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