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 ubuf and kbuf alike */ 20 #define iterate_buf(i, n, base, len, off, __p, STEP) { \ 21 size_t __maybe_unused off = 0; \ 22 len = n; \ 23 base = __p + i->iov_offset; \ 24 len -= (STEP); \ 25 i->iov_offset += len; \ 26 n = len; \ 27 } 28 29 /* covers iovec and kvec alike */ 30 #define iterate_iovec(i, n, base, len, off, __p, STEP) { \ 31 size_t off = 0; \ 32 size_t skip = i->iov_offset; \ 33 do { \ 34 len = min(n, __p->iov_len - skip); \ 35 if (likely(len)) { \ 36 base = __p->iov_base + skip; \ 37 len -= (STEP); \ 38 off += len; \ 39 skip += len; \ 40 n -= len; \ 41 if (skip < __p->iov_len) \ 42 break; \ 43 } \ 44 __p++; \ 45 skip = 0; \ 46 } while (n); \ 47 i->iov_offset = skip; \ 48 n = off; \ 49 } 50 51 #define iterate_bvec(i, n, base, len, off, p, STEP) { \ 52 size_t off = 0; \ 53 unsigned skip = i->iov_offset; \ 54 while (n) { \ 55 unsigned offset = p->bv_offset + skip; \ 56 unsigned left; \ 57 void *kaddr = kmap_local_page(p->bv_page + \ 58 offset / PAGE_SIZE); \ 59 base = kaddr + offset % PAGE_SIZE; \ 60 len = min(min(n, (size_t)(p->bv_len - skip)), \ 61 (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \ 62 left = (STEP); \ 63 kunmap_local(kaddr); \ 64 len -= left; \ 65 off += len; \ 66 skip += len; \ 67 if (skip == p->bv_len) { \ 68 skip = 0; \ 69 p++; \ 70 } \ 71 n -= len; \ 72 if (left) \ 73 break; \ 74 } \ 75 i->iov_offset = skip; \ 76 n = off; \ 77 } 78 79 #define iterate_xarray(i, n, base, len, __off, STEP) { \ 80 __label__ __out; \ 81 size_t __off = 0; \ 82 struct folio *folio; \ 83 loff_t start = i->xarray_start + i->iov_offset; \ 84 pgoff_t index = start / PAGE_SIZE; \ 85 XA_STATE(xas, i->xarray, index); \ 86 \ 87 len = PAGE_SIZE - offset_in_page(start); \ 88 rcu_read_lock(); \ 89 xas_for_each(&xas, folio, ULONG_MAX) { \ 90 unsigned left; \ 91 size_t offset; \ 92 if (xas_retry(&xas, folio)) \ 93 continue; \ 94 if (WARN_ON(xa_is_value(folio))) \ 95 break; \ 96 if (WARN_ON(folio_test_hugetlb(folio))) \ 97 break; \ 98 offset = offset_in_folio(folio, start + __off); \ 99 while (offset < folio_size(folio)) { \ 100 base = kmap_local_folio(folio, offset); \ 101 len = min(n, len); \ 102 left = (STEP); \ 103 kunmap_local(base); \ 104 len -= left; \ 105 __off += len; \ 106 n -= len; \ 107 if (left || n == 0) \ 108 goto __out; \ 109 offset += len; \ 110 len = PAGE_SIZE; \ 111 } \ 112 } \ 113 __out: \ 114 rcu_read_unlock(); \ 115 i->iov_offset += __off; \ 116 n = __off; \ 117 } 118 119 #define __iterate_and_advance(i, n, base, len, off, I, K) { \ 120 if (unlikely(i->count < n)) \ 121 n = i->count; \ 122 if (likely(n)) { \ 123 if (likely(iter_is_ubuf(i))) { \ 124 void __user *base; \ 125 size_t len; \ 126 iterate_buf(i, n, base, len, off, \ 127 i->ubuf, (I)) \ 128 } else if (likely(iter_is_iovec(i))) { \ 129 const struct iovec *iov = iter_iov(i); \ 130 void __user *base; \ 131 size_t len; \ 132 iterate_iovec(i, n, base, len, off, \ 133 iov, (I)) \ 134 i->nr_segs -= iov - iter_iov(i); \ 135 i->__iov = iov; \ 136 } else if (iov_iter_is_bvec(i)) { \ 137 const struct bio_vec *bvec = i->bvec; \ 138 void *base; \ 139 size_t len; \ 140 iterate_bvec(i, n, base, len, off, \ 141 bvec, (K)) \ 142 i->nr_segs -= bvec - i->bvec; \ 143 i->bvec = bvec; \ 144 } else if (iov_iter_is_kvec(i)) { \ 145 const struct kvec *kvec = i->kvec; \ 146 void *base; \ 147 size_t len; \ 148 iterate_iovec(i, n, base, len, off, \ 149 kvec, (K)) \ 150 i->nr_segs -= kvec - i->kvec; \ 151 i->kvec = kvec; \ 152 } else if (iov_iter_is_xarray(i)) { \ 153 void *base; \ 154 size_t len; \ 155 iterate_xarray(i, n, base, len, off, \ 156 (K)) \ 157 } \ 158 i->count -= n; \ 159 } \ 160 } 161 #define iterate_and_advance(i, n, base, len, off, I, K) \ 162 __iterate_and_advance(i, n, base, len, off, I, ((void)(K),0)) 163 164 static int copyout(void __user *to, const void *from, size_t n) 165 { 166 if (should_fail_usercopy()) 167 return n; 168 if (access_ok(to, n)) { 169 instrument_copy_to_user(to, from, n); 170 n = raw_copy_to_user(to, from, n); 171 } 172 return n; 173 } 174 175 static int copyout_nofault(void __user *to, const void *from, size_t n) 176 { 177 long res; 178 179 if (should_fail_usercopy()) 180 return n; 181 182 res = copy_to_user_nofault(to, from, n); 183 184 return res < 0 ? n : res; 185 } 186 187 static int copyin(void *to, const void __user *from, size_t n) 188 { 189 size_t res = n; 190 191 if (should_fail_usercopy()) 192 return n; 193 if (access_ok(from, n)) { 194 instrument_copy_from_user_before(to, from, n); 195 res = raw_copy_from_user(to, from, n); 196 instrument_copy_from_user_after(to, from, n, res); 197 } 198 return res; 199 } 200 201 #ifdef PIPE_PARANOIA 202 static bool sanity(const struct iov_iter *i) 203 { 204 struct pipe_inode_info *pipe = i->pipe; 205 unsigned int p_head = pipe->head; 206 unsigned int p_tail = pipe->tail; 207 unsigned int p_occupancy = pipe_occupancy(p_head, p_tail); 208 unsigned int i_head = i->head; 209 unsigned int idx; 210 211 if (i->last_offset) { 212 struct pipe_buffer *p; 213 if (unlikely(p_occupancy == 0)) 214 goto Bad; // pipe must be non-empty 215 if (unlikely(i_head != p_head - 1)) 216 goto Bad; // must be at the last buffer... 217 218 p = pipe_buf(pipe, i_head); 219 if (unlikely(p->offset + p->len != abs(i->last_offset))) 220 goto Bad; // ... at the end of segment 221 } else { 222 if (i_head != p_head) 223 goto Bad; // must be right after the last buffer 224 } 225 return true; 226 Bad: 227 printk(KERN_ERR "idx = %d, offset = %d\n", i_head, i->last_offset); 228 printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n", 229 p_head, p_tail, pipe->ring_size); 230 for (idx = 0; idx < pipe->ring_size; idx++) 231 printk(KERN_ERR "[%p %p %d %d]\n", 232 pipe->bufs[idx].ops, 233 pipe->bufs[idx].page, 234 pipe->bufs[idx].offset, 235 pipe->bufs[idx].len); 236 WARN_ON(1); 237 return false; 238 } 239 #else 240 #define sanity(i) true 241 #endif 242 243 static struct page *push_anon(struct pipe_inode_info *pipe, unsigned size) 244 { 245 struct page *page = alloc_page(GFP_USER); 246 if (page) { 247 struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++); 248 *buf = (struct pipe_buffer) { 249 .ops = &default_pipe_buf_ops, 250 .page = page, 251 .offset = 0, 252 .len = size 253 }; 254 } 255 return page; 256 } 257 258 static void push_page(struct pipe_inode_info *pipe, struct page *page, 259 unsigned int offset, unsigned int size) 260 { 261 struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++); 262 *buf = (struct pipe_buffer) { 263 .ops = &page_cache_pipe_buf_ops, 264 .page = page, 265 .offset = offset, 266 .len = size 267 }; 268 get_page(page); 269 } 270 271 static inline int last_offset(const struct pipe_buffer *buf) 272 { 273 if (buf->ops == &default_pipe_buf_ops) 274 return buf->len; // buf->offset is 0 for those 275 else 276 return -(buf->offset + buf->len); 277 } 278 279 static struct page *append_pipe(struct iov_iter *i, size_t size, 280 unsigned int *off) 281 { 282 struct pipe_inode_info *pipe = i->pipe; 283 int offset = i->last_offset; 284 struct pipe_buffer *buf; 285 struct page *page; 286 287 if (offset > 0 && offset < PAGE_SIZE) { 288 // some space in the last buffer; add to it 289 buf = pipe_buf(pipe, pipe->head - 1); 290 size = min_t(size_t, size, PAGE_SIZE - offset); 291 buf->len += size; 292 i->last_offset += size; 293 i->count -= size; 294 *off = offset; 295 return buf->page; 296 } 297 // OK, we need a new buffer 298 *off = 0; 299 size = min_t(size_t, size, PAGE_SIZE); 300 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) 301 return NULL; 302 page = push_anon(pipe, size); 303 if (!page) 304 return NULL; 305 i->head = pipe->head - 1; 306 i->last_offset = size; 307 i->count -= size; 308 return page; 309 } 310 311 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes, 312 struct iov_iter *i) 313 { 314 struct pipe_inode_info *pipe = i->pipe; 315 unsigned int head = pipe->head; 316 317 if (unlikely(bytes > i->count)) 318 bytes = i->count; 319 320 if (unlikely(!bytes)) 321 return 0; 322 323 if (!sanity(i)) 324 return 0; 325 326 if (offset && i->last_offset == -offset) { // could we merge it? 327 struct pipe_buffer *buf = pipe_buf(pipe, head - 1); 328 if (buf->page == page) { 329 buf->len += bytes; 330 i->last_offset -= bytes; 331 i->count -= bytes; 332 return bytes; 333 } 334 } 335 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) 336 return 0; 337 338 push_page(pipe, page, offset, bytes); 339 i->last_offset = -(offset + bytes); 340 i->head = head; 341 i->count -= bytes; 342 return bytes; 343 } 344 345 /* 346 * fault_in_iov_iter_readable - fault in iov iterator for reading 347 * @i: iterator 348 * @size: maximum length 349 * 350 * Fault in one or more iovecs of the given iov_iter, to a maximum length of 351 * @size. For each iovec, fault in each page that constitutes the iovec. 352 * 353 * Returns the number of bytes not faulted in (like copy_to_user() and 354 * copy_from_user()). 355 * 356 * Always returns 0 for non-userspace iterators. 357 */ 358 size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size) 359 { 360 if (iter_is_ubuf(i)) { 361 size_t n = min(size, iov_iter_count(i)); 362 n -= fault_in_readable(i->ubuf + i->iov_offset, n); 363 return size - n; 364 } else if (iter_is_iovec(i)) { 365 size_t count = min(size, iov_iter_count(i)); 366 const struct iovec *p; 367 size_t skip; 368 369 size -= count; 370 for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) { 371 size_t len = min(count, p->iov_len - skip); 372 size_t ret; 373 374 if (unlikely(!len)) 375 continue; 376 ret = fault_in_readable(p->iov_base + skip, len); 377 count -= len - ret; 378 if (ret) 379 break; 380 } 381 return count + size; 382 } 383 return 0; 384 } 385 EXPORT_SYMBOL(fault_in_iov_iter_readable); 386 387 /* 388 * fault_in_iov_iter_writeable - fault in iov iterator for writing 389 * @i: iterator 390 * @size: maximum length 391 * 392 * Faults in the iterator using get_user_pages(), i.e., without triggering 393 * hardware page faults. This is primarily useful when we already know that 394 * some or all of the pages in @i aren't in memory. 395 * 396 * Returns the number of bytes not faulted in, like copy_to_user() and 397 * copy_from_user(). 398 * 399 * Always returns 0 for non-user-space iterators. 400 */ 401 size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size) 402 { 403 if (iter_is_ubuf(i)) { 404 size_t n = min(size, iov_iter_count(i)); 405 n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n); 406 return size - n; 407 } else if (iter_is_iovec(i)) { 408 size_t count = min(size, iov_iter_count(i)); 409 const struct iovec *p; 410 size_t skip; 411 412 size -= count; 413 for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) { 414 size_t len = min(count, p->iov_len - skip); 415 size_t ret; 416 417 if (unlikely(!len)) 418 continue; 419 ret = fault_in_safe_writeable(p->iov_base + skip, len); 420 count -= len - ret; 421 if (ret) 422 break; 423 } 424 return count + size; 425 } 426 return 0; 427 } 428 EXPORT_SYMBOL(fault_in_iov_iter_writeable); 429 430 void iov_iter_init(struct iov_iter *i, unsigned int direction, 431 const struct iovec *iov, unsigned long nr_segs, 432 size_t count) 433 { 434 WARN_ON(direction & ~(READ | WRITE)); 435 *i = (struct iov_iter) { 436 .iter_type = ITER_IOVEC, 437 .nofault = false, 438 .user_backed = true, 439 .data_source = direction, 440 .__iov = iov, 441 .nr_segs = nr_segs, 442 .iov_offset = 0, 443 .count = count 444 }; 445 } 446 EXPORT_SYMBOL(iov_iter_init); 447 448 // returns the offset in partial buffer (if any) 449 static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages) 450 { 451 struct pipe_inode_info *pipe = i->pipe; 452 int used = pipe->head - pipe->tail; 453 int off = i->last_offset; 454 455 *npages = max((int)pipe->max_usage - used, 0); 456 457 if (off > 0 && off < PAGE_SIZE) { // anon and not full 458 (*npages)++; 459 return off; 460 } 461 return 0; 462 } 463 464 static size_t copy_pipe_to_iter(const void *addr, size_t bytes, 465 struct iov_iter *i) 466 { 467 unsigned int off, chunk; 468 469 if (unlikely(bytes > i->count)) 470 bytes = i->count; 471 if (unlikely(!bytes)) 472 return 0; 473 474 if (!sanity(i)) 475 return 0; 476 477 for (size_t n = bytes; n; n -= chunk) { 478 struct page *page = append_pipe(i, n, &off); 479 chunk = min_t(size_t, n, PAGE_SIZE - off); 480 if (!page) 481 return bytes - n; 482 memcpy_to_page(page, off, addr, chunk); 483 addr += chunk; 484 } 485 return bytes; 486 } 487 488 static __wsum csum_and_memcpy(void *to, const void *from, size_t len, 489 __wsum sum, size_t off) 490 { 491 __wsum next = csum_partial_copy_nocheck(from, to, len); 492 return csum_block_add(sum, next, off); 493 } 494 495 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes, 496 struct iov_iter *i, __wsum *sump) 497 { 498 __wsum sum = *sump; 499 size_t off = 0; 500 unsigned int chunk, r; 501 502 if (unlikely(bytes > i->count)) 503 bytes = i->count; 504 if (unlikely(!bytes)) 505 return 0; 506 507 if (!sanity(i)) 508 return 0; 509 510 while (bytes) { 511 struct page *page = append_pipe(i, bytes, &r); 512 char *p; 513 514 if (!page) 515 break; 516 chunk = min_t(size_t, bytes, PAGE_SIZE - r); 517 p = kmap_local_page(page); 518 sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off); 519 kunmap_local(p); 520 off += chunk; 521 bytes -= chunk; 522 } 523 *sump = sum; 524 return off; 525 } 526 527 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) 528 { 529 if (WARN_ON_ONCE(i->data_source)) 530 return 0; 531 if (unlikely(iov_iter_is_pipe(i))) 532 return copy_pipe_to_iter(addr, bytes, i); 533 if (user_backed_iter(i)) 534 might_fault(); 535 iterate_and_advance(i, bytes, base, len, off, 536 copyout(base, addr + off, len), 537 memcpy(base, addr + off, len) 538 ) 539 540 return bytes; 541 } 542 EXPORT_SYMBOL(_copy_to_iter); 543 544 #ifdef CONFIG_ARCH_HAS_COPY_MC 545 static int copyout_mc(void __user *to, const void *from, size_t n) 546 { 547 if (access_ok(to, n)) { 548 instrument_copy_to_user(to, from, n); 549 n = copy_mc_to_user((__force void *) to, from, n); 550 } 551 return n; 552 } 553 554 static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes, 555 struct iov_iter *i) 556 { 557 size_t xfer = 0; 558 unsigned int off, chunk; 559 560 if (unlikely(bytes > i->count)) 561 bytes = i->count; 562 if (unlikely(!bytes)) 563 return 0; 564 565 if (!sanity(i)) 566 return 0; 567 568 while (bytes) { 569 struct page *page = append_pipe(i, bytes, &off); 570 unsigned long rem; 571 char *p; 572 573 if (!page) 574 break; 575 chunk = min_t(size_t, bytes, PAGE_SIZE - off); 576 p = kmap_local_page(page); 577 rem = copy_mc_to_kernel(p + off, addr + xfer, chunk); 578 chunk -= rem; 579 kunmap_local(p); 580 xfer += chunk; 581 bytes -= chunk; 582 if (rem) { 583 iov_iter_revert(i, rem); 584 break; 585 } 586 } 587 return xfer; 588 } 589 590 /** 591 * _copy_mc_to_iter - copy to iter with source memory error exception handling 592 * @addr: source kernel address 593 * @bytes: total transfer length 594 * @i: destination iterator 595 * 596 * The pmem driver deploys this for the dax operation 597 * (dax_copy_to_iter()) for dax reads (bypass page-cache and the 598 * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes 599 * successfully copied. 600 * 601 * The main differences between this and typical _copy_to_iter(). 602 * 603 * * Typical tail/residue handling after a fault retries the copy 604 * byte-by-byte until the fault happens again. Re-triggering machine 605 * checks is potentially fatal so the implementation uses source 606 * alignment and poison alignment assumptions to avoid re-triggering 607 * hardware exceptions. 608 * 609 * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies. 610 * Compare to copy_to_iter() where only ITER_IOVEC attempts might return 611 * a short copy. 612 * 613 * Return: number of bytes copied (may be %0) 614 */ 615 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i) 616 { 617 if (WARN_ON_ONCE(i->data_source)) 618 return 0; 619 if (unlikely(iov_iter_is_pipe(i))) 620 return copy_mc_pipe_to_iter(addr, bytes, i); 621 if (user_backed_iter(i)) 622 might_fault(); 623 __iterate_and_advance(i, bytes, base, len, off, 624 copyout_mc(base, addr + off, len), 625 copy_mc_to_kernel(base, addr + off, len) 626 ) 627 628 return bytes; 629 } 630 EXPORT_SYMBOL_GPL(_copy_mc_to_iter); 631 #endif /* CONFIG_ARCH_HAS_COPY_MC */ 632 633 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) 634 { 635 if (WARN_ON_ONCE(!i->data_source)) 636 return 0; 637 638 if (user_backed_iter(i)) 639 might_fault(); 640 iterate_and_advance(i, bytes, base, len, off, 641 copyin(addr + off, base, len), 642 memcpy(addr + off, base, len) 643 ) 644 645 return bytes; 646 } 647 EXPORT_SYMBOL(_copy_from_iter); 648 649 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i) 650 { 651 if (WARN_ON_ONCE(!i->data_source)) 652 return 0; 653 654 iterate_and_advance(i, bytes, base, len, off, 655 __copy_from_user_inatomic_nocache(addr + off, base, len), 656 memcpy(addr + off, base, len) 657 ) 658 659 return bytes; 660 } 661 EXPORT_SYMBOL(_copy_from_iter_nocache); 662 663 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE 664 /** 665 * _copy_from_iter_flushcache - write destination through cpu cache 666 * @addr: destination kernel address 667 * @bytes: total transfer length 668 * @i: source iterator 669 * 670 * The pmem driver arranges for filesystem-dax to use this facility via 671 * dax_copy_from_iter() for ensuring that writes to persistent memory 672 * are flushed through the CPU cache. It is differentiated from 673 * _copy_from_iter_nocache() in that guarantees all data is flushed for 674 * all iterator types. The _copy_from_iter_nocache() only attempts to 675 * bypass the cache for the ITER_IOVEC case, and on some archs may use 676 * instructions that strand dirty-data in the cache. 677 * 678 * Return: number of bytes copied (may be %0) 679 */ 680 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i) 681 { 682 if (WARN_ON_ONCE(!i->data_source)) 683 return 0; 684 685 iterate_and_advance(i, bytes, base, len, off, 686 __copy_from_user_flushcache(addr + off, base, len), 687 memcpy_flushcache(addr + off, base, len) 688 ) 689 690 return bytes; 691 } 692 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache); 693 #endif 694 695 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n) 696 { 697 struct page *head; 698 size_t v = n + offset; 699 700 /* 701 * The general case needs to access the page order in order 702 * to compute the page size. 703 * However, we mostly deal with order-0 pages and thus can 704 * avoid a possible cache line miss for requests that fit all 705 * page orders. 706 */ 707 if (n <= v && v <= PAGE_SIZE) 708 return true; 709 710 head = compound_head(page); 711 v += (page - head) << PAGE_SHIFT; 712 713 if (WARN_ON(n > v || v > page_size(head))) 714 return false; 715 return true; 716 } 717 718 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, 719 struct iov_iter *i) 720 { 721 size_t res = 0; 722 if (!page_copy_sane(page, offset, bytes)) 723 return 0; 724 if (WARN_ON_ONCE(i->data_source)) 725 return 0; 726 if (unlikely(iov_iter_is_pipe(i))) 727 return copy_page_to_iter_pipe(page, offset, bytes, i); 728 page += offset / PAGE_SIZE; // first subpage 729 offset %= PAGE_SIZE; 730 while (1) { 731 void *kaddr = kmap_local_page(page); 732 size_t n = min(bytes, (size_t)PAGE_SIZE - offset); 733 n = _copy_to_iter(kaddr + offset, n, i); 734 kunmap_local(kaddr); 735 res += n; 736 bytes -= n; 737 if (!bytes || !n) 738 break; 739 offset += n; 740 if (offset == PAGE_SIZE) { 741 page++; 742 offset = 0; 743 } 744 } 745 return res; 746 } 747 EXPORT_SYMBOL(copy_page_to_iter); 748 749 size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes, 750 struct iov_iter *i) 751 { 752 size_t res = 0; 753 754 if (!page_copy_sane(page, offset, bytes)) 755 return 0; 756 if (WARN_ON_ONCE(i->data_source)) 757 return 0; 758 if (unlikely(iov_iter_is_pipe(i))) 759 return copy_page_to_iter_pipe(page, offset, bytes, i); 760 page += offset / PAGE_SIZE; // first subpage 761 offset %= PAGE_SIZE; 762 while (1) { 763 void *kaddr = kmap_local_page(page); 764 size_t n = min(bytes, (size_t)PAGE_SIZE - offset); 765 766 iterate_and_advance(i, n, base, len, off, 767 copyout_nofault(base, kaddr + offset + off, len), 768 memcpy(base, kaddr + offset + off, len) 769 ) 770 kunmap_local(kaddr); 771 res += n; 772 bytes -= n; 773 if (!bytes || !n) 774 break; 775 offset += n; 776 if (offset == PAGE_SIZE) { 777 page++; 778 offset = 0; 779 } 780 } 781 return res; 782 } 783 EXPORT_SYMBOL(copy_page_to_iter_nofault); 784 785 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, 786 struct iov_iter *i) 787 { 788 size_t res = 0; 789 if (!page_copy_sane(page, offset, bytes)) 790 return 0; 791 page += offset / PAGE_SIZE; // first subpage 792 offset %= PAGE_SIZE; 793 while (1) { 794 void *kaddr = kmap_local_page(page); 795 size_t n = min(bytes, (size_t)PAGE_SIZE - offset); 796 n = _copy_from_iter(kaddr + offset, n, i); 797 kunmap_local(kaddr); 798 res += n; 799 bytes -= n; 800 if (!bytes || !n) 801 break; 802 offset += n; 803 if (offset == PAGE_SIZE) { 804 page++; 805 offset = 0; 806 } 807 } 808 return res; 809 } 810 EXPORT_SYMBOL(copy_page_from_iter); 811 812 static size_t pipe_zero(size_t bytes, struct iov_iter *i) 813 { 814 unsigned int chunk, off; 815 816 if (unlikely(bytes > i->count)) 817 bytes = i->count; 818 if (unlikely(!bytes)) 819 return 0; 820 821 if (!sanity(i)) 822 return 0; 823 824 for (size_t n = bytes; n; n -= chunk) { 825 struct page *page = append_pipe(i, n, &off); 826 char *p; 827 828 if (!page) 829 return bytes - n; 830 chunk = min_t(size_t, n, PAGE_SIZE - off); 831 p = kmap_local_page(page); 832 memset(p + off, 0, chunk); 833 kunmap_local(p); 834 } 835 return bytes; 836 } 837 838 size_t iov_iter_zero(size_t bytes, struct iov_iter *i) 839 { 840 if (unlikely(iov_iter_is_pipe(i))) 841 return pipe_zero(bytes, i); 842 iterate_and_advance(i, bytes, base, len, count, 843 clear_user(base, len), 844 memset(base, 0, len) 845 ) 846 847 return bytes; 848 } 849 EXPORT_SYMBOL(iov_iter_zero); 850 851 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes, 852 struct iov_iter *i) 853 { 854 char *kaddr = kmap_atomic(page), *p = kaddr + offset; 855 if (!page_copy_sane(page, offset, bytes)) { 856 kunmap_atomic(kaddr); 857 return 0; 858 } 859 if (WARN_ON_ONCE(!i->data_source)) { 860 kunmap_atomic(kaddr); 861 return 0; 862 } 863 iterate_and_advance(i, bytes, base, len, off, 864 copyin(p + off, base, len), 865 memcpy(p + off, base, len) 866 ) 867 kunmap_atomic(kaddr); 868 return bytes; 869 } 870 EXPORT_SYMBOL(copy_page_from_iter_atomic); 871 872 static void pipe_advance(struct iov_iter *i, size_t size) 873 { 874 struct pipe_inode_info *pipe = i->pipe; 875 int off = i->last_offset; 876 877 if (!off && !size) { 878 pipe_discard_from(pipe, i->start_head); // discard everything 879 return; 880 } 881 i->count -= size; 882 while (1) { 883 struct pipe_buffer *buf = pipe_buf(pipe, i->head); 884 if (off) /* make it relative to the beginning of buffer */ 885 size += abs(off) - buf->offset; 886 if (size <= buf->len) { 887 buf->len = size; 888 i->last_offset = last_offset(buf); 889 break; 890 } 891 size -= buf->len; 892 i->head++; 893 off = 0; 894 } 895 pipe_discard_from(pipe, i->head + 1); // discard everything past this one 896 } 897 898 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size) 899 { 900 const struct bio_vec *bvec, *end; 901 902 if (!i->count) 903 return; 904 i->count -= size; 905 906 size += i->iov_offset; 907 908 for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) { 909 if (likely(size < bvec->bv_len)) 910 break; 911 size -= bvec->bv_len; 912 } 913 i->iov_offset = size; 914 i->nr_segs -= bvec - i->bvec; 915 i->bvec = bvec; 916 } 917 918 static void iov_iter_iovec_advance(struct iov_iter *i, size_t size) 919 { 920 const struct iovec *iov, *end; 921 922 if (!i->count) 923 return; 924 i->count -= size; 925 926 size += i->iov_offset; // from beginning of current segment 927 for (iov = iter_iov(i), end = iov + i->nr_segs; iov < end; iov++) { 928 if (likely(size < iov->iov_len)) 929 break; 930 size -= iov->iov_len; 931 } 932 i->iov_offset = size; 933 i->nr_segs -= iov - iter_iov(i); 934 i->__iov = iov; 935 } 936 937 void iov_iter_advance(struct iov_iter *i, size_t size) 938 { 939 if (unlikely(i->count < size)) 940 size = i->count; 941 if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) { 942 i->iov_offset += size; 943 i->count -= size; 944 } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) { 945 /* iovec and kvec have identical layouts */ 946 iov_iter_iovec_advance(i, size); 947 } else if (iov_iter_is_bvec(i)) { 948 iov_iter_bvec_advance(i, size); 949 } else if (iov_iter_is_pipe(i)) { 950 pipe_advance(i, size); 951 } else if (iov_iter_is_discard(i)) { 952 i->count -= size; 953 } 954 } 955 EXPORT_SYMBOL(iov_iter_advance); 956 957 void iov_iter_revert(struct iov_iter *i, size_t unroll) 958 { 959 if (!unroll) 960 return; 961 if (WARN_ON(unroll > MAX_RW_COUNT)) 962 return; 963 i->count += unroll; 964 if (unlikely(iov_iter_is_pipe(i))) { 965 struct pipe_inode_info *pipe = i->pipe; 966 unsigned int head = pipe->head; 967 968 while (head > i->start_head) { 969 struct pipe_buffer *b = pipe_buf(pipe, --head); 970 if (unroll < b->len) { 971 b->len -= unroll; 972 i->last_offset = last_offset(b); 973 i->head = head; 974 return; 975 } 976 unroll -= b->len; 977 pipe_buf_release(pipe, b); 978 pipe->head--; 979 } 980 i->last_offset = 0; 981 i->head = head; 982 return; 983 } 984 if (unlikely(iov_iter_is_discard(i))) 985 return; 986 if (unroll <= i->iov_offset) { 987 i->iov_offset -= unroll; 988 return; 989 } 990 unroll -= i->iov_offset; 991 if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) { 992 BUG(); /* We should never go beyond the start of the specified 993 * range since we might then be straying into pages that 994 * aren't pinned. 995 */ 996 } else if (iov_iter_is_bvec(i)) { 997 const struct bio_vec *bvec = i->bvec; 998 while (1) { 999 size_t n = (--bvec)->bv_len; 1000 i->nr_segs++; 1001 if (unroll <= n) { 1002 i->bvec = bvec; 1003 i->iov_offset = n - unroll; 1004 return; 1005 } 1006 unroll -= n; 1007 } 1008 } else { /* same logics for iovec and kvec */ 1009 const struct iovec *iov = iter_iov(i); 1010 while (1) { 1011 size_t n = (--iov)->iov_len; 1012 i->nr_segs++; 1013 if (unroll <= n) { 1014 i->__iov = iov; 1015 i->iov_offset = n - unroll; 1016 return; 1017 } 1018 unroll -= n; 1019 } 1020 } 1021 } 1022 EXPORT_SYMBOL(iov_iter_revert); 1023 1024 /* 1025 * Return the count of just the current iov_iter segment. 1026 */ 1027 size_t iov_iter_single_seg_count(const struct iov_iter *i) 1028 { 1029 if (i->nr_segs > 1) { 1030 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) 1031 return min(i->count, iter_iov(i)->iov_len - i->iov_offset); 1032 if (iov_iter_is_bvec(i)) 1033 return min(i->count, i->bvec->bv_len - i->iov_offset); 1034 } 1035 return i->count; 1036 } 1037 EXPORT_SYMBOL(iov_iter_single_seg_count); 1038 1039 void iov_iter_kvec(struct iov_iter *i, unsigned int direction, 1040 const struct kvec *kvec, unsigned long nr_segs, 1041 size_t count) 1042 { 1043 WARN_ON(direction & ~(READ | WRITE)); 1044 *i = (struct iov_iter){ 1045 .iter_type = ITER_KVEC, 1046 .data_source = direction, 1047 .kvec = kvec, 1048 .nr_segs = nr_segs, 1049 .iov_offset = 0, 1050 .count = count 1051 }; 1052 } 1053 EXPORT_SYMBOL(iov_iter_kvec); 1054 1055 void iov_iter_bvec(struct iov_iter *i, unsigned int direction, 1056 const struct bio_vec *bvec, unsigned long nr_segs, 1057 size_t count) 1058 { 1059 WARN_ON(direction & ~(READ | WRITE)); 1060 *i = (struct iov_iter){ 1061 .iter_type = ITER_BVEC, 1062 .data_source = direction, 1063 .bvec = bvec, 1064 .nr_segs = nr_segs, 1065 .iov_offset = 0, 1066 .count = count 1067 }; 1068 } 1069 EXPORT_SYMBOL(iov_iter_bvec); 1070 1071 void iov_iter_pipe(struct iov_iter *i, unsigned int direction, 1072 struct pipe_inode_info *pipe, 1073 size_t count) 1074 { 1075 BUG_ON(direction != READ); 1076 WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size)); 1077 *i = (struct iov_iter){ 1078 .iter_type = ITER_PIPE, 1079 .data_source = false, 1080 .pipe = pipe, 1081 .head = pipe->head, 1082 .start_head = pipe->head, 1083 .last_offset = 0, 1084 .count = count 1085 }; 1086 } 1087 EXPORT_SYMBOL(iov_iter_pipe); 1088 1089 /** 1090 * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray 1091 * @i: The iterator to initialise. 1092 * @direction: The direction of the transfer. 1093 * @xarray: The xarray to access. 1094 * @start: The start file position. 1095 * @count: The size of the I/O buffer in bytes. 1096 * 1097 * Set up an I/O iterator to either draw data out of the pages attached to an 1098 * inode or to inject data into those pages. The pages *must* be prevented 1099 * from evaporation, either by taking a ref on them or locking them by the 1100 * caller. 1101 */ 1102 void iov_iter_xarray(struct iov_iter *i, unsigned int direction, 1103 struct xarray *xarray, loff_t start, size_t count) 1104 { 1105 BUG_ON(direction & ~1); 1106 *i = (struct iov_iter) { 1107 .iter_type = ITER_XARRAY, 1108 .data_source = direction, 1109 .xarray = xarray, 1110 .xarray_start = start, 1111 .count = count, 1112 .iov_offset = 0 1113 }; 1114 } 1115 EXPORT_SYMBOL(iov_iter_xarray); 1116 1117 /** 1118 * iov_iter_discard - Initialise an I/O iterator that discards data 1119 * @i: The iterator to initialise. 1120 * @direction: The direction of the transfer. 1121 * @count: The size of the I/O buffer in bytes. 1122 * 1123 * Set up an I/O iterator that just discards everything that's written to it. 1124 * It's only available as a READ iterator. 1125 */ 1126 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count) 1127 { 1128 BUG_ON(direction != READ); 1129 *i = (struct iov_iter){ 1130 .iter_type = ITER_DISCARD, 1131 .data_source = false, 1132 .count = count, 1133 .iov_offset = 0 1134 }; 1135 } 1136 EXPORT_SYMBOL(iov_iter_discard); 1137 1138 static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask, 1139 unsigned len_mask) 1140 { 1141 size_t size = i->count; 1142 size_t skip = i->iov_offset; 1143 unsigned k; 1144 1145 for (k = 0; k < i->nr_segs; k++, skip = 0) { 1146 const struct iovec *iov = iter_iov(i) + k; 1147 size_t len = iov->iov_len - skip; 1148 1149 if (len > size) 1150 len = size; 1151 if (len & len_mask) 1152 return false; 1153 if ((unsigned long)(iov->iov_base + skip) & addr_mask) 1154 return false; 1155 1156 size -= len; 1157 if (!size) 1158 break; 1159 } 1160 return true; 1161 } 1162 1163 static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask, 1164 unsigned len_mask) 1165 { 1166 size_t size = i->count; 1167 unsigned skip = i->iov_offset; 1168 unsigned k; 1169 1170 for (k = 0; k < i->nr_segs; k++, skip = 0) { 1171 size_t len = i->bvec[k].bv_len - skip; 1172 1173 if (len > size) 1174 len = size; 1175 if (len & len_mask) 1176 return false; 1177 if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask) 1178 return false; 1179 1180 size -= len; 1181 if (!size) 1182 break; 1183 } 1184 return true; 1185 } 1186 1187 /** 1188 * iov_iter_is_aligned() - Check if the addresses and lengths of each segments 1189 * are aligned to the parameters. 1190 * 1191 * @i: &struct iov_iter to restore 1192 * @addr_mask: bit mask to check against the iov element's addresses 1193 * @len_mask: bit mask to check against the iov element's lengths 1194 * 1195 * Return: false if any addresses or lengths intersect with the provided masks 1196 */ 1197 bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask, 1198 unsigned len_mask) 1199 { 1200 if (likely(iter_is_ubuf(i))) { 1201 if (i->count & len_mask) 1202 return false; 1203 if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask) 1204 return false; 1205 return true; 1206 } 1207 1208 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) 1209 return iov_iter_aligned_iovec(i, addr_mask, len_mask); 1210 1211 if (iov_iter_is_bvec(i)) 1212 return iov_iter_aligned_bvec(i, addr_mask, len_mask); 1213 1214 if (iov_iter_is_pipe(i)) { 1215 size_t size = i->count; 1216 1217 if (size & len_mask) 1218 return false; 1219 if (size && i->last_offset > 0) { 1220 if (i->last_offset & addr_mask) 1221 return false; 1222 } 1223 1224 return true; 1225 } 1226 1227 if (iov_iter_is_xarray(i)) { 1228 if (i->count & len_mask) 1229 return false; 1230 if ((i->xarray_start + i->iov_offset) & addr_mask) 1231 return false; 1232 } 1233 1234 return true; 1235 } 1236 EXPORT_SYMBOL_GPL(iov_iter_is_aligned); 1237 1238 static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i) 1239 { 1240 unsigned long res = 0; 1241 size_t size = i->count; 1242 size_t skip = i->iov_offset; 1243 unsigned k; 1244 1245 for (k = 0; k < i->nr_segs; k++, skip = 0) { 1246 const struct iovec *iov = iter_iov(i) + k; 1247 size_t len = iov->iov_len - skip; 1248 if (len) { 1249 res |= (unsigned long)iov->iov_base + skip; 1250 if (len > size) 1251 len = size; 1252 res |= len; 1253 size -= len; 1254 if (!size) 1255 break; 1256 } 1257 } 1258 return res; 1259 } 1260 1261 static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i) 1262 { 1263 unsigned res = 0; 1264 size_t size = i->count; 1265 unsigned skip = i->iov_offset; 1266 unsigned k; 1267 1268 for (k = 0; k < i->nr_segs; k++, skip = 0) { 1269 size_t len = i->bvec[k].bv_len - skip; 1270 res |= (unsigned long)i->bvec[k].bv_offset + skip; 1271 if (len > size) 1272 len = size; 1273 res |= len; 1274 size -= len; 1275 if (!size) 1276 break; 1277 } 1278 return res; 1279 } 1280 1281 unsigned long iov_iter_alignment(const struct iov_iter *i) 1282 { 1283 if (likely(iter_is_ubuf(i))) { 1284 size_t size = i->count; 1285 if (size) 1286 return ((unsigned long)i->ubuf + i->iov_offset) | size; 1287 return 0; 1288 } 1289 1290 /* iovec and kvec have identical layouts */ 1291 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) 1292 return iov_iter_alignment_iovec(i); 1293 1294 if (iov_iter_is_bvec(i)) 1295 return iov_iter_alignment_bvec(i); 1296 1297 if (iov_iter_is_pipe(i)) { 1298 size_t size = i->count; 1299 1300 if (size && i->last_offset > 0) 1301 return size | i->last_offset; 1302 return size; 1303 } 1304 1305 if (iov_iter_is_xarray(i)) 1306 return (i->xarray_start + i->iov_offset) | i->count; 1307 1308 return 0; 1309 } 1310 EXPORT_SYMBOL(iov_iter_alignment); 1311 1312 unsigned long iov_iter_gap_alignment(const struct iov_iter *i) 1313 { 1314 unsigned long res = 0; 1315 unsigned long v = 0; 1316 size_t size = i->count; 1317 unsigned k; 1318 1319 if (iter_is_ubuf(i)) 1320 return 0; 1321 1322 if (WARN_ON(!iter_is_iovec(i))) 1323 return ~0U; 1324 1325 for (k = 0; k < i->nr_segs; k++) { 1326 const struct iovec *iov = iter_iov(i) + k; 1327 if (iov->iov_len) { 1328 unsigned long base = (unsigned long)iov->iov_base; 1329 if (v) // if not the first one 1330 res |= base | v; // this start | previous end 1331 v = base + iov->iov_len; 1332 if (size <= iov->iov_len) 1333 break; 1334 size -= iov->iov_len; 1335 } 1336 } 1337 return res; 1338 } 1339 EXPORT_SYMBOL(iov_iter_gap_alignment); 1340 1341 static int want_pages_array(struct page ***res, size_t size, 1342 size_t start, unsigned int maxpages) 1343 { 1344 unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE); 1345 1346 if (count > maxpages) 1347 count = maxpages; 1348 WARN_ON(!count); // caller should've prevented that 1349 if (!*res) { 1350 *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL); 1351 if (!*res) 1352 return 0; 1353 } 1354 return count; 1355 } 1356 1357 static ssize_t pipe_get_pages(struct iov_iter *i, 1358 struct page ***pages, size_t maxsize, unsigned maxpages, 1359 size_t *start) 1360 { 1361 unsigned int npages, count, off, chunk; 1362 struct page **p; 1363 size_t left; 1364 1365 if (!sanity(i)) 1366 return -EFAULT; 1367 1368 *start = off = pipe_npages(i, &npages); 1369 if (!npages) 1370 return -EFAULT; 1371 count = want_pages_array(pages, maxsize, off, min(npages, maxpages)); 1372 if (!count) 1373 return -ENOMEM; 1374 p = *pages; 1375 for (npages = 0, left = maxsize ; npages < count; npages++, left -= chunk) { 1376 struct page *page = append_pipe(i, left, &off); 1377 if (!page) 1378 break; 1379 chunk = min_t(size_t, left, PAGE_SIZE - off); 1380 get_page(*p++ = page); 1381 } 1382 if (!npages) 1383 return -EFAULT; 1384 return maxsize - left; 1385 } 1386 1387 static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa, 1388 pgoff_t index, unsigned int nr_pages) 1389 { 1390 XA_STATE(xas, xa, index); 1391 struct page *page; 1392 unsigned int ret = 0; 1393 1394 rcu_read_lock(); 1395 for (page = xas_load(&xas); page; page = xas_next(&xas)) { 1396 if (xas_retry(&xas, page)) 1397 continue; 1398 1399 /* Has the page moved or been split? */ 1400 if (unlikely(page != xas_reload(&xas))) { 1401 xas_reset(&xas); 1402 continue; 1403 } 1404 1405 pages[ret] = find_subpage(page, xas.xa_index); 1406 get_page(pages[ret]); 1407 if (++ret == nr_pages) 1408 break; 1409 } 1410 rcu_read_unlock(); 1411 return ret; 1412 } 1413 1414 static ssize_t iter_xarray_get_pages(struct iov_iter *i, 1415 struct page ***pages, size_t maxsize, 1416 unsigned maxpages, size_t *_start_offset) 1417 { 1418 unsigned nr, offset, count; 1419 pgoff_t index; 1420 loff_t pos; 1421 1422 pos = i->xarray_start + i->iov_offset; 1423 index = pos >> PAGE_SHIFT; 1424 offset = pos & ~PAGE_MASK; 1425 *_start_offset = offset; 1426 1427 count = want_pages_array(pages, maxsize, offset, maxpages); 1428 if (!count) 1429 return -ENOMEM; 1430 nr = iter_xarray_populate_pages(*pages, i->xarray, index, count); 1431 if (nr == 0) 1432 return 0; 1433 1434 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize); 1435 i->iov_offset += maxsize; 1436 i->count -= maxsize; 1437 return maxsize; 1438 } 1439 1440 /* must be done on non-empty ITER_UBUF or ITER_IOVEC one */ 1441 static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size) 1442 { 1443 size_t skip; 1444 long k; 1445 1446 if (iter_is_ubuf(i)) 1447 return (unsigned long)i->ubuf + i->iov_offset; 1448 1449 for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) { 1450 const struct iovec *iov = iter_iov(i) + k; 1451 size_t len = iov->iov_len - skip; 1452 1453 if (unlikely(!len)) 1454 continue; 1455 if (*size > len) 1456 *size = len; 1457 return (unsigned long)iov->iov_base + skip; 1458 } 1459 BUG(); // if it had been empty, we wouldn't get called 1460 } 1461 1462 /* must be done on non-empty ITER_BVEC one */ 1463 static struct page *first_bvec_segment(const struct iov_iter *i, 1464 size_t *size, size_t *start) 1465 { 1466 struct page *page; 1467 size_t skip = i->iov_offset, len; 1468 1469 len = i->bvec->bv_len - skip; 1470 if (*size > len) 1471 *size = len; 1472 skip += i->bvec->bv_offset; 1473 page = i->bvec->bv_page + skip / PAGE_SIZE; 1474 *start = skip % PAGE_SIZE; 1475 return page; 1476 } 1477 1478 static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, 1479 struct page ***pages, size_t maxsize, 1480 unsigned int maxpages, size_t *start, 1481 iov_iter_extraction_t extraction_flags) 1482 { 1483 unsigned int n, gup_flags = 0; 1484 1485 if (maxsize > i->count) 1486 maxsize = i->count; 1487 if (!maxsize) 1488 return 0; 1489 if (maxsize > MAX_RW_COUNT) 1490 maxsize = MAX_RW_COUNT; 1491 if (extraction_flags & ITER_ALLOW_P2PDMA) 1492 gup_flags |= FOLL_PCI_P2PDMA; 1493 1494 if (likely(user_backed_iter(i))) { 1495 unsigned long addr; 1496 int res; 1497 1498 if (iov_iter_rw(i) != WRITE) 1499 gup_flags |= FOLL_WRITE; 1500 if (i->nofault) 1501 gup_flags |= FOLL_NOFAULT; 1502 1503 addr = first_iovec_segment(i, &maxsize); 1504 *start = addr % PAGE_SIZE; 1505 addr &= PAGE_MASK; 1506 n = want_pages_array(pages, maxsize, *start, maxpages); 1507 if (!n) 1508 return -ENOMEM; 1509 res = get_user_pages_fast(addr, n, gup_flags, *pages); 1510 if (unlikely(res <= 0)) 1511 return res; 1512 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start); 1513 iov_iter_advance(i, maxsize); 1514 return maxsize; 1515 } 1516 if (iov_iter_is_bvec(i)) { 1517 struct page **p; 1518 struct page *page; 1519 1520 page = first_bvec_segment(i, &maxsize, start); 1521 n = want_pages_array(pages, maxsize, *start, maxpages); 1522 if (!n) 1523 return -ENOMEM; 1524 p = *pages; 1525 for (int k = 0; k < n; k++) 1526 get_page(p[k] = page + k); 1527 maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start); 1528 i->count -= maxsize; 1529 i->iov_offset += maxsize; 1530 if (i->iov_offset == i->bvec->bv_len) { 1531 i->iov_offset = 0; 1532 i->bvec++; 1533 i->nr_segs--; 1534 } 1535 return maxsize; 1536 } 1537 if (iov_iter_is_pipe(i)) 1538 return pipe_get_pages(i, pages, maxsize, maxpages, start); 1539 if (iov_iter_is_xarray(i)) 1540 return iter_xarray_get_pages(i, pages, maxsize, maxpages, start); 1541 return -EFAULT; 1542 } 1543 1544 ssize_t iov_iter_get_pages(struct iov_iter *i, 1545 struct page **pages, size_t maxsize, unsigned maxpages, 1546 size_t *start, iov_iter_extraction_t extraction_flags) 1547 { 1548 if (!maxpages) 1549 return 0; 1550 BUG_ON(!pages); 1551 1552 return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, 1553 start, extraction_flags); 1554 } 1555 EXPORT_SYMBOL_GPL(iov_iter_get_pages); 1556 1557 ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages, 1558 size_t maxsize, unsigned maxpages, size_t *start) 1559 { 1560 return iov_iter_get_pages(i, pages, maxsize, maxpages, start, 0); 1561 } 1562 EXPORT_SYMBOL(iov_iter_get_pages2); 1563 1564 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, 1565 struct page ***pages, size_t maxsize, 1566 size_t *start, iov_iter_extraction_t extraction_flags) 1567 { 1568 ssize_t len; 1569 1570 *pages = NULL; 1571 1572 len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start, 1573 extraction_flags); 1574 if (len <= 0) { 1575 kvfree(*pages); 1576 *pages = NULL; 1577 } 1578 return len; 1579 } 1580 EXPORT_SYMBOL_GPL(iov_iter_get_pages_alloc); 1581 1582 ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, 1583 struct page ***pages, size_t maxsize, size_t *start) 1584 { 1585 return iov_iter_get_pages_alloc(i, pages, maxsize, start, 0); 1586 } 1587 EXPORT_SYMBOL(iov_iter_get_pages_alloc2); 1588 1589 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, 1590 struct iov_iter *i) 1591 { 1592 __wsum sum, next; 1593 sum = *csum; 1594 if (WARN_ON_ONCE(!i->data_source)) 1595 return 0; 1596 1597 iterate_and_advance(i, bytes, base, len, off, ({ 1598 next = csum_and_copy_from_user(base, addr + off, len); 1599 sum = csum_block_add(sum, next, off); 1600 next ? 0 : len; 1601 }), ({ 1602 sum = csum_and_memcpy(addr + off, base, len, sum, off); 1603 }) 1604 ) 1605 *csum = sum; 1606 return bytes; 1607 } 1608 EXPORT_SYMBOL(csum_and_copy_from_iter); 1609 1610 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate, 1611 struct iov_iter *i) 1612 { 1613 struct csum_state *csstate = _csstate; 1614 __wsum sum, next; 1615 1616 if (WARN_ON_ONCE(i->data_source)) 1617 return 0; 1618 if (unlikely(iov_iter_is_discard(i))) { 1619 // can't use csum_memcpy() for that one - data is not copied 1620 csstate->csum = csum_block_add(csstate->csum, 1621 csum_partial(addr, bytes, 0), 1622 csstate->off); 1623 csstate->off += bytes; 1624 return bytes; 1625 } 1626 1627 sum = csum_shift(csstate->csum, csstate->off); 1628 if (unlikely(iov_iter_is_pipe(i))) 1629 bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum); 1630 else iterate_and_advance(i, bytes, base, len, off, ({ 1631 next = csum_and_copy_to_user(addr + off, base, len); 1632 sum = csum_block_add(sum, next, off); 1633 next ? 0 : len; 1634 }), ({ 1635 sum = csum_and_memcpy(base, addr + off, len, sum, off); 1636 }) 1637 ) 1638 csstate->csum = csum_shift(sum, csstate->off); 1639 csstate->off += bytes; 1640 return bytes; 1641 } 1642 EXPORT_SYMBOL(csum_and_copy_to_iter); 1643 1644 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp, 1645 struct iov_iter *i) 1646 { 1647 #ifdef CONFIG_CRYPTO_HASH 1648 struct ahash_request *hash = hashp; 1649 struct scatterlist sg; 1650 size_t copied; 1651 1652 copied = copy_to_iter(addr, bytes, i); 1653 sg_init_one(&sg, addr, copied); 1654 ahash_request_set_crypt(hash, &sg, NULL, copied); 1655 crypto_ahash_update(hash); 1656 return copied; 1657 #else 1658 return 0; 1659 #endif 1660 } 1661 EXPORT_SYMBOL(hash_and_copy_to_iter); 1662 1663 static int iov_npages(const struct iov_iter *i, int maxpages) 1664 { 1665 size_t skip = i->iov_offset, size = i->count; 1666 const struct iovec *p; 1667 int npages = 0; 1668 1669 for (p = iter_iov(i); size; skip = 0, p++) { 1670 unsigned offs = offset_in_page(p->iov_base + skip); 1671 size_t len = min(p->iov_len - skip, size); 1672 1673 if (len) { 1674 size -= len; 1675 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE); 1676 if (unlikely(npages > maxpages)) 1677 return maxpages; 1678 } 1679 } 1680 return npages; 1681 } 1682 1683 static int bvec_npages(const struct iov_iter *i, int maxpages) 1684 { 1685 size_t skip = i->iov_offset, size = i->count; 1686 const struct bio_vec *p; 1687 int npages = 0; 1688 1689 for (p = i->bvec; size; skip = 0, p++) { 1690 unsigned offs = (p->bv_offset + skip) % PAGE_SIZE; 1691 size_t len = min(p->bv_len - skip, size); 1692 1693 size -= len; 1694 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE); 1695 if (unlikely(npages > maxpages)) 1696 return maxpages; 1697 } 1698 return npages; 1699 } 1700 1701 int iov_iter_npages(const struct iov_iter *i, int maxpages) 1702 { 1703 if (unlikely(!i->count)) 1704 return 0; 1705 if (likely(iter_is_ubuf(i))) { 1706 unsigned offs = offset_in_page(i->ubuf + i->iov_offset); 1707 int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE); 1708 return min(npages, maxpages); 1709 } 1710 /* iovec and kvec have identical layouts */ 1711 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) 1712 return iov_npages(i, maxpages); 1713 if (iov_iter_is_bvec(i)) 1714 return bvec_npages(i, maxpages); 1715 if (iov_iter_is_pipe(i)) { 1716 int npages; 1717 1718 if (!sanity(i)) 1719 return 0; 1720 1721 pipe_npages(i, &npages); 1722 return min(npages, maxpages); 1723 } 1724 if (iov_iter_is_xarray(i)) { 1725 unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE; 1726 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE); 1727 return min(npages, maxpages); 1728 } 1729 return 0; 1730 } 1731 EXPORT_SYMBOL(iov_iter_npages); 1732 1733 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags) 1734 { 1735 *new = *old; 1736 if (unlikely(iov_iter_is_pipe(new))) { 1737 WARN_ON(1); 1738 return NULL; 1739 } 1740 if (iov_iter_is_bvec(new)) 1741 return new->bvec = kmemdup(new->bvec, 1742 new->nr_segs * sizeof(struct bio_vec), 1743 flags); 1744 else if (iov_iter_is_kvec(new) || iter_is_iovec(new)) 1745 /* iovec and kvec have identical layout */ 1746 return new->__iov = kmemdup(new->__iov, 1747 new->nr_segs * sizeof(struct iovec), 1748 flags); 1749 return NULL; 1750 } 1751 EXPORT_SYMBOL(dup_iter); 1752 1753 static __noclone int copy_compat_iovec_from_user(struct iovec *iov, 1754 const struct iovec __user *uvec, unsigned long nr_segs) 1755 { 1756 const struct compat_iovec __user *uiov = 1757 (const struct compat_iovec __user *)uvec; 1758 int ret = -EFAULT, i; 1759 1760 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) 1761 return -EFAULT; 1762 1763 for (i = 0; i < nr_segs; i++) { 1764 compat_uptr_t buf; 1765 compat_ssize_t len; 1766 1767 unsafe_get_user(len, &uiov[i].iov_len, uaccess_end); 1768 unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end); 1769 1770 /* check for compat_size_t not fitting in compat_ssize_t .. */ 1771 if (len < 0) { 1772 ret = -EINVAL; 1773 goto uaccess_end; 1774 } 1775 iov[i].iov_base = compat_ptr(buf); 1776 iov[i].iov_len = len; 1777 } 1778 1779 ret = 0; 1780 uaccess_end: 1781 user_access_end(); 1782 return ret; 1783 } 1784 1785 static int copy_iovec_from_user(struct iovec *iov, 1786 const struct iovec __user *uiov, unsigned long nr_segs) 1787 { 1788 int ret = -EFAULT; 1789 1790 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) 1791 return -EFAULT; 1792 1793 do { 1794 void __user *buf; 1795 ssize_t len; 1796 1797 unsafe_get_user(len, &uiov->iov_len, uaccess_end); 1798 unsafe_get_user(buf, &uiov->iov_base, uaccess_end); 1799 1800 /* check for size_t not fitting in ssize_t .. */ 1801 if (unlikely(len < 0)) { 1802 ret = -EINVAL; 1803 goto uaccess_end; 1804 } 1805 iov->iov_base = buf; 1806 iov->iov_len = len; 1807 1808 uiov++; iov++; 1809 } while (--nr_segs); 1810 1811 ret = 0; 1812 uaccess_end: 1813 user_access_end(); 1814 return ret; 1815 } 1816 1817 struct iovec *iovec_from_user(const struct iovec __user *uvec, 1818 unsigned long nr_segs, unsigned long fast_segs, 1819 struct iovec *fast_iov, bool compat) 1820 { 1821 struct iovec *iov = fast_iov; 1822 int ret; 1823 1824 /* 1825 * SuS says "The readv() function *may* fail if the iovcnt argument was 1826 * less than or equal to 0, or greater than {IOV_MAX}. Linux has 1827 * traditionally returned zero for zero segments, so... 1828 */ 1829 if (nr_segs == 0) 1830 return iov; 1831 if (nr_segs > UIO_MAXIOV) 1832 return ERR_PTR(-EINVAL); 1833 if (nr_segs > fast_segs) { 1834 iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL); 1835 if (!iov) 1836 return ERR_PTR(-ENOMEM); 1837 } 1838 1839 if (unlikely(compat)) 1840 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs); 1841 else 1842 ret = copy_iovec_from_user(iov, uvec, nr_segs); 1843 if (ret) { 1844 if (iov != fast_iov) 1845 kfree(iov); 1846 return ERR_PTR(ret); 1847 } 1848 1849 return iov; 1850 } 1851 1852 /* 1853 * Single segment iovec supplied by the user, import it as ITER_UBUF. 1854 */ 1855 static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec, 1856 struct iovec **iovp, struct iov_iter *i, 1857 bool compat) 1858 { 1859 struct iovec *iov = *iovp; 1860 ssize_t ret; 1861 1862 if (compat) 1863 ret = copy_compat_iovec_from_user(iov, uvec, 1); 1864 else 1865 ret = copy_iovec_from_user(iov, uvec, 1); 1866 if (unlikely(ret)) 1867 return ret; 1868 1869 ret = import_ubuf(type, iov->iov_base, iov->iov_len, i); 1870 if (unlikely(ret)) 1871 return ret; 1872 *iovp = NULL; 1873 return i->count; 1874 } 1875 1876 ssize_t __import_iovec(int type, const struct iovec __user *uvec, 1877 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp, 1878 struct iov_iter *i, bool compat) 1879 { 1880 ssize_t total_len = 0; 1881 unsigned long seg; 1882 struct iovec *iov; 1883 1884 if (nr_segs == 1) 1885 return __import_iovec_ubuf(type, uvec, iovp, i, compat); 1886 1887 iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat); 1888 if (IS_ERR(iov)) { 1889 *iovp = NULL; 1890 return PTR_ERR(iov); 1891 } 1892 1893 /* 1894 * According to the Single Unix Specification we should return EINVAL if 1895 * an element length is < 0 when cast to ssize_t or if the total length 1896 * would overflow the ssize_t return value of the system call. 1897 * 1898 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the 1899 * overflow case. 1900 */ 1901 for (seg = 0; seg < nr_segs; seg++) { 1902 ssize_t len = (ssize_t)iov[seg].iov_len; 1903 1904 if (!access_ok(iov[seg].iov_base, len)) { 1905 if (iov != *iovp) 1906 kfree(iov); 1907 *iovp = NULL; 1908 return -EFAULT; 1909 } 1910 1911 if (len > MAX_RW_COUNT - total_len) { 1912 len = MAX_RW_COUNT - total_len; 1913 iov[seg].iov_len = len; 1914 } 1915 total_len += len; 1916 } 1917 1918 iov_iter_init(i, type, iov, nr_segs, total_len); 1919 if (iov == *iovp) 1920 *iovp = NULL; 1921 else 1922 *iovp = iov; 1923 return total_len; 1924 } 1925 1926 /** 1927 * import_iovec() - Copy an array of &struct iovec from userspace 1928 * into the kernel, check that it is valid, and initialize a new 1929 * &struct iov_iter iterator to access it. 1930 * 1931 * @type: One of %READ or %WRITE. 1932 * @uvec: Pointer to the userspace array. 1933 * @nr_segs: Number of elements in userspace array. 1934 * @fast_segs: Number of elements in @iov. 1935 * @iovp: (input and output parameter) Pointer to pointer to (usually small 1936 * on-stack) kernel array. 1937 * @i: Pointer to iterator that will be initialized on success. 1938 * 1939 * If the array pointed to by *@iov is large enough to hold all @nr_segs, 1940 * then this function places %NULL in *@iov on return. Otherwise, a new 1941 * array will be allocated and the result placed in *@iov. This means that 1942 * the caller may call kfree() on *@iov regardless of whether the small 1943 * on-stack array was used or not (and regardless of whether this function 1944 * returns an error or not). 1945 * 1946 * Return: Negative error code on error, bytes imported on success 1947 */ 1948 ssize_t import_iovec(int type, const struct iovec __user *uvec, 1949 unsigned nr_segs, unsigned fast_segs, 1950 struct iovec **iovp, struct iov_iter *i) 1951 { 1952 return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i, 1953 in_compat_syscall()); 1954 } 1955 EXPORT_SYMBOL(import_iovec); 1956 1957 int import_single_range(int rw, void __user *buf, size_t len, 1958 struct iovec *iov, struct iov_iter *i) 1959 { 1960 if (len > MAX_RW_COUNT) 1961 len = MAX_RW_COUNT; 1962 if (unlikely(!access_ok(buf, len))) 1963 return -EFAULT; 1964 1965 iov_iter_ubuf(i, rw, buf, len); 1966 return 0; 1967 } 1968 EXPORT_SYMBOL(import_single_range); 1969 1970 int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i) 1971 { 1972 if (len > MAX_RW_COUNT) 1973 len = MAX_RW_COUNT; 1974 if (unlikely(!access_ok(buf, len))) 1975 return -EFAULT; 1976 1977 iov_iter_ubuf(i, rw, buf, len); 1978 return 0; 1979 } 1980 1981 /** 1982 * iov_iter_restore() - Restore a &struct iov_iter to the same state as when 1983 * iov_iter_save_state() was called. 1984 * 1985 * @i: &struct iov_iter to restore 1986 * @state: state to restore from 1987 * 1988 * Used after iov_iter_save_state() to bring restore @i, if operations may 1989 * have advanced it. 1990 * 1991 * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC 1992 */ 1993 void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state) 1994 { 1995 if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) && 1996 !iter_is_ubuf(i)) && !iov_iter_is_kvec(i)) 1997 return; 1998 i->iov_offset = state->iov_offset; 1999 i->count = state->count; 2000 if (iter_is_ubuf(i)) 2001 return; 2002 /* 2003 * For the *vec iters, nr_segs + iov is constant - if we increment 2004 * the vec, then we also decrement the nr_segs count. Hence we don't 2005 * need to track both of these, just one is enough and we can deduct 2006 * the other from that. ITER_KVEC and ITER_IOVEC are the same struct 2007 * size, so we can just increment the iov pointer as they are unionzed. 2008 * ITER_BVEC _may_ be the same size on some archs, but on others it is 2009 * not. Be safe and handle it separately. 2010 */ 2011 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec)); 2012 if (iov_iter_is_bvec(i)) 2013 i->bvec -= state->nr_segs - i->nr_segs; 2014 else 2015 i->__iov -= state->nr_segs - i->nr_segs; 2016 i->nr_segs = state->nr_segs; 2017 } 2018 2019 /* 2020 * Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not 2021 * get references on the pages, nor does it get a pin on them. 2022 */ 2023 static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i, 2024 struct page ***pages, size_t maxsize, 2025 unsigned int maxpages, 2026 iov_iter_extraction_t extraction_flags, 2027 size_t *offset0) 2028 { 2029 struct page *page, **p; 2030 unsigned int nr = 0, offset; 2031 loff_t pos = i->xarray_start + i->iov_offset; 2032 pgoff_t index = pos >> PAGE_SHIFT; 2033 XA_STATE(xas, i->xarray, index); 2034 2035 offset = pos & ~PAGE_MASK; 2036 *offset0 = offset; 2037 2038 maxpages = want_pages_array(pages, maxsize, offset, maxpages); 2039 if (!maxpages) 2040 return -ENOMEM; 2041 p = *pages; 2042 2043 rcu_read_lock(); 2044 for (page = xas_load(&xas); page; page = xas_next(&xas)) { 2045 if (xas_retry(&xas, page)) 2046 continue; 2047 2048 /* Has the page moved or been split? */ 2049 if (unlikely(page != xas_reload(&xas))) { 2050 xas_reset(&xas); 2051 continue; 2052 } 2053 2054 p[nr++] = find_subpage(page, xas.xa_index); 2055 if (nr == maxpages) 2056 break; 2057 } 2058 rcu_read_unlock(); 2059 2060 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize); 2061 iov_iter_advance(i, maxsize); 2062 return maxsize; 2063 } 2064 2065 /* 2066 * Extract a list of contiguous pages from an ITER_BVEC iterator. This does 2067 * not get references on the pages, nor does it get a pin on them. 2068 */ 2069 static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i, 2070 struct page ***pages, size_t maxsize, 2071 unsigned int maxpages, 2072 iov_iter_extraction_t extraction_flags, 2073 size_t *offset0) 2074 { 2075 struct page **p, *page; 2076 size_t skip = i->iov_offset, offset; 2077 int k; 2078 2079 for (;;) { 2080 if (i->nr_segs == 0) 2081 return 0; 2082 maxsize = min(maxsize, i->bvec->bv_len - skip); 2083 if (maxsize) 2084 break; 2085 i->iov_offset = 0; 2086 i->nr_segs--; 2087 i->bvec++; 2088 skip = 0; 2089 } 2090 2091 skip += i->bvec->bv_offset; 2092 page = i->bvec->bv_page + skip / PAGE_SIZE; 2093 offset = skip % PAGE_SIZE; 2094 *offset0 = offset; 2095 2096 maxpages = want_pages_array(pages, maxsize, offset, maxpages); 2097 if (!maxpages) 2098 return -ENOMEM; 2099 p = *pages; 2100 for (k = 0; k < maxpages; k++) 2101 p[k] = page + k; 2102 2103 maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); 2104 iov_iter_advance(i, maxsize); 2105 return maxsize; 2106 } 2107 2108 /* 2109 * Extract a list of virtually contiguous pages from an ITER_KVEC iterator. 2110 * This does not get references on the pages, nor does it get a pin on them. 2111 */ 2112 static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i, 2113 struct page ***pages, size_t maxsize, 2114 unsigned int maxpages, 2115 iov_iter_extraction_t extraction_flags, 2116 size_t *offset0) 2117 { 2118 struct page **p, *page; 2119 const void *kaddr; 2120 size_t skip = i->iov_offset, offset, len; 2121 int k; 2122 2123 for (;;) { 2124 if (i->nr_segs == 0) 2125 return 0; 2126 maxsize = min(maxsize, i->kvec->iov_len - skip); 2127 if (maxsize) 2128 break; 2129 i->iov_offset = 0; 2130 i->nr_segs--; 2131 i->kvec++; 2132 skip = 0; 2133 } 2134 2135 kaddr = i->kvec->iov_base + skip; 2136 offset = (unsigned long)kaddr & ~PAGE_MASK; 2137 *offset0 = offset; 2138 2139 maxpages = want_pages_array(pages, maxsize, offset, maxpages); 2140 if (!maxpages) 2141 return -ENOMEM; 2142 p = *pages; 2143 2144 kaddr -= offset; 2145 len = offset + maxsize; 2146 for (k = 0; k < maxpages; k++) { 2147 size_t seg = min_t(size_t, len, PAGE_SIZE); 2148 2149 if (is_vmalloc_or_module_addr(kaddr)) 2150 page = vmalloc_to_page(kaddr); 2151 else 2152 page = virt_to_page(kaddr); 2153 2154 p[k] = page; 2155 len -= seg; 2156 kaddr += PAGE_SIZE; 2157 } 2158 2159 maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); 2160 iov_iter_advance(i, maxsize); 2161 return maxsize; 2162 } 2163 2164 /* 2165 * Extract a list of contiguous pages from a user iterator and get a pin on 2166 * each of them. This should only be used if the iterator is user-backed 2167 * (IOBUF/UBUF). 2168 * 2169 * It does not get refs on the pages, but the pages must be unpinned by the 2170 * caller once the transfer is complete. 2171 * 2172 * This is safe to be used where background IO/DMA *is* going to be modifying 2173 * the buffer; using a pin rather than a ref makes forces fork() to give the 2174 * child a copy of the page. 2175 */ 2176 static ssize_t iov_iter_extract_user_pages(struct iov_iter *i, 2177 struct page ***pages, 2178 size_t maxsize, 2179 unsigned int maxpages, 2180 iov_iter_extraction_t extraction_flags, 2181 size_t *offset0) 2182 { 2183 unsigned long addr; 2184 unsigned int gup_flags = 0; 2185 size_t offset; 2186 int res; 2187 2188 if (i->data_source == ITER_DEST) 2189 gup_flags |= FOLL_WRITE; 2190 if (extraction_flags & ITER_ALLOW_P2PDMA) 2191 gup_flags |= FOLL_PCI_P2PDMA; 2192 if (i->nofault) 2193 gup_flags |= FOLL_NOFAULT; 2194 2195 addr = first_iovec_segment(i, &maxsize); 2196 *offset0 = offset = addr % PAGE_SIZE; 2197 addr &= PAGE_MASK; 2198 maxpages = want_pages_array(pages, maxsize, offset, maxpages); 2199 if (!maxpages) 2200 return -ENOMEM; 2201 res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages); 2202 if (unlikely(res <= 0)) 2203 return res; 2204 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset); 2205 iov_iter_advance(i, maxsize); 2206 return maxsize; 2207 } 2208 2209 /** 2210 * iov_iter_extract_pages - Extract a list of contiguous pages from an iterator 2211 * @i: The iterator to extract from 2212 * @pages: Where to return the list of pages 2213 * @maxsize: The maximum amount of iterator to extract 2214 * @maxpages: The maximum size of the list of pages 2215 * @extraction_flags: Flags to qualify request 2216 * @offset0: Where to return the starting offset into (*@pages)[0] 2217 * 2218 * Extract a list of contiguous pages from the current point of the iterator, 2219 * advancing the iterator. The maximum number of pages and the maximum amount 2220 * of page contents can be set. 2221 * 2222 * If *@pages is NULL, a page list will be allocated to the required size and 2223 * *@pages will be set to its base. If *@pages is not NULL, it will be assumed 2224 * that the caller allocated a page list at least @maxpages in size and this 2225 * will be filled in. 2226 * 2227 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA 2228 * be allowed on the pages extracted. 2229 * 2230 * The iov_iter_extract_will_pin() function can be used to query how cleanup 2231 * should be performed. 2232 * 2233 * Extra refs or pins on the pages may be obtained as follows: 2234 * 2235 * (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be 2236 * added to the pages, but refs will not be taken. 2237 * iov_iter_extract_will_pin() will return true. 2238 * 2239 * (*) If the iterator is ITER_KVEC, ITER_BVEC or ITER_XARRAY, the pages are 2240 * merely listed; no extra refs or pins are obtained. 2241 * iov_iter_extract_will_pin() will return 0. 2242 * 2243 * Note also: 2244 * 2245 * (*) Use with ITER_DISCARD is not supported as that has no content. 2246 * 2247 * On success, the function sets *@pages to the new pagelist, if allocated, and 2248 * sets *offset0 to the offset into the first page. 2249 * 2250 * It may also return -ENOMEM and -EFAULT. 2251 */ 2252 ssize_t iov_iter_extract_pages(struct iov_iter *i, 2253 struct page ***pages, 2254 size_t maxsize, 2255 unsigned int maxpages, 2256 iov_iter_extraction_t extraction_flags, 2257 size_t *offset0) 2258 { 2259 maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT); 2260 if (!maxsize) 2261 return 0; 2262 2263 if (likely(user_backed_iter(i))) 2264 return iov_iter_extract_user_pages(i, pages, maxsize, 2265 maxpages, extraction_flags, 2266 offset0); 2267 if (iov_iter_is_kvec(i)) 2268 return iov_iter_extract_kvec_pages(i, pages, maxsize, 2269 maxpages, extraction_flags, 2270 offset0); 2271 if (iov_iter_is_bvec(i)) 2272 return iov_iter_extract_bvec_pages(i, pages, maxsize, 2273 maxpages, extraction_flags, 2274 offset0); 2275 if (iov_iter_is_xarray(i)) 2276 return iov_iter_extract_xarray_pages(i, pages, maxsize, 2277 maxpages, extraction_flags, 2278 offset0); 2279 return -EFAULT; 2280 } 2281 EXPORT_SYMBOL_GPL(iov_iter_extract_pages); 2282