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/uio.h>
   6 #include <linux/pagemap.h>
   7 #include <linux/slab.h>
   8 #include <linux/vmalloc.h>
   9 #include <linux/splice.h>
  10 #include <net/checksum.h>
  11 #include <linux/scatterlist.h>
  12 #include <linux/instrumented.h>
  13
  14 #define PIPE_PARANOIA /* for now */
  15
  16 #define iterate_iovec(i, n, __v, __p, skip, STEP) {     \
  17         size_t left;                                    \
  18         size_t wanted = n;                              \
  19         __p = i->iov;                                   \
  20         __v.iov_len = min(n, __p->iov_len - skip);      \
  21         if (likely(__v.iov_len)) {                      \
  22                 __v.iov_base = __p->iov_base + skip;    \
  23                 left = (STEP);                          \
  24                 __v.iov_len -= left;                    \
  25                 skip += __v.iov_len;                    \
  26                 n -= __v.iov_len;                       \
  27         } else {                                        \
  28                 left = 0;                               \
  29         }                                               \
  30         while (unlikely(!left && n)) {                  \
  31                 __p++;                                  \
  32                 __v.iov_len = min(n, __p->iov_len);     \
  33                 if (unlikely(!__v.iov_len))             \
  34                         continue;                       \
  35                 __v.iov_base = __p->iov_base;           \
  36                 left = (STEP);                          \
  37                 __v.iov_len -= left;                    \
  38                 skip = __v.iov_len;                     \
  39                 n -= __v.iov_len;                       \
  40         }                                               \
  41         n = wanted - n;                                 \
  42 }
  43
  44 #define iterate_kvec(i, n, __v, __p, skip, STEP) {      \
  45         size_t wanted = n;                              \
  46         __p = i->kvec;                                  \
  47         __v.iov_len = min(n, __p->iov_len - skip);      \
  48         if (likely(__v.iov_len)) {                      \
  49                 __v.iov_base = __p->iov_base + skip;    \
  50                 (void)(STEP);                           \
  51                 skip += __v.iov_len;                    \
  52                 n -= __v.iov_len;                       \
  53         }                                               \
  54         while (unlikely(n)) {                           \
  55                 __p++;                                  \
  56                 __v.iov_len = min(n, __p->iov_len);     \
  57                 if (unlikely(!__v.iov_len))             \
  58                         continue;                       \
  59                 __v.iov_base = __p->iov_base;           \
  60                 (void)(STEP);                           \
  61                 skip = __v.iov_len;                     \
  62                 n -= __v.iov_len;                       \
  63         }                                               \
  64         n = wanted;                                     \
  65 }
  66
  67 #define iterate_bvec(i, n, __v, __bi, skip, STEP) {     \
  68         struct bvec_iter __start;                       \
  69         __start.bi_size = n;                            \
  70         __start.bi_bvec_done = skip;                    \
  71         __start.bi_idx = 0;                             \
  72         for_each_bvec(__v, i->bvec, __bi, __start) {    \
  73                 if (!__v.bv_len)                        \
  74                         continue;                       \
  75                 (void)(STEP);                           \
  76         }                                               \
  77 }
  78
  79 #define iterate_all_kinds(i, n, v, I, B, K) {                   \
  80         if (likely(n)) {                                        \
  81                 size_t skip = i->iov_offset;                    \
  82                 if (unlikely(i->type & ITER_BVEC)) {            \
  83                         struct bio_vec v;                       \
  84                         struct bvec_iter __bi;                  \
  85                         iterate_bvec(i, n, v, __bi, skip, (B))  \
  86                 } else if (unlikely(i->type & ITER_KVEC)) {     \
  87                         const struct kvec *kvec;                \
  88                         struct kvec v;                          \
  89                         iterate_kvec(i, n, v, kvec, skip, (K))  \
  90                 } else if (unlikely(i->type & ITER_DISCARD)) {  \
  91                 } else {                                        \
  92                         const struct iovec *iov;                \
  93                         struct iovec v;                         \
  94                         iterate_iovec(i, n, v, iov, skip, (I))  \
  95                 }                                               \
  96         }                                                       \
  97 }
  98
  99 #define iterate_and_advance(i, n, v, I, B, K) {                 \
 100         if (unlikely(i->count < n))                             \
 101                 n = i->count;                                   \
 102         if (i->count) {                                         \
 103                 size_t skip = i->iov_offset;                    \
 104                 if (unlikely(i->type & ITER_BVEC)) {            \
 105                         const struct bio_vec *bvec = i->bvec;   \
 106                         struct bio_vec v;                       \
 107                         struct bvec_iter __bi;                  \
 108                         iterate_bvec(i, n, v, __bi, skip, (B))  \
 109                         i->bvec = __bvec_iter_bvec(i->bvec, __bi);      \
 110                         i->nr_segs -= i->bvec - bvec;           \
 111                         skip = __bi.bi_bvec_done;               \
 112                 } else if (unlikely(i->type & ITER_KVEC)) {     \
 113                         const struct kvec *kvec;                \
 114                         struct kvec v;                          \
 115                         iterate_kvec(i, n, v, kvec, skip, (K))  \
 116                         if (skip == kvec->iov_len) {            \
 117                                 kvec++;                         \
 118                                 skip = 0;                       \
 119                         }                                       \
 120                         i->nr_segs -= kvec - i->kvec;           \
 121                         i->kvec = kvec;                         \
 122                 } else if (unlikely(i->type & ITER_DISCARD)) {  \
 123                         skip += n;                              \
 124                 } else {                                        \
 125                         const struct iovec *iov;                \
 126                         struct iovec v;                         \
 127                         iterate_iovec(i, n, v, iov, skip, (I))  \
 128                         if (skip == iov->iov_len) {             \
 129                                 iov++;                          \
 130                                 skip = 0;                       \
 131                         }                                       \
 132                         i->nr_segs -= iov - i->iov;             \
 133                         i->iov = iov;                           \
 134                 }                                               \
 135                 i->count -= n;                                  \
 136                 i->iov_offset = skip;                           \
 137         }                                                       \
 138 }
 139
 140 static int copyout(void __user *to, const void *from, size_t n)
 141 {
 142         if (access_ok(to, n)) {
 143                 instrument_copy_to_user(to, from, n);
 144                 n = raw_copy_to_user(to, from, n);
 145         }
 146         return n;
 147 }
 148
 149 static int copyin(void *to, const void __user *from, size_t n)
 150 {
 151         if (access_ok(from, n)) {
 152                 instrument_copy_from_user(to, from, n);
 153                 n = raw_copy_from_user(to, from, n);
 154         }
 155         return n;
 156 }
 157
 158 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
 159                          struct iov_iter *i)
 160 {
 161         size_t skip, copy, left, wanted;
 162         const struct iovec *iov;
 163         char __user *buf;
 164         void *kaddr, *from;
 165
 166         if (unlikely(bytes > i->count))
 167                 bytes = i->count;
 168
 169         if (unlikely(!bytes))
 170                 return 0;
 171
 172         might_fault();
 173         wanted = bytes;
 174         iov = i->iov;
 175         skip = i->iov_offset;
 176         buf = iov->iov_base + skip;
 177         copy = min(bytes, iov->iov_len - skip);
 178
 179         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
 180                 kaddr = kmap_atomic(page);
 181                 from = kaddr + offset;
 182
 183                 /* first chunk, usually the only one */
 184                 left = copyout(buf, from, copy);
 185                 copy -= left;
 186                 skip += copy;
 187                 from += copy;
 188                 bytes -= copy;
 189
 190                 while (unlikely(!left && bytes)) {
 191                         iov++;
 192                         buf = iov->iov_base;
 193                         copy = min(bytes, iov->iov_len);
 194                         left = copyout(buf, from, copy);
 195                         copy -= left;
 196                         skip = copy;
 197                         from += copy;
 198                         bytes -= copy;
 199                 }
 200                 if (likely(!bytes)) {
 201                         kunmap_atomic(kaddr);
 202                         goto done;
 203                 }
 204                 offset = from - kaddr;
 205                 buf += copy;
 206                 kunmap_atomic(kaddr);
 207                 copy = min(bytes, iov->iov_len - skip);
 208         }
 209         /* Too bad - revert to non-atomic kmap */
 210
 211         kaddr = kmap(page);
 212         from = kaddr + offset;
 213         left = copyout(buf, from, copy);
 214         copy -= left;
 215         skip += copy;
 216         from += copy;
 217         bytes -= copy;
 218         while (unlikely(!left && bytes)) {
 219                 iov++;
 220                 buf = iov->iov_base;
 221                 copy = min(bytes, iov->iov_len);
 222                 left = copyout(buf, from, copy);
 223                 copy -= left;
 224                 skip = copy;
 225                 from += copy;
 226                 bytes -= copy;
 227         }
 228         kunmap(page);
 229
 230 done:
 231         if (skip == iov->iov_len) {
 232                 iov++;
 233                 skip = 0;
 234         }
 235         i->count -= wanted - bytes;
 236         i->nr_segs -= iov - i->iov;
 237         i->iov = iov;
 238         i->iov_offset = skip;
 239         return wanted - bytes;
 240 }
 241
 242 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
 243                          struct iov_iter *i)
 244 {
 245         size_t skip, copy, left, wanted;
 246         const struct iovec *iov;
 247         char __user *buf;
 248         void *kaddr, *to;
 249
 250         if (unlikely(bytes > i->count))
 251                 bytes = i->count;
 252
 253         if (unlikely(!bytes))
 254                 return 0;
 255
 256         might_fault();
 257         wanted = bytes;
 258         iov = i->iov;
 259         skip = i->iov_offset;
 260         buf = iov->iov_base + skip;
 261         copy = min(bytes, iov->iov_len - skip);
 262
 263         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
 264                 kaddr = kmap_atomic(page);
 265                 to = kaddr + offset;
 266
 267                 /* first chunk, usually the only one */
 268                 left = copyin(to, buf, copy);
 269                 copy -= left;
 270                 skip += copy;
 271                 to += copy;
 272                 bytes -= copy;
 273
 274                 while (unlikely(!left && bytes)) {
 275                         iov++;
 276                         buf = iov->iov_base;
 277                         copy = min(bytes, iov->iov_len);
 278                         left = copyin(to, buf, copy);
 279                         copy -= left;
 280                         skip = copy;
 281                         to += copy;
 282                         bytes -= copy;
 283                 }
 284                 if (likely(!bytes)) {
 285                         kunmap_atomic(kaddr);
 286                         goto done;
 287                 }
 288                 offset = to - kaddr;
 289                 buf += copy;
 290                 kunmap_atomic(kaddr);
 291                 copy = min(bytes, iov->iov_len - skip);
 292         }
 293         /* Too bad - revert to non-atomic kmap */
 294
 295         kaddr = kmap(page);
 296         to = kaddr + offset;
 297         left = copyin(to, buf, copy);
 298         copy -= left;
 299         skip += copy;
 300         to += copy;
 301         bytes -= copy;
 302         while (unlikely(!left && bytes)) {
 303                 iov++;
 304                 buf = iov->iov_base;
 305                 copy = min(bytes, iov->iov_len);
 306                 left = copyin(to, buf, copy);
 307                 copy -= left;
 308                 skip = copy;
 309                 to += copy;
 310                 bytes -= copy;
 311         }
 312         kunmap(page);
 313
 314 done:
 315         if (skip == iov->iov_len) {
 316                 iov++;
 317                 skip = 0;
 318         }
 319         i->count -= wanted - bytes;
 320         i->nr_segs -= iov - i->iov;
 321         i->iov = iov;
 322         i->iov_offset = skip;
 323         return wanted - bytes;
 324 }
 325
 326 #ifdef PIPE_PARANOIA
 327 static bool sanity(const struct iov_iter *i)
 328 {
 329         struct pipe_inode_info *pipe = i->pipe;
 330         unsigned int p_head = pipe->head;
 331         unsigned int p_tail = pipe->tail;
 332         unsigned int p_mask = pipe->ring_size - 1;
 333         unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
 334         unsigned int i_head = i->head;
 335         unsigned int idx;
 336
 337         if (i->iov_offset) {
 338                 struct pipe_buffer *p;
 339                 if (unlikely(p_occupancy == 0))
 340                         goto Bad;       // pipe must be non-empty
 341                 if (unlikely(i_head != p_head - 1))
 342                         goto Bad;       // must be at the last buffer...
 343
 344                 p = &pipe->bufs[i_head & p_mask];
 345                 if (unlikely(p->offset + p->len != i->iov_offset))
 346                         goto Bad;       // ... at the end of segment
 347         } else {
 348                 if (i_head != p_head)
 349                         goto Bad;       // must be right after the last buffer
 350         }
 351         return true;
 352 Bad:
 353         printk(KERN_ERR "idx = %d, offset = %zd\n", i_head, i->iov_offset);
 354         printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
 355                         p_head, p_tail, pipe->ring_size);
 356         for (idx = 0; idx < pipe->ring_size; idx++)
 357                 printk(KERN_ERR "[%p %p %d %d]\n",
 358                         pipe->bufs[idx].ops,
 359                         pipe->bufs[idx].page,
 360                         pipe->bufs[idx].offset,
 361                         pipe->bufs[idx].len);
 362         WARN_ON(1);
 363         return false;
 364 }
 365 #else
 366 #define sanity(i) true
 367 #endif
 368
 369 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
 370                          struct iov_iter *i)
 371 {
 372         struct pipe_inode_info *pipe = i->pipe;
 373         struct pipe_buffer *buf;
 374         unsigned int p_tail = pipe->tail;
 375         unsigned int p_mask = pipe->ring_size - 1;
 376         unsigned int i_head = i->head;
 377         size_t off;
 378
 379         if (unlikely(bytes > i->count))
 380                 bytes = i->count;
 381
 382         if (unlikely(!bytes))
 383                 return 0;
 384
 385         if (!sanity(i))
 386                 return 0;
 387
 388         off = i->iov_offset;
 389         buf = &pipe->bufs[i_head & p_mask];
 390         if (off) {
 391                 if (offset == off && buf->page == page) {
 392                         /* merge with the last one */
 393                         buf->len += bytes;
 394                         i->iov_offset += bytes;
 395                         goto out;
 396                 }
 397                 i_head++;
 398                 buf = &pipe->bufs[i_head & p_mask];
 399         }
 400         if (pipe_full(i_head, p_tail, pipe->max_usage))
 401                 return 0;
 402
 403         buf->ops = &page_cache_pipe_buf_ops;
 404         get_page(page);
 405         buf->page = page;
 406         buf->offset = offset;
 407         buf->len = bytes;
 408
 409         pipe->head = i_head + 1;
 410         i->iov_offset = offset + bytes;
 411         i->head = i_head;
 412 out:
 413         i->count -= bytes;
 414         return bytes;
 415 }
 416
 417 /*
 418  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 419  * bytes.  For each iovec, fault in each page that constitutes the iovec.
 420  *
 421  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 422  * because it is an invalid address).
 423  */
 424 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 425 {
 426         size_t skip = i->iov_offset;
 427         const struct iovec *iov;
 428         int err;
 429         struct iovec v;
 430
 431         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 432                 iterate_iovec(i, bytes, v, iov, skip, ({
 433                         err = fault_in_pages_readable(v.iov_base, v.iov_len);
 434                         if (unlikely(err))
 435                         return err;
 436                 0;}))
 437         }
 438         return 0;
 439 }
 440 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 441
 442 void iov_iter_init(struct iov_iter *i, unsigned int direction,
 443                         const struct iovec *iov, unsigned long nr_segs,
 444                         size_t count)
 445 {
 446         WARN_ON(direction & ~(READ | WRITE));
 447         direction &= READ | WRITE;
 448
 449         /* It will get better.  Eventually... */
 450         if (uaccess_kernel()) {
 451                 i->type = ITER_KVEC | direction;
 452                 i->kvec = (struct kvec *)iov;
 453         } else {
 454                 i->type = ITER_IOVEC | direction;
 455                 i->iov = iov;
 456         }
 457         i->nr_segs = nr_segs;
 458         i->iov_offset = 0;
 459         i->count = count;
 460 }
 461 EXPORT_SYMBOL(iov_iter_init);
 462
 463 static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
 464 {
 465         char *from = kmap_atomic(page);
 466         memcpy(to, from + offset, len);
 467         kunmap_atomic(from);
 468 }
 469
 470 static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 471 {
 472         char *to = kmap_atomic(page);
 473         memcpy(to + offset, from, len);
 474         kunmap_atomic(to);
 475 }
 476
 477 static void memzero_page(struct page *page, size_t offset, size_t len)
 478 {
 479         char *addr = kmap_atomic(page);
 480         memset(addr + offset, 0, len);
 481         kunmap_atomic(addr);
 482 }
 483
 484 static inline bool allocated(struct pipe_buffer *buf)
 485 {
 486         return buf->ops == &default_pipe_buf_ops;
 487 }
 488
 489 static inline void data_start(const struct iov_iter *i,
 490                               unsigned int *iter_headp, size_t *offp)
 491 {
 492         unsigned int p_mask = i->pipe->ring_size - 1;
 493         unsigned int iter_head = i->head;
 494         size_t off = i->iov_offset;
 495
 496         if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) ||
 497                     off == PAGE_SIZE)) {
 498                 iter_head++;
 499                 off = 0;
 500         }
 501         *iter_headp = iter_head;
 502         *offp = off;
 503 }
 504
 505 static size_t push_pipe(struct iov_iter *i, size_t size,
 506                         int *iter_headp, size_t *offp)
 507 {
 508         struct pipe_inode_info *pipe = i->pipe;
 509         unsigned int p_tail = pipe->tail;
 510         unsigned int p_mask = pipe->ring_size - 1;
 511         unsigned int iter_head;
 512         size_t off;
 513         ssize_t left;
 514
 515         if (unlikely(size > i->count))
 516                 size = i->count;
 517         if (unlikely(!size))
 518                 return 0;
 519
 520         left = size;
 521         data_start(i, &iter_head, &off);
 522         *iter_headp = iter_head;
 523         *offp = off;
 524         if (off) {
 525                 left -= PAGE_SIZE - off;
 526                 if (left <= 0) {
 527                         pipe->bufs[iter_head & p_mask].len += size;
 528                         return size;
 529                 }
 530                 pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
 531                 iter_head++;
 532         }
 533         while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
 534                 struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
 535                 struct page *page = alloc_page(GFP_USER);
 536                 if (!page)
 537                         break;
 538
 539                 buf->ops = &default_pipe_buf_ops;
 540                 buf->page = page;
 541                 buf->offset = 0;
 542                 buf->len = min_t(ssize_t, left, PAGE_SIZE);
 543                 left -= buf->len;
 544                 iter_head++;
 545                 pipe->head = iter_head;
 546
 547                 if (left == 0)
 548                         return size;
 549         }
 550         return size - left;
 551 }
 552
 553 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
 554                                 struct iov_iter *i)
 555 {
 556         struct pipe_inode_info *pipe = i->pipe;
 557         unsigned int p_mask = pipe->ring_size - 1;
 558         unsigned int i_head;
 559         size_t n, off;
 560
 561         if (!sanity(i))
 562                 return 0;
 563
 564         bytes = n = push_pipe(i, bytes, &i_head, &off);
 565         if (unlikely(!n))
 566                 return 0;
 567         do {
 568                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 569                 memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
 570                 i->head = i_head;
 571                 i->iov_offset = off + chunk;
 572                 n -= chunk;
 573                 addr += chunk;
 574                 off = 0;
 575                 i_head++;
 576         } while (n);
 577         i->count -= bytes;
 578         return bytes;
 579 }
 580
 581 static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
 582                               __wsum sum, size_t off)
 583 {
 584         __wsum next = csum_partial_copy_nocheck(from, to, len, 0);
 585         return csum_block_add(sum, next, off);
 586 }
 587
 588 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
 589                                 __wsum *csum, struct iov_iter *i)
 590 {
 591         struct pipe_inode_info *pipe = i->pipe;
 592         unsigned int p_mask = pipe->ring_size - 1;
 593         unsigned int i_head;
 594         size_t n, r;
 595         size_t off = 0;
 596         __wsum sum = *csum;
 597
 598         if (!sanity(i))
 599                 return 0;
 600
 601         bytes = n = push_pipe(i, bytes, &i_head, &r);
 602         if (unlikely(!n))
 603                 return 0;
 604         do {
 605                 size_t chunk = min_t(size_t, n, PAGE_SIZE - r);
 606                 char *p = kmap_atomic(pipe->bufs[i_head & p_mask].page);
 607                 sum = csum_and_memcpy(p + r, addr, chunk, sum, off);
 608                 kunmap_atomic(p);
 609                 i->head = i_head;
 610                 i->iov_offset = r + chunk;
 611                 n -= chunk;
 612                 off += chunk;
 613                 addr += chunk;
 614                 r = 0;
 615                 i_head++;
 616         } while (n);
 617         i->count -= bytes;
 618         *csum = sum;
 619         return bytes;
 620 }
 621
 622 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 623 {
 624         const char *from = addr;
 625         if (unlikely(iov_iter_is_pipe(i)))
 626                 return copy_pipe_to_iter(addr, bytes, i);
 627         if (iter_is_iovec(i))
 628                 might_fault();
 629         iterate_and_advance(i, bytes, v,
 630                 copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
 631                 memcpy_to_page(v.bv_page, v.bv_offset,
 632                                (from += v.bv_len) - v.bv_len, v.bv_len),
 633                 memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
 634         )
 635
 636         return bytes;
 637 }
 638 EXPORT_SYMBOL(_copy_to_iter);
 639
 640 #ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE
 641 static int copyout_mcsafe(void __user *to, const void *from, size_t n)
 642 {
 643         if (access_ok(to, n)) {
 644                 instrument_copy_to_user(to, from, n);
 645                 n = copy_to_user_mcsafe((__force void *) to, from, n);
 646         }
 647         return n;
 648 }
 649
 650 static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset,
 651                 const char *from, size_t len)
 652 {
 653         unsigned long ret;
 654         char *to;
 655
 656         to = kmap_atomic(page);
 657         ret = memcpy_mcsafe(to + offset, from, len);
 658         kunmap_atomic(to);
 659
 660         return ret;
 661 }
 662
 663 static size_t copy_pipe_to_iter_mcsafe(const void *addr, size_t bytes,
 664                                 struct iov_iter *i)
 665 {
 666         struct pipe_inode_info *pipe = i->pipe;
 667         unsigned int p_mask = pipe->ring_size - 1;
 668         unsigned int i_head;
 669         size_t n, off, xfer = 0;
 670
 671         if (!sanity(i))
 672                 return 0;
 673
 674         bytes = n = push_pipe(i, bytes, &i_head, &off);
 675         if (unlikely(!n))
 676                 return 0;
 677         do {
 678                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 679                 unsigned long rem;
 680
 681                 rem = memcpy_mcsafe_to_page(pipe->bufs[i_head & p_mask].page,
 682                                             off, addr, chunk);
 683                 i->head = i_head;
 684                 i->iov_offset = off + chunk - rem;
 685                 xfer += chunk - rem;
 686                 if (rem)
 687                         break;
 688                 n -= chunk;
 689                 addr += chunk;
 690                 off = 0;
 691                 i_head++;
 692         } while (n);
 693         i->count -= xfer;
 694         return xfer;
 695 }
 696
 697 /**
 698  * _copy_to_iter_mcsafe - copy to user with source-read error exception handling
 699  * @addr: source kernel address
 700  * @bytes: total transfer length
 701  * @iter: destination iterator
 702  *
 703  * The pmem driver arranges for filesystem-dax to use this facility via
 704  * dax_copy_to_iter() for protecting read/write to persistent memory.
 705  * Unless / until an architecture can guarantee identical performance
 706  * between _copy_to_iter_mcsafe() and _copy_to_iter() it would be a
 707  * performance regression to switch more users to the mcsafe version.
 708  *
 709  * Otherwise, the main differences between this and typical _copy_to_iter().
 710  *
 711  * * Typical tail/residue handling after a fault retries the copy
 712  *   byte-by-byte until the fault happens again. Re-triggering machine
 713  *   checks is potentially fatal so the implementation uses source
 714  *   alignment and poison alignment assumptions to avoid re-triggering
 715  *   hardware exceptions.
 716  *
 717  * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
 718  *   Compare to copy_to_iter() where only ITER_IOVEC attempts might return
 719  *   a short copy.
 720  *
 721  * See MCSAFE_TEST for self-test.
 722  */
 723 size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i)
 724 {
 725         const char *from = addr;
 726         unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
 727
 728         if (unlikely(iov_iter_is_pipe(i)))
 729                 return copy_pipe_to_iter_mcsafe(addr, bytes, i);
 730         if (iter_is_iovec(i))
 731                 might_fault();
 732         iterate_and_advance(i, bytes, v,
 733                 copyout_mcsafe(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
 734                 ({
 735                 rem = memcpy_mcsafe_to_page(v.bv_page, v.bv_offset,
 736                                (from += v.bv_len) - v.bv_len, v.bv_len);
 737                 if (rem) {
 738                         curr_addr = (unsigned long) from;
 739                         bytes = curr_addr - s_addr - rem;
 740                         return bytes;
 741                 }
 742                 }),
 743                 ({
 744                 rem = memcpy_mcsafe(v.iov_base, (from += v.iov_len) - v.iov_len,
 745                                 v.iov_len);
 746                 if (rem) {
 747                         curr_addr = (unsigned long) from;
 748                         bytes = curr_addr - s_addr - rem;
 749                         return bytes;
 750                 }
 751                 })
 752         )
 753
 754         return bytes;
 755 }
 756 EXPORT_SYMBOL_GPL(_copy_to_iter_mcsafe);
 757 #endif /* CONFIG_ARCH_HAS_UACCESS_MCSAFE */
 758
 759 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 760 {
 761         char *to = addr;
 762         if (unlikely(iov_iter_is_pipe(i))) {
 763                 WARN_ON(1);
 764                 return 0;
 765         }
 766         if (iter_is_iovec(i))
 767                 might_fault();
 768         iterate_and_advance(i, bytes, v,
 769                 copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 770                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 771                                  v.bv_offset, v.bv_len),
 772                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 773         )
 774
 775         return bytes;
 776 }
 777 EXPORT_SYMBOL(_copy_from_iter);
 778
 779 bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 780 {
 781         char *to = addr;
 782         if (unlikely(iov_iter_is_pipe(i))) {
 783                 WARN_ON(1);
 784                 return false;
 785         }
 786         if (unlikely(i->count < bytes))
 787                 return false;
 788
 789         if (iter_is_iovec(i))
 790                 might_fault();
 791         iterate_all_kinds(i, bytes, v, ({
 792                 if (copyin((to += v.iov_len) - v.iov_len,
 793                                       v.iov_base, v.iov_len))
 794                         return false;
 795                 0;}),
 796                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 797                                  v.bv_offset, v.bv_len),
 798                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 799         )
 800
 801         iov_iter_advance(i, bytes);
 802         return true;
 803 }
 804 EXPORT_SYMBOL(_copy_from_iter_full);
 805
 806 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 807 {
 808         char *to = addr;
 809         if (unlikely(iov_iter_is_pipe(i))) {
 810                 WARN_ON(1);
 811                 return 0;
 812         }
 813         iterate_and_advance(i, bytes, v,
 814                 __copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 815                                          v.iov_base, v.iov_len),
 816                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 817                                  v.bv_offset, v.bv_len),
 818                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 819         )
 820
 821         return bytes;
 822 }
 823 EXPORT_SYMBOL(_copy_from_iter_nocache);
 824
 825 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 826 /**
 827  * _copy_from_iter_flushcache - write destination through cpu cache
 828  * @addr: destination kernel address
 829  * @bytes: total transfer length
 830  * @iter: source iterator
 831  *
 832  * The pmem driver arranges for filesystem-dax to use this facility via
 833  * dax_copy_from_iter() for ensuring that writes to persistent memory
 834  * are flushed through the CPU cache. It is differentiated from
 835  * _copy_from_iter_nocache() in that guarantees all data is flushed for
 836  * all iterator types. The _copy_from_iter_nocache() only attempts to
 837  * bypass the cache for the ITER_IOVEC case, and on some archs may use
 838  * instructions that strand dirty-data in the cache.
 839  */
 840 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 841 {
 842         char *to = addr;
 843         if (unlikely(iov_iter_is_pipe(i))) {
 844                 WARN_ON(1);
 845                 return 0;
 846         }
 847         iterate_and_advance(i, bytes, v,
 848                 __copy_from_user_flushcache((to += v.iov_len) - v.iov_len,
 849                                          v.iov_base, v.iov_len),
 850                 memcpy_page_flushcache((to += v.bv_len) - v.bv_len, v.bv_page,
 851                                  v.bv_offset, v.bv_len),
 852                 memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base,
 853                         v.iov_len)
 854         )
 855
 856         return bytes;
 857 }
 858 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 859 #endif
 860
 861 bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 862 {
 863         char *to = addr;
 864         if (unlikely(iov_iter_is_pipe(i))) {
 865                 WARN_ON(1);
 866                 return false;
 867         }
 868         if (unlikely(i->count < bytes))
 869                 return false;
 870         iterate_all_kinds(i, bytes, v, ({
 871                 if (__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 872                                              v.iov_base, v.iov_len))
 873                         return false;
 874                 0;}),
 875                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 876                                  v.bv_offset, v.bv_len),
 877                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 878         )
 879
 880         iov_iter_advance(i, bytes);
 881         return true;
 882 }
 883 EXPORT_SYMBOL(_copy_from_iter_full_nocache);
 884
 885 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 886 {
 887         struct page *head;
 888         size_t v = n + offset;
 889
 890         /*
 891          * The general case needs to access the page order in order
 892          * to compute the page size.
 893          * However, we mostly deal with order-0 pages and thus can
 894          * avoid a possible cache line miss for requests that fit all
 895          * page orders.
 896          */
 897         if (n <= v && v <= PAGE_SIZE)
 898                 return true;
 899
 900         head = compound_head(page);
 901         v += (page - head) << PAGE_SHIFT;
 902
 903         if (likely(n <= v && v <= (page_size(head))))
 904                 return true;
 905         WARN_ON(1);
 906         return false;
 907 }
 908
 909 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 910                          struct iov_iter *i)
 911 {
 912         if (unlikely(!page_copy_sane(page, offset, bytes)))
 913                 return 0;
 914         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 915                 void *kaddr = kmap_atomic(page);
 916                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 917                 kunmap_atomic(kaddr);
 918                 return wanted;
 919         } else if (unlikely(iov_iter_is_discard(i)))
 920                 return bytes;
 921         else if (likely(!iov_iter_is_pipe(i)))
 922                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 923         else
 924                 return copy_page_to_iter_pipe(page, offset, bytes, i);
 925 }
 926 EXPORT_SYMBOL(copy_page_to_iter);
 927
 928 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 929                          struct iov_iter *i)
 930 {
 931         if (unlikely(!page_copy_sane(page, offset, bytes)))
 932                 return 0;
 933         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
 934                 WARN_ON(1);
 935                 return 0;
 936         }
 937         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 938                 void *kaddr = kmap_atomic(page);
 939                 size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
 940                 kunmap_atomic(kaddr);
 941                 return wanted;
 942         } else
 943                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 944 }
 945 EXPORT_SYMBOL(copy_page_from_iter);
 946
 947 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
 948 {
 949         struct pipe_inode_info *pipe = i->pipe;
 950         unsigned int p_mask = pipe->ring_size - 1;
 951         unsigned int i_head;
 952         size_t n, off;
 953
 954         if (!sanity(i))
 955                 return 0;
 956
 957         bytes = n = push_pipe(i, bytes, &i_head, &off);
 958         if (unlikely(!n))
 959                 return 0;
 960
 961         do {
 962                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 963                 memzero_page(pipe->bufs[i_head & p_mask].page, off, chunk);
 964                 i->head = i_head;
 965                 i->iov_offset = off + chunk;
 966                 n -= chunk;
 967                 off = 0;
 968                 i_head++;
 969         } while (n);
 970         i->count -= bytes;
 971         return bytes;
 972 }
 973
 974 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 975 {
 976         if (unlikely(iov_iter_is_pipe(i)))
 977                 return pipe_zero(bytes, i);
 978         iterate_and_advance(i, bytes, v,
 979                 clear_user(v.iov_base, v.iov_len),
 980                 memzero_page(v.bv_page, v.bv_offset, v.bv_len),
 981                 memset(v.iov_base, 0, v.iov_len)
 982         )
 983
 984         return bytes;
 985 }
 986 EXPORT_SYMBOL(iov_iter_zero);
 987
 988 size_t iov_iter_copy_from_user_atomic(struct page *page,
 989                 struct iov_iter *i, unsigned long offset, size_t bytes)
 990 {
 991         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 992         if (unlikely(!page_copy_sane(page, offset, bytes))) {
 993                 kunmap_atomic(kaddr);
 994                 return 0;
 995         }
 996         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
 997                 kunmap_atomic(kaddr);
 998                 WARN_ON(1);
 999                 return 0;
1000         }
1001         iterate_all_kinds(i, bytes, v,
1002                 copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
1003                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
1004                                  v.bv_offset, v.bv_len),
1005                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
1006         )
1007         kunmap_atomic(kaddr);
1008         return bytes;
1009 }
1010 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1011
1012 static inline void pipe_truncate(struct iov_iter *i)
1013 {
1014         struct pipe_inode_info *pipe = i->pipe;
1015         unsigned int p_tail = pipe->tail;
1016         unsigned int p_head = pipe->head;
1017         unsigned int p_mask = pipe->ring_size - 1;
1018
1019         if (!pipe_empty(p_head, p_tail)) {
1020                 struct pipe_buffer *buf;
1021                 unsigned int i_head = i->head;
1022                 size_t off = i->iov_offset;
1023
1024                 if (off) {
1025                         buf = &pipe->bufs[i_head & p_mask];
1026                         buf->len = off - buf->offset;
1027                         i_head++;
1028                 }
1029                 while (p_head != i_head) {
1030                         p_head--;
1031                         pipe_buf_release(pipe, &pipe->bufs[p_head & p_mask]);
1032                 }
1033
1034                 pipe->head = p_head;
1035         }
1036 }
1037
1038 static void pipe_advance(struct iov_iter *i, size_t size)
1039 {
1040         struct pipe_inode_info *pipe = i->pipe;
1041         if (unlikely(i->count < size))
1042                 size = i->count;
1043         if (size) {
1044                 struct pipe_buffer *buf;
1045                 unsigned int p_mask = pipe->ring_size - 1;
1046                 unsigned int i_head = i->head;
1047                 size_t off = i->iov_offset, left = size;
1048
1049                 if (off) /* make it relative to the beginning of buffer */
1050                         left += off - pipe->bufs[i_head & p_mask].offset;
1051                 while (1) {
1052                         buf = &pipe->bufs[i_head & p_mask];
1053                         if (left <= buf->len)
1054                                 break;
1055                         left -= buf->len;
1056                         i_head++;
1057                 }
1058                 i->head = i_head;
1059                 i->iov_offset = buf->offset + left;
1060         }
1061         i->count -= size;
1062         /* ... and discard everything past that point */
1063         pipe_truncate(i);
1064 }
1065
1066 void iov_iter_advance(struct iov_iter *i, size_t size)
1067 {
1068         if (unlikely(iov_iter_is_pipe(i))) {
1069                 pipe_advance(i, size);
1070                 return;
1071         }
1072         if (unlikely(iov_iter_is_discard(i))) {
1073                 i->count -= size;
1074                 return;
1075         }
1076         iterate_and_advance(i, size, v, 0, 0, 0)
1077 }
1078 EXPORT_SYMBOL(iov_iter_advance);
1079
1080 void iov_iter_revert(struct iov_iter *i, size_t unroll)
1081 {
1082         if (!unroll)
1083                 return;
1084         if (WARN_ON(unroll > MAX_RW_COUNT))
1085                 return;
1086         i->count += unroll;
1087         if (unlikely(iov_iter_is_pipe(i))) {
1088                 struct pipe_inode_info *pipe = i->pipe;
1089                 unsigned int p_mask = pipe->ring_size - 1;
1090                 unsigned int i_head = i->head;
1091                 size_t off = i->iov_offset;
1092                 while (1) {
1093                         struct pipe_buffer *b = &pipe->bufs[i_head & p_mask];
1094                         size_t n = off - b->offset;
1095                         if (unroll < n) {
1096                                 off -= unroll;
1097                                 break;
1098                         }
1099                         unroll -= n;
1100                         if (!unroll && i_head == i->start_head) {
1101                                 off = 0;
1102                                 break;
1103                         }
1104                         i_head--;
1105                         b = &pipe->bufs[i_head & p_mask];
1106                         off = b->offset + b->len;
1107                 }
1108                 i->iov_offset = off;
1109                 i->head = i_head;
1110                 pipe_truncate(i);
1111                 return;
1112         }
1113         if (unlikely(iov_iter_is_discard(i)))
1114                 return;
1115         if (unroll <= i->iov_offset) {
1116                 i->iov_offset -= unroll;
1117                 return;
1118         }
1119         unroll -= i->iov_offset;
1120         if (iov_iter_is_bvec(i)) {
1121                 const struct bio_vec *bvec = i->bvec;
1122                 while (1) {
1123                         size_t n = (--bvec)->bv_len;
1124                         i->nr_segs++;
1125                         if (unroll <= n) {
1126                                 i->bvec = bvec;
1127                                 i->iov_offset = n - unroll;
1128                                 return;
1129                         }
1130                         unroll -= n;
1131                 }
1132         } else { /* same logics for iovec and kvec */
1133                 const struct iovec *iov = i->iov;
1134                 while (1) {
1135                         size_t n = (--iov)->iov_len;
1136                         i->nr_segs++;
1137                         if (unroll <= n) {
1138                                 i->iov = iov;
1139                                 i->iov_offset = n - unroll;
1140                                 return;
1141                         }
1142                         unroll -= n;
1143                 }
1144         }
1145 }
1146 EXPORT_SYMBOL(iov_iter_revert);
1147
1148 /*
1149  * Return the count of just the current iov_iter segment.
1150  */
1151 size_t iov_iter_single_seg_count(const struct iov_iter *i)
1152 {
1153         if (unlikely(iov_iter_is_pipe(i)))
1154                 return i->count;        // it is a silly place, anyway
1155         if (i->nr_segs == 1)
1156                 return i->count;
1157         if (unlikely(iov_iter_is_discard(i)))
1158                 return i->count;
1159         else if (iov_iter_is_bvec(i))
1160                 return min(i->count, i->bvec->bv_len - i->iov_offset);
1161         else
1162                 return min(i->count, i->iov->iov_len - i->iov_offset);
1163 }
1164 EXPORT_SYMBOL(iov_iter_single_seg_count);
1165
1166 void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
1167                         const struct kvec *kvec, unsigned long nr_segs,
1168                         size_t count)
1169 {
1170         WARN_ON(direction & ~(READ | WRITE));
1171         i->type = ITER_KVEC | (direction & (READ | WRITE));
1172         i->kvec = kvec;
1173         i->nr_segs = nr_segs;
1174         i->iov_offset = 0;
1175         i->count = count;
1176 }
1177 EXPORT_SYMBOL(iov_iter_kvec);
1178
1179 void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
1180                         const struct bio_vec *bvec, unsigned long nr_segs,
1181                         size_t count)
1182 {
1183         WARN_ON(direction & ~(READ | WRITE));
1184         i->type = ITER_BVEC | (direction & (READ | WRITE));
1185         i->bvec = bvec;
1186         i->nr_segs = nr_segs;
1187         i->iov_offset = 0;
1188         i->count = count;
1189 }
1190 EXPORT_SYMBOL(iov_iter_bvec);
1191
1192 void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
1193                         struct pipe_inode_info *pipe,
1194                         size_t count)
1195 {
1196         BUG_ON(direction != READ);
1197         WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
1198         i->type = ITER_PIPE | READ;
1199         i->pipe = pipe;
1200         i->head = pipe->head;
1201         i->iov_offset = 0;
1202         i->count = count;
1203         i->start_head = i->head;
1204 }
1205 EXPORT_SYMBOL(iov_iter_pipe);
1206
1207 /**
1208  * iov_iter_discard - Initialise an I/O iterator that discards data
1209  * @i: The iterator to initialise.
1210  * @direction: The direction of the transfer.
1211  * @count: The size of the I/O buffer in bytes.
1212  *
1213  * Set up an I/O iterator that just discards everything that's written to it.
1214  * It's only available as a READ iterator.
1215  */
1216 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
1217 {
1218         BUG_ON(direction != READ);
1219         i->type = ITER_DISCARD | READ;
1220         i->count = count;
1221         i->iov_offset = 0;
1222 }
1223 EXPORT_SYMBOL(iov_iter_discard);
1224
1225 unsigned long iov_iter_alignment(const struct iov_iter *i)
1226 {
1227         unsigned long res = 0;
1228         size_t size = i->count;
1229
1230         if (unlikely(iov_iter_is_pipe(i))) {
1231                 unsigned int p_mask = i->pipe->ring_size - 1;
1232
1233                 if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask]))
1234                         return size | i->iov_offset;
1235                 return size;
1236         }
1237         iterate_all_kinds(i, size, v,
1238                 (res |= (unsigned long)v.iov_base | v.iov_len, 0),
1239                 res |= v.bv_offset | v.bv_len,
1240                 res |= (unsigned long)v.iov_base | v.iov_len
1241         )
1242         return res;
1243 }
1244 EXPORT_SYMBOL(iov_iter_alignment);
1245
1246 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
1247 {
1248         unsigned long res = 0;
1249         size_t size = i->count;
1250
1251         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1252                 WARN_ON(1);
1253                 return ~0U;
1254         }
1255
1256         iterate_all_kinds(i, size, v,
1257                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
1258                         (size != v.iov_len ? size : 0), 0),
1259                 (res |= (!res ? 0 : (unsigned long)v.bv_offset) |
1260                         (size != v.bv_len ? size : 0)),
1261                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
1262                         (size != v.iov_len ? size : 0))
1263                 );
1264         return res;
1265 }
1266 EXPORT_SYMBOL(iov_iter_gap_alignment);
1267
1268 static inline ssize_t __pipe_get_pages(struct iov_iter *i,
1269                                 size_t maxsize,
1270                                 struct page **pages,
1271                                 int iter_head,
1272                                 size_t *start)
1273 {
1274         struct pipe_inode_info *pipe = i->pipe;
1275         unsigned int p_mask = pipe->ring_size - 1;
1276         ssize_t n = push_pipe(i, maxsize, &iter_head, start);
1277         if (!n)
1278                 return -EFAULT;
1279
1280         maxsize = n;
1281         n += *start;
1282         while (n > 0) {
1283                 get_page(*pages++ = pipe->bufs[iter_head & p_mask].page);
1284                 iter_head++;
1285                 n -= PAGE_SIZE;
1286         }
1287
1288         return maxsize;
1289 }
1290
1291 static ssize_t pipe_get_pages(struct iov_iter *i,
1292                    struct page **pages, size_t maxsize, unsigned maxpages,
1293                    size_t *start)
1294 {
1295         unsigned int iter_head, npages;
1296         size_t capacity;
1297
1298         if (!maxsize)
1299                 return 0;
1300
1301         if (!sanity(i))
1302                 return -EFAULT;
1303
1304         data_start(i, &iter_head, start);
1305         /* Amount of free space: some of this one + all after this one */
1306         npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1307         capacity = min(npages, maxpages) * PAGE_SIZE - *start;
1308
1309         return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
1310 }
1311
1312 ssize_t iov_iter_get_pages(struct iov_iter *i,
1313                    struct page **pages, size_t maxsize, unsigned maxpages,
1314                    size_t *start)
1315 {
1316         if (maxsize > i->count)
1317                 maxsize = i->count;
1318
1319         if (unlikely(iov_iter_is_pipe(i)))
1320                 return pipe_get_pages(i, pages, maxsize, maxpages, start);
1321         if (unlikely(iov_iter_is_discard(i)))
1322                 return -EFAULT;
1323
1324         iterate_all_kinds(i, maxsize, v, ({
1325                 unsigned long addr = (unsigned long)v.iov_base;
1326                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1327                 int n;
1328                 int res;
1329
1330                 if (len > maxpages * PAGE_SIZE)
1331                         len = maxpages * PAGE_SIZE;
1332                 addr &= ~(PAGE_SIZE - 1);
1333                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1334                 res = get_user_pages_fast(addr, n,
1335                                 iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0,
1336                                 pages);
1337                 if (unlikely(res < 0))
1338                         return res;
1339                 return (res == n ? len : res * PAGE_SIZE) - *start;
1340         0;}),({
1341                 /* can't be more than PAGE_SIZE */
1342                 *start = v.bv_offset;
1343                 get_page(*pages = v.bv_page);
1344                 return v.bv_len;
1345         }),({
1346                 return -EFAULT;
1347         })
1348         )
1349         return 0;
1350 }
1351 EXPORT_SYMBOL(iov_iter_get_pages);
1352
1353 static struct page **get_pages_array(size_t n)
1354 {
1355         return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
1356 }
1357
1358 static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
1359                    struct page ***pages, size_t maxsize,
1360                    size_t *start)
1361 {
1362         struct page **p;
1363         unsigned int iter_head, npages;
1364         ssize_t n;
1365
1366         if (!maxsize)
1367                 return 0;
1368
1369         if (!sanity(i))
1370                 return -EFAULT;
1371
1372         data_start(i, &iter_head, start);
1373         /* Amount of free space: some of this one + all after this one */
1374         npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1375         n = npages * PAGE_SIZE - *start;
1376         if (maxsize > n)
1377                 maxsize = n;
1378         else
1379                 npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
1380         p = get_pages_array(npages);
1381         if (!p)
1382                 return -ENOMEM;
1383         n = __pipe_get_pages(i, maxsize, p, iter_head, start);
1384         if (n > 0)
1385                 *pages = p;
1386         else
1387                 kvfree(p);
1388         return n;
1389 }
1390
1391 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
1392                    struct page ***pages, size_t maxsize,
1393                    size_t *start)
1394 {
1395         struct page **p;
1396
1397         if (maxsize > i->count)
1398                 maxsize = i->count;
1399
1400         if (unlikely(iov_iter_is_pipe(i)))
1401                 return pipe_get_pages_alloc(i, pages, maxsize, start);
1402         if (unlikely(iov_iter_is_discard(i)))
1403                 return -EFAULT;
1404
1405         iterate_all_kinds(i, maxsize, v, ({
1406                 unsigned long addr = (unsigned long)v.iov_base;
1407                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1408                 int n;
1409                 int res;
1410
1411                 addr &= ~(PAGE_SIZE - 1);
1412                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1413                 p = get_pages_array(n);
1414                 if (!p)
1415                         return -ENOMEM;
1416                 res = get_user_pages_fast(addr, n,
1417                                 iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0, p);
1418                 if (unlikely(res < 0)) {
1419                         kvfree(p);
1420                         return res;
1421                 }
1422                 *pages = p;
1423                 return (res == n ? len : res * PAGE_SIZE) - *start;
1424         0;}),({
1425                 /* can't be more than PAGE_SIZE */
1426                 *start = v.bv_offset;
1427                 *pages = p = get_pages_array(1);
1428                 if (!p)
1429                         return -ENOMEM;
1430                 get_page(*p = v.bv_page);
1431                 return v.bv_len;
1432         }),({
1433                 return -EFAULT;
1434         })
1435         )
1436         return 0;
1437 }
1438 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
1439
1440 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1441                                struct iov_iter *i)
1442 {
1443         char *to = addr;
1444         __wsum sum, next;
1445         size_t off = 0;
1446         sum = *csum;
1447         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1448                 WARN_ON(1);
1449                 return 0;
1450         }
1451         iterate_and_advance(i, bytes, v, ({
1452                 int err = 0;
1453                 next = csum_and_copy_from_user(v.iov_base,
1454                                                (to += v.iov_len) - v.iov_len,
1455                                                v.iov_len, 0, &err);
1456                 if (!err) {
1457                         sum = csum_block_add(sum, next, off);
1458                         off += v.iov_len;
1459                 }
1460                 err ? v.iov_len : 0;
1461         }), ({
1462                 char *p = kmap_atomic(v.bv_page);
1463                 sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
1464                                       p + v.bv_offset, v.bv_len,
1465                                       sum, off);
1466                 kunmap_atomic(p);
1467                 off += v.bv_len;
1468         }),({
1469                 sum = csum_and_memcpy((to += v.iov_len) - v.iov_len,
1470                                       v.iov_base, v.iov_len,
1471                                       sum, off);
1472                 off += v.iov_len;
1473         })
1474         )
1475         *csum = sum;
1476         return bytes;
1477 }
1478 EXPORT_SYMBOL(csum_and_copy_from_iter);
1479
1480 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
1481                                struct iov_iter *i)
1482 {
1483         char *to = addr;
1484         __wsum sum, next;
1485         size_t off = 0;
1486         sum = *csum;
1487         if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1488                 WARN_ON(1);
1489                 return false;
1490         }
1491         if (unlikely(i->count < bytes))
1492                 return false;
1493         iterate_all_kinds(i, bytes, v, ({
1494                 int err = 0;
1495                 next = csum_and_copy_from_user(v.iov_base,
1496                                                (to += v.iov_len) - v.iov_len,
1497                                                v.iov_len, 0, &err);
1498                 if (err)
1499                         return false;
1500                 sum = csum_block_add(sum, next, off);
1501                 off += v.iov_len;
1502                 0;
1503         }), ({
1504                 char *p = kmap_atomic(v.bv_page);
1505                 sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
1506                                       p + v.bv_offset, v.bv_len,
1507                                       sum, off);
1508                 kunmap_atomic(p);
1509                 off += v.bv_len;
1510         }),({
1511                 sum = csum_and_memcpy((to += v.iov_len) - v.iov_len,
1512                                       v.iov_base, v.iov_len,
1513                                       sum, off);
1514                 off += v.iov_len;
1515         })
1516         )
1517         *csum = sum;
1518         iov_iter_advance(i, bytes);
1519         return true;
1520 }
1521 EXPORT_SYMBOL(csum_and_copy_from_iter_full);
1522
1523 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
1524                              struct iov_iter *i)
1525 {
1526         const char *from = addr;
1527         __wsum *csum = csump;
1528         __wsum sum, next;
1529         size_t off = 0;
1530
1531         if (unlikely(iov_iter_is_pipe(i)))
1532                 return csum_and_copy_to_pipe_iter(addr, bytes, csum, i);
1533
1534         sum = *csum;
1535         if (unlikely(iov_iter_is_discard(i))) {
1536                 WARN_ON(1);     /* for now */
1537                 return 0;
1538         }
1539         iterate_and_advance(i, bytes, v, ({
1540                 int err = 0;
1541                 next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
1542                                              v.iov_base,
1543                                              v.iov_len, 0, &err);
1544                 if (!err) {
1545                         sum = csum_block_add(sum, next, off);
1546                         off += v.iov_len;
1547                 }
1548                 err ? v.iov_len : 0;
1549         }), ({
1550                 char *p = kmap_atomic(v.bv_page);
1551                 sum = csum_and_memcpy(p + v.bv_offset,
1552                                       (from += v.bv_len) - v.bv_len,
1553                                       v.bv_len, sum, off);
1554                 kunmap_atomic(p);
1555                 off += v.bv_len;
1556         }),({
1557                 sum = csum_and_memcpy(v.iov_base,
1558                                      (from += v.iov_len) - v.iov_len,
1559                                      v.iov_len, sum, off);
1560                 off += v.iov_len;
1561         })
1562         )
1563         *csum = sum;
1564         return bytes;
1565 }
1566 EXPORT_SYMBOL(csum_and_copy_to_iter);
1567
1568 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
1569                 struct iov_iter *i)
1570 {
1571 #ifdef CONFIG_CRYPTO_HASH
1572         struct ahash_request *hash = hashp;
1573         struct scatterlist sg;
1574         size_t copied;
1575
1576         copied = copy_to_iter(addr, bytes, i);
1577         sg_init_one(&sg, addr, copied);
1578         ahash_request_set_crypt(hash, &sg, NULL, copied);
1579         crypto_ahash_update(hash);
1580         return copied;
1581 #else
1582         return 0;
1583 #endif
1584 }
1585 EXPORT_SYMBOL(hash_and_copy_to_iter);
1586
1587 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1588 {
1589         size_t size = i->count;
1590         int npages = 0;
1591
1592         if (!size)
1593                 return 0;
1594         if (unlikely(iov_iter_is_discard(i)))
1595                 return 0;
1596
1597         if (unlikely(iov_iter_is_pipe(i))) {
1598                 struct pipe_inode_info *pipe = i->pipe;
1599                 unsigned int iter_head;
1600                 size_t off;
1601
1602                 if (!sanity(i))
1603                         return 0;
1604
1605                 data_start(i, &iter_head, &off);
1606                 /* some of this one + all after this one */
1607                 npages = pipe_space_for_user(iter_head, pipe->tail, pipe);
1608                 if (npages >= maxpages)
1609                         return maxpages;
1610         } else iterate_all_kinds(i, size, v, ({
1611                 unsigned long p = (unsigned long)v.iov_base;
1612                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1613                         - p / PAGE_SIZE;
1614                 if (npages >= maxpages)
1615                         return maxpages;
1616         0;}),({
1617                 npages++;
1618                 if (npages >= maxpages)
1619                         return maxpages;
1620         }),({
1621                 unsigned long p = (unsigned long)v.iov_base;
1622                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1623                         - p / PAGE_SIZE;
1624                 if (npages >= maxpages)
1625                         return maxpages;
1626         })
1627         )
1628         return npages;
1629 }
1630 EXPORT_SYMBOL(iov_iter_npages);
1631
1632 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1633 {
1634         *new = *old;
1635         if (unlikely(iov_iter_is_pipe(new))) {
1636                 WARN_ON(1);
1637                 return NULL;
1638         }
1639         if (unlikely(iov_iter_is_discard(new)))
1640                 return NULL;
1641         if (iov_iter_is_bvec(new))
1642                 return new->bvec = kmemdup(new->bvec,
1643                                     new->nr_segs * sizeof(struct bio_vec),
1644                                     flags);
1645         else
1646                 /* iovec and kvec have identical layout */
1647                 return new->iov = kmemdup(new->iov,
1648                                    new->nr_segs * sizeof(struct iovec),
1649                                    flags);
1650 }
1651 EXPORT_SYMBOL(dup_iter);
1652
1653 /**
1654  * import_iovec() - Copy an array of &struct iovec from userspace
1655  *     into the kernel, check that it is valid, and initialize a new
1656  *     &struct iov_iter iterator to access it.
1657  *
1658  * @type: One of %READ or %WRITE.
1659  * @uvector: Pointer to the userspace array.
1660  * @nr_segs: Number of elements in userspace array.
1661  * @fast_segs: Number of elements in @iov.
1662  * @iov: (input and output parameter) Pointer to pointer to (usually small
1663  *     on-stack) kernel array.
1664  * @i: Pointer to iterator that will be initialized on success.
1665  *
1666  * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1667  * then this function places %NULL in *@iov on return. Otherwise, a new
1668  * array will be allocated and the result placed in *@iov. This means that
1669  * the caller may call kfree() on *@iov regardless of whether the small
1670  * on-stack array was used or not (and regardless of whether this function
1671  * returns an error or not).
1672  *
1673  * Return: Negative error code on error, bytes imported on success
1674  */
1675 ssize_t import_iovec(int type, const struct iovec __user * uvector,
1676                  unsigned nr_segs, unsigned fast_segs,
1677                  struct iovec **iov, struct iov_iter *i)
1678 {
1679         ssize_t n;
1680         struct iovec *p;
1681         n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1682                                   *iov, &p);
1683         if (n < 0) {
1684                 if (p != *iov)
1685                         kfree(p);
1686                 *iov = NULL;
1687                 return n;
1688         }
1689         iov_iter_init(i, type, p, nr_segs, n);
1690         *iov = p == *iov ? NULL : p;
1691         return n;
1692 }
1693 EXPORT_SYMBOL(import_iovec);
1694
1695 #ifdef CONFIG_COMPAT
1696 #include <linux/compat.h>
1697
1698 ssize_t compat_import_iovec(int type,
1699                 const struct compat_iovec __user * uvector,
1700                 unsigned nr_segs, unsigned fast_segs,
1701                 struct iovec **iov, struct iov_iter *i)
1702 {
1703         ssize_t n;
1704         struct iovec *p;
1705         n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1706                                   *iov, &p);
1707         if (n < 0) {
1708                 if (p != *iov)
1709                         kfree(p);
1710                 *iov = NULL;
1711                 return n;
1712         }
1713         iov_iter_init(i, type, p, nr_segs, n);
1714         *iov = p == *iov ? NULL : p;
1715         return n;
1716 }
1717 EXPORT_SYMBOL(compat_import_iovec);
1718 #endif
1719
1720 int import_single_range(int rw, void __user *buf, size_t len,
1721                  struct iovec *iov, struct iov_iter *i)
1722 {
1723         if (len > MAX_RW_COUNT)
1724                 len = MAX_RW_COUNT;
1725         if (unlikely(!access_ok(buf, len)))
1726                 return -EFAULT;
1727
1728         iov->iov_base = buf;
1729         iov->iov_len = len;
1730         iov_iter_init(i, rw, iov, 1, len);
1731         return 0;
1732 }
1733 EXPORT_SYMBOL(import_single_range);
1734
1735 int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
1736                             int (*f)(struct kvec *vec, void *context),
1737                             void *context)
1738 {
1739         struct kvec w;
1740         int err = -EINVAL;
1741         if (!bytes)
1742                 return 0;
1743
1744         iterate_all_kinds(i, bytes, v, -EINVAL, ({
1745                 w.iov_base = kmap(v.bv_page) + v.bv_offset;
1746                 w.iov_len = v.bv_len;
1747                 err = f(&w, context);
1748                 kunmap(v.bv_page);
1749                 err;}), ({
1750                 w = v;
1751                 err = f(&w, context);})
1752         )
1753         return err;
1754 }
1755 EXPORT_SYMBOL(iov_iter_for_each_range);