1 #include <linux/kernel.h> 2 #include <linux/errno.h> 3 #include <linux/err.h> 4 #include <linux/spinlock.h> 5 6 #include <linux/mm.h> 7 #include <linux/memremap.h> 8 #include <linux/pagemap.h> 9 #include <linux/rmap.h> 10 #include <linux/swap.h> 11 #include <linux/swapops.h> 12 13 #include <linux/sched.h> 14 #include <linux/rwsem.h> 15 #include <linux/hugetlb.h> 16 17 #include <asm/pgtable.h> 18 #include <asm/tlbflush.h> 19 20 #include "internal.h" 21 22 static struct page *no_page_table(struct vm_area_struct *vma, 23 unsigned int flags) 24 { 25 /* 26 * When core dumping an enormous anonymous area that nobody 27 * has touched so far, we don't want to allocate unnecessary pages or 28 * page tables. Return error instead of NULL to skip handle_mm_fault, 29 * then get_dump_page() will return NULL to leave a hole in the dump. 30 * But we can only make this optimization where a hole would surely 31 * be zero-filled if handle_mm_fault() actually did handle it. 32 */ 33 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault)) 34 return ERR_PTR(-EFAULT); 35 return NULL; 36 } 37 38 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, 39 pte_t *pte, unsigned int flags) 40 { 41 /* No page to get reference */ 42 if (flags & FOLL_GET) 43 return -EFAULT; 44 45 if (flags & FOLL_TOUCH) { 46 pte_t entry = *pte; 47 48 if (flags & FOLL_WRITE) 49 entry = pte_mkdirty(entry); 50 entry = pte_mkyoung(entry); 51 52 if (!pte_same(*pte, entry)) { 53 set_pte_at(vma->vm_mm, address, pte, entry); 54 update_mmu_cache(vma, address, pte); 55 } 56 } 57 58 /* Proper page table entry exists, but no corresponding struct page */ 59 return -EEXIST; 60 } 61 62 static struct page *follow_page_pte(struct vm_area_struct *vma, 63 unsigned long address, pmd_t *pmd, unsigned int flags) 64 { 65 struct mm_struct *mm = vma->vm_mm; 66 struct dev_pagemap *pgmap = NULL; 67 struct page *page; 68 spinlock_t *ptl; 69 pte_t *ptep, pte; 70 71 retry: 72 if (unlikely(pmd_bad(*pmd))) 73 return no_page_table(vma, flags); 74 75 ptep = pte_offset_map_lock(mm, pmd, address, &ptl); 76 pte = *ptep; 77 if (!pte_present(pte)) { 78 swp_entry_t entry; 79 /* 80 * KSM's break_ksm() relies upon recognizing a ksm page 81 * even while it is being migrated, so for that case we 82 * need migration_entry_wait(). 83 */ 84 if (likely(!(flags & FOLL_MIGRATION))) 85 goto no_page; 86 if (pte_none(pte)) 87 goto no_page; 88 entry = pte_to_swp_entry(pte); 89 if (!is_migration_entry(entry)) 90 goto no_page; 91 pte_unmap_unlock(ptep, ptl); 92 migration_entry_wait(mm, pmd, address); 93 goto retry; 94 } 95 if ((flags & FOLL_NUMA) && pte_protnone(pte)) 96 goto no_page; 97 if ((flags & FOLL_WRITE) && !pte_write(pte)) { 98 pte_unmap_unlock(ptep, ptl); 99 return NULL; 100 } 101 102 page = vm_normal_page(vma, address, pte); 103 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) { 104 /* 105 * Only return device mapping pages in the FOLL_GET case since 106 * they are only valid while holding the pgmap reference. 107 */ 108 pgmap = get_dev_pagemap(pte_pfn(pte), NULL); 109 if (pgmap) 110 page = pte_page(pte); 111 else 112 goto no_page; 113 } else if (unlikely(!page)) { 114 if (flags & FOLL_DUMP) { 115 /* Avoid special (like zero) pages in core dumps */ 116 page = ERR_PTR(-EFAULT); 117 goto out; 118 } 119 120 if (is_zero_pfn(pte_pfn(pte))) { 121 page = pte_page(pte); 122 } else { 123 int ret; 124 125 ret = follow_pfn_pte(vma, address, ptep, flags); 126 page = ERR_PTR(ret); 127 goto out; 128 } 129 } 130 131 if (flags & FOLL_SPLIT && PageTransCompound(page)) { 132 int ret; 133 get_page(page); 134 pte_unmap_unlock(ptep, ptl); 135 lock_page(page); 136 ret = split_huge_page(page); 137 unlock_page(page); 138 put_page(page); 139 if (ret) 140 return ERR_PTR(ret); 141 goto retry; 142 } 143 144 if (flags & FOLL_GET) { 145 get_page(page); 146 147 /* drop the pgmap reference now that we hold the page */ 148 if (pgmap) { 149 put_dev_pagemap(pgmap); 150 pgmap = NULL; 151 } 152 } 153 if (flags & FOLL_TOUCH) { 154 if ((flags & FOLL_WRITE) && 155 !pte_dirty(pte) && !PageDirty(page)) 156 set_page_dirty(page); 157 /* 158 * pte_mkyoung() would be more correct here, but atomic care 159 * is needed to avoid losing the dirty bit: it is easier to use 160 * mark_page_accessed(). 161 */ 162 mark_page_accessed(page); 163 } 164 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 165 /* Do not mlock pte-mapped THP */ 166 if (PageTransCompound(page)) 167 goto out; 168 169 /* 170 * The preliminary mapping check is mainly to avoid the 171 * pointless overhead of lock_page on the ZERO_PAGE 172 * which might bounce very badly if there is contention. 173 * 174 * If the page is already locked, we don't need to 175 * handle it now - vmscan will handle it later if and 176 * when it attempts to reclaim the page. 177 */ 178 if (page->mapping && trylock_page(page)) { 179 lru_add_drain(); /* push cached pages to LRU */ 180 /* 181 * Because we lock page here, and migration is 182 * blocked by the pte's page reference, and we 183 * know the page is still mapped, we don't even 184 * need to check for file-cache page truncation. 185 */ 186 mlock_vma_page(page); 187 unlock_page(page); 188 } 189 } 190 out: 191 pte_unmap_unlock(ptep, ptl); 192 return page; 193 no_page: 194 pte_unmap_unlock(ptep, ptl); 195 if (!pte_none(pte)) 196 return NULL; 197 return no_page_table(vma, flags); 198 } 199 200 /** 201 * follow_page_mask - look up a page descriptor from a user-virtual address 202 * @vma: vm_area_struct mapping @address 203 * @address: virtual address to look up 204 * @flags: flags modifying lookup behaviour 205 * @page_mask: on output, *page_mask is set according to the size of the page 206 * 207 * @flags can have FOLL_ flags set, defined in <linux/mm.h> 208 * 209 * Returns the mapped (struct page *), %NULL if no mapping exists, or 210 * an error pointer if there is a mapping to something not represented 211 * by a page descriptor (see also vm_normal_page()). 212 */ 213 struct page *follow_page_mask(struct vm_area_struct *vma, 214 unsigned long address, unsigned int flags, 215 unsigned int *page_mask) 216 { 217 pgd_t *pgd; 218 pud_t *pud; 219 pmd_t *pmd; 220 spinlock_t *ptl; 221 struct page *page; 222 struct mm_struct *mm = vma->vm_mm; 223 224 *page_mask = 0; 225 226 page = follow_huge_addr(mm, address, flags & FOLL_WRITE); 227 if (!IS_ERR(page)) { 228 BUG_ON(flags & FOLL_GET); 229 return page; 230 } 231 232 pgd = pgd_offset(mm, address); 233 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) 234 return no_page_table(vma, flags); 235 236 pud = pud_offset(pgd, address); 237 if (pud_none(*pud)) 238 return no_page_table(vma, flags); 239 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) { 240 page = follow_huge_pud(mm, address, pud, flags); 241 if (page) 242 return page; 243 return no_page_table(vma, flags); 244 } 245 if (unlikely(pud_bad(*pud))) 246 return no_page_table(vma, flags); 247 248 pmd = pmd_offset(pud, address); 249 if (pmd_none(*pmd)) 250 return no_page_table(vma, flags); 251 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) { 252 page = follow_huge_pmd(mm, address, pmd, flags); 253 if (page) 254 return page; 255 return no_page_table(vma, flags); 256 } 257 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 258 return no_page_table(vma, flags); 259 if (pmd_devmap(*pmd)) { 260 ptl = pmd_lock(mm, pmd); 261 page = follow_devmap_pmd(vma, address, pmd, flags); 262 spin_unlock(ptl); 263 if (page) 264 return page; 265 } 266 if (likely(!pmd_trans_huge(*pmd))) 267 return follow_page_pte(vma, address, pmd, flags); 268 269 ptl = pmd_lock(mm, pmd); 270 if (unlikely(!pmd_trans_huge(*pmd))) { 271 spin_unlock(ptl); 272 return follow_page_pte(vma, address, pmd, flags); 273 } 274 if (flags & FOLL_SPLIT) { 275 int ret; 276 page = pmd_page(*pmd); 277 if (is_huge_zero_page(page)) { 278 spin_unlock(ptl); 279 ret = 0; 280 split_huge_pmd(vma, pmd, address); 281 } else { 282 get_page(page); 283 spin_unlock(ptl); 284 lock_page(page); 285 ret = split_huge_page(page); 286 unlock_page(page); 287 put_page(page); 288 } 289 290 return ret ? ERR_PTR(ret) : 291 follow_page_pte(vma, address, pmd, flags); 292 } 293 294 page = follow_trans_huge_pmd(vma, address, pmd, flags); 295 spin_unlock(ptl); 296 *page_mask = HPAGE_PMD_NR - 1; 297 return page; 298 } 299 300 static int get_gate_page(struct mm_struct *mm, unsigned long address, 301 unsigned int gup_flags, struct vm_area_struct **vma, 302 struct page **page) 303 { 304 pgd_t *pgd; 305 pud_t *pud; 306 pmd_t *pmd; 307 pte_t *pte; 308 int ret = -EFAULT; 309 310 /* user gate pages are read-only */ 311 if (gup_flags & FOLL_WRITE) 312 return -EFAULT; 313 if (address > TASK_SIZE) 314 pgd = pgd_offset_k(address); 315 else 316 pgd = pgd_offset_gate(mm, address); 317 BUG_ON(pgd_none(*pgd)); 318 pud = pud_offset(pgd, address); 319 BUG_ON(pud_none(*pud)); 320 pmd = pmd_offset(pud, address); 321 if (pmd_none(*pmd)) 322 return -EFAULT; 323 VM_BUG_ON(pmd_trans_huge(*pmd)); 324 pte = pte_offset_map(pmd, address); 325 if (pte_none(*pte)) 326 goto unmap; 327 *vma = get_gate_vma(mm); 328 if (!page) 329 goto out; 330 *page = vm_normal_page(*vma, address, *pte); 331 if (!*page) { 332 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte))) 333 goto unmap; 334 *page = pte_page(*pte); 335 } 336 get_page(*page); 337 out: 338 ret = 0; 339 unmap: 340 pte_unmap(pte); 341 return ret; 342 } 343 344 /* 345 * mmap_sem must be held on entry. If @nonblocking != NULL and 346 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released. 347 * If it is, *@nonblocking will be set to 0 and -EBUSY returned. 348 */ 349 static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, 350 unsigned long address, unsigned int *flags, int *nonblocking) 351 { 352 struct mm_struct *mm = vma->vm_mm; 353 unsigned int fault_flags = 0; 354 int ret; 355 356 /* mlock all present pages, but do not fault in new pages */ 357 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) 358 return -ENOENT; 359 /* For mm_populate(), just skip the stack guard page. */ 360 if ((*flags & FOLL_POPULATE) && 361 (stack_guard_page_start(vma, address) || 362 stack_guard_page_end(vma, address + PAGE_SIZE))) 363 return -ENOENT; 364 if (*flags & FOLL_WRITE) 365 fault_flags |= FAULT_FLAG_WRITE; 366 if (nonblocking) 367 fault_flags |= FAULT_FLAG_ALLOW_RETRY; 368 if (*flags & FOLL_NOWAIT) 369 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; 370 if (*flags & FOLL_TRIED) { 371 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY); 372 fault_flags |= FAULT_FLAG_TRIED; 373 } 374 375 ret = handle_mm_fault(mm, vma, address, fault_flags); 376 if (ret & VM_FAULT_ERROR) { 377 if (ret & VM_FAULT_OOM) 378 return -ENOMEM; 379 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) 380 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT; 381 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV)) 382 return -EFAULT; 383 BUG(); 384 } 385 386 if (tsk) { 387 if (ret & VM_FAULT_MAJOR) 388 tsk->maj_flt++; 389 else 390 tsk->min_flt++; 391 } 392 393 if (ret & VM_FAULT_RETRY) { 394 if (nonblocking) 395 *nonblocking = 0; 396 return -EBUSY; 397 } 398 399 /* 400 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when 401 * necessary, even if maybe_mkwrite decided not to set pte_write. We 402 * can thus safely do subsequent page lookups as if they were reads. 403 * But only do so when looping for pte_write is futile: in some cases 404 * userspace may also be wanting to write to the gotten user page, 405 * which a read fault here might prevent (a readonly page might get 406 * reCOWed by userspace write). 407 */ 408 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) 409 *flags &= ~FOLL_WRITE; 410 return 0; 411 } 412 413 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) 414 { 415 vm_flags_t vm_flags = vma->vm_flags; 416 417 if (vm_flags & (VM_IO | VM_PFNMAP)) 418 return -EFAULT; 419 420 if (gup_flags & FOLL_WRITE) { 421 if (!(vm_flags & VM_WRITE)) { 422 if (!(gup_flags & FOLL_FORCE)) 423 return -EFAULT; 424 /* 425 * We used to let the write,force case do COW in a 426 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could 427 * set a breakpoint in a read-only mapping of an 428 * executable, without corrupting the file (yet only 429 * when that file had been opened for writing!). 430 * Anon pages in shared mappings are surprising: now 431 * just reject it. 432 */ 433 if (!is_cow_mapping(vm_flags)) 434 return -EFAULT; 435 } 436 } else if (!(vm_flags & VM_READ)) { 437 if (!(gup_flags & FOLL_FORCE)) 438 return -EFAULT; 439 /* 440 * Is there actually any vma we can reach here which does not 441 * have VM_MAYREAD set? 442 */ 443 if (!(vm_flags & VM_MAYREAD)) 444 return -EFAULT; 445 } 446 return 0; 447 } 448 449 /** 450 * __get_user_pages() - pin user pages in memory 451 * @tsk: task_struct of target task 452 * @mm: mm_struct of target mm 453 * @start: starting user address 454 * @nr_pages: number of pages from start to pin 455 * @gup_flags: flags modifying pin behaviour 456 * @pages: array that receives pointers to the pages pinned. 457 * Should be at least nr_pages long. Or NULL, if caller 458 * only intends to ensure the pages are faulted in. 459 * @vmas: array of pointers to vmas corresponding to each page. 460 * Or NULL if the caller does not require them. 461 * @nonblocking: whether waiting for disk IO or mmap_sem contention 462 * 463 * Returns number of pages pinned. This may be fewer than the number 464 * requested. If nr_pages is 0 or negative, returns 0. If no pages 465 * were pinned, returns -errno. Each page returned must be released 466 * with a put_page() call when it is finished with. vmas will only 467 * remain valid while mmap_sem is held. 468 * 469 * Must be called with mmap_sem held. It may be released. See below. 470 * 471 * __get_user_pages walks a process's page tables and takes a reference to 472 * each struct page that each user address corresponds to at a given 473 * instant. That is, it takes the page that would be accessed if a user 474 * thread accesses the given user virtual address at that instant. 475 * 476 * This does not guarantee that the page exists in the user mappings when 477 * __get_user_pages returns, and there may even be a completely different 478 * page there in some cases (eg. if mmapped pagecache has been invalidated 479 * and subsequently re faulted). However it does guarantee that the page 480 * won't be freed completely. And mostly callers simply care that the page 481 * contains data that was valid *at some point in time*. Typically, an IO 482 * or similar operation cannot guarantee anything stronger anyway because 483 * locks can't be held over the syscall boundary. 484 * 485 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If 486 * the page is written to, set_page_dirty (or set_page_dirty_lock, as 487 * appropriate) must be called after the page is finished with, and 488 * before put_page is called. 489 * 490 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO 491 * or mmap_sem contention, and if waiting is needed to pin all pages, 492 * *@nonblocking will be set to 0. Further, if @gup_flags does not 493 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in 494 * this case. 495 * 496 * A caller using such a combination of @nonblocking and @gup_flags 497 * must therefore hold the mmap_sem for reading only, and recognize 498 * when it's been released. Otherwise, it must be held for either 499 * reading or writing and will not be released. 500 * 501 * In most cases, get_user_pages or get_user_pages_fast should be used 502 * instead of __get_user_pages. __get_user_pages should be used only if 503 * you need some special @gup_flags. 504 */ 505 long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 506 unsigned long start, unsigned long nr_pages, 507 unsigned int gup_flags, struct page **pages, 508 struct vm_area_struct **vmas, int *nonblocking) 509 { 510 long i = 0; 511 unsigned int page_mask; 512 struct vm_area_struct *vma = NULL; 513 514 if (!nr_pages) 515 return 0; 516 517 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); 518 519 /* 520 * If FOLL_FORCE is set then do not force a full fault as the hinting 521 * fault information is unrelated to the reference behaviour of a task 522 * using the address space 523 */ 524 if (!(gup_flags & FOLL_FORCE)) 525 gup_flags |= FOLL_NUMA; 526 527 do { 528 struct page *page; 529 unsigned int foll_flags = gup_flags; 530 unsigned int page_increm; 531 532 /* first iteration or cross vma bound */ 533 if (!vma || start >= vma->vm_end) { 534 vma = find_extend_vma(mm, start); 535 if (!vma && in_gate_area(mm, start)) { 536 int ret; 537 ret = get_gate_page(mm, start & PAGE_MASK, 538 gup_flags, &vma, 539 pages ? &pages[i] : NULL); 540 if (ret) 541 return i ? : ret; 542 page_mask = 0; 543 goto next_page; 544 } 545 546 if (!vma || check_vma_flags(vma, gup_flags)) 547 return i ? : -EFAULT; 548 if (is_vm_hugetlb_page(vma)) { 549 i = follow_hugetlb_page(mm, vma, pages, vmas, 550 &start, &nr_pages, i, 551 gup_flags); 552 continue; 553 } 554 } 555 retry: 556 /* 557 * If we have a pending SIGKILL, don't keep faulting pages and 558 * potentially allocating memory. 559 */ 560 if (unlikely(fatal_signal_pending(current))) 561 return i ? i : -ERESTARTSYS; 562 cond_resched(); 563 page = follow_page_mask(vma, start, foll_flags, &page_mask); 564 if (!page) { 565 int ret; 566 ret = faultin_page(tsk, vma, start, &foll_flags, 567 nonblocking); 568 switch (ret) { 569 case 0: 570 goto retry; 571 case -EFAULT: 572 case -ENOMEM: 573 case -EHWPOISON: 574 return i ? i : ret; 575 case -EBUSY: 576 return i; 577 case -ENOENT: 578 goto next_page; 579 } 580 BUG(); 581 } else if (PTR_ERR(page) == -EEXIST) { 582 /* 583 * Proper page table entry exists, but no corresponding 584 * struct page. 585 */ 586 goto next_page; 587 } else if (IS_ERR(page)) { 588 return i ? i : PTR_ERR(page); 589 } 590 if (pages) { 591 pages[i] = page; 592 flush_anon_page(vma, page, start); 593 flush_dcache_page(page); 594 page_mask = 0; 595 } 596 next_page: 597 if (vmas) { 598 vmas[i] = vma; 599 page_mask = 0; 600 } 601 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); 602 if (page_increm > nr_pages) 603 page_increm = nr_pages; 604 i += page_increm; 605 start += page_increm * PAGE_SIZE; 606 nr_pages -= page_increm; 607 } while (nr_pages); 608 return i; 609 } 610 EXPORT_SYMBOL(__get_user_pages); 611 612 /* 613 * fixup_user_fault() - manually resolve a user page fault 614 * @tsk: the task_struct to use for page fault accounting, or 615 * NULL if faults are not to be recorded. 616 * @mm: mm_struct of target mm 617 * @address: user address 618 * @fault_flags:flags to pass down to handle_mm_fault() 619 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller 620 * does not allow retry 621 * 622 * This is meant to be called in the specific scenario where for locking reasons 623 * we try to access user memory in atomic context (within a pagefault_disable() 624 * section), this returns -EFAULT, and we want to resolve the user fault before 625 * trying again. 626 * 627 * Typically this is meant to be used by the futex code. 628 * 629 * The main difference with get_user_pages() is that this function will 630 * unconditionally call handle_mm_fault() which will in turn perform all the 631 * necessary SW fixup of the dirty and young bits in the PTE, while 632 * get_user_pages() only guarantees to update these in the struct page. 633 * 634 * This is important for some architectures where those bits also gate the 635 * access permission to the page because they are maintained in software. On 636 * such architectures, gup() will not be enough to make a subsequent access 637 * succeed. 638 * 639 * This function will not return with an unlocked mmap_sem. So it has not the 640 * same semantics wrt the @mm->mmap_sem as does filemap_fault(). 641 */ 642 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, 643 unsigned long address, unsigned int fault_flags, 644 bool *unlocked) 645 { 646 struct vm_area_struct *vma; 647 vm_flags_t vm_flags; 648 int ret, major = 0; 649 650 if (unlocked) 651 fault_flags |= FAULT_FLAG_ALLOW_RETRY; 652 653 retry: 654 vma = find_extend_vma(mm, address); 655 if (!vma || address < vma->vm_start) 656 return -EFAULT; 657 658 vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ; 659 if (!(vm_flags & vma->vm_flags)) 660 return -EFAULT; 661 662 ret = handle_mm_fault(mm, vma, address, fault_flags); 663 major |= ret & VM_FAULT_MAJOR; 664 if (ret & VM_FAULT_ERROR) { 665 if (ret & VM_FAULT_OOM) 666 return -ENOMEM; 667 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) 668 return -EHWPOISON; 669 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV)) 670 return -EFAULT; 671 BUG(); 672 } 673 674 if (ret & VM_FAULT_RETRY) { 675 down_read(&mm->mmap_sem); 676 if (!(fault_flags & FAULT_FLAG_TRIED)) { 677 *unlocked = true; 678 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; 679 fault_flags |= FAULT_FLAG_TRIED; 680 goto retry; 681 } 682 } 683 684 if (tsk) { 685 if (major) 686 tsk->maj_flt++; 687 else 688 tsk->min_flt++; 689 } 690 return 0; 691 } 692 693 static __always_inline long __get_user_pages_locked(struct task_struct *tsk, 694 struct mm_struct *mm, 695 unsigned long start, 696 unsigned long nr_pages, 697 int write, int force, 698 struct page **pages, 699 struct vm_area_struct **vmas, 700 int *locked, bool notify_drop, 701 unsigned int flags) 702 { 703 long ret, pages_done; 704 bool lock_dropped; 705 706 if (locked) { 707 /* if VM_FAULT_RETRY can be returned, vmas become invalid */ 708 BUG_ON(vmas); 709 /* check caller initialized locked */ 710 BUG_ON(*locked != 1); 711 } 712 713 if (pages) 714 flags |= FOLL_GET; 715 if (write) 716 flags |= FOLL_WRITE; 717 if (force) 718 flags |= FOLL_FORCE; 719 720 pages_done = 0; 721 lock_dropped = false; 722 for (;;) { 723 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages, 724 vmas, locked); 725 if (!locked) 726 /* VM_FAULT_RETRY couldn't trigger, bypass */ 727 return ret; 728 729 /* VM_FAULT_RETRY cannot return errors */ 730 if (!*locked) { 731 BUG_ON(ret < 0); 732 BUG_ON(ret >= nr_pages); 733 } 734 735 if (!pages) 736 /* If it's a prefault don't insist harder */ 737 return ret; 738 739 if (ret > 0) { 740 nr_pages -= ret; 741 pages_done += ret; 742 if (!nr_pages) 743 break; 744 } 745 if (*locked) { 746 /* VM_FAULT_RETRY didn't trigger */ 747 if (!pages_done) 748 pages_done = ret; 749 break; 750 } 751 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */ 752 pages += ret; 753 start += ret << PAGE_SHIFT; 754 755 /* 756 * Repeat on the address that fired VM_FAULT_RETRY 757 * without FAULT_FLAG_ALLOW_RETRY but with 758 * FAULT_FLAG_TRIED. 759 */ 760 *locked = 1; 761 lock_dropped = true; 762 down_read(&mm->mmap_sem); 763 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, 764 pages, NULL, NULL); 765 if (ret != 1) { 766 BUG_ON(ret > 1); 767 if (!pages_done) 768 pages_done = ret; 769 break; 770 } 771 nr_pages--; 772 pages_done++; 773 if (!nr_pages) 774 break; 775 pages++; 776 start += PAGE_SIZE; 777 } 778 if (notify_drop && lock_dropped && *locked) { 779 /* 780 * We must let the caller know we temporarily dropped the lock 781 * and so the critical section protected by it was lost. 782 */ 783 up_read(&mm->mmap_sem); 784 *locked = 0; 785 } 786 return pages_done; 787 } 788 789 /* 790 * We can leverage the VM_FAULT_RETRY functionality in the page fault 791 * paths better by using either get_user_pages_locked() or 792 * get_user_pages_unlocked(). 793 * 794 * get_user_pages_locked() is suitable to replace the form: 795 * 796 * down_read(&mm->mmap_sem); 797 * do_something() 798 * get_user_pages(tsk, mm, ..., pages, NULL); 799 * up_read(&mm->mmap_sem); 800 * 801 * to: 802 * 803 * int locked = 1; 804 * down_read(&mm->mmap_sem); 805 * do_something() 806 * get_user_pages_locked(tsk, mm, ..., pages, &locked); 807 * if (locked) 808 * up_read(&mm->mmap_sem); 809 */ 810 long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm, 811 unsigned long start, unsigned long nr_pages, 812 int write, int force, struct page **pages, 813 int *locked) 814 { 815 return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, 816 pages, NULL, locked, true, FOLL_TOUCH); 817 } 818 EXPORT_SYMBOL(get_user_pages_locked); 819 820 /* 821 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to 822 * pass additional gup_flags as last parameter (like FOLL_HWPOISON). 823 * 824 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the 825 * caller if required (just like with __get_user_pages). "FOLL_GET", 826 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed 827 * according to the parameters "pages", "write", "force" 828 * respectively. 829 */ 830 __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, 831 unsigned long start, unsigned long nr_pages, 832 int write, int force, struct page **pages, 833 unsigned int gup_flags) 834 { 835 long ret; 836 int locked = 1; 837 down_read(&mm->mmap_sem); 838 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, 839 pages, NULL, &locked, false, gup_flags); 840 if (locked) 841 up_read(&mm->mmap_sem); 842 return ret; 843 } 844 EXPORT_SYMBOL(__get_user_pages_unlocked); 845 846 /* 847 * get_user_pages_unlocked() is suitable to replace the form: 848 * 849 * down_read(&mm->mmap_sem); 850 * get_user_pages(tsk, mm, ..., pages, NULL); 851 * up_read(&mm->mmap_sem); 852 * 853 * with: 854 * 855 * get_user_pages_unlocked(tsk, mm, ..., pages); 856 * 857 * It is functionally equivalent to get_user_pages_fast so 858 * get_user_pages_fast should be used instead, if the two parameters 859 * "tsk" and "mm" are respectively equal to current and current->mm, 860 * or if "force" shall be set to 1 (get_user_pages_fast misses the 861 * "force" parameter). 862 */ 863 long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, 864 unsigned long start, unsigned long nr_pages, 865 int write, int force, struct page **pages) 866 { 867 return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write, 868 force, pages, FOLL_TOUCH); 869 } 870 EXPORT_SYMBOL(get_user_pages_unlocked); 871 872 /* 873 * get_user_pages() - pin user pages in memory 874 * @tsk: the task_struct to use for page fault accounting, or 875 * NULL if faults are not to be recorded. 876 * @mm: mm_struct of target mm 877 * @start: starting user address 878 * @nr_pages: number of pages from start to pin 879 * @write: whether pages will be written to by the caller 880 * @force: whether to force access even when user mapping is currently 881 * protected (but never forces write access to shared mapping). 882 * @pages: array that receives pointers to the pages pinned. 883 * Should be at least nr_pages long. Or NULL, if caller 884 * only intends to ensure the pages are faulted in. 885 * @vmas: array of pointers to vmas corresponding to each page. 886 * Or NULL if the caller does not require them. 887 * 888 * Returns number of pages pinned. This may be fewer than the number 889 * requested. If nr_pages is 0 or negative, returns 0. If no pages 890 * were pinned, returns -errno. Each page returned must be released 891 * with a put_page() call when it is finished with. vmas will only 892 * remain valid while mmap_sem is held. 893 * 894 * Must be called with mmap_sem held for read or write. 895 * 896 * get_user_pages walks a process's page tables and takes a reference to 897 * each struct page that each user address corresponds to at a given 898 * instant. That is, it takes the page that would be accessed if a user 899 * thread accesses the given user virtual address at that instant. 900 * 901 * This does not guarantee that the page exists in the user mappings when 902 * get_user_pages returns, and there may even be a completely different 903 * page there in some cases (eg. if mmapped pagecache has been invalidated 904 * and subsequently re faulted). However it does guarantee that the page 905 * won't be freed completely. And mostly callers simply care that the page 906 * contains data that was valid *at some point in time*. Typically, an IO 907 * or similar operation cannot guarantee anything stronger anyway because 908 * locks can't be held over the syscall boundary. 909 * 910 * If write=0, the page must not be written to. If the page is written to, 911 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called 912 * after the page is finished with, and before put_page is called. 913 * 914 * get_user_pages is typically used for fewer-copy IO operations, to get a 915 * handle on the memory by some means other than accesses via the user virtual 916 * addresses. The pages may be submitted for DMA to devices or accessed via 917 * their kernel linear mapping (via the kmap APIs). Care should be taken to 918 * use the correct cache flushing APIs. 919 * 920 * See also get_user_pages_fast, for performance critical applications. 921 * 922 * get_user_pages should be phased out in favor of 923 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing 924 * should use get_user_pages because it cannot pass 925 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. 926 */ 927 long get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 928 unsigned long start, unsigned long nr_pages, int write, 929 int force, struct page **pages, struct vm_area_struct **vmas) 930 { 931 return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, 932 pages, vmas, NULL, false, FOLL_TOUCH); 933 } 934 EXPORT_SYMBOL(get_user_pages); 935 936 /** 937 * populate_vma_page_range() - populate a range of pages in the vma. 938 * @vma: target vma 939 * @start: start address 940 * @end: end address 941 * @nonblocking: 942 * 943 * This takes care of mlocking the pages too if VM_LOCKED is set. 944 * 945 * return 0 on success, negative error code on error. 946 * 947 * vma->vm_mm->mmap_sem must be held. 948 * 949 * If @nonblocking is NULL, it may be held for read or write and will 950 * be unperturbed. 951 * 952 * If @nonblocking is non-NULL, it must held for read only and may be 953 * released. If it's released, *@nonblocking will be set to 0. 954 */ 955 long populate_vma_page_range(struct vm_area_struct *vma, 956 unsigned long start, unsigned long end, int *nonblocking) 957 { 958 struct mm_struct *mm = vma->vm_mm; 959 unsigned long nr_pages = (end - start) / PAGE_SIZE; 960 int gup_flags; 961 962 VM_BUG_ON(start & ~PAGE_MASK); 963 VM_BUG_ON(end & ~PAGE_MASK); 964 VM_BUG_ON_VMA(start < vma->vm_start, vma); 965 VM_BUG_ON_VMA(end > vma->vm_end, vma); 966 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); 967 968 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK; 969 if (vma->vm_flags & VM_LOCKONFAULT) 970 gup_flags &= ~FOLL_POPULATE; 971 /* 972 * We want to touch writable mappings with a write fault in order 973 * to break COW, except for shared mappings because these don't COW 974 * and we would not want to dirty them for nothing. 975 */ 976 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) 977 gup_flags |= FOLL_WRITE; 978 979 /* 980 * We want mlock to succeed for regions that have any permissions 981 * other than PROT_NONE. 982 */ 983 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) 984 gup_flags |= FOLL_FORCE; 985 986 /* 987 * We made sure addr is within a VMA, so the following will 988 * not result in a stack expansion that recurses back here. 989 */ 990 return __get_user_pages(current, mm, start, nr_pages, gup_flags, 991 NULL, NULL, nonblocking); 992 } 993 994 /* 995 * __mm_populate - populate and/or mlock pages within a range of address space. 996 * 997 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap 998 * flags. VMAs must be already marked with the desired vm_flags, and 999 * mmap_sem must not be held. 1000 */ 1001 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) 1002 { 1003 struct mm_struct *mm = current->mm; 1004 unsigned long end, nstart, nend; 1005 struct vm_area_struct *vma = NULL; 1006 int locked = 0; 1007 long ret = 0; 1008 1009 VM_BUG_ON(start & ~PAGE_MASK); 1010 VM_BUG_ON(len != PAGE_ALIGN(len)); 1011 end = start + len; 1012 1013 for (nstart = start; nstart < end; nstart = nend) { 1014 /* 1015 * We want to fault in pages for [nstart; end) address range. 1016 * Find first corresponding VMA. 1017 */ 1018 if (!locked) { 1019 locked = 1; 1020 down_read(&mm->mmap_sem); 1021 vma = find_vma(mm, nstart); 1022 } else if (nstart >= vma->vm_end) 1023 vma = vma->vm_next; 1024 if (!vma || vma->vm_start >= end) 1025 break; 1026 /* 1027 * Set [nstart; nend) to intersection of desired address 1028 * range with the first VMA. Also, skip undesirable VMA types. 1029 */ 1030 nend = min(end, vma->vm_end); 1031 if (vma->vm_flags & (VM_IO | VM_PFNMAP)) 1032 continue; 1033 if (nstart < vma->vm_start) 1034 nstart = vma->vm_start; 1035 /* 1036 * Now fault in a range of pages. populate_vma_page_range() 1037 * double checks the vma flags, so that it won't mlock pages 1038 * if the vma was already munlocked. 1039 */ 1040 ret = populate_vma_page_range(vma, nstart, nend, &locked); 1041 if (ret < 0) { 1042 if (ignore_errors) { 1043 ret = 0; 1044 continue; /* continue at next VMA */ 1045 } 1046 break; 1047 } 1048 nend = nstart + ret * PAGE_SIZE; 1049 ret = 0; 1050 } 1051 if (locked) 1052 up_read(&mm->mmap_sem); 1053 return ret; /* 0 or negative error code */ 1054 } 1055 1056 /** 1057 * get_dump_page() - pin user page in memory while writing it to core dump 1058 * @addr: user address 1059 * 1060 * Returns struct page pointer of user page pinned for dump, 1061 * to be freed afterwards by page_cache_release() or put_page(). 1062 * 1063 * Returns NULL on any kind of failure - a hole must then be inserted into 1064 * the corefile, to preserve alignment with its headers; and also returns 1065 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - 1066 * allowing a hole to be left in the corefile to save diskspace. 1067 * 1068 * Called without mmap_sem, but after all other threads have been killed. 1069 */ 1070 #ifdef CONFIG_ELF_CORE 1071 struct page *get_dump_page(unsigned long addr) 1072 { 1073 struct vm_area_struct *vma; 1074 struct page *page; 1075 1076 if (__get_user_pages(current, current->mm, addr, 1, 1077 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, 1078 NULL) < 1) 1079 return NULL; 1080 flush_cache_page(vma, addr, page_to_pfn(page)); 1081 return page; 1082 } 1083 #endif /* CONFIG_ELF_CORE */ 1084 1085 /* 1086 * Generic RCU Fast GUP 1087 * 1088 * get_user_pages_fast attempts to pin user pages by walking the page 1089 * tables directly and avoids taking locks. Thus the walker needs to be 1090 * protected from page table pages being freed from under it, and should 1091 * block any THP splits. 1092 * 1093 * One way to achieve this is to have the walker disable interrupts, and 1094 * rely on IPIs from the TLB flushing code blocking before the page table 1095 * pages are freed. This is unsuitable for architectures that do not need 1096 * to broadcast an IPI when invalidating TLBs. 1097 * 1098 * Another way to achieve this is to batch up page table containing pages 1099 * belonging to more than one mm_user, then rcu_sched a callback to free those 1100 * pages. Disabling interrupts will allow the fast_gup walker to both block 1101 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs 1102 * (which is a relatively rare event). The code below adopts this strategy. 1103 * 1104 * Before activating this code, please be aware that the following assumptions 1105 * are currently made: 1106 * 1107 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free 1108 * pages containing page tables. 1109 * 1110 * *) ptes can be read atomically by the architecture. 1111 * 1112 * *) access_ok is sufficient to validate userspace address ranges. 1113 * 1114 * The last two assumptions can be relaxed by the addition of helper functions. 1115 * 1116 * This code is based heavily on the PowerPC implementation by Nick Piggin. 1117 */ 1118 #ifdef CONFIG_HAVE_GENERIC_RCU_GUP 1119 1120 #ifdef __HAVE_ARCH_PTE_SPECIAL 1121 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, 1122 int write, struct page **pages, int *nr) 1123 { 1124 pte_t *ptep, *ptem; 1125 int ret = 0; 1126 1127 ptem = ptep = pte_offset_map(&pmd, addr); 1128 do { 1129 /* 1130 * In the line below we are assuming that the pte can be read 1131 * atomically. If this is not the case for your architecture, 1132 * please wrap this in a helper function! 1133 * 1134 * for an example see gup_get_pte in arch/x86/mm/gup.c 1135 */ 1136 pte_t pte = READ_ONCE(*ptep); 1137 struct page *head, *page; 1138 1139 /* 1140 * Similar to the PMD case below, NUMA hinting must take slow 1141 * path using the pte_protnone check. 1142 */ 1143 if (!pte_present(pte) || pte_special(pte) || 1144 pte_protnone(pte) || (write && !pte_write(pte))) 1145 goto pte_unmap; 1146 1147 VM_BUG_ON(!pfn_valid(pte_pfn(pte))); 1148 page = pte_page(pte); 1149 head = compound_head(page); 1150 1151 if (!page_cache_get_speculative(head)) 1152 goto pte_unmap; 1153 1154 if (unlikely(pte_val(pte) != pte_val(*ptep))) { 1155 put_page(head); 1156 goto pte_unmap; 1157 } 1158 1159 VM_BUG_ON_PAGE(compound_head(page) != head, page); 1160 pages[*nr] = page; 1161 (*nr)++; 1162 1163 } while (ptep++, addr += PAGE_SIZE, addr != end); 1164 1165 ret = 1; 1166 1167 pte_unmap: 1168 pte_unmap(ptem); 1169 return ret; 1170 } 1171 #else 1172 1173 /* 1174 * If we can't determine whether or not a pte is special, then fail immediately 1175 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not 1176 * to be special. 1177 * 1178 * For a futex to be placed on a THP tail page, get_futex_key requires a 1179 * __get_user_pages_fast implementation that can pin pages. Thus it's still 1180 * useful to have gup_huge_pmd even if we can't operate on ptes. 1181 */ 1182 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, 1183 int write, struct page **pages, int *nr) 1184 { 1185 return 0; 1186 } 1187 #endif /* __HAVE_ARCH_PTE_SPECIAL */ 1188 1189 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, 1190 unsigned long end, int write, struct page **pages, int *nr) 1191 { 1192 struct page *head, *page; 1193 int refs; 1194 1195 if (write && !pmd_write(orig)) 1196 return 0; 1197 1198 refs = 0; 1199 head = pmd_page(orig); 1200 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); 1201 do { 1202 VM_BUG_ON_PAGE(compound_head(page) != head, page); 1203 pages[*nr] = page; 1204 (*nr)++; 1205 page++; 1206 refs++; 1207 } while (addr += PAGE_SIZE, addr != end); 1208 1209 if (!page_cache_add_speculative(head, refs)) { 1210 *nr -= refs; 1211 return 0; 1212 } 1213 1214 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { 1215 *nr -= refs; 1216 while (refs--) 1217 put_page(head); 1218 return 0; 1219 } 1220 1221 return 1; 1222 } 1223 1224 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, 1225 unsigned long end, int write, struct page **pages, int *nr) 1226 { 1227 struct page *head, *page; 1228 int refs; 1229 1230 if (write && !pud_write(orig)) 1231 return 0; 1232 1233 refs = 0; 1234 head = pud_page(orig); 1235 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); 1236 do { 1237 VM_BUG_ON_PAGE(compound_head(page) != head, page); 1238 pages[*nr] = page; 1239 (*nr)++; 1240 page++; 1241 refs++; 1242 } while (addr += PAGE_SIZE, addr != end); 1243 1244 if (!page_cache_add_speculative(head, refs)) { 1245 *nr -= refs; 1246 return 0; 1247 } 1248 1249 if (unlikely(pud_val(orig) != pud_val(*pudp))) { 1250 *nr -= refs; 1251 while (refs--) 1252 put_page(head); 1253 return 0; 1254 } 1255 1256 return 1; 1257 } 1258 1259 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, 1260 unsigned long end, int write, 1261 struct page **pages, int *nr) 1262 { 1263 int refs; 1264 struct page *head, *page; 1265 1266 if (write && !pgd_write(orig)) 1267 return 0; 1268 1269 refs = 0; 1270 head = pgd_page(orig); 1271 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); 1272 do { 1273 VM_BUG_ON_PAGE(compound_head(page) != head, page); 1274 pages[*nr] = page; 1275 (*nr)++; 1276 page++; 1277 refs++; 1278 } while (addr += PAGE_SIZE, addr != end); 1279 1280 if (!page_cache_add_speculative(head, refs)) { 1281 *nr -= refs; 1282 return 0; 1283 } 1284 1285 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { 1286 *nr -= refs; 1287 while (refs--) 1288 put_page(head); 1289 return 0; 1290 } 1291 1292 return 1; 1293 } 1294 1295 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, 1296 int write, struct page **pages, int *nr) 1297 { 1298 unsigned long next; 1299 pmd_t *pmdp; 1300 1301 pmdp = pmd_offset(&pud, addr); 1302 do { 1303 pmd_t pmd = READ_ONCE(*pmdp); 1304 1305 next = pmd_addr_end(addr, end); 1306 if (pmd_none(pmd)) 1307 return 0; 1308 1309 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) { 1310 /* 1311 * NUMA hinting faults need to be handled in the GUP 1312 * slowpath for accounting purposes and so that they 1313 * can be serialised against THP migration. 1314 */ 1315 if (pmd_protnone(pmd)) 1316 return 0; 1317 1318 if (!gup_huge_pmd(pmd, pmdp, addr, next, write, 1319 pages, nr)) 1320 return 0; 1321 1322 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { 1323 /* 1324 * architecture have different format for hugetlbfs 1325 * pmd format and THP pmd format 1326 */ 1327 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, 1328 PMD_SHIFT, next, write, pages, nr)) 1329 return 0; 1330 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) 1331 return 0; 1332 } while (pmdp++, addr = next, addr != end); 1333 1334 return 1; 1335 } 1336 1337 static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, 1338 int write, struct page **pages, int *nr) 1339 { 1340 unsigned long next; 1341 pud_t *pudp; 1342 1343 pudp = pud_offset(&pgd, addr); 1344 do { 1345 pud_t pud = READ_ONCE(*pudp); 1346 1347 next = pud_addr_end(addr, end); 1348 if (pud_none(pud)) 1349 return 0; 1350 if (unlikely(pud_huge(pud))) { 1351 if (!gup_huge_pud(pud, pudp, addr, next, write, 1352 pages, nr)) 1353 return 0; 1354 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { 1355 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, 1356 PUD_SHIFT, next, write, pages, nr)) 1357 return 0; 1358 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) 1359 return 0; 1360 } while (pudp++, addr = next, addr != end); 1361 1362 return 1; 1363 } 1364 1365 /* 1366 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to 1367 * the regular GUP. It will only return non-negative values. 1368 */ 1369 int __get_user_pages_fast(unsigned long start, int nr_pages, int write, 1370 struct page **pages) 1371 { 1372 struct mm_struct *mm = current->mm; 1373 unsigned long addr, len, end; 1374 unsigned long next, flags; 1375 pgd_t *pgdp; 1376 int nr = 0; 1377 1378 start &= PAGE_MASK; 1379 addr = start; 1380 len = (unsigned long) nr_pages << PAGE_SHIFT; 1381 end = start + len; 1382 1383 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, 1384 start, len))) 1385 return 0; 1386 1387 /* 1388 * Disable interrupts. We use the nested form as we can already have 1389 * interrupts disabled by get_futex_key. 1390 * 1391 * With interrupts disabled, we block page table pages from being 1392 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h 1393 * for more details. 1394 * 1395 * We do not adopt an rcu_read_lock(.) here as we also want to 1396 * block IPIs that come from THPs splitting. 1397 */ 1398 1399 local_irq_save(flags); 1400 pgdp = pgd_offset(mm, addr); 1401 do { 1402 pgd_t pgd = READ_ONCE(*pgdp); 1403 1404 next = pgd_addr_end(addr, end); 1405 if (pgd_none(pgd)) 1406 break; 1407 if (unlikely(pgd_huge(pgd))) { 1408 if (!gup_huge_pgd(pgd, pgdp, addr, next, write, 1409 pages, &nr)) 1410 break; 1411 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { 1412 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, 1413 PGDIR_SHIFT, next, write, pages, &nr)) 1414 break; 1415 } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) 1416 break; 1417 } while (pgdp++, addr = next, addr != end); 1418 local_irq_restore(flags); 1419 1420 return nr; 1421 } 1422 1423 /** 1424 * get_user_pages_fast() - pin user pages in memory 1425 * @start: starting user address 1426 * @nr_pages: number of pages from start to pin 1427 * @write: whether pages will be written to 1428 * @pages: array that receives pointers to the pages pinned. 1429 * Should be at least nr_pages long. 1430 * 1431 * Attempt to pin user pages in memory without taking mm->mmap_sem. 1432 * If not successful, it will fall back to taking the lock and 1433 * calling get_user_pages(). 1434 * 1435 * Returns number of pages pinned. This may be fewer than the number 1436 * requested. If nr_pages is 0 or negative, returns 0. If no pages 1437 * were pinned, returns -errno. 1438 */ 1439 int get_user_pages_fast(unsigned long start, int nr_pages, int write, 1440 struct page **pages) 1441 { 1442 struct mm_struct *mm = current->mm; 1443 int nr, ret; 1444 1445 start &= PAGE_MASK; 1446 nr = __get_user_pages_fast(start, nr_pages, write, pages); 1447 ret = nr; 1448 1449 if (nr < nr_pages) { 1450 /* Try to get the remaining pages with get_user_pages */ 1451 start += nr << PAGE_SHIFT; 1452 pages += nr; 1453 1454 ret = get_user_pages_unlocked(current, mm, start, 1455 nr_pages - nr, write, 0, pages); 1456 1457 /* Have to be a bit careful with return values */ 1458 if (nr > 0) { 1459 if (ret < 0) 1460 ret = nr; 1461 else 1462 ret += nr; 1463 } 1464 } 1465 1466 return ret; 1467 } 1468 1469 #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */ 1470