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/export.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#include <linux/migrate.h>
61#include <linux/string.h>
62
63#include <asm/io.h>
64#include <asm/pgalloc.h>
65#include <asm/uaccess.h>
66#include <asm/tlb.h>
67#include <asm/tlbflush.h>
68#include <asm/pgtable.h>
69
70#include "internal.h"
71
72#ifdef LAST_NID_NOT_IN_PAGE_FLAGS
73#warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_nid.
74#endif
75
76#ifndef CONFIG_NEED_MULTIPLE_NODES
77/* use the per-pgdat data instead for discontigmem - mbligh */
78unsigned long max_mapnr;
79struct page *mem_map;
80
81EXPORT_SYMBOL(max_mapnr);
82EXPORT_SYMBOL(mem_map);
83#endif
84
85unsigned long num_physpages;
86/*
87 * A number of key systems in x86 including ioremap() rely on the assumption
88 * that high_memory defines the upper bound on direct map memory, then end
89 * of ZONE_NORMAL. Under CONFIG_DISCONTIG this means that max_low_pfn and
90 * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
91 * and ZONE_HIGHMEM.
92 */
93void * high_memory;
94
95EXPORT_SYMBOL(num_physpages);
96EXPORT_SYMBOL(high_memory);
97
98/*
99 * Randomize the address space (stacks, mmaps, brk, etc.).
100 *
101 * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
102 * as ancient (libc5 based) binaries can segfault. )
103 */
104int randomize_va_space __read_mostly =
105#ifdef CONFIG_COMPAT_BRK
106                    1;
107#else
108                    2;
109#endif
110
111static int __init disable_randmaps(char *s)
112{
113    randomize_va_space = 0;
114    return 1;
115}
116__setup("norandmaps", disable_randmaps);
117
118unsigned long zero_pfn __read_mostly;
119unsigned long highest_memmap_pfn __read_mostly;
120
121/*
122 * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
123 */
124static int __init init_zero_pfn(void)
125{
126    zero_pfn = page_to_pfn(ZERO_PAGE(0));
127    return 0;
128}
129core_initcall(init_zero_pfn);
130
131
132#if defined(SPLIT_RSS_COUNTING)
133
134void sync_mm_rss(struct mm_struct *mm)
135{
136    int i;
137
138    for (i = 0; i < NR_MM_COUNTERS; i++) {
139        if (current->rss_stat.count[i]) {
140            add_mm_counter(mm, i, current->rss_stat.count[i]);
141            current->rss_stat.count[i] = 0;
142        }
143    }
144    current->rss_stat.events = 0;
145}
146
147static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
148{
149    struct task_struct *task = current;
150
151    if (likely(task->mm == mm))
152        task->rss_stat.count[member] += val;
153    else
154        add_mm_counter(mm, member, val);
155}
156#define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
157#define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
158
159/* sync counter once per 64 page faults */
160#define TASK_RSS_EVENTS_THRESH (64)
161static void check_sync_rss_stat(struct task_struct *task)
162{
163    if (unlikely(task != current))
164        return;
165    if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
166        sync_mm_rss(task->mm);
167}
168#else /* SPLIT_RSS_COUNTING */
169
170#define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
171#define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
172
173static void check_sync_rss_stat(struct task_struct *task)
174{
175}
176
177#endif /* SPLIT_RSS_COUNTING */
178
179#ifdef HAVE_GENERIC_MMU_GATHER
180
181static int tlb_next_batch(struct mmu_gather *tlb)
182{
183    struct mmu_gather_batch *batch;
184
185    batch = tlb->active;
186    if (batch->next) {
187        tlb->active = batch->next;
188        return 1;
189    }
190
191    if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
192        return 0;
193
194    batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
195    if (!batch)
196        return 0;
197
198    tlb->batch_count++;
199    batch->next = NULL;
200    batch->nr = 0;
201    batch->max = MAX_GATHER_BATCH;
202
203    tlb->active->next = batch;
204    tlb->active = batch;
205
206    return 1;
207}
208
209/* tlb_gather_mmu
210 * Called to initialize an (on-stack) mmu_gather structure for page-table
211 * tear-down from @mm. The @fullmm argument is used when @mm is without
212 * users and we're going to destroy the full address space (exit/execve).
213 */
214void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
215{
216    tlb->mm = mm;
217
218    tlb->fullmm = fullmm;
219    tlb->need_flush_all = 0;
220    tlb->start = -1UL;
221    tlb->end = 0;
222    tlb->need_flush = 0;
223    tlb->fast_mode = (num_possible_cpus() == 1);
224    tlb->local.next = NULL;
225    tlb->local.nr = 0;
226    tlb->local.max = ARRAY_SIZE(tlb->__pages);
227    tlb->active = &tlb->local;
228    tlb->batch_count = 0;
229
230#ifdef CONFIG_HAVE_RCU_TABLE_FREE
231    tlb->batch = NULL;
232#endif
233}
234
235void tlb_flush_mmu(struct mmu_gather *tlb)
236{
237    struct mmu_gather_batch *batch;
238
239    if (!tlb->need_flush)
240        return;
241    tlb->need_flush = 0;
242    tlb_flush(tlb);
243#ifdef CONFIG_HAVE_RCU_TABLE_FREE
244    tlb_table_flush(tlb);
245#endif
246
247    if (tlb_fast_mode(tlb))
248        return;
249
250    for (batch = &tlb->local; batch; batch = batch->next) {
251        free_pages_and_swap_cache(batch->pages, batch->nr);
252        batch->nr = 0;
253    }
254    tlb->active = &tlb->local;
255}
256
257/* tlb_finish_mmu
258 * Called at the end of the shootdown operation to free up any resources
259 * that were required.
260 */
261void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
262{
263    struct mmu_gather_batch *batch, *next;
264
265    tlb->start = start;
266    tlb->end = end;
267    tlb_flush_mmu(tlb);
268
269    /* keep the page table cache within bounds */
270    check_pgt_cache();
271
272    for (batch = tlb->local.next; batch; batch = next) {
273        next = batch->next;
274        free_pages((unsigned long)batch, 0);
275    }
276    tlb->local.next = NULL;
277}
278
279/* __tlb_remove_page
280 * Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
281 * handling the additional races in SMP caused by other CPUs caching valid
282 * mappings in their TLBs. Returns the number of free page slots left.
283 * When out of page slots we must call tlb_flush_mmu().
284 */
285int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
286{
287    struct mmu_gather_batch *batch;
288
289    VM_BUG_ON(!tlb->need_flush);
290
291    if (tlb_fast_mode(tlb)) {
292        free_page_and_swap_cache(page);
293        return 1; /* avoid calling tlb_flush_mmu() */
294    }
295
296    batch = tlb->active;
297    batch->pages[batch->nr++] = page;
298    if (batch->nr == batch->max) {
299        if (!tlb_next_batch(tlb))
300            return 0;
301        batch = tlb->active;
302    }
303    VM_BUG_ON(batch->nr > batch->max);
304
305    return batch->max - batch->nr;
306}
307
308#endif /* HAVE_GENERIC_MMU_GATHER */
309
310#ifdef CONFIG_HAVE_RCU_TABLE_FREE
311
312/*
313 * See the comment near struct mmu_table_batch.
314 */
315
316static void tlb_remove_table_smp_sync(void *arg)
317{
318    /* Simply deliver the interrupt */
319}
320
321static void tlb_remove_table_one(void *table)
322{
323    /*
324     * This isn't an RCU grace period and hence the page-tables cannot be
325     * assumed to be actually RCU-freed.
326     *
327     * It is however sufficient for software page-table walkers that rely on
328     * IRQ disabling. See the comment near struct mmu_table_batch.
329     */
330    smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
331    __tlb_remove_table(table);
332}
333
334static void tlb_remove_table_rcu(struct rcu_head *head)
335{
336    struct mmu_table_batch *batch;
337    int i;
338
339    batch = container_of(head, struct mmu_table_batch, rcu);
340
341    for (i = 0; i < batch->nr; i++)
342        __tlb_remove_table(batch->tables[i]);
343
344    free_page((unsigned long)batch);
345}
346
347void tlb_table_flush(struct mmu_gather *tlb)
348{
349    struct mmu_table_batch **batch = &tlb->batch;
350
351    if (*batch) {
352        call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
353        *batch = NULL;
354    }
355}
356
357void tlb_remove_table(struct mmu_gather *tlb, void *table)
358{
359    struct mmu_table_batch **batch = &tlb->batch;
360
361    tlb->need_flush = 1;
362
363    /*
364     * When there's less then two users of this mm there cannot be a
365     * concurrent page-table walk.
366     */
367    if (atomic_read(&tlb->mm->mm_users) < 2) {
368        __tlb_remove_table(table);
369        return;
370    }
371
372    if (*batch == NULL) {
373        *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
374        if (*batch == NULL) {
375            tlb_remove_table_one(table);
376            return;
377        }
378        (*batch)->nr = 0;
379    }
380    (*batch)->tables[(*batch)->nr++] = table;
381    if ((*batch)->nr == MAX_TABLE_BATCH)
382        tlb_table_flush(tlb);
383}
384
385#endif /* CONFIG_HAVE_RCU_TABLE_FREE */
386
387/*
388 * If a p?d_bad entry is found while walking page tables, report
389 * the error, before resetting entry to p?d_none. Usually (but
390 * very seldom) called out from the p?d_none_or_clear_bad macros.
391 */
392
393void pgd_clear_bad(pgd_t *pgd)
394{
395    pgd_ERROR(*pgd);
396    pgd_clear(pgd);
397}
398
399void pud_clear_bad(pud_t *pud)
400{
401    pud_ERROR(*pud);
402    pud_clear(pud);
403}
404
405void pmd_clear_bad(pmd_t *pmd)
406{
407    pmd_ERROR(*pmd);
408    pmd_clear(pmd);
409}
410
411/*
412 * Note: this doesn't free the actual pages themselves. That
413 * has been handled earlier when unmapping all the memory regions.
414 */
415static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
416               unsigned long addr)
417{
418    pgtable_t token = pmd_pgtable(*pmd);
419    pmd_clear(pmd);
420    pte_free_tlb(tlb, token, addr);
421    tlb->mm->nr_ptes--;
422}
423
424static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
425                unsigned long addr, unsigned long end,
426                unsigned long floor, unsigned long ceiling)
427{
428    pmd_t *pmd;
429    unsigned long next;
430    unsigned long start;
431
432    start = addr;
433    pmd = pmd_offset(pud, addr);
434    do {
435        next = pmd_addr_end(addr, end);
436        if (pmd_none_or_clear_bad(pmd))
437            continue;
438        free_pte_range(tlb, pmd, addr);
439    } while (pmd++, addr = next, addr != end);
440
441    start &= PUD_MASK;
442    if (start < floor)
443        return;
444    if (ceiling) {
445        ceiling &= PUD_MASK;
446        if (!ceiling)
447            return;
448    }
449    if (end - 1 > ceiling - 1)
450        return;
451
452    pmd = pmd_offset(pud, start);
453    pud_clear(pud);
454    pmd_free_tlb(tlb, pmd, start);
455}
456
457static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
458                unsigned long addr, unsigned long end,
459                unsigned long floor, unsigned long ceiling)
460{
461    pud_t *pud;
462    unsigned long next;
463    unsigned long start;
464
465    start = addr;
466    pud = pud_offset(pgd, addr);
467    do {
468        next = pud_addr_end(addr, end);
469        if (pud_none_or_clear_bad(pud))
470            continue;
471        free_pmd_range(tlb, pud, addr, next, floor, ceiling);
472    } while (pud++, addr = next, addr != end);
473
474    start &= PGDIR_MASK;
475    if (start < floor)
476        return;
477    if (ceiling) {
478        ceiling &= PGDIR_MASK;
479        if (!ceiling)
480            return;
481    }
482    if (end - 1 > ceiling - 1)
483        return;
484
485    pud = pud_offset(pgd, start);
486    pgd_clear(pgd);
487    pud_free_tlb(tlb, pud, start);
488}
489
490/*
491 * This function frees user-level page tables of a process.
492 *
493 * Must be called with pagetable lock held.
494 */
495void free_pgd_range(struct mmu_gather *tlb,
496            unsigned long addr, unsigned long end,
497            unsigned long floor, unsigned long ceiling)
498{
499    pgd_t *pgd;
500    unsigned long next;
501
502    /*
503     * The next few lines have given us lots of grief...
504     *
505     * Why are we testing PMD* at this top level? Because often
506     * there will be no work to do at all, and we'd prefer not to
507     * go all the way down to the bottom just to discover that.
508     *
509     * Why all these "- 1"s? Because 0 represents both the bottom
510     * of the address space and the top of it (using -1 for the
511     * top wouldn't help much: the masks would do the wrong thing).
512     * The rule is that addr 0 and floor 0 refer to the bottom of
513     * the address space, but end 0 and ceiling 0 refer to the top
514     * Comparisons need to use "end - 1" and "ceiling - 1" (though
515     * that end 0 case should be mythical).
516     *
517     * Wherever addr is brought up or ceiling brought down, we must
518     * be careful to reject "the opposite 0" before it confuses the
519     * subsequent tests. But what about where end is brought down
520     * by PMD_SIZE below? no, end can't go down to 0 there.
521     *
522     * Whereas we round start (addr) and ceiling down, by different
523     * masks at different levels, in order to test whether a table
524     * now has no other vmas using it, so can be freed, we don't
525     * bother to round floor or end up - the tests don't need that.
526     */
527
528    addr &= PMD_MASK;
529    if (addr < floor) {
530        addr += PMD_SIZE;
531        if (!addr)
532            return;
533    }
534    if (ceiling) {
535        ceiling &= PMD_MASK;
536        if (!ceiling)
537            return;
538    }
539    if (end - 1 > ceiling - 1)
540        end -= PMD_SIZE;
541    if (addr > end - 1)
542        return;
543
544    pgd = pgd_offset(tlb->mm, addr);
545    do {
546        next = pgd_addr_end(addr, end);
547        if (pgd_none_or_clear_bad(pgd))
548            continue;
549        free_pud_range(tlb, pgd, addr, next, floor, ceiling);
550    } while (pgd++, addr = next, addr != end);
551}
552
553void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
554        unsigned long floor, unsigned long ceiling)
555{
556    while (vma) {
557        struct vm_area_struct *next = vma->vm_next;
558        unsigned long addr = vma->vm_start;
559
560        /*
561         * Hide vma from rmap and truncate_pagecache before freeing
562         * pgtables
563         */
564        unlink_anon_vmas(vma);
565        unlink_file_vma(vma);
566
567        if (is_vm_hugetlb_page(vma)) {
568            hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
569                floor, next? next->vm_start: ceiling);
570        } else {
571            /*
572             * Optimization: gather nearby vmas into one call down
573             */
574            while (next && next->vm_start <= vma->vm_end + PMD_SIZE
575                   && !is_vm_hugetlb_page(next)) {
576                vma = next;
577                next = vma->vm_next;
578                unlink_anon_vmas(vma);
579                unlink_file_vma(vma);
580            }
581            free_pgd_range(tlb, addr, vma->vm_end,
582                floor, next? next->vm_start: ceiling);
583        }
584        vma = next;
585    }
586}
587
588int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
589        pmd_t *pmd, unsigned long address)
590{
591    pgtable_t new = pte_alloc_one(mm, address);
592    int wait_split_huge_page;
593    if (!new)
594        return -ENOMEM;
595
596    /*
597     * Ensure all pte setup (eg. pte page lock and page clearing) are
598     * visible before the pte is made visible to other CPUs by being
599     * put into page tables.
600     *
601     * The other side of the story is the pointer chasing in the page
602     * table walking code (when walking the page table without locking;
603     * ie. most of the time). Fortunately, these data accesses consist
604     * of a chain of data-dependent loads, meaning most CPUs (alpha
605     * being the notable exception) will already guarantee loads are
606     * seen in-order. See the alpha page table accessors for the
607     * smp_read_barrier_depends() barriers in page table walking code.
608     */
609    smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
610
611    spin_lock(&mm->page_table_lock);
612    wait_split_huge_page = 0;
613    if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
614        mm->nr_ptes++;
615        pmd_populate(mm, pmd, new);
616        new = NULL;
617    } else if (unlikely(pmd_trans_splitting(*pmd)))
618        wait_split_huge_page = 1;
619    spin_unlock(&mm->page_table_lock);
620    if (new)
621        pte_free(mm, new);
622    if (wait_split_huge_page)
623        wait_split_huge_page(vma->anon_vma, pmd);
624    return 0;
625}
626
627int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
628{
629    pte_t *new = pte_alloc_one_kernel(&init_mm, address);
630    if (!new)
631        return -ENOMEM;
632
633    smp_wmb(); /* See comment in __pte_alloc */
634
635    spin_lock(&init_mm.page_table_lock);
636    if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
637        pmd_populate_kernel(&init_mm, pmd, new);
638        new = NULL;
639    } else
640        VM_BUG_ON(pmd_trans_splitting(*pmd));
641    spin_unlock(&init_mm.page_table_lock);
642    if (new)
643        pte_free_kernel(&init_mm, new);
644    return 0;
645}
646
647static inline void init_rss_vec(int *rss)
648{
649    memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
650}
651
652static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
653{
654    int i;
655
656    if (current->mm == mm)
657        sync_mm_rss(mm);
658    for (i = 0; i < NR_MM_COUNTERS; i++)
659        if (rss[i])
660            add_mm_counter(mm, i, rss[i]);
661}
662
663/*
664 * This function is called to print an error when a bad pte
665 * is found. For example, we might have a PFN-mapped pte in
666 * a region that doesn't allow it.
667 *
668 * The calling function must still handle the error.
669 */
670static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
671              pte_t pte, struct page *page)
672{
673    pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
674    pud_t *pud = pud_offset(pgd, addr);
675    pmd_t *pmd = pmd_offset(pud, addr);
676    struct address_space *mapping;
677    pgoff_t index;
678    static unsigned long resume;
679    static unsigned long nr_shown;
680    static unsigned long nr_unshown;
681
682    /*
683     * Allow a burst of 60 reports, then keep quiet for that minute;
684     * or allow a steady drip of one report per second.
685     */
686    if (nr_shown == 60) {
687        if (time_before(jiffies, resume)) {
688            nr_unshown++;
689            return;
690        }
691        if (nr_unshown) {
692            printk(KERN_ALERT
693                "BUG: Bad page map: %lu messages suppressed\n",
694                nr_unshown);
695            nr_unshown = 0;
696        }
697        nr_shown = 0;
698    }
699    if (nr_shown++ == 0)
700        resume = jiffies + 60 * HZ;
701
702    mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
703    index = linear_page_index(vma, addr);
704
705    printk(KERN_ALERT
706        "BUG: Bad page map in process %s pte:%08llx pmd:%08llx\n",
707        current->comm,
708        (long long)pte_val(pte), (long long)pmd_val(*pmd));
709    if (page)
710        dump_page(page);
711    printk(KERN_ALERT
712        "addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
713        (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
714    /*
715     * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
716     */
717    if (vma->vm_ops)
718        print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
719                (unsigned long)vma->vm_ops->fault);
720    if (vma->vm_file && vma->vm_file->f_op)
721        print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
722                (unsigned long)vma->vm_file->f_op->mmap);
723    dump_stack();
724    add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
725}
726
727static inline bool is_cow_mapping(vm_flags_t flags)
728{
729    return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
730}
731
732/*
733 * vm_normal_page -- This function gets the "struct page" associated with a pte.
734 *
735 * "Special" mappings do not wish to be associated with a "struct page" (either
736 * it doesn't exist, or it exists but they don't want to touch it). In this
737 * case, NULL is returned here. "Normal" mappings do have a struct page.
738 *
739 * There are 2 broad cases. Firstly, an architecture may define a pte_special()
740 * pte bit, in which case this function is trivial. Secondly, an architecture
741 * may not have a spare pte bit, which requires a more complicated scheme,
742 * described below.
743 *
744 * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
745 * special mapping (even if there are underlying and valid "struct pages").
746 * COWed pages of a VM_PFNMAP are always normal.
747 *
748 * The way we recognize COWed pages within VM_PFNMAP mappings is through the
749 * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
750 * set, and the vm_pgoff will point to the first PFN mapped: thus every special
751 * mapping will always honor the rule
752 *
753 * pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
754 *
755 * And for normal mappings this is false.
756 *
757 * This restricts such mappings to be a linear translation from virtual address
758 * to pfn. To get around this restriction, we allow arbitrary mappings so long
759 * as the vma is not a COW mapping; in that case, we know that all ptes are
760 * special (because none can have been COWed).
761 *
762 *
763 * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
764 *
765 * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
766 * page" backing, however the difference is that _all_ pages with a struct
767 * page (that is, those where pfn_valid is true) are refcounted and considered
768 * normal pages by the VM. The disadvantage is that pages are refcounted
769 * (which can be slower and simply not an option for some PFNMAP users). The
770 * advantage is that we don't have to follow the strict linearity rule of
771 * PFNMAP mappings in order to support COWable mappings.
772 *
773 */
774#ifdef __HAVE_ARCH_PTE_SPECIAL
775# define HAVE_PTE_SPECIAL 1
776#else
777# define HAVE_PTE_SPECIAL 0
778#endif
779struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
780                pte_t pte)
781{
782    unsigned long pfn = pte_pfn(pte);
783
784    if (HAVE_PTE_SPECIAL) {
785        if (likely(!pte_special(pte)))
786            goto check_pfn;
787        if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
788            return NULL;
789        if (!is_zero_pfn(pfn))
790            print_bad_pte(vma, addr, pte, NULL);
791        return NULL;
792    }
793
794    /* !HAVE_PTE_SPECIAL case follows: */
795
796    if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
797        if (vma->vm_flags & VM_MIXEDMAP) {
798            if (!pfn_valid(pfn))
799                return NULL;
800            goto out;
801        } else {
802            unsigned long off;
803            off = (addr - vma->vm_start) >> PAGE_SHIFT;
804            if (pfn == vma->vm_pgoff + off)
805                return NULL;
806            if (!is_cow_mapping(vma->vm_flags))
807                return NULL;
808        }
809    }
810
811    if (is_zero_pfn(pfn))
812        return NULL;
813check_pfn:
814    if (unlikely(pfn > highest_memmap_pfn)) {
815        print_bad_pte(vma, addr, pte, NULL);
816        return NULL;
817    }
818
819    /*
820     * NOTE! We still have PageReserved() pages in the page tables.
821     * eg. VDSO mappings can cause them to exist.
822     */
823out:
824    return pfn_to_page(pfn);
825}
826
827/*
828 * copy one vm_area from one task to the other. Assumes the page tables
829 * already present in the new task to be cleared in the whole range
830 * covered by this vma.
831 */
832
833static inline unsigned long
834copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
835        pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
836        unsigned long addr, int *rss)
837{
838    unsigned long vm_flags = vma->vm_flags;
839    pte_t pte = *src_pte;
840    struct page *page;
841
842    /* pte contains position in swap or file, so copy. */
843    if (unlikely(!pte_present(pte))) {
844        if (!pte_file(pte)) {
845            swp_entry_t entry = pte_to_swp_entry(pte);
846
847            if (swap_duplicate(entry) < 0)
848                return entry.val;
849
850            /* make sure dst_mm is on swapoff's mmlist. */
851            if (unlikely(list_empty(&dst_mm->mmlist))) {
852                spin_lock(&mmlist_lock);
853                if (list_empty(&dst_mm->mmlist))
854                    list_add(&dst_mm->mmlist,
855                         &src_mm->mmlist);
856                spin_unlock(&mmlist_lock);
857            }
858            if (likely(!non_swap_entry(entry)))
859                rss[MM_SWAPENTS]++;
860            else if (is_migration_entry(entry)) {
861                page = migration_entry_to_page(entry);
862
863                if (PageAnon(page))
864                    rss[MM_ANONPAGES]++;
865                else
866                    rss[MM_FILEPAGES]++;
867
868                if (is_write_migration_entry(entry) &&
869                    is_cow_mapping(vm_flags)) {
870                    /*
871                     * COW mappings require pages in both
872                     * parent and child to be set to read.
873                     */
874                    make_migration_entry_read(&entry);
875                    pte = swp_entry_to_pte(entry);
876                    set_pte_at(src_mm, addr, src_pte, pte);
877                }
878            }
879        }
880        goto out_set_pte;
881    }
882
883    /*
884     * If it's a COW mapping, write protect it both
885     * in the parent and the child
886     */
887    if (is_cow_mapping(vm_flags)) {
888        ptep_set_wrprotect(src_mm, addr, src_pte);
889        pte = pte_wrprotect(pte);
890    }
891
892    /*
893     * If it's a shared mapping, mark it clean in
894     * the child
895     */
896    if (vm_flags & VM_SHARED)
897        pte = pte_mkclean(pte);
898    pte = pte_mkold(pte);
899
900    page = vm_normal_page(vma, addr, pte);
901    if (page) {
902        get_page(page);
903        page_dup_rmap(page);
904        if (PageAnon(page))
905            rss[MM_ANONPAGES]++;
906        else
907            rss[MM_FILEPAGES]++;
908    }
909
910out_set_pte:
911    set_pte_at(dst_mm, addr, dst_pte, pte);
912    return 0;
913}
914
915int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
916           pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
917           unsigned long addr, unsigned long end)
918{
919    pte_t *orig_src_pte, *orig_dst_pte;
920    pte_t *src_pte, *dst_pte;
921    spinlock_t *src_ptl, *dst_ptl;
922    int progress = 0;
923    int rss[NR_MM_COUNTERS];
924    swp_entry_t entry = (swp_entry_t){0};
925
926again:
927    init_rss_vec(rss);
928
929    dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
930    if (!dst_pte)
931        return -ENOMEM;
932    src_pte = pte_offset_map(src_pmd, addr);
933    src_ptl = pte_lockptr(src_mm, src_pmd);
934    spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
935    orig_src_pte = src_pte;
936    orig_dst_pte = dst_pte;
937    arch_enter_lazy_mmu_mode();
938
939    do {
940        /*
941         * We are holding two locks at this point - either of them
942         * could generate latencies in another task on another CPU.
943         */
944        if (progress >= 32) {
945            progress = 0;
946            if (need_resched() ||
947                spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
948                break;
949        }
950        if (pte_none(*src_pte)) {
951            progress++;
952            continue;
953        }
954        entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
955                            vma, addr, rss);
956        if (entry.val)
957            break;
958        progress += 8;
959    } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
960
961    arch_leave_lazy_mmu_mode();
962    spin_unlock(src_ptl);
963    pte_unmap(orig_src_pte);
964    add_mm_rss_vec(dst_mm, rss);
965    pte_unmap_unlock(orig_dst_pte, dst_ptl);
966    cond_resched();
967
968    if (entry.val) {
969        if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
970            return -ENOMEM;
971        progress = 0;
972    }
973    if (addr != end)
974        goto again;
975    return 0;
976}
977
978static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
979        pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
980        unsigned long addr, unsigned long end)
981{
982    pmd_t *src_pmd, *dst_pmd;
983    unsigned long next;
984
985    dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
986    if (!dst_pmd)
987        return -ENOMEM;
988    src_pmd = pmd_offset(src_pud, addr);
989    do {
990        next = pmd_addr_end(addr, end);
991        if (pmd_trans_huge(*src_pmd)) {
992            int err;
993            VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
994            err = copy_huge_pmd(dst_mm, src_mm,
995                        dst_pmd, src_pmd, addr, vma);
996            if (err == -ENOMEM)
997                return -ENOMEM;
998            if (!err)
999                continue;
1000            /* fall through */
1001        }
1002        if (pmd_none_or_clear_bad(src_pmd))
1003            continue;
1004        if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
1005                        vma, addr, next))
1006            return -ENOMEM;
1007    } while (dst_pmd++, src_pmd++, addr = next, addr != end);
1008    return 0;
1009}
1010
1011static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1012        pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
1013        unsigned long addr, unsigned long end)
1014{
1015    pud_t *src_pud, *dst_pud;
1016    unsigned long next;
1017
1018    dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
1019    if (!dst_pud)
1020        return -ENOMEM;
1021    src_pud = pud_offset(src_pgd, addr);
1022    do {
1023        next = pud_addr_end(addr, end);
1024        if (pud_none_or_clear_bad(src_pud))
1025            continue;
1026        if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
1027                        vma, addr, next))
1028            return -ENOMEM;
1029    } while (dst_pud++, src_pud++, addr = next, addr != end);
1030    return 0;
1031}
1032
1033int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1034        struct vm_area_struct *vma)
1035{
1036    pgd_t *src_pgd, *dst_pgd;
1037    unsigned long next;
1038    unsigned long addr = vma->vm_start;
1039    unsigned long end = vma->vm_end;
1040    unsigned long mmun_start; /* For mmu_notifiers */
1041    unsigned long mmun_end; /* For mmu_notifiers */
1042    bool is_cow;
1043    int ret;
1044
1045    /*
1046     * Don't copy ptes where a page fault will fill them correctly.
1047     * Fork becomes much lighter when there are big shared or private
1048     * readonly mappings. The tradeoff is that copy_page_range is more
1049     * efficient than faulting.
1050     */
1051    if (!(vma->vm_flags & (VM_HUGETLB | VM_NONLINEAR |
1052                   VM_PFNMAP | VM_MIXEDMAP))) {
1053        if (!vma->anon_vma)
1054            return 0;
1055    }
1056
1057    if (is_vm_hugetlb_page(vma))
1058        return copy_hugetlb_page_range(dst_mm, src_mm, vma);
1059
1060    if (unlikely(vma->vm_flags & VM_PFNMAP)) {
1061        /*
1062         * We do not free on error cases below as remove_vma
1063         * gets called on error from higher level routine
1064         */
1065        ret = track_pfn_copy(vma);
1066        if (ret)
1067            return ret;
1068    }
1069
1070    /*
1071     * We need to invalidate the secondary MMU mappings only when
1072     * there could be a permission downgrade on the ptes of the
1073     * parent mm. And a permission downgrade will only happen if
1074     * is_cow_mapping() returns true.
1075     */
1076    is_cow = is_cow_mapping(vma->vm_flags);
1077    mmun_start = addr;
1078    mmun_end = end;
1079    if (is_cow)
1080        mmu_notifier_invalidate_range_start(src_mm, mmun_start,
1081                            mmun_end);
1082
1083    ret = 0;
1084    dst_pgd = pgd_offset(dst_mm, addr);
1085    src_pgd = pgd_offset(src_mm, addr);
1086    do {
1087        next = pgd_addr_end(addr, end);
1088        if (pgd_none_or_clear_bad(src_pgd))
1089            continue;
1090        if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
1091                        vma, addr, next))) {
1092            ret = -ENOMEM;
1093            break;
1094        }
1095    } while (dst_pgd++, src_pgd++, addr = next, addr != end);
1096
1097    if (is_cow)
1098        mmu_notifier_invalidate_range_end(src_mm, mmun_start, mmun_end);
1099    return ret;
1100}
1101
1102static unsigned long zap_pte_range(struct mmu_gather *tlb,
1103                struct vm_area_struct *vma, pmd_t *pmd,
1104                unsigned long addr, unsigned long end,
1105                struct zap_details *details)
1106{
1107    struct mm_struct *mm = tlb->mm;
1108    int force_flush = 0;
1109    int rss[NR_MM_COUNTERS];
1110    spinlock_t *ptl;
1111    pte_t *start_pte;
1112    pte_t *pte;
1113
1114again:
1115    init_rss_vec(rss);
1116    start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
1117    pte = start_pte;
1118    arch_enter_lazy_mmu_mode();
1119    do {
1120        pte_t ptent = *pte;
1121        if (pte_none(ptent)) {
1122            continue;
1123        }
1124
1125        if (pte_present(ptent)) {
1126            struct page *page;
1127
1128            page = vm_normal_page(vma, addr, ptent);
1129            if (unlikely(details) && page) {
1130                /*
1131                 * unmap_shared_mapping_pages() wants to
1132                 * invalidate cache without truncating:
1133                 * unmap shared but keep private pages.
1134                 */
1135                if (details->check_mapping &&
1136                    details->check_mapping != page->mapping)
1137                    continue;
1138                /*
1139                 * Each page->index must be checked when
1140                 * invalidating or truncating nonlinear.
1141                 */
1142                if (details->nonlinear_vma &&
1143                    (page->index < details->first_index ||
1144                     page->index > details->last_index))
1145                    continue;
1146            }
1147            ptent = ptep_get_and_clear_full(mm, addr, pte,
1148                            tlb->fullmm);
1149            tlb_remove_tlb_entry(tlb, pte, addr);
1150            if (unlikely(!page))
1151                continue;
1152            if (unlikely(details) && details->nonlinear_vma
1153                && linear_page_index(details->nonlinear_vma,
1154                        addr) != page->index)
1155                set_pte_at(mm, addr, pte,
1156                       pgoff_to_pte(page->index));
1157            if (PageAnon(page))
1158                rss[MM_ANONPAGES]--;
1159            else {
1160                if (pte_dirty(ptent))
1161                    set_page_dirty(page);
1162                if (pte_young(ptent) &&
1163                    likely(!VM_SequentialReadHint(vma)))
1164                    mark_page_accessed(page);
1165                rss[MM_FILEPAGES]--;
1166            }
1167            page_remove_rmap(page);
1168            if (unlikely(page_mapcount(page) < 0))
1169                print_bad_pte(vma, addr, ptent, page);
1170            force_flush = !__tlb_remove_page(tlb, page);
1171            if (force_flush)
1172                break;
1173            continue;
1174        }
1175        /*
1176         * If details->check_mapping, we leave swap entries;
1177         * if details->nonlinear_vma, we leave file entries.
1178         */
1179        if (unlikely(details))
1180            continue;
1181        if (pte_file(ptent)) {
1182            if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
1183                print_bad_pte(vma, addr, ptent, NULL);
1184        } else {
1185            swp_entry_t entry = pte_to_swp_entry(ptent);
1186
1187            if (!non_swap_entry(entry))
1188                rss[MM_SWAPENTS]--;
1189            else if (is_migration_entry(entry)) {
1190                struct page *page;
1191
1192                page = migration_entry_to_page(entry);
1193
1194                if (PageAnon(page))
1195                    rss[MM_ANONPAGES]--;
1196                else
1197                    rss[MM_FILEPAGES]--;
1198            }
1199            if (unlikely(!free_swap_and_cache(entry)))
1200                print_bad_pte(vma, addr, ptent, NULL);
1201        }
1202        pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
1203    } while (pte++, addr += PAGE_SIZE, addr != end);
1204
1205    add_mm_rss_vec(mm, rss);
1206    arch_leave_lazy_mmu_mode();
1207    pte_unmap_unlock(start_pte, ptl);
1208
1209    /*
1210     * mmu_gather ran out of room to batch pages, we break out of
1211     * the PTE lock to avoid doing the potential expensive TLB invalidate
1212     * and page-free while holding it.
1213     */
1214    if (force_flush) {
1215        force_flush = 0;
1216
1217#ifdef HAVE_GENERIC_MMU_GATHER
1218        tlb->start = addr;
1219        tlb->end = end;
1220#endif
1221        tlb_flush_mmu(tlb);
1222        if (addr != end)
1223            goto again;
1224    }
1225
1226    return addr;
1227}
1228
1229static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1230                struct vm_area_struct *vma, pud_t *pud,
1231                unsigned long addr, unsigned long end,
1232                struct zap_details *details)
1233{
1234    pmd_t *pmd;
1235    unsigned long next;
1236
1237    pmd = pmd_offset(pud, addr);
1238    do {
1239        next = pmd_addr_end(addr, end);
1240        if (pmd_trans_huge(*pmd)) {
1241            if (next - addr != HPAGE_PMD_SIZE) {
1242#ifdef CONFIG_DEBUG_VM
1243                if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
1244                    pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
1245                        __func__, addr, end,
1246                        vma->vm_start,
1247                        vma->vm_end);
1248                    BUG();
1249                }
1250#endif
1251                split_huge_page_pmd(vma, addr, pmd);
1252            } else if (zap_huge_pmd(tlb, vma, pmd, addr))
1253                goto next;
1254            /* fall through */
1255        }
1256        /*
1257         * Here there can be other concurrent MADV_DONTNEED or
1258         * trans huge page faults running, and if the pmd is
1259         * none or trans huge it can change under us. This is
1260         * because MADV_DONTNEED holds the mmap_sem in read
1261         * mode.
1262         */
1263        if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1264            goto next;
1265        next = zap_pte_range(tlb, vma, pmd, addr, next, details);
1266next:
1267        cond_resched();
1268    } while (pmd++, addr = next, addr != end);
1269
1270    return addr;
1271}
1272
1273static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1274                struct vm_area_struct *vma, pgd_t *pgd,
1275                unsigned long addr, unsigned long end,
1276                struct zap_details *details)
1277{
1278    pud_t *pud;
1279    unsigned long next;
1280
1281    pud = pud_offset(pgd, addr);
1282    do {
1283        next = pud_addr_end(addr, end);
1284        if (pud_none_or_clear_bad(pud))
1285            continue;
1286        next = zap_pmd_range(tlb, vma, pud, addr, next, details);
1287    } while (pud++, addr = next, addr != end);
1288
1289    return addr;
1290}
1291
1292static void unmap_page_range(struct mmu_gather *tlb,
1293                 struct vm_area_struct *vma,
1294                 unsigned long addr, unsigned long end,
1295                 struct zap_details *details)
1296{
1297    pgd_t *pgd;
1298    unsigned long next;
1299
1300    if (details && !details->check_mapping && !details->nonlinear_vma)
1301        details = NULL;
1302
1303    BUG_ON(addr >= end);
1304    mem_cgroup_uncharge_start();
1305    tlb_start_vma(tlb, vma);
1306    pgd = pgd_offset(vma->vm_mm, addr);
1307    do {
1308        next = pgd_addr_end(addr, end);
1309        if (pgd_none_or_clear_bad(pgd))
1310            continue;
1311        next = zap_pud_range(tlb, vma, pgd, addr, next, details);
1312    } while (pgd++, addr = next, addr != end);
1313    tlb_end_vma(tlb, vma);
1314    mem_cgroup_uncharge_end();
1315}
1316
1317
1318static void unmap_single_vma(struct mmu_gather *tlb,
1319        struct vm_area_struct *vma, unsigned long start_addr,
1320        unsigned long end_addr,
1321        struct zap_details *details)
1322{
1323    unsigned long start = max(vma->vm_start, start_addr);
1324    unsigned long end;
1325
1326    if (start >= vma->vm_end)
1327        return;
1328    end = min(vma->vm_end, end_addr);
1329    if (end <= vma->vm_start)
1330        return;
1331
1332    if (vma->vm_file)
1333        uprobe_munmap(vma, start, end);
1334
1335    if (unlikely(vma->vm_flags & VM_PFNMAP))
1336        untrack_pfn(vma, 0, 0);
1337
1338    if (start != end) {
1339        if (unlikely(is_vm_hugetlb_page(vma))) {
1340            /*
1341             * It is undesirable to test vma->vm_file as it
1342             * should be non-null for valid hugetlb area.
1343             * However, vm_file will be NULL in the error
1344             * cleanup path of do_mmap_pgoff. When
1345             * hugetlbfs ->mmap method fails,
1346             * do_mmap_pgoff() nullifies vma->vm_file
1347             * before calling this function to clean up.
1348             * Since no pte has actually been setup, it is
1349             * safe to do nothing in this case.
1350             */
1351            if (vma->vm_file) {
1352                mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
1353                __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
1354                mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
1355            }
1356        } else
1357            unmap_page_range(tlb, vma, start, end, details);
1358    }
1359}
1360
1361/**
1362 * unmap_vmas - unmap a range of memory covered by a list of vma's
1363 * @tlb: address of the caller's struct mmu_gather
1364 * @vma: the starting vma
1365 * @start_addr: virtual address at which to start unmapping
1366 * @end_addr: virtual address at which to end unmapping
1367 *
1368 * Unmap all pages in the vma list.
1369 *
1370 * Only addresses between `start' and `end' will be unmapped.
1371 *
1372 * The VMA list must be sorted in ascending virtual address order.
1373 *
1374 * unmap_vmas() assumes that the caller will flush the whole unmapped address
1375 * range after unmap_vmas() returns. So the only responsibility here is to
1376 * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1377 * drops the lock and schedules.
1378 */
1379void unmap_vmas(struct mmu_gather *tlb,
1380        struct vm_area_struct *vma, unsigned long start_addr,
1381        unsigned long end_addr)
1382{
1383    struct mm_struct *mm = vma->vm_mm;
1384
1385    mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1386    for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
1387        unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
1388    mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1389}
1390
1391/**
1392 * zap_page_range - remove user pages in a given range
1393 * @vma: vm_area_struct holding the applicable pages
1394 * @start: starting address of pages to zap
1395 * @size: number of bytes to zap
1396 * @details: details of nonlinear truncation or shared cache invalidation
1397 *
1398 * Caller must protect the VMA list
1399 */
1400void zap_page_range(struct vm_area_struct *vma, unsigned long start,
1401        unsigned long size, struct zap_details *details)
1402{
1403    struct mm_struct *mm = vma->vm_mm;
1404    struct mmu_gather tlb;
1405    unsigned long end = start + size;
1406
1407    lru_add_drain();
1408    tlb_gather_mmu(&tlb, mm, 0);
1409    update_hiwater_rss(mm);
1410    mmu_notifier_invalidate_range_start(mm, start, end);
1411    for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
1412        unmap_single_vma(&tlb, vma, start, end, details);
1413    mmu_notifier_invalidate_range_end(mm, start, end);
1414    tlb_finish_mmu(&tlb, start, end);
1415}
1416
1417/**
1418 * zap_page_range_single - remove user pages in a given range
1419 * @vma: vm_area_struct holding the applicable pages
1420 * @address: starting address of pages to zap
1421 * @size: number of bytes to zap
1422 * @details: details of nonlinear truncation or shared cache invalidation
1423 *
1424 * The range must fit into one VMA.
1425 */
1426static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
1427        unsigned long size, struct zap_details *details)
1428{
1429    struct mm_struct *mm = vma->vm_mm;
1430    struct mmu_gather tlb;
1431    unsigned long end = address + size;
1432
1433    lru_add_drain();
1434    tlb_gather_mmu(&tlb, mm, 0);
1435    update_hiwater_rss(mm);
1436    mmu_notifier_invalidate_range_start(mm, address, end);
1437    unmap_single_vma(&tlb, vma, address, end, details);
1438    mmu_notifier_invalidate_range_end(mm, address, end);
1439    tlb_finish_mmu(&tlb, address, end);
1440}
1441
1442/**
1443 * zap_vma_ptes - remove ptes mapping the vma
1444 * @vma: vm_area_struct holding ptes to be zapped
1445 * @address: starting address of pages to zap
1446 * @size: number of bytes to zap
1447 *
1448 * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1449 *
1450 * The entire address range must be fully contained within the vma.
1451 *
1452 * Returns 0 if successful.
1453 */
1454int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1455        unsigned long size)
1456{
1457    if (address < vma->vm_start || address + size > vma->vm_end ||
1458                !(vma->vm_flags & VM_PFNMAP))
1459        return -1;
1460    zap_page_range_single(vma, address, size, NULL);
1461    return 0;
1462}
1463EXPORT_SYMBOL_GPL(zap_vma_ptes);
1464
1465/**
1466 * follow_page_mask - look up a page descriptor from a user-virtual address
1467 * @vma: vm_area_struct mapping @address
1468 * @address: virtual address to look up
1469 * @flags: flags modifying lookup behaviour
1470 * @page_mask: on output, *page_mask is set according to the size of the page
1471 *
1472 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
1473 *
1474 * Returns the mapped (struct page *), %NULL if no mapping exists, or
1475 * an error pointer if there is a mapping to something not represented
1476 * by a page descriptor (see also vm_normal_page()).
1477 */
1478struct page *follow_page_mask(struct vm_area_struct *vma,
1479                  unsigned long address, unsigned int flags,
1480                  unsigned int *page_mask)
1481{
1482    pgd_t *pgd;
1483    pud_t *pud;
1484    pmd_t *pmd;
1485    pte_t *ptep, pte;
1486    spinlock_t *ptl;
1487    struct page *page;
1488    struct mm_struct *mm = vma->vm_mm;
1489
1490    *page_mask = 0;
1491
1492    page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1493    if (!IS_ERR(page)) {
1494        BUG_ON(flags & FOLL_GET);
1495        goto out;
1496    }
1497
1498    page = NULL;
1499    pgd = pgd_offset(mm, address);
1500    if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1501        goto no_page_table;
1502
1503    pud = pud_offset(pgd, address);
1504    if (pud_none(*pud))
1505        goto no_page_table;
1506    if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
1507        BUG_ON(flags & FOLL_GET);
1508        page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1509        goto out;
1510    }
1511    if (unlikely(pud_bad(*pud)))
1512        goto no_page_table;
1513
1514    pmd = pmd_offset(pud, address);
1515    if (pmd_none(*pmd))
1516        goto no_page_table;
1517    if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
1518        BUG_ON(flags & FOLL_GET);
1519        page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1520        goto out;
1521    }
1522    if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
1523        goto no_page_table;
1524    if (pmd_trans_huge(*pmd)) {
1525        if (flags & FOLL_SPLIT) {
1526            split_huge_page_pmd(vma, address, pmd);
1527            goto split_fallthrough;
1528        }
1529        spin_lock(&mm->page_table_lock);
1530        if (likely(pmd_trans_huge(*pmd))) {
1531            if (unlikely(pmd_trans_splitting(*pmd))) {
1532                spin_unlock(&mm->page_table_lock);
1533                wait_split_huge_page(vma->anon_vma, pmd);
1534            } else {
1535                page = follow_trans_huge_pmd(vma, address,
1536                                 pmd, flags);
1537                spin_unlock(&mm->page_table_lock);
1538                *page_mask = HPAGE_PMD_NR - 1;
1539                goto out;
1540            }
1541        } else
1542            spin_unlock(&mm->page_table_lock);
1543        /* fall through */
1544    }
1545split_fallthrough:
1546    if (unlikely(pmd_bad(*pmd)))
1547        goto no_page_table;
1548
1549    ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1550
1551    pte = *ptep;
1552    if (!pte_present(pte)) {
1553        swp_entry_t entry;
1554        /*
1555         * KSM's break_ksm() relies upon recognizing a ksm page
1556         * even while it is being migrated, so for that case we
1557         * need migration_entry_wait().
1558         */
1559        if (likely(!(flags & FOLL_MIGRATION)))
1560            goto no_page;
1561        if (pte_none(pte) || pte_file(pte))
1562            goto no_page;
1563        entry = pte_to_swp_entry(pte);
1564        if (!is_migration_entry(entry))
1565            goto no_page;
1566        pte_unmap_unlock(ptep, ptl);
1567        migration_entry_wait(mm, pmd, address);
1568        goto split_fallthrough;
1569    }
1570    if ((flags & FOLL_NUMA) && pte_numa(pte))
1571        goto no_page;
1572    if ((flags & FOLL_WRITE) && !pte_write(pte))
1573        goto unlock;
1574
1575    page = vm_normal_page(vma, address, pte);
1576    if (unlikely(!page)) {
1577        if ((flags & FOLL_DUMP) ||
1578            !is_zero_pfn(pte_pfn(pte)))
1579            goto bad_page;
1580        page = pte_page(pte);
1581    }
1582
1583    if (flags & FOLL_GET)
1584        get_page_foll(page);
1585    if (flags & FOLL_TOUCH) {
1586        if ((flags & FOLL_WRITE) &&
1587            !pte_dirty(pte) && !PageDirty(page))
1588            set_page_dirty(page);
1589        /*
1590         * pte_mkyoung() would be more correct here, but atomic care
1591         * is needed to avoid losing the dirty bit: it is easier to use
1592         * mark_page_accessed().
1593         */
1594        mark_page_accessed(page);
1595    }
1596    if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1597        /*
1598         * The preliminary mapping check is mainly to avoid the
1599         * pointless overhead of lock_page on the ZERO_PAGE
1600         * which might bounce very badly if there is contention.
1601         *
1602         * If the page is already locked, we don't need to
1603         * handle it now - vmscan will handle it later if and
1604         * when it attempts to reclaim the page.
1605         */
1606        if (page->mapping && trylock_page(page)) {
1607            lru_add_drain(); /* push cached pages to LRU */
1608            /*
1609             * Because we lock page here, and migration is
1610             * blocked by the pte's page reference, and we
1611             * know the page is still mapped, we don't even
1612             * need to check for file-cache page truncation.
1613             */
1614            mlock_vma_page(page);
1615            unlock_page(page);
1616        }
1617    }
1618unlock:
1619    pte_unmap_unlock(ptep, ptl);
1620out:
1621    return page;
1622
1623bad_page:
1624    pte_unmap_unlock(ptep, ptl);
1625    return ERR_PTR(-EFAULT);
1626
1627no_page:
1628    pte_unmap_unlock(ptep, ptl);
1629    if (!pte_none(pte))
1630        return page;
1631
1632no_page_table:
1633    /*
1634     * When core dumping an enormous anonymous area that nobody
1635     * has touched so far, we don't want to allocate unnecessary pages or
1636     * page tables. Return error instead of NULL to skip handle_mm_fault,
1637     * then get_dump_page() will return NULL to leave a hole in the dump.
1638     * But we can only make this optimization where a hole would surely
1639     * be zero-filled if handle_mm_fault() actually did handle it.
1640     */
1641    if ((flags & FOLL_DUMP) &&
1642        (!vma->vm_ops || !vma->vm_ops->fault))
1643        return ERR_PTR(-EFAULT);
1644    return page;
1645}
1646
1647static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
1648{
1649    return stack_guard_page_start(vma, addr) ||
1650           stack_guard_page_end(vma, addr+PAGE_SIZE);
1651}
1652
1653/**
1654 * __get_user_pages() - pin user pages in memory
1655 * @tsk: task_struct of target task
1656 * @mm: mm_struct of target mm
1657 * @start: starting user address
1658 * @nr_pages: number of pages from start to pin
1659 * @gup_flags: flags modifying pin behaviour
1660 * @pages: array that receives pointers to the pages pinned.
1661 * Should be at least nr_pages long. Or NULL, if caller
1662 * only intends to ensure the pages are faulted in.
1663 * @vmas: array of pointers to vmas corresponding to each page.
1664 * Or NULL if the caller does not require them.
1665 * @nonblocking: whether waiting for disk IO or mmap_sem contention
1666 *
1667 * Returns number of pages pinned. This may be fewer than the number
1668 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1669 * were pinned, returns -errno. Each page returned must be released
1670 * with a put_page() call when it is finished with. vmas will only
1671 * remain valid while mmap_sem is held.
1672 *
1673 * Must be called with mmap_sem held for read or write.
1674 *
1675 * __get_user_pages walks a process's page tables and takes a reference to
1676 * each struct page that each user address corresponds to at a given
1677 * instant. That is, it takes the page that would be accessed if a user
1678 * thread accesses the given user virtual address at that instant.
1679 *
1680 * This does not guarantee that the page exists in the user mappings when
1681 * __get_user_pages returns, and there may even be a completely different
1682 * page there in some cases (eg. if mmapped pagecache has been invalidated
1683 * and subsequently re faulted). However it does guarantee that the page
1684 * won't be freed completely. And mostly callers simply care that the page
1685 * contains data that was valid *at some point in time*. Typically, an IO
1686 * or similar operation cannot guarantee anything stronger anyway because
1687 * locks can't be held over the syscall boundary.
1688 *
1689 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1690 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1691 * appropriate) must be called after the page is finished with, and
1692 * before put_page is called.
1693 *
1694 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
1695 * or mmap_sem contention, and if waiting is needed to pin all pages,
1696 * *@nonblocking will be set to 0.
1697 *
1698 * In most cases, get_user_pages or get_user_pages_fast should be used
1699 * instead of __get_user_pages. __get_user_pages should be used only if
1700 * you need some special @gup_flags.
1701 */
1702long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1703        unsigned long start, unsigned long nr_pages,
1704        unsigned int gup_flags, struct page **pages,
1705        struct vm_area_struct **vmas, int *nonblocking)
1706{
1707    long i;
1708    unsigned long vm_flags;
1709    unsigned int page_mask;
1710
1711    if (!nr_pages)
1712        return 0;
1713
1714    VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1715
1716    /*
1717     * Require read or write permissions.
1718     * If FOLL_FORCE is set, we only require the "MAY" flags.
1719     */
1720    vm_flags = (gup_flags & FOLL_WRITE) ?
1721            (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1722    vm_flags &= (gup_flags & FOLL_FORCE) ?
1723            (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1724
1725    /*
1726     * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
1727     * would be called on PROT_NONE ranges. We must never invoke
1728     * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
1729     * page faults would unprotect the PROT_NONE ranges if
1730     * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
1731     * bitflag. So to avoid that, don't set FOLL_NUMA if
1732     * FOLL_FORCE is set.
1733     */
1734    if (!(gup_flags & FOLL_FORCE))
1735        gup_flags |= FOLL_NUMA;
1736
1737    i = 0;
1738
1739    do {
1740        struct vm_area_struct *vma;
1741
1742        vma = find_extend_vma(mm, start);
1743        if (!vma && in_gate_area(mm, start)) {
1744            unsigned long pg = start & PAGE_MASK;
1745            pgd_t *pgd;
1746            pud_t *pud;
1747            pmd_t *pmd;
1748            pte_t *pte;
1749
1750            /* user gate pages are read-only */
1751            if (gup_flags & FOLL_WRITE)
1752                return i ? : -EFAULT;
1753            if (pg > TASK_SIZE)
1754                pgd = pgd_offset_k(pg);
1755            else
1756                pgd = pgd_offset_gate(mm, pg);
1757            BUG_ON(pgd_none(*pgd));
1758            pud = pud_offset(pgd, pg);
1759            BUG_ON(pud_none(*pud));
1760            pmd = pmd_offset(pud, pg);
1761            if (pmd_none(*pmd))
1762                return i ? : -EFAULT;
1763            VM_BUG_ON(pmd_trans_huge(*pmd));
1764            pte = pte_offset_map(pmd, pg);
1765            if (pte_none(*pte)) {
1766                pte_unmap(pte);
1767                return i ? : -EFAULT;
1768            }
1769            vma = get_gate_vma(mm);
1770            if (pages) {
1771                struct page *page;
1772
1773                page = vm_normal_page(vma, start, *pte);
1774                if (!page) {
1775                    if (!(gup_flags & FOLL_DUMP) &&
1776                         is_zero_pfn(pte_pfn(*pte)))
1777                        page = pte_page(*pte);
1778                    else {
1779                        pte_unmap(pte);
1780                        return i ? : -EFAULT;
1781                    }
1782                }
1783                pages[i] = page;
1784                get_page(page);
1785            }
1786            pte_unmap(pte);
1787            page_mask = 0;
1788            goto next_page;
1789        }
1790
1791        if (!vma ||
1792            (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1793            !(vm_flags & vma->vm_flags))
1794            return i ? : -EFAULT;
1795
1796        if (is_vm_hugetlb_page(vma)) {
1797            i = follow_hugetlb_page(mm, vma, pages, vmas,
1798                    &start, &nr_pages, i, gup_flags);
1799            continue;
1800        }
1801
1802        do {
1803            struct page *page;
1804            unsigned int foll_flags = gup_flags;
1805            unsigned int page_increm;
1806
1807            /*
1808             * If we have a pending SIGKILL, don't keep faulting
1809             * pages and potentially allocating memory.
1810             */
1811            if (unlikely(fatal_signal_pending(current)))
1812                return i ? i : -ERESTARTSYS;
1813
1814            cond_resched();
1815            while (!(page = follow_page_mask(vma, start,
1816                        foll_flags, &page_mask))) {
1817                int ret;
1818                unsigned int fault_flags = 0;
1819
1820                /* For mlock, just skip the stack guard page. */
1821                if (foll_flags & FOLL_MLOCK) {
1822                    if (stack_guard_page(vma, start))
1823                        goto next_page;
1824                }
1825                if (foll_flags & FOLL_WRITE)
1826                    fault_flags |= FAULT_FLAG_WRITE;
1827                if (nonblocking)
1828                    fault_flags |= FAULT_FLAG_ALLOW_RETRY;
1829                if (foll_flags & FOLL_NOWAIT)
1830                    fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
1831
1832                ret = handle_mm_fault(mm, vma, start,
1833                            fault_flags);
1834
1835                if (ret & VM_FAULT_ERROR) {
1836                    if (ret & VM_FAULT_OOM)
1837                        return i ? i : -ENOMEM;
1838                    if (ret & (VM_FAULT_HWPOISON |
1839                           VM_FAULT_HWPOISON_LARGE)) {
1840                        if (i)
1841                            return i;
1842                        else if (gup_flags & FOLL_HWPOISON)
1843                            return -EHWPOISON;
1844                        else
1845                            return -EFAULT;
1846                    }
1847                    if (ret & VM_FAULT_SIGBUS)
1848                        return i ? i : -EFAULT;
1849                    BUG();
1850                }
1851
1852                if (tsk) {
1853                    if (ret & VM_FAULT_MAJOR)
1854                        tsk->maj_flt++;
1855                    else
1856                        tsk->min_flt++;
1857                }
1858
1859                if (ret & VM_FAULT_RETRY) {
1860                    if (nonblocking)
1861                        *nonblocking = 0;
1862                    return i;
1863                }
1864
1865                /*
1866                 * The VM_FAULT_WRITE bit tells us that
1867                 * do_wp_page has broken COW when necessary,
1868                 * even if maybe_mkwrite decided not to set
1869                 * pte_write. We can thus safely do subsequent
1870                 * page lookups as if they were reads. But only
1871                 * do so when looping for pte_write is futile:
1872                 * in some cases userspace may also be wanting
1873                 * to write to the gotten user page, which a
1874                 * read fault here might prevent (a readonly
1875                 * page might get reCOWed by userspace write).
1876                 */
1877                if ((ret & VM_FAULT_WRITE) &&
1878                    !(vma->vm_flags & VM_WRITE))
1879                    foll_flags &= ~FOLL_WRITE;
1880
1881                cond_resched();
1882            }
1883            if (IS_ERR(page))
1884                return i ? i : PTR_ERR(page);
1885            if (pages) {
1886                pages[i] = page;
1887
1888                flush_anon_page(vma, page, start);
1889                flush_dcache_page(page);
1890                page_mask = 0;
1891            }
1892next_page:
1893            if (vmas) {
1894                vmas[i] = vma;
1895                page_mask = 0;
1896            }
1897            page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
1898            if (page_increm > nr_pages)
1899                page_increm = nr_pages;
1900            i += page_increm;
1901            start += page_increm * PAGE_SIZE;
1902            nr_pages -= page_increm;
1903        } while (nr_pages && start < vma->vm_end);
1904    } while (nr_pages);
1905    return i;
1906}
1907EXPORT_SYMBOL(__get_user_pages);
1908
1909/*
1910 * fixup_user_fault() - manually resolve a user page fault
1911 * @tsk: the task_struct to use for page fault accounting, or
1912 * NULL if faults are not to be recorded.
1913 * @mm: mm_struct of target mm
1914 * @address: user address
1915 * @fault_flags:flags to pass down to handle_mm_fault()
1916 *
1917 * This is meant to be called in the specific scenario where for locking reasons
1918 * we try to access user memory in atomic context (within a pagefault_disable()
1919 * section), this returns -EFAULT, and we want to resolve the user fault before
1920 * trying again.
1921 *
1922 * Typically this is meant to be used by the futex code.
1923 *
1924 * The main difference with get_user_pages() is that this function will
1925 * unconditionally call handle_mm_fault() which will in turn perform all the
1926 * necessary SW fixup of the dirty and young bits in the PTE, while
1927 * handle_mm_fault() only guarantees to update these in the struct page.
1928 *
1929 * This is important for some architectures where those bits also gate the
1930 * access permission to the page because they are maintained in software. On
1931 * such architectures, gup() will not be enough to make a subsequent access
1932 * succeed.
1933 *
1934 * This should be called with the mm_sem held for read.
1935 */
1936int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
1937             unsigned long address, unsigned int fault_flags)
1938{
1939    struct vm_area_struct *vma;
1940    int ret;
1941
1942    vma = find_extend_vma(mm, address);
1943    if (!vma || address < vma->vm_start)
1944        return -EFAULT;
1945
1946    ret = handle_mm_fault(mm, vma, address, fault_flags);
1947    if (ret & VM_FAULT_ERROR) {
1948        if (ret & VM_FAULT_OOM)
1949            return -ENOMEM;
1950        if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
1951            return -EHWPOISON;
1952        if (ret & VM_FAULT_SIGBUS)
1953            return -EFAULT;
1954        BUG();
1955    }
1956    if (tsk) {
1957        if (ret & VM_FAULT_MAJOR)
1958            tsk->maj_flt++;
1959        else
1960            tsk->min_flt++;
1961    }
1962    return 0;
1963}
1964
1965/*
1966 * get_user_pages() - pin user pages in memory
1967 * @tsk: the task_struct to use for page fault accounting, or
1968 * NULL if faults are not to be recorded.
1969 * @mm: mm_struct of target mm
1970 * @start: starting user address
1971 * @nr_pages: number of pages from start to pin
1972 * @write: whether pages will be written to by the caller
1973 * @force: whether to force write access even if user mapping is
1974 * readonly. This will result in the page being COWed even
1975 * in MAP_SHARED mappings. You do not want this.
1976 * @pages: array that receives pointers to the pages pinned.
1977 * Should be at least nr_pages long. Or NULL, if caller
1978 * only intends to ensure the pages are faulted in.
1979 * @vmas: array of pointers to vmas corresponding to each page.
1980 * Or NULL if the caller does not require them.
1981 *
1982 * Returns number of pages pinned. This may be fewer than the number
1983 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1984 * were pinned, returns -errno. Each page returned must be released
1985 * with a put_page() call when it is finished with. vmas will only
1986 * remain valid while mmap_sem is held.
1987 *
1988 * Must be called with mmap_sem held for read or write.
1989 *
1990 * get_user_pages walks a process's page tables and takes a reference to
1991 * each struct page that each user address corresponds to at a given
1992 * instant. That is, it takes the page that would be accessed if a user
1993 * thread accesses the given user virtual address at that instant.
1994 *
1995 * This does not guarantee that the page exists in the user mappings when
1996 * get_user_pages returns, and there may even be a completely different
1997 * page there in some cases (eg. if mmapped pagecache has been invalidated
1998 * and subsequently re faulted). However it does guarantee that the page
1999 * won't be freed completely. And mostly callers simply care that the page
2000 * contains data that was valid *at some point in time*. Typically, an IO
2001 * or similar operation cannot guarantee anything stronger anyway because
2002 * locks can't be held over the syscall boundary.
2003 *
2004 * If write=0, the page must not be written to. If the page is written to,
2005 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
2006 * after the page is finished with, and before put_page is called.
2007 *
2008 * get_user_pages is typically used for fewer-copy IO operations, to get a
2009 * handle on the memory by some means other than accesses via the user virtual
2010 * addresses. The pages may be submitted for DMA to devices or accessed via
2011 * their kernel linear mapping (via the kmap APIs). Care should be taken to
2012 * use the correct cache flushing APIs.
2013 *
2014 * See also get_user_pages_fast, for performance critical applications.
2015 */
2016long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
2017        unsigned long start, unsigned long nr_pages, int write,
2018        int force, struct page **pages, struct vm_area_struct **vmas)
2019{
2020    int flags = FOLL_TOUCH;
2021
2022    if (pages)
2023        flags |= FOLL_GET;
2024    if (write)
2025        flags |= FOLL_WRITE;
2026    if (force)
2027        flags |= FOLL_FORCE;
2028
2029    return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
2030                NULL);
2031}
2032EXPORT_SYMBOL(get_user_pages);
2033
2034/**
2035 * get_dump_page() - pin user page in memory while writing it to core dump
2036 * @addr: user address
2037 *
2038 * Returns struct page pointer of user page pinned for dump,
2039 * to be freed afterwards by page_cache_release() or put_page().
2040 *
2041 * Returns NULL on any kind of failure - a hole must then be inserted into
2042 * the corefile, to preserve alignment with its headers; and also returns
2043 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
2044 * allowing a hole to be left in the corefile to save diskspace.
2045 *
2046 * Called without mmap_sem, but after all other threads have been killed.
2047 */
2048#ifdef CONFIG_ELF_CORE
2049struct page *get_dump_page(unsigned long addr)
2050{
2051    struct vm_area_struct *vma;
2052    struct page *page;
2053
2054    if (__get_user_pages(current, current->mm, addr, 1,
2055                 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
2056                 NULL) < 1)
2057        return NULL;
2058    flush_cache_page(vma, addr, page_to_pfn(page));
2059    return page;
2060}
2061#endif /* CONFIG_ELF_CORE */
2062
2063pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
2064            spinlock_t **ptl)
2065{
2066    pgd_t * pgd = pgd_offset(mm, addr);
2067    pud_t * pud = pud_alloc(mm, pgd, addr);
2068    if (pud) {
2069        pmd_t * pmd = pmd_alloc(mm, pud, addr);
2070        if (pmd) {
2071            VM_BUG_ON(pmd_trans_huge(*pmd));
2072            return pte_alloc_map_lock(mm, pmd, addr, ptl);
2073        }
2074    }
2075    return NULL;
2076}
2077
2078/*
2079 * This is the old fallback for page remapping.
2080 *
2081 * For historical reasons, it only allows reserved pages. Only
2082 * old drivers should use this, and they needed to mark their
2083 * pages reserved for the old functions anyway.
2084 */
2085static int insert_page(struct vm_area_struct *vma, unsigned long addr,
2086            struct page *page, pgprot_t prot)
2087{
2088    struct mm_struct *mm = vma->vm_mm;
2089    int retval;
2090    pte_t *pte;
2091    spinlock_t *ptl;
2092
2093    retval = -EINVAL;
2094    if (PageAnon(page))
2095        goto out;
2096    retval = -ENOMEM;
2097    flush_dcache_page(page);
2098    pte = get_locked_pte(mm, addr, &ptl);
2099    if (!pte)
2100        goto out;
2101    retval = -EBUSY;
2102    if (!pte_none(*pte))
2103        goto out_unlock;
2104
2105    /* Ok, finally just insert the thing.. */
2106    get_page(page);
2107    inc_mm_counter_fast(mm, MM_FILEPAGES);
2108    page_add_file_rmap(page);
2109    set_pte_at(mm, addr, pte, mk_pte(page, prot));
2110
2111    retval = 0;
2112    pte_unmap_unlock(pte, ptl);
2113    return retval;
2114out_unlock:
2115    pte_unmap_unlock(pte, ptl);
2116out:
2117    return retval;
2118}
2119
2120/**
2121 * vm_insert_page - insert single page into user vma
2122 * @vma: user vma to map to
2123 * @addr: target user address of this page
2124 * @page: source kernel page
2125 *
2126 * This allows drivers to insert individual pages they've allocated
2127 * into a user vma.
2128 *
2129 * The page has to be a nice clean _individual_ kernel allocation.
2130 * If you allocate a compound page, you need to have marked it as
2131 * such (__GFP_COMP), or manually just split the page up yourself
2132 * (see split_page()).
2133 *
2134 * NOTE! Traditionally this was done with "remap_pfn_range()" which
2135 * took an arbitrary page protection parameter. This doesn't allow
2136 * that. Your vma protection will have to be set up correctly, which
2137 * means that if you want a shared writable mapping, you'd better
2138 * ask for a shared writable mapping!
2139 *
2140 * The page does not need to be reserved.
2141 *
2142 * Usually this function is called from f_op->mmap() handler
2143 * under mm->mmap_sem write-lock, so it can change vma->vm_flags.
2144 * Caller must set VM_MIXEDMAP on vma if it wants to call this
2145 * function from other places, for example from page-fault handler.
2146 */
2147int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
2148            struct page *page)
2149{
2150    if (addr < vma->vm_start || addr >= vma->vm_end)
2151        return -EFAULT;
2152    if (!page_count(page))
2153        return -EINVAL;
2154    if (!(vma->vm_flags & VM_MIXEDMAP)) {
2155        BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
2156        BUG_ON(vma->vm_flags & VM_PFNMAP);
2157        vma->vm_flags |= VM_MIXEDMAP;
2158    }
2159    return insert_page(vma, addr, page, vma->vm_page_prot);
2160}
2161EXPORT_SYMBOL(vm_insert_page);
2162
2163static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
2164            unsigned long pfn, pgprot_t prot)
2165{
2166    struct mm_struct *mm = vma->vm_mm;
2167    int retval;
2168    pte_t *pte, entry;
2169    spinlock_t *ptl;
2170
2171    retval = -ENOMEM;
2172    pte = get_locked_pte(mm, addr, &ptl);
2173    if (!pte)
2174        goto out;
2175    retval = -EBUSY;
2176    if (!pte_none(*pte))
2177        goto out_unlock;
2178
2179    /* Ok, finally just insert the thing.. */
2180    entry = pte_mkspecial(pfn_pte(pfn, prot));
2181    set_pte_at(mm, addr, pte, entry);
2182    update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
2183
2184    retval = 0;
2185out_unlock:
2186    pte_unmap_unlock(pte, ptl);
2187out:
2188    return retval;
2189}
2190
2191/**
2192 * vm_insert_pfn - insert single pfn into user vma
2193 * @vma: user vma to map to
2194 * @addr: target user address of this page
2195 * @pfn: source kernel pfn
2196 *
2197 * Similar to vm_insert_page, this allows drivers to insert individual pages
2198 * they've allocated into a user vma. Same comments apply.
2199 *
2200 * This function should only be called from a vm_ops->fault handler, and
2201 * in that case the handler should return NULL.
2202 *
2203 * vma cannot be a COW mapping.
2204 *
2205 * As this is called only for pages that do not currently exist, we
2206 * do not need to flush old virtual caches or the TLB.
2207 */
2208int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
2209            unsigned long pfn)
2210{
2211    int ret;
2212    pgprot_t pgprot = vma->vm_page_prot;
2213    /*
2214     * Technically, architectures with pte_special can avoid all these
2215     * restrictions (same for remap_pfn_range). However we would like
2216     * consistency in testing and feature parity among all, so we should
2217     * try to keep these invariants in place for everybody.
2218     */
2219    BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
2220    BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
2221                        (VM_PFNMAP|VM_MIXEDMAP));
2222    BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
2223    BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
2224
2225    if (addr < vma->vm_start || addr >= vma->vm_end)
2226        return -EFAULT;
2227    if (track_pfn_insert(vma, &pgprot, pfn))
2228        return -EINVAL;
2229
2230    ret = insert_pfn(vma, addr, pfn, pgprot);
2231
2232    return ret;
2233}
2234EXPORT_SYMBOL(vm_insert_pfn);
2235
2236int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
2237            unsigned long pfn)
2238{
2239    BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
2240
2241    if (addr < vma->vm_start || addr >= vma->vm_end)
2242        return -EFAULT;
2243
2244    /*
2245     * If we don't have pte special, then we have to use the pfn_valid()
2246     * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
2247     * refcount the page if pfn_valid is true (hence insert_page rather
2248     * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP
2249     * without pte special, it would there be refcounted as a normal page.
2250     */
2251    if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
2252        struct page *page;
2253
2254        page = pfn_to_page(pfn);
2255        return insert_page(vma, addr, page, vma->vm_page_prot);
2256    }
2257    return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
2258}
2259EXPORT_SYMBOL(vm_insert_mixed);
2260
2261/*
2262 * maps a range of physical memory into the requested pages. the old
2263 * mappings are removed. any references to nonexistent pages results
2264 * in null mappings (currently treated as "copy-on-access")
2265 */
2266static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
2267            unsigned long addr, unsigned long end,
2268            unsigned long pfn, pgprot_t prot)
2269{
2270    pte_t *pte;
2271    spinlock_t *ptl;
2272
2273    pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
2274    if (!pte)
2275        return -ENOMEM;
2276    arch_enter_lazy_mmu_mode();
2277    do {
2278        BUG_ON(!pte_none(*pte));
2279        set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
2280        pfn++;
2281    } while (pte++, addr += PAGE_SIZE, addr != end);
2282    arch_leave_lazy_mmu_mode();
2283    pte_unmap_unlock(pte - 1, ptl);
2284    return 0;
2285}
2286
2287static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
2288            unsigned long addr, unsigned long end,
2289            unsigned long pfn, pgprot_t prot)
2290{
2291    pmd_t *pmd;
2292    unsigned long next;
2293
2294    pfn -= addr >> PAGE_SHIFT;
2295    pmd = pmd_alloc(mm, pud, addr);
2296    if (!pmd)
2297        return -ENOMEM;
2298    VM_BUG_ON(pmd_trans_huge(*pmd));
2299    do {
2300        next = pmd_addr_end(addr, end);
2301        if (remap_pte_range(mm, pmd, addr, next,
2302                pfn + (addr >> PAGE_SHIFT), prot))
2303            return -ENOMEM;
2304    } while (pmd++, addr = next, addr != end);
2305    return 0;
2306}
2307
2308static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
2309            unsigned long addr, unsigned long end,
2310            unsigned long pfn, pgprot_t prot)
2311{
2312    pud_t *pud;
2313    unsigned long next;
2314
2315    pfn -= addr >> PAGE_SHIFT;
2316    pud = pud_alloc(mm, pgd, addr);
2317    if (!pud)
2318        return -ENOMEM;
2319    do {
2320        next = pud_addr_end(addr, end);
2321        if (remap_pmd_range(mm, pud, addr, next,
2322                pfn + (addr >> PAGE_SHIFT), prot))
2323            return -ENOMEM;
2324    } while (pud++, addr = next, addr != end);
2325    return 0;
2326}
2327
2328/**
2329 * remap_pfn_range - remap kernel memory to userspace
2330 * @vma: user vma to map to
2331 * @addr: target user address to start at
2332 * @pfn: physical address of kernel memory
2333 * @size: size of map area
2334 * @prot: page protection flags for this mapping
2335 *
2336 * Note: this is only safe if the mm semaphore is held when called.
2337 */
2338int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
2339            unsigned long pfn, unsigned long size, pgprot_t prot)
2340{
2341    pgd_t *pgd;
2342    unsigned long next;
2343    unsigned long end = addr + PAGE_ALIGN(size);
2344    struct mm_struct *mm = vma->vm_mm;
2345    int err;
2346
2347    /*
2348     * Physically remapped pages are special. Tell the
2349     * rest of the world about it:
2350     * VM_IO tells people not to look at these pages
2351     * (accesses can have side effects).
2352     * VM_PFNMAP tells the core MM that the base pages are just
2353     * raw PFN mappings, and do not have a "struct page" associated
2354     * with them.
2355     * VM_DONTEXPAND
2356     * Disable vma merging and expanding with mremap().
2357     * VM_DONTDUMP
2358     * Omit vma from core dump, even when VM_IO turned off.
2359     *
2360     * There's a horrible special case to handle copy-on-write
2361     * behaviour that some programs depend on. We mark the "original"
2362     * un-COW'ed pages by matching them up with "vma->vm_pgoff".
2363     * See vm_normal_page() for details.
2364     */
2365    if (is_cow_mapping(vma->vm_flags)) {
2366        if (addr != vma->vm_start || end != vma->vm_end)
2367            return -EINVAL;
2368        vma->vm_pgoff = pfn;
2369    }
2370
2371    err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
2372    if (err)
2373        return -EINVAL;
2374
2375    vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
2376
2377    BUG_ON(addr >= end);
2378    pfn -= addr >> PAGE_SHIFT;
2379    pgd = pgd_offset(mm, addr);
2380    flush_cache_range(vma, addr, end);
2381    do {
2382        next = pgd_addr_end(addr, end);
2383        err = remap_pud_range(mm, pgd, addr, next,
2384                pfn + (addr >> PAGE_SHIFT), prot);
2385        if (err)
2386            break;
2387    } while (pgd++, addr = next, addr != end);
2388
2389    if (err)
2390        untrack_pfn(vma, pfn, PAGE_ALIGN(size));
2391
2392    return err;
2393}
2394EXPORT_SYMBOL(remap_pfn_range);
2395
2396/**
2397 * vm_iomap_memory - remap memory to userspace
2398 * @vma: user vma to map to
2399 * @start: start of area
2400 * @len: size of area
2401 *
2402 * This is a simplified io_remap_pfn_range() for common driver use. The
2403 * driver just needs to give us the physical memory range to be mapped,
2404 * we'll figure out the rest from the vma information.
2405 *
2406 * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
2407 * whatever write-combining details or similar.
2408 */
2409int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
2410{
2411    unsigned long vm_len, pfn, pages;
2412
2413    /* Check that the physical memory area passed in looks valid */
2414    if (start + len < start)
2415        return -EINVAL;
2416    /*
2417     * You *really* shouldn't map things that aren't page-aligned,
2418     * but we've historically allowed it because IO memory might
2419     * just have smaller alignment.
2420     */
2421    len += start & ~PAGE_MASK;
2422    pfn = start >> PAGE_SHIFT;
2423    pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
2424    if (pfn + pages < pfn)
2425        return -EINVAL;
2426
2427    /* We start the mapping 'vm_pgoff' pages into the area */
2428    if (vma->vm_pgoff > pages)
2429        return -EINVAL;
2430    pfn += vma->vm_pgoff;
2431    pages -= vma->vm_pgoff;
2432
2433    /* Can we fit all of the mapping? */
2434    vm_len = vma->vm_end - vma->vm_start;
2435    if (vm_len >> PAGE_SHIFT > pages)
2436        return -EINVAL;
2437
2438    /* Ok, let it rip */
2439    return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
2440}
2441EXPORT_SYMBOL(vm_iomap_memory);
2442
2443static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
2444                     unsigned long addr, unsigned long end,
2445                     pte_fn_t fn, void *data)
2446{
2447    pte_t *pte;
2448    int err;
2449    pgtable_t token;
2450    spinlock_t *uninitialized_var(ptl);
2451
2452    pte = (mm == &init_mm) ?
2453        pte_alloc_kernel(pmd, addr) :
2454        pte_alloc_map_lock(mm, pmd, addr, &ptl);
2455    if (!pte)
2456        return -ENOMEM;
2457
2458    BUG_ON(pmd_huge(*pmd));
2459
2460    arch_enter_lazy_mmu_mode();
2461
2462    token = pmd_pgtable(*pmd);
2463
2464    do {
2465        err = fn(pte++, token, addr, data);
2466        if (err)
2467            break;
2468    } while (addr += PAGE_SIZE, addr != end);
2469
2470    arch_leave_lazy_mmu_mode();
2471
2472    if (mm != &init_mm)
2473        pte_unmap_unlock(pte-1, ptl);
2474    return err;
2475}
2476
2477static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
2478                     unsigned long addr, unsigned long end,
2479                     pte_fn_t fn, void *data)
2480{
2481    pmd_t *pmd;
2482    unsigned long next;
2483    int err;
2484
2485    BUG_ON(pud_huge(*pud));
2486
2487    pmd = pmd_alloc(mm, pud, addr);
2488    if (!pmd)
2489        return -ENOMEM;
2490    do {
2491        next = pmd_addr_end(addr, end);
2492        err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
2493        if (err)
2494            break;
2495    } while (pmd++, addr = next, addr != end);
2496    return err;
2497}
2498
2499static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
2500                     unsigned long addr, unsigned long end,
2501                     pte_fn_t fn, void *data)
2502{
2503    pud_t *pud;
2504    unsigned long next;
2505    int err;
2506
2507    pud = pud_alloc(mm, pgd, addr);
2508    if (!pud)
2509        return -ENOMEM;
2510    do {
2511        next = pud_addr_end(addr, end);
2512        err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
2513        if (err)
2514            break;
2515    } while (pud++, addr = next, addr != end);
2516    return err;
2517}
2518
2519/*
2520 * Scan a region of virtual memory, filling in page tables as necessary
2521 * and calling a provided function on each leaf page table.
2522 */
2523int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
2524            unsigned long size, pte_fn_t fn, void *data)
2525{
2526    pgd_t *pgd;
2527    unsigned long next;
2528    unsigned long end = addr + size;
2529    int err;
2530
2531    BUG_ON(addr >= end);
2532    pgd = pgd_offset(mm, addr);
2533    do {
2534        next = pgd_addr_end(addr, end);
2535        err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
2536        if (err)
2537            break;
2538    } while (pgd++, addr = next, addr != end);
2539
2540    return err;
2541}
2542EXPORT_SYMBOL_GPL(apply_to_page_range);
2543
2544/*
2545 * handle_pte_fault chooses page fault handler according to an entry
2546 * which was read non-atomically. Before making any commitment, on
2547 * those architectures or configurations (e.g. i386 with PAE) which
2548 * might give a mix of unmatched parts, do_swap_page and do_nonlinear_fault
2549 * must check under lock before unmapping the pte and proceeding
2550 * (but do_wp_page is only called after already making such a check;
2551 * and do_anonymous_page can safely check later on).
2552 */
2553static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
2554                pte_t *page_table, pte_t orig_pte)
2555{
2556    int same = 1;
2557#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
2558    if (sizeof(pte_t) > sizeof(unsigned long)) {
2559        spinlock_t *ptl = pte_lockptr(mm, pmd);
2560        spin_lock(ptl);
2561        same = pte_same(*page_table, orig_pte);
2562        spin_unlock(ptl);
2563    }
2564#endif
2565    pte_unmap(page_table);
2566    return same;
2567}
2568
2569static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
2570{
2571    /*
2572     * If the source page was a PFN mapping, we don't have
2573     * a "struct page" for it. We do a best-effort copy by
2574     * just copying from the original user address. If that
2575     * fails, we just zero-fill it. Live with it.
2576     */
2577    if (unlikely(!src)) {
2578        void *kaddr = kmap_atomic(dst);
2579        void __user *uaddr = (void __user *)(va & PAGE_MASK);
2580
2581        /*
2582         * This really shouldn't fail, because the page is there
2583         * in the page tables. But it might just be unreadable,
2584         * in which case we just give up and fill the result with
2585         * zeroes.
2586         */
2587        if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
2588            clear_page(kaddr);
2589        kunmap_atomic(kaddr);
2590        flush_dcache_page(dst);
2591    } else
2592        copy_user_highpage(dst, src, va, vma);
2593}
2594
2595/*
2596 * This routine handles present pages, when users try to write
2597 * to a shared page. It is done by copying the page to a new address
2598 * and decrementing the shared-page counter for the old page.
2599 *
2600 * Note that this routine assumes that the protection checks have been
2601 * done by the caller (the low-level page fault routine in most cases).
2602 * Thus we can safely just mark it writable once we've done any necessary
2603 * COW.
2604 *
2605 * We also mark the page dirty at this point even though the page will
2606 * change only once the write actually happens. This avoids a few races,
2607 * and potentially makes it more efficient.
2608 *
2609 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2610 * but allow concurrent faults), with pte both mapped and locked.
2611 * We return with mmap_sem still held, but pte unmapped and unlocked.
2612 */
2613static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2614        unsigned long address, pte_t *page_table, pmd_t *pmd,
2615        spinlock_t *ptl, pte_t orig_pte)
2616    __releases(ptl)
2617{
2618    struct page *old_page, *new_page = NULL;
2619    pte_t entry;
2620    int ret = 0;
2621    int page_mkwrite = 0;
2622    struct page *dirty_page = NULL;
2623    unsigned long mmun_start = 0; /* For mmu_notifiers */
2624    unsigned long mmun_end = 0; /* For mmu_notifiers */
2625
2626    old_page = vm_normal_page(vma, address, orig_pte);
2627    if (!old_page) {
2628        /*
2629         * VM_MIXEDMAP !pfn_valid() case
2630         *
2631         * We should not cow pages in a shared writeable mapping.
2632         * Just mark the pages writable as we can't do any dirty
2633         * accounting on raw pfn maps.
2634         */
2635        if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2636                     (VM_WRITE|VM_SHARED))
2637            goto reuse;
2638        goto gotten;
2639    }
2640
2641    /*
2642     * Take out anonymous pages first, anonymous shared vmas are
2643     * not dirty accountable.
2644     */
2645    if (PageAnon(old_page) && !PageKsm(old_page)) {
2646        if (!trylock_page(old_page)) {
2647            page_cache_get(old_page);
2648            pte_unmap_unlock(page_table, ptl);
2649            lock_page(old_page);
2650            page_table = pte_offset_map_lock(mm, pmd, address,
2651                             &ptl);
2652            if (!pte_same(*page_table, orig_pte)) {
2653                unlock_page(old_page);
2654                goto unlock;
2655            }
2656            page_cache_release(old_page);
2657        }
2658        if (reuse_swap_page(old_page)) {
2659            /*
2660             * The page is all ours. Move it to our anon_vma so
2661             * the rmap code will not search our parent or siblings.
2662             * Protected against the rmap code by the page lock.
2663             */
2664            page_move_anon_rmap(old_page, vma, address);
2665            unlock_page(old_page);
2666            goto reuse;
2667        }
2668        unlock_page(old_page);
2669    } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2670                    (VM_WRITE|VM_SHARED))) {
2671        /*
2672         * Only catch write-faults on shared writable pages,
2673         * read-only shared pages can get COWed by
2674         * get_user_pages(.write=1, .force=1).
2675         */
2676        if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2677            struct vm_fault vmf;
2678            int tmp;
2679
2680            vmf.virtual_address = (void __user *)(address &
2681                                PAGE_MASK);
2682            vmf.pgoff = old_page->index;
2683            vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2684            vmf.page = old_page;
2685
2686            /*
2687             * Notify the address space that the page is about to
2688             * become writable so that it can prohibit this or wait
2689             * for the page to get into an appropriate state.
2690             *
2691             * We do this without the lock held, so that it can
2692             * sleep if it needs to.
2693             */
2694            page_cache_get(old_page);
2695            pte_unmap_unlock(page_table, ptl);
2696
2697            tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2698            if (unlikely(tmp &
2699                    (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2700                ret = tmp;
2701                goto unwritable_page;
2702            }
2703            if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2704                lock_page(old_page);
2705                if (!old_page->mapping) {
2706                    ret = 0; /* retry the fault */
2707                    unlock_page(old_page);
2708                    goto unwritable_page;
2709                }
2710            } else
2711                VM_BUG_ON(!PageLocked(old_page));
2712
2713            /*
2714             * Since we dropped the lock we need to revalidate
2715             * the PTE as someone else may have changed it. If
2716             * they did, we just return, as we can count on the
2717             * MMU to tell us if they didn't also make it writable.
2718             */
2719            page_table = pte_offset_map_lock(mm, pmd, address,
2720                             &ptl);
2721            if (!pte_same(*page_table, orig_pte)) {
2722                unlock_page(old_page);
2723                goto unlock;
2724            }
2725
2726            page_mkwrite = 1;
2727        }
2728        dirty_page = old_page;
2729        get_page(dirty_page);
2730
2731reuse:
2732        flush_cache_page(vma, address, pte_pfn(orig_pte));
2733        entry = pte_mkyoung(orig_pte);
2734        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2735        if (ptep_set_access_flags(vma, address, page_table, entry,1))
2736            update_mmu_cache(vma, address, page_table);
2737        pte_unmap_unlock(page_table, ptl);
2738        ret |= VM_FAULT_WRITE;
2739
2740        if (!dirty_page)
2741            return ret;
2742
2743        /*
2744         * Yes, Virginia, this is actually required to prevent a race
2745         * with clear_page_dirty_for_io() from clearing the page dirty
2746         * bit after it clear all dirty ptes, but before a racing
2747         * do_wp_page installs a dirty pte.
2748         *
2749         * __do_fault is protected similarly.
2750         */
2751        if (!page_mkwrite) {
2752            wait_on_page_locked(dirty_page);
2753            set_page_dirty_balance(dirty_page, page_mkwrite);
2754            /* file_update_time outside page_lock */
2755            if (vma->vm_file)
2756                file_update_time(vma->vm_file);
2757        }
2758        put_page(dirty_page);
2759        if (page_mkwrite) {
2760            struct address_space *mapping = dirty_page->mapping;
2761
2762            set_page_dirty(dirty_page);
2763            unlock_page(dirty_page);
2764            page_cache_release(dirty_page);
2765            if (mapping) {
2766                /*
2767                 * Some device drivers do not set page.mapping
2768                 * but still dirty their pages
2769                 */
2770                balance_dirty_pages_ratelimited(mapping);
2771            }
2772        }
2773
2774        return ret;
2775    }
2776
2777    /*
2778     * Ok, we need to copy. Oh, well..
2779     */
2780    page_cache_get(old_page);
2781gotten:
2782    pte_unmap_unlock(page_table, ptl);
2783
2784    if (unlikely(anon_vma_prepare(vma)))
2785        goto oom;
2786
2787    if (is_zero_pfn(pte_pfn(orig_pte))) {
2788        new_page = alloc_zeroed_user_highpage_movable(vma, address);
2789        if (!new_page)
2790            goto oom;
2791    } else {
2792        new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2793        if (!new_page)
2794            goto oom;
2795        cow_user_page(new_page, old_page, address, vma);
2796    }
2797    __SetPageUptodate(new_page);
2798
2799    if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
2800        goto oom_free_new;
2801
2802    mmun_start = address & PAGE_MASK;
2803    mmun_end = mmun_start + PAGE_SIZE;
2804    mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2805
2806    /*
2807     * Re-check the pte - we dropped the lock
2808     */
2809    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2810    if (likely(pte_same(*page_table, orig_pte))) {
2811        if (old_page) {
2812            if (!PageAnon(old_page)) {
2813                dec_mm_counter_fast(mm, MM_FILEPAGES);
2814                inc_mm_counter_fast(mm, MM_ANONPAGES);
2815            }
2816        } else
2817            inc_mm_counter_fast(mm, MM_ANONPAGES);
2818        flush_cache_page(vma, address, pte_pfn(orig_pte));
2819        entry = mk_pte(new_page, vma->vm_page_prot);
2820        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2821        /*
2822         * Clear the pte entry and flush it first, before updating the
2823         * pte with the new entry. This will avoid a race condition
2824         * seen in the presence of one thread doing SMC and another
2825         * thread doing COW.
2826         */
2827        ptep_clear_flush(vma, address, page_table);
2828        page_add_new_anon_rmap(new_page, vma, address);
2829        /*
2830         * We call the notify macro here because, when using secondary
2831         * mmu page tables (such as kvm shadow page tables), we want the
2832         * new page to be mapped directly into the secondary page table.
2833         */
2834        set_pte_at_notify(mm, address, page_table, entry);
2835        update_mmu_cache(vma, address, page_table);
2836        if (old_page) {
2837            /*
2838             * Only after switching the pte to the new page may
2839             * we remove the mapcount here. Otherwise another
2840             * process may come and find the rmap count decremented
2841             * before the pte is switched to the new page, and
2842             * "reuse" the old page writing into it while our pte
2843             * here still points into it and can be read by other
2844             * threads.
2845             *
2846             * The critical issue is to order this
2847             * page_remove_rmap with the ptp_clear_flush above.
2848             * Those stores are ordered by (if nothing else,)
2849             * the barrier present in the atomic_add_negative
2850             * in page_remove_rmap.
2851             *
2852             * Then the TLB flush in ptep_clear_flush ensures that
2853             * no process can access the old page before the
2854             * decremented mapcount is visible. And the old page
2855             * cannot be reused until after the decremented
2856             * mapcount is visible. So transitively, TLBs to
2857             * old page will be flushed before it can be reused.
2858             */
2859            page_remove_rmap(old_page);
2860        }
2861
2862        /* Free the old page.. */
2863        new_page = old_page;
2864        ret |= VM_FAULT_WRITE;
2865    } else
2866        mem_cgroup_uncharge_page(new_page);
2867
2868    if (new_page)
2869        page_cache_release(new_page);
2870unlock:
2871    pte_unmap_unlock(page_table, ptl);
2872    if (mmun_end > mmun_start)
2873        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2874    if (old_page) {
2875        /*
2876         * Don't let another task, with possibly unlocked vma,
2877         * keep the mlocked page.
2878         */
2879        if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
2880            lock_page(old_page); /* LRU manipulation */
2881            munlock_vma_page(old_page);
2882            unlock_page(old_page);
2883        }
2884        page_cache_release(old_page);
2885    }
2886    return ret;
2887oom_free_new:
2888    page_cache_release(new_page);
2889oom:
2890    if (old_page)
2891        page_cache_release(old_page);
2892    return VM_FAULT_OOM;
2893
2894unwritable_page:
2895    page_cache_release(old_page);
2896    return ret;
2897}
2898
2899static void unmap_mapping_range_vma(struct vm_area_struct *vma,
2900        unsigned long start_addr, unsigned long end_addr,
2901        struct zap_details *details)
2902{
2903    zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
2904}
2905
2906static inline void unmap_mapping_range_tree(struct rb_root *root,
2907                        struct zap_details *details)
2908{
2909    struct vm_area_struct *vma;
2910    pgoff_t vba, vea, zba, zea;
2911
2912    vma_interval_tree_foreach(vma, root,
2913            details->first_index, details->last_index) {
2914
2915        vba = vma->vm_pgoff;
2916        vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2917        /* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2918        zba = details->first_index;
2919        if (zba < vba)
2920            zba = vba;
2921        zea = details->last_index;
2922        if (zea > vea)
2923            zea = vea;
2924
2925        unmap_mapping_range_vma(vma,
2926            ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2927            ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2928                details);
2929    }
2930}
2931
2932static inline void unmap_mapping_range_list(struct list_head *head,
2933                        struct zap_details *details)
2934{
2935    struct vm_area_struct *vma;
2936
2937    /*
2938     * In nonlinear VMAs there is no correspondence between virtual address
2939     * offset and file offset. So we must perform an exhaustive search
2940     * across *all* the pages in each nonlinear VMA, not just the pages
2941     * whose virtual address lies outside the file truncation point.
2942     */
2943    list_for_each_entry(vma, head, shared.nonlinear) {
2944        details->nonlinear_vma = vma;
2945        unmap_mapping_range_vma(vma, vma->vm_start, vma->vm_end, details);
2946    }
2947}
2948
2949/**
2950 * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2951 * @mapping: the address space containing mmaps to be unmapped.
2952 * @holebegin: byte in first page to unmap, relative to the start of
2953 * the underlying file. This will be rounded down to a PAGE_SIZE
2954 * boundary. Note that this is different from truncate_pagecache(), which
2955 * must keep the partial page. In contrast, we must get rid of
2956 * partial pages.
2957 * @holelen: size of prospective hole in bytes. This will be rounded
2958 * up to a PAGE_SIZE boundary. A holelen of zero truncates to the
2959 * end of the file.
2960 * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2961 * but 0 when invalidating pagecache, don't throw away private data.
2962 */
2963void unmap_mapping_range(struct address_space *mapping,
2964        loff_t const holebegin, loff_t const holelen, int even_cows)
2965{
2966    struct zap_details details;
2967    pgoff_t hba = holebegin >> PAGE_SHIFT;
2968    pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2969
2970    /* Check for overflow. */
2971    if (sizeof(holelen) > sizeof(hlen)) {
2972        long long holeend =
2973            (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2974        if (holeend & ~(long long)ULONG_MAX)
2975            hlen = ULONG_MAX - hba + 1;
2976    }
2977
2978    details.check_mapping = even_cows? NULL: mapping;
2979    details.nonlinear_vma = NULL;
2980    details.first_index = hba;
2981    details.last_index = hba + hlen - 1;
2982    if (details.last_index < details.first_index)
2983        details.last_index = ULONG_MAX;
2984
2985
2986    mutex_lock(&mapping->i_mmap_mutex);
2987    if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
2988        unmap_mapping_range_tree(&mapping->i_mmap, &details);
2989    if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2990        unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2991    mutex_unlock(&mapping->i_mmap_mutex);
2992}
2993EXPORT_SYMBOL(unmap_mapping_range);
2994
2995/*
2996 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2997 * but allow concurrent faults), and pte mapped but not yet locked.
2998 * We return with mmap_sem still held, but pte unmapped and unlocked.
2999 */
3000static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
3001        unsigned long address, pte_t *page_table, pmd_t *pmd,
3002        unsigned int flags, pte_t orig_pte)
3003{
3004    spinlock_t *ptl;
3005    struct page *page, *swapcache;
3006    swp_entry_t entry;
3007    pte_t pte;
3008    int locked;
3009    struct mem_cgroup *ptr;
3010    int exclusive = 0;
3011    int ret = 0;
3012
3013    if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3014        goto out;
3015
3016    entry = pte_to_swp_entry(orig_pte);
3017    if (unlikely(non_swap_entry(entry))) {
3018        if (is_migration_entry(entry)) {
3019            migration_entry_wait(mm, pmd, address);
3020        } else if (is_hwpoison_entry(entry)) {
3021            ret = VM_FAULT_HWPOISON;
3022        } else {
3023            print_bad_pte(vma, address, orig_pte, NULL);
3024            ret = VM_FAULT_SIGBUS;
3025        }
3026        goto out;
3027    }
3028    delayacct_set_flag(DELAYACCT_PF_SWAPIN);
3029    page = lookup_swap_cache(entry);
3030    if (!page) {
3031        page = swapin_readahead(entry,
3032                    GFP_HIGHUSER_MOVABLE, vma, address);
3033        if (!page) {
3034            /*
3035             * Back out if somebody else faulted in this pte
3036             * while we released the pte lock.
3037             */
3038            page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3039            if (likely(pte_same(*page_table, orig_pte)))
3040                ret = VM_FAULT_OOM;
3041            delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3042            goto unlock;
3043        }
3044
3045        /* Had to read the page from swap area: Major fault */
3046        ret = VM_FAULT_MAJOR;
3047        count_vm_event(PGMAJFAULT);
3048        mem_cgroup_count_vm_event(mm, PGMAJFAULT);
3049    } else if (PageHWPoison(page)) {
3050        /*
3051         * hwpoisoned dirty swapcache pages are kept for killing
3052         * owner processes (which may be unknown at hwpoison time)
3053         */
3054        ret = VM_FAULT_HWPOISON;
3055        delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3056        swapcache = page;
3057        goto out_release;
3058    }
3059
3060    swapcache = page;
3061    locked = lock_page_or_retry(page, mm, flags);
3062
3063    delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3064    if (!locked) {
3065        ret |= VM_FAULT_RETRY;
3066        goto out_release;
3067    }
3068
3069    /*
3070     * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
3071     * release the swapcache from under us. The page pin, and pte_same
3072     * test below, are not enough to exclude that. Even if it is still
3073     * swapcache, we need to check that the page's swap has not changed.
3074     */
3075    if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
3076        goto out_page;
3077
3078    page = ksm_might_need_to_copy(page, vma, address);
3079    if (unlikely(!page)) {
3080        ret = VM_FAULT_OOM;
3081        page = swapcache;
3082        goto out_page;
3083    }
3084
3085    if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
3086        ret = VM_FAULT_OOM;
3087        goto out_page;
3088    }
3089
3090    /*
3091     * Back out if somebody else already faulted in this pte.
3092     */
3093    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3094    if (unlikely(!pte_same(*page_table, orig_pte)))
3095        goto out_nomap;
3096
3097    if (unlikely(!PageUptodate(page))) {
3098        ret = VM_FAULT_SIGBUS;
3099        goto out_nomap;
3100    }
3101
3102    /*
3103     * The page isn't present yet, go ahead with the fault.
3104     *
3105     * Be careful about the sequence of operations here.
3106     * To get its accounting right, reuse_swap_page() must be called
3107     * while the page is counted on swap but not yet in mapcount i.e.
3108     * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
3109     * must be called after the swap_free(), or it will never succeed.
3110     * Because delete_from_swap_page() may be called by reuse_swap_page(),
3111     * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
3112     * in page->private. In this case, a record in swap_cgroup is silently
3113     * discarded at swap_free().
3114     */
3115
3116    inc_mm_counter_fast(mm, MM_ANONPAGES);
3117    dec_mm_counter_fast(mm, MM_SWAPENTS);
3118    pte = mk_pte(page, vma->vm_page_prot);
3119    if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
3120        pte = maybe_mkwrite(pte_mkdirty(pte), vma);
3121        flags &= ~FAULT_FLAG_WRITE;
3122        ret |= VM_FAULT_WRITE;
3123        exclusive = 1;
3124    }
3125    flush_icache_page(vma, page);
3126    set_pte_at(mm, address, page_table, pte);
3127    if (page == swapcache)
3128        do_page_add_anon_rmap(page, vma, address, exclusive);
3129    else /* ksm created a completely new copy */
3130        page_add_new_anon_rmap(page, vma, address);
3131    /* It's better to call commit-charge after rmap is established */
3132    mem_cgroup_commit_charge_swapin(page, ptr);
3133
3134    swap_free(entry);
3135    if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
3136        try_to_free_swap(page);
3137    unlock_page(page);
3138    if (page != swapcache) {
3139        /*
3140         * Hold the lock to avoid the swap entry to be reused
3141         * until we take the PT lock for the pte_same() check
3142         * (to avoid false positives from pte_same). For
3143         * further safety release the lock after the swap_free
3144         * so that the swap count won't change under a
3145         * parallel locked swapcache.
3146         */
3147        unlock_page(swapcache);
3148        page_cache_release(swapcache);
3149    }
3150
3151    if (flags & FAULT_FLAG_WRITE) {
3152        ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
3153        if (ret & VM_FAULT_ERROR)
3154            ret &= VM_FAULT_ERROR;
3155        goto out;
3156    }
3157
3158    /* No need to invalidate - it was non-present before */
3159    update_mmu_cache(vma, address, page_table);
3160unlock:
3161    pte_unmap_unlock(page_table, ptl);
3162out:
3163    return ret;
3164out_nomap:
3165    mem_cgroup_cancel_charge_swapin(ptr);
3166    pte_unmap_unlock(page_table, ptl);
3167out_page:
3168    unlock_page(page);
3169out_release:
3170    page_cache_release(page);
3171    if (page != swapcache) {
3172        unlock_page(swapcache);
3173        page_cache_release(swapcache);
3174    }
3175    return ret;
3176}
3177
3178/*
3179 * This is like a special single-page "expand_{down|up}wards()",
3180 * except we must first make sure that 'address{-|+}PAGE_SIZE'
3181 * doesn't hit another vma.
3182 */
3183static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
3184{
3185    address &= PAGE_MASK;
3186    if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
3187        struct vm_area_struct *prev = vma->vm_prev;
3188
3189        /*
3190         * Is there a mapping abutting this one below?
3191         *
3192         * That's only ok if it's the same stack mapping
3193         * that has gotten split..
3194         */
3195        if (prev && prev->vm_end == address)
3196            return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
3197
3198        expand_downwards(vma, address - PAGE_SIZE);
3199    }
3200    if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
3201        struct vm_area_struct *next = vma->vm_next;
3202
3203        /* As VM_GROWSDOWN but s/below/above/ */
3204        if (next && next->vm_start == address + PAGE_SIZE)
3205            return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
3206
3207        expand_upwards(vma, address + PAGE_SIZE);
3208    }
3209    return 0;
3210}
3211
3212/*
3213 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3214 * but allow concurrent faults), and pte mapped but not yet locked.
3215 * We return with mmap_sem still held, but pte unmapped and unlocked.
3216 */
3217static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
3218        unsigned long address, pte_t *page_table, pmd_t *pmd,
3219        unsigned int flags)
3220{
3221    struct page *page;
3222    spinlock_t *ptl;
3223    pte_t entry;
3224
3225    pte_unmap(page_table);
3226
3227    /* Check if we need to add a guard page to the stack */
3228    if (check_stack_guard_page(vma, address) < 0)
3229        return VM_FAULT_SIGBUS;
3230
3231    /* Use the zero-page for reads */
3232    if (!(flags & FAULT_FLAG_WRITE)) {
3233        entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
3234                        vma->vm_page_prot));
3235        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3236        if (!pte_none(*page_table))
3237            goto unlock;
3238        goto setpte;
3239    }
3240
3241    /* Allocate our own private page. */
3242    if (unlikely(anon_vma_prepare(vma)))
3243        goto oom;
3244    page = alloc_zeroed_user_highpage_movable(vma, address);
3245    if (!page)
3246        goto oom;
3247    __SetPageUptodate(page);
3248
3249    if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
3250        goto oom_free_page;
3251
3252    entry = mk_pte(page, vma->vm_page_prot);
3253    if (vma->vm_flags & VM_WRITE)
3254        entry = pte_mkwrite(pte_mkdirty(entry));
3255
3256    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3257    if (!pte_none(*page_table))
3258        goto release;
3259
3260    inc_mm_counter_fast(mm, MM_ANONPAGES);
3261    page_add_new_anon_rmap(page, vma, address);
3262setpte:
3263    set_pte_at(mm, address, page_table, entry);
3264
3265    /* No need to invalidate - it was non-present before */
3266    update_mmu_cache(vma, address, page_table);
3267unlock:
3268    pte_unmap_unlock(page_table, ptl);
3269    return 0;
3270release:
3271    mem_cgroup_uncharge_page(page);
3272    page_cache_release(page);
3273    goto unlock;
3274oom_free_page:
3275    page_cache_release(page);
3276oom:
3277    return VM_FAULT_OOM;
3278}
3279
3280/*
3281 * __do_fault() tries to create a new page mapping. It aggressively
3282 * tries to share with existing pages, but makes a separate copy if
3283 * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
3284 * the next page fault.
3285 *
3286 * As this is called only for pages that do not currently exist, we
3287 * do not need to flush old virtual caches or the TLB.
3288 *
3289 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3290 * but allow concurrent faults), and pte neither mapped nor locked.
3291 * We return with mmap_sem still held, but pte unmapped and unlocked.
3292 */
3293static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3294        unsigned long address, pmd_t *pmd,
3295        pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3296{
3297    pte_t *page_table;
3298    spinlock_t *ptl;
3299    struct page *page;
3300    struct page *cow_page;
3301    pte_t entry;
3302    int anon = 0;
3303    struct page *dirty_page = NULL;
3304    struct vm_fault vmf;
3305    int ret;
3306    int page_mkwrite = 0;
3307
3308    /*
3309     * If we do COW later, allocate page befor taking lock_page()
3310     * on the file cache page. This will reduce lock holding time.
3311     */
3312    if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
3313
3314        if (unlikely(anon_vma_prepare(vma)))
3315            return VM_FAULT_OOM;
3316
3317        cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
3318        if (!cow_page)
3319            return VM_FAULT_OOM;
3320
3321        if (mem_cgroup_newpage_charge(cow_page, mm, GFP_KERNEL)) {
3322            page_cache_release(cow_page);
3323            return VM_FAULT_OOM;
3324        }
3325    } else
3326        cow_page = NULL;
3327
3328    vmf.virtual_address = (void __user *)(address & PAGE_MASK);
3329    vmf.pgoff = pgoff;
3330    vmf.flags = flags;
3331    vmf.page = NULL;
3332
3333    ret = vma->vm_ops->fault(vma, &vmf);
3334    if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
3335                VM_FAULT_RETRY)))
3336        goto uncharge_out;
3337
3338    if (unlikely(PageHWPoison(vmf.page))) {
3339        if (ret & VM_FAULT_LOCKED)
3340            unlock_page(vmf.page);
3341        ret = VM_FAULT_HWPOISON;
3342        goto uncharge_out;
3343    }
3344
3345    /*
3346     * For consistency in subsequent calls, make the faulted page always
3347     * locked.
3348     */
3349    if (unlikely(!(ret & VM_FAULT_LOCKED)))
3350        lock_page(vmf.page);
3351    else
3352        VM_BUG_ON(!PageLocked(vmf.page));
3353
3354    /*
3355     * Should we do an early C-O-W break?
3356     */
3357    page = vmf.page;
3358    if (flags & FAULT_FLAG_WRITE) {
3359        if (!(vma->vm_flags & VM_SHARED)) {
3360            page = cow_page;
3361            anon = 1;
3362            copy_user_highpage(page, vmf.page, address, vma);
3363            __SetPageUptodate(page);
3364        } else {
3365            /*
3366             * If the page will be shareable, see if the backing
3367             * address space wants to know that the page is about
3368             * to become writable
3369             */
3370            if (vma->vm_ops->page_mkwrite) {
3371                int tmp;
3372
3373                unlock_page(page);
3374                vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
3375                tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
3376                if (unlikely(tmp &
3377                      (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
3378                    ret = tmp;
3379                    goto unwritable_page;
3380                }
3381                if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
3382                    lock_page(page);
3383                    if (!page->mapping) {
3384                        ret = 0; /* retry the fault */
3385                        unlock_page(page);
3386                        goto unwritable_page;
3387                    }
3388                } else
3389                    VM_BUG_ON(!PageLocked(page));
3390                page_mkwrite = 1;
3391            }
3392        }
3393
3394    }
3395
3396    page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3397
3398    /*
3399     * This silly early PAGE_DIRTY setting removes a race
3400     * due to the bad i386 page protection. But it's valid
3401     * for other architectures too.
3402     *
3403     * Note that if FAULT_FLAG_WRITE is set, we either now have
3404     * an exclusive copy of the page, or this is a shared mapping,
3405     * so we can make it writable and dirty to avoid having to
3406     * handle that later.
3407     */
3408    /* Only go through if we didn't race with anybody else... */
3409    if (likely(pte_same(*page_table, orig_pte))) {
3410        flush_icache_page(vma, page);
3411        entry = mk_pte(page, vma->vm_page_prot);
3412        if (flags & FAULT_FLAG_WRITE)
3413            entry = maybe_mkwrite(pte_mkdirty(entry), vma);
3414        if (anon) {
3415            inc_mm_counter_fast(mm, MM_ANONPAGES);
3416            page_add_new_anon_rmap(page, vma, address);
3417        } else {
3418            inc_mm_counter_fast(mm, MM_FILEPAGES);
3419            page_add_file_rmap(page);
3420            if (flags & FAULT_FLAG_WRITE) {
3421                dirty_page = page;
3422                get_page(dirty_page);
3423            }
3424        }
3425        set_pte_at(mm, address, page_table, entry);
3426
3427        /* no need to invalidate: a not-present page won't be cached */
3428        update_mmu_cache(vma, address, page_table);
3429    } else {
3430        if (cow_page)
3431            mem_cgroup_uncharge_page(cow_page);
3432        if (anon)
3433            page_cache_release(page);
3434        else
3435            anon = 1; /* no anon but release faulted_page */
3436    }
3437
3438    pte_unmap_unlock(page_table, ptl);
3439
3440    if (dirty_page) {
3441        struct address_space *mapping = page->mapping;
3442        int dirtied = 0;
3443
3444        if (set_page_dirty(dirty_page))
3445            dirtied = 1;
3446        unlock_page(dirty_page);
3447        put_page(dirty_page);
3448        if ((dirtied || page_mkwrite) && mapping) {
3449            /*
3450             * Some device drivers do not set page.mapping but still
3451             * dirty their pages
3452             */
3453            balance_dirty_pages_ratelimited(mapping);
3454        }
3455
3456        /* file_update_time outside page_lock */
3457        if (vma->vm_file && !page_mkwrite)
3458            file_update_time(vma->vm_file);
3459    } else {
3460        unlock_page(vmf.page);
3461        if (anon)
3462            page_cache_release(vmf.page);
3463    }
3464
3465    return ret;
3466
3467unwritable_page:
3468    page_cache_release(page);
3469    return ret;
3470uncharge_out:
3471    /* fs's fault handler get error */
3472    if (cow_page) {
3473        mem_cgroup_uncharge_page(cow_page);
3474        page_cache_release(cow_page);
3475    }
3476    return ret;
3477}
3478
3479static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3480        unsigned long address, pte_t *page_table, pmd_t *pmd,
3481        unsigned int flags, pte_t orig_pte)
3482{
3483    pgoff_t pgoff = (((address & PAGE_MASK)
3484            - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
3485
3486    pte_unmap(page_table);
3487    return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3488}
3489
3490/*
3491 * Fault of a previously existing named mapping. Repopulate the pte
3492 * from the encoded file_pte if possible. This enables swappable
3493 * nonlinear vmas.
3494 *
3495 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3496 * but allow concurrent faults), and pte mapped but not yet locked.
3497 * We return with mmap_sem still held, but pte unmapped and unlocked.
3498 */
3499static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3500        unsigned long address, pte_t *page_table, pmd_t *pmd,
3501        unsigned int flags, pte_t orig_pte)
3502{
3503    pgoff_t pgoff;
3504
3505    flags |= FAULT_FLAG_NONLINEAR;
3506
3507    if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3508        return 0;
3509
3510    if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
3511        /*
3512         * Page table corrupted: show pte and kill process.
3513         */
3514        print_bad_pte(vma, address, orig_pte, NULL);
3515        return VM_FAULT_SIGBUS;
3516    }
3517
3518    pgoff = pte_to_pgoff(orig_pte);
3519    return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3520}
3521
3522int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
3523                unsigned long addr, int current_nid)
3524{
3525    get_page(page);
3526
3527    count_vm_numa_event(NUMA_HINT_FAULTS);
3528    if (current_nid == numa_node_id())
3529        count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
3530
3531    return mpol_misplaced(page, vma, addr);
3532}
3533
3534int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3535           unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)
3536{
3537    struct page *page = NULL;
3538    spinlock_t *ptl;
3539    int current_nid = -1;
3540    int target_nid;
3541    bool migrated = false;
3542
3543    /*
3544    * The "pte" at this point cannot be used safely without
3545    * validation through pte_unmap_same(). It's of NUMA type but
3546    * the pfn may be screwed if the read is non atomic.
3547    *
3548    * ptep_modify_prot_start is not called as this is clearing
3549    * the _PAGE_NUMA bit and it is not really expected that there
3550    * would be concurrent hardware modifications to the PTE.
3551    */
3552    ptl = pte_lockptr(mm, pmd);
3553    spin_lock(ptl);
3554    if (unlikely(!pte_same(*ptep, pte))) {
3555        pte_unmap_unlock(ptep, ptl);
3556        goto out;
3557    }
3558
3559    pte = pte_mknonnuma(pte);
3560    set_pte_at(mm, addr, ptep, pte);
3561    update_mmu_cache(vma, addr, ptep);
3562
3563    page = vm_normal_page(vma, addr, pte);
3564    if (!page) {
3565        pte_unmap_unlock(ptep, ptl);
3566        return 0;
3567    }
3568
3569    current_nid = page_to_nid(page);
3570    target_nid = numa_migrate_prep(page, vma, addr, current_nid);
3571    pte_unmap_unlock(ptep, ptl);
3572    if (target_nid == -1) {
3573        /*
3574         * Account for the fault against the current node if it not
3575         * being replaced regardless of where the page is located.
3576         */
3577        current_nid = numa_node_id();
3578        put_page(page);
3579        goto out;
3580    }
3581
3582    /* Migrate to the requested node */
3583    migrated = migrate_misplaced_page(page, target_nid);
3584    if (migrated)
3585        current_nid = target_nid;
3586
3587out:
3588    if (current_nid != -1)
3589        task_numa_fault(current_nid, 1, migrated);
3590    return 0;
3591}
3592
3593/* NUMA hinting page fault entry point for regular pmds */
3594#ifdef CONFIG_NUMA_BALANCING
3595static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3596             unsigned long addr, pmd_t *pmdp)
3597{
3598    pmd_t pmd;
3599    pte_t *pte, *orig_pte;
3600    unsigned long _addr = addr & PMD_MASK;
3601    unsigned long offset;
3602    spinlock_t *ptl;
3603    bool numa = false;
3604    int local_nid = numa_node_id();
3605
3606    spin_lock(&mm->page_table_lock);
3607    pmd = *pmdp;
3608    if (pmd_numa(pmd)) {
3609        set_pmd_at(mm, _addr, pmdp, pmd_mknonnuma(pmd));
3610        numa = true;
3611    }
3612    spin_unlock(&mm->page_table_lock);
3613
3614    if (!numa)
3615        return 0;
3616
3617    /* we're in a page fault so some vma must be in the range */
3618    BUG_ON(!vma);
3619    BUG_ON(vma->vm_start >= _addr + PMD_SIZE);
3620    offset = max(_addr, vma->vm_start) & ~PMD_MASK;
3621    VM_BUG_ON(offset >= PMD_SIZE);
3622    orig_pte = pte = pte_offset_map_lock(mm, pmdp, _addr, &ptl);
3623    pte += offset >> PAGE_SHIFT;
3624    for (addr = _addr + offset; addr < _addr + PMD_SIZE; pte++, addr += PAGE_SIZE) {
3625        pte_t pteval = *pte;
3626        struct page *page;
3627        int curr_nid = local_nid;
3628        int target_nid;
3629        bool migrated;
3630        if (!pte_present(pteval))
3631            continue;
3632        if (!pte_numa(pteval))
3633            continue;
3634        if (addr >= vma->vm_end) {
3635            vma = find_vma(mm, addr);
3636            /* there's a pte present so there must be a vma */
3637            BUG_ON(!vma);
3638            BUG_ON(addr < vma->vm_start);
3639        }
3640        if (pte_numa(pteval)) {
3641            pteval = pte_mknonnuma(pteval);
3642            set_pte_at(mm, addr, pte, pteval);
3643        }
3644        page = vm_normal_page(vma, addr, pteval);
3645        if (unlikely(!page))
3646            continue;
3647        /* only check non-shared pages */
3648        if (unlikely(page_mapcount(page) != 1))
3649            continue;
3650
3651        /*
3652         * Note that the NUMA fault is later accounted to either
3653         * the node that is currently running or where the page is
3654         * migrated to.
3655         */
3656        curr_nid = local_nid;
3657        target_nid = numa_migrate_prep(page, vma, addr,
3658                           page_to_nid(page));
3659        if (target_nid == -1) {
3660            put_page(page);
3661            continue;
3662        }
3663
3664        /* Migrate to the requested node */
3665        pte_unmap_unlock(pte, ptl);
3666        migrated = migrate_misplaced_page(page, target_nid);
3667        if (migrated)
3668            curr_nid = target_nid;
3669        task_numa_fault(curr_nid, 1, migrated);
3670
3671        pte = pte_offset_map_lock(mm, pmdp, addr, &ptl);
3672    }
3673    pte_unmap_unlock(orig_pte, ptl);
3674
3675    return 0;
3676}
3677#else
3678static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3679             unsigned long addr, pmd_t *pmdp)
3680{
3681    BUG();
3682    return 0;
3683}
3684#endif /* CONFIG_NUMA_BALANCING */
3685
3686/*
3687 * These routines also need to handle stuff like marking pages dirty
3688 * and/or accessed for architectures that don't do it in hardware (most
3689 * RISC architectures). The early dirtying is also good on the i386.
3690 *
3691 * There is also a hook called "update_mmu_cache()" that architectures
3692 * with external mmu caches can use to update those (ie the Sparc or
3693 * PowerPC hashed page tables that act as extended TLBs).
3694 *
3695 * We enter with non-exclusive mmap_sem (to exclude vma changes,
3696 * but allow concurrent faults), and pte mapped but not yet locked.
3697 * We return with mmap_sem still held, but pte unmapped and unlocked.
3698 */
3699int handle_pte_fault(struct mm_struct *mm,
3700             struct vm_area_struct *vma, unsigned long address,
3701             pte_t *pte, pmd_t *pmd, unsigned int flags)
3702{
3703    pte_t entry;
3704    spinlock_t *ptl;
3705
3706    entry = *pte;
3707    if (!pte_present(entry)) {
3708        if (pte_none(entry)) {
3709            if (vma->vm_ops) {
3710                if (likely(vma->vm_ops->fault))
3711                    return do_linear_fault(mm, vma, address,
3712                        pte, pmd, flags, entry);
3713            }
3714            return do_anonymous_page(mm, vma, address,
3715                         pte, pmd, flags);
3716        }
3717        if (pte_file(entry))
3718            return do_nonlinear_fault(mm, vma, address,
3719                    pte, pmd, flags, entry);
3720        return do_swap_page(mm, vma, address,
3721                    pte, pmd, flags, entry);
3722    }
3723
3724    if (pte_numa(entry))
3725        return do_numa_page(mm, vma, address, entry, pte, pmd);
3726
3727    ptl = pte_lockptr(mm, pmd);
3728    spin_lock(ptl);
3729    if (unlikely(!pte_same(*pte, entry)))
3730        goto unlock;
3731    if (flags & FAULT_FLAG_WRITE) {
3732        if (!pte_write(entry))
3733            return do_wp_page(mm, vma, address,
3734                    pte, pmd, ptl, entry);
3735        entry = pte_mkdirty(entry);
3736    }
3737    entry = pte_mkyoung(entry);
3738    if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3739        update_mmu_cache(vma, address, pte);
3740    } else {
3741        /*
3742         * This is needed only for protection faults but the arch code
3743         * is not yet telling us if this is a protection fault or not.
3744         * This still avoids useless tlb flushes for .text page faults
3745         * with threads.
3746         */
3747        if (flags & FAULT_FLAG_WRITE)
3748            flush_tlb_fix_spurious_fault(vma, address);
3749    }
3750unlock:
3751    pte_unmap_unlock(pte, ptl);
3752    return 0;
3753}
3754
3755/*
3756 * By the time we get here, we already hold the mm semaphore
3757 */
3758int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3759        unsigned long address, unsigned int flags)
3760{
3761    pgd_t *pgd;
3762    pud_t *pud;
3763    pmd_t *pmd;
3764    pte_t *pte;
3765
3766    __set_current_state(TASK_RUNNING);
3767
3768    count_vm_event(PGFAULT);
3769    mem_cgroup_count_vm_event(mm, PGFAULT);
3770
3771    /* do counter updates before entering really critical section. */
3772    check_sync_rss_stat(current);
3773
3774    if (unlikely(is_vm_hugetlb_page(vma)))
3775        return hugetlb_fault(mm, vma, address, flags);
3776
3777retry:
3778    pgd = pgd_offset(mm, address);
3779    pud = pud_alloc(mm, pgd, address);
3780    if (!pud)
3781        return VM_FAULT_OOM;
3782    pmd = pmd_alloc(mm, pud, address);
3783    if (!pmd)
3784        return VM_FAULT_OOM;
3785    if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
3786        if (!vma->vm_ops)
3787            return do_huge_pmd_anonymous_page(mm, vma, address,
3788                              pmd, flags);
3789    } else {
3790        pmd_t orig_pmd = *pmd;
3791        int ret;
3792
3793        barrier();
3794        if (pmd_trans_huge(orig_pmd)) {
3795            unsigned int dirty = flags & FAULT_FLAG_WRITE;
3796
3797            /*
3798             * If the pmd is splitting, return and retry the
3799             * the fault. Alternative: wait until the split
3800             * is done, and goto retry.
3801             */
3802            if (pmd_trans_splitting(orig_pmd))
3803                return 0;
3804
3805            if (pmd_numa(orig_pmd))
3806                return do_huge_pmd_numa_page(mm, vma, address,
3807                                 orig_pmd, pmd);
3808
3809            if (dirty && !pmd_write(orig_pmd)) {
3810                ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
3811                              orig_pmd);
3812                /*
3813                 * If COW results in an oom, the huge pmd will
3814                 * have been split, so retry the fault on the
3815                 * pte for a smaller charge.
3816                 */
3817                if (unlikely(ret & VM_FAULT_OOM))
3818                    goto retry;
3819                return ret;
3820            } else {
3821                huge_pmd_set_accessed(mm, vma, address, pmd,
3822                              orig_pmd, dirty);
3823            }
3824
3825            return 0;
3826        }
3827    }
3828
3829    if (pmd_numa(*pmd))
3830        return do_pmd_numa_page(mm, vma, address, pmd);
3831
3832    /*
3833     * Use __pte_alloc instead of pte_alloc_map, because we can't
3834     * run pte_offset_map on the pmd, if an huge pmd could
3835     * materialize from under us from a different thread.
3836     */
3837    if (unlikely(pmd_none(*pmd)) &&
3838        unlikely(__pte_alloc(mm, vma, pmd, address)))
3839        return VM_FAULT_OOM;
3840    /* if an huge pmd materialized from under us just retry later */
3841    if (unlikely(pmd_trans_huge(*pmd)))
3842        return 0;
3843    /*
3844     * A regular pmd is established and it can't morph into a huge pmd
3845     * from under us anymore at this point because we hold the mmap_sem
3846     * read mode and khugepaged takes it in write mode. So now it's
3847     * safe to run pte_offset_map().
3848     */
3849    pte = pte_offset_map(pmd, address);
3850
3851    return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3852}
3853
3854#ifndef __PAGETABLE_PUD_FOLDED
3855/*
3856 * Allocate page upper directory.
3857 * We've already handled the fast-path in-line.
3858 */
3859int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3860{
3861    pud_t *new = pud_alloc_one(mm, address);
3862    if (!new)
3863        return -ENOMEM;
3864
3865    smp_wmb(); /* See comment in __pte_alloc */
3866
3867    spin_lock(&mm->page_table_lock);
3868    if (pgd_present(*pgd)) /* Another has populated it */
3869        pud_free(mm, new);
3870    else
3871        pgd_populate(mm, pgd, new);
3872    spin_unlock(&mm->page_table_lock);
3873    return 0;
3874}
3875#endif /* __PAGETABLE_PUD_FOLDED */
3876
3877#ifndef __PAGETABLE_PMD_FOLDED
3878/*
3879 * Allocate page middle directory.
3880 * We've already handled the fast-path in-line.
3881 */
3882int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3883{
3884    pmd_t *new = pmd_alloc_one(mm, address);
3885    if (!new)
3886        return -ENOMEM;
3887
3888    smp_wmb(); /* See comment in __pte_alloc */
3889
3890    spin_lock(&mm->page_table_lock);
3891#ifndef __ARCH_HAS_4LEVEL_HACK
3892    if (pud_present(*pud)) /* Another has populated it */
3893        pmd_free(mm, new);
3894    else
3895        pud_populate(mm, pud, new);
3896#else
3897    if (pgd_present(*pud)) /* Another has populated it */
3898        pmd_free(mm, new);
3899    else
3900        pgd_populate(mm, pud, new);
3901#endif /* __ARCH_HAS_4LEVEL_HACK */
3902    spin_unlock(&mm->page_table_lock);
3903    return 0;
3904}
3905#endif /* __PAGETABLE_PMD_FOLDED */
3906
3907#if !defined(__HAVE_ARCH_GATE_AREA)
3908
3909#if defined(AT_SYSINFO_EHDR)
3910static struct vm_area_struct gate_vma;
3911
3912static int __init gate_vma_init(void)
3913{
3914    gate_vma.vm_mm = NULL;
3915    gate_vma.vm_start = FIXADDR_USER_START;
3916    gate_vma.vm_end = FIXADDR_USER_END;
3917    gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
3918    gate_vma.vm_page_prot = __P101;
3919
3920    return 0;
3921}
3922__initcall(gate_vma_init);
3923#endif
3924
3925struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
3926{
3927#ifdef AT_SYSINFO_EHDR
3928    return &gate_vma;
3929#else
3930    return NULL;
3931#endif
3932}
3933
3934int in_gate_area_no_mm(unsigned long addr)
3935{
3936#ifdef AT_SYSINFO_EHDR
3937    if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
3938        return 1;
3939#endif
3940    return 0;
3941}
3942
3943#endif /* __HAVE_ARCH_GATE_AREA */
3944
3945static int __follow_pte(struct mm_struct *mm, unsigned long address,
3946        pte_t **ptepp, spinlock_t **ptlp)
3947{
3948    pgd_t *pgd;
3949    pud_t *pud;
3950    pmd_t *pmd;
3951    pte_t *ptep;
3952
3953    pgd = pgd_offset(mm, address);
3954    if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3955        goto out;
3956
3957    pud = pud_offset(pgd, address);
3958    if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3959        goto out;
3960
3961    pmd = pmd_offset(pud, address);
3962    VM_BUG_ON(pmd_trans_huge(*pmd));
3963    if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3964        goto out;
3965
3966    /* We cannot handle huge page PFN maps. Luckily they don't exist. */
3967    if (pmd_huge(*pmd))
3968        goto out;
3969
3970    ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3971    if (!ptep)
3972        goto out;
3973    if (!pte_present(*ptep))
3974        goto unlock;
3975    *ptepp = ptep;
3976    return 0;
3977unlock:
3978    pte_unmap_unlock(ptep, *ptlp);
3979out:
3980    return -EINVAL;
3981}
3982
3983static inline int follow_pte(struct mm_struct *mm, unsigned long address,
3984                 pte_t **ptepp, spinlock_t **ptlp)
3985{
3986    int res;
3987
3988    /* (void) is needed to make gcc happy */
3989    (void) __cond_lock(*ptlp,
3990               !(res = __follow_pte(mm, address, ptepp, ptlp)));
3991    return res;
3992}
3993
3994/**
3995 * follow_pfn - look up PFN at a user virtual address
3996 * @vma: memory mapping
3997 * @address: user virtual address
3998 * @pfn: location to store found PFN
3999 *
4000 * Only IO mappings and raw PFN mappings are allowed.
4001 *
4002 * Returns zero and the pfn at @pfn on success, -ve otherwise.
4003 */
4004int follow_pfn(struct vm_area_struct *vma, unsigned long address,
4005    unsigned long *pfn)
4006{
4007    int ret = -EINVAL;
4008    spinlock_t *ptl;
4009    pte_t *ptep;
4010
4011    if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
4012        return ret;
4013
4014    ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
4015    if (ret)
4016        return ret;
4017    *pfn = pte_pfn(*ptep);
4018    pte_unmap_unlock(ptep, ptl);
4019    return 0;
4020}
4021EXPORT_SYMBOL(follow_pfn);
4022
4023#ifdef CONFIG_HAVE_IOREMAP_PROT
4024int follow_phys(struct vm_area_struct *vma,
4025        unsigned long address, unsigned int flags,
4026        unsigned long *prot, resource_size_t *phys)
4027{
4028    int ret = -EINVAL;
4029    pte_t *ptep, pte;
4030    spinlock_t *ptl;
4031
4032    if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
4033        goto out;
4034
4035    if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
4036        goto out;
4037    pte = *ptep;
4038
4039    if ((flags & FOLL_WRITE) && !pte_write(pte))
4040        goto unlock;
4041
4042    *prot = pgprot_val(pte_pgprot(pte));
4043    *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
4044
4045    ret = 0;
4046unlock:
4047    pte_unmap_unlock(ptep, ptl);
4048out:
4049    return ret;
4050}
4051
4052int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
4053            void *buf, int len, int write)
4054{
4055    resource_size_t phys_addr;
4056    unsigned long prot = 0;
4057    void __iomem *maddr;
4058    int offset = addr & (PAGE_SIZE-1);
4059
4060    if (follow_phys(vma, addr, write, &prot, &phys_addr))
4061        return -EINVAL;
4062
4063    maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
4064    if (write)
4065        memcpy_toio(maddr + offset, buf, len);
4066    else
4067        memcpy_fromio(buf, maddr + offset, len);
4068    iounmap(maddr);
4069
4070    return len;
4071}
4072#endif
4073
4074/*
4075 * Access another process' address space as given in mm. If non-NULL, use the
4076 * given task for page fault accounting.
4077 */
4078static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
4079        unsigned long addr, void *buf, int len, int write)
4080{
4081    struct vm_area_struct *vma;
4082    void *old_buf = buf;
4083
4084    down_read(&mm->mmap_sem);
4085    /* ignore errors, just check how much was successfully transferred */
4086    while (len) {
4087        int bytes, ret, offset;
4088        void *maddr;
4089        struct page *page = NULL;
4090
4091        ret = get_user_pages(tsk, mm, addr, 1,
4092                write, 1, &page, &vma);
4093        if (ret <= 0) {
4094            /*
4095             * Check if this is a VM_IO | VM_PFNMAP VMA, which
4096             * we can access using slightly different code.
4097             */
4098#ifdef CONFIG_HAVE_IOREMAP_PROT
4099            vma = find_vma(mm, addr);
4100            if (!vma || vma->vm_start > addr)
4101                break;
4102            if (vma->vm_ops && vma->vm_ops->access)
4103                ret = vma->vm_ops->access(vma, addr, buf,
4104                              len, write);
4105            if (ret <= 0)
4106#endif
4107                break;
4108            bytes = ret;
4109        } else {
4110            bytes = len;
4111            offset = addr & (PAGE_SIZE-1);
4112            if (bytes > PAGE_SIZE-offset)
4113                bytes = PAGE_SIZE-offset;
4114
4115            maddr = kmap(page);
4116            if (write) {
4117                copy_to_user_page(vma, page, addr,
4118                          maddr + offset, buf, bytes);
4119                set_page_dirty_lock(page);
4120            } else {
4121                copy_from_user_page(vma, page, addr,
4122                            buf, maddr + offset, bytes);
4123            }
4124            kunmap(page);
4125            page_cache_release(page);
4126        }
4127        len -= bytes;
4128        buf += bytes;
4129        addr += bytes;
4130    }
4131    up_read(&mm->mmap_sem);
4132
4133    return buf - old_buf;
4134}
4135
4136/**
4137 * access_remote_vm - access another process' address space
4138 * @mm: the mm_struct of the target address space
4139 * @addr: start address to access
4140 * @buf: source or destination buffer
4141 * @len: number of bytes to transfer
4142 * @write: whether the access is a write
4143 *
4144 * The caller must hold a reference on @mm.
4145 */
4146int access_remote_vm(struct mm_struct *mm, unsigned long addr,
4147        void *buf, int len, int write)
4148{
4149    return __access_remote_vm(NULL, mm, addr, buf, len, write);
4150}
4151
4152/*
4153 * Access another process' address space.
4154 * Source/target buffer must be kernel space,
4155 * Do not walk the page table directly, use get_user_pages
4156 */
4157int access_process_vm(struct task_struct *tsk, unsigned long addr,
4158        void *buf, int len, int write)
4159{
4160    struct mm_struct *mm;
4161    int ret;
4162
4163    mm = get_task_mm(tsk);
4164    if (!mm)
4165        return 0;
4166
4167    ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
4168    mmput(mm);
4169
4170    return ret;
4171}
4172
4173/*
4174 * Print the name of a VMA.
4175 */
4176void print_vma_addr(char *prefix, unsigned long ip)
4177{
4178    struct mm_struct *mm = current->mm;
4179    struct vm_area_struct *vma;
4180
4181    /*
4182     * Do not print if we are in atomic
4183     * contexts (in exception stacks, etc.):
4184     */
4185    if (preempt_count())
4186        return;
4187
4188    down_read(&mm->mmap_sem);
4189    vma = find_vma(mm, ip);
4190    if (vma && vma->vm_file) {
4191        struct file *f = vma->vm_file;
4192        char *buf = (char *)__get_free_page(GFP_KERNEL);
4193        if (buf) {
4194            char *p;
4195
4196            p = d_path(&f->f_path, buf, PAGE_SIZE);
4197            if (IS_ERR(p))
4198                p = "?";
4199            printk("%s%s[%lx+%lx]", prefix, kbasename(p),
4200                    vma->vm_start,
4201                    vma->vm_end - vma->vm_start);
4202            free_page((unsigned long)buf);
4203        }
4204    }
4205    up_read(&mm->mmap_sem);
4206}
4207
4208#ifdef CONFIG_PROVE_LOCKING
4209void might_fault(void)
4210{
4211    /*
4212     * Some code (nfs/sunrpc) uses socket ops on kernel memory while
4213     * holding the mmap_sem, this is safe because kernel memory doesn't
4214     * get paged out, therefore we'll never actually fault, and the
4215     * below annotations will generate false positives.
4216     */
4217    if (segment_eq(get_fs(), KERNEL_DS))
4218        return;
4219
4220    might_sleep();
4221    /*
4222     * it would be nicer only to annotate paths which are not under
4223     * pagefault_disable, however that requires a larger audit and
4224     * providing helpers like get_user_atomic.
4225     */
4226    if (!in_atomic() && current->mm)
4227        might_lock_read(&current->mm->mmap_sem);
4228}
4229EXPORT_SYMBOL(might_fault);
4230#endif
4231
4232#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
4233static void clear_gigantic_page(struct page *page,
4234                unsigned long addr,
4235                unsigned int pages_per_huge_page)
4236{
4237    int i;
4238    struct page *p = page;
4239
4240    might_sleep();
4241    for (i = 0; i < pages_per_huge_page;
4242         i++, p = mem_map_next(p, page, i)) {
4243        cond_resched();
4244        clear_user_highpage(p, addr + i * PAGE_SIZE);
4245    }
4246}
4247void clear_huge_page(struct page *page,
4248             unsigned long addr, unsigned int pages_per_huge_page)
4249{
4250    int i;
4251
4252    if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4253        clear_gigantic_page(page, addr, pages_per_huge_page);
4254        return;
4255    }
4256
4257    might_sleep();
4258    for (i = 0; i < pages_per_huge_page; i++) {
4259        cond_resched();
4260        clear_user_highpage(page + i, addr + i * PAGE_SIZE);
4261    }
4262}
4263
4264static void copy_user_gigantic_page(struct page *dst, struct page *src,
4265                    unsigned long addr,
4266                    struct vm_area_struct *vma,
4267                    unsigned int pages_per_huge_page)
4268{
4269    int i;
4270    struct page *dst_base = dst;
4271    struct page *src_base = src;
4272
4273    for (i = 0; i < pages_per_huge_page; ) {
4274        cond_resched();
4275        copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
4276
4277        i++;
4278        dst = mem_map_next(dst, dst_base, i);
4279        src = mem_map_next(src, src_base, i);
4280    }
4281}
4282
4283void copy_user_huge_page(struct page *dst, struct page *src,
4284             unsigned long addr, struct vm_area_struct *vma,
4285             unsigned int pages_per_huge_page)
4286{
4287    int i;
4288
4289    if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4290        copy_user_gigantic_page(dst, src, addr, vma,
4291                    pages_per_huge_page);
4292        return;
4293    }
4294
4295    might_sleep();
4296    for (i = 0; i < pages_per_huge_page; i++) {
4297        cond_resched();
4298        copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
4299    }
4300}
4301#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
4302

Archive Download this file



interactive