xref: /openbmc/linux/mm/memory.c (revision e8e0929d)
1 /*
2  *  linux/mm/memory.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  */
6 
7 /*
8  * demand-loading started 01.12.91 - seems it is high on the list of
9  * things wanted, and it should be easy to implement. - Linus
10  */
11 
12 /*
13  * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
14  * pages started 02.12.91, seems to work. - Linus.
15  *
16  * Tested sharing by executing about 30 /bin/sh: under the old kernel it
17  * would have taken more than the 6M I have free, but it worked well as
18  * far as I could see.
19  *
20  * Also corrected some "invalidate()"s - I wasn't doing enough of them.
21  */
22 
23 /*
24  * Real VM (paging to/from disk) started 18.12.91. Much more work and
25  * thought has to go into this. Oh, well..
26  * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
27  *		Found it. Everything seems to work now.
28  * 20.12.91  -  Ok, making the swap-device changeable like the root.
29  */
30 
31 /*
32  * 05.04.94  -  Multi-page memory management added for v1.1.
33  * 		Idea by Alex Bligh (alex@cconcepts.co.uk)
34  *
35  * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
36  *		(Gerhard.Wichert@pdb.siemens.de)
37  *
38  * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
39  */
40 
41 #include <linux/kernel_stat.h>
42 #include <linux/mm.h>
43 #include <linux/hugetlb.h>
44 #include <linux/mman.h>
45 #include <linux/swap.h>
46 #include <linux/highmem.h>
47 #include <linux/pagemap.h>
48 #include <linux/ksm.h>
49 #include <linux/rmap.h>
50 #include <linux/module.h>
51 #include <linux/delayacct.h>
52 #include <linux/init.h>
53 #include <linux/writeback.h>
54 #include <linux/memcontrol.h>
55 #include <linux/mmu_notifier.h>
56 #include <linux/kallsyms.h>
57 #include <linux/swapops.h>
58 #include <linux/elf.h>
59 
60 #include <asm/io.h>
61 #include <asm/pgalloc.h>
62 #include <asm/uaccess.h>
63 #include <asm/tlb.h>
64 #include <asm/tlbflush.h>
65 #include <asm/pgtable.h>
66 
67 #include "internal.h"
68 
69 #ifndef CONFIG_NEED_MULTIPLE_NODES
70 /* use the per-pgdat data instead for discontigmem - mbligh */
71 unsigned long max_mapnr;
72 struct page *mem_map;
73 
74 EXPORT_SYMBOL(max_mapnr);
75 EXPORT_SYMBOL(mem_map);
76 #endif
77 
78 unsigned long num_physpages;
79 /*
80  * A number of key systems in x86 including ioremap() rely on the assumption
81  * that high_memory defines the upper bound on direct map memory, then end
82  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
83  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
84  * and ZONE_HIGHMEM.
85  */
86 void * high_memory;
87 
88 EXPORT_SYMBOL(num_physpages);
89 EXPORT_SYMBOL(high_memory);
90 
91 /*
92  * Randomize the address space (stacks, mmaps, brk, etc.).
93  *
94  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
95  *   as ancient (libc5 based) binaries can segfault. )
96  */
97 int randomize_va_space __read_mostly =
98 #ifdef CONFIG_COMPAT_BRK
99 					1;
100 #else
101 					2;
102 #endif
103 
104 static int __init disable_randmaps(char *s)
105 {
106 	randomize_va_space = 0;
107 	return 1;
108 }
109 __setup("norandmaps", disable_randmaps);
110 
111 unsigned long zero_pfn __read_mostly;
112 unsigned long highest_memmap_pfn __read_mostly;
113 
114 /*
115  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
116  */
117 static int __init init_zero_pfn(void)
118 {
119 	zero_pfn = page_to_pfn(ZERO_PAGE(0));
120 	return 0;
121 }
122 core_initcall(init_zero_pfn);
123 
124 /*
125  * If a p?d_bad entry is found while walking page tables, report
126  * the error, before resetting entry to p?d_none.  Usually (but
127  * very seldom) called out from the p?d_none_or_clear_bad macros.
128  */
129 
130 void pgd_clear_bad(pgd_t *pgd)
131 {
132 	pgd_ERROR(*pgd);
133 	pgd_clear(pgd);
134 }
135 
136 void pud_clear_bad(pud_t *pud)
137 {
138 	pud_ERROR(*pud);
139 	pud_clear(pud);
140 }
141 
142 void pmd_clear_bad(pmd_t *pmd)
143 {
144 	pmd_ERROR(*pmd);
145 	pmd_clear(pmd);
146 }
147 
148 /*
149  * Note: this doesn't free the actual pages themselves. That
150  * has been handled earlier when unmapping all the memory regions.
151  */
152 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
153 			   unsigned long addr)
154 {
155 	pgtable_t token = pmd_pgtable(*pmd);
156 	pmd_clear(pmd);
157 	pte_free_tlb(tlb, token, addr);
158 	tlb->mm->nr_ptes--;
159 }
160 
161 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
162 				unsigned long addr, unsigned long end,
163 				unsigned long floor, unsigned long ceiling)
164 {
165 	pmd_t *pmd;
166 	unsigned long next;
167 	unsigned long start;
168 
169 	start = addr;
170 	pmd = pmd_offset(pud, addr);
171 	do {
172 		next = pmd_addr_end(addr, end);
173 		if (pmd_none_or_clear_bad(pmd))
174 			continue;
175 		free_pte_range(tlb, pmd, addr);
176 	} while (pmd++, addr = next, addr != end);
177 
178 	start &= PUD_MASK;
179 	if (start < floor)
180 		return;
181 	if (ceiling) {
182 		ceiling &= PUD_MASK;
183 		if (!ceiling)
184 			return;
185 	}
186 	if (end - 1 > ceiling - 1)
187 		return;
188 
189 	pmd = pmd_offset(pud, start);
190 	pud_clear(pud);
191 	pmd_free_tlb(tlb, pmd, start);
192 }
193 
194 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
195 				unsigned long addr, unsigned long end,
196 				unsigned long floor, unsigned long ceiling)
197 {
198 	pud_t *pud;
199 	unsigned long next;
200 	unsigned long start;
201 
202 	start = addr;
203 	pud = pud_offset(pgd, addr);
204 	do {
205 		next = pud_addr_end(addr, end);
206 		if (pud_none_or_clear_bad(pud))
207 			continue;
208 		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
209 	} while (pud++, addr = next, addr != end);
210 
211 	start &= PGDIR_MASK;
212 	if (start < floor)
213 		return;
214 	if (ceiling) {
215 		ceiling &= PGDIR_MASK;
216 		if (!ceiling)
217 			return;
218 	}
219 	if (end - 1 > ceiling - 1)
220 		return;
221 
222 	pud = pud_offset(pgd, start);
223 	pgd_clear(pgd);
224 	pud_free_tlb(tlb, pud, start);
225 }
226 
227 /*
228  * This function frees user-level page tables of a process.
229  *
230  * Must be called with pagetable lock held.
231  */
232 void free_pgd_range(struct mmu_gather *tlb,
233 			unsigned long addr, unsigned long end,
234 			unsigned long floor, unsigned long ceiling)
235 {
236 	pgd_t *pgd;
237 	unsigned long next;
238 	unsigned long start;
239 
240 	/*
241 	 * The next few lines have given us lots of grief...
242 	 *
243 	 * Why are we testing PMD* at this top level?  Because often
244 	 * there will be no work to do at all, and we'd prefer not to
245 	 * go all the way down to the bottom just to discover that.
246 	 *
247 	 * Why all these "- 1"s?  Because 0 represents both the bottom
248 	 * of the address space and the top of it (using -1 for the
249 	 * top wouldn't help much: the masks would do the wrong thing).
250 	 * The rule is that addr 0 and floor 0 refer to the bottom of
251 	 * the address space, but end 0 and ceiling 0 refer to the top
252 	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
253 	 * that end 0 case should be mythical).
254 	 *
255 	 * Wherever addr is brought up or ceiling brought down, we must
256 	 * be careful to reject "the opposite 0" before it confuses the
257 	 * subsequent tests.  But what about where end is brought down
258 	 * by PMD_SIZE below? no, end can't go down to 0 there.
259 	 *
260 	 * Whereas we round start (addr) and ceiling down, by different
261 	 * masks at different levels, in order to test whether a table
262 	 * now has no other vmas using it, so can be freed, we don't
263 	 * bother to round floor or end up - the tests don't need that.
264 	 */
265 
266 	addr &= PMD_MASK;
267 	if (addr < floor) {
268 		addr += PMD_SIZE;
269 		if (!addr)
270 			return;
271 	}
272 	if (ceiling) {
273 		ceiling &= PMD_MASK;
274 		if (!ceiling)
275 			return;
276 	}
277 	if (end - 1 > ceiling - 1)
278 		end -= PMD_SIZE;
279 	if (addr > end - 1)
280 		return;
281 
282 	start = addr;
283 	pgd = pgd_offset(tlb->mm, addr);
284 	do {
285 		next = pgd_addr_end(addr, end);
286 		if (pgd_none_or_clear_bad(pgd))
287 			continue;
288 		free_pud_range(tlb, pgd, addr, next, floor, ceiling);
289 	} while (pgd++, addr = next, addr != end);
290 }
291 
292 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
293 		unsigned long floor, unsigned long ceiling)
294 {
295 	while (vma) {
296 		struct vm_area_struct *next = vma->vm_next;
297 		unsigned long addr = vma->vm_start;
298 
299 		/*
300 		 * Hide vma from rmap and truncate_pagecache before freeing
301 		 * pgtables
302 		 */
303 		anon_vma_unlink(vma);
304 		unlink_file_vma(vma);
305 
306 		if (is_vm_hugetlb_page(vma)) {
307 			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
308 				floor, next? next->vm_start: ceiling);
309 		} else {
310 			/*
311 			 * Optimization: gather nearby vmas into one call down
312 			 */
313 			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
314 			       && !is_vm_hugetlb_page(next)) {
315 				vma = next;
316 				next = vma->vm_next;
317 				anon_vma_unlink(vma);
318 				unlink_file_vma(vma);
319 			}
320 			free_pgd_range(tlb, addr, vma->vm_end,
321 				floor, next? next->vm_start: ceiling);
322 		}
323 		vma = next;
324 	}
325 }
326 
327 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
328 {
329 	pgtable_t new = pte_alloc_one(mm, address);
330 	if (!new)
331 		return -ENOMEM;
332 
333 	/*
334 	 * Ensure all pte setup (eg. pte page lock and page clearing) are
335 	 * visible before the pte is made visible to other CPUs by being
336 	 * put into page tables.
337 	 *
338 	 * The other side of the story is the pointer chasing in the page
339 	 * table walking code (when walking the page table without locking;
340 	 * ie. most of the time). Fortunately, these data accesses consist
341 	 * of a chain of data-dependent loads, meaning most CPUs (alpha
342 	 * being the notable exception) will already guarantee loads are
343 	 * seen in-order. See the alpha page table accessors for the
344 	 * smp_read_barrier_depends() barriers in page table walking code.
345 	 */
346 	smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
347 
348 	spin_lock(&mm->page_table_lock);
349 	if (!pmd_present(*pmd)) {	/* Has another populated it ? */
350 		mm->nr_ptes++;
351 		pmd_populate(mm, pmd, new);
352 		new = NULL;
353 	}
354 	spin_unlock(&mm->page_table_lock);
355 	if (new)
356 		pte_free(mm, new);
357 	return 0;
358 }
359 
360 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
361 {
362 	pte_t *new = pte_alloc_one_kernel(&init_mm, address);
363 	if (!new)
364 		return -ENOMEM;
365 
366 	smp_wmb(); /* See comment in __pte_alloc */
367 
368 	spin_lock(&init_mm.page_table_lock);
369 	if (!pmd_present(*pmd)) {	/* Has another populated it ? */
370 		pmd_populate_kernel(&init_mm, pmd, new);
371 		new = NULL;
372 	}
373 	spin_unlock(&init_mm.page_table_lock);
374 	if (new)
375 		pte_free_kernel(&init_mm, new);
376 	return 0;
377 }
378 
379 static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
380 {
381 	if (file_rss)
382 		add_mm_counter(mm, file_rss, file_rss);
383 	if (anon_rss)
384 		add_mm_counter(mm, anon_rss, anon_rss);
385 }
386 
387 /*
388  * This function is called to print an error when a bad pte
389  * is found. For example, we might have a PFN-mapped pte in
390  * a region that doesn't allow it.
391  *
392  * The calling function must still handle the error.
393  */
394 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
395 			  pte_t pte, struct page *page)
396 {
397 	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
398 	pud_t *pud = pud_offset(pgd, addr);
399 	pmd_t *pmd = pmd_offset(pud, addr);
400 	struct address_space *mapping;
401 	pgoff_t index;
402 	static unsigned long resume;
403 	static unsigned long nr_shown;
404 	static unsigned long nr_unshown;
405 
406 	/*
407 	 * Allow a burst of 60 reports, then keep quiet for that minute;
408 	 * or allow a steady drip of one report per second.
409 	 */
410 	if (nr_shown == 60) {
411 		if (time_before(jiffies, resume)) {
412 			nr_unshown++;
413 			return;
414 		}
415 		if (nr_unshown) {
416 			printk(KERN_ALERT
417 				"BUG: Bad page map: %lu messages suppressed\n",
418 				nr_unshown);
419 			nr_unshown = 0;
420 		}
421 		nr_shown = 0;
422 	}
423 	if (nr_shown++ == 0)
424 		resume = jiffies + 60 * HZ;
425 
426 	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
427 	index = linear_page_index(vma, addr);
428 
429 	printk(KERN_ALERT
430 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
431 		current->comm,
432 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
433 	if (page) {
434 		printk(KERN_ALERT
435 		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
436 		page, (void *)page->flags, page_count(page),
437 		page_mapcount(page), page->mapping, page->index);
438 	}
439 	printk(KERN_ALERT
440 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
441 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
442 	/*
443 	 * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
444 	 */
445 	if (vma->vm_ops)
446 		print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
447 				(unsigned long)vma->vm_ops->fault);
448 	if (vma->vm_file && vma->vm_file->f_op)
449 		print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
450 				(unsigned long)vma->vm_file->f_op->mmap);
451 	dump_stack();
452 	add_taint(TAINT_BAD_PAGE);
453 }
454 
455 static inline int is_cow_mapping(unsigned int flags)
456 {
457 	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
458 }
459 
460 #ifndef is_zero_pfn
461 static inline int is_zero_pfn(unsigned long pfn)
462 {
463 	return pfn == zero_pfn;
464 }
465 #endif
466 
467 #ifndef my_zero_pfn
468 static inline unsigned long my_zero_pfn(unsigned long addr)
469 {
470 	return zero_pfn;
471 }
472 #endif
473 
474 /*
475  * vm_normal_page -- This function gets the "struct page" associated with a pte.
476  *
477  * "Special" mappings do not wish to be associated with a "struct page" (either
478  * it doesn't exist, or it exists but they don't want to touch it). In this
479  * case, NULL is returned here. "Normal" mappings do have a struct page.
480  *
481  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
482  * pte bit, in which case this function is trivial. Secondly, an architecture
483  * may not have a spare pte bit, which requires a more complicated scheme,
484  * described below.
485  *
486  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
487  * special mapping (even if there are underlying and valid "struct pages").
488  * COWed pages of a VM_PFNMAP are always normal.
489  *
490  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
491  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
492  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
493  * mapping will always honor the rule
494  *
495  *	pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
496  *
497  * And for normal mappings this is false.
498  *
499  * This restricts such mappings to be a linear translation from virtual address
500  * to pfn. To get around this restriction, we allow arbitrary mappings so long
501  * as the vma is not a COW mapping; in that case, we know that all ptes are
502  * special (because none can have been COWed).
503  *
504  *
505  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
506  *
507  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
508  * page" backing, however the difference is that _all_ pages with a struct
509  * page (that is, those where pfn_valid is true) are refcounted and considered
510  * normal pages by the VM. The disadvantage is that pages are refcounted
511  * (which can be slower and simply not an option for some PFNMAP users). The
512  * advantage is that we don't have to follow the strict linearity rule of
513  * PFNMAP mappings in order to support COWable mappings.
514  *
515  */
516 #ifdef __HAVE_ARCH_PTE_SPECIAL
517 # define HAVE_PTE_SPECIAL 1
518 #else
519 # define HAVE_PTE_SPECIAL 0
520 #endif
521 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
522 				pte_t pte)
523 {
524 	unsigned long pfn = pte_pfn(pte);
525 
526 	if (HAVE_PTE_SPECIAL) {
527 		if (likely(!pte_special(pte)))
528 			goto check_pfn;
529 		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
530 			return NULL;
531 		if (!is_zero_pfn(pfn))
532 			print_bad_pte(vma, addr, pte, NULL);
533 		return NULL;
534 	}
535 
536 	/* !HAVE_PTE_SPECIAL case follows: */
537 
538 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
539 		if (vma->vm_flags & VM_MIXEDMAP) {
540 			if (!pfn_valid(pfn))
541 				return NULL;
542 			goto out;
543 		} else {
544 			unsigned long off;
545 			off = (addr - vma->vm_start) >> PAGE_SHIFT;
546 			if (pfn == vma->vm_pgoff + off)
547 				return NULL;
548 			if (!is_cow_mapping(vma->vm_flags))
549 				return NULL;
550 		}
551 	}
552 
553 	if (is_zero_pfn(pfn))
554 		return NULL;
555 check_pfn:
556 	if (unlikely(pfn > highest_memmap_pfn)) {
557 		print_bad_pte(vma, addr, pte, NULL);
558 		return NULL;
559 	}
560 
561 	/*
562 	 * NOTE! We still have PageReserved() pages in the page tables.
563 	 * eg. VDSO mappings can cause them to exist.
564 	 */
565 out:
566 	return pfn_to_page(pfn);
567 }
568 
569 /*
570  * copy one vm_area from one task to the other. Assumes the page tables
571  * already present in the new task to be cleared in the whole range
572  * covered by this vma.
573  */
574 
575 static inline void
576 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
577 		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
578 		unsigned long addr, int *rss)
579 {
580 	unsigned long vm_flags = vma->vm_flags;
581 	pte_t pte = *src_pte;
582 	struct page *page;
583 
584 	/* pte contains position in swap or file, so copy. */
585 	if (unlikely(!pte_present(pte))) {
586 		if (!pte_file(pte)) {
587 			swp_entry_t entry = pte_to_swp_entry(pte);
588 
589 			swap_duplicate(entry);
590 			/* make sure dst_mm is on swapoff's mmlist. */
591 			if (unlikely(list_empty(&dst_mm->mmlist))) {
592 				spin_lock(&mmlist_lock);
593 				if (list_empty(&dst_mm->mmlist))
594 					list_add(&dst_mm->mmlist,
595 						 &src_mm->mmlist);
596 				spin_unlock(&mmlist_lock);
597 			}
598 			if (is_write_migration_entry(entry) &&
599 					is_cow_mapping(vm_flags)) {
600 				/*
601 				 * COW mappings require pages in both parent
602 				 * and child to be set to read.
603 				 */
604 				make_migration_entry_read(&entry);
605 				pte = swp_entry_to_pte(entry);
606 				set_pte_at(src_mm, addr, src_pte, pte);
607 			}
608 		}
609 		goto out_set_pte;
610 	}
611 
612 	/*
613 	 * If it's a COW mapping, write protect it both
614 	 * in the parent and the child
615 	 */
616 	if (is_cow_mapping(vm_flags)) {
617 		ptep_set_wrprotect(src_mm, addr, src_pte);
618 		pte = pte_wrprotect(pte);
619 	}
620 
621 	/*
622 	 * If it's a shared mapping, mark it clean in
623 	 * the child
624 	 */
625 	if (vm_flags & VM_SHARED)
626 		pte = pte_mkclean(pte);
627 	pte = pte_mkold(pte);
628 
629 	page = vm_normal_page(vma, addr, pte);
630 	if (page) {
631 		get_page(page);
632 		page_dup_rmap(page);
633 		rss[PageAnon(page)]++;
634 	}
635 
636 out_set_pte:
637 	set_pte_at(dst_mm, addr, dst_pte, pte);
638 }
639 
640 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
641 		pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
642 		unsigned long addr, unsigned long end)
643 {
644 	pte_t *src_pte, *dst_pte;
645 	spinlock_t *src_ptl, *dst_ptl;
646 	int progress = 0;
647 	int rss[2];
648 
649 again:
650 	rss[1] = rss[0] = 0;
651 	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
652 	if (!dst_pte)
653 		return -ENOMEM;
654 	src_pte = pte_offset_map_nested(src_pmd, addr);
655 	src_ptl = pte_lockptr(src_mm, src_pmd);
656 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
657 	arch_enter_lazy_mmu_mode();
658 
659 	do {
660 		/*
661 		 * We are holding two locks at this point - either of them
662 		 * could generate latencies in another task on another CPU.
663 		 */
664 		if (progress >= 32) {
665 			progress = 0;
666 			if (need_resched() ||
667 			    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
668 				break;
669 		}
670 		if (pte_none(*src_pte)) {
671 			progress++;
672 			continue;
673 		}
674 		copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vma, addr, rss);
675 		progress += 8;
676 	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
677 
678 	arch_leave_lazy_mmu_mode();
679 	spin_unlock(src_ptl);
680 	pte_unmap_nested(src_pte - 1);
681 	add_mm_rss(dst_mm, rss[0], rss[1]);
682 	pte_unmap_unlock(dst_pte - 1, dst_ptl);
683 	cond_resched();
684 	if (addr != end)
685 		goto again;
686 	return 0;
687 }
688 
689 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
690 		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
691 		unsigned long addr, unsigned long end)
692 {
693 	pmd_t *src_pmd, *dst_pmd;
694 	unsigned long next;
695 
696 	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
697 	if (!dst_pmd)
698 		return -ENOMEM;
699 	src_pmd = pmd_offset(src_pud, addr);
700 	do {
701 		next = pmd_addr_end(addr, end);
702 		if (pmd_none_or_clear_bad(src_pmd))
703 			continue;
704 		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
705 						vma, addr, next))
706 			return -ENOMEM;
707 	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
708 	return 0;
709 }
710 
711 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
712 		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
713 		unsigned long addr, unsigned long end)
714 {
715 	pud_t *src_pud, *dst_pud;
716 	unsigned long next;
717 
718 	dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
719 	if (!dst_pud)
720 		return -ENOMEM;
721 	src_pud = pud_offset(src_pgd, addr);
722 	do {
723 		next = pud_addr_end(addr, end);
724 		if (pud_none_or_clear_bad(src_pud))
725 			continue;
726 		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
727 						vma, addr, next))
728 			return -ENOMEM;
729 	} while (dst_pud++, src_pud++, addr = next, addr != end);
730 	return 0;
731 }
732 
733 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
734 		struct vm_area_struct *vma)
735 {
736 	pgd_t *src_pgd, *dst_pgd;
737 	unsigned long next;
738 	unsigned long addr = vma->vm_start;
739 	unsigned long end = vma->vm_end;
740 	int ret;
741 
742 	/*
743 	 * Don't copy ptes where a page fault will fill them correctly.
744 	 * Fork becomes much lighter when there are big shared or private
745 	 * readonly mappings. The tradeoff is that copy_page_range is more
746 	 * efficient than faulting.
747 	 */
748 	if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
749 		if (!vma->anon_vma)
750 			return 0;
751 	}
752 
753 	if (is_vm_hugetlb_page(vma))
754 		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
755 
756 	if (unlikely(is_pfn_mapping(vma))) {
757 		/*
758 		 * We do not free on error cases below as remove_vma
759 		 * gets called on error from higher level routine
760 		 */
761 		ret = track_pfn_vma_copy(vma);
762 		if (ret)
763 			return ret;
764 	}
765 
766 	/*
767 	 * We need to invalidate the secondary MMU mappings only when
768 	 * there could be a permission downgrade on the ptes of the
769 	 * parent mm. And a permission downgrade will only happen if
770 	 * is_cow_mapping() returns true.
771 	 */
772 	if (is_cow_mapping(vma->vm_flags))
773 		mmu_notifier_invalidate_range_start(src_mm, addr, end);
774 
775 	ret = 0;
776 	dst_pgd = pgd_offset(dst_mm, addr);
777 	src_pgd = pgd_offset(src_mm, addr);
778 	do {
779 		next = pgd_addr_end(addr, end);
780 		if (pgd_none_or_clear_bad(src_pgd))
781 			continue;
782 		if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
783 					    vma, addr, next))) {
784 			ret = -ENOMEM;
785 			break;
786 		}
787 	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
788 
789 	if (is_cow_mapping(vma->vm_flags))
790 		mmu_notifier_invalidate_range_end(src_mm,
791 						  vma->vm_start, end);
792 	return ret;
793 }
794 
795 static unsigned long zap_pte_range(struct mmu_gather *tlb,
796 				struct vm_area_struct *vma, pmd_t *pmd,
797 				unsigned long addr, unsigned long end,
798 				long *zap_work, struct zap_details *details)
799 {
800 	struct mm_struct *mm = tlb->mm;
801 	pte_t *pte;
802 	spinlock_t *ptl;
803 	int file_rss = 0;
804 	int anon_rss = 0;
805 
806 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
807 	arch_enter_lazy_mmu_mode();
808 	do {
809 		pte_t ptent = *pte;
810 		if (pte_none(ptent)) {
811 			(*zap_work)--;
812 			continue;
813 		}
814 
815 		(*zap_work) -= PAGE_SIZE;
816 
817 		if (pte_present(ptent)) {
818 			struct page *page;
819 
820 			page = vm_normal_page(vma, addr, ptent);
821 			if (unlikely(details) && page) {
822 				/*
823 				 * unmap_shared_mapping_pages() wants to
824 				 * invalidate cache without truncating:
825 				 * unmap shared but keep private pages.
826 				 */
827 				if (details->check_mapping &&
828 				    details->check_mapping != page->mapping)
829 					continue;
830 				/*
831 				 * Each page->index must be checked when
832 				 * invalidating or truncating nonlinear.
833 				 */
834 				if (details->nonlinear_vma &&
835 				    (page->index < details->first_index ||
836 				     page->index > details->last_index))
837 					continue;
838 			}
839 			ptent = ptep_get_and_clear_full(mm, addr, pte,
840 							tlb->fullmm);
841 			tlb_remove_tlb_entry(tlb, pte, addr);
842 			if (unlikely(!page))
843 				continue;
844 			if (unlikely(details) && details->nonlinear_vma
845 			    && linear_page_index(details->nonlinear_vma,
846 						addr) != page->index)
847 				set_pte_at(mm, addr, pte,
848 					   pgoff_to_pte(page->index));
849 			if (PageAnon(page))
850 				anon_rss--;
851 			else {
852 				if (pte_dirty(ptent))
853 					set_page_dirty(page);
854 				if (pte_young(ptent) &&
855 				    likely(!VM_SequentialReadHint(vma)))
856 					mark_page_accessed(page);
857 				file_rss--;
858 			}
859 			page_remove_rmap(page);
860 			if (unlikely(page_mapcount(page) < 0))
861 				print_bad_pte(vma, addr, ptent, page);
862 			tlb_remove_page(tlb, page);
863 			continue;
864 		}
865 		/*
866 		 * If details->check_mapping, we leave swap entries;
867 		 * if details->nonlinear_vma, we leave file entries.
868 		 */
869 		if (unlikely(details))
870 			continue;
871 		if (pte_file(ptent)) {
872 			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
873 				print_bad_pte(vma, addr, ptent, NULL);
874 		} else if
875 		  (unlikely(!free_swap_and_cache(pte_to_swp_entry(ptent))))
876 			print_bad_pte(vma, addr, ptent, NULL);
877 		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
878 	} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
879 
880 	add_mm_rss(mm, file_rss, anon_rss);
881 	arch_leave_lazy_mmu_mode();
882 	pte_unmap_unlock(pte - 1, ptl);
883 
884 	return addr;
885 }
886 
887 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
888 				struct vm_area_struct *vma, pud_t *pud,
889 				unsigned long addr, unsigned long end,
890 				long *zap_work, struct zap_details *details)
891 {
892 	pmd_t *pmd;
893 	unsigned long next;
894 
895 	pmd = pmd_offset(pud, addr);
896 	do {
897 		next = pmd_addr_end(addr, end);
898 		if (pmd_none_or_clear_bad(pmd)) {
899 			(*zap_work)--;
900 			continue;
901 		}
902 		next = zap_pte_range(tlb, vma, pmd, addr, next,
903 						zap_work, details);
904 	} while (pmd++, addr = next, (addr != end && *zap_work > 0));
905 
906 	return addr;
907 }
908 
909 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
910 				struct vm_area_struct *vma, pgd_t *pgd,
911 				unsigned long addr, unsigned long end,
912 				long *zap_work, struct zap_details *details)
913 {
914 	pud_t *pud;
915 	unsigned long next;
916 
917 	pud = pud_offset(pgd, addr);
918 	do {
919 		next = pud_addr_end(addr, end);
920 		if (pud_none_or_clear_bad(pud)) {
921 			(*zap_work)--;
922 			continue;
923 		}
924 		next = zap_pmd_range(tlb, vma, pud, addr, next,
925 						zap_work, details);
926 	} while (pud++, addr = next, (addr != end && *zap_work > 0));
927 
928 	return addr;
929 }
930 
931 static unsigned long unmap_page_range(struct mmu_gather *tlb,
932 				struct vm_area_struct *vma,
933 				unsigned long addr, unsigned long end,
934 				long *zap_work, struct zap_details *details)
935 {
936 	pgd_t *pgd;
937 	unsigned long next;
938 
939 	if (details && !details->check_mapping && !details->nonlinear_vma)
940 		details = NULL;
941 
942 	BUG_ON(addr >= end);
943 	tlb_start_vma(tlb, vma);
944 	pgd = pgd_offset(vma->vm_mm, addr);
945 	do {
946 		next = pgd_addr_end(addr, end);
947 		if (pgd_none_or_clear_bad(pgd)) {
948 			(*zap_work)--;
949 			continue;
950 		}
951 		next = zap_pud_range(tlb, vma, pgd, addr, next,
952 						zap_work, details);
953 	} while (pgd++, addr = next, (addr != end && *zap_work > 0));
954 	tlb_end_vma(tlb, vma);
955 
956 	return addr;
957 }
958 
959 #ifdef CONFIG_PREEMPT
960 # define ZAP_BLOCK_SIZE	(8 * PAGE_SIZE)
961 #else
962 /* No preempt: go for improved straight-line efficiency */
963 # define ZAP_BLOCK_SIZE	(1024 * PAGE_SIZE)
964 #endif
965 
966 /**
967  * unmap_vmas - unmap a range of memory covered by a list of vma's
968  * @tlbp: address of the caller's struct mmu_gather
969  * @vma: the starting vma
970  * @start_addr: virtual address at which to start unmapping
971  * @end_addr: virtual address at which to end unmapping
972  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
973  * @details: details of nonlinear truncation or shared cache invalidation
974  *
975  * Returns the end address of the unmapping (restart addr if interrupted).
976  *
977  * Unmap all pages in the vma list.
978  *
979  * We aim to not hold locks for too long (for scheduling latency reasons).
980  * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
981  * return the ending mmu_gather to the caller.
982  *
983  * Only addresses between `start' and `end' will be unmapped.
984  *
985  * The VMA list must be sorted in ascending virtual address order.
986  *
987  * unmap_vmas() assumes that the caller will flush the whole unmapped address
988  * range after unmap_vmas() returns.  So the only responsibility here is to
989  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
990  * drops the lock and schedules.
991  */
992 unsigned long unmap_vmas(struct mmu_gather **tlbp,
993 		struct vm_area_struct *vma, unsigned long start_addr,
994 		unsigned long end_addr, unsigned long *nr_accounted,
995 		struct zap_details *details)
996 {
997 	long zap_work = ZAP_BLOCK_SIZE;
998 	unsigned long tlb_start = 0;	/* For tlb_finish_mmu */
999 	int tlb_start_valid = 0;
1000 	unsigned long start = start_addr;
1001 	spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
1002 	int fullmm = (*tlbp)->fullmm;
1003 	struct mm_struct *mm = vma->vm_mm;
1004 
1005 	mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1006 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
1007 		unsigned long end;
1008 
1009 		start = max(vma->vm_start, start_addr);
1010 		if (start >= vma->vm_end)
1011 			continue;
1012 		end = min(vma->vm_end, end_addr);
1013 		if (end <= vma->vm_start)
1014 			continue;
1015 
1016 		if (vma->vm_flags & VM_ACCOUNT)
1017 			*nr_accounted += (end - start) >> PAGE_SHIFT;
1018 
1019 		if (unlikely(is_pfn_mapping(vma)))
1020 			untrack_pfn_vma(vma, 0, 0);
1021 
1022 		while (start != end) {
1023 			if (!tlb_start_valid) {
1024 				tlb_start = start;
1025 				tlb_start_valid = 1;
1026 			}
1027 
1028 			if (unlikely(is_vm_hugetlb_page(vma))) {
1029 				/*
1030 				 * It is undesirable to test vma->vm_file as it
1031 				 * should be non-null for valid hugetlb area.
1032 				 * However, vm_file will be NULL in the error
1033 				 * cleanup path of do_mmap_pgoff. When
1034 				 * hugetlbfs ->mmap method fails,
1035 				 * do_mmap_pgoff() nullifies vma->vm_file
1036 				 * before calling this function to clean up.
1037 				 * Since no pte has actually been setup, it is
1038 				 * safe to do nothing in this case.
1039 				 */
1040 				if (vma->vm_file) {
1041 					unmap_hugepage_range(vma, start, end, NULL);
1042 					zap_work -= (end - start) /
1043 					pages_per_huge_page(hstate_vma(vma));
1044 				}
1045 
1046 				start = end;
1047 			} else
1048 				start = unmap_page_range(*tlbp, vma,
1049 						start, end, &zap_work, details);
1050 
1051 			if (zap_work > 0) {
1052 				BUG_ON(start != end);
1053 				break;
1054 			}
1055 
1056 			tlb_finish_mmu(*tlbp, tlb_start, start);
1057 
1058 			if (need_resched() ||
1059 				(i_mmap_lock && spin_needbreak(i_mmap_lock))) {
1060 				if (i_mmap_lock) {
1061 					*tlbp = NULL;
1062 					goto out;
1063 				}
1064 				cond_resched();
1065 			}
1066 
1067 			*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
1068 			tlb_start_valid = 0;
1069 			zap_work = ZAP_BLOCK_SIZE;
1070 		}
1071 	}
1072 out:
1073 	mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1074 	return start;	/* which is now the end (or restart) address */
1075 }
1076 
1077 /**
1078  * zap_page_range - remove user pages in a given range
1079  * @vma: vm_area_struct holding the applicable pages
1080  * @address: starting address of pages to zap
1081  * @size: number of bytes to zap
1082  * @details: details of nonlinear truncation or shared cache invalidation
1083  */
1084 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
1085 		unsigned long size, struct zap_details *details)
1086 {
1087 	struct mm_struct *mm = vma->vm_mm;
1088 	struct mmu_gather *tlb;
1089 	unsigned long end = address + size;
1090 	unsigned long nr_accounted = 0;
1091 
1092 	lru_add_drain();
1093 	tlb = tlb_gather_mmu(mm, 0);
1094 	update_hiwater_rss(mm);
1095 	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
1096 	if (tlb)
1097 		tlb_finish_mmu(tlb, address, end);
1098 	return end;
1099 }
1100 
1101 /**
1102  * zap_vma_ptes - remove ptes mapping the vma
1103  * @vma: vm_area_struct holding ptes to be zapped
1104  * @address: starting address of pages to zap
1105  * @size: number of bytes to zap
1106  *
1107  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1108  *
1109  * The entire address range must be fully contained within the vma.
1110  *
1111  * Returns 0 if successful.
1112  */
1113 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1114 		unsigned long size)
1115 {
1116 	if (address < vma->vm_start || address + size > vma->vm_end ||
1117 	    		!(vma->vm_flags & VM_PFNMAP))
1118 		return -1;
1119 	zap_page_range(vma, address, size, NULL);
1120 	return 0;
1121 }
1122 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1123 
1124 /*
1125  * Do a quick page-table lookup for a single page.
1126  */
1127 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1128 			unsigned int flags)
1129 {
1130 	pgd_t *pgd;
1131 	pud_t *pud;
1132 	pmd_t *pmd;
1133 	pte_t *ptep, pte;
1134 	spinlock_t *ptl;
1135 	struct page *page;
1136 	struct mm_struct *mm = vma->vm_mm;
1137 
1138 	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1139 	if (!IS_ERR(page)) {
1140 		BUG_ON(flags & FOLL_GET);
1141 		goto out;
1142 	}
1143 
1144 	page = NULL;
1145 	pgd = pgd_offset(mm, address);
1146 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1147 		goto no_page_table;
1148 
1149 	pud = pud_offset(pgd, address);
1150 	if (pud_none(*pud))
1151 		goto no_page_table;
1152 	if (pud_huge(*pud)) {
1153 		BUG_ON(flags & FOLL_GET);
1154 		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1155 		goto out;
1156 	}
1157 	if (unlikely(pud_bad(*pud)))
1158 		goto no_page_table;
1159 
1160 	pmd = pmd_offset(pud, address);
1161 	if (pmd_none(*pmd))
1162 		goto no_page_table;
1163 	if (pmd_huge(*pmd)) {
1164 		BUG_ON(flags & FOLL_GET);
1165 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1166 		goto out;
1167 	}
1168 	if (unlikely(pmd_bad(*pmd)))
1169 		goto no_page_table;
1170 
1171 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1172 
1173 	pte = *ptep;
1174 	if (!pte_present(pte))
1175 		goto no_page;
1176 	if ((flags & FOLL_WRITE) && !pte_write(pte))
1177 		goto unlock;
1178 
1179 	page = vm_normal_page(vma, address, pte);
1180 	if (unlikely(!page)) {
1181 		if ((flags & FOLL_DUMP) ||
1182 		    !is_zero_pfn(pte_pfn(pte)))
1183 			goto bad_page;
1184 		page = pte_page(pte);
1185 	}
1186 
1187 	if (flags & FOLL_GET)
1188 		get_page(page);
1189 	if (flags & FOLL_TOUCH) {
1190 		if ((flags & FOLL_WRITE) &&
1191 		    !pte_dirty(pte) && !PageDirty(page))
1192 			set_page_dirty(page);
1193 		/*
1194 		 * pte_mkyoung() would be more correct here, but atomic care
1195 		 * is needed to avoid losing the dirty bit: it is easier to use
1196 		 * mark_page_accessed().
1197 		 */
1198 		mark_page_accessed(page);
1199 	}
1200 unlock:
1201 	pte_unmap_unlock(ptep, ptl);
1202 out:
1203 	return page;
1204 
1205 bad_page:
1206 	pte_unmap_unlock(ptep, ptl);
1207 	return ERR_PTR(-EFAULT);
1208 
1209 no_page:
1210 	pte_unmap_unlock(ptep, ptl);
1211 	if (!pte_none(pte))
1212 		return page;
1213 
1214 no_page_table:
1215 	/*
1216 	 * When core dumping an enormous anonymous area that nobody
1217 	 * has touched so far, we don't want to allocate unnecessary pages or
1218 	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
1219 	 * then get_dump_page() will return NULL to leave a hole in the dump.
1220 	 * But we can only make this optimization where a hole would surely
1221 	 * be zero-filled if handle_mm_fault() actually did handle it.
1222 	 */
1223 	if ((flags & FOLL_DUMP) &&
1224 	    (!vma->vm_ops || !vma->vm_ops->fault))
1225 		return ERR_PTR(-EFAULT);
1226 	return page;
1227 }
1228 
1229 int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1230 		     unsigned long start, int nr_pages, unsigned int gup_flags,
1231 		     struct page **pages, struct vm_area_struct **vmas)
1232 {
1233 	int i;
1234 	unsigned long vm_flags;
1235 
1236 	if (nr_pages <= 0)
1237 		return 0;
1238 
1239 	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1240 
1241 	/*
1242 	 * Require read or write permissions.
1243 	 * If FOLL_FORCE is set, we only require the "MAY" flags.
1244 	 */
1245 	vm_flags  = (gup_flags & FOLL_WRITE) ?
1246 			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1247 	vm_flags &= (gup_flags & FOLL_FORCE) ?
1248 			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1249 	i = 0;
1250 
1251 	do {
1252 		struct vm_area_struct *vma;
1253 
1254 		vma = find_extend_vma(mm, start);
1255 		if (!vma && in_gate_area(tsk, start)) {
1256 			unsigned long pg = start & PAGE_MASK;
1257 			struct vm_area_struct *gate_vma = get_gate_vma(tsk);
1258 			pgd_t *pgd;
1259 			pud_t *pud;
1260 			pmd_t *pmd;
1261 			pte_t *pte;
1262 
1263 			/* user gate pages are read-only */
1264 			if (gup_flags & FOLL_WRITE)
1265 				return i ? : -EFAULT;
1266 			if (pg > TASK_SIZE)
1267 				pgd = pgd_offset_k(pg);
1268 			else
1269 				pgd = pgd_offset_gate(mm, pg);
1270 			BUG_ON(pgd_none(*pgd));
1271 			pud = pud_offset(pgd, pg);
1272 			BUG_ON(pud_none(*pud));
1273 			pmd = pmd_offset(pud, pg);
1274 			if (pmd_none(*pmd))
1275 				return i ? : -EFAULT;
1276 			pte = pte_offset_map(pmd, pg);
1277 			if (pte_none(*pte)) {
1278 				pte_unmap(pte);
1279 				return i ? : -EFAULT;
1280 			}
1281 			if (pages) {
1282 				struct page *page = vm_normal_page(gate_vma, start, *pte);
1283 				pages[i] = page;
1284 				if (page)
1285 					get_page(page);
1286 			}
1287 			pte_unmap(pte);
1288 			if (vmas)
1289 				vmas[i] = gate_vma;
1290 			i++;
1291 			start += PAGE_SIZE;
1292 			nr_pages--;
1293 			continue;
1294 		}
1295 
1296 		if (!vma ||
1297 		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1298 		    !(vm_flags & vma->vm_flags))
1299 			return i ? : -EFAULT;
1300 
1301 		if (is_vm_hugetlb_page(vma)) {
1302 			i = follow_hugetlb_page(mm, vma, pages, vmas,
1303 					&start, &nr_pages, i, gup_flags);
1304 			continue;
1305 		}
1306 
1307 		do {
1308 			struct page *page;
1309 			unsigned int foll_flags = gup_flags;
1310 
1311 			/*
1312 			 * If we have a pending SIGKILL, don't keep faulting
1313 			 * pages and potentially allocating memory.
1314 			 */
1315 			if (unlikely(fatal_signal_pending(current)))
1316 				return i ? i : -ERESTARTSYS;
1317 
1318 			cond_resched();
1319 			while (!(page = follow_page(vma, start, foll_flags))) {
1320 				int ret;
1321 
1322 				ret = handle_mm_fault(mm, vma, start,
1323 					(foll_flags & FOLL_WRITE) ?
1324 					FAULT_FLAG_WRITE : 0);
1325 
1326 				if (ret & VM_FAULT_ERROR) {
1327 					if (ret & VM_FAULT_OOM)
1328 						return i ? i : -ENOMEM;
1329 					if (ret &
1330 					    (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))
1331 						return i ? i : -EFAULT;
1332 					BUG();
1333 				}
1334 				if (ret & VM_FAULT_MAJOR)
1335 					tsk->maj_flt++;
1336 				else
1337 					tsk->min_flt++;
1338 
1339 				/*
1340 				 * The VM_FAULT_WRITE bit tells us that
1341 				 * do_wp_page has broken COW when necessary,
1342 				 * even if maybe_mkwrite decided not to set
1343 				 * pte_write. We can thus safely do subsequent
1344 				 * page lookups as if they were reads. But only
1345 				 * do so when looping for pte_write is futile:
1346 				 * in some cases userspace may also be wanting
1347 				 * to write to the gotten user page, which a
1348 				 * read fault here might prevent (a readonly
1349 				 * page might get reCOWed by userspace write).
1350 				 */
1351 				if ((ret & VM_FAULT_WRITE) &&
1352 				    !(vma->vm_flags & VM_WRITE))
1353 					foll_flags &= ~FOLL_WRITE;
1354 
1355 				cond_resched();
1356 			}
1357 			if (IS_ERR(page))
1358 				return i ? i : PTR_ERR(page);
1359 			if (pages) {
1360 				pages[i] = page;
1361 
1362 				flush_anon_page(vma, page, start);
1363 				flush_dcache_page(page);
1364 			}
1365 			if (vmas)
1366 				vmas[i] = vma;
1367 			i++;
1368 			start += PAGE_SIZE;
1369 			nr_pages--;
1370 		} while (nr_pages && start < vma->vm_end);
1371 	} while (nr_pages);
1372 	return i;
1373 }
1374 
1375 /**
1376  * get_user_pages() - pin user pages in memory
1377  * @tsk:	task_struct of target task
1378  * @mm:		mm_struct of target mm
1379  * @start:	starting user address
1380  * @nr_pages:	number of pages from start to pin
1381  * @write:	whether pages will be written to by the caller
1382  * @force:	whether to force write access even if user mapping is
1383  *		readonly. This will result in the page being COWed even
1384  *		in MAP_SHARED mappings. You do not want this.
1385  * @pages:	array that receives pointers to the pages pinned.
1386  *		Should be at least nr_pages long. Or NULL, if caller
1387  *		only intends to ensure the pages are faulted in.
1388  * @vmas:	array of pointers to vmas corresponding to each page.
1389  *		Or NULL if the caller does not require them.
1390  *
1391  * Returns number of pages pinned. This may be fewer than the number
1392  * requested. If nr_pages is 0 or negative, returns 0. If no pages
1393  * were pinned, returns -errno. Each page returned must be released
1394  * with a put_page() call when it is finished with. vmas will only
1395  * remain valid while mmap_sem is held.
1396  *
1397  * Must be called with mmap_sem held for read or write.
1398  *
1399  * get_user_pages walks a process's page tables and takes a reference to
1400  * each struct page that each user address corresponds to at a given
1401  * instant. That is, it takes the page that would be accessed if a user
1402  * thread accesses the given user virtual address at that instant.
1403  *
1404  * This does not guarantee that the page exists in the user mappings when
1405  * get_user_pages returns, and there may even be a completely different
1406  * page there in some cases (eg. if mmapped pagecache has been invalidated
1407  * and subsequently re faulted). However it does guarantee that the page
1408  * won't be freed completely. And mostly callers simply care that the page
1409  * contains data that was valid *at some point in time*. Typically, an IO
1410  * or similar operation cannot guarantee anything stronger anyway because
1411  * locks can't be held over the syscall boundary.
1412  *
1413  * If write=0, the page must not be written to. If the page is written to,
1414  * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
1415  * after the page is finished with, and before put_page is called.
1416  *
1417  * get_user_pages is typically used for fewer-copy IO operations, to get a
1418  * handle on the memory by some means other than accesses via the user virtual
1419  * addresses. The pages may be submitted for DMA to devices or accessed via
1420  * their kernel linear mapping (via the kmap APIs). Care should be taken to
1421  * use the correct cache flushing APIs.
1422  *
1423  * See also get_user_pages_fast, for performance critical applications.
1424  */
1425 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1426 		unsigned long start, int nr_pages, int write, int force,
1427 		struct page **pages, struct vm_area_struct **vmas)
1428 {
1429 	int flags = FOLL_TOUCH;
1430 
1431 	if (pages)
1432 		flags |= FOLL_GET;
1433 	if (write)
1434 		flags |= FOLL_WRITE;
1435 	if (force)
1436 		flags |= FOLL_FORCE;
1437 
1438 	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
1439 }
1440 EXPORT_SYMBOL(get_user_pages);
1441 
1442 /**
1443  * get_dump_page() - pin user page in memory while writing it to core dump
1444  * @addr: user address
1445  *
1446  * Returns struct page pointer of user page pinned for dump,
1447  * to be freed afterwards by page_cache_release() or put_page().
1448  *
1449  * Returns NULL on any kind of failure - a hole must then be inserted into
1450  * the corefile, to preserve alignment with its headers; and also returns
1451  * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1452  * allowing a hole to be left in the corefile to save diskspace.
1453  *
1454  * Called without mmap_sem, but after all other threads have been killed.
1455  */
1456 #ifdef CONFIG_ELF_CORE
1457 struct page *get_dump_page(unsigned long addr)
1458 {
1459 	struct vm_area_struct *vma;
1460 	struct page *page;
1461 
1462 	if (__get_user_pages(current, current->mm, addr, 1,
1463 			FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)
1464 		return NULL;
1465 	flush_cache_page(vma, addr, page_to_pfn(page));
1466 	return page;
1467 }
1468 #endif /* CONFIG_ELF_CORE */
1469 
1470 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
1471 			spinlock_t **ptl)
1472 {
1473 	pgd_t * pgd = pgd_offset(mm, addr);
1474 	pud_t * pud = pud_alloc(mm, pgd, addr);
1475 	if (pud) {
1476 		pmd_t * pmd = pmd_alloc(mm, pud, addr);
1477 		if (pmd)
1478 			return pte_alloc_map_lock(mm, pmd, addr, ptl);
1479 	}
1480 	return NULL;
1481 }
1482 
1483 /*
1484  * This is the old fallback for page remapping.
1485  *
1486  * For historical reasons, it only allows reserved pages. Only
1487  * old drivers should use this, and they needed to mark their
1488  * pages reserved for the old functions anyway.
1489  */
1490 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1491 			struct page *page, pgprot_t prot)
1492 {
1493 	struct mm_struct *mm = vma->vm_mm;
1494 	int retval;
1495 	pte_t *pte;
1496 	spinlock_t *ptl;
1497 
1498 	retval = -EINVAL;
1499 	if (PageAnon(page))
1500 		goto out;
1501 	retval = -ENOMEM;
1502 	flush_dcache_page(page);
1503 	pte = get_locked_pte(mm, addr, &ptl);
1504 	if (!pte)
1505 		goto out;
1506 	retval = -EBUSY;
1507 	if (!pte_none(*pte))
1508 		goto out_unlock;
1509 
1510 	/* Ok, finally just insert the thing.. */
1511 	get_page(page);
1512 	inc_mm_counter(mm, file_rss);
1513 	page_add_file_rmap(page);
1514 	set_pte_at(mm, addr, pte, mk_pte(page, prot));
1515 
1516 	retval = 0;
1517 	pte_unmap_unlock(pte, ptl);
1518 	return retval;
1519 out_unlock:
1520 	pte_unmap_unlock(pte, ptl);
1521 out:
1522 	return retval;
1523 }
1524 
1525 /**
1526  * vm_insert_page - insert single page into user vma
1527  * @vma: user vma to map to
1528  * @addr: target user address of this page
1529  * @page: source kernel page
1530  *
1531  * This allows drivers to insert individual pages they've allocated
1532  * into a user vma.
1533  *
1534  * The page has to be a nice clean _individual_ kernel allocation.
1535  * If you allocate a compound page, you need to have marked it as
1536  * such (__GFP_COMP), or manually just split the page up yourself
1537  * (see split_page()).
1538  *
1539  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1540  * took an arbitrary page protection parameter. This doesn't allow
1541  * that. Your vma protection will have to be set up correctly, which
1542  * means that if you want a shared writable mapping, you'd better
1543  * ask for a shared writable mapping!
1544  *
1545  * The page does not need to be reserved.
1546  */
1547 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1548 			struct page *page)
1549 {
1550 	if (addr < vma->vm_start || addr >= vma->vm_end)
1551 		return -EFAULT;
1552 	if (!page_count(page))
1553 		return -EINVAL;
1554 	vma->vm_flags |= VM_INSERTPAGE;
1555 	return insert_page(vma, addr, page, vma->vm_page_prot);
1556 }
1557 EXPORT_SYMBOL(vm_insert_page);
1558 
1559 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1560 			unsigned long pfn, pgprot_t prot)
1561 {
1562 	struct mm_struct *mm = vma->vm_mm;
1563 	int retval;
1564 	pte_t *pte, entry;
1565 	spinlock_t *ptl;
1566 
1567 	retval = -ENOMEM;
1568 	pte = get_locked_pte(mm, addr, &ptl);
1569 	if (!pte)
1570 		goto out;
1571 	retval = -EBUSY;
1572 	if (!pte_none(*pte))
1573 		goto out_unlock;
1574 
1575 	/* Ok, finally just insert the thing.. */
1576 	entry = pte_mkspecial(pfn_pte(pfn, prot));
1577 	set_pte_at(mm, addr, pte, entry);
1578 	update_mmu_cache(vma, addr, entry); /* XXX: why not for insert_page? */
1579 
1580 	retval = 0;
1581 out_unlock:
1582 	pte_unmap_unlock(pte, ptl);
1583 out:
1584 	return retval;
1585 }
1586 
1587 /**
1588  * vm_insert_pfn - insert single pfn into user vma
1589  * @vma: user vma to map to
1590  * @addr: target user address of this page
1591  * @pfn: source kernel pfn
1592  *
1593  * Similar to vm_inert_page, this allows drivers to insert individual pages
1594  * they've allocated into a user vma. Same comments apply.
1595  *
1596  * This function should only be called from a vm_ops->fault handler, and
1597  * in that case the handler should return NULL.
1598  *
1599  * vma cannot be a COW mapping.
1600  *
1601  * As this is called only for pages that do not currently exist, we
1602  * do not need to flush old virtual caches or the TLB.
1603  */
1604 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1605 			unsigned long pfn)
1606 {
1607 	int ret;
1608 	pgprot_t pgprot = vma->vm_page_prot;
1609 	/*
1610 	 * Technically, architectures with pte_special can avoid all these
1611 	 * restrictions (same for remap_pfn_range).  However we would like
1612 	 * consistency in testing and feature parity among all, so we should
1613 	 * try to keep these invariants in place for everybody.
1614 	 */
1615 	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1616 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1617 						(VM_PFNMAP|VM_MIXEDMAP));
1618 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1619 	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1620 
1621 	if (addr < vma->vm_start || addr >= vma->vm_end)
1622 		return -EFAULT;
1623 	if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
1624 		return -EINVAL;
1625 
1626 	ret = insert_pfn(vma, addr, pfn, pgprot);
1627 
1628 	if (ret)
1629 		untrack_pfn_vma(vma, pfn, PAGE_SIZE);
1630 
1631 	return ret;
1632 }
1633 EXPORT_SYMBOL(vm_insert_pfn);
1634 
1635 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1636 			unsigned long pfn)
1637 {
1638 	BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1639 
1640 	if (addr < vma->vm_start || addr >= vma->vm_end)
1641 		return -EFAULT;
1642 
1643 	/*
1644 	 * If we don't have pte special, then we have to use the pfn_valid()
1645 	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1646 	 * refcount the page if pfn_valid is true (hence insert_page rather
1647 	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1648 	 * without pte special, it would there be refcounted as a normal page.
1649 	 */
1650 	if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1651 		struct page *page;
1652 
1653 		page = pfn_to_page(pfn);
1654 		return insert_page(vma, addr, page, vma->vm_page_prot);
1655 	}
1656 	return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1657 }
1658 EXPORT_SYMBOL(vm_insert_mixed);
1659 
1660 /*
1661  * maps a range of physical memory into the requested pages. the old
1662  * mappings are removed. any references to nonexistent pages results
1663  * in null mappings (currently treated as "copy-on-access")
1664  */
1665 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1666 			unsigned long addr, unsigned long end,
1667 			unsigned long pfn, pgprot_t prot)
1668 {
1669 	pte_t *pte;
1670 	spinlock_t *ptl;
1671 
1672 	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1673 	if (!pte)
1674 		return -ENOMEM;
1675 	arch_enter_lazy_mmu_mode();
1676 	do {
1677 		BUG_ON(!pte_none(*pte));
1678 		set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1679 		pfn++;
1680 	} while (pte++, addr += PAGE_SIZE, addr != end);
1681 	arch_leave_lazy_mmu_mode();
1682 	pte_unmap_unlock(pte - 1, ptl);
1683 	return 0;
1684 }
1685 
1686 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1687 			unsigned long addr, unsigned long end,
1688 			unsigned long pfn, pgprot_t prot)
1689 {
1690 	pmd_t *pmd;
1691 	unsigned long next;
1692 
1693 	pfn -= addr >> PAGE_SHIFT;
1694 	pmd = pmd_alloc(mm, pud, addr);
1695 	if (!pmd)
1696 		return -ENOMEM;
1697 	do {
1698 		next = pmd_addr_end(addr, end);
1699 		if (remap_pte_range(mm, pmd, addr, next,
1700 				pfn + (addr >> PAGE_SHIFT), prot))
1701 			return -ENOMEM;
1702 	} while (pmd++, addr = next, addr != end);
1703 	return 0;
1704 }
1705 
1706 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1707 			unsigned long addr, unsigned long end,
1708 			unsigned long pfn, pgprot_t prot)
1709 {
1710 	pud_t *pud;
1711 	unsigned long next;
1712 
1713 	pfn -= addr >> PAGE_SHIFT;
1714 	pud = pud_alloc(mm, pgd, addr);
1715 	if (!pud)
1716 		return -ENOMEM;
1717 	do {
1718 		next = pud_addr_end(addr, end);
1719 		if (remap_pmd_range(mm, pud, addr, next,
1720 				pfn + (addr >> PAGE_SHIFT), prot))
1721 			return -ENOMEM;
1722 	} while (pud++, addr = next, addr != end);
1723 	return 0;
1724 }
1725 
1726 /**
1727  * remap_pfn_range - remap kernel memory to userspace
1728  * @vma: user vma to map to
1729  * @addr: target user address to start at
1730  * @pfn: physical address of kernel memory
1731  * @size: size of map area
1732  * @prot: page protection flags for this mapping
1733  *
1734  *  Note: this is only safe if the mm semaphore is held when called.
1735  */
1736 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1737 		    unsigned long pfn, unsigned long size, pgprot_t prot)
1738 {
1739 	pgd_t *pgd;
1740 	unsigned long next;
1741 	unsigned long end = addr + PAGE_ALIGN(size);
1742 	struct mm_struct *mm = vma->vm_mm;
1743 	int err;
1744 
1745 	/*
1746 	 * Physically remapped pages are special. Tell the
1747 	 * rest of the world about it:
1748 	 *   VM_IO tells people not to look at these pages
1749 	 *	(accesses can have side effects).
1750 	 *   VM_RESERVED is specified all over the place, because
1751 	 *	in 2.4 it kept swapout's vma scan off this vma; but
1752 	 *	in 2.6 the LRU scan won't even find its pages, so this
1753 	 *	flag means no more than count its pages in reserved_vm,
1754 	 * 	and omit it from core dump, even when VM_IO turned off.
1755 	 *   VM_PFNMAP tells the core MM that the base pages are just
1756 	 *	raw PFN mappings, and do not have a "struct page" associated
1757 	 *	with them.
1758 	 *
1759 	 * There's a horrible special case to handle copy-on-write
1760 	 * behaviour that some programs depend on. We mark the "original"
1761 	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1762 	 */
1763 	if (addr == vma->vm_start && end == vma->vm_end) {
1764 		vma->vm_pgoff = pfn;
1765 		vma->vm_flags |= VM_PFN_AT_MMAP;
1766 	} else if (is_cow_mapping(vma->vm_flags))
1767 		return -EINVAL;
1768 
1769 	vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1770 
1771 	err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
1772 	if (err) {
1773 		/*
1774 		 * To indicate that track_pfn related cleanup is not
1775 		 * needed from higher level routine calling unmap_vmas
1776 		 */
1777 		vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
1778 		vma->vm_flags &= ~VM_PFN_AT_MMAP;
1779 		return -EINVAL;
1780 	}
1781 
1782 	BUG_ON(addr >= end);
1783 	pfn -= addr >> PAGE_SHIFT;
1784 	pgd = pgd_offset(mm, addr);
1785 	flush_cache_range(vma, addr, end);
1786 	do {
1787 		next = pgd_addr_end(addr, end);
1788 		err = remap_pud_range(mm, pgd, addr, next,
1789 				pfn + (addr >> PAGE_SHIFT), prot);
1790 		if (err)
1791 			break;
1792 	} while (pgd++, addr = next, addr != end);
1793 
1794 	if (err)
1795 		untrack_pfn_vma(vma, pfn, PAGE_ALIGN(size));
1796 
1797 	return err;
1798 }
1799 EXPORT_SYMBOL(remap_pfn_range);
1800 
1801 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1802 				     unsigned long addr, unsigned long end,
1803 				     pte_fn_t fn, void *data)
1804 {
1805 	pte_t *pte;
1806 	int err;
1807 	pgtable_t token;
1808 	spinlock_t *uninitialized_var(ptl);
1809 
1810 	pte = (mm == &init_mm) ?
1811 		pte_alloc_kernel(pmd, addr) :
1812 		pte_alloc_map_lock(mm, pmd, addr, &ptl);
1813 	if (!pte)
1814 		return -ENOMEM;
1815 
1816 	BUG_ON(pmd_huge(*pmd));
1817 
1818 	arch_enter_lazy_mmu_mode();
1819 
1820 	token = pmd_pgtable(*pmd);
1821 
1822 	do {
1823 		err = fn(pte, token, addr, data);
1824 		if (err)
1825 			break;
1826 	} while (pte++, addr += PAGE_SIZE, addr != end);
1827 
1828 	arch_leave_lazy_mmu_mode();
1829 
1830 	if (mm != &init_mm)
1831 		pte_unmap_unlock(pte-1, ptl);
1832 	return err;
1833 }
1834 
1835 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1836 				     unsigned long addr, unsigned long end,
1837 				     pte_fn_t fn, void *data)
1838 {
1839 	pmd_t *pmd;
1840 	unsigned long next;
1841 	int err;
1842 
1843 	BUG_ON(pud_huge(*pud));
1844 
1845 	pmd = pmd_alloc(mm, pud, addr);
1846 	if (!pmd)
1847 		return -ENOMEM;
1848 	do {
1849 		next = pmd_addr_end(addr, end);
1850 		err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1851 		if (err)
1852 			break;
1853 	} while (pmd++, addr = next, addr != end);
1854 	return err;
1855 }
1856 
1857 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1858 				     unsigned long addr, unsigned long end,
1859 				     pte_fn_t fn, void *data)
1860 {
1861 	pud_t *pud;
1862 	unsigned long next;
1863 	int err;
1864 
1865 	pud = pud_alloc(mm, pgd, addr);
1866 	if (!pud)
1867 		return -ENOMEM;
1868 	do {
1869 		next = pud_addr_end(addr, end);
1870 		err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1871 		if (err)
1872 			break;
1873 	} while (pud++, addr = next, addr != end);
1874 	return err;
1875 }
1876 
1877 /*
1878  * Scan a region of virtual memory, filling in page tables as necessary
1879  * and calling a provided function on each leaf page table.
1880  */
1881 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1882 			unsigned long size, pte_fn_t fn, void *data)
1883 {
1884 	pgd_t *pgd;
1885 	unsigned long next;
1886 	unsigned long start = addr, end = addr + size;
1887 	int err;
1888 
1889 	BUG_ON(addr >= end);
1890 	mmu_notifier_invalidate_range_start(mm, start, end);
1891 	pgd = pgd_offset(mm, addr);
1892 	do {
1893 		next = pgd_addr_end(addr, end);
1894 		err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1895 		if (err)
1896 			break;
1897 	} while (pgd++, addr = next, addr != end);
1898 	mmu_notifier_invalidate_range_end(mm, start, end);
1899 	return err;
1900 }
1901 EXPORT_SYMBOL_GPL(apply_to_page_range);
1902 
1903 /*
1904  * handle_pte_fault chooses page fault handler according to an entry
1905  * which was read non-atomically.  Before making any commitment, on
1906  * those architectures or configurations (e.g. i386 with PAE) which
1907  * might give a mix of unmatched parts, do_swap_page and do_file_page
1908  * must check under lock before unmapping the pte and proceeding
1909  * (but do_wp_page is only called after already making such a check;
1910  * and do_anonymous_page and do_no_page can safely check later on).
1911  */
1912 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1913 				pte_t *page_table, pte_t orig_pte)
1914 {
1915 	int same = 1;
1916 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1917 	if (sizeof(pte_t) > sizeof(unsigned long)) {
1918 		spinlock_t *ptl = pte_lockptr(mm, pmd);
1919 		spin_lock(ptl);
1920 		same = pte_same(*page_table, orig_pte);
1921 		spin_unlock(ptl);
1922 	}
1923 #endif
1924 	pte_unmap(page_table);
1925 	return same;
1926 }
1927 
1928 /*
1929  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
1930  * servicing faults for write access.  In the normal case, do always want
1931  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
1932  * that do not have writing enabled, when used by access_process_vm.
1933  */
1934 static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
1935 {
1936 	if (likely(vma->vm_flags & VM_WRITE))
1937 		pte = pte_mkwrite(pte);
1938 	return pte;
1939 }
1940 
1941 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1942 {
1943 	/*
1944 	 * If the source page was a PFN mapping, we don't have
1945 	 * a "struct page" for it. We do a best-effort copy by
1946 	 * just copying from the original user address. If that
1947 	 * fails, we just zero-fill it. Live with it.
1948 	 */
1949 	if (unlikely(!src)) {
1950 		void *kaddr = kmap_atomic(dst, KM_USER0);
1951 		void __user *uaddr = (void __user *)(va & PAGE_MASK);
1952 
1953 		/*
1954 		 * This really shouldn't fail, because the page is there
1955 		 * in the page tables. But it might just be unreadable,
1956 		 * in which case we just give up and fill the result with
1957 		 * zeroes.
1958 		 */
1959 		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
1960 			memset(kaddr, 0, PAGE_SIZE);
1961 		kunmap_atomic(kaddr, KM_USER0);
1962 		flush_dcache_page(dst);
1963 	} else
1964 		copy_user_highpage(dst, src, va, vma);
1965 }
1966 
1967 /*
1968  * This routine handles present pages, when users try to write
1969  * to a shared page. It is done by copying the page to a new address
1970  * and decrementing the shared-page counter for the old page.
1971  *
1972  * Note that this routine assumes that the protection checks have been
1973  * done by the caller (the low-level page fault routine in most cases).
1974  * Thus we can safely just mark it writable once we've done any necessary
1975  * COW.
1976  *
1977  * We also mark the page dirty at this point even though the page will
1978  * change only once the write actually happens. This avoids a few races,
1979  * and potentially makes it more efficient.
1980  *
1981  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1982  * but allow concurrent faults), with pte both mapped and locked.
1983  * We return with mmap_sem still held, but pte unmapped and unlocked.
1984  */
1985 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1986 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1987 		spinlock_t *ptl, pte_t orig_pte)
1988 {
1989 	struct page *old_page, *new_page;
1990 	pte_t entry;
1991 	int reuse = 0, ret = 0;
1992 	int page_mkwrite = 0;
1993 	struct page *dirty_page = NULL;
1994 
1995 	old_page = vm_normal_page(vma, address, orig_pte);
1996 	if (!old_page) {
1997 		/*
1998 		 * VM_MIXEDMAP !pfn_valid() case
1999 		 *
2000 		 * We should not cow pages in a shared writeable mapping.
2001 		 * Just mark the pages writable as we can't do any dirty
2002 		 * accounting on raw pfn maps.
2003 		 */
2004 		if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2005 				     (VM_WRITE|VM_SHARED))
2006 			goto reuse;
2007 		goto gotten;
2008 	}
2009 
2010 	/*
2011 	 * Take out anonymous pages first, anonymous shared vmas are
2012 	 * not dirty accountable.
2013 	 */
2014 	if (PageAnon(old_page) && !PageKsm(old_page)) {
2015 		if (!trylock_page(old_page)) {
2016 			page_cache_get(old_page);
2017 			pte_unmap_unlock(page_table, ptl);
2018 			lock_page(old_page);
2019 			page_table = pte_offset_map_lock(mm, pmd, address,
2020 							 &ptl);
2021 			if (!pte_same(*page_table, orig_pte)) {
2022 				unlock_page(old_page);
2023 				page_cache_release(old_page);
2024 				goto unlock;
2025 			}
2026 			page_cache_release(old_page);
2027 		}
2028 		reuse = reuse_swap_page(old_page);
2029 		unlock_page(old_page);
2030 	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2031 					(VM_WRITE|VM_SHARED))) {
2032 		/*
2033 		 * Only catch write-faults on shared writable pages,
2034 		 * read-only shared pages can get COWed by
2035 		 * get_user_pages(.write=1, .force=1).
2036 		 */
2037 		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2038 			struct vm_fault vmf;
2039 			int tmp;
2040 
2041 			vmf.virtual_address = (void __user *)(address &
2042 								PAGE_MASK);
2043 			vmf.pgoff = old_page->index;
2044 			vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2045 			vmf.page = old_page;
2046 
2047 			/*
2048 			 * Notify the address space that the page is about to
2049 			 * become writable so that it can prohibit this or wait
2050 			 * for the page to get into an appropriate state.
2051 			 *
2052 			 * We do this without the lock held, so that it can
2053 			 * sleep if it needs to.
2054 			 */
2055 			page_cache_get(old_page);
2056 			pte_unmap_unlock(page_table, ptl);
2057 
2058 			tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2059 			if (unlikely(tmp &
2060 					(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2061 				ret = tmp;
2062 				goto unwritable_page;
2063 			}
2064 			if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2065 				lock_page(old_page);
2066 				if (!old_page->mapping) {
2067 					ret = 0; /* retry the fault */
2068 					unlock_page(old_page);
2069 					goto unwritable_page;
2070 				}
2071 			} else
2072 				VM_BUG_ON(!PageLocked(old_page));
2073 
2074 			/*
2075 			 * Since we dropped the lock we need to revalidate
2076 			 * the PTE as someone else may have changed it.  If
2077 			 * they did, we just return, as we can count on the
2078 			 * MMU to tell us if they didn't also make it writable.
2079 			 */
2080 			page_table = pte_offset_map_lock(mm, pmd, address,
2081 							 &ptl);
2082 			if (!pte_same(*page_table, orig_pte)) {
2083 				unlock_page(old_page);
2084 				page_cache_release(old_page);
2085 				goto unlock;
2086 			}
2087 
2088 			page_mkwrite = 1;
2089 		}
2090 		dirty_page = old_page;
2091 		get_page(dirty_page);
2092 		reuse = 1;
2093 	}
2094 
2095 	if (reuse) {
2096 reuse:
2097 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2098 		entry = pte_mkyoung(orig_pte);
2099 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2100 		if (ptep_set_access_flags(vma, address, page_table, entry,1))
2101 			update_mmu_cache(vma, address, entry);
2102 		ret |= VM_FAULT_WRITE;
2103 		goto unlock;
2104 	}
2105 
2106 	/*
2107 	 * Ok, we need to copy. Oh, well..
2108 	 */
2109 	page_cache_get(old_page);
2110 gotten:
2111 	pte_unmap_unlock(page_table, ptl);
2112 
2113 	if (unlikely(anon_vma_prepare(vma)))
2114 		goto oom;
2115 
2116 	if (is_zero_pfn(pte_pfn(orig_pte))) {
2117 		new_page = alloc_zeroed_user_highpage_movable(vma, address);
2118 		if (!new_page)
2119 			goto oom;
2120 	} else {
2121 		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2122 		if (!new_page)
2123 			goto oom;
2124 		cow_user_page(new_page, old_page, address, vma);
2125 	}
2126 	__SetPageUptodate(new_page);
2127 
2128 	/*
2129 	 * Don't let another task, with possibly unlocked vma,
2130 	 * keep the mlocked page.
2131 	 */
2132 	if ((vma->vm_flags & VM_LOCKED) && old_page) {
2133 		lock_page(old_page);	/* for LRU manipulation */
2134 		clear_page_mlock(old_page);
2135 		unlock_page(old_page);
2136 	}
2137 
2138 	if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
2139 		goto oom_free_new;
2140 
2141 	/*
2142 	 * Re-check the pte - we dropped the lock
2143 	 */
2144 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2145 	if (likely(pte_same(*page_table, orig_pte))) {
2146 		if (old_page) {
2147 			if (!PageAnon(old_page)) {
2148 				dec_mm_counter(mm, file_rss);
2149 				inc_mm_counter(mm, anon_rss);
2150 			}
2151 		} else
2152 			inc_mm_counter(mm, anon_rss);
2153 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2154 		entry = mk_pte(new_page, vma->vm_page_prot);
2155 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2156 		/*
2157 		 * Clear the pte entry and flush it first, before updating the
2158 		 * pte with the new entry. This will avoid a race condition
2159 		 * seen in the presence of one thread doing SMC and another
2160 		 * thread doing COW.
2161 		 */
2162 		ptep_clear_flush(vma, address, page_table);
2163 		page_add_new_anon_rmap(new_page, vma, address);
2164 		/*
2165 		 * We call the notify macro here because, when using secondary
2166 		 * mmu page tables (such as kvm shadow page tables), we want the
2167 		 * new page to be mapped directly into the secondary page table.
2168 		 */
2169 		set_pte_at_notify(mm, address, page_table, entry);
2170 		update_mmu_cache(vma, address, entry);
2171 		if (old_page) {
2172 			/*
2173 			 * Only after switching the pte to the new page may
2174 			 * we remove the mapcount here. Otherwise another
2175 			 * process may come and find the rmap count decremented
2176 			 * before the pte is switched to the new page, and
2177 			 * "reuse" the old page writing into it while our pte
2178 			 * here still points into it and can be read by other
2179 			 * threads.
2180 			 *
2181 			 * The critical issue is to order this
2182 			 * page_remove_rmap with the ptp_clear_flush above.
2183 			 * Those stores are ordered by (if nothing else,)
2184 			 * the barrier present in the atomic_add_negative
2185 			 * in page_remove_rmap.
2186 			 *
2187 			 * Then the TLB flush in ptep_clear_flush ensures that
2188 			 * no process can access the old page before the
2189 			 * decremented mapcount is visible. And the old page
2190 			 * cannot be reused until after the decremented
2191 			 * mapcount is visible. So transitively, TLBs to
2192 			 * old page will be flushed before it can be reused.
2193 			 */
2194 			page_remove_rmap(old_page);
2195 		}
2196 
2197 		/* Free the old page.. */
2198 		new_page = old_page;
2199 		ret |= VM_FAULT_WRITE;
2200 	} else
2201 		mem_cgroup_uncharge_page(new_page);
2202 
2203 	if (new_page)
2204 		page_cache_release(new_page);
2205 	if (old_page)
2206 		page_cache_release(old_page);
2207 unlock:
2208 	pte_unmap_unlock(page_table, ptl);
2209 	if (dirty_page) {
2210 		/*
2211 		 * Yes, Virginia, this is actually required to prevent a race
2212 		 * with clear_page_dirty_for_io() from clearing the page dirty
2213 		 * bit after it clear all dirty ptes, but before a racing
2214 		 * do_wp_page installs a dirty pte.
2215 		 *
2216 		 * do_no_page is protected similarly.
2217 		 */
2218 		if (!page_mkwrite) {
2219 			wait_on_page_locked(dirty_page);
2220 			set_page_dirty_balance(dirty_page, page_mkwrite);
2221 		}
2222 		put_page(dirty_page);
2223 		if (page_mkwrite) {
2224 			struct address_space *mapping = dirty_page->mapping;
2225 
2226 			set_page_dirty(dirty_page);
2227 			unlock_page(dirty_page);
2228 			page_cache_release(dirty_page);
2229 			if (mapping)	{
2230 				/*
2231 				 * Some device drivers do not set page.mapping
2232 				 * but still dirty their pages
2233 				 */
2234 				balance_dirty_pages_ratelimited(mapping);
2235 			}
2236 		}
2237 
2238 		/* file_update_time outside page_lock */
2239 		if (vma->vm_file)
2240 			file_update_time(vma->vm_file);
2241 	}
2242 	return ret;
2243 oom_free_new:
2244 	page_cache_release(new_page);
2245 oom:
2246 	if (old_page) {
2247 		if (page_mkwrite) {
2248 			unlock_page(old_page);
2249 			page_cache_release(old_page);
2250 		}
2251 		page_cache_release(old_page);
2252 	}
2253 	return VM_FAULT_OOM;
2254 
2255 unwritable_page:
2256 	page_cache_release(old_page);
2257 	return ret;
2258 }
2259 
2260 /*
2261  * Helper functions for unmap_mapping_range().
2262  *
2263  * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
2264  *
2265  * We have to restart searching the prio_tree whenever we drop the lock,
2266  * since the iterator is only valid while the lock is held, and anyway
2267  * a later vma might be split and reinserted earlier while lock dropped.
2268  *
2269  * The list of nonlinear vmas could be handled more efficiently, using
2270  * a placeholder, but handle it in the same way until a need is shown.
2271  * It is important to search the prio_tree before nonlinear list: a vma
2272  * may become nonlinear and be shifted from prio_tree to nonlinear list
2273  * while the lock is dropped; but never shifted from list to prio_tree.
2274  *
2275  * In order to make forward progress despite restarting the search,
2276  * vm_truncate_count is used to mark a vma as now dealt with, so we can
2277  * quickly skip it next time around.  Since the prio_tree search only
2278  * shows us those vmas affected by unmapping the range in question, we
2279  * can't efficiently keep all vmas in step with mapping->truncate_count:
2280  * so instead reset them all whenever it wraps back to 0 (then go to 1).
2281  * mapping->truncate_count and vma->vm_truncate_count are protected by
2282  * i_mmap_lock.
2283  *
2284  * In order to make forward progress despite repeatedly restarting some
2285  * large vma, note the restart_addr from unmap_vmas when it breaks out:
2286  * and restart from that address when we reach that vma again.  It might
2287  * have been split or merged, shrunk or extended, but never shifted: so
2288  * restart_addr remains valid so long as it remains in the vma's range.
2289  * unmap_mapping_range forces truncate_count to leap over page-aligned
2290  * values so we can save vma's restart_addr in its truncate_count field.
2291  */
2292 #define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
2293 
2294 static void reset_vma_truncate_counts(struct address_space *mapping)
2295 {
2296 	struct vm_area_struct *vma;
2297 	struct prio_tree_iter iter;
2298 
2299 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
2300 		vma->vm_truncate_count = 0;
2301 	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
2302 		vma->vm_truncate_count = 0;
2303 }
2304 
2305 static int unmap_mapping_range_vma(struct vm_area_struct *vma,
2306 		unsigned long start_addr, unsigned long end_addr,
2307 		struct zap_details *details)
2308 {
2309 	unsigned long restart_addr;
2310 	int need_break;
2311 
2312 	/*
2313 	 * files that support invalidating or truncating portions of the
2314 	 * file from under mmaped areas must have their ->fault function
2315 	 * return a locked page (and set VM_FAULT_LOCKED in the return).
2316 	 * This provides synchronisation against concurrent unmapping here.
2317 	 */
2318 
2319 again:
2320 	restart_addr = vma->vm_truncate_count;
2321 	if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
2322 		start_addr = restart_addr;
2323 		if (start_addr >= end_addr) {
2324 			/* Top of vma has been split off since last time */
2325 			vma->vm_truncate_count = details->truncate_count;
2326 			return 0;
2327 		}
2328 	}
2329 
2330 	restart_addr = zap_page_range(vma, start_addr,
2331 					end_addr - start_addr, details);
2332 	need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
2333 
2334 	if (restart_addr >= end_addr) {
2335 		/* We have now completed this vma: mark it so */
2336 		vma->vm_truncate_count = details->truncate_count;
2337 		if (!need_break)
2338 			return 0;
2339 	} else {
2340 		/* Note restart_addr in vma's truncate_count field */
2341 		vma->vm_truncate_count = restart_addr;
2342 		if (!need_break)
2343 			goto again;
2344 	}
2345 
2346 	spin_unlock(details->i_mmap_lock);
2347 	cond_resched();
2348 	spin_lock(details->i_mmap_lock);
2349 	return -EINTR;
2350 }
2351 
2352 static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
2353 					    struct zap_details *details)
2354 {
2355 	struct vm_area_struct *vma;
2356 	struct prio_tree_iter iter;
2357 	pgoff_t vba, vea, zba, zea;
2358 
2359 restart:
2360 	vma_prio_tree_foreach(vma, &iter, root,
2361 			details->first_index, details->last_index) {
2362 		/* Skip quickly over those we have already dealt with */
2363 		if (vma->vm_truncate_count == details->truncate_count)
2364 			continue;
2365 
2366 		vba = vma->vm_pgoff;
2367 		vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2368 		/* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2369 		zba = details->first_index;
2370 		if (zba < vba)
2371 			zba = vba;
2372 		zea = details->last_index;
2373 		if (zea > vea)
2374 			zea = vea;
2375 
2376 		if (unmap_mapping_range_vma(vma,
2377 			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2378 			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2379 				details) < 0)
2380 			goto restart;
2381 	}
2382 }
2383 
2384 static inline void unmap_mapping_range_list(struct list_head *head,
2385 					    struct zap_details *details)
2386 {
2387 	struct vm_area_struct *vma;
2388 
2389 	/*
2390 	 * In nonlinear VMAs there is no correspondence between virtual address
2391 	 * offset and file offset.  So we must perform an exhaustive search
2392 	 * across *all* the pages in each nonlinear VMA, not just the pages
2393 	 * whose virtual address lies outside the file truncation point.
2394 	 */
2395 restart:
2396 	list_for_each_entry(vma, head, shared.vm_set.list) {
2397 		/* Skip quickly over those we have already dealt with */
2398 		if (vma->vm_truncate_count == details->truncate_count)
2399 			continue;
2400 		details->nonlinear_vma = vma;
2401 		if (unmap_mapping_range_vma(vma, vma->vm_start,
2402 					vma->vm_end, details) < 0)
2403 			goto restart;
2404 	}
2405 }
2406 
2407 /**
2408  * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2409  * @mapping: the address space containing mmaps to be unmapped.
2410  * @holebegin: byte in first page to unmap, relative to the start of
2411  * the underlying file.  This will be rounded down to a PAGE_SIZE
2412  * boundary.  Note that this is different from truncate_pagecache(), which
2413  * must keep the partial page.  In contrast, we must get rid of
2414  * partial pages.
2415  * @holelen: size of prospective hole in bytes.  This will be rounded
2416  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2417  * end of the file.
2418  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2419  * but 0 when invalidating pagecache, don't throw away private data.
2420  */
2421 void unmap_mapping_range(struct address_space *mapping,
2422 		loff_t const holebegin, loff_t const holelen, int even_cows)
2423 {
2424 	struct zap_details details;
2425 	pgoff_t hba = holebegin >> PAGE_SHIFT;
2426 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2427 
2428 	/* Check for overflow. */
2429 	if (sizeof(holelen) > sizeof(hlen)) {
2430 		long long holeend =
2431 			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2432 		if (holeend & ~(long long)ULONG_MAX)
2433 			hlen = ULONG_MAX - hba + 1;
2434 	}
2435 
2436 	details.check_mapping = even_cows? NULL: mapping;
2437 	details.nonlinear_vma = NULL;
2438 	details.first_index = hba;
2439 	details.last_index = hba + hlen - 1;
2440 	if (details.last_index < details.first_index)
2441 		details.last_index = ULONG_MAX;
2442 	details.i_mmap_lock = &mapping->i_mmap_lock;
2443 
2444 	spin_lock(&mapping->i_mmap_lock);
2445 
2446 	/* Protect against endless unmapping loops */
2447 	mapping->truncate_count++;
2448 	if (unlikely(is_restart_addr(mapping->truncate_count))) {
2449 		if (mapping->truncate_count == 0)
2450 			reset_vma_truncate_counts(mapping);
2451 		mapping->truncate_count++;
2452 	}
2453 	details.truncate_count = mapping->truncate_count;
2454 
2455 	if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
2456 		unmap_mapping_range_tree(&mapping->i_mmap, &details);
2457 	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2458 		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2459 	spin_unlock(&mapping->i_mmap_lock);
2460 }
2461 EXPORT_SYMBOL(unmap_mapping_range);
2462 
2463 int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
2464 {
2465 	struct address_space *mapping = inode->i_mapping;
2466 
2467 	/*
2468 	 * If the underlying filesystem is not going to provide
2469 	 * a way to truncate a range of blocks (punch a hole) -
2470 	 * we should return failure right now.
2471 	 */
2472 	if (!inode->i_op->truncate_range)
2473 		return -ENOSYS;
2474 
2475 	mutex_lock(&inode->i_mutex);
2476 	down_write(&inode->i_alloc_sem);
2477 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2478 	truncate_inode_pages_range(mapping, offset, end);
2479 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2480 	inode->i_op->truncate_range(inode, offset, end);
2481 	up_write(&inode->i_alloc_sem);
2482 	mutex_unlock(&inode->i_mutex);
2483 
2484 	return 0;
2485 }
2486 
2487 /*
2488  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2489  * but allow concurrent faults), and pte mapped but not yet locked.
2490  * We return with mmap_sem still held, but pte unmapped and unlocked.
2491  */
2492 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2493 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2494 		unsigned int flags, pte_t orig_pte)
2495 {
2496 	spinlock_t *ptl;
2497 	struct page *page;
2498 	swp_entry_t entry;
2499 	pte_t pte;
2500 	struct mem_cgroup *ptr = NULL;
2501 	int ret = 0;
2502 
2503 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2504 		goto out;
2505 
2506 	entry = pte_to_swp_entry(orig_pte);
2507 	if (unlikely(non_swap_entry(entry))) {
2508 		if (is_migration_entry(entry)) {
2509 			migration_entry_wait(mm, pmd, address);
2510 		} else if (is_hwpoison_entry(entry)) {
2511 			ret = VM_FAULT_HWPOISON;
2512 		} else {
2513 			print_bad_pte(vma, address, orig_pte, NULL);
2514 			ret = VM_FAULT_OOM;
2515 		}
2516 		goto out;
2517 	}
2518 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2519 	page = lookup_swap_cache(entry);
2520 	if (!page) {
2521 		grab_swap_token(mm); /* Contend for token _before_ read-in */
2522 		page = swapin_readahead(entry,
2523 					GFP_HIGHUSER_MOVABLE, vma, address);
2524 		if (!page) {
2525 			/*
2526 			 * Back out if somebody else faulted in this pte
2527 			 * while we released the pte lock.
2528 			 */
2529 			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2530 			if (likely(pte_same(*page_table, orig_pte)))
2531 				ret = VM_FAULT_OOM;
2532 			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2533 			goto unlock;
2534 		}
2535 
2536 		/* Had to read the page from swap area: Major fault */
2537 		ret = VM_FAULT_MAJOR;
2538 		count_vm_event(PGMAJFAULT);
2539 	} else if (PageHWPoison(page)) {
2540 		ret = VM_FAULT_HWPOISON;
2541 		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2542 		goto out;
2543 	}
2544 
2545 	lock_page(page);
2546 	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2547 
2548 	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
2549 		ret = VM_FAULT_OOM;
2550 		goto out_page;
2551 	}
2552 
2553 	/*
2554 	 * Back out if somebody else already faulted in this pte.
2555 	 */
2556 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2557 	if (unlikely(!pte_same(*page_table, orig_pte)))
2558 		goto out_nomap;
2559 
2560 	if (unlikely(!PageUptodate(page))) {
2561 		ret = VM_FAULT_SIGBUS;
2562 		goto out_nomap;
2563 	}
2564 
2565 	/*
2566 	 * The page isn't present yet, go ahead with the fault.
2567 	 *
2568 	 * Be careful about the sequence of operations here.
2569 	 * To get its accounting right, reuse_swap_page() must be called
2570 	 * while the page is counted on swap but not yet in mapcount i.e.
2571 	 * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2572 	 * must be called after the swap_free(), or it will never succeed.
2573 	 * Because delete_from_swap_page() may be called by reuse_swap_page(),
2574 	 * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
2575 	 * in page->private. In this case, a record in swap_cgroup  is silently
2576 	 * discarded at swap_free().
2577 	 */
2578 
2579 	inc_mm_counter(mm, anon_rss);
2580 	pte = mk_pte(page, vma->vm_page_prot);
2581 	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
2582 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2583 		flags &= ~FAULT_FLAG_WRITE;
2584 	}
2585 	flush_icache_page(vma, page);
2586 	set_pte_at(mm, address, page_table, pte);
2587 	page_add_anon_rmap(page, vma, address);
2588 	/* It's better to call commit-charge after rmap is established */
2589 	mem_cgroup_commit_charge_swapin(page, ptr);
2590 
2591 	swap_free(entry);
2592 	if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2593 		try_to_free_swap(page);
2594 	unlock_page(page);
2595 
2596 	if (flags & FAULT_FLAG_WRITE) {
2597 		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2598 		if (ret & VM_FAULT_ERROR)
2599 			ret &= VM_FAULT_ERROR;
2600 		goto out;
2601 	}
2602 
2603 	/* No need to invalidate - it was non-present before */
2604 	update_mmu_cache(vma, address, pte);
2605 unlock:
2606 	pte_unmap_unlock(page_table, ptl);
2607 out:
2608 	return ret;
2609 out_nomap:
2610 	mem_cgroup_cancel_charge_swapin(ptr);
2611 	pte_unmap_unlock(page_table, ptl);
2612 out_page:
2613 	unlock_page(page);
2614 	page_cache_release(page);
2615 	return ret;
2616 }
2617 
2618 /*
2619  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2620  * but allow concurrent faults), and pte mapped but not yet locked.
2621  * We return with mmap_sem still held, but pte unmapped and unlocked.
2622  */
2623 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2624 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2625 		unsigned int flags)
2626 {
2627 	struct page *page;
2628 	spinlock_t *ptl;
2629 	pte_t entry;
2630 
2631 	if (!(flags & FAULT_FLAG_WRITE)) {
2632 		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2633 						vma->vm_page_prot));
2634 		ptl = pte_lockptr(mm, pmd);
2635 		spin_lock(ptl);
2636 		if (!pte_none(*page_table))
2637 			goto unlock;
2638 		goto setpte;
2639 	}
2640 
2641 	/* Allocate our own private page. */
2642 	pte_unmap(page_table);
2643 
2644 	if (unlikely(anon_vma_prepare(vma)))
2645 		goto oom;
2646 	page = alloc_zeroed_user_highpage_movable(vma, address);
2647 	if (!page)
2648 		goto oom;
2649 	__SetPageUptodate(page);
2650 
2651 	if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
2652 		goto oom_free_page;
2653 
2654 	entry = mk_pte(page, vma->vm_page_prot);
2655 	if (vma->vm_flags & VM_WRITE)
2656 		entry = pte_mkwrite(pte_mkdirty(entry));
2657 
2658 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2659 	if (!pte_none(*page_table))
2660 		goto release;
2661 
2662 	inc_mm_counter(mm, anon_rss);
2663 	page_add_new_anon_rmap(page, vma, address);
2664 setpte:
2665 	set_pte_at(mm, address, page_table, entry);
2666 
2667 	/* No need to invalidate - it was non-present before */
2668 	update_mmu_cache(vma, address, entry);
2669 unlock:
2670 	pte_unmap_unlock(page_table, ptl);
2671 	return 0;
2672 release:
2673 	mem_cgroup_uncharge_page(page);
2674 	page_cache_release(page);
2675 	goto unlock;
2676 oom_free_page:
2677 	page_cache_release(page);
2678 oom:
2679 	return VM_FAULT_OOM;
2680 }
2681 
2682 /*
2683  * __do_fault() tries to create a new page mapping. It aggressively
2684  * tries to share with existing pages, but makes a separate copy if
2685  * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
2686  * the next page fault.
2687  *
2688  * As this is called only for pages that do not currently exist, we
2689  * do not need to flush old virtual caches or the TLB.
2690  *
2691  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2692  * but allow concurrent faults), and pte neither mapped nor locked.
2693  * We return with mmap_sem still held, but pte unmapped and unlocked.
2694  */
2695 static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2696 		unsigned long address, pmd_t *pmd,
2697 		pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2698 {
2699 	pte_t *page_table;
2700 	spinlock_t *ptl;
2701 	struct page *page;
2702 	pte_t entry;
2703 	int anon = 0;
2704 	int charged = 0;
2705 	struct page *dirty_page = NULL;
2706 	struct vm_fault vmf;
2707 	int ret;
2708 	int page_mkwrite = 0;
2709 
2710 	vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2711 	vmf.pgoff = pgoff;
2712 	vmf.flags = flags;
2713 	vmf.page = NULL;
2714 
2715 	ret = vma->vm_ops->fault(vma, &vmf);
2716 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2717 		return ret;
2718 
2719 	if (unlikely(PageHWPoison(vmf.page))) {
2720 		if (ret & VM_FAULT_LOCKED)
2721 			unlock_page(vmf.page);
2722 		return VM_FAULT_HWPOISON;
2723 	}
2724 
2725 	/*
2726 	 * For consistency in subsequent calls, make the faulted page always
2727 	 * locked.
2728 	 */
2729 	if (unlikely(!(ret & VM_FAULT_LOCKED)))
2730 		lock_page(vmf.page);
2731 	else
2732 		VM_BUG_ON(!PageLocked(vmf.page));
2733 
2734 	/*
2735 	 * Should we do an early C-O-W break?
2736 	 */
2737 	page = vmf.page;
2738 	if (flags & FAULT_FLAG_WRITE) {
2739 		if (!(vma->vm_flags & VM_SHARED)) {
2740 			anon = 1;
2741 			if (unlikely(anon_vma_prepare(vma))) {
2742 				ret = VM_FAULT_OOM;
2743 				goto out;
2744 			}
2745 			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
2746 						vma, address);
2747 			if (!page) {
2748 				ret = VM_FAULT_OOM;
2749 				goto out;
2750 			}
2751 			if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
2752 				ret = VM_FAULT_OOM;
2753 				page_cache_release(page);
2754 				goto out;
2755 			}
2756 			charged = 1;
2757 			/*
2758 			 * Don't let another task, with possibly unlocked vma,
2759 			 * keep the mlocked page.
2760 			 */
2761 			if (vma->vm_flags & VM_LOCKED)
2762 				clear_page_mlock(vmf.page);
2763 			copy_user_highpage(page, vmf.page, address, vma);
2764 			__SetPageUptodate(page);
2765 		} else {
2766 			/*
2767 			 * If the page will be shareable, see if the backing
2768 			 * address space wants to know that the page is about
2769 			 * to become writable
2770 			 */
2771 			if (vma->vm_ops->page_mkwrite) {
2772 				int tmp;
2773 
2774 				unlock_page(page);
2775 				vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2776 				tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2777 				if (unlikely(tmp &
2778 					  (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2779 					ret = tmp;
2780 					goto unwritable_page;
2781 				}
2782 				if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2783 					lock_page(page);
2784 					if (!page->mapping) {
2785 						ret = 0; /* retry the fault */
2786 						unlock_page(page);
2787 						goto unwritable_page;
2788 					}
2789 				} else
2790 					VM_BUG_ON(!PageLocked(page));
2791 				page_mkwrite = 1;
2792 			}
2793 		}
2794 
2795 	}
2796 
2797 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2798 
2799 	/*
2800 	 * This silly early PAGE_DIRTY setting removes a race
2801 	 * due to the bad i386 page protection. But it's valid
2802 	 * for other architectures too.
2803 	 *
2804 	 * Note that if FAULT_FLAG_WRITE is set, we either now have
2805 	 * an exclusive copy of the page, or this is a shared mapping,
2806 	 * so we can make it writable and dirty to avoid having to
2807 	 * handle that later.
2808 	 */
2809 	/* Only go through if we didn't race with anybody else... */
2810 	if (likely(pte_same(*page_table, orig_pte))) {
2811 		flush_icache_page(vma, page);
2812 		entry = mk_pte(page, vma->vm_page_prot);
2813 		if (flags & FAULT_FLAG_WRITE)
2814 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2815 		if (anon) {
2816 			inc_mm_counter(mm, anon_rss);
2817 			page_add_new_anon_rmap(page, vma, address);
2818 		} else {
2819 			inc_mm_counter(mm, file_rss);
2820 			page_add_file_rmap(page);
2821 			if (flags & FAULT_FLAG_WRITE) {
2822 				dirty_page = page;
2823 				get_page(dirty_page);
2824 			}
2825 		}
2826 		set_pte_at(mm, address, page_table, entry);
2827 
2828 		/* no need to invalidate: a not-present page won't be cached */
2829 		update_mmu_cache(vma, address, entry);
2830 	} else {
2831 		if (charged)
2832 			mem_cgroup_uncharge_page(page);
2833 		if (anon)
2834 			page_cache_release(page);
2835 		else
2836 			anon = 1; /* no anon but release faulted_page */
2837 	}
2838 
2839 	pte_unmap_unlock(page_table, ptl);
2840 
2841 out:
2842 	if (dirty_page) {
2843 		struct address_space *mapping = page->mapping;
2844 
2845 		if (set_page_dirty(dirty_page))
2846 			page_mkwrite = 1;
2847 		unlock_page(dirty_page);
2848 		put_page(dirty_page);
2849 		if (page_mkwrite && mapping) {
2850 			/*
2851 			 * Some device drivers do not set page.mapping but still
2852 			 * dirty their pages
2853 			 */
2854 			balance_dirty_pages_ratelimited(mapping);
2855 		}
2856 
2857 		/* file_update_time outside page_lock */
2858 		if (vma->vm_file)
2859 			file_update_time(vma->vm_file);
2860 	} else {
2861 		unlock_page(vmf.page);
2862 		if (anon)
2863 			page_cache_release(vmf.page);
2864 	}
2865 
2866 	return ret;
2867 
2868 unwritable_page:
2869 	page_cache_release(page);
2870 	return ret;
2871 }
2872 
2873 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2874 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2875 		unsigned int flags, pte_t orig_pte)
2876 {
2877 	pgoff_t pgoff = (((address & PAGE_MASK)
2878 			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2879 
2880 	pte_unmap(page_table);
2881 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2882 }
2883 
2884 /*
2885  * Fault of a previously existing named mapping. Repopulate the pte
2886  * from the encoded file_pte if possible. This enables swappable
2887  * nonlinear vmas.
2888  *
2889  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2890  * but allow concurrent faults), and pte mapped but not yet locked.
2891  * We return with mmap_sem still held, but pte unmapped and unlocked.
2892  */
2893 static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2894 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2895 		unsigned int flags, pte_t orig_pte)
2896 {
2897 	pgoff_t pgoff;
2898 
2899 	flags |= FAULT_FLAG_NONLINEAR;
2900 
2901 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2902 		return 0;
2903 
2904 	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
2905 		/*
2906 		 * Page table corrupted: show pte and kill process.
2907 		 */
2908 		print_bad_pte(vma, address, orig_pte, NULL);
2909 		return VM_FAULT_OOM;
2910 	}
2911 
2912 	pgoff = pte_to_pgoff(orig_pte);
2913 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2914 }
2915 
2916 /*
2917  * These routines also need to handle stuff like marking pages dirty
2918  * and/or accessed for architectures that don't do it in hardware (most
2919  * RISC architectures).  The early dirtying is also good on the i386.
2920  *
2921  * There is also a hook called "update_mmu_cache()" that architectures
2922  * with external mmu caches can use to update those (ie the Sparc or
2923  * PowerPC hashed page tables that act as extended TLBs).
2924  *
2925  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2926  * but allow concurrent faults), and pte mapped but not yet locked.
2927  * We return with mmap_sem still held, but pte unmapped and unlocked.
2928  */
2929 static inline int handle_pte_fault(struct mm_struct *mm,
2930 		struct vm_area_struct *vma, unsigned long address,
2931 		pte_t *pte, pmd_t *pmd, unsigned int flags)
2932 {
2933 	pte_t entry;
2934 	spinlock_t *ptl;
2935 
2936 	entry = *pte;
2937 	if (!pte_present(entry)) {
2938 		if (pte_none(entry)) {
2939 			if (vma->vm_ops) {
2940 				if (likely(vma->vm_ops->fault))
2941 					return do_linear_fault(mm, vma, address,
2942 						pte, pmd, flags, entry);
2943 			}
2944 			return do_anonymous_page(mm, vma, address,
2945 						 pte, pmd, flags);
2946 		}
2947 		if (pte_file(entry))
2948 			return do_nonlinear_fault(mm, vma, address,
2949 					pte, pmd, flags, entry);
2950 		return do_swap_page(mm, vma, address,
2951 					pte, pmd, flags, entry);
2952 	}
2953 
2954 	ptl = pte_lockptr(mm, pmd);
2955 	spin_lock(ptl);
2956 	if (unlikely(!pte_same(*pte, entry)))
2957 		goto unlock;
2958 	if (flags & FAULT_FLAG_WRITE) {
2959 		if (!pte_write(entry))
2960 			return do_wp_page(mm, vma, address,
2961 					pte, pmd, ptl, entry);
2962 		entry = pte_mkdirty(entry);
2963 	}
2964 	entry = pte_mkyoung(entry);
2965 	if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
2966 		update_mmu_cache(vma, address, entry);
2967 	} else {
2968 		/*
2969 		 * This is needed only for protection faults but the arch code
2970 		 * is not yet telling us if this is a protection fault or not.
2971 		 * This still avoids useless tlb flushes for .text page faults
2972 		 * with threads.
2973 		 */
2974 		if (flags & FAULT_FLAG_WRITE)
2975 			flush_tlb_page(vma, address);
2976 	}
2977 unlock:
2978 	pte_unmap_unlock(pte, ptl);
2979 	return 0;
2980 }
2981 
2982 /*
2983  * By the time we get here, we already hold the mm semaphore
2984  */
2985 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2986 		unsigned long address, unsigned int flags)
2987 {
2988 	pgd_t *pgd;
2989 	pud_t *pud;
2990 	pmd_t *pmd;
2991 	pte_t *pte;
2992 
2993 	__set_current_state(TASK_RUNNING);
2994 
2995 	count_vm_event(PGFAULT);
2996 
2997 	if (unlikely(is_vm_hugetlb_page(vma)))
2998 		return hugetlb_fault(mm, vma, address, flags);
2999 
3000 	pgd = pgd_offset(mm, address);
3001 	pud = pud_alloc(mm, pgd, address);
3002 	if (!pud)
3003 		return VM_FAULT_OOM;
3004 	pmd = pmd_alloc(mm, pud, address);
3005 	if (!pmd)
3006 		return VM_FAULT_OOM;
3007 	pte = pte_alloc_map(mm, pmd, address);
3008 	if (!pte)
3009 		return VM_FAULT_OOM;
3010 
3011 	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3012 }
3013 
3014 #ifndef __PAGETABLE_PUD_FOLDED
3015 /*
3016  * Allocate page upper directory.
3017  * We've already handled the fast-path in-line.
3018  */
3019 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3020 {
3021 	pud_t *new = pud_alloc_one(mm, address);
3022 	if (!new)
3023 		return -ENOMEM;
3024 
3025 	smp_wmb(); /* See comment in __pte_alloc */
3026 
3027 	spin_lock(&mm->page_table_lock);
3028 	if (pgd_present(*pgd))		/* Another has populated it */
3029 		pud_free(mm, new);
3030 	else
3031 		pgd_populate(mm, pgd, new);
3032 	spin_unlock(&mm->page_table_lock);
3033 	return 0;
3034 }
3035 #endif /* __PAGETABLE_PUD_FOLDED */
3036 
3037 #ifndef __PAGETABLE_PMD_FOLDED
3038 /*
3039  * Allocate page middle directory.
3040  * We've already handled the fast-path in-line.
3041  */
3042 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3043 {
3044 	pmd_t *new = pmd_alloc_one(mm, address);
3045 	if (!new)
3046 		return -ENOMEM;
3047 
3048 	smp_wmb(); /* See comment in __pte_alloc */
3049 
3050 	spin_lock(&mm->page_table_lock);
3051 #ifndef __ARCH_HAS_4LEVEL_HACK
3052 	if (pud_present(*pud))		/* Another has populated it */
3053 		pmd_free(mm, new);
3054 	else
3055 		pud_populate(mm, pud, new);
3056 #else
3057 	if (pgd_present(*pud))		/* Another has populated it */
3058 		pmd_free(mm, new);
3059 	else
3060 		pgd_populate(mm, pud, new);
3061 #endif /* __ARCH_HAS_4LEVEL_HACK */
3062 	spin_unlock(&mm->page_table_lock);
3063 	return 0;
3064 }
3065 #endif /* __PAGETABLE_PMD_FOLDED */
3066 
3067 int make_pages_present(unsigned long addr, unsigned long end)
3068 {
3069 	int ret, len, write;
3070 	struct vm_area_struct * vma;
3071 
3072 	vma = find_vma(current->mm, addr);
3073 	if (!vma)
3074 		return -ENOMEM;
3075 	write = (vma->vm_flags & VM_WRITE) != 0;
3076 	BUG_ON(addr >= end);
3077 	BUG_ON(end > vma->vm_end);
3078 	len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
3079 	ret = get_user_pages(current, current->mm, addr,
3080 			len, write, 0, NULL, NULL);
3081 	if (ret < 0)
3082 		return ret;
3083 	return ret == len ? 0 : -EFAULT;
3084 }
3085 
3086 #if !defined(__HAVE_ARCH_GATE_AREA)
3087 
3088 #if defined(AT_SYSINFO_EHDR)
3089 static struct vm_area_struct gate_vma;
3090 
3091 static int __init gate_vma_init(void)
3092 {
3093 	gate_vma.vm_mm = NULL;
3094 	gate_vma.vm_start = FIXADDR_USER_START;
3095 	gate_vma.vm_end = FIXADDR_USER_END;
3096 	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
3097 	gate_vma.vm_page_prot = __P101;
3098 	/*
3099 	 * Make sure the vDSO gets into every core dump.
3100 	 * Dumping its contents makes post-mortem fully interpretable later
3101 	 * without matching up the same kernel and hardware config to see
3102 	 * what PC values meant.
3103 	 */
3104 	gate_vma.vm_flags |= VM_ALWAYSDUMP;
3105 	return 0;
3106 }
3107 __initcall(gate_vma_init);
3108 #endif
3109 
3110 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
3111 {
3112 #ifdef AT_SYSINFO_EHDR
3113 	return &gate_vma;
3114 #else
3115 	return NULL;
3116 #endif
3117 }
3118 
3119 int in_gate_area_no_task(unsigned long addr)
3120 {
3121 #ifdef AT_SYSINFO_EHDR
3122 	if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
3123 		return 1;
3124 #endif
3125 	return 0;
3126 }
3127 
3128 #endif	/* __HAVE_ARCH_GATE_AREA */
3129 
3130 static int follow_pte(struct mm_struct *mm, unsigned long address,
3131 		pte_t **ptepp, spinlock_t **ptlp)
3132 {
3133 	pgd_t *pgd;
3134 	pud_t *pud;
3135 	pmd_t *pmd;
3136 	pte_t *ptep;
3137 
3138 	pgd = pgd_offset(mm, address);
3139 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3140 		goto out;
3141 
3142 	pud = pud_offset(pgd, address);
3143 	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3144 		goto out;
3145 
3146 	pmd = pmd_offset(pud, address);
3147 	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3148 		goto out;
3149 
3150 	/* We cannot handle huge page PFN maps. Luckily they don't exist. */
3151 	if (pmd_huge(*pmd))
3152 		goto out;
3153 
3154 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3155 	if (!ptep)
3156 		goto out;
3157 	if (!pte_present(*ptep))
3158 		goto unlock;
3159 	*ptepp = ptep;
3160 	return 0;
3161 unlock:
3162 	pte_unmap_unlock(ptep, *ptlp);
3163 out:
3164 	return -EINVAL;
3165 }
3166 
3167 /**
3168  * follow_pfn - look up PFN at a user virtual address
3169  * @vma: memory mapping
3170  * @address: user virtual address
3171  * @pfn: location to store found PFN
3172  *
3173  * Only IO mappings and raw PFN mappings are allowed.
3174  *
3175  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3176  */
3177 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3178 	unsigned long *pfn)
3179 {
3180 	int ret = -EINVAL;
3181 	spinlock_t *ptl;
3182 	pte_t *ptep;
3183 
3184 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3185 		return ret;
3186 
3187 	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3188 	if (ret)
3189 		return ret;
3190 	*pfn = pte_pfn(*ptep);
3191 	pte_unmap_unlock(ptep, ptl);
3192 	return 0;
3193 }
3194 EXPORT_SYMBOL(follow_pfn);
3195 
3196 #ifdef CONFIG_HAVE_IOREMAP_PROT
3197 int follow_phys(struct vm_area_struct *vma,
3198 		unsigned long address, unsigned int flags,
3199 		unsigned long *prot, resource_size_t *phys)
3200 {
3201 	int ret = -EINVAL;
3202 	pte_t *ptep, pte;
3203 	spinlock_t *ptl;
3204 
3205 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3206 		goto out;
3207 
3208 	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3209 		goto out;
3210 	pte = *ptep;
3211 
3212 	if ((flags & FOLL_WRITE) && !pte_write(pte))
3213 		goto unlock;
3214 
3215 	*prot = pgprot_val(pte_pgprot(pte));
3216 	*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3217 
3218 	ret = 0;
3219 unlock:
3220 	pte_unmap_unlock(ptep, ptl);
3221 out:
3222 	return ret;
3223 }
3224 
3225 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3226 			void *buf, int len, int write)
3227 {
3228 	resource_size_t phys_addr;
3229 	unsigned long prot = 0;
3230 	void __iomem *maddr;
3231 	int offset = addr & (PAGE_SIZE-1);
3232 
3233 	if (follow_phys(vma, addr, write, &prot, &phys_addr))
3234 		return -EINVAL;
3235 
3236 	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
3237 	if (write)
3238 		memcpy_toio(maddr + offset, buf, len);
3239 	else
3240 		memcpy_fromio(buf, maddr + offset, len);
3241 	iounmap(maddr);
3242 
3243 	return len;
3244 }
3245 #endif
3246 
3247 /*
3248  * Access another process' address space.
3249  * Source/target buffer must be kernel space,
3250  * Do not walk the page table directly, use get_user_pages
3251  */
3252 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
3253 {
3254 	struct mm_struct *mm;
3255 	struct vm_area_struct *vma;
3256 	void *old_buf = buf;
3257 
3258 	mm = get_task_mm(tsk);
3259 	if (!mm)
3260 		return 0;
3261 
3262 	down_read(&mm->mmap_sem);
3263 	/* ignore errors, just check how much was successfully transferred */
3264 	while (len) {
3265 		int bytes, ret, offset;
3266 		void *maddr;
3267 		struct page *page = NULL;
3268 
3269 		ret = get_user_pages(tsk, mm, addr, 1,
3270 				write, 1, &page, &vma);
3271 		if (ret <= 0) {
3272 			/*
3273 			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
3274 			 * we can access using slightly different code.
3275 			 */
3276 #ifdef CONFIG_HAVE_IOREMAP_PROT
3277 			vma = find_vma(mm, addr);
3278 			if (!vma)
3279 				break;
3280 			if (vma->vm_ops && vma->vm_ops->access)
3281 				ret = vma->vm_ops->access(vma, addr, buf,
3282 							  len, write);
3283 			if (ret <= 0)
3284 #endif
3285 				break;
3286 			bytes = ret;
3287 		} else {
3288 			bytes = len;
3289 			offset = addr & (PAGE_SIZE-1);
3290 			if (bytes > PAGE_SIZE-offset)
3291 				bytes = PAGE_SIZE-offset;
3292 
3293 			maddr = kmap(page);
3294 			if (write) {
3295 				copy_to_user_page(vma, page, addr,
3296 						  maddr + offset, buf, bytes);
3297 				set_page_dirty_lock(page);
3298 			} else {
3299 				copy_from_user_page(vma, page, addr,
3300 						    buf, maddr + offset, bytes);
3301 			}
3302 			kunmap(page);
3303 			page_cache_release(page);
3304 		}
3305 		len -= bytes;
3306 		buf += bytes;
3307 		addr += bytes;
3308 	}
3309 	up_read(&mm->mmap_sem);
3310 	mmput(mm);
3311 
3312 	return buf - old_buf;
3313 }
3314 
3315 /*
3316  * Print the name of a VMA.
3317  */
3318 void print_vma_addr(char *prefix, unsigned long ip)
3319 {
3320 	struct mm_struct *mm = current->mm;
3321 	struct vm_area_struct *vma;
3322 
3323 	/*
3324 	 * Do not print if we are in atomic
3325 	 * contexts (in exception stacks, etc.):
3326 	 */
3327 	if (preempt_count())
3328 		return;
3329 
3330 	down_read(&mm->mmap_sem);
3331 	vma = find_vma(mm, ip);
3332 	if (vma && vma->vm_file) {
3333 		struct file *f = vma->vm_file;
3334 		char *buf = (char *)__get_free_page(GFP_KERNEL);
3335 		if (buf) {
3336 			char *p, *s;
3337 
3338 			p = d_path(&f->f_path, buf, PAGE_SIZE);
3339 			if (IS_ERR(p))
3340 				p = "?";
3341 			s = strrchr(p, '/');
3342 			if (s)
3343 				p = s+1;
3344 			printk("%s%s[%lx+%lx]", prefix, p,
3345 					vma->vm_start,
3346 					vma->vm_end - vma->vm_start);
3347 			free_page((unsigned long)buf);
3348 		}
3349 	}
3350 	up_read(&current->mm->mmap_sem);
3351 }
3352 
3353 #ifdef CONFIG_PROVE_LOCKING
3354 void might_fault(void)
3355 {
3356 	/*
3357 	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3358 	 * holding the mmap_sem, this is safe because kernel memory doesn't
3359 	 * get paged out, therefore we'll never actually fault, and the
3360 	 * below annotations will generate false positives.
3361 	 */
3362 	if (segment_eq(get_fs(), KERNEL_DS))
3363 		return;
3364 
3365 	might_sleep();
3366 	/*
3367 	 * it would be nicer only to annotate paths which are not under
3368 	 * pagefault_disable, however that requires a larger audit and
3369 	 * providing helpers like get_user_atomic.
3370 	 */
3371 	if (!in_atomic() && current->mm)
3372 		might_lock_read(&current->mm->mmap_sem);
3373 }
3374 EXPORT_SYMBOL(might_fault);
3375 #endif
3376