lib/iov_iter.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <crypto/hash.h>
   3 #include <linux/export.h>
   4 #include <linux/bvec.h>
   5 #include <linux/fault-inject-usercopy.h>
   6 #include <linux/uio.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/highmem.h>
   9 #include <linux/slab.h>
  10 #include <linux/vmalloc.h>
  11 #include <linux/splice.h>
  12 #include <linux/compat.h>
  13 #include <net/checksum.h>
  14 #include <linux/scatterlist.h>
  15 #include <linux/instrumented.h>
  16
  17 #define PIPE_PARANOIA /* for now */
  18
  19 /* covers iovec and kvec alike */
  20 #define iterate_iovec(i, n, base, len, off, __p, STEP) {        \
  21         size_t off = 0;                                         \
  22         size_t skip = i->iov_offset;                            \
  23         do {                                                    \
  24                 len = min(n, __p->iov_len - skip);              \
  25                 if (likely(len)) {                              \
  26                         base = __p->iov_base + skip;            \
  27                         len -= (STEP);                          \
  28                         off += len;                             \
  29                         skip += len;                            \
  30                         n -= len;                               \
  31                         if (skip < __p->iov_len)                \
  32                                 break;                          \
  33                 }                                               \
  34                 __p++;                                          \
  35                 skip = 0;                                       \
  36         } while (n);                                            \
  37         i->iov_offset = skip;                                   \
  38         n = off;                                                \
  39 }
  40
  41 #define iterate_bvec(i, n, base, len, off, p, STEP) {           \
  42         size_t off = 0;                                         \
  43         unsigned skip = i->iov_offset;                          \
  44         while (n) {                                             \
  45                 unsigned offset = p->bv_offset + skip;          \
  46                 unsigned left;                                  \
  47                 void *kaddr = kmap_local_page(p->bv_page +      \
  48                                         offset / PAGE_SIZE);    \
  49                 base = kaddr + offset % PAGE_SIZE;              \
  50                 len = min(min(n, (size_t)(p->bv_len - skip)),   \
  51                      (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
  52                 left = (STEP);                                  \
  53                 kunmap_local(kaddr);                            \
  54                 len -= left;                                    \
  55                 off += len;                                     \
  56                 skip += len;                                    \
  57                 if (skip == p->bv_len) {                        \
  58                         skip = 0;                               \
  59                         p++;                                    \
  60                 }                                               \
  61                 n -= len;                                       \
  62                 if (left)                                       \
  63                         break;                                  \
  64         }                                                       \
  65         i->iov_offset = skip;                                   \
  66         n = off;                                                \
  67 }
  68
  69 #define iterate_xarray(i, n, base, len, __off, STEP) {          \
  70         __label__ __out;                                        \
  71         size_t __off = 0;                                       \
  72         struct page *head = NULL;                               \
  73         loff_t start = i->xarray_start + i->iov_offset;         \
  74         unsigned offset = start % PAGE_SIZE;                    \
  75         pgoff_t index = start / PAGE_SIZE;                      \
  76         int j;                                                  \
  77                                                                 \
  78         XA_STATE(xas, i->xarray, index);                        \
  79                                                                 \
  80         rcu_read_lock();                                        \
  81         xas_for_each(&xas, head, ULONG_MAX) {                   \
  82                 unsigned left;                                  \
  83                 if (xas_retry(&xas, head))                      \
  84                         continue;                               \
  85                 if (WARN_ON(xa_is_value(head)))                 \
  86                         break;                                  \
  87                 if (WARN_ON(PageHuge(head)))                    \
  88                         break;                                  \
  89                 for (j = (head->index < index) ? index - head->index : 0; \
  90                      j < thp_nr_pages(head); j++) {             \
  91                         void *kaddr = kmap_local_page(head + j);        \
  92                         base = kaddr + offset;                  \
  93                         len = PAGE_SIZE - offset;               \
  94                         len = min(n, len);                      \
  95                         left = (STEP);                          \
  96                         kunmap_local(kaddr);                    \
  97                         len -= left;                            \
  98                         __off += len;                           \
  99                         n -= len;                               \
 100                         if (left || n == 0)                     \
 101                                 goto __out;                     \
 102                         offset = 0;                             \
 103                 }                                               \
 104         }                                                       \
 105 __out:                                                          \
 106         rcu_read_unlock();                                      \
 107         i->iov_offset += __off;                                         \
 108         n = __off;                                              \
 109 }
 110
 111 #define __iterate_and_advance(i, n, base, len, off, I, K) {     \
 112         if (unlikely(i->count < n))                             \
 113                 n = i->count;                                   \
 114         if (likely(n)) {                                        \
 115                 if (likely(iter_is_iovec(i))) {                 \
 116                         const struct iovec *iov = i->iov;       \
 117                         void __user *base;                      \
 118                         size_t len;                             \
 119                         iterate_iovec(i, n, base, len, off,     \
 120                                                 iov, (I))       \
 121                         i->nr_segs -= iov - i->iov;             \
 122                         i->iov = iov;                           \
 123                 } else if (iov_iter_is_bvec(i)) {               \
 124                         const struct bio_vec *bvec = i->bvec;   \
 125                         void *base;                             \
 126                         size_t len;                             \
 127                         iterate_bvec(i, n, base, len, off,      \
 128                                                 bvec, (K))      \
 129                         i->nr_segs -= bvec - i->bvec;           \
 130                         i->bvec = bvec;                         \
 131                 } else if (iov_iter_is_kvec(i)) {               \
 132                         const struct kvec *kvec = i->kvec;      \
 133                         void *base;                             \
 134                         size_t len;                             \
 135                         iterate_iovec(i, n, base, len, off,     \
 136                                                 kvec, (K))      \
 137                         i->nr_segs -= kvec - i->kvec;           \
 138                         i->kvec = kvec;                         \
 139                 } else if (iov_iter_is_xarray(i)) {             \
 140                         void *base;                             \
 141                         size_t len;                             \
 142                         iterate_xarray(i, n, base, len, off,    \
 143                                                         (K))    \
 144                 }                                               \
 145                 i->count -= n;                                  \
 146         }                                                       \
 147 }
 148 #define iterate_and_advance(i, n, base, len, off, I, K) \
 149         __iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
 150
 151 static int copyout(void __user *to, const void *from, size_t n)
 152 {
 153         if (should_fail_usercopy())
 154                 return n;
 155         if (access_ok(to, n)) {
 156                 instrument_copy_to_user(to, from, n);
 157                 n = raw_copy_to_user(to, from, n);
 158         }
 159         return n;
 160 }
 161
 162 static int copyin(void *to, const void __user *from, size_t n)
 163 {
 164         if (should_fail_usercopy())
 165                 return n;
 166         if (access_ok(from, n)) {
 167                 instrument_copy_from_user(to, from, n);
 168                 n = raw_copy_from_user(to, from, n);
 169         }
 170         return n;
 171 }
 172
 173 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
 174                          struct iov_iter *i)
 175 {
 176         size_t skip, copy, left, wanted;
 177         const struct iovec *iov;
 178         char __user *buf;
 179         void *kaddr, *from;
 180
 181         if (unlikely(bytes > i->count))
 182                 bytes = i->count;
 183
 184         if (unlikely(!bytes))
 185                 return 0;
 186
 187         might_fault();
 188         wanted = bytes;
 189         iov = i->iov;
 190         skip = i->iov_offset;
 191         buf = iov->iov_base + skip;
 192         copy = min(bytes, iov->iov_len - skip);
 193
 194         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_writeable(buf, copy)) {
 195                 kaddr = kmap_atomic(page);
 196                 from = kaddr + offset;
 197
 198                 /* first chunk, usually the only one */
 199                 left = copyout(buf, from, copy);
 200                 copy -= left;
 201                 skip += copy;
 202                 from += copy;
 203                 bytes -= copy;
 204
 205                 while (unlikely(!left && bytes)) {
 206                         iov++;
 207                         buf = iov->iov_base;
 208                         copy = min(bytes, iov->iov_len);
 209                         left = copyout(buf, from, copy);
 210                         copy -= left;
 211                         skip = copy;
 212                         from += copy;
 213                         bytes -= copy;
 214                 }
 215                 if (likely(!bytes)) {
 216                         kunmap_atomic(kaddr);
 217                         goto done;
 218                 }
 219                 offset = from - kaddr;
 220                 buf += copy;
 221                 kunmap_atomic(kaddr);
 222                 copy = min(bytes, iov->iov_len - skip);
 223         }
 224         /* Too bad - revert to non-atomic kmap */
 225
 226         kaddr = kmap(page);
 227         from = kaddr + offset;
 228         left = copyout(buf, from, copy);
 229         copy -= left;
 230         skip += copy;
 231         from += copy;
 232         bytes -= copy;
 233         while (unlikely(!left && bytes)) {
 234                 iov++;
 235                 buf = iov->iov_base;
 236                 copy = min(bytes, iov->iov_len);
 237                 left = copyout(buf, from, copy);
 238                 copy -= left;
 239                 skip = copy;
 240                 from += copy;
 241                 bytes -= copy;
 242         }
 243         kunmap(page);
 244
 245 done:
 246         if (skip == iov->iov_len) {
 247                 iov++;
 248                 skip = 0;
 249         }
 250         i->count -= wanted - bytes;
 251         i->nr_segs -= iov - i->iov;
 252         i->iov = iov;
 253         i->iov_offset = skip;
 254         return wanted - bytes;
 255 }
 256
 257 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
 258                          struct iov_iter *i)
 259 {
 260         size_t skip, copy, left, wanted;
 261         const struct iovec *iov;
 262         char __user *buf;
 263         void *kaddr, *to;
 264
 265         if (unlikely(bytes > i->count))
 266                 bytes = i->count;
 267
 268         if (unlikely(!bytes))
 269                 return 0;
 270
 271         might_fault();
 272         wanted = bytes;
 273         iov = i->iov;
 274         skip = i->iov_offset;
 275         buf = iov->iov_base + skip;
 276         copy = min(bytes, iov->iov_len - skip);
 277
 278         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_readable(buf, copy)) {
 279                 kaddr = kmap_atomic(page);
 280                 to = kaddr + offset;
 281
 282                 /* first chunk, usually the only one */
 283                 left = copyin(to, buf, copy);
 284                 copy -= left;
 285                 skip += copy;
 286                 to += copy;
 287                 bytes -= copy;
 288
 289                 while (unlikely(!left && bytes)) {
 290                         iov++;
 291                         buf = iov->iov_base;
 292                         copy = min(bytes, iov->iov_len);
 293                         left = copyin(to, buf, copy);
 294                         copy -= left;
 295                         skip = copy;
 296                         to += copy;
 297                         bytes -= copy;
 298                 }
 299                 if (likely(!bytes)) {
 300                         kunmap_atomic(kaddr);
 301                         goto done;
 302                 }
 303                 offset = to - kaddr;
 304                 buf += copy;
 305                 kunmap_atomic(kaddr);
 306                 copy = min(bytes, iov->iov_len - skip);
 307         }
 308         /* Too bad - revert to non-atomic kmap */
 309
 310         kaddr = kmap(page);
 311         to = kaddr + offset;
 312         left = copyin(to, buf, copy);
 313         copy -= left;
 314         skip += copy;
 315         to += copy;
 316         bytes -= copy;
 317         while (unlikely(!left && bytes)) {
 318                 iov++;
 319                 buf = iov->iov_base;
 320                 copy = min(bytes, iov->iov_len);
 321                 left = copyin(to, buf, copy);
 322                 copy -= left;
 323                 skip = copy;
 324                 to += copy;
 325                 bytes -= copy;
 326         }
 327         kunmap(page);
 328
 329 done:
 330         if (skip == iov->iov_len) {
 331                 iov++;
 332                 skip = 0;
 333         }
 334         i->count -= wanted - bytes;
 335         i->nr_segs -= iov - i->iov;
 336         i->iov = iov;
 337         i->iov_offset = skip;
 338         return wanted - bytes;
 339 }
 340
 341 #ifdef PIPE_PARANOIA
 342 static bool sanity(const struct iov_iter *i)
 343 {
 344         struct pipe_inode_info *pipe = i->pipe;
 345         unsigned int p_head = pipe->head;
 346         unsigned int p_tail = pipe->tail;
 347         unsigned int p_mask = pipe->ring_size - 1;
 348         unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
 349         unsigned int i_head = i->head;
 350         unsigned int idx;
 351
 352         if (i->iov_offset) {
 353                 struct pipe_buffer *p;
 354                 if (unlikely(p_occupancy == 0))
 355                         goto Bad;       // pipe must be non-empty
 356                 if (unlikely(i_head != p_head - 1))
 357                         goto Bad;       // must be at the last buffer...
 358
 359                 p = &pipe->bufs[i_head & p_mask];
 360                 if (unlikely(p->offset + p->len != i->iov_offset))
 361                         goto Bad;       // ... at the end of segment
 362         } else {
 363                 if (i_head != p_head)
 364                         goto Bad;       // must be right after the last buffer
 365         }
 366         return true;
 367 Bad:
 368         printk(KERN_ERR "idx = %d, offset = %zd\n", i_head, i->iov_offset);
 369         printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
 370                         p_head, p_tail, pipe->ring_size);
 371         for (idx = 0; idx < pipe->ring_size; idx++)
 372                 printk(KERN_ERR "[%p %p %d %d]\n",
 373                         pipe->bufs[idx].ops,
 374                         pipe->bufs[idx].page,
 375                         pipe->bufs[idx].offset,
 376                         pipe->bufs[idx].len);
 377         WARN_ON(1);
 378         return false;
 379 }
 380 #else
 381 #define sanity(i) true
 382 #endif
 383
 384 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
 385                          struct iov_iter *i)
 386 {
 387         struct pipe_inode_info *pipe = i->pipe;
 388         struct pipe_buffer *buf;
 389         unsigned int p_tail = pipe->tail;
 390         unsigned int p_mask = pipe->ring_size - 1;
 391         unsigned int i_head = i->head;
 392         size_t off;
 393
 394         if (unlikely(bytes > i->count))
 395                 bytes = i->count;
 396
 397         if (unlikely(!bytes))
 398                 return 0;
 399
 400         if (!sanity(i))
 401                 return 0;
 402
 403         off = i->iov_offset;
 404         buf = &pipe->bufs[i_head & p_mask];
 405         if (off) {
 406                 if (offset == off && buf->page == page) {
 407                         /* merge with the last one */
 408                         buf->len += bytes;
 409                         i->iov_offset += bytes;
 410                         goto out;
 411                 }
 412                 i_head++;
 413                 buf = &pipe->bufs[i_head & p_mask];
 414         }
 415         if (pipe_full(i_head, p_tail, pipe->max_usage))
 416                 return 0;
 417
 418         buf->ops = &page_cache_pipe_buf_ops;
 419         buf->flags = 0;
 420         get_page(page);
 421         buf->page = page;
 422         buf->offset = offset;
 423         buf->len = bytes;
 424
 425         pipe->head = i_head + 1;
 426         i->iov_offset = offset + bytes;
 427         i->head = i_head;
 428 out:
 429         i->count -= bytes;
 430         return bytes;
 431 }
 432
 433 /*
 434  * fault_in_iov_iter_readable - fault in iov iterator for reading
 435  * @i: iterator
 436  * @size: maximum length
 437  *
 438  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 439  * @size.  For each iovec, fault in each page that constitutes the iovec.
 440  *
 441  * Returns the number of bytes not faulted in (like copy_to_user() and
 442  * copy_from_user()).
 443  *
 444  * Always returns 0 for non-userspace iterators.
 445  */
 446 size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
 447 {
 448         if (iter_is_iovec(i)) {
 449                 size_t count = min(size, iov_iter_count(i));
 450                 const struct iovec *p;
 451                 size_t skip;
 452
 453                 size -= count;
 454                 for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
 455                         size_t len = min(count, p->iov_len - skip);
 456                         size_t ret;
 457
 458                         if (unlikely(!len))
 459                                 continue;
 460                         ret = fault_in_readable(p->iov_base + skip, len);
 461                         count -= len - ret;
 462                         if (ret)
 463                                 break;
 464                 }
 465                 return count + size;
 466         }
 467         return 0;
 468 }
 469 EXPORT_SYMBOL(fault_in_iov_iter_readable);
 470
 471 /*
 472  * fault_in_iov_iter_writeable - fault in iov iterator for writing
 473  * @i: iterator
 474  * @size: maximum length
 475  *
 476  * Faults in the iterator using get_user_pages(), i.e., without triggering
 477  * hardware page faults.  This is primarily useful when we already know that
 478  * some or all of the pages in @i aren't in memory.
 479  *
 480  * Returns the number of bytes not faulted in, like copy_to_user() and
 481  * copy_from_user().
 482  *
 483  * Always returns 0 for non-user-space iterators.
 484  */
 485 size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
 486 {
 487         if (iter_is_iovec(i)) {
 488                 size_t count = min(size, iov_iter_count(i));
 489                 const struct iovec *p;
 490                 size_t skip;
 491
 492                 size -= count;
 493                 for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
 494                         size_t len = min(count, p->iov_len - skip);
 495                         size_t ret;
 496
 497                         if (unlikely(!len))
 498                                 continue;
 499                         ret = fault_in_safe_writeable(p->iov_base + skip, len);
 500                         count -= len - ret;
 501                         if (ret)
 502                                 break;
 503                 }
 504                 return count + size;
 505         }
 506         return 0;
 507 }
 508 EXPORT_SYMBOL(fault_in_iov_iter_writeable);
 509
 510 void iov_iter_init(struct iov_iter *i, unsigned int direction,
 511                         const struct iovec *iov, unsigned long nr_segs,
 512                         size_t count)
 513 {
 514         WARN_ON(direction & ~(READ | WRITE));
 515         *i = (struct iov_iter) {
 516                 .iter_type = ITER_IOVEC,
 517                 .nofault = false,
 518                 .data_source = direction,
 519                 .iov = iov,
 520                 .nr_segs = nr_segs,
 521                 .iov_offset = 0,
 522                 .count = count
 523         };
 524 }
 525 EXPORT_SYMBOL(iov_iter_init);
 526
 527 static inline bool allocated(struct pipe_buffer *buf)
 528 {
 529         return buf->ops == &default_pipe_buf_ops;
 530 }
 531
 532 static inline void data_start(const struct iov_iter *i,
 533                               unsigned int *iter_headp, size_t *offp)
 534 {
 535         unsigned int p_mask = i->pipe->ring_size - 1;
 536         unsigned int iter_head = i->head;
 537         size_t off = i->iov_offset;
 538
 539         if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) ||
 540                     off == PAGE_SIZE)) {
 541                 iter_head++;
 542                 off = 0;
 543         }
 544         *iter_headp = iter_head;
 545         *offp = off;
 546 }
 547
 548 static size_t push_pipe(struct iov_iter *i, size_t size,
 549                         int *iter_headp, size_t *offp)
 550 {
 551         struct pipe_inode_info *pipe = i->pipe;
 552         unsigned int p_tail = pipe->tail;
 553         unsigned int p_mask = pipe->ring_size - 1;
 554         unsigned int iter_head;
 555         size_t off;
 556         ssize_t left;
 557
 558         if (unlikely(size > i->count))
 559                 size = i->count;
 560         if (unlikely(!size))
 561                 return 0;
 562
 563         left = size;
 564         data_start(i, &iter_head, &off);
 565         *iter_headp = iter_head;
 566         *offp = off;
 567         if (off) {
 568                 left -= PAGE_SIZE - off;
 569                 if (left <= 0) {
 570                         pipe->bufs[iter_head & p_mask].len += size;
 571                         return size;
 572                 }
 573                 pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
 574                 iter_head++;
 575         }
 576         while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
 577                 struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
 578                 struct page *page = alloc_page(GFP_USER);
 579                 if (!page)
 580                         break;
 581
 582                 buf->ops = &default_pipe_buf_ops;
 583                 buf->flags = 0;
 584                 buf->page = page;
 585                 buf->offset = 0;
 586                 buf->len = min_t(ssize_t, left, PAGE_SIZE);
 587                 left -= buf->len;
 588                 iter_head++;
 589                 pipe->head = iter_head;
 590
 591                 if (left == 0)
 592                         return size;
 593         }
 594         return size - left;
 595 }
 596
 597 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
 598                                 struct iov_iter *i)
 599 {
 600         struct pipe_inode_info *pipe = i->pipe;
 601         unsigned int p_mask = pipe->ring_size - 1;
 602         unsigned int i_head;
 603         size_t n, off;
 604
 605         if (!sanity(i))
 606                 return 0;
 607
 608         bytes = n = push_pipe(i, bytes, &i_head, &off);
 609         if (unlikely(!n))
 610                 return 0;
 611         do {
 612                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 613                 memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
 614                 i->head = i_head;
 615                 i->iov_offset = off + chunk;
 616                 n -= chunk;
 617                 addr += chunk;
 618                 off = 0;
 619                 i_head++;
 620         } while (n);
 621         i->count -= bytes;
 622         return bytes;
 623 }
 624
 625 static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
 626                               __wsum sum, size_t off)
 627 {
 628         __wsum next = csum_partial_copy_nocheck(from, to, len);
 629         return csum_block_add(sum, next, off);
 630 }
 631
 632 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
 633                                          struct iov_iter *i, __wsum *sump)
 634 {
 635         struct pipe_inode_info *pipe = i->pipe;
 636         unsigned int p_mask = pipe->ring_size - 1;
 637         __wsum sum = *sump;
 638         size_t off = 0;
 639         unsigned int i_head;
 640         size_t r;
 641
 642         if (!sanity(i))
 643                 return 0;
 644
 645         bytes = push_pipe(i, bytes, &i_head, &r);
 646         while (bytes) {
 647                 size_t chunk = min_t(size_t, bytes, PAGE_SIZE - r);
 648                 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
 649                 sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
 650                 kunmap_local(p);
 651                 i->head = i_head;
 652                 i->iov_offset = r + chunk;
 653                 bytes -= chunk;
 654                 off += chunk;
 655                 r = 0;
 656                 i_head++;
 657         }
 658         *sump = sum;
 659         i->count -= off;
 660         return off;
 661 }
 662
 663 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 664 {
 665         if (unlikely(iov_iter_is_pipe(i)))
 666                 return copy_pipe_to_iter(addr, bytes, i);
 667         if (iter_is_iovec(i))
 668                 might_fault();
 669         iterate_and_advance(i, bytes, base, len, off,
 670                 copyout(base, addr + off, len),
 671                 memcpy(base, addr + off, len)
 672         )
 673
 674         return bytes;
 675 }
 676 EXPORT_SYMBOL(_copy_to_iter);
 677
 678 #ifdef CONFIG_ARCH_HAS_COPY_MC
 679 static int copyout_mc(void __user *to, const void *from, size_t n)
 680 {
 681         if (access_ok(to, n)) {
 682                 instrument_copy_to_user(to, from, n);
 683                 n = copy_mc_to_user((__force void *) to, from, n);
 684         }
 685         return n;
 686 }
 687
 688 static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
 689                                 struct iov_iter *i)
 690 {
 691         struct pipe_inode_info *pipe = i->pipe;
 692         unsigned int p_mask = pipe->ring_size - 1;
 693         unsigned int i_head;
 694         unsigned int valid = pipe->head;
 695         size_t n, off, xfer = 0;
 696
 697         if (!sanity(i))
 698                 return 0;
 699
 700         n = push_pipe(i, bytes, &i_head, &off);
 701         while (n) {
 702                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 703                 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
 704                 unsigned long rem;
 705                 rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
 706                 chunk -= rem;
 707                 kunmap_local(p);
 708                 if (chunk) {
 709                         i->head = i_head;
 710                         i->iov_offset = off + chunk;
 711                         xfer += chunk;
 712                         valid = i_head + 1;
 713                 }
 714                 if (rem) {
 715                         pipe->bufs[i_head & p_mask].len -= rem;
 716                         pipe_discard_from(pipe, valid);
 717                         break;
 718                 }
 719                 n -= chunk;
 720                 off = 0;
 721                 i_head++;
 722         }
 723         i->count -= xfer;
 724         return xfer;
 725 }
 726
 727 /**
 728  * _copy_mc_to_iter - copy to iter with source memory error exception handling
 729  * @addr: source kernel address
 730  * @bytes: total transfer length
 731  * @i: destination iterator
 732  *
 733  * The pmem driver deploys this for the dax operation
 734  * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
 735  * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
 736  * successfully copied.
 737  *
 738  * The main differences between this and typical _copy_to_iter().
 739  *
 740  * * Typical tail/residue handling after a fault retries the copy
 741  *   byte-by-byte until the fault happens again. Re-triggering machine
 742  *   checks is potentially fatal so the implementation uses source
 743  *   alignment and poison alignment assumptions to avoid re-triggering
 744  *   hardware exceptions.
 745  *
 746  * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
 747  *   Compare to copy_to_iter() where only ITER_IOVEC attempts might return
 748  *   a short copy.
 749  *
 750  * Return: number of bytes copied (may be %0)
 751  */
 752 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 753 {
 754         if (unlikely(iov_iter_is_pipe(i)))
 755                 return copy_mc_pipe_to_iter(addr, bytes, i);
 756         if (iter_is_iovec(i))
 757                 might_fault();
 758         __iterate_and_advance(i, bytes, base, len, off,
 759                 copyout_mc(base, addr + off, len),
 760                 copy_mc_to_kernel(base, addr + off, len)
 761         )
 762
 763         return bytes;
 764 }
 765 EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
 766 #endif /* CONFIG_ARCH_HAS_COPY_MC */
 767
 768 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 769 {
 770         if (unlikely(iov_iter_is_pipe(i))) {
 771                 WARN_ON(1);
 772                 return 0;
 773         }
 774         if (iter_is_iovec(i))
 775                 might_fault();
 776         iterate_and_advance(i, bytes, base, len, off,
 777                 copyin(addr + off, base, len),
 778                 memcpy(addr + off, base, len)
 779         )
 780
 781         return bytes;
 782 }
 783 EXPORT_SYMBOL(_copy_from_iter);
 784
 785 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 786 {
 787         if (unlikely(iov_iter_is_pipe(i))) {
 788                 WARN_ON(1);
 789                 return 0;
 790         }
 791         iterate_and_advance(i, bytes, base, len, off,
 792                 __copy_from_user_inatomic_nocache(addr + off, base, len),
 793                 memcpy(addr + off, base, len)
 794         )
 795
 796         return bytes;
 797 }
 798 EXPORT_SYMBOL(_copy_from_iter_nocache);
 799
 800 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 801 /**
 802  * _copy_from_iter_flushcache - write destination through cpu cache
 803  * @addr: destination kernel address
 804  * @bytes: total transfer length
 805  * @i: source iterator
 806  *
 807  * The pmem driver arranges for filesystem-dax to use this facility via
 808  * dax_copy_from_iter() for ensuring that writes to persistent memory
 809  * are flushed through the CPU cache. It is differentiated from
 810  * _copy_from_iter_nocache() in that guarantees all data is flushed for
 811  * all iterator types. The _copy_from_iter_nocache() only attempts to
 812  * bypass the cache for the ITER_IOVEC case, and on some archs may use
 813  * instructions that strand dirty-data in the cache.
 814  *
 815  * Return: number of bytes copied (may be %0)
 816  */
 817 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 818 {
 819         if (unlikely(iov_iter_is_pipe(i))) {
 820                 WARN_ON(1);
 821                 return 0;
 822         }
 823         iterate_and_advance(i, bytes, base, len, off,
 824                 __copy_from_user_flushcache(addr + off, base, len),
 825                 memcpy_flushcache(addr + off, base, len)
 826         )
 827
 828         return bytes;
 829 }
 830 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 831 #endif
 832
 833 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 834 {
 835         struct page *head;
 836         size_t v = n + offset;
 837
 838         /*
 839          * The general case needs to access the page order in order
 840          * to compute the page size.
 841          * However, we mostly deal with order-0 pages and thus can
 842          * avoid a possible cache line miss for requests that fit all
 843          * page orders.
 844          */
 845         if (n <= v && v <= PAGE_SIZE)
 846                 return true;
 847
 848         head = compound_head(page);
 849         v += (page - head) << PAGE_SHIFT;
 850
 851         if (likely(n <= v && v <= (page_size(head))))
 852                 return true;
 853         WARN_ON(1);
 854         return false;
 855 }
 856
 857 static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 858                          struct iov_iter *i)
 859 {
 860         if (likely(iter_is_iovec(i)))
 861                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 862         if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
 863                 void *kaddr = kmap_local_page(page);
 864                 size_t wanted = _copy_to_iter(kaddr + offset, bytes, i);
 865                 kunmap_local(kaddr);
 866                 return wanted;
 867         }
 868         if (iov_iter_is_pipe(i))
 869                 return copy_page_to_iter_pipe(page, offset, bytes, i);
 870         if (unlikely(iov_iter_is_discard(i))) {
 871                 if (unlikely(i->count < bytes))
 872                         bytes = i->count;
 873                 i->count -= bytes;
 874                 return bytes;
 875         }
 876         WARN_ON(1);
 877         return 0;
 878 }
 879
 880 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 881                          struct iov_iter *i)
 882 {
 883         size_t res = 0;
 884         if (unlikely(!page_copy_sane(page, offset, bytes)))
 885                 return 0;
 886         page += offset / PAGE_SIZE; // first subpage
 887         offset %= PAGE_SIZE;
 888         while (1) {
 889                 size_t n = __copy_page_to_iter(page, offset,
 890                                 min(bytes, (size_t)PAGE_SIZE - offset), i);
 891                 res += n;
 892                 bytes -= n;
 893                 if (!bytes || !n)
 894                         break;
 895                 offset += n;
 896                 if (offset == PAGE_SIZE) {
 897                         page++;
 898                         offset = 0;
 899                 }
 900         }
 901         return res;
 902 }
 903 EXPORT_SYMBOL(copy_page_to_iter);
 904
 905 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 906                          struct iov_iter *i)
 907 {
 908         if (unlikely(!page_copy_sane(page, offset, bytes)))
 909                 return 0;
 910         if (likely(iter_is_iovec(i)))
 911                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 912         if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
 913                 void *kaddr = kmap_local_page(page);
 914                 size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
 915                 kunmap_local(kaddr);
 916                 return wanted;
 917         }
 918         WARN_ON(1);
 919         return 0;
 920 }
 921 EXPORT_SYMBOL(copy_page_from_iter);
 922
 923 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
 924 {
 925         struct pipe_inode_info *pipe = i->pipe;
 926         unsigned int p_mask = pipe->ring_size - 1;
 927         unsigned int i_head;
 928         size_t n, off;
 929
 930         if (!sanity(i))
 931                 return 0;
 932
 933         bytes = n = push_pipe(i, bytes, &i_head, &off);
 934         if (unlikely(!n))
 935                 return 0;
 936
 937         do {
 938                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 939                 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
 940                 memset(p + off, 0, chunk);
 941                 kunmap_local(p);
 942                 i->head = i_head;
 943                 i->iov_offset = off + chunk;
 944                 n -= chunk;
 945                 off = 0;
 946                 i_head++;
 947         } while (n);
 948         i->count -= bytes;
 949         return bytes;
 950 }
 951
 952 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 953 {
 954         if (unlikely(iov_iter_is_pipe(i)))
 955                 return pipe_zero(bytes, i);
 956         iterate_and_advance(i, bytes, base, len, count,
 957                 clear_user(base, len),
 958                 memset(base, 0, len)
 959         )
 960
 961         return bytes;
 962 }
 963 EXPORT_SYMBOL(iov_iter_zero);
 964
 965 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
 966                                   struct iov_iter *i)
 967 {
 968         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 969         if (unlikely(!page_copy_sane(page, offset, bytes))) {
 970                 kunmap_atomic(kaddr);
 971                 return 0;
 972         }
 973         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
 974                 kunmap_atomic(kaddr);
 975                 WARN_ON(1);
 976                 return 0;
 977         }
 978         iterate_and_advance(i, bytes, base, len, off,
 979                 copyin(p + off, base, len),
 980                 memcpy(p + off, base, len)
 981         )
 982         kunmap_atomic(kaddr);
 983         return bytes;
 984 }
 985 EXPORT_SYMBOL(copy_page_from_iter_atomic);
 986
 987 static inline void pipe_truncate(struct iov_iter *i)
 988 {
 989         struct pipe_inode_info *pipe = i->pipe;
 990         unsigned int p_tail = pipe->tail;
 991         unsigned int p_head = pipe->head;
 992         unsigned int p_mask = pipe->ring_size - 1;
 993
 994         if (!pipe_empty(p_head, p_tail)) {
 995                 struct pipe_buffer *buf;
 996                 unsigned int i_head = i->head;
 997                 size_t off = i->iov_offset;
 998
 999                 if (off) {
1000                         buf = &pipe->bufs[i_head & p_mask];
1001                         buf->len = off - buf->offset;
1002                         i_head++;
1003                 }
1004                 while (p_head != i_head) {
1005                         p_head--;
1006                         pipe_buf_release(pipe, &pipe->bufs[p_head & p_mask]);
1007                 }
1008
1009                 pipe->head = p_head;
1010         }
1011 }
1012
1013 static void pipe_advance(struct iov_iter *i, size_t size)
1014 {
1015         struct pipe_inode_info *pipe = i->pipe;
1016         if (size) {
1017                 struct pipe_buffer *buf;
1018                 unsigned int p_mask = pipe->ring_size - 1;
1019                 unsigned int i_head = i->head;
1020                 size_t off = i->iov_offset, left = size;
1021
1022                 if (off) /* make it relative to the beginning of buffer */
1023                         left += off - pipe->bufs[i_head & p_mask].offset;
1024                 while (1) {
1025                         buf = &pipe->bufs[i_head & p_mask];
1026                         if (left <= buf->len)
1027                                 break;
1028                         left -= buf->len;
1029                         i_head++;
1030                 }
1031                 i->head = i_head;
1032                 i->iov_offset = buf->offset + left;
1033         }
1034         i->count -= size;
1035         /* ... and discard everything past that point */
1036         pipe_truncate(i);
1037 }
1038
1039 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
1040 {
1041         struct bvec_iter bi;
1042
1043         bi.bi_size = i->count;
1044         bi.bi_bvec_done = i->iov_offset;
1045         bi.bi_idx = 0;
1046         bvec_iter_advance(i->bvec, &bi, size);
1047
1048         i->bvec += bi.bi_idx;
1049         i->nr_segs -= bi.bi_idx;
1050         i->count = bi.bi_size;
1051         i->iov_offset = bi.bi_bvec_done;
1052 }
1053
1054 static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
1055 {
1056         const struct iovec *iov, *end;
1057
1058         if (!i->count)
1059                 return;
1060         i->count -= size;
1061
1062         size += i->iov_offset; // from beginning of current segment
1063         for (iov = i->iov, end = iov + i->nr_segs; iov < end; iov++) {
1064                 if (likely(size < iov->iov_len))
1065                         break;
1066                 size -= iov->iov_len;
1067         }
1068         i->iov_offset = size;
1069         i->nr_segs -= iov - i->iov;
1070         i->iov = iov;
1071 }
1072
1073 void iov_iter_advance(struct iov_iter *i, size_t size)
1074 {
1075         if (unlikely(i->count < size))
1076                 size = i->count;
1077         if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
1078                 /* iovec and kvec have identical layouts */
1079                 iov_iter_iovec_advance(i, size);
1080         } else if (iov_iter_is_bvec(i)) {
1081                 iov_iter_bvec_advance(i, size);
1082         } else if (iov_iter_is_pipe(i)) {
1083                 pipe_advance(i, size);
1084         } else if (unlikely(iov_iter_is_xarray(i))) {
1085                 i->iov_offset += size;
1086                 i->count -= size;
1087         } else if (iov_iter_is_discard(i)) {
1088                 i->count -= size;
1089         }
1090 }
1091 EXPORT_SYMBOL(iov_iter_advance);
1092
1093 void iov_iter_revert(struct iov_iter *i, size_t unroll)
1094 {
1095         if (!unroll)
1096                 return;
1097         if (WARN_ON(unroll > MAX_RW_COUNT))
1098                 return;
1099         i->count += unroll;
1100         if (unlikely(iov_iter_is_pipe(i))) {
1101                 struct pipe_inode_info *pipe = i->pipe;
1102                 unsigned int p_mask = pipe->ring_size - 1;
1103                 unsigned int i_head = i->head;
1104                 size_t off = i->iov_offset;
1105                 while (1) {
1106                         struct pipe_buffer *b = &pipe->bufs[i_head & p_mask];
1107                         size_t n = off - b->offset;
1108                         if (unroll < n) {
1109                                 off -= unroll;
1110                                 break;
1111                         }
1112                         unroll -= n;
1113                         if (!unroll && i_head == i->start_head) {
1114                                 off = 0;
1115                                 break;
1116                         }
1117                         i_head--;
1118                         b = &pipe->bufs[i_head & p_mask];
1119                         off = b->offset + b->len;
1120                 }
1121                 i->iov_offset = off;
1122                 i->head = i_head;
1123                 pipe_truncate(i);
1124                 return;
1125         }
1126         if (unlikely(iov_iter_is_discard(i)))
1127                 return;
1128         if (unroll <= i->iov_offset) {
1129                 i->iov_offset -= unroll;
1130                 return;
1131         }
1132         unroll -= i->iov_offset;
1133         if (iov_iter_is_xarray(i)) {
1134                 BUG(); /* We should never go beyond the start of the specified
1135                         * range since we might then be straying into pages that
1136                         * aren't pinned.
1137                         */
1138         } else if (iov_iter_is_bvec(i)) {
1139                 const struct bio_vec *bvec = i->bvec;
1140                 while (1) {
1141                         size_t n = (--bvec)->bv_len;
1142                         i->nr_segs++;
1143                         if (unroll <= n) {
1144                                 i->bvec = bvec;
1145                                 i->iov_offset = n - unroll;
1146                                 return;
1147                         }
1148                         unroll -= n;
1149                 }
1150         } else { /* same logics for iovec and kvec */
1151                 const struct iovec *iov = i->iov;
1152                 while (1) {
1153                         size_t n = (--iov)->iov_len;
1154                         i->nr_segs++;
1155                         if (unroll <= n) {
1156                                 i->iov = iov;
1157                                 i->iov_offset = n - unroll;
1158                                 return;
1159                         }
1160                         unroll -= n;
1161                 }
1162         }
1163 }
1164 EXPORT_SYMBOL(iov_iter_revert);
1165
1166 /*
1167  * Return the count of just the current iov_iter segment.
1168  */
1169 size_t iov_iter_single_seg_count(const struct iov_iter *i)
1170 {
1171         if (i->nr_segs > 1) {
1172                 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1173                         return min(i->count, i->iov->iov_len - i->iov_offset);
1174                 if (iov_iter_is_bvec(i))
1175                         return min(i->count, i->bvec->bv_len - i->iov_offset);
1176         }
1177         return i->count;
1178 }
1179 EXPORT_SYMBOL(iov_iter_single_seg_count);
1180
1181 void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
1182                         const struct kvec *kvec, unsigned long nr_segs,
1183                         size_t count)
1184 {
1185         WARN_ON(direction & ~(READ | WRITE));
1186         *i = (struct iov_iter){
1187                 .iter_type = ITER_KVEC,
1188                 .data_source = direction,
1189                 .kvec = kvec,
1190                 .nr_segs = nr_segs,
1191                 .iov_offset = 0,
1192                 .count = count
1193         };
1194 }
1195 EXPORT_SYMBOL(iov_iter_kvec);
1196
1197 void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
1198                         const struct bio_vec *bvec, unsigned long nr_segs,
1199                         size_t count)
1200 {
1201         WARN_ON(direction & ~(READ | WRITE));
1202         *i = (struct iov_iter){
1203                 .iter_type = ITER_BVEC,
1204                 .data_source = direction,
1205                 .bvec = bvec,
1206                 .nr_segs = nr_segs,
1207                 .iov_offset = 0,
1208                 .count = count
1209         };
1210 }
1211 EXPORT_SYMBOL(iov_iter_bvec);
1212
1213 void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
1214                         struct pipe_inode_info *pipe,
1215                         size_t count)
1216 {
1217         BUG_ON(direction != READ);
1218         WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
1219         *i = (struct iov_iter){
1220                 .iter_type = ITER_PIPE,
1221                 .data_source = false,
1222                 .pipe = pipe,
1223                 .head = pipe->head,
1224                 .start_head = pipe->head,
1225                 .iov_offset = 0,
1226                 .count = count
1227         };
1228 }
1229 EXPORT_SYMBOL(iov_iter_pipe);
1230
1231 /**
1232  * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
1233  * @i: The iterator to initialise.
1234  * @direction: The direction of the transfer.
1235  * @xarray: The xarray to access.
1236  * @start: The start file position.
1237  * @count: The size of the I/O buffer in bytes.
1238  *
1239  * Set up an I/O iterator to either draw data out of the pages attached to an
1240  * inode or to inject data into those pages.  The pages *must* be prevented
1241  * from evaporation, either by taking a ref on them or locking them by the
1242  * caller.
1243  */
1244 void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
1245                      struct xarray *xarray, loff_t start, size_t count)
1246 {
1247         BUG_ON(direction & ~1);
1248         *i = (struct iov_iter) {
1249                 .iter_type = ITER_XARRAY,
1250                 .data_source = direction,
1251                 .xarray = xarray,
1252                 .xarray_start = start,
1253                 .count = count,
1254                 .iov_offset = 0
1255         };
1256 }
1257 EXPORT_SYMBOL(iov_iter_xarray);
1258
1259 /**
1260  * iov_iter_discard - Initialise an I/O iterator that discards data
1261  * @i: The iterator to initialise.
1262  * @direction: The direction of the transfer.
1263  * @count: The size of the I/O buffer in bytes.
1264  *
1265  * Set up an I/O iterator that just discards everything that's written to it.
1266  * It's only available as a READ iterator.
1267  */
1268 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
1269 {
1270         BUG_ON(direction != READ);
1271         *i = (struct iov_iter){
1272                 .iter_type = ITER_DISCARD,
1273                 .data_source = false,
1274                 .count = count,
1275                 .iov_offset = 0
1276         };
1277 }
1278 EXPORT_SYMBOL(iov_iter_discard);
1279
1280 static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
1281 {
1282         unsigned long res = 0;
1283         size_t size = i->count;
1284         size_t skip = i->iov_offset;
1285         unsigned k;
1286
1287         for (k = 0; k < i->nr_segs; k++, skip = 0) {
1288                 size_t len = i->iov[k].iov_len - skip;
1289                 if (len) {
1290                         res |= (unsigned long)i->iov[k].iov_base + skip;
1291                         if (len > size)
1292                                 len = size;
1293                         res |= len;
1294                         size -= len;
1295                         if (!size)
1296                                 break;
1297                 }
1298         }
1299         return res;
1300 }
1301
1302 static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
1303 {
1304         unsigned res = 0;
1305         size_t size = i->count;
1306         unsigned skip = i->iov_offset;
1307         unsigned k;
1308
1309         for (k = 0; k < i->nr_segs; k++, skip = 0) {
1310                 size_t len = i->bvec[k].bv_len - skip;
1311                 res |= (unsigned long)i->bvec[k].bv_offset + skip;
1312                 if (len > size)
1313                         len = size;
1314                 res |= len;
1315                 size -= len;
1316                 if (!size)
1317                         break;
1318         }
1319         return res;
1320 }
1321
1322 unsigned long iov_iter_alignment(const struct iov_iter *i)
1323 {
1324         /* iovec and kvec have identical layouts */
1325         if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1326                 return iov_iter_alignment_iovec(i);
1327
1328         if (iov_iter_is_bvec(i))
1329                 return iov_iter_alignment_bvec(i);
1330
1331         if (iov_iter_is_pipe(i)) {
1332                 unsigned int p_mask = i->pipe->ring_size - 1;
1333                 size_t size = i->count;
1334
1335                 if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask]))
1336                         return size | i->iov_offset;
1337                 return size;
1338         }
1339
1340         if (iov_iter_is_xarray(i))
1341                 return (i->xarray_start + i->iov_offset) | i->count;
1342
1343         return 0;
1344 }
1345 EXPORT_SYMBOL(iov_iter_alignment);
1346
1347 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
1348 {
1349         unsigned long res = 0;
1350         unsigned long v = 0;
1351         size_t size = i->count;
1352         unsigned k;
1353
1354         if (WARN_ON(!iter_is_iovec(i)))
1355                 return ~0U;
1356
1357         for (k = 0; k < i->nr_segs; k++) {
1358                 if (i->iov[k].iov_len) {
1359                         unsigned long base = (unsigned long)i->iov[k].iov_base;
1360                         if (v) // if not the first one
1361                                 res |= base | v; // this start | previous end
1362                         v = base + i->iov[k].iov_len;
1363                         if (size <= i->iov[k].iov_len)
1364                                 break;
1365                         size -= i->iov[k].iov_len;
1366                 }
1367         }
1368         return res;
1369 }
1370 EXPORT_SYMBOL(iov_iter_gap_alignment);
1371
1372 static inline ssize_t __pipe_get_pages(struct iov_iter *i,
1373                                 size_t maxsize,
1374                                 struct page **pages,
1375                                 int iter_head,
1376                                 size_t *start)
1377 {
1378         struct pipe_inode_info *pipe = i->pipe;
1379         unsigned int p_mask = pipe->ring_size - 1;
1380         ssize_t n = push_pipe(i, maxsize, &iter_head, start);
1381         if (!n)
1382                 return -EFAULT;
1383
1384         maxsize = n;
1385         n += *start;
1386         while (n > 0) {
1387                 get_page(*pages++ = pipe->bufs[iter_head & p_mask].page);
1388                 iter_head++;
1389                 n -= PAGE_SIZE;
1390         }
1391
1392         return maxsize;
1393 }
1394
1395 static ssize_t pipe_get_pages(struct iov_iter *i,
1396                    struct page **pages, size_t maxsize, unsigned maxpages,
1397                    size_t *start)
1398 {
1399         unsigned int iter_head, npages;
1400         size_t capacity;
1401
1402         if (!sanity(i))
1403                 return -EFAULT;
1404
1405         data_start(i, &iter_head, start);
1406         /* Amount of free space: some of this one + all after this one */
1407         npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1408         capacity = min(npages, maxpages) * PAGE_SIZE - *start;
1409
1410         return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
1411 }
1412
1413 static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
1414                                           pgoff_t index, unsigned int nr_pages)
1415 {
1416         XA_STATE(xas, xa, index);
1417         struct page *page;
1418         unsigned int ret = 0;
1419
1420         rcu_read_lock();
1421         for (page = xas_load(&xas); page; page = xas_next(&xas)) {
1422                 if (xas_retry(&xas, page))
1423                         continue;
1424
1425                 /* Has the page moved or been split? */
1426                 if (unlikely(page != xas_reload(&xas))) {
1427                         xas_reset(&xas);
1428                         continue;
1429                 }
1430
1431                 pages[ret] = find_subpage(page, xas.xa_index);
1432                 get_page(pages[ret]);
1433                 if (++ret == nr_pages)
1434                         break;
1435         }
1436         rcu_read_unlock();
1437         return ret;
1438 }
1439
1440 static ssize_t iter_xarray_get_pages(struct iov_iter *i,
1441                                      struct page **pages, size_t maxsize,
1442                                      unsigned maxpages, size_t *_start_offset)
1443 {
1444         unsigned nr, offset;
1445         pgoff_t index, count;
1446         size_t size = maxsize;
1447         loff_t pos;
1448
1449         if (!size || !maxpages)
1450                 return 0;
1451
1452         pos = i->xarray_start + i->iov_offset;
1453         index = pos >> PAGE_SHIFT;
1454         offset = pos & ~PAGE_MASK;
1455         *_start_offset = offset;
1456
1457         count = 1;
1458         if (size > PAGE_SIZE - offset) {
1459                 size -= PAGE_SIZE - offset;
1460                 count += size >> PAGE_SHIFT;
1461                 size &= ~PAGE_MASK;
1462                 if (size)
1463                         count++;
1464         }
1465
1466         if (count > maxpages)
1467                 count = maxpages;
1468
1469         nr = iter_xarray_populate_pages(pages, i->xarray, index, count);
1470         if (nr == 0)
1471                 return 0;
1472
1473         return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1474 }
1475
1476 /* must be done on non-empty ITER_IOVEC one */
1477 static unsigned long first_iovec_segment(const struct iov_iter *i,
1478                                          size_t *size, size_t *start,
1479                                          size_t maxsize, unsigned maxpages)
1480 {
1481         size_t skip;
1482         long k;
1483
1484         for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
1485                 unsigned long addr = (unsigned long)i->iov[k].iov_base + skip;
1486                 size_t len = i->iov[k].iov_len - skip;
1487
1488                 if (unlikely(!len))
1489                         continue;
1490                 if (len > maxsize)
1491                         len = maxsize;
1492                 len += (*start = addr % PAGE_SIZE);
1493                 if (len > maxpages * PAGE_SIZE)
1494                         len = maxpages * PAGE_SIZE;
1495                 *size = len;
1496                 return addr & PAGE_MASK;
1497         }
1498         BUG(); // if it had been empty, we wouldn't get called
1499 }
1500
1501 /* must be done on non-empty ITER_BVEC one */
1502 static struct page *first_bvec_segment(const struct iov_iter *i,
1503                                        size_t *size, size_t *start,
1504                                        size_t maxsize, unsigned maxpages)
1505 {
1506         struct page *page;
1507         size_t skip = i->iov_offset, len;
1508
1509         len = i->bvec->bv_len - skip;
1510         if (len > maxsize)
1511                 len = maxsize;
1512         skip += i->bvec->bv_offset;
1513         page = i->bvec->bv_page + skip / PAGE_SIZE;
1514         len += (*start = skip % PAGE_SIZE);
1515         if (len > maxpages * PAGE_SIZE)
1516                 len = maxpages * PAGE_SIZE;
1517         *size = len;
1518         return page;
1519 }
1520
1521 ssize_t iov_iter_get_pages(struct iov_iter *i,
1522                    struct page **pages, size_t maxsize, unsigned maxpages,
1523                    size_t *start)
1524 {
1525         size_t len;
1526         int n, res;
1527
1528         if (maxsize > i->count)
1529                 maxsize = i->count;
1530         if (!maxsize)
1531                 return 0;
1532
1533         if (likely(iter_is_iovec(i))) {
1534                 unsigned int gup_flags = 0;
1535                 unsigned long addr;
1536
1537                 if (iov_iter_rw(i) != WRITE)
1538                         gup_flags |= FOLL_WRITE;
1539                 if (i->nofault)
1540                         gup_flags |= FOLL_NOFAULT;
1541
1542                 addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
1543                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1544                 res = get_user_pages_fast(addr, n, gup_flags, pages);
1545                 if (unlikely(res <= 0))
1546                         return res;
1547                 return (res == n ? len : res * PAGE_SIZE) - *start;
1548         }
1549         if (iov_iter_is_bvec(i)) {
1550                 struct page *page;
1551
1552                 page = first_bvec_segment(i, &len, start, maxsize, maxpages);
1553                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1554                 while (n--)
1555                         get_page(*pages++ = page++);
1556                 return len - *start;
1557         }
1558         if (iov_iter_is_pipe(i))
1559                 return pipe_get_pages(i, pages, maxsize, maxpages, start);
1560         if (iov_iter_is_xarray(i))
1561                 return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
1562         return -EFAULT;
1563 }
1564 EXPORT_SYMBOL(iov_iter_get_pages);
1565
1566 static struct page **get_pages_array(size_t n)
1567 {
1568         return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
1569 }
1570
1571 static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
1572                    struct page ***pages, size_t maxsize,
1573                    size_t *start)
1574 {
1575         struct page **p;
1576         unsigned int iter_head, npages;
1577         ssize_t n;
1578
1579         if (!sanity(i))
1580                 return -EFAULT;
1581
1582         data_start(i, &iter_head, start);
1583         /* Amount of free space: some of this one + all after this one */
1584         npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1585         n = npages * PAGE_SIZE - *start;
1586         if (maxsize > n)
1587                 maxsize = n;
1588         else
1589                 npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
1590         p = get_pages_array(npages);
1591         if (!p)
1592                 return -ENOMEM;
1593         n = __pipe_get_pages(i, maxsize, p, iter_head, start);
1594         if (n > 0)
1595                 *pages = p;
1596         else
1597                 kvfree(p);
1598         return n;
1599 }
1600
1601 static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
1602                                            struct page ***pages, size_t maxsize,
1603                                            size_t *_start_offset)
1604 {
1605         struct page **p;
1606         unsigned nr, offset;
1607         pgoff_t index, count;
1608         size_t size = maxsize;
1609         loff_t pos;
1610
1611         if (!size)
1612                 return 0;
1613
1614         pos = i->xarray_start + i->iov_offset;
1615         index = pos >> PAGE_SHIFT;
1616         offset = pos & ~PAGE_MASK;
1617         *_start_offset = offset;
1618
1619         count = 1;
1620         if (size > PAGE_SIZE - offset) {
1621                 size -= PAGE_SIZE - offset;
1622                 count += size >> PAGE_SHIFT;
1623                 size &= ~PAGE_MASK;
1624                 if (size)
1625                         count++;
1626         }
1627
1628         p = get_pages_array(count);
1629         if (!p)
1630                 return -ENOMEM;
1631         *pages = p;
1632
1633         nr = iter_xarray_populate_pages(p, i->xarray, index, count);
1634         if (nr == 0)
1635                 return 0;
1636
1637         return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1638 }
1639
1640 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
1641                    struct page ***pages, size_t maxsize,
1642                    size_t *start)
1643 {
1644         struct page **p;
1645         size_t len;
1646         int n, res;
1647
1648         if (maxsize > i->count)
1649                 maxsize = i->count;
1650         if (!maxsize)
1651                 return 0;
1652
1653         if (likely(iter_is_iovec(i))) {
1654                 unsigned int gup_flags = 0;
1655                 unsigned long addr;
1656
1657                 if (iov_iter_rw(i) != WRITE)
1658                         gup_flags |= FOLL_WRITE;
1659                 if (i->nofault)
1660                         gup_flags |= FOLL_NOFAULT;
1661
1662                 addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
1663                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1664                 p = get_pages_array(n);
1665                 if (!p)
1666                         return -ENOMEM;
1667                 res = get_user_pages_fast(addr, n, gup_flags, p);
1668                 if (unlikely(res <= 0)) {
1669                         kvfree(p);
1670                         *pages = NULL;
1671                         return res;
1672                 }
1673                 *pages = p;
1674                 return (res == n ? len : res * PAGE_SIZE) - *start;
1675         }
1676         if (iov_iter_is_bvec(i)) {
1677                 struct page *page;
1678
1679                 page = first_bvec_segment(i, &len, start, maxsize, ~0U);
1680                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1681                 *pages = p = get_pages_array(n);
1682                 if (!p)
1683                         return -ENOMEM;
1684                 while (n--)
1685                         get_page(*p++ = page++);
1686                 return len - *start;
1687         }
1688         if (iov_iter_is_pipe(i))
1689                 return pipe_get_pages_alloc(i, pages, maxsize, start);
1690         if (iov_iter_is_xarray(i))
1691                 return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
1692         return -EFAULT;
1693 }
1694 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
1695
1696 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1697                                struct iov_iter *i)
1698 {
1699         __wsum sum, next;
1700         sum = *csum;
1701         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1702                 WARN_ON(1);
1703                 return 0;
1704         }
1705         iterate_and_advance(i, bytes, base, len, off, ({
1706                 next = csum_and_copy_from_user(base, addr + off, len);
1707                 sum = csum_block_add(sum, next, off);
1708                 next ? 0 : len;
1709         }), ({
1710                 sum = csum_and_memcpy(addr + off, base, len, sum, off);
1711         })
1712         )
1713         *csum = sum;
1714         return bytes;
1715 }
1716 EXPORT_SYMBOL(csum_and_copy_from_iter);
1717
1718 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
1719                              struct iov_iter *i)
1720 {
1721         struct csum_state *csstate = _csstate;
1722         __wsum sum, next;
1723
1724         if (unlikely(iov_iter_is_discard(i))) {
1725                 WARN_ON(1);     /* for now */
1726                 return 0;
1727         }
1728
1729         sum = csum_shift(csstate->csum, csstate->off);
1730         if (unlikely(iov_iter_is_pipe(i)))
1731                 bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
1732         else iterate_and_advance(i, bytes, base, len, off, ({
1733                 next = csum_and_copy_to_user(addr + off, base, len);
1734                 sum = csum_block_add(sum, next, off);
1735                 next ? 0 : len;
1736         }), ({
1737                 sum = csum_and_memcpy(base, addr + off, len, sum, off);
1738         })
1739         )
1740         csstate->csum = csum_shift(sum, csstate->off);
1741         csstate->off += bytes;
1742         return bytes;
1743 }
1744 EXPORT_SYMBOL(csum_and_copy_to_iter);
1745
1746 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
1747                 struct iov_iter *i)
1748 {
1749 #ifdef CONFIG_CRYPTO_HASH
1750         struct ahash_request *hash = hashp;
1751         struct scatterlist sg;
1752         size_t copied;
1753
1754         copied = copy_to_iter(addr, bytes, i);
1755         sg_init_one(&sg, addr, copied);
1756         ahash_request_set_crypt(hash, &sg, NULL, copied);
1757         crypto_ahash_update(hash);
1758         return copied;
1759 #else
1760         return 0;
1761 #endif
1762 }
1763 EXPORT_SYMBOL(hash_and_copy_to_iter);
1764
1765 static int iov_npages(const struct iov_iter *i, int maxpages)
1766 {
1767         size_t skip = i->iov_offset, size = i->count;
1768         const struct iovec *p;
1769         int npages = 0;
1770
1771         for (p = i->iov; size; skip = 0, p++) {
1772                 unsigned offs = offset_in_page(p->iov_base + skip);
1773                 size_t len = min(p->iov_len - skip, size);
1774
1775                 if (len) {
1776                         size -= len;
1777                         npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1778                         if (unlikely(npages > maxpages))
1779                                 return maxpages;
1780                 }
1781         }
1782         return npages;
1783 }
1784
1785 static int bvec_npages(const struct iov_iter *i, int maxpages)
1786 {
1787         size_t skip = i->iov_offset, size = i->count;
1788         const struct bio_vec *p;
1789         int npages = 0;
1790
1791         for (p = i->bvec; size; skip = 0, p++) {
1792                 unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
1793                 size_t len = min(p->bv_len - skip, size);
1794
1795                 size -= len;
1796                 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1797                 if (unlikely(npages > maxpages))
1798                         return maxpages;
1799         }
1800         return npages;
1801 }
1802
1803 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1804 {
1805         if (unlikely(!i->count))
1806                 return 0;
1807         /* iovec and kvec have identical layouts */
1808         if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1809                 return iov_npages(i, maxpages);
1810         if (iov_iter_is_bvec(i))
1811                 return bvec_npages(i, maxpages);
1812         if (iov_iter_is_pipe(i)) {
1813                 unsigned int iter_head;
1814                 int npages;
1815                 size_t off;
1816
1817                 if (!sanity(i))
1818                         return 0;
1819
1820                 data_start(i, &iter_head, &off);
1821                 /* some of this one + all after this one */
1822                 npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1823                 return min(npages, maxpages);
1824         }
1825         if (iov_iter_is_xarray(i)) {
1826                 unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
1827                 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1828                 return min(npages, maxpages);
1829         }
1830         return 0;
1831 }
1832 EXPORT_SYMBOL(iov_iter_npages);
1833
1834 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1835 {
1836         *new = *old;
1837         if (unlikely(iov_iter_is_pipe(new))) {
1838                 WARN_ON(1);
1839                 return NULL;
1840         }
1841         if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new)))
1842                 return NULL;
1843         if (iov_iter_is_bvec(new))
1844                 return new->bvec = kmemdup(new->bvec,
1845                                     new->nr_segs * sizeof(struct bio_vec),
1846                                     flags);
1847         else
1848                 /* iovec and kvec have identical layout */
1849                 return new->iov = kmemdup(new->iov,
1850                                    new->nr_segs * sizeof(struct iovec),
1851                                    flags);
1852 }
1853 EXPORT_SYMBOL(dup_iter);
1854
1855 static int copy_compat_iovec_from_user(struct iovec *iov,
1856                 const struct iovec __user *uvec, unsigned long nr_segs)
1857 {
1858         const struct compat_iovec __user *uiov =
1859                 (const struct compat_iovec __user *)uvec;
1860         int ret = -EFAULT, i;
1861
1862         if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1863                 return -EFAULT;
1864
1865         for (i = 0; i < nr_segs; i++) {
1866                 compat_uptr_t buf;
1867                 compat_ssize_t len;
1868
1869                 unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
1870                 unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
1871
1872                 /* check for compat_size_t not fitting in compat_ssize_t .. */
1873                 if (len < 0) {
1874                         ret = -EINVAL;
1875                         goto uaccess_end;
1876                 }
1877                 iov[i].iov_base = compat_ptr(buf);
1878                 iov[i].iov_len = len;
1879         }
1880
1881         ret = 0;
1882 uaccess_end:
1883         user_access_end();
1884         return ret;
1885 }
1886
1887 static int copy_iovec_from_user(struct iovec *iov,
1888                 const struct iovec __user *uvec, unsigned long nr_segs)
1889 {
1890         unsigned long seg;
1891
1892         if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
1893                 return -EFAULT;
1894         for (seg = 0; seg < nr_segs; seg++) {
1895                 if ((ssize_t)iov[seg].iov_len < 0)
1896                         return -EINVAL;
1897         }
1898
1899         return 0;
1900 }
1901
1902 struct iovec *iovec_from_user(const struct iovec __user *uvec,
1903                 unsigned long nr_segs, unsigned long fast_segs,
1904                 struct iovec *fast_iov, bool compat)
1905 {
1906         struct iovec *iov = fast_iov;
1907         int ret;
1908
1909         /*
1910          * SuS says "The readv() function *may* fail if the iovcnt argument was
1911          * less than or equal to 0, or greater than {IOV_MAX}.  Linux has
1912          * traditionally returned zero for zero segments, so...
1913          */
1914         if (nr_segs == 0)
1915                 return iov;
1916         if (nr_segs > UIO_MAXIOV)
1917                 return ERR_PTR(-EINVAL);
1918         if (nr_segs > fast_segs) {
1919                 iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
1920                 if (!iov)
1921                         return ERR_PTR(-ENOMEM);
1922         }
1923
1924         if (compat)
1925                 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
1926         else
1927                 ret = copy_iovec_from_user(iov, uvec, nr_segs);
1928         if (ret) {
1929                 if (iov != fast_iov)
1930                         kfree(iov);
1931                 return ERR_PTR(ret);
1932         }
1933
1934         return iov;
1935 }
1936
1937 ssize_t __import_iovec(int type, const struct iovec __user *uvec,
1938                  unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
1939                  struct iov_iter *i, bool compat)
1940 {
1941         ssize_t total_len = 0;
1942         unsigned long seg;
1943         struct iovec *iov;
1944
1945         iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
1946         if (IS_ERR(iov)) {
1947                 *iovp = NULL;
1948                 return PTR_ERR(iov);
1949         }
1950
1951         /*
1952          * According to the Single Unix Specification we should return EINVAL if
1953          * an element length is < 0 when cast to ssize_t or if the total length
1954          * would overflow the ssize_t return value of the system call.
1955          *
1956          * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
1957          * overflow case.
1958          */
1959         for (seg = 0; seg < nr_segs; seg++) {
1960                 ssize_t len = (ssize_t)iov[seg].iov_len;
1961
1962                 if (!access_ok(iov[seg].iov_base, len)) {
1963                         if (iov != *iovp)
1964                                 kfree(iov);
1965                         *iovp = NULL;
1966                         return -EFAULT;
1967                 }
1968
1969                 if (len > MAX_RW_COUNT - total_len) {
1970                         len = MAX_RW_COUNT - total_len;
1971                         iov[seg].iov_len = len;
1972                 }
1973                 total_len += len;
1974         }
1975
1976         iov_iter_init(i, type, iov, nr_segs, total_len);
1977         if (iov == *iovp)
1978                 *iovp = NULL;
1979         else
1980                 *iovp = iov;
1981         return total_len;
1982 }
1983
1984 /**
1985  * import_iovec() - Copy an array of &struct iovec from userspace
1986  *     into the kernel, check that it is valid, and initialize a new
1987  *     &struct iov_iter iterator to access it.
1988  *
1989  * @type: One of %READ or %WRITE.
1990  * @uvec: Pointer to the userspace array.
1991  * @nr_segs: Number of elements in userspace array.
1992  * @fast_segs: Number of elements in @iov.
1993  * @iovp: (input and output parameter) Pointer to pointer to (usually small
1994  *     on-stack) kernel array.
1995  * @i: Pointer to iterator that will be initialized on success.
1996  *
1997  * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1998  * then this function places %NULL in *@iov on return. Otherwise, a new
1999  * array will be allocated and the result placed in *@iov. This means that
2000  * the caller may call kfree() on *@iov regardless of whether the small
2001  * on-stack array was used or not (and regardless of whether this function
2002  * returns an error or not).
2003  *
2004  * Return: Negative error code on error, bytes imported on success
2005  */
2006 ssize_t import_iovec(int type, const struct iovec __user *uvec,
2007                  unsigned nr_segs, unsigned fast_segs,
2008                  struct iovec **iovp, struct iov_iter *i)
2009 {
2010         return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
2011                               in_compat_syscall());
2012 }
2013 EXPORT_SYMBOL(import_iovec);
2014
2015 int import_single_range(int rw, void __user *buf, size_t len,
2016                  struct iovec *iov, struct iov_iter *i)
2017 {
2018         if (len > MAX_RW_COUNT)
2019                 len = MAX_RW_COUNT;
2020         if (unlikely(!access_ok(buf, len)))
2021                 return -EFAULT;
2022
2023         iov->iov_base = buf;
2024         iov->iov_len = len;
2025         iov_iter_init(i, rw, iov, 1, len);
2026         return 0;
2027 }
2028 EXPORT_SYMBOL(import_single_range);
2029
2030 /**
2031  * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
2032  *     iov_iter_save_state() was called.
2033  *
2034  * @i: &struct iov_iter to restore
2035  * @state: state to restore from
2036  *
2037  * Used after iov_iter_save_state() to bring restore @i, if operations may
2038  * have advanced it.
2039  *
2040  * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
2041  */
2042 void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
2043 {
2044         if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
2045                          !iov_iter_is_kvec(i))
2046                 return;
2047         i->iov_offset = state->iov_offset;
2048         i->count = state->count;
2049         /*
2050          * For the *vec iters, nr_segs + iov is constant - if we increment
2051          * the vec, then we also decrement the nr_segs count. Hence we don't
2052          * need to track both of these, just one is enough and we can deduct
2053          * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
2054          * size, so we can just increment the iov pointer as they are unionzed.
2055          * ITER_BVEC _may_ be the same size on some archs, but on others it is
2056          * not. Be safe and handle it separately.
2057          */
2058         BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
2059         if (iov_iter_is_bvec(i))
2060                 i->bvec -= state->nr_segs - i->nr_segs;
2061         else
2062                 i->iov -= state->nr_segs - i->nr_segs;
2063         i->nr_segs = state->nr_segs;
2064 }