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