Root/mm/memory.c

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#include <linux/gfp.h>
60
61#include <asm/io.h>
62#include <asm/pgalloc.h>
63#include <asm/uaccess.h>
64#include <asm/tlb.h>
65#include <asm/tlbflush.h>
66#include <asm/pgtable.h>
67
68#include "internal.h"
69
70#ifndef CONFIG_NEED_MULTIPLE_NODES
71/* use the per-pgdat data instead for discontigmem - mbligh */
72unsigned long max_mapnr;
73struct page *mem_map;
74
75EXPORT_SYMBOL(max_mapnr);
76EXPORT_SYMBOL(mem_map);
77#endif
78
79unsigned long num_physpages;
80/*
81 * A number of key systems in x86 including ioremap() rely on the assumption
82 * that high_memory defines the upper bound on direct map memory, then end
83 * of ZONE_NORMAL. Under CONFIG_DISCONTIG this means that max_low_pfn and
84 * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
85 * and ZONE_HIGHMEM.
86 */
87void * high_memory;
88
89EXPORT_SYMBOL(num_physpages);
90EXPORT_SYMBOL(high_memory);
91
92/*
93 * Randomize the address space (stacks, mmaps, brk, etc.).
94 *
95 * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
96 * as ancient (libc5 based) binaries can segfault. )
97 */
98int randomize_va_space __read_mostly =
99#ifdef CONFIG_COMPAT_BRK
100                    1;
101#else
102                    2;
103#endif
104
105static int __init disable_randmaps(char *s)
106{
107    randomize_va_space = 0;
108    return 1;
109}
110__setup("norandmaps", disable_randmaps);
111
112unsigned long zero_pfn __read_mostly;
113unsigned long highest_memmap_pfn __read_mostly;
114
115/*
116 * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
117 */
118static int __init init_zero_pfn(void)
119{
120    zero_pfn = page_to_pfn(ZERO_PAGE(0));
121    return 0;
122}
123core_initcall(init_zero_pfn);
124
125
126#if defined(SPLIT_RSS_COUNTING)
127
128static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
129{
130    int i;
131
132    for (i = 0; i < NR_MM_COUNTERS; i++) {
133        if (task->rss_stat.count[i]) {
134            add_mm_counter(mm, i, task->rss_stat.count[i]);
135            task->rss_stat.count[i] = 0;
136        }
137    }
138    task->rss_stat.events = 0;
139}
140
141static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
142{
143    struct task_struct *task = current;
144
145    if (likely(task->mm == mm))
146        task->rss_stat.count[member] += val;
147    else
148        add_mm_counter(mm, member, val);
149}
150#define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
151#define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
152
153/* sync counter once per 64 page faults */
154#define TASK_RSS_EVENTS_THRESH (64)
155static void check_sync_rss_stat(struct task_struct *task)
156{
157    if (unlikely(task != current))
158        return;
159    if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
160        __sync_task_rss_stat(task, task->mm);
161}
162
163unsigned long get_mm_counter(struct mm_struct *mm, int member)
164{
165    long val = 0;
166
167    /*
168     * Don't use task->mm here...for avoiding to use task_get_mm()..
169     * The caller must guarantee task->mm is not invalid.
170     */
171    val = atomic_long_read(&mm->rss_stat.count[member]);
172    /*
173     * counter is updated in asynchronous manner and may go to minus.
174     * But it's never be expected number for users.
175     */
176    if (val < 0)
177        return 0;
178    return (unsigned long)val;
179}
180
181void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
182{
183    __sync_task_rss_stat(task, mm);
184}
185#else
186
187#define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
188#define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
189
190static void check_sync_rss_stat(struct task_struct *task)
191{
192}
193
194#endif
195
196/*
197 * If a p?d_bad entry is found while walking page tables, report
198 * the error, before resetting entry to p?d_none. Usually (but
199 * very seldom) called out from the p?d_none_or_clear_bad macros.
200 */
201
202void pgd_clear_bad(pgd_t *pgd)
203{
204    pgd_ERROR(*pgd);
205    pgd_clear(pgd);
206}
207
208void pud_clear_bad(pud_t *pud)
209{
210    pud_ERROR(*pud);
211    pud_clear(pud);
212}
213
214void pmd_clear_bad(pmd_t *pmd)
215{
216    pmd_ERROR(*pmd);
217    pmd_clear(pmd);
218}
219
220/*
221 * Note: this doesn't free the actual pages themselves. That
222 * has been handled earlier when unmapping all the memory regions.
223 */
224static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
225               unsigned long addr)
226{
227    pgtable_t token = pmd_pgtable(*pmd);
228    pmd_clear(pmd);
229    pte_free_tlb(tlb, token, addr);
230    tlb->mm->nr_ptes--;
231}
232
233static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
234                unsigned long addr, unsigned long end,
235                unsigned long floor, unsigned long ceiling)
236{
237    pmd_t *pmd;
238    unsigned long next;
239    unsigned long start;
240
241    start = addr;
242    pmd = pmd_offset(pud, addr);
243    do {
244        next = pmd_addr_end(addr, end);
245        if (pmd_none_or_clear_bad(pmd))
246            continue;
247        free_pte_range(tlb, pmd, addr);
248    } while (pmd++, addr = next, addr != end);
249
250    start &= PUD_MASK;
251    if (start < floor)
252        return;
253    if (ceiling) {
254        ceiling &= PUD_MASK;
255        if (!ceiling)
256            return;
257    }
258    if (end - 1 > ceiling - 1)
259        return;
260
261    pmd = pmd_offset(pud, start);
262    pud_clear(pud);
263    pmd_free_tlb(tlb, pmd, start);
264}
265
266static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
267                unsigned long addr, unsigned long end,
268                unsigned long floor, unsigned long ceiling)
269{
270    pud_t *pud;
271    unsigned long next;
272    unsigned long start;
273
274    start = addr;
275    pud = pud_offset(pgd, addr);
276    do {
277        next = pud_addr_end(addr, end);
278        if (pud_none_or_clear_bad(pud))
279            continue;
280        free_pmd_range(tlb, pud, addr, next, floor, ceiling);
281    } while (pud++, addr = next, addr != end);
282
283    start &= PGDIR_MASK;
284    if (start < floor)
285        return;
286    if (ceiling) {
287        ceiling &= PGDIR_MASK;
288        if (!ceiling)
289            return;
290    }
291    if (end - 1 > ceiling - 1)
292        return;
293
294    pud = pud_offset(pgd, start);
295    pgd_clear(pgd);
296    pud_free_tlb(tlb, pud, start);
297}
298
299/*
300 * This function frees user-level page tables of a process.
301 *
302 * Must be called with pagetable lock held.
303 */
304void free_pgd_range(struct mmu_gather *tlb,
305            unsigned long addr, unsigned long end,
306            unsigned long floor, unsigned long ceiling)
307{
308    pgd_t *pgd;
309    unsigned long next;
310    unsigned long start;
311
312    /*
313     * The next few lines have given us lots of grief...
314     *
315     * Why are we testing PMD* at this top level? Because often
316     * there will be no work to do at all, and we'd prefer not to
317     * go all the way down to the bottom just to discover that.
318     *
319     * Why all these "- 1"s? Because 0 represents both the bottom
320     * of the address space and the top of it (using -1 for the
321     * top wouldn't help much: the masks would do the wrong thing).
322     * The rule is that addr 0 and floor 0 refer to the bottom of
323     * the address space, but end 0 and ceiling 0 refer to the top
324     * Comparisons need to use "end - 1" and "ceiling - 1" (though
325     * that end 0 case should be mythical).
326     *
327     * Wherever addr is brought up or ceiling brought down, we must
328     * be careful to reject "the opposite 0" before it confuses the
329     * subsequent tests. But what about where end is brought down
330     * by PMD_SIZE below? no, end can't go down to 0 there.
331     *
332     * Whereas we round start (addr) and ceiling down, by different
333     * masks at different levels, in order to test whether a table
334     * now has no other vmas using it, so can be freed, we don't
335     * bother to round floor or end up - the tests don't need that.
336     */
337
338    addr &= PMD_MASK;
339    if (addr < floor) {
340        addr += PMD_SIZE;
341        if (!addr)
342            return;
343    }
344    if (ceiling) {
345        ceiling &= PMD_MASK;
346        if (!ceiling)
347            return;
348    }
349    if (end - 1 > ceiling - 1)
350        end -= PMD_SIZE;
351    if (addr > end - 1)
352        return;
353
354    start = addr;
355    pgd = pgd_offset(tlb->mm, addr);
356    do {
357        next = pgd_addr_end(addr, end);
358        if (pgd_none_or_clear_bad(pgd))
359            continue;
360        free_pud_range(tlb, pgd, addr, next, floor, ceiling);
361    } while (pgd++, addr = next, addr != end);
362}
363
364void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
365        unsigned long floor, unsigned long ceiling)
366{
367    while (vma) {
368        struct vm_area_struct *next = vma->vm_next;
369        unsigned long addr = vma->vm_start;
370
371        /*
372         * Hide vma from rmap and truncate_pagecache before freeing
373         * pgtables
374         */
375        unlink_anon_vmas(vma);
376        unlink_file_vma(vma);
377
378        if (is_vm_hugetlb_page(vma)) {
379            hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
380                floor, next? next->vm_start: ceiling);
381        } else {
382            /*
383             * Optimization: gather nearby vmas into one call down
384             */
385            while (next && next->vm_start <= vma->vm_end + PMD_SIZE
386                   && !is_vm_hugetlb_page(next)) {
387                vma = next;
388                next = vma->vm_next;
389                unlink_anon_vmas(vma);
390                unlink_file_vma(vma);
391            }
392            free_pgd_range(tlb, addr, vma->vm_end,
393                floor, next? next->vm_start: ceiling);
394        }
395        vma = next;
396    }
397}
398
399int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
400{
401    pgtable_t new = pte_alloc_one(mm, address);
402    if (!new)
403        return -ENOMEM;
404
405    /*
406     * Ensure all pte setup (eg. pte page lock and page clearing) are
407     * visible before the pte is made visible to other CPUs by being
408     * put into page tables.
409     *
410     * The other side of the story is the pointer chasing in the page
411     * table walking code (when walking the page table without locking;
412     * ie. most of the time). Fortunately, these data accesses consist
413     * of a chain of data-dependent loads, meaning most CPUs (alpha
414     * being the notable exception) will already guarantee loads are
415     * seen in-order. See the alpha page table accessors for the
416     * smp_read_barrier_depends() barriers in page table walking code.
417     */
418    smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
419
420    spin_lock(&mm->page_table_lock);
421    if (!pmd_present(*pmd)) { /* Has another populated it ? */
422        mm->nr_ptes++;
423        pmd_populate(mm, pmd, new);
424        new = NULL;
425    }
426    spin_unlock(&mm->page_table_lock);
427    if (new)
428        pte_free(mm, new);
429    return 0;
430}
431
432int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
433{
434    pte_t *new = pte_alloc_one_kernel(&init_mm, address);
435    if (!new)
436        return -ENOMEM;
437
438    smp_wmb(); /* See comment in __pte_alloc */
439
440    spin_lock(&init_mm.page_table_lock);
441    if (!pmd_present(*pmd)) { /* Has another populated it ? */
442        pmd_populate_kernel(&init_mm, pmd, new);
443        new = NULL;
444    }
445    spin_unlock(&init_mm.page_table_lock);
446    if (new)
447        pte_free_kernel(&init_mm, new);
448    return 0;
449}
450
451static inline void init_rss_vec(int *rss)
452{
453    memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
454}
455
456static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
457{
458    int i;
459
460    if (current->mm == mm)
461        sync_mm_rss(current, mm);
462    for (i = 0; i < NR_MM_COUNTERS; i++)
463        if (rss[i])
464            add_mm_counter(mm, i, rss[i]);
465}
466
467/*
468 * This function is called to print an error when a bad pte
469 * is found. For example, we might have a PFN-mapped pte in
470 * a region that doesn't allow it.
471 *
472 * The calling function must still handle the error.
473 */
474static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
475              pte_t pte, struct page *page)
476{
477    pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
478    pud_t *pud = pud_offset(pgd, addr);
479    pmd_t *pmd = pmd_offset(pud, addr);
480    struct address_space *mapping;
481    pgoff_t index;
482    static unsigned long resume;
483    static unsigned long nr_shown;
484    static unsigned long nr_unshown;
485
486    /*
487     * Allow a burst of 60 reports, then keep quiet for that minute;
488     * or allow a steady drip of one report per second.
489     */
490    if (nr_shown == 60) {
491        if (time_before(jiffies, resume)) {
492            nr_unshown++;
493            return;
494        }
495        if (nr_unshown) {
496            printk(KERN_ALERT
497                "BUG: Bad page map: %lu messages suppressed\n",
498                nr_unshown);
499            nr_unshown = 0;
500        }
501        nr_shown = 0;
502    }
503    if (nr_shown++ == 0)
504        resume = jiffies + 60 * HZ;
505
506    mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
507    index = linear_page_index(vma, addr);
508
509    printk(KERN_ALERT
510        "BUG: Bad page map in process %s pte:%08llx pmd:%08llx\n",
511        current->comm,
512        (long long)pte_val(pte), (long long)pmd_val(*pmd));
513    if (page)
514        dump_page(page);
515    printk(KERN_ALERT
516        "addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
517        (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
518    /*
519     * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
520     */
521    if (vma->vm_ops)
522        print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
523                (unsigned long)vma->vm_ops->fault);
524    if (vma->vm_file && vma->vm_file->f_op)
525        print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
526                (unsigned long)vma->vm_file->f_op->mmap);
527    dump_stack();
528    add_taint(TAINT_BAD_PAGE);
529}
530
531static inline int is_cow_mapping(unsigned int flags)
532{
533    return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
534}
535
536#ifndef is_zero_pfn
537static inline int is_zero_pfn(unsigned long pfn)
538{
539    return pfn == zero_pfn;
540}
541#endif
542
543#ifndef my_zero_pfn
544static inline unsigned long my_zero_pfn(unsigned long addr)
545{
546    return zero_pfn;
547}
548#endif
549
550/*
551 * vm_normal_page -- This function gets the "struct page" associated with a pte.
552 *
553 * "Special" mappings do not wish to be associated with a "struct page" (either
554 * it doesn't exist, or it exists but they don't want to touch it). In this
555 * case, NULL is returned here. "Normal" mappings do have a struct page.
556 *
557 * There are 2 broad cases. Firstly, an architecture may define a pte_special()
558 * pte bit, in which case this function is trivial. Secondly, an architecture
559 * may not have a spare pte bit, which requires a more complicated scheme,
560 * described below.
561 *
562 * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
563 * special mapping (even if there are underlying and valid "struct pages").
564 * COWed pages of a VM_PFNMAP are always normal.
565 *
566 * The way we recognize COWed pages within VM_PFNMAP mappings is through the
567 * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
568 * set, and the vm_pgoff will point to the first PFN mapped: thus every special
569 * mapping will always honor the rule
570 *
571 * pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
572 *
573 * And for normal mappings this is false.
574 *
575 * This restricts such mappings to be a linear translation from virtual address
576 * to pfn. To get around this restriction, we allow arbitrary mappings so long
577 * as the vma is not a COW mapping; in that case, we know that all ptes are
578 * special (because none can have been COWed).
579 *
580 *
581 * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
582 *
583 * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
584 * page" backing, however the difference is that _all_ pages with a struct
585 * page (that is, those where pfn_valid is true) are refcounted and considered
586 * normal pages by the VM. The disadvantage is that pages are refcounted
587 * (which can be slower and simply not an option for some PFNMAP users). The
588 * advantage is that we don't have to follow the strict linearity rule of
589 * PFNMAP mappings in order to support COWable mappings.
590 *
591 */
592#ifdef __HAVE_ARCH_PTE_SPECIAL
593# define HAVE_PTE_SPECIAL 1
594#else
595# define HAVE_PTE_SPECIAL 0
596#endif
597struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
598                pte_t pte)
599{
600    unsigned long pfn = pte_pfn(pte);
601
602    if (HAVE_PTE_SPECIAL) {
603        if (likely(!pte_special(pte)))
604            goto check_pfn;
605        if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
606            return NULL;
607        if (!is_zero_pfn(pfn))
608            print_bad_pte(vma, addr, pte, NULL);
609        return NULL;
610    }
611
612    /* !HAVE_PTE_SPECIAL case follows: */
613
614    if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
615        if (vma->vm_flags & VM_MIXEDMAP) {
616            if (!pfn_valid(pfn))
617                return NULL;
618            goto out;
619        } else {
620            unsigned long off;
621            off = (addr - vma->vm_start) >> PAGE_SHIFT;
622            if (pfn == vma->vm_pgoff + off)
623                return NULL;
624            if (!is_cow_mapping(vma->vm_flags))
625                return NULL;
626        }
627    }
628
629    if (is_zero_pfn(pfn))
630        return NULL;
631check_pfn:
632    if (unlikely(pfn > highest_memmap_pfn)) {
633        print_bad_pte(vma, addr, pte, NULL);
634        return NULL;
635    }
636
637    /*
638     * NOTE! We still have PageReserved() pages in the page tables.
639     * eg. VDSO mappings can cause them to exist.
640     */
641out:
642    return pfn_to_page(pfn);
643}
644
645/*
646 * copy one vm_area from one task to the other. Assumes the page tables
647 * already present in the new task to be cleared in the whole range
648 * covered by this vma.
649 */
650
651static inline unsigned long
652copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
653        pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
654        unsigned long addr, int *rss)
655{
656    unsigned long vm_flags = vma->vm_flags;
657    pte_t pte = *src_pte;
658    struct page *page;
659
660    /* pte contains position in swap or file, so copy. */
661    if (unlikely(!pte_present(pte))) {
662        if (!pte_file(pte)) {
663            swp_entry_t entry = pte_to_swp_entry(pte);
664
665            if (swap_duplicate(entry) < 0)
666                return entry.val;
667
668            /* make sure dst_mm is on swapoff's mmlist. */
669            if (unlikely(list_empty(&dst_mm->mmlist))) {
670                spin_lock(&mmlist_lock);
671                if (list_empty(&dst_mm->mmlist))
672                    list_add(&dst_mm->mmlist,
673                         &src_mm->mmlist);
674                spin_unlock(&mmlist_lock);
675            }
676            if (likely(!non_swap_entry(entry)))
677                rss[MM_SWAPENTS]++;
678            else if (is_write_migration_entry(entry) &&
679                    is_cow_mapping(vm_flags)) {
680                /*
681                 * COW mappings require pages in both parent
682                 * and child to be set to read.
683                 */
684                make_migration_entry_read(&entry);
685                pte = swp_entry_to_pte(entry);
686                set_pte_at(src_mm, addr, src_pte, pte);
687            }
688        }
689        goto out_set_pte;
690    }
691
692    /*
693     * If it's a COW mapping, write protect it both
694     * in the parent and the child
695     */
696    if (is_cow_mapping(vm_flags)) {
697        ptep_set_wrprotect(src_mm, addr, src_pte);
698        pte = pte_wrprotect(pte);
699    }
700
701    /*
702     * If it's a shared mapping, mark it clean in
703     * the child
704     */
705    if (vm_flags & VM_SHARED)
706        pte = pte_mkclean(pte);
707    pte = pte_mkold(pte);
708
709    page = vm_normal_page(vma, addr, pte);
710    if (page) {
711        get_page(page);
712        page_dup_rmap(page);
713        if (PageAnon(page))
714            rss[MM_ANONPAGES]++;
715        else
716            rss[MM_FILEPAGES]++;
717    }
718
719out_set_pte:
720    set_pte_at(dst_mm, addr, dst_pte, pte);
721    return 0;
722}
723
724static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
725        pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
726        unsigned long addr, unsigned long end)
727{
728    pte_t *orig_src_pte, *orig_dst_pte;
729    pte_t *src_pte, *dst_pte;
730    spinlock_t *src_ptl, *dst_ptl;
731    int progress = 0;
732    int rss[NR_MM_COUNTERS];
733    swp_entry_t entry = (swp_entry_t){0};
734
735again:
736    init_rss_vec(rss);
737
738    dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
739    if (!dst_pte)
740        return -ENOMEM;
741    src_pte = pte_offset_map_nested(src_pmd, addr);
742    src_ptl = pte_lockptr(src_mm, src_pmd);
743    spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
744    orig_src_pte = src_pte;
745    orig_dst_pte = dst_pte;
746    arch_enter_lazy_mmu_mode();
747
748    do {
749        /*
750         * We are holding two locks at this point - either of them
751         * could generate latencies in another task on another CPU.
752         */
753        if (progress >= 32) {
754            progress = 0;
755            if (need_resched() ||
756                spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
757                break;
758        }
759        if (pte_none(*src_pte)) {
760            progress++;
761            continue;
762        }
763        entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
764                            vma, addr, rss);
765        if (entry.val)
766            break;
767        progress += 8;
768    } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
769
770    arch_leave_lazy_mmu_mode();
771    spin_unlock(src_ptl);
772    pte_unmap_nested(orig_src_pte);
773    add_mm_rss_vec(dst_mm, rss);
774    pte_unmap_unlock(orig_dst_pte, dst_ptl);
775    cond_resched();
776
777    if (entry.val) {
778        if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
779            return -ENOMEM;
780        progress = 0;
781    }
782    if (addr != end)
783        goto again;
784    return 0;
785}
786
787static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
788        pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
789        unsigned long addr, unsigned long end)
790{
791    pmd_t *src_pmd, *dst_pmd;
792    unsigned long next;
793
794    dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
795    if (!dst_pmd)
796        return -ENOMEM;
797    src_pmd = pmd_offset(src_pud, addr);
798    do {
799        next = pmd_addr_end(addr, end);
800        if (pmd_none_or_clear_bad(src_pmd))
801            continue;
802        if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
803                        vma, addr, next))
804            return -ENOMEM;
805    } while (dst_pmd++, src_pmd++, addr = next, addr != end);
806    return 0;
807}
808
809static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
810        pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
811        unsigned long addr, unsigned long end)
812{
813    pud_t *src_pud, *dst_pud;
814    unsigned long next;
815
816    dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
817    if (!dst_pud)
818        return -ENOMEM;
819    src_pud = pud_offset(src_pgd, addr);
820    do {
821        next = pud_addr_end(addr, end);
822        if (pud_none_or_clear_bad(src_pud))
823            continue;
824        if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
825                        vma, addr, next))
826            return -ENOMEM;
827    } while (dst_pud++, src_pud++, addr = next, addr != end);
828    return 0;
829}
830
831int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
832        struct vm_area_struct *vma)
833{
834    pgd_t *src_pgd, *dst_pgd;
835    unsigned long next;
836    unsigned long addr = vma->vm_start;
837    unsigned long end = vma->vm_end;
838    int ret;
839
840    /*
841     * Don't copy ptes where a page fault will fill them correctly.
842     * Fork becomes much lighter when there are big shared or private
843     * readonly mappings. The tradeoff is that copy_page_range is more
844     * efficient than faulting.
845     */
846    if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
847        if (!vma->anon_vma)
848            return 0;
849    }
850
851    if (is_vm_hugetlb_page(vma))
852        return copy_hugetlb_page_range(dst_mm, src_mm, vma);
853
854    if (unlikely(is_pfn_mapping(vma))) {
855        /*
856         * We do not free on error cases below as remove_vma
857         * gets called on error from higher level routine
858         */
859        ret = track_pfn_vma_copy(vma);
860        if (ret)
861            return ret;
862    }
863
864    /*
865     * We need to invalidate the secondary MMU mappings only when
866     * there could be a permission downgrade on the ptes of the
867     * parent mm. And a permission downgrade will only happen if
868     * is_cow_mapping() returns true.
869     */
870    if (is_cow_mapping(vma->vm_flags))
871        mmu_notifier_invalidate_range_start(src_mm, addr, end);
872
873    ret = 0;
874    dst_pgd = pgd_offset(dst_mm, addr);
875    src_pgd = pgd_offset(src_mm, addr);
876    do {
877        next = pgd_addr_end(addr, end);
878        if (pgd_none_or_clear_bad(src_pgd))
879            continue;
880        if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
881                        vma, addr, next))) {
882            ret = -ENOMEM;
883            break;
884        }
885    } while (dst_pgd++, src_pgd++, addr = next, addr != end);
886
887    if (is_cow_mapping(vma->vm_flags))
888        mmu_notifier_invalidate_range_end(src_mm,
889                          vma->vm_start, end);
890    return ret;
891}
892
893static unsigned long zap_pte_range(struct mmu_gather *tlb,
894                struct vm_area_struct *vma, pmd_t *pmd,
895                unsigned long addr, unsigned long end,
896                long *zap_work, struct zap_details *details)
897{
898    struct mm_struct *mm = tlb->mm;
899    pte_t *pte;
900    spinlock_t *ptl;
901    int rss[NR_MM_COUNTERS];
902
903    init_rss_vec(rss);
904
905    pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
906    arch_enter_lazy_mmu_mode();
907    do {
908        pte_t ptent = *pte;
909        if (pte_none(ptent)) {
910            (*zap_work)--;
911            continue;
912        }
913
914        (*zap_work) -= PAGE_SIZE;
915
916        if (pte_present(ptent)) {
917            struct page *page;
918
919            page = vm_normal_page(vma, addr, ptent);
920            if (unlikely(details) && page) {
921                /*
922                 * unmap_shared_mapping_pages() wants to
923                 * invalidate cache without truncating:
924                 * unmap shared but keep private pages.
925                 */
926                if (details->check_mapping &&
927                    details->check_mapping != page->mapping)
928                    continue;
929                /*
930                 * Each page->index must be checked when
931                 * invalidating or truncating nonlinear.
932                 */
933                if (details->nonlinear_vma &&
934                    (page->index < details->first_index ||
935                     page->index > details->last_index))
936                    continue;
937            }
938            ptent = ptep_get_and_clear_full(mm, addr, pte,
939                            tlb->fullmm);
940            tlb_remove_tlb_entry(tlb, pte, addr);
941            if (unlikely(!page))
942                continue;
943            if (unlikely(details) && details->nonlinear_vma
944                && linear_page_index(details->nonlinear_vma,
945                        addr) != page->index)
946                set_pte_at(mm, addr, pte,
947                       pgoff_to_pte(page->index));
948            if (PageAnon(page))
949                rss[MM_ANONPAGES]--;
950            else {
951                if (pte_dirty(ptent))
952                    set_page_dirty(page);
953                if (pte_young(ptent) &&
954                    likely(!VM_SequentialReadHint(vma)))
955                    mark_page_accessed(page);
956                rss[MM_FILEPAGES]--;
957            }
958            page_remove_rmap(page);
959            if (unlikely(page_mapcount(page) < 0))
960                print_bad_pte(vma, addr, ptent, page);
961            tlb_remove_page(tlb, page);
962            continue;
963        }
964        /*
965         * If details->check_mapping, we leave swap entries;
966         * if details->nonlinear_vma, we leave file entries.
967         */
968        if (unlikely(details))
969            continue;
970        if (pte_file(ptent)) {
971            if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
972                print_bad_pte(vma, addr, ptent, NULL);
973        } else {
974            swp_entry_t entry = pte_to_swp_entry(ptent);
975
976            if (!non_swap_entry(entry))
977                rss[MM_SWAPENTS]--;
978            if (unlikely(!free_swap_and_cache(entry)))
979                print_bad_pte(vma, addr, ptent, NULL);
980        }
981        pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
982    } while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
983
984    add_mm_rss_vec(mm, rss);
985    arch_leave_lazy_mmu_mode();
986    pte_unmap_unlock(pte - 1, ptl);
987
988    return addr;
989}
990
991static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
992                struct vm_area_struct *vma, pud_t *pud,
993                unsigned long addr, unsigned long end,
994                long *zap_work, struct zap_details *details)
995{
996    pmd_t *pmd;
997    unsigned long next;
998
999    pmd = pmd_offset(pud, addr);
1000    do {
1001        next = pmd_addr_end(addr, end);
1002        if (pmd_none_or_clear_bad(pmd)) {
1003            (*zap_work)--;
1004            continue;
1005        }
1006        next = zap_pte_range(tlb, vma, pmd, addr, next,
1007                        zap_work, details);
1008    } while (pmd++, addr = next, (addr != end && *zap_work > 0));
1009
1010    return addr;
1011}
1012
1013static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1014                struct vm_area_struct *vma, pgd_t *pgd,
1015                unsigned long addr, unsigned long end,
1016                long *zap_work, struct zap_details *details)
1017{
1018    pud_t *pud;
1019    unsigned long next;
1020
1021    pud = pud_offset(pgd, addr);
1022    do {
1023        next = pud_addr_end(addr, end);
1024        if (pud_none_or_clear_bad(pud)) {
1025            (*zap_work)--;
1026            continue;
1027        }
1028        next = zap_pmd_range(tlb, vma, pud, addr, next,
1029                        zap_work, details);
1030    } while (pud++, addr = next, (addr != end && *zap_work > 0));
1031
1032    return addr;
1033}
1034
1035static unsigned long unmap_page_range(struct mmu_gather *tlb,
1036                struct vm_area_struct *vma,
1037                unsigned long addr, unsigned long end,
1038                long *zap_work, struct zap_details *details)
1039{
1040    pgd_t *pgd;
1041    unsigned long next;
1042
1043    if (details && !details->check_mapping && !details->nonlinear_vma)
1044        details = NULL;
1045
1046    BUG_ON(addr >= end);
1047    mem_cgroup_uncharge_start();
1048    tlb_start_vma(tlb, vma);
1049    pgd = pgd_offset(vma->vm_mm, addr);
1050    do {
1051        next = pgd_addr_end(addr, end);
1052        if (pgd_none_or_clear_bad(pgd)) {
1053            (*zap_work)--;
1054            continue;
1055        }
1056        next = zap_pud_range(tlb, vma, pgd, addr, next,
1057                        zap_work, details);
1058    } while (pgd++, addr = next, (addr != end && *zap_work > 0));
1059    tlb_end_vma(tlb, vma);
1060    mem_cgroup_uncharge_end();
1061
1062    return addr;
1063}
1064
1065#ifdef CONFIG_PREEMPT
1066# define ZAP_BLOCK_SIZE (8 * PAGE_SIZE)
1067#else
1068/* No preempt: go for improved straight-line efficiency */
1069# define ZAP_BLOCK_SIZE (1024 * PAGE_SIZE)
1070#endif
1071
1072/**
1073 * unmap_vmas - unmap a range of memory covered by a list of vma's
1074 * @tlbp: address of the caller's struct mmu_gather
1075 * @vma: the starting vma
1076 * @start_addr: virtual address at which to start unmapping
1077 * @end_addr: virtual address at which to end unmapping
1078 * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
1079 * @details: details of nonlinear truncation or shared cache invalidation
1080 *
1081 * Returns the end address of the unmapping (restart addr if interrupted).
1082 *
1083 * Unmap all pages in the vma list.
1084 *
1085 * We aim to not hold locks for too long (for scheduling latency reasons).
1086 * So zap pages in ZAP_BLOCK_SIZE bytecounts. This means we need to
1087 * return the ending mmu_gather to the caller.
1088 *
1089 * Only addresses between `start' and `end' will be unmapped.
1090 *
1091 * The VMA list must be sorted in ascending virtual address order.
1092 *
1093 * unmap_vmas() assumes that the caller will flush the whole unmapped address
1094 * range after unmap_vmas() returns. So the only responsibility here is to
1095 * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1096 * drops the lock and schedules.
1097 */
1098unsigned long unmap_vmas(struct mmu_gather **tlbp,
1099        struct vm_area_struct *vma, unsigned long start_addr,
1100        unsigned long end_addr, unsigned long *nr_accounted,
1101        struct zap_details *details)
1102{
1103    long zap_work = ZAP_BLOCK_SIZE;
1104    unsigned long tlb_start = 0; /* For tlb_finish_mmu */
1105    int tlb_start_valid = 0;
1106    unsigned long start = start_addr;
1107    spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
1108    int fullmm = (*tlbp)->fullmm;
1109    struct mm_struct *mm = vma->vm_mm;
1110
1111    mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1112    for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
1113        unsigned long end;
1114
1115        start = max(vma->vm_start, start_addr);
1116        if (start >= vma->vm_end)
1117            continue;
1118        end = min(vma->vm_end, end_addr);
1119        if (end <= vma->vm_start)
1120            continue;
1121
1122        if (vma->vm_flags & VM_ACCOUNT)
1123            *nr_accounted += (end - start) >> PAGE_SHIFT;
1124
1125        if (unlikely(is_pfn_mapping(vma)))
1126            untrack_pfn_vma(vma, 0, 0);
1127
1128        while (start != end) {
1129            if (!tlb_start_valid) {
1130                tlb_start = start;
1131                tlb_start_valid = 1;
1132            }
1133
1134            if (unlikely(is_vm_hugetlb_page(vma))) {
1135                /*
1136                 * It is undesirable to test vma->vm_file as it
1137                 * should be non-null for valid hugetlb area.
1138                 * However, vm_file will be NULL in the error
1139                 * cleanup path of do_mmap_pgoff. When
1140                 * hugetlbfs ->mmap method fails,
1141                 * do_mmap_pgoff() nullifies vma->vm_file
1142                 * before calling this function to clean up.
1143                 * Since no pte has actually been setup, it is
1144                 * safe to do nothing in this case.
1145                 */
1146                if (vma->vm_file) {
1147                    unmap_hugepage_range(vma, start, end, NULL);
1148                    zap_work -= (end - start) /
1149                    pages_per_huge_page(hstate_vma(vma));
1150                }
1151
1152                start = end;
1153            } else
1154                start = unmap_page_range(*tlbp, vma,
1155                        start, end, &zap_work, details);
1156
1157            if (zap_work > 0) {
1158                BUG_ON(start != end);
1159                break;
1160            }
1161
1162            tlb_finish_mmu(*tlbp, tlb_start, start);
1163
1164            if (need_resched() ||
1165                (i_mmap_lock && spin_needbreak(i_mmap_lock))) {
1166                if (i_mmap_lock) {
1167                    *tlbp = NULL;
1168                    goto out;
1169                }
1170                cond_resched();
1171            }
1172
1173            *tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
1174            tlb_start_valid = 0;
1175            zap_work = ZAP_BLOCK_SIZE;
1176        }
1177    }
1178out:
1179    mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1180    return start; /* which is now the end (or restart) address */
1181}
1182
1183/**
1184 * zap_page_range - remove user pages in a given range
1185 * @vma: vm_area_struct holding the applicable pages
1186 * @address: starting address of pages to zap
1187 * @size: number of bytes to zap
1188 * @details: details of nonlinear truncation or shared cache invalidation
1189 */
1190unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
1191        unsigned long size, struct zap_details *details)
1192{
1193    struct mm_struct *mm = vma->vm_mm;
1194    struct mmu_gather *tlb;
1195    unsigned long end = address + size;
1196    unsigned long nr_accounted = 0;
1197
1198    lru_add_drain();
1199    tlb = tlb_gather_mmu(mm, 0);
1200    update_hiwater_rss(mm);
1201    end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
1202    if (tlb)
1203        tlb_finish_mmu(tlb, address, end);
1204    return end;
1205}
1206
1207/**
1208 * zap_vma_ptes - remove ptes mapping the vma
1209 * @vma: vm_area_struct holding ptes to be zapped
1210 * @address: starting address of pages to zap
1211 * @size: number of bytes to zap
1212 *
1213 * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1214 *
1215 * The entire address range must be fully contained within the vma.
1216 *
1217 * Returns 0 if successful.
1218 */
1219int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1220        unsigned long size)
1221{
1222    if (address < vma->vm_start || address + size > vma->vm_end ||
1223                !(vma->vm_flags & VM_PFNMAP))
1224        return -1;
1225    zap_page_range(vma, address, size, NULL);
1226    return 0;
1227}
1228EXPORT_SYMBOL_GPL(zap_vma_ptes);
1229
1230/**
1231 * follow_page - look up a page descriptor from a user-virtual address
1232 * @vma: vm_area_struct mapping @address
1233 * @address: virtual address to look up
1234 * @flags: flags modifying lookup behaviour
1235 *
1236 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
1237 *
1238 * Returns the mapped (struct page *), %NULL if no mapping exists, or
1239 * an error pointer if there is a mapping to something not represented
1240 * by a page descriptor (see also vm_normal_page()).
1241 */
1242struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1243            unsigned int flags)
1244{
1245    pgd_t *pgd;
1246    pud_t *pud;
1247    pmd_t *pmd;
1248    pte_t *ptep, pte;
1249    spinlock_t *ptl;
1250    struct page *page;
1251    struct mm_struct *mm = vma->vm_mm;
1252
1253    page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1254    if (!IS_ERR(page)) {
1255        BUG_ON(flags & FOLL_GET);
1256        goto out;
1257    }
1258
1259    page = NULL;
1260    pgd = pgd_offset(mm, address);
1261    if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1262        goto no_page_table;
1263
1264    pud = pud_offset(pgd, address);
1265    if (pud_none(*pud))
1266        goto no_page_table;
1267    if (pud_huge(*pud)) {
1268        BUG_ON(flags & FOLL_GET);
1269        page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1270        goto out;
1271    }
1272    if (unlikely(pud_bad(*pud)))
1273        goto no_page_table;
1274
1275    pmd = pmd_offset(pud, address);
1276    if (pmd_none(*pmd))
1277        goto no_page_table;
1278    if (pmd_huge(*pmd)) {
1279        BUG_ON(flags & FOLL_GET);
1280        page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1281        goto out;
1282    }
1283    if (unlikely(pmd_bad(*pmd)))
1284        goto no_page_table;
1285
1286    ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1287
1288    pte = *ptep;
1289    if (!pte_present(pte))
1290        goto no_page;
1291    if ((flags & FOLL_WRITE) && !pte_write(pte))
1292        goto unlock;
1293
1294    page = vm_normal_page(vma, address, pte);
1295    if (unlikely(!page)) {
1296        if ((flags & FOLL_DUMP) ||
1297            !is_zero_pfn(pte_pfn(pte)))
1298            goto bad_page;
1299        page = pte_page(pte);
1300    }
1301
1302    if (flags & FOLL_GET)
1303        get_page(page);
1304    if (flags & FOLL_TOUCH) {
1305        if ((flags & FOLL_WRITE) &&
1306            !pte_dirty(pte) && !PageDirty(page))
1307            set_page_dirty(page);
1308        /*
1309         * pte_mkyoung() would be more correct here, but atomic care
1310         * is needed to avoid losing the dirty bit: it is easier to use
1311         * mark_page_accessed().
1312         */
1313        mark_page_accessed(page);
1314    }
1315unlock:
1316    pte_unmap_unlock(ptep, ptl);
1317out:
1318    return page;
1319
1320bad_page:
1321    pte_unmap_unlock(ptep, ptl);
1322    return ERR_PTR(-EFAULT);
1323
1324no_page:
1325    pte_unmap_unlock(ptep, ptl);
1326    if (!pte_none(pte))
1327        return page;
1328
1329no_page_table:
1330    /*
1331     * When core dumping an enormous anonymous area that nobody
1332     * has touched so far, we don't want to allocate unnecessary pages or
1333     * page tables. Return error instead of NULL to skip handle_mm_fault,
1334     * then get_dump_page() will return NULL to leave a hole in the dump.
1335     * But we can only make this optimization where a hole would surely
1336     * be zero-filled if handle_mm_fault() actually did handle it.
1337     */
1338    if ((flags & FOLL_DUMP) &&
1339        (!vma->vm_ops || !vma->vm_ops->fault))
1340        return ERR_PTR(-EFAULT);
1341    return page;
1342}
1343
1344int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1345             unsigned long start, int nr_pages, unsigned int gup_flags,
1346             struct page **pages, struct vm_area_struct **vmas)
1347{
1348    int i;
1349    unsigned long vm_flags;
1350
1351    if (nr_pages <= 0)
1352        return 0;
1353
1354    VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1355
1356    /*
1357     * Require read or write permissions.
1358     * If FOLL_FORCE is set, we only require the "MAY" flags.
1359     */
1360    vm_flags = (gup_flags & FOLL_WRITE) ?
1361            (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1362    vm_flags &= (gup_flags & FOLL_FORCE) ?
1363            (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1364    i = 0;
1365
1366    do {
1367        struct vm_area_struct *vma;
1368
1369        vma = find_extend_vma(mm, start);
1370        if (!vma && in_gate_area(tsk, start)) {
1371            unsigned long pg = start & PAGE_MASK;
1372            struct vm_area_struct *gate_vma = get_gate_vma(tsk);
1373            pgd_t *pgd;
1374            pud_t *pud;
1375            pmd_t *pmd;
1376            pte_t *pte;
1377
1378            /* user gate pages are read-only */
1379            if (gup_flags & FOLL_WRITE)
1380                return i ? : -EFAULT;
1381            if (pg > TASK_SIZE)
1382                pgd = pgd_offset_k(pg);
1383            else
1384                pgd = pgd_offset_gate(mm, pg);
1385            BUG_ON(pgd_none(*pgd));
1386            pud = pud_offset(pgd, pg);
1387            BUG_ON(pud_none(*pud));
1388            pmd = pmd_offset(pud, pg);
1389            if (pmd_none(*pmd))
1390                return i ? : -EFAULT;
1391            pte = pte_offset_map(pmd, pg);
1392            if (pte_none(*pte)) {
1393                pte_unmap(pte);
1394                return i ? : -EFAULT;
1395            }
1396            if (pages) {
1397                struct page *page;
1398
1399                page = vm_normal_page(gate_vma, start, *pte);
1400                if (!page) {
1401                    if (!(gup_flags & FOLL_DUMP) &&
1402                         is_zero_pfn(pte_pfn(*pte)))
1403                        page = pte_page(*pte);
1404                    else {
1405                        pte_unmap(pte);
1406                        return i ? : -EFAULT;
1407                    }
1408                }
1409                pages[i] = page;
1410                get_page(page);
1411            }
1412            pte_unmap(pte);
1413            if (vmas)
1414                vmas[i] = gate_vma;
1415            i++;
1416            start += PAGE_SIZE;
1417            nr_pages--;
1418            continue;
1419        }
1420
1421        if (!vma ||
1422            (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1423            !(vm_flags & vma->vm_flags))
1424            return i ? : -EFAULT;
1425
1426        if (is_vm_hugetlb_page(vma)) {
1427            i = follow_hugetlb_page(mm, vma, pages, vmas,
1428                    &start, &nr_pages, i, gup_flags);
1429            continue;
1430        }
1431
1432        do {
1433            struct page *page;
1434            unsigned int foll_flags = gup_flags;
1435
1436            /*
1437             * If we have a pending SIGKILL, don't keep faulting
1438             * pages and potentially allocating memory.
1439             */
1440            if (unlikely(fatal_signal_pending(current)))
1441                return i ? i : -ERESTARTSYS;
1442
1443            cond_resched();
1444            while (!(page = follow_page(vma, start, foll_flags))) {
1445                int ret;
1446
1447                ret = handle_mm_fault(mm, vma, start,
1448                    (foll_flags & FOLL_WRITE) ?
1449                    FAULT_FLAG_WRITE : 0);
1450
1451                if (ret & VM_FAULT_ERROR) {
1452                    if (ret & VM_FAULT_OOM)
1453                        return i ? i : -ENOMEM;
1454                    if (ret &
1455                        (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))
1456                        return i ? i : -EFAULT;
1457                    BUG();
1458                }
1459                if (ret & VM_FAULT_MAJOR)
1460                    tsk->maj_flt++;
1461                else
1462                    tsk->min_flt++;
1463
1464                /*
1465                 * The VM_FAULT_WRITE bit tells us that
1466                 * do_wp_page has broken COW when necessary,
1467                 * even if maybe_mkwrite decided not to set
1468                 * pte_write. We can thus safely do subsequent
1469                 * page lookups as if they were reads. But only
1470                 * do so when looping for pte_write is futile:
1471                 * in some cases userspace may also be wanting
1472                 * to write to the gotten user page, which a
1473                 * read fault here might prevent (a readonly
1474                 * page might get reCOWed by userspace write).
1475                 */
1476                if ((ret & VM_FAULT_WRITE) &&
1477                    !(vma->vm_flags & VM_WRITE))
1478                    foll_flags &= ~FOLL_WRITE;
1479
1480                cond_resched();
1481            }
1482            if (IS_ERR(page))
1483                return i ? i : PTR_ERR(page);
1484            if (pages) {
1485                pages[i] = page;
1486
1487                flush_anon_page(vma, page, start);
1488                flush_dcache_page(page);
1489            }
1490            if (vmas)
1491                vmas[i] = vma;
1492            i++;
1493            start += PAGE_SIZE;
1494            nr_pages--;
1495        } while (nr_pages && start < vma->vm_end);
1496    } while (nr_pages);
1497    return i;
1498}
1499
1500/**
1501 * get_user_pages() - pin user pages in memory
1502 * @tsk: task_struct of target task
1503 * @mm: mm_struct of target mm
1504 * @start: starting user address
1505 * @nr_pages: number of pages from start to pin
1506 * @write: whether pages will be written to by the caller
1507 * @force: whether to force write access even if user mapping is
1508 * readonly. This will result in the page being COWed even
1509 * in MAP_SHARED mappings. You do not want this.
1510 * @pages: array that receives pointers to the pages pinned.
1511 * Should be at least nr_pages long. Or NULL, if caller
1512 * only intends to ensure the pages are faulted in.
1513 * @vmas: array of pointers to vmas corresponding to each page.
1514 * Or NULL if the caller does not require them.
1515 *
1516 * Returns number of pages pinned. This may be fewer than the number
1517 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1518 * were pinned, returns -errno. Each page returned must be released
1519 * with a put_page() call when it is finished with. vmas will only
1520 * remain valid while mmap_sem is held.
1521 *
1522 * Must be called with mmap_sem held for read or write.
1523 *
1524 * get_user_pages walks a process's page tables and takes a reference to
1525 * each struct page that each user address corresponds to at a given
1526 * instant. That is, it takes the page that would be accessed if a user
1527 * thread accesses the given user virtual address at that instant.
1528 *
1529 * This does not guarantee that the page exists in the user mappings when
1530 * get_user_pages returns, and there may even be a completely different
1531 * page there in some cases (eg. if mmapped pagecache has been invalidated
1532 * and subsequently re faulted). However it does guarantee that the page
1533 * won't be freed completely. And mostly callers simply care that the page
1534 * contains data that was valid *at some point in time*. Typically, an IO
1535 * or similar operation cannot guarantee anything stronger anyway because
1536 * locks can't be held over the syscall boundary.
1537 *
1538 * If write=0, the page must not be written to. If the page is written to,
1539 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
1540 * after the page is finished with, and before put_page is called.
1541 *
1542 * get_user_pages is typically used for fewer-copy IO operations, to get a
1543 * handle on the memory by some means other than accesses via the user virtual
1544 * addresses. The pages may be submitted for DMA to devices or accessed via
1545 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1546 * use the correct cache flushing APIs.
1547 *
1548 * See also get_user_pages_fast, for performance critical applications.
1549 */
1550int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1551        unsigned long start, int nr_pages, int write, int force,
1552        struct page **pages, struct vm_area_struct **vmas)
1553{
1554    int flags = FOLL_TOUCH;
1555
1556    if (pages)
1557        flags |= FOLL_GET;
1558    if (write)
1559        flags |= FOLL_WRITE;
1560    if (force)
1561        flags |= FOLL_FORCE;
1562
1563    return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
1564}
1565EXPORT_SYMBOL(get_user_pages);
1566
1567/**
1568 * get_dump_page() - pin user page in memory while writing it to core dump
1569 * @addr: user address
1570 *
1571 * Returns struct page pointer of user page pinned for dump,
1572 * to be freed afterwards by page_cache_release() or put_page().
1573 *
1574 * Returns NULL on any kind of failure - a hole must then be inserted into
1575 * the corefile, to preserve alignment with its headers; and also returns
1576 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1577 * allowing a hole to be left in the corefile to save diskspace.
1578 *
1579 * Called without mmap_sem, but after all other threads have been killed.
1580 */
1581#ifdef CONFIG_ELF_CORE
1582struct page *get_dump_page(unsigned long addr)
1583{
1584    struct vm_area_struct *vma;
1585    struct page *page;
1586
1587    if (__get_user_pages(current, current->mm, addr, 1,
1588            FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)
1589        return NULL;
1590    flush_cache_page(vma, addr, page_to_pfn(page));
1591    return page;
1592}
1593#endif /* CONFIG_ELF_CORE */
1594
1595pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
1596            spinlock_t **ptl)
1597{
1598    pgd_t * pgd = pgd_offset(mm, addr);
1599    pud_t * pud = pud_alloc(mm, pgd, addr);
1600    if (pud) {
1601        pmd_t * pmd = pmd_alloc(mm, pud, addr);
1602        if (pmd)
1603            return pte_alloc_map_lock(mm, pmd, addr, ptl);
1604    }
1605    return NULL;
1606}
1607
1608/*
1609 * This is the old fallback for page remapping.
1610 *
1611 * For historical reasons, it only allows reserved pages. Only
1612 * old drivers should use this, and they needed to mark their
1613 * pages reserved for the old functions anyway.
1614 */
1615static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1616            struct page *page, pgprot_t prot)
1617{
1618    struct mm_struct *mm = vma->vm_mm;
1619    int retval;
1620    pte_t *pte;
1621    spinlock_t *ptl;
1622
1623    retval = -EINVAL;
1624    if (PageAnon(page))
1625        goto out;
1626    retval = -ENOMEM;
1627    flush_dcache_page(page);
1628    pte = get_locked_pte(mm, addr, &ptl);
1629    if (!pte)
1630        goto out;
1631    retval = -EBUSY;
1632    if (!pte_none(*pte))
1633        goto out_unlock;
1634
1635    /* Ok, finally just insert the thing.. */
1636    get_page(page);
1637    inc_mm_counter_fast(mm, MM_FILEPAGES);
1638    page_add_file_rmap(page);
1639    set_pte_at(mm, addr, pte, mk_pte(page, prot));
1640
1641    retval = 0;
1642    pte_unmap_unlock(pte, ptl);
1643    return retval;
1644out_unlock:
1645    pte_unmap_unlock(pte, ptl);
1646out:
1647    return retval;
1648}
1649
1650/**
1651 * vm_insert_page - insert single page into user vma
1652 * @vma: user vma to map to
1653 * @addr: target user address of this page
1654 * @page: source kernel page
1655 *
1656 * This allows drivers to insert individual pages they've allocated
1657 * into a user vma.
1658 *
1659 * The page has to be a nice clean _individual_ kernel allocation.
1660 * If you allocate a compound page, you need to have marked it as
1661 * such (__GFP_COMP), or manually just split the page up yourself
1662 * (see split_page()).
1663 *
1664 * NOTE! Traditionally this was done with "remap_pfn_range()" which
1665 * took an arbitrary page protection parameter. This doesn't allow
1666 * that. Your vma protection will have to be set up correctly, which
1667 * means that if you want a shared writable mapping, you'd better
1668 * ask for a shared writable mapping!
1669 *
1670 * The page does not need to be reserved.
1671 */
1672int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1673            struct page *page)
1674{
1675    if (addr < vma->vm_start || addr >= vma->vm_end)
1676        return -EFAULT;
1677    if (!page_count(page))
1678        return -EINVAL;
1679    vma->vm_flags |= VM_INSERTPAGE;
1680    return insert_page(vma, addr, page, vma->vm_page_prot);
1681}
1682EXPORT_SYMBOL(vm_insert_page);
1683
1684static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1685            unsigned long pfn, pgprot_t prot)
1686{
1687    struct mm_struct *mm = vma->vm_mm;
1688    int retval;
1689    pte_t *pte, entry;
1690    spinlock_t *ptl;
1691
1692    retval = -ENOMEM;
1693    pte = get_locked_pte(mm, addr, &ptl);
1694    if (!pte)
1695        goto out;
1696    retval = -EBUSY;
1697    if (!pte_none(*pte))
1698        goto out_unlock;
1699
1700    /* Ok, finally just insert the thing.. */
1701    entry = pte_mkspecial(pfn_pte(pfn, prot));
1702    set_pte_at(mm, addr, pte, entry);
1703    update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
1704
1705    retval = 0;
1706out_unlock:
1707    pte_unmap_unlock(pte, ptl);
1708out:
1709    return retval;
1710}
1711
1712/**
1713 * vm_insert_pfn - insert single pfn into user vma
1714 * @vma: user vma to map to
1715 * @addr: target user address of this page
1716 * @pfn: source kernel pfn
1717 *
1718 * Similar to vm_inert_page, this allows drivers to insert individual pages
1719 * they've allocated into a user vma. Same comments apply.
1720 *
1721 * This function should only be called from a vm_ops->fault handler, and
1722 * in that case the handler should return NULL.
1723 *
1724 * vma cannot be a COW mapping.
1725 *
1726 * As this is called only for pages that do not currently exist, we
1727 * do not need to flush old virtual caches or the TLB.
1728 */
1729int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1730            unsigned long pfn)
1731{
1732    int ret;
1733    pgprot_t pgprot = vma->vm_page_prot;
1734    /*
1735     * Technically, architectures with pte_special can avoid all these
1736     * restrictions (same for remap_pfn_range). However we would like
1737     * consistency in testing and feature parity among all, so we should
1738     * try to keep these invariants in place for everybody.
1739     */
1740    BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1741    BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1742                        (VM_PFNMAP|VM_MIXEDMAP));
1743    BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1744    BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1745
1746    if (addr < vma->vm_start || addr >= vma->vm_end)
1747        return -EFAULT;
1748    if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
1749        return -EINVAL;
1750
1751    ret = insert_pfn(vma, addr, pfn, pgprot);
1752
1753    if (ret)
1754        untrack_pfn_vma(vma, pfn, PAGE_SIZE);
1755
1756    return ret;
1757}
1758EXPORT_SYMBOL(vm_insert_pfn);
1759
1760int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1761            unsigned long pfn)
1762{
1763    BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1764
1765    if (addr < vma->vm_start || addr >= vma->vm_end)
1766        return -EFAULT;
1767
1768    /*
1769     * If we don't have pte special, then we have to use the pfn_valid()
1770     * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1771     * refcount the page if pfn_valid is true (hence insert_page rather
1772     * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP
1773     * without pte special, it would there be refcounted as a normal page.
1774     */
1775    if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1776        struct page *page;
1777
1778        page = pfn_to_page(pfn);
1779        return insert_page(vma, addr, page, vma->vm_page_prot);
1780    }
1781    return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1782}
1783EXPORT_SYMBOL(vm_insert_mixed);
1784
1785/*
1786 * maps a range of physical memory into the requested pages. the old
1787 * mappings are removed. any references to nonexistent pages results
1788 * in null mappings (currently treated as "copy-on-access")
1789 */
1790static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1791            unsigned long addr, unsigned long end,
1792            unsigned long pfn, pgprot_t prot)
1793{
1794    pte_t *pte;
1795    spinlock_t *ptl;
1796
1797    pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1798    if (!pte)
1799        return -ENOMEM;
1800    arch_enter_lazy_mmu_mode();
1801    do {
1802        BUG_ON(!pte_none(*pte));
1803        set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1804        pfn++;
1805    } while (pte++, addr += PAGE_SIZE, addr != end);
1806    arch_leave_lazy_mmu_mode();
1807    pte_unmap_unlock(pte - 1, ptl);
1808    return 0;
1809}
1810
1811static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1812            unsigned long addr, unsigned long end,
1813            unsigned long pfn, pgprot_t prot)
1814{
1815    pmd_t *pmd;
1816    unsigned long next;
1817
1818    pfn -= addr >> PAGE_SHIFT;
1819    pmd = pmd_alloc(mm, pud, addr);
1820    if (!pmd)
1821        return -ENOMEM;
1822    do {
1823        next = pmd_addr_end(addr, end);
1824        if (remap_pte_range(mm, pmd, addr, next,
1825                pfn + (addr >> PAGE_SHIFT), prot))
1826            return -ENOMEM;
1827    } while (pmd++, addr = next, addr != end);
1828    return 0;
1829}
1830
1831static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1832            unsigned long addr, unsigned long end,
1833            unsigned long pfn, pgprot_t prot)
1834{
1835    pud_t *pud;
1836    unsigned long next;
1837
1838    pfn -= addr >> PAGE_SHIFT;
1839    pud = pud_alloc(mm, pgd, addr);
1840    if (!pud)
1841        return -ENOMEM;
1842    do {
1843        next = pud_addr_end(addr, end);
1844        if (remap_pmd_range(mm, pud, addr, next,
1845                pfn + (addr >> PAGE_SHIFT), prot))
1846            return -ENOMEM;
1847    } while (pud++, addr = next, addr != end);
1848    return 0;
1849}
1850
1851/**
1852 * remap_pfn_range - remap kernel memory to userspace
1853 * @vma: user vma to map to
1854 * @addr: target user address to start at
1855 * @pfn: physical address of kernel memory
1856 * @size: size of map area
1857 * @prot: page protection flags for this mapping
1858 *
1859 * Note: this is only safe if the mm semaphore is held when called.
1860 */
1861int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1862            unsigned long pfn, unsigned long size, pgprot_t prot)
1863{
1864    pgd_t *pgd;
1865    unsigned long next;
1866    unsigned long end = addr + PAGE_ALIGN(size);
1867    struct mm_struct *mm = vma->vm_mm;
1868    int err;
1869
1870    /*
1871     * Physically remapped pages are special. Tell the
1872     * rest of the world about it:
1873     * VM_IO tells people not to look at these pages
1874     * (accesses can have side effects).
1875     * VM_RESERVED is specified all over the place, because
1876     * in 2.4 it kept swapout's vma scan off this vma; but
1877     * in 2.6 the LRU scan won't even find its pages, so this
1878     * flag means no more than count its pages in reserved_vm,
1879     * and omit it from core dump, even when VM_IO turned off.
1880     * VM_PFNMAP tells the core MM that the base pages are just
1881     * raw PFN mappings, and do not have a "struct page" associated
1882     * with them.
1883     *
1884     * There's a horrible special case to handle copy-on-write
1885     * behaviour that some programs depend on. We mark the "original"
1886     * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1887     */
1888    if (addr == vma->vm_start && end == vma->vm_end) {
1889        vma->vm_pgoff = pfn;
1890        vma->vm_flags |= VM_PFN_AT_MMAP;
1891    } else if (is_cow_mapping(vma->vm_flags))
1892        return -EINVAL;
1893
1894    vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1895
1896    err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
1897    if (err) {
1898        /*
1899         * To indicate that track_pfn related cleanup is not
1900         * needed from higher level routine calling unmap_vmas
1901         */
1902        vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
1903        vma->vm_flags &= ~VM_PFN_AT_MMAP;
1904        return -EINVAL;
1905    }
1906
1907    BUG_ON(addr >= end);
1908    pfn -= addr >> PAGE_SHIFT;
1909    pgd = pgd_offset(mm, addr);
1910    flush_cache_range(vma, addr, end);
1911    do {
1912        next = pgd_addr_end(addr, end);
1913        err = remap_pud_range(mm, pgd, addr, next,
1914                pfn + (addr >> PAGE_SHIFT), prot);
1915        if (err)
1916            break;
1917    } while (pgd++, addr = next, addr != end);
1918
1919    if (err)
1920        untrack_pfn_vma(vma, pfn, PAGE_ALIGN(size));
1921
1922    return err;
1923}
1924EXPORT_SYMBOL(remap_pfn_range);
1925
1926static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1927                     unsigned long addr, unsigned long end,
1928                     pte_fn_t fn, void *data)
1929{
1930    pte_t *pte;
1931    int err;
1932    pgtable_t token;
1933    spinlock_t *uninitialized_var(ptl);
1934
1935    pte = (mm == &init_mm) ?
1936        pte_alloc_kernel(pmd, addr) :
1937        pte_alloc_map_lock(mm, pmd, addr, &ptl);
1938    if (!pte)
1939        return -ENOMEM;
1940
1941    BUG_ON(pmd_huge(*pmd));
1942
1943    arch_enter_lazy_mmu_mode();
1944
1945    token = pmd_pgtable(*pmd);
1946
1947    do {
1948        err = fn(pte++, token, addr, data);
1949        if (err)
1950            break;
1951    } while (addr += PAGE_SIZE, addr != end);
1952
1953    arch_leave_lazy_mmu_mode();
1954
1955    if (mm != &init_mm)
1956        pte_unmap_unlock(pte-1, ptl);
1957    return err;
1958}
1959
1960static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1961                     unsigned long addr, unsigned long end,
1962                     pte_fn_t fn, void *data)
1963{
1964    pmd_t *pmd;
1965    unsigned long next;
1966    int err;
1967
1968    BUG_ON(pud_huge(*pud));
1969
1970    pmd = pmd_alloc(mm, pud, addr);
1971    if (!pmd)
1972        return -ENOMEM;
1973    do {
1974        next = pmd_addr_end(addr, end);
1975        err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1976        if (err)
1977            break;
1978    } while (pmd++, addr = next, addr != end);
1979    return err;
1980}
1981
1982static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1983                     unsigned long addr, unsigned long end,
1984                     pte_fn_t fn, void *data)
1985{
1986    pud_t *pud;
1987    unsigned long next;
1988    int err;
1989
1990    pud = pud_alloc(mm, pgd, addr);
1991    if (!pud)
1992        return -ENOMEM;
1993    do {
1994        next = pud_addr_end(addr, end);
1995        err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1996        if (err)
1997            break;
1998    } while (pud++, addr = next, addr != end);
1999    return err;
2000}
2001
2002/*
2003 * Scan a region of virtual memory, filling in page tables as necessary
2004 * and calling a provided function on each leaf page table.
2005 */
2006int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
2007            unsigned long size, pte_fn_t fn, void *data)
2008{
2009    pgd_t *pgd;
2010    unsigned long next;
2011    unsigned long start = addr, end = addr + size;
2012    int err;
2013
2014    BUG_ON(addr >= end);
2015    mmu_notifier_invalidate_range_start(mm, start, end);
2016    pgd = pgd_offset(mm, addr);
2017    do {
2018        next = pgd_addr_end(addr, end);
2019        err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
2020        if (err)
2021            break;
2022    } while (pgd++, addr = next, addr != end);
2023    mmu_notifier_invalidate_range_end(mm, start, end);
2024    return err;
2025}
2026EXPORT_SYMBOL_GPL(apply_to_page_range);
2027
2028/*
2029 * handle_pte_fault chooses page fault handler according to an entry
2030 * which was read non-atomically. Before making any commitment, on
2031 * those architectures or configurations (e.g. i386 with PAE) which
2032 * might give a mix of unmatched parts, do_swap_page and do_file_page
2033 * must check under lock before unmapping the pte and proceeding
2034 * (but do_wp_page is only called after already making such a check;
2035 * and do_anonymous_page and do_no_page can safely check later on).
2036 */
2037static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
2038                pte_t *page_table, pte_t orig_pte)
2039{
2040    int same = 1;
2041#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
2042    if (sizeof(pte_t) > sizeof(unsigned long)) {
2043        spinlock_t *ptl = pte_lockptr(mm, pmd);
2044        spin_lock(ptl);
2045        same = pte_same(*page_table, orig_pte);
2046        spin_unlock(ptl);
2047    }
2048#endif
2049    pte_unmap(page_table);
2050    return same;
2051}
2052
2053/*
2054 * Do pte_mkwrite, but only if the vma says VM_WRITE. We do this when
2055 * servicing faults for write access. In the normal case, do always want
2056 * pte_mkwrite. But get_user_pages can cause write faults for mappings
2057 * that do not have writing enabled, when used by access_process_vm.
2058 */
2059static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
2060{
2061    if (likely(vma->vm_flags & VM_WRITE))
2062        pte = pte_mkwrite(pte);
2063    return pte;
2064}
2065
2066static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
2067{
2068    /*
2069     * If the source page was a PFN mapping, we don't have
2070     * a "struct page" for it. We do a best-effort copy by
2071     * just copying from the original user address. If that
2072     * fails, we just zero-fill it. Live with it.
2073     */
2074    if (unlikely(!src)) {
2075        void *kaddr = kmap_atomic(dst, KM_USER0);
2076        void __user *uaddr = (void __user *)(va & PAGE_MASK);
2077
2078        /*
2079         * This really shouldn't fail, because the page is there
2080         * in the page tables. But it might just be unreadable,
2081         * in which case we just give up and fill the result with
2082         * zeroes.
2083         */
2084        if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
2085            memset(kaddr, 0, PAGE_SIZE);
2086        kunmap_atomic(kaddr, KM_USER0);
2087        flush_dcache_page(dst);
2088    } else
2089        copy_user_highpage(dst, src, va, vma);
2090}
2091
2092/*
2093 * This routine handles present pages, when users try to write
2094 * to a shared page. It is done by copying the page to a new address
2095 * and decrementing the shared-page counter for the old page.
2096 *
2097 * Note that this routine assumes that the protection checks have been
2098 * done by the caller (the low-level page fault routine in most cases).
2099 * Thus we can safely just mark it writable once we've done any necessary
2100 * COW.
2101 *
2102 * We also mark the page dirty at this point even though the page will
2103 * change only once the write actually happens. This avoids a few races,
2104 * and potentially makes it more efficient.
2105 *
2106 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2107 * but allow concurrent faults), with pte both mapped and locked.
2108 * We return with mmap_sem still held, but pte unmapped and unlocked.
2109 */
2110static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2111        unsigned long address, pte_t *page_table, pmd_t *pmd,
2112        spinlock_t *ptl, pte_t orig_pte)
2113{
2114    struct page *old_page, *new_page;
2115    pte_t entry;
2116    int reuse = 0, ret = 0;
2117    int page_mkwrite = 0;
2118    struct page *dirty_page = NULL;
2119
2120    old_page = vm_normal_page(vma, address, orig_pte);
2121    if (!old_page) {
2122        /*
2123         * VM_MIXEDMAP !pfn_valid() case
2124         *
2125         * We should not cow pages in a shared writeable mapping.
2126         * Just mark the pages writable as we can't do any dirty
2127         * accounting on raw pfn maps.
2128         */
2129        if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2130                     (VM_WRITE|VM_SHARED))
2131            goto reuse;
2132        goto gotten;
2133    }
2134
2135    /*
2136     * Take out anonymous pages first, anonymous shared vmas are
2137     * not dirty accountable.
2138     */
2139    if (PageAnon(old_page) && !PageKsm(old_page)) {
2140        if (!trylock_page(old_page)) {
2141            page_cache_get(old_page);
2142            pte_unmap_unlock(page_table, ptl);
2143            lock_page(old_page);
2144            page_table = pte_offset_map_lock(mm, pmd, address,
2145                             &ptl);
2146            if (!pte_same(*page_table, orig_pte)) {
2147                unlock_page(old_page);
2148                page_cache_release(old_page);
2149                goto unlock;
2150            }
2151            page_cache_release(old_page);
2152        }
2153        reuse = reuse_swap_page(old_page);
2154        if (reuse)
2155            /*
2156             * The page is all ours. Move it to our anon_vma so
2157             * the rmap code will not search our parent or siblings.
2158             * Protected against the rmap code by the page lock.
2159             */
2160            page_move_anon_rmap(old_page, vma, address);
2161        unlock_page(old_page);
2162    } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2163                    (VM_WRITE|VM_SHARED))) {
2164        /*
2165         * Only catch write-faults on shared writable pages,
2166         * read-only shared pages can get COWed by
2167         * get_user_pages(.write=1, .force=1).
2168         */
2169        if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2170            struct vm_fault vmf;
2171            int tmp;
2172
2173            vmf.virtual_address = (void __user *)(address &
2174                                PAGE_MASK);
2175            vmf.pgoff = old_page->index;
2176            vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2177            vmf.page = old_page;
2178
2179            /*
2180             * Notify the address space that the page is about to
2181             * become writable so that it can prohibit this or wait
2182             * for the page to get into an appropriate state.
2183             *
2184             * We do this without the lock held, so that it can
2185             * sleep if it needs to.
2186             */
2187            page_cache_get(old_page);
2188            pte_unmap_unlock(page_table, ptl);
2189
2190            tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2191            if (unlikely(tmp &
2192                    (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2193                ret = tmp;
2194                goto unwritable_page;
2195            }
2196            if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2197                lock_page(old_page);
2198                if (!old_page->mapping) {
2199                    ret = 0; /* retry the fault */
2200                    unlock_page(old_page);
2201                    goto unwritable_page;
2202                }
2203            } else
2204                VM_BUG_ON(!PageLocked(old_page));
2205
2206            /*
2207             * Since we dropped the lock we need to revalidate
2208             * the PTE as someone else may have changed it. If
2209             * they did, we just return, as we can count on the
2210             * MMU to tell us if they didn't also make it writable.
2211             */
2212            page_table = pte_offset_map_lock(mm, pmd, address,
2213                             &ptl);
2214            if (!pte_same(*page_table, orig_pte)) {
2215                unlock_page(old_page);
2216                page_cache_release(old_page);
2217                goto unlock;
2218            }
2219
2220            page_mkwrite = 1;
2221        }
2222        dirty_page = old_page;
2223        get_page(dirty_page);
2224        reuse = 1;
2225    }
2226
2227    if (reuse) {
2228reuse:
2229        flush_cache_page(vma, address, pte_pfn(orig_pte));
2230        entry = pte_mkyoung(orig_pte);
2231        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2232        if (ptep_set_access_flags(vma, address, page_table, entry,1))
2233            update_mmu_cache(vma, address, page_table);
2234        ret |= VM_FAULT_WRITE;
2235        goto unlock;
2236    }
2237
2238    /*
2239     * Ok, we need to copy. Oh, well..
2240     */
2241    page_cache_get(old_page);
2242gotten:
2243    pte_unmap_unlock(page_table, ptl);
2244
2245    if (unlikely(anon_vma_prepare(vma)))
2246        goto oom;
2247
2248    if (is_zero_pfn(pte_pfn(orig_pte))) {
2249        new_page = alloc_zeroed_user_highpage_movable(vma, address);
2250        if (!new_page)
2251            goto oom;
2252    } else {
2253        new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2254        if (!new_page)
2255            goto oom;
2256        cow_user_page(new_page, old_page, address, vma);
2257    }
2258    __SetPageUptodate(new_page);
2259
2260    /*
2261     * Don't let another task, with possibly unlocked vma,
2262     * keep the mlocked page.
2263     */
2264    if ((vma->vm_flags & VM_LOCKED) && old_page) {
2265        lock_page(old_page); /* for LRU manipulation */
2266        clear_page_mlock(old_page);
2267        unlock_page(old_page);
2268    }
2269
2270    if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
2271        goto oom_free_new;
2272
2273    /*
2274     * Re-check the pte - we dropped the lock
2275     */
2276    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2277    if (likely(pte_same(*page_table, orig_pte))) {
2278        if (old_page) {
2279            if (!PageAnon(old_page)) {
2280                dec_mm_counter_fast(mm, MM_FILEPAGES);
2281                inc_mm_counter_fast(mm, MM_ANONPAGES);
2282            }
2283        } else
2284            inc_mm_counter_fast(mm, MM_ANONPAGES);
2285        flush_cache_page(vma, address, pte_pfn(orig_pte));
2286        entry = mk_pte(new_page, vma->vm_page_prot);
2287        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2288        /*
2289         * Clear the pte entry and flush it first, before updating the
2290         * pte with the new entry. This will avoid a race condition
2291         * seen in the presence of one thread doing SMC and another
2292         * thread doing COW.
2293         */
2294        ptep_clear_flush(vma, address, page_table);
2295        page_add_new_anon_rmap(new_page, vma, address);
2296        /*
2297         * We call the notify macro here because, when using secondary
2298         * mmu page tables (such as kvm shadow page tables), we want the
2299         * new page to be mapped directly into the secondary page table.
2300         */
2301        set_pte_at_notify(mm, address, page_table, entry);
2302        update_mmu_cache(vma, address, page_table);
2303        if (old_page) {
2304            /*
2305             * Only after switching the pte to the new page may
2306             * we remove the mapcount here. Otherwise another
2307             * process may come and find the rmap count decremented
2308             * before the pte is switched to the new page, and
2309             * "reuse" the old page writing into it while our pte
2310             * here still points into it and can be read by other
2311             * threads.
2312             *
2313             * The critical issue is to order this
2314             * page_remove_rmap with the ptp_clear_flush above.
2315             * Those stores are ordered by (if nothing else,)
2316             * the barrier present in the atomic_add_negative
2317             * in page_remove_rmap.
2318             *
2319             * Then the TLB flush in ptep_clear_flush ensures that
2320             * no process can access the old page before the
2321             * decremented mapcount is visible. And the old page
2322             * cannot be reused until after the decremented
2323             * mapcount is visible. So transitively, TLBs to
2324             * old page will be flushed before it can be reused.
2325             */
2326            page_remove_rmap(old_page);
2327        }
2328
2329        /* Free the old page.. */
2330        new_page = old_page;
2331        ret |= VM_FAULT_WRITE;
2332    } else
2333        mem_cgroup_uncharge_page(new_page);
2334
2335    if (new_page)
2336        page_cache_release(new_page);
2337    if (old_page)
2338        page_cache_release(old_page);
2339unlock:
2340    pte_unmap_unlock(page_table, ptl);
2341    if (dirty_page) {
2342        /*
2343         * Yes, Virginia, this is actually required to prevent a race
2344         * with clear_page_dirty_for_io() from clearing the page dirty
2345         * bit after it clear all dirty ptes, but before a racing
2346         * do_wp_page installs a dirty pte.
2347         *
2348         * do_no_page is protected similarly.
2349         */
2350        if (!page_mkwrite) {
2351            wait_on_page_locked(dirty_page);
2352            set_page_dirty_balance(dirty_page, page_mkwrite);
2353        }
2354        put_page(dirty_page);
2355        if (page_mkwrite) {
2356            struct address_space *mapping = dirty_page->mapping;
2357
2358            set_page_dirty(dirty_page);
2359            unlock_page(dirty_page);
2360            page_cache_release(dirty_page);
2361            if (mapping) {
2362                /*
2363                 * Some device drivers do not set page.mapping
2364                 * but still dirty their pages
2365                 */
2366                balance_dirty_pages_ratelimited(mapping);
2367            }
2368        }
2369
2370        /* file_update_time outside page_lock */
2371        if (vma->vm_file)
2372            file_update_time(vma->vm_file);
2373    }
2374    return ret;
2375oom_free_new:
2376    page_cache_release(new_page);
2377oom:
2378    if (old_page) {
2379        if (page_mkwrite) {
2380            unlock_page(old_page);
2381            page_cache_release(old_page);
2382        }
2383        page_cache_release(old_page);
2384    }
2385    return VM_FAULT_OOM;
2386
2387unwritable_page:
2388    page_cache_release(old_page);
2389    return ret;
2390}
2391
2392/*
2393 * Helper functions for unmap_mapping_range().
2394 *
2395 * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
2396 *
2397 * We have to restart searching the prio_tree whenever we drop the lock,
2398 * since the iterator is only valid while the lock is held, and anyway
2399 * a later vma might be split and reinserted earlier while lock dropped.
2400 *
2401 * The list of nonlinear vmas could be handled more efficiently, using
2402 * a placeholder, but handle it in the same way until a need is shown.
2403 * It is important to search the prio_tree before nonlinear list: a vma
2404 * may become nonlinear and be shifted from prio_tree to nonlinear list
2405 * while the lock is dropped; but never shifted from list to prio_tree.
2406 *
2407 * In order to make forward progress despite restarting the search,
2408 * vm_truncate_count is used to mark a vma as now dealt with, so we can
2409 * quickly skip it next time around. Since the prio_tree search only
2410 * shows us those vmas affected by unmapping the range in question, we
2411 * can't efficiently keep all vmas in step with mapping->truncate_count:
2412 * so instead reset them all whenever it wraps back to 0 (then go to 1).
2413 * mapping->truncate_count and vma->vm_truncate_count are protected by
2414 * i_mmap_lock.
2415 *
2416 * In order to make forward progress despite repeatedly restarting some
2417 * large vma, note the restart_addr from unmap_vmas when it breaks out:
2418 * and restart from that address when we reach that vma again. It might
2419 * have been split or merged, shrunk or extended, but never shifted: so
2420 * restart_addr remains valid so long as it remains in the vma's range.
2421 * unmap_mapping_range forces truncate_count to leap over page-aligned
2422 * values so we can save vma's restart_addr in its truncate_count field.
2423 */
2424#define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
2425
2426static void reset_vma_truncate_counts(struct address_space *mapping)
2427{
2428    struct vm_area_struct *vma;
2429    struct prio_tree_iter iter;
2430
2431    vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
2432        vma->vm_truncate_count = 0;
2433    list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
2434        vma->vm_truncate_count = 0;
2435}
2436
2437static int unmap_mapping_range_vma(struct vm_area_struct *vma,
2438        unsigned long start_addr, unsigned long end_addr,
2439        struct zap_details *details)
2440{
2441    unsigned long restart_addr;
2442    int need_break;
2443
2444    /*
2445     * files that support invalidating or truncating portions of the
2446     * file from under mmaped areas must have their ->fault function
2447     * return a locked page (and set VM_FAULT_LOCKED in the return).
2448     * This provides synchronisation against concurrent unmapping here.
2449     */
2450
2451again:
2452    restart_addr = vma->vm_truncate_count;
2453    if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
2454        start_addr = restart_addr;
2455        if (start_addr >= end_addr) {
2456            /* Top of vma has been split off since last time */
2457            vma->vm_truncate_count = details->truncate_count;
2458            return 0;
2459        }
2460    }
2461
2462    restart_addr = zap_page_range(vma, start_addr,
2463                    end_addr - start_addr, details);
2464    need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
2465
2466    if (restart_addr >= end_addr) {
2467        /* We have now completed this vma: mark it so */
2468        vma->vm_truncate_count = details->truncate_count;
2469        if (!need_break)
2470            return 0;
2471    } else {
2472        /* Note restart_addr in vma's truncate_count field */
2473        vma->vm_truncate_count = restart_addr;
2474        if (!need_break)
2475            goto again;
2476    }
2477
2478    spin_unlock(details->i_mmap_lock);
2479    cond_resched();
2480    spin_lock(details->i_mmap_lock);
2481    return -EINTR;
2482}
2483
2484static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
2485                        struct zap_details *details)
2486{
2487    struct vm_area_struct *vma;
2488    struct prio_tree_iter iter;
2489    pgoff_t vba, vea, zba, zea;
2490
2491restart:
2492    vma_prio_tree_foreach(vma, &iter, root,
2493            details->first_index, details->last_index) {
2494        /* Skip quickly over those we have already dealt with */
2495        if (vma->vm_truncate_count == details->truncate_count)
2496            continue;
2497
2498        vba = vma->vm_pgoff;
2499        vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2500        /* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2501        zba = details->first_index;
2502        if (zba < vba)
2503            zba = vba;
2504        zea = details->last_index;
2505        if (zea > vea)
2506            zea = vea;
2507
2508        if (unmap_mapping_range_vma(vma,
2509            ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2510            ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2511                details) < 0)
2512            goto restart;
2513    }
2514}
2515
2516static inline void unmap_mapping_range_list(struct list_head *head,
2517                        struct zap_details *details)
2518{
2519    struct vm_area_struct *vma;
2520
2521    /*
2522     * In nonlinear VMAs there is no correspondence between virtual address
2523     * offset and file offset. So we must perform an exhaustive search
2524     * across *all* the pages in each nonlinear VMA, not just the pages
2525     * whose virtual address lies outside the file truncation point.
2526     */
2527restart:
2528    list_for_each_entry(vma, head, shared.vm_set.list) {
2529        /* Skip quickly over those we have already dealt with */
2530        if (vma->vm_truncate_count == details->truncate_count)
2531            continue;
2532        details->nonlinear_vma = vma;
2533        if (unmap_mapping_range_vma(vma, vma->vm_start,
2534                    vma->vm_end, details) < 0)
2535            goto restart;
2536    }
2537}
2538
2539/**
2540 * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2541 * @mapping: the address space containing mmaps to be unmapped.
2542 * @holebegin: byte in first page to unmap, relative to the start of
2543 * the underlying file. This will be rounded down to a PAGE_SIZE
2544 * boundary. Note that this is different from truncate_pagecache(), which
2545 * must keep the partial page. In contrast, we must get rid of
2546 * partial pages.
2547 * @holelen: size of prospective hole in bytes. This will be rounded
2548 * up to a PAGE_SIZE boundary. A holelen of zero truncates to the
2549 * end of the file.
2550 * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2551 * but 0 when invalidating pagecache, don't throw away private data.
2552 */
2553void unmap_mapping_range(struct address_space *mapping,
2554        loff_t const holebegin, loff_t const holelen, int even_cows)
2555{
2556    struct zap_details details;
2557    pgoff_t hba = holebegin >> PAGE_SHIFT;
2558    pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2559
2560    /* Check for overflow. */
2561    if (sizeof(holelen) > sizeof(hlen)) {
2562        long long holeend =
2563            (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2564        if (holeend & ~(long long)ULONG_MAX)
2565            hlen = ULONG_MAX - hba + 1;
2566    }
2567
2568    details.check_mapping = even_cows? NULL: mapping;
2569    details.nonlinear_vma = NULL;
2570    details.first_index = hba;
2571    details.last_index = hba + hlen - 1;
2572    if (details.last_index < details.first_index)
2573        details.last_index = ULONG_MAX;
2574    details.i_mmap_lock = &mapping->i_mmap_lock;
2575
2576    spin_lock(&mapping->i_mmap_lock);
2577
2578    /* Protect against endless unmapping loops */
2579    mapping->truncate_count++;
2580    if (unlikely(is_restart_addr(mapping->truncate_count))) {
2581        if (mapping->truncate_count == 0)
2582            reset_vma_truncate_counts(mapping);
2583        mapping->truncate_count++;
2584    }
2585    details.truncate_count = mapping->truncate_count;
2586
2587    if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
2588        unmap_mapping_range_tree(&mapping->i_mmap, &details);
2589    if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2590        unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2591    spin_unlock(&mapping->i_mmap_lock);
2592}
2593EXPORT_SYMBOL(unmap_mapping_range);
2594
2595int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
2596{
2597    struct address_space *mapping = inode->i_mapping;
2598
2599    /*
2600     * If the underlying filesystem is not going to provide
2601     * a way to truncate a range of blocks (punch a hole) -
2602     * we should return failure right now.
2603     */
2604    if (!inode->i_op->truncate_range)
2605        return -ENOSYS;
2606
2607    mutex_lock(&inode->i_mutex);
2608    down_write(&inode->i_alloc_sem);
2609    unmap_mapping_range(mapping, offset, (end - offset), 1);
2610    truncate_inode_pages_range(mapping, offset, end);
2611    unmap_mapping_range(mapping, offset, (end - offset), 1);
2612    inode->i_op->truncate_range(inode, offset, end);
2613    up_write(&inode->i_alloc_sem);
2614    mutex_unlock(&inode->i_mutex);
2615
2616    return 0;
2617}
2618
2619/*
2620 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2621 * but allow concurrent faults), and pte mapped but not yet locked.
2622 * We return with mmap_sem still held, but pte unmapped and unlocked.
2623 */
2624static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2625        unsigned long address, pte_t *page_table, pmd_t *pmd,
2626        unsigned int flags, pte_t orig_pte)
2627{
2628    spinlock_t *ptl;
2629    struct page *page;
2630    swp_entry_t entry;
2631    pte_t pte;
2632    struct mem_cgroup *ptr = NULL;
2633    int ret = 0;
2634
2635    if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2636        goto out;
2637
2638    entry = pte_to_swp_entry(orig_pte);
2639    if (unlikely(non_swap_entry(entry))) {
2640        if (is_migration_entry(entry)) {
2641            migration_entry_wait(mm, pmd, address);
2642        } else if (is_hwpoison_entry(entry)) {
2643            ret = VM_FAULT_HWPOISON;
2644        } else {
2645            print_bad_pte(vma, address, orig_pte, NULL);
2646            ret = VM_FAULT_SIGBUS;
2647        }
2648        goto out;
2649    }
2650    delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2651    page = lookup_swap_cache(entry);
2652    if (!page) {
2653        grab_swap_token(mm); /* Contend for token _before_ read-in */
2654        page = swapin_readahead(entry,
2655                    GFP_HIGHUSER_MOVABLE, vma, address);
2656        if (!page) {
2657            /*
2658             * Back out if somebody else faulted in this pte
2659             * while we released the pte lock.
2660             */
2661            page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2662            if (likely(pte_same(*page_table, orig_pte)))
2663                ret = VM_FAULT_OOM;
2664            delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2665            goto unlock;
2666        }
2667
2668        /* Had to read the page from swap area: Major fault */
2669        ret = VM_FAULT_MAJOR;
2670        count_vm_event(PGMAJFAULT);
2671    } else if (PageHWPoison(page)) {
2672        /*
2673         * hwpoisoned dirty swapcache pages are kept for killing
2674         * owner processes (which may be unknown at hwpoison time)
2675         */
2676        ret = VM_FAULT_HWPOISON;
2677        delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2678        goto out_release;
2679    }
2680
2681    lock_page(page);
2682    delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2683
2684    page = ksm_might_need_to_copy(page, vma, address);
2685    if (!page) {
2686        ret = VM_FAULT_OOM;
2687        goto out;
2688    }
2689
2690    if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
2691        ret = VM_FAULT_OOM;
2692        goto out_page;
2693    }
2694
2695    /*
2696     * Back out if somebody else already faulted in this pte.
2697     */
2698    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2699    if (unlikely(!pte_same(*page_table, orig_pte)))
2700        goto out_nomap;
2701
2702    if (unlikely(!PageUptodate(page))) {
2703        ret = VM_FAULT_SIGBUS;
2704        goto out_nomap;
2705    }
2706
2707    /*
2708     * The page isn't present yet, go ahead with the fault.
2709     *
2710     * Be careful about the sequence of operations here.
2711     * To get its accounting right, reuse_swap_page() must be called
2712     * while the page is counted on swap but not yet in mapcount i.e.
2713     * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2714     * must be called after the swap_free(), or it will never succeed.
2715     * Because delete_from_swap_page() may be called by reuse_swap_page(),
2716     * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
2717     * in page->private. In this case, a record in swap_cgroup is silently
2718     * discarded at swap_free().
2719     */
2720
2721    inc_mm_counter_fast(mm, MM_ANONPAGES);
2722    dec_mm_counter_fast(mm, MM_SWAPENTS);
2723    pte = mk_pte(page, vma->vm_page_prot);
2724    if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
2725        pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2726        flags &= ~FAULT_FLAG_WRITE;
2727    }
2728    flush_icache_page(vma, page);
2729    set_pte_at(mm, address, page_table, pte);
2730    page_add_anon_rmap(page, vma, address);
2731    /* It's better to call commit-charge after rmap is established */
2732    mem_cgroup_commit_charge_swapin(page, ptr);
2733
2734    swap_free(entry);
2735    if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2736        try_to_free_swap(page);
2737    unlock_page(page);
2738
2739    if (flags & FAULT_FLAG_WRITE) {
2740        ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2741        if (ret & VM_FAULT_ERROR)
2742            ret &= VM_FAULT_ERROR;
2743        goto out;
2744    }
2745
2746    /* No need to invalidate - it was non-present before */
2747    update_mmu_cache(vma, address, page_table);
2748unlock:
2749    pte_unmap_unlock(page_table, ptl);
2750out:
2751    return ret;
2752out_nomap:
2753    mem_cgroup_cancel_charge_swapin(ptr);
2754    pte_unmap_unlock(page_table, ptl);
2755out_page:
2756    unlock_page(page);
2757out_release:
2758    page_cache_release(page);
2759    return ret;
2760}
2761
2762/*
2763 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2764 * but allow concurrent faults), and pte mapped but not yet locked.
2765 * We return with mmap_sem still held, but pte unmapped and unlocked.
2766 */
2767static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2768        unsigned long address, pte_t *page_table, pmd_t *pmd,
2769        unsigned int flags)
2770{
2771    struct page *page;
2772    spinlock_t *ptl;
2773    pte_t entry;
2774
2775    if (!(flags & FAULT_FLAG_WRITE)) {
2776        entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2777                        vma->vm_page_prot));
2778        ptl = pte_lockptr(mm, pmd);
2779        spin_lock(ptl);
2780        if (!pte_none(*page_table))
2781            goto unlock;
2782        goto setpte;
2783    }
2784
2785    /* Allocate our own private page. */
2786    pte_unmap(page_table);
2787
2788    if (unlikely(anon_vma_prepare(vma)))
2789        goto oom;
2790    page = alloc_zeroed_user_highpage_movable(vma, address);
2791    if (!page)
2792        goto oom;
2793    __SetPageUptodate(page);
2794
2795    if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
2796        goto oom_free_page;
2797
2798    entry = mk_pte(page, vma->vm_page_prot);
2799    if (vma->vm_flags & VM_WRITE)
2800        entry = pte_mkwrite(pte_mkdirty(entry));
2801
2802    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2803    if (!pte_none(*page_table))
2804        goto release;
2805
2806    inc_mm_counter_fast(mm, MM_ANONPAGES);
2807    page_add_new_anon_rmap(page, vma, address);
2808setpte:
2809    set_pte_at(mm, address, page_table, entry);
2810
2811    /* No need to invalidate - it was non-present before */
2812    update_mmu_cache(vma, address, page_table);
2813unlock:
2814    pte_unmap_unlock(page_table, ptl);
2815    return 0;
2816release:
2817    mem_cgroup_uncharge_page(page);
2818    page_cache_release(page);
2819    goto unlock;
2820oom_free_page:
2821    page_cache_release(page);
2822oom:
2823    return VM_FAULT_OOM;
2824}
2825
2826/*
2827 * __do_fault() tries to create a new page mapping. It aggressively
2828 * tries to share with existing pages, but makes a separate copy if
2829 * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
2830 * the next page fault.
2831 *
2832 * As this is called only for pages that do not currently exist, we
2833 * do not need to flush old virtual caches or the TLB.
2834 *
2835 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2836 * but allow concurrent faults), and pte neither mapped nor locked.
2837 * We return with mmap_sem still held, but pte unmapped and unlocked.
2838 */
2839static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2840        unsigned long address, pmd_t *pmd,
2841        pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2842{
2843    pte_t *page_table;
2844    spinlock_t *ptl;
2845    struct page *page;
2846    pte_t entry;
2847    int anon = 0;
2848    int charged = 0;
2849    struct page *dirty_page = NULL;
2850    struct vm_fault vmf;
2851    int ret;
2852    int page_mkwrite = 0;
2853
2854    vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2855    vmf.pgoff = pgoff;
2856    vmf.flags = flags;
2857    vmf.page = NULL;
2858
2859    ret = vma->vm_ops->fault(vma, &vmf);
2860    if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2861        return ret;
2862
2863    if (unlikely(PageHWPoison(vmf.page))) {
2864        if (ret & VM_FAULT_LOCKED)
2865            unlock_page(vmf.page);
2866        return VM_FAULT_HWPOISON;
2867    }
2868
2869    /*
2870     * For consistency in subsequent calls, make the faulted page always
2871     * locked.
2872     */
2873    if (unlikely(!(ret & VM_FAULT_LOCKED)))
2874        lock_page(vmf.page);
2875    else
2876        VM_BUG_ON(!PageLocked(vmf.page));
2877
2878    /*
2879     * Should we do an early C-O-W break?
2880     */
2881    page = vmf.page;
2882    if (flags & FAULT_FLAG_WRITE) {
2883        if (!(vma->vm_flags & VM_SHARED)) {
2884            anon = 1;
2885            if (unlikely(anon_vma_prepare(vma))) {
2886                ret = VM_FAULT_OOM;
2887                goto out;
2888            }
2889            page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
2890                        vma, address);
2891            if (!page) {
2892                ret = VM_FAULT_OOM;
2893                goto out;
2894            }
2895            if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
2896                ret = VM_FAULT_OOM;
2897                page_cache_release(page);
2898                goto out;
2899            }
2900            charged = 1;
2901            /*
2902             * Don't let another task, with possibly unlocked vma,
2903             * keep the mlocked page.
2904             */
2905            if (vma->vm_flags & VM_LOCKED)
2906                clear_page_mlock(vmf.page);
2907            copy_user_highpage(page, vmf.page, address, vma);
2908            __SetPageUptodate(page);
2909        } else {
2910            /*
2911             * If the page will be shareable, see if the backing
2912             * address space wants to know that the page is about
2913             * to become writable
2914             */
2915            if (vma->vm_ops->page_mkwrite) {
2916                int tmp;
2917
2918                unlock_page(page);
2919                vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2920                tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2921                if (unlikely(tmp &
2922                      (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2923                    ret = tmp;
2924                    goto unwritable_page;
2925                }
2926                if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2927                    lock_page(page);
2928                    if (!page->mapping) {
2929                        ret = 0; /* retry the fault */
2930                        unlock_page(page);
2931                        goto unwritable_page;
2932                    }
2933                } else
2934                    VM_BUG_ON(!PageLocked(page));
2935                page_mkwrite = 1;
2936            }
2937        }
2938
2939    }
2940
2941    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2942
2943    /*
2944     * This silly early PAGE_DIRTY setting removes a race
2945     * due to the bad i386 page protection. But it's valid
2946     * for other architectures too.
2947     *
2948     * Note that if FAULT_FLAG_WRITE is set, we either now have
2949     * an exclusive copy of the page, or this is a shared mapping,
2950     * so we can make it writable and dirty to avoid having to
2951     * handle that later.
2952     */
2953    /* Only go through if we didn't race with anybody else... */
2954    if (likely(pte_same(*page_table, orig_pte))) {
2955        flush_icache_page(vma, page);
2956        entry = mk_pte(page, vma->vm_page_prot);
2957        if (flags & FAULT_FLAG_WRITE)
2958            entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2959        if (anon) {
2960            inc_mm_counter_fast(mm, MM_ANONPAGES);
2961            page_add_new_anon_rmap(page, vma, address);
2962        } else {
2963            inc_mm_counter_fast(mm, MM_FILEPAGES);
2964            page_add_file_rmap(page);
2965            if (flags & FAULT_FLAG_WRITE) {
2966                dirty_page = page;
2967                get_page(dirty_page);
2968            }
2969        }
2970        set_pte_at(mm, address, page_table, entry);
2971
2972        /* no need to invalidate: a not-present page won't be cached */
2973        update_mmu_cache(vma, address, page_table);
2974    } else {
2975        if (charged)
2976            mem_cgroup_uncharge_page(page);
2977        if (anon)
2978            page_cache_release(page);
2979        else
2980            anon = 1; /* no anon but release faulted_page */
2981    }
2982
2983    pte_unmap_unlock(page_table, ptl);
2984
2985out:
2986    if (dirty_page) {
2987        struct address_space *mapping = page->mapping;
2988
2989        if (set_page_dirty(dirty_page))
2990            page_mkwrite = 1;
2991        unlock_page(dirty_page);
2992        put_page(dirty_page);
2993        if (page_mkwrite && mapping) {
2994            /*
2995             * Some device drivers do not set page.mapping but still
2996             * dirty their pages
2997             */
2998            balance_dirty_pages_ratelimited(mapping);
2999        }
3000
3001        /* file_update_time outside page_lock */
3002        if (vma->vm_file)
3003            file_update_time(vma->vm_file);
3004    } else {
3005        unlock_page(vmf.page);
3006        if (anon)
3007            page_cache_release(vmf.page);
3008    }
3009
3010    return ret;
3011
3012unwritable_page:
3013    page_cache_release(page);
3014    return ret;
3015}
3016
3017static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3018        unsigned long address, pte_t *page_table, pmd_t *pmd,
3019        unsigned int flags, pte_t orig_pte)
3020{
3021    pgoff_t pgoff = (((address & PAGE_MASK)
3022            - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
3023
3024    pte_unmap(page_table);
3025    return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3026}
3027
3028/*
3029 * Fault of a previously existing named mapping. Repopulate the pte
3030 * from the encoded file_pte if possible. This enables swappable
3031 * nonlinear vmas.
3032 *
3033 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3034 * but allow concurrent faults), and pte mapped but not yet locked.
3035 * We return with mmap_sem still held, but pte unmapped and unlocked.
3036 */
3037static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3038        unsigned long address, pte_t *page_table, pmd_t *pmd,
3039        unsigned int flags, pte_t orig_pte)
3040{
3041    pgoff_t pgoff;
3042
3043    flags |= FAULT_FLAG_NONLINEAR;
3044
3045    if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3046        return 0;
3047
3048    if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
3049        /*
3050         * Page table corrupted: show pte and kill process.
3051         */
3052        print_bad_pte(vma, address, orig_pte, NULL);
3053        return VM_FAULT_SIGBUS;
3054    }
3055
3056    pgoff = pte_to_pgoff(orig_pte);
3057    return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3058}
3059
3060/*
3061 * These routines also need to handle stuff like marking pages dirty
3062 * and/or accessed for architectures that don't do it in hardware (most
3063 * RISC architectures). The early dirtying is also good on the i386.
3064 *
3065 * There is also a hook called "update_mmu_cache()" that architectures
3066 * with external mmu caches can use to update those (ie the Sparc or
3067 * PowerPC hashed page tables that act as extended TLBs).
3068 *
3069 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3070 * but allow concurrent faults), and pte mapped but not yet locked.
3071 * We return with mmap_sem still held, but pte unmapped and unlocked.
3072 */
3073static inline int handle_pte_fault(struct mm_struct *mm,
3074        struct vm_area_struct *vma, unsigned long address,
3075        pte_t *pte, pmd_t *pmd, unsigned int flags)
3076{
3077    pte_t entry;
3078    spinlock_t *ptl;
3079
3080    entry = *pte;
3081    if (!pte_present(entry)) {
3082        if (pte_none(entry)) {
3083            if (vma->vm_ops) {
3084                if (likely(vma->vm_ops->fault))
3085                    return do_linear_fault(mm, vma, address,
3086                        pte, pmd, flags, entry);
3087            }
3088            return do_anonymous_page(mm, vma, address,
3089                         pte, pmd, flags);
3090        }
3091        if (pte_file(entry))
3092            return do_nonlinear_fault(mm, vma, address,
3093                    pte, pmd, flags, entry);
3094        return do_swap_page(mm, vma, address,
3095                    pte, pmd, flags, entry);
3096    }
3097
3098    ptl = pte_lockptr(mm, pmd);
3099    spin_lock(ptl);
3100    if (unlikely(!pte_same(*pte, entry)))
3101        goto unlock;
3102    if (flags & FAULT_FLAG_WRITE) {
3103        if (!pte_write(entry))
3104            return do_wp_page(mm, vma, address,
3105                    pte, pmd, ptl, entry);
3106        entry = pte_mkdirty(entry);
3107    }
3108    entry = pte_mkyoung(entry);
3109    if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3110        update_mmu_cache(vma, address, pte);
3111    } else {
3112        /*
3113         * This is needed only for protection faults but the arch code
3114         * is not yet telling us if this is a protection fault or not.
3115         * This still avoids useless tlb flushes for .text page faults
3116         * with threads.
3117         */
3118        if (flags & FAULT_FLAG_WRITE)
3119            flush_tlb_page(vma, address);
3120    }
3121unlock:
3122    pte_unmap_unlock(pte, ptl);
3123    return 0;
3124}
3125
3126/*
3127 * By the time we get here, we already hold the mm semaphore
3128 */
3129int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3130        unsigned long address, unsigned int flags)
3131{
3132    pgd_t *pgd;
3133    pud_t *pud;
3134    pmd_t *pmd;
3135    pte_t *pte;
3136
3137    __set_current_state(TASK_RUNNING);
3138
3139    count_vm_event(PGFAULT);
3140
3141    /* do counter updates before entering really critical section. */
3142    check_sync_rss_stat(current);
3143
3144    if (unlikely(is_vm_hugetlb_page(vma)))
3145        return hugetlb_fault(mm, vma, address, flags);
3146
3147    pgd = pgd_offset(mm, address);
3148    pud = pud_alloc(mm, pgd, address);
3149    if (!pud)
3150        return VM_FAULT_OOM;
3151    pmd = pmd_alloc(mm, pud, address);
3152    if (!pmd)
3153        return VM_FAULT_OOM;
3154    pte = pte_alloc_map(mm, pmd, address);
3155    if (!pte)
3156        return VM_FAULT_OOM;
3157
3158    return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3159}
3160
3161#ifndef __PAGETABLE_PUD_FOLDED
3162/*
3163 * Allocate page upper directory.
3164 * We've already handled the fast-path in-line.
3165 */
3166int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3167{
3168    pud_t *new = pud_alloc_one(mm, address);
3169    if (!new)
3170        return -ENOMEM;
3171
3172    smp_wmb(); /* See comment in __pte_alloc */
3173
3174    spin_lock(&mm->page_table_lock);
3175    if (pgd_present(*pgd)) /* Another has populated it */
3176        pud_free(mm, new);
3177    else
3178        pgd_populate(mm, pgd, new);
3179    spin_unlock(&mm->page_table_lock);
3180    return 0;
3181}
3182#endif /* __PAGETABLE_PUD_FOLDED */
3183
3184#ifndef __PAGETABLE_PMD_FOLDED
3185/*
3186 * Allocate page middle directory.
3187 * We've already handled the fast-path in-line.
3188 */
3189int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3190{
3191    pmd_t *new = pmd_alloc_one(mm, address);
3192    if (!new)
3193        return -ENOMEM;
3194
3195    smp_wmb(); /* See comment in __pte_alloc */
3196
3197    spin_lock(&mm->page_table_lock);
3198#ifndef __ARCH_HAS_4LEVEL_HACK
3199    if (pud_present(*pud)) /* Another has populated it */
3200        pmd_free(mm, new);
3201    else
3202        pud_populate(mm, pud, new);
3203#else
3204    if (pgd_present(*pud)) /* Another has populated it */
3205        pmd_free(mm, new);
3206    else
3207        pgd_populate(mm, pud, new);
3208#endif /* __ARCH_HAS_4LEVEL_HACK */
3209    spin_unlock(&mm->page_table_lock);
3210    return 0;
3211}
3212#endif /* __PAGETABLE_PMD_FOLDED */
3213
3214int make_pages_present(unsigned long addr, unsigned long end)
3215{
3216    int ret, len, write;
3217    struct vm_area_struct * vma;
3218
3219    vma = find_vma(current->mm, addr);
3220    if (!vma)
3221        return -ENOMEM;
3222    write = (vma->vm_flags & VM_WRITE) != 0;
3223    BUG_ON(addr >= end);
3224    BUG_ON(end > vma->vm_end);
3225    len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
3226    ret = get_user_pages(current, current->mm, addr,
3227            len, write, 0, NULL, NULL);
3228    if (ret < 0)
3229        return ret;
3230    return ret == len ? 0 : -EFAULT;
3231}
3232
3233#if !defined(__HAVE_ARCH_GATE_AREA)
3234
3235#if defined(AT_SYSINFO_EHDR)
3236static struct vm_area_struct gate_vma;
3237
3238static int __init gate_vma_init(void)
3239{
3240    gate_vma.vm_mm = NULL;
3241    gate_vma.vm_start = FIXADDR_USER_START;
3242    gate_vma.vm_end = FIXADDR_USER_END;
3243    gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
3244    gate_vma.vm_page_prot = __P101;
3245    /*
3246     * Make sure the vDSO gets into every core dump.
3247     * Dumping its contents makes post-mortem fully interpretable later
3248     * without matching up the same kernel and hardware config to see
3249     * what PC values meant.
3250     */
3251    gate_vma.vm_flags |= VM_ALWAYSDUMP;
3252    return 0;
3253}
3254__initcall(gate_vma_init);
3255#endif
3256
3257struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
3258{
3259#ifdef AT_SYSINFO_EHDR
3260    return &gate_vma;
3261#else
3262    return NULL;
3263#endif
3264}
3265
3266int in_gate_area_no_task(unsigned long addr)
3267{
3268#ifdef AT_SYSINFO_EHDR
3269    if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
3270        return 1;
3271#endif
3272    return 0;
3273}
3274
3275#endif /* __HAVE_ARCH_GATE_AREA */
3276
3277static int follow_pte(struct mm_struct *mm, unsigned long address,
3278        pte_t **ptepp, spinlock_t **ptlp)
3279{
3280    pgd_t *pgd;
3281    pud_t *pud;
3282    pmd_t *pmd;
3283    pte_t *ptep;
3284
3285    pgd = pgd_offset(mm, address);
3286    if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3287        goto out;
3288
3289    pud = pud_offset(pgd, address);
3290    if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3291        goto out;
3292
3293    pmd = pmd_offset(pud, address);
3294    if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3295        goto out;
3296
3297    /* We cannot handle huge page PFN maps. Luckily they don't exist. */
3298    if (pmd_huge(*pmd))
3299        goto out;
3300
3301    ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3302    if (!ptep)
3303        goto out;
3304    if (!pte_present(*ptep))
3305        goto unlock;
3306    *ptepp = ptep;
3307    return 0;
3308unlock:
3309    pte_unmap_unlock(ptep, *ptlp);
3310out:
3311    return -EINVAL;
3312}
3313
3314/**
3315 * follow_pfn - look up PFN at a user virtual address
3316 * @vma: memory mapping
3317 * @address: user virtual address
3318 * @pfn: location to store found PFN
3319 *
3320 * Only IO mappings and raw PFN mappings are allowed.
3321 *
3322 * Returns zero and the pfn at @pfn on success, -ve otherwise.
3323 */
3324int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3325    unsigned long *pfn)
3326{
3327    int ret = -EINVAL;
3328    spinlock_t *ptl;
3329    pte_t *ptep;
3330
3331    if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3332        return ret;
3333
3334    ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3335    if (ret)
3336        return ret;
3337    *pfn = pte_pfn(*ptep);
3338    pte_unmap_unlock(ptep, ptl);
3339    return 0;
3340}
3341EXPORT_SYMBOL(follow_pfn);
3342
3343#ifdef CONFIG_HAVE_IOREMAP_PROT
3344int follow_phys(struct vm_area_struct *vma,
3345        unsigned long address, unsigned int flags,
3346        unsigned long *prot, resource_size_t *phys)
3347{
3348    int ret = -EINVAL;
3349    pte_t *ptep, pte;
3350    spinlock_t *ptl;
3351
3352    if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3353        goto out;
3354
3355    if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3356        goto out;
3357    pte = *ptep;
3358
3359    if ((flags & FOLL_WRITE) && !pte_write(pte))
3360        goto unlock;
3361
3362    *prot = pgprot_val(pte_pgprot(pte));
3363    *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3364
3365    ret = 0;
3366unlock:
3367    pte_unmap_unlock(ptep, ptl);
3368out:
3369    return ret;
3370}
3371
3372int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3373            void *buf, int len, int write)
3374{
3375    resource_size_t phys_addr;
3376    unsigned long prot = 0;
3377    void __iomem *maddr;
3378    int offset = addr & (PAGE_SIZE-1);
3379
3380    if (follow_phys(vma, addr, write, &prot, &phys_addr))
3381        return -EINVAL;
3382
3383    maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
3384    if (write)
3385        memcpy_toio(maddr + offset, buf, len);
3386    else
3387        memcpy_fromio(buf, maddr + offset, len);
3388    iounmap(maddr);
3389
3390    return len;
3391}
3392#endif
3393
3394/*
3395 * Access another process' address space.
3396 * Source/target buffer must be kernel space,
3397 * Do not walk the page table directly, use get_user_pages
3398 */
3399int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
3400{
3401    struct mm_struct *mm;
3402    struct vm_area_struct *vma;
3403    void *old_buf = buf;
3404
3405    mm = get_task_mm(tsk);
3406    if (!mm)
3407        return 0;
3408
3409    down_read(&mm->mmap_sem);
3410    /* ignore errors, just check how much was successfully transferred */
3411    while (len) {
3412        int bytes, ret, offset;
3413        void *maddr;
3414        struct page *page = NULL;
3415
3416        ret = get_user_pages(tsk, mm, addr, 1,
3417                write, 1, &page, &vma);
3418        if (ret <= 0) {
3419            /*
3420             * Check if this is a VM_IO | VM_PFNMAP VMA, which
3421             * we can access using slightly different code.
3422             */
3423#ifdef CONFIG_HAVE_IOREMAP_PROT
3424            vma = find_vma(mm, addr);
3425            if (!vma)
3426                break;
3427            if (vma->vm_ops && vma->vm_ops->access)
3428                ret = vma->vm_ops->access(vma, addr, buf,
3429                              len, write);
3430            if (ret <= 0)
3431#endif
3432                break;
3433            bytes = ret;
3434        } else {
3435            bytes = len;
3436            offset = addr & (PAGE_SIZE-1);
3437            if (bytes > PAGE_SIZE-offset)
3438                bytes = PAGE_SIZE-offset;
3439
3440            maddr = kmap(page);
3441            if (write) {
3442                copy_to_user_page(vma, page, addr,
3443                          maddr + offset, buf, bytes);
3444                set_page_dirty_lock(page);
3445            } else {
3446                copy_from_user_page(vma, page, addr,
3447                            buf, maddr + offset, bytes);
3448            }
3449            kunmap(page);
3450            page_cache_release(page);
3451        }
3452        len -= bytes;
3453        buf += bytes;
3454        addr += bytes;
3455    }
3456    up_read(&mm->mmap_sem);
3457    mmput(mm);
3458
3459    return buf - old_buf;
3460}
3461
3462/*
3463 * Print the name of a VMA.
3464 */
3465void print_vma_addr(char *prefix, unsigned long ip)
3466{
3467    struct mm_struct *mm = current->mm;
3468    struct vm_area_struct *vma;
3469
3470    /*
3471     * Do not print if we are in atomic
3472     * contexts (in exception stacks, etc.):
3473     */
3474    if (preempt_count())
3475        return;
3476
3477    down_read(&mm->mmap_sem);
3478    vma = find_vma(mm, ip);
3479    if (vma && vma->vm_file) {
3480        struct file *f = vma->vm_file;
3481        char *buf = (char *)__get_free_page(GFP_KERNEL);
3482        if (buf) {
3483            char *p, *s;
3484
3485            p = d_path(&f->f_path, buf, PAGE_SIZE);
3486            if (IS_ERR(p))
3487                p = "?";
3488            s = strrchr(p, '/');
3489            if (s)
3490                p = s+1;
3491            printk("%s%s[%lx+%lx]", prefix, p,
3492                    vma->vm_start,
3493                    vma->vm_end - vma->vm_start);
3494            free_page((unsigned long)buf);
3495        }
3496    }
3497    up_read(&current->mm->mmap_sem);
3498}
3499
3500#ifdef CONFIG_PROVE_LOCKING
3501void might_fault(void)
3502{
3503    /*
3504     * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3505     * holding the mmap_sem, this is safe because kernel memory doesn't
3506     * get paged out, therefore we'll never actually fault, and the
3507     * below annotations will generate false positives.
3508     */
3509    if (segment_eq(get_fs(), KERNEL_DS))
3510        return;
3511
3512    might_sleep();
3513    /*
3514     * it would be nicer only to annotate paths which are not under
3515     * pagefault_disable, however that requires a larger audit and
3516     * providing helpers like get_user_atomic.
3517     */
3518    if (!in_atomic() && current->mm)
3519        might_lock_read(&current->mm->mmap_sem);
3520}
3521EXPORT_SYMBOL(might_fault);
3522#endif
3523

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