytes = i->count;
 392
 393         if (unlikely(!bytes))
 394                 return 0;
 395
 396         iterate_and_advance(i, bytes, v,
 397                 __copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
 398                                  v.iov_len),
 399                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 400                                  v.bv_offset, v.bv_len),
 401                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 402         )
 403
 404         return bytes;
 405 }
 406 EXPORT_SYMBOL(copy_from_iter);
 407
 408 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 409 {
 410         char *to = addr;
 411         if (unlikely(bytes > i->count))
 412                 bytes = i->count;
 413
 414         if (unlikely(!bytes))
 415                 return 0;
 416
 417         iterate_and_advance(i, bytes, v,
 418                 __copy_from_user_nocache((to += v.iov_len) - v.iov_len,
 419                                          v.iov_base, v.iov_len),
 420                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 421                                  v.bv_offset, v.bv_len),
 422                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 423         )
 424
 425         return bytes;
 426 }
 427 EXPORT_SYMBOL(copy_from_iter_nocache);
 428
 429 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 430                          struct iov_iter *i)
 431 {
 432         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 433                 void *kaddr = kmap_atomic(page);
 434                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 435                 kunmap_atomic(kaddr);
 436                 return wanted;
 437         } else
 438                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 439 }
 440 EXPORT_SYMBOL(copy_page_to_iter);
 441
 442 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 443                          struct iov_iter *i)
 444 {
 445         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 446                 void *kaddr = kmap_atomic(page);
 447                 size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
 448                 kunmap_atomic(kaddr);
 449                 return wanted;
 450         } else
 451                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 452 }
 453 EXPORT_SYMBOL(copy_page_from_iter);
 454
 455 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 456 {
 457         if (unlikely(bytes > i->count))
 458                 bytes = i->count;
 459
 460         if (unlikely(!bytes))
 461                 return 0;
 462
 463         iterate_and_advance(i, bytes, v,
 464                 __clear_user(v.iov_base, v.iov_len),
 465                 memzero_page(v.bv_page, v.bv_offset, v.bv_len),
 466                 memset(v.iov_base, 0, v.iov_len)
 467         )
 468
 469         return bytes;
 470 }
 471 EXPORT_SYMBOL(iov_iter_zero);
 472
 473 size_t iov_iter_copy_from_user_atomic(struct page *page,
 474                 struct iov_iter *i, unsigned long offset, size_t bytes)
 475 {
 476         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 477         iterate_all_kinds(i, bytes, v,
 478                 __copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
 479                                           v.iov_base, v.iov_len),
 480                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 481                                  v.bv_offset, v.bv_len),
 482                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 483         )
 484         kunmap_atomic(kaddr);
 485         return bytes;
 486 }
 487 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 488
 489 void iov_iter_advance(struct iov_iter *i, size_t size)
 490 {
 491         iterate_and_advance(i, size, v, 0, 0, 0)
 492 }
 493 EXPORT_SYMBOL(iov_iter_advance);
 494
 495 /*
 496  * Return the count of just the current iov_iter segment.
 497  */
 498 size_t iov_iter_single_seg_count(const struct iov_iter *i)
 499 {
 500         if (i->nr_segs == 1)
 501                 return i->count;
 502         else if (i->type & ITER_BVEC)
 503                 return min(i->count, i->bvec->bv_len - i->iov_offset);
 504         else
 505                 return min(i->count, i->iov->iov_len - i->iov_offset);
 506 }
 507 EXPORT_SYMBOL(iov_iter_single_seg_count);
 508
 509 void iov_iter_kvec(struct iov_iter *i, int direction,
 510                         const struct kvec *kvec, unsigned long nr_segs,
 511                         size_t count)
 512 {
 513         BUG_ON(!(direction & ITER_KVEC));
 514         i->type = direction;
 515         i->kvec = kvec;
 516         i->nr_segs = nr_segs;
 517         i->iov_offset = 0;
 518         i->count = count;
 519 }
 520 EXPORT_SYMBOL(iov_iter_kvec);
 521
 522 void iov_iter_bvec(struct iov_iter *i, int direction,
 523                         const struct bio_vec *bvec, unsigned long nr_segs,
 524                         size_t count)
 525 {
 526         BUG_ON(!(direction & ITER_BVEC));
 527         i->type = direction;
 528         i->bvec = bvec;
 529         i->nr_segs = nr_segs;
 530         i->iov_offset = 0;
 531         i->count = count;
 532 }
 533 EXPORT_SYMBOL(iov_iter_bvec);
 534
 535 unsigned long iov_iter_alignment(const struct iov_iter *i)
 536 {
 537         unsigned long res = 0;
 538         size_t size = i->count;
 539
 540         if (!size)
 541                 return 0;
 542
 543         iterate_all_kinds(i, size, v,
 544                 (res |= (unsigned long)v.iov_base | v.iov_len, 0),
 545                 res |= v.bv_offset | v.bv_len,
 546                 res |= (unsigned long)v.iov_base | v.iov_len
 547         )
 548         return res;
 549 }
 550 EXPORT_SYMBOL(iov_iter_alignment);
 551
 552 ssize_t iov_iter_get_pages(struct iov_iter *i,
 553                    struct page **pages, size_t maxsize, unsigned maxpages,
 554                    size_t *start)
 555 {
 556         if (maxsize > i->count)
 557                 maxsize = i->count;
 558
 559         if (!maxsize)
 560                 return 0;
 561
 562         iterate_all_kinds(i, maxsize, v, ({
 563                 unsigned long addr = (unsigned long)v.iov_base;
 564                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
 565                 int n;
 566                 int res;
 567
 568                 if (len > maxpages * PAGE_SIZE)
 569                         len = maxpages * PAGE_SIZE;
 570                 addr &= ~(PAGE_SIZE - 1);
 571                 n = DIV_ROUND_UP(len, PAGE_SIZE);
 572                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
 573                 if (unlikely(res < 0))
 574                         return res;
 575                 return (res == n ? len : res * PAGE_SIZE) - *start;
 576         0;}),({
 577                 /* can't be more than PAGE_SIZE */
 578                 *start = v.bv_offset;
 579                 get_page(*pages = v.bv_page);
 580                 return v.bv_len;
 581         }),({
 582                 return -EFAULT;
 583         })
 584         )
 585         return 0;
 586 }
 587 EXPORT_SYMBOL(iov_iter_get_pages);
 588
 589 static struct page **get_pages_array(size_t n)
 590 {
 591         struct page **p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
 592         if (!p)
 593                 p = vmalloc(n * sizeof(struct page *));
 594         return p;
 595 }
 596
 597 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 598                    struct page ***pages, size_t maxsize,
 599                    size_t *start)
 600 {
 601         struct page **p;
 602
 603         if (maxsize > i->count)
 604                 maxsize = i->count;
 605
 606         if (!maxsize)
 607                 return 0;
 608
 609         iterate_all_kinds(i, maxsize, v, ({
 610                 unsigned long addr = (unsigned long)v.iov_base;
 611                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
 612                 int n;
 613                 int res;
 614
 615                 addr &= ~(PAGE_SIZE - 1);
 616                 n = DIV_ROUND_UP(len, PAGE_SIZE);
 617                 p = get_pages_array(n);
 618                 if (!p)
 619                         return -ENOMEM;
 620                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
 621                 if (unlikely(res < 0)) {
 622                         kvfree(p);
 623                         return res;
 624                 }
 625                 *pages = p;
 626                 return (res == n ? len : res * PAGE_SIZE) - *start;
 627         0;}),({
 628                 /* can't be more than PAGE_SIZE */
 629                 *start = v.bv_offset;
 630                 *pages = p = get_pages_array(1);
 631                 if (!p)
 632                         return -ENOMEM;
 633                 get_page(*p = v.bv_page);
 634                 return v.bv_len;
 635         }),({
 636                 return -EFAULT;
 637         })
 638         )
 639         return 0;
 640 }
 641 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
 642
 643 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 644                                struct iov_iter *i)
 645 {
 646         char *to = addr;
 647         __wsum sum, next;
 648         size_t off = 0;
 649         if (unlikely(bytes > i->count))
 650                 bytes = i->count;
 651
 652         if (unlikely(!bytes))
 653                 return 0;
 654
 655         sum = *csum;
 656         iterate_and_advance(i, bytes, v, ({
 657                 int err = 0;
 658                 next = csum_and_copy_from_user(v.iov_base,
 659                                                (to += v.iov_len) - v.iov_len,
 660                                                v.iov_len, 0, &err);
 661                 if (!err) {
 662                         sum = csum_block_add(sum, next, off);
 663                         off += v.iov_len;
 664                 }
 665                 err ? v.iov_len : 0;
 666         }), ({
 667                 char *p = kmap_atomic(v.bv_page);
 668                 next = csum_partial_copy_nocheck(p + v.bv_offset,
 669                                                  (to += v.bv_len) - v.bv_len,
 670                                                  v.bv_len, 0);
 671                 kunmap_atomic(p);
 672                 sum = csum_block_add(sum, next, off);
 673                 off += v.bv_len;
 674         }),({
 675                 next = csum_partial_copy_nocheck(v.iov_base,
 676                                                  (to += v.iov_len) - v.iov_len,
 677                                                  v.iov_len, 0);
 678                 sum = csum_block_add(sum, next, off);
 679                 off += v.iov_len;
 680         })
 681         )
 682         *csum = sum;
 683         return bytes;
 684 }
 685 EXPORT_SYMBOL(csum_and_copy_from_iter);
 686
 687 size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum,
 688                              struct iov_iter *i)
 689 {
 690         char *from = addr;
 691         __wsum sum, next;
 692         size_t off = 0;
 693         if (unlikely(bytes > i->count))
 694                 bytes = i->count;
 695
 696         if (unlikely(!bytes))
 697                 return 0;
 698
 699         sum = *csum;
 700         iterate_and_advance(i, bytes, v, ({
 701                 int err = 0;
 702                 next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
 703                                              v.iov_base,
 704                                              v.iov_len, 0, &err);
 705                 if (!err) {
 706                         sum = csum_block_add(sum, next, off);
 707                         off += v.iov_len;
 708                 }
 709                 err ? v.iov_len : 0;
 710         }), ({
 711                 char *p = kmap_atomic(v.bv_page);
 712                 next = csum_partial_copy_nocheck((from += v.bv_len) - v.bv_len,
 713                                                  p + v.bv_offset,
 714                                                  v.bv_len, 0);
 715                 kunmap_atomic(p);
 716                 sum = csum_block_add(sum, next, off);
 717                 off += v.bv_len;
 718         }),({
 719                 next = csum_partial_copy_nocheck((from += v.iov_len) - v.iov_len,
 720                                                  v.iov_base,
 721                                                  v.iov_len, 0);
 722                 sum = csum_block_add(sum, next, off);
 723                 off += v.iov_len;
 724         })
 725         )
 726         *csum = sum;
 727         return bytes;
 728 }
 729 EXPORT_SYMBOL(csum_and_copy_to_iter);
 730
 731 int iov_iter_npages(const struct iov_iter *i, int maxpages)
 732 {
 733         size_t size = i->count;
 734         int npages = 0;
 735
 736         if (!size)
 737                 return 0;
 738
 739         iterate_all_kinds(i, size, v, ({
 740                 unsigned long p = (unsigned long)v.iov_base;
 741                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
 742                         - p / PAGE_SIZE;
 743                 if (npages >= maxpages)
 744                         return maxpages;
 745         0;}),({
 746                 npages++;
 747                 if (npages >= maxpages)
 748                         return maxpages;
 749         }),({
 750                 unsigned long p = (unsigned long)v.iov_base;
 751                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
 752                         - p / PAGE_SIZE;
 753                 if (npages >= maxpages)
 754                         return maxpages;
 755         })
 756         )
 757         return npages;
 758 }
 759 EXPORT_SYMBOL(iov_iter_npages);
 760
 761 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 762 {
 763         *new = *old;
 764         if (new->type & ITER_BVEC)
 765                 return new->bvec = kmemdup(new->bvec,
 766                                     new->nr_segs * sizeof(struct bio_vec),
 767                                     flags);
 768         else
 769                 /* iovec and kvec have identical layout */
 770                 return new->iov = kmemdup(new->iov,
 771                                    new->nr_segs * sizeof(struct iovec),
 772                                    flags);
 773 }
 774 EXPORT_SYMBOL(dup_iter);
 775
 776 int import_iovec(int type, const struct iovec __user * uvector,
 777                  unsigned nr_segs, unsigned fast_segs,
 778                  struct iovec **iov, struct iov_iter *i)
 779 {
 780         ssize_t n;
 781         struct iovec *p;
 782         n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
 783                                   *iov, &p);
 784         if (n < 0) {
 785                 if (p != *iov)
 786                         kfree(p);
 787                 *iov = NULL;
 788                 return n;
 789         }
 790         iov_iter_init(i, type, p, nr_segs, n);
 791         *iov = p == *iov ? NULL : p;
 792         return 0;
 793 }
 794 EXPORT_SYMBOL(import_iovec);
 795
 796 #ifdef CONFIG_COMPAT
 797 #include <linux/compat.h>
 798
 799 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 800                  unsigned nr_segs, unsigned fast_segs,
 801                  struct iovec **iov, struct iov_iter *i)
 802 {
 803         ssize_t n;
 804         struct iovec *p;
 805         n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
 806                                   *iov, &p);
 807         if (n < 0) {
 808                 if (p != *iov)
 809                         kfree(p);
 810                 *iov = NULL;
 811                 return n;
 812         }
 813         iov_iter_init(i, type, p, nr_segs, n);
 814         *iov = p == *iov ? NULL : p;
 815         return 0;
 816 }
 817 #endif
 818
 819 int import_single_range(int rw, void __user *buf, size_t len,
 820                  struct iovec *iov, struct iov_iter *i)
 821 {
 822         if (len > MAX_RW_COUNT)
 823                 len = MAX_RW_COUNT;
 824         if (unlikely(!access_ok(!rw, buf, len)))
 825                 return -EFAULT;
 826
 827         iov->iov_base = buf;
 828         iov->iov_len = len;
 829         iov_iter_init(i, rw, iov, 1, len);
 830         return 0;
 831 }