mmap.c 71.1 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
/*
 * mm/mmap.c
 *
 * Written by obz.
 *
Alan Cox's avatar
Alan Cox committed
6
 * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
Linus Torvalds's avatar
Linus Torvalds committed
7
8
9
 */

#include <linux/slab.h>
Alexey Dobriyan's avatar
Alexey Dobriyan committed
10
#include <linux/backing-dev.h>
Linus Torvalds's avatar
Linus Torvalds committed
11
12
13
14
15
16
#include <linux/mm.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
17
#include <linux/capability.h>
Linus Torvalds's avatar
Linus Torvalds committed
18
19
20
21
22
23
24
#include <linux/init.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <linux/profile.h>
25
#include <linux/export.h>
Linus Torvalds's avatar
Linus Torvalds committed
26
27
28
#include <linux/mount.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
Andrea Arcangeli's avatar
Andrea Arcangeli committed
29
#include <linux/mmu_notifier.h>
30
#include <linux/perf_event.h>
Al Viro's avatar
Al Viro committed
31
#include <linux/audit.h>
Andrea Arcangeli's avatar
Andrea Arcangeli committed
32
#include <linux/khugepaged.h>
33
#include <linux/uprobes.h>
Linus Torvalds's avatar
Linus Torvalds committed
34
35
36
37

#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/tlb.h>
38
#include <asm/mmu_context.h>
Linus Torvalds's avatar
Linus Torvalds committed
39

40
41
#include "internal.h"

42
43
44
45
#ifndef arch_mmap_check
#define arch_mmap_check(addr, len, flags)	(0)
#endif

46
47
48
49
#ifndef arch_rebalance_pgtables
#define arch_rebalance_pgtables(addr, len)		(addr)
#endif

50
51
52
53
static void unmap_region(struct mm_struct *mm,
		struct vm_area_struct *vma, struct vm_area_struct *prev,
		unsigned long start, unsigned long end);

Linus Torvalds's avatar
Linus Torvalds committed
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
/*
 * WARNING: the debugging will use recursive algorithms so never enable this
 * unless you know what you are doing.
 */
#undef DEBUG_MM_RB

/* description of effects of mapping type and prot in current implementation.
 * this is due to the limited x86 page protection hardware.  The expected
 * behavior is in parens:
 *
 * map_type	prot
 *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
 * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
 *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
 *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
 *		
 * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
 *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
 *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
 *
 */
pgprot_t protection_map[16] = {
	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
};

80
81
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
82
83
84
	return __pgprot(pgprot_val(protection_map[vm_flags &
				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
			pgprot_val(arch_vm_get_page_prot(vm_flags)));
85
86
87
}
EXPORT_SYMBOL(vm_get_page_prot);

88
89
int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;  /* heuristic overcommit */
int sysctl_overcommit_ratio __read_mostly = 50;	/* default is 50% */
90
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
91
92
93
94
95
/*
 * Make sure vm_committed_as in one cacheline and not cacheline shared with
 * other variables. It can be updated by several CPUs frequently.
 */
struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
Linus Torvalds's avatar
Linus Torvalds committed
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 0 means there is enough memory for the allocation to
 * succeed and -ENOMEM implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 *
 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 *
 * Note this is a helper function intended to be used by LSMs which
 * wish to use this logic.
 */
113
int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
Linus Torvalds's avatar
Linus Torvalds committed
114
115
116
117
118
119
120
121
122
123
124
125
{
	unsigned long free, allowed;

	vm_acct_memory(pages);

	/*
	 * Sometimes we want to use more memory than we have
	 */
	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
		return 0;

	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
126
127
128
129
130
131
132
133
134
135
		free = global_page_state(NR_FREE_PAGES);
		free += global_page_state(NR_FILE_PAGES);

		/*
		 * shmem pages shouldn't be counted as free in this
		 * case, they can't be purged, only swapped out, and
		 * that won't affect the overall amount of available
		 * memory in the system.
		 */
		free -= global_page_state(NR_SHMEM);
Linus Torvalds's avatar
Linus Torvalds committed
136
137
138
139
140
141
142
143
144

		free += nr_swap_pages;

		/*
		 * Any slabs which are created with the
		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
		 * which are reclaimable, under pressure.  The dentry
		 * cache and most inode caches should fall into this
		 */
145
		free += global_page_state(NR_SLAB_RECLAIMABLE);
Linus Torvalds's avatar
Linus Torvalds committed
146

147
148
149
		/*
		 * Leave reserved pages. The pages are not for anonymous pages.
		 */
150
		if (free <= totalreserve_pages)
151
152
			goto error;
		else
153
			free -= totalreserve_pages;
154
155
156
157

		/*
		 * Leave the last 3% for root
		 */
Linus Torvalds's avatar
Linus Torvalds committed
158
		if (!cap_sys_admin)
159
			free -= free / 32;
Linus Torvalds's avatar
Linus Torvalds committed
160
161
162

		if (free > pages)
			return 0;
163
164

		goto error;
Linus Torvalds's avatar
Linus Torvalds committed
165
166
167
168
169
170
171
172
173
174
175
176
177
	}

	allowed = (totalram_pages - hugetlb_total_pages())
	       	* sysctl_overcommit_ratio / 100;
	/*
	 * Leave the last 3% for root
	 */
	if (!cap_sys_admin)
		allowed -= allowed / 32;
	allowed += total_swap_pages;

	/* Don't let a single process grow too big:
	   leave 3% of the size of this process for other processes */
Alan Cox's avatar
Alan Cox committed
178
179
	if (mm)
		allowed -= mm->total_vm / 32;
Linus Torvalds's avatar
Linus Torvalds committed
180

181
	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
Linus Torvalds's avatar
Linus Torvalds committed
182
		return 0;
183
error:
Linus Torvalds's avatar
Linus Torvalds committed
184
185
186
187
188
189
	vm_unacct_memory(pages);

	return -ENOMEM;
}

/*
190
 * Requires inode->i_mapping->i_mmap_mutex
Linus Torvalds's avatar
Linus Torvalds committed
191
192
193
194
195
 */
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
		struct file *file, struct address_space *mapping)
{
	if (vma->vm_flags & VM_DENYWRITE)
196
		atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
Linus Torvalds's avatar
Linus Torvalds committed
197
198
199
200
201
	if (vma->vm_flags & VM_SHARED)
		mapping->i_mmap_writable--;

	flush_dcache_mmap_lock(mapping);
	if (unlikely(vma->vm_flags & VM_NONLINEAR))
202
		list_del_init(&vma->shared.nonlinear);
Linus Torvalds's avatar
Linus Torvalds committed
203
	else
204
		vma_interval_tree_remove(vma, &mapping->i_mmap);
Linus Torvalds's avatar
Linus Torvalds committed
205
206
207
208
	flush_dcache_mmap_unlock(mapping);
}

/*
209
 * Unlink a file-based vm structure from its interval tree, to hide
210
 * vma from rmap and vmtruncate before freeing its page tables.
Linus Torvalds's avatar
Linus Torvalds committed
211
 */
212
void unlink_file_vma(struct vm_area_struct *vma)
Linus Torvalds's avatar
Linus Torvalds committed
213
214
215
216
217
{
	struct file *file = vma->vm_file;

	if (file) {
		struct address_space *mapping = file->f_mapping;
218
		mutex_lock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
219
		__remove_shared_vm_struct(vma, file, mapping);
220
		mutex_unlock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
221
	}
222
223
224
225
226
227
228
229
230
231
}

/*
 * Close a vm structure and free it, returning the next.
 */
static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
{
	struct vm_area_struct *next = vma->vm_next;

	might_sleep();
Linus Torvalds's avatar
Linus Torvalds committed
232
233
	if (vma->vm_ops && vma->vm_ops->close)
		vma->vm_ops->close(vma);
234
	if (vma->vm_file)
235
		fput(vma->vm_file);
236
	mpol_put(vma_policy(vma));
Linus Torvalds's avatar
Linus Torvalds committed
237
	kmem_cache_free(vm_area_cachep, vma);
238
	return next;
Linus Torvalds's avatar
Linus Torvalds committed
239
240
}

241
242
static unsigned long do_brk(unsigned long addr, unsigned long len);

243
SYSCALL_DEFINE1(brk, unsigned long, brk)
Linus Torvalds's avatar
Linus Torvalds committed
244
245
246
247
{
	unsigned long rlim, retval;
	unsigned long newbrk, oldbrk;
	struct mm_struct *mm = current->mm;
248
	unsigned long min_brk;
Linus Torvalds's avatar
Linus Torvalds committed
249
250
251

	down_write(&mm->mmap_sem);

252
#ifdef CONFIG_COMPAT_BRK
253
254
255
256
257
	/*
	 * CONFIG_COMPAT_BRK can still be overridden by setting
	 * randomize_va_space to 2, which will still cause mm->start_brk
	 * to be arbitrarily shifted
	 */
258
	if (current->brk_randomized)
259
260
261
		min_brk = mm->start_brk;
	else
		min_brk = mm->end_data;
262
263
264
265
#else
	min_brk = mm->start_brk;
#endif
	if (brk < min_brk)
Linus Torvalds's avatar
Linus Torvalds committed
266
		goto out;
Ram Gupta's avatar
Ram Gupta committed
267
268
269
270
271
272
273

	/*
	 * Check against rlimit here. If this check is done later after the test
	 * of oldbrk with newbrk then it can escape the test and let the data
	 * segment grow beyond its set limit the in case where the limit is
	 * not page aligned -Ram Gupta
	 */
Jiri Slaby's avatar
Jiri Slaby committed
274
	rlim = rlimit(RLIMIT_DATA);
Jiri Kosina's avatar
Jiri Kosina committed
275
276
	if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
			(mm->end_data - mm->start_data) > rlim)
Ram Gupta's avatar
Ram Gupta committed
277
278
		goto out;

Linus Torvalds's avatar
Linus Torvalds committed
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(mm->brk);
	if (oldbrk == newbrk)
		goto set_brk;

	/* Always allow shrinking brk. */
	if (brk <= mm->brk) {
		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
			goto set_brk;
		goto out;
	}

	/* Check against existing mmap mappings. */
	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;

	/* Ok, looks good - let it rip. */
	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
		goto out;
set_brk:
	mm->brk = brk;
out:
	retval = mm->brk;
	up_write(&mm->mmap_sem);
	return retval;
}

#ifdef DEBUG_MM_RB
static int browse_rb(struct rb_root *root)
{
	int i = 0, j;
	struct rb_node *nd, *pn = NULL;
	unsigned long prev = 0, pend = 0;

	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
		struct vm_area_struct *vma;
		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
		if (vma->vm_start < prev)
			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
		if (vma->vm_start < pend)
			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
		if (vma->vm_start > vma->vm_end)
			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
		i++;
		pn = nd;
David Miller's avatar
David Miller committed
324
325
		prev = vma->vm_start;
		pend = vma->vm_end;
Linus Torvalds's avatar
Linus Torvalds committed
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
	}
	j = 0;
	for (nd = pn; nd; nd = rb_prev(nd)) {
		j++;
	}
	if (i != j)
		printk("backwards %d, forwards %d\n", j, i), i = 0;
	return i;
}

void validate_mm(struct mm_struct *mm)
{
	int bug = 0;
	int i = 0;
	struct vm_area_struct *tmp = mm->mmap;
	while (tmp) {
		tmp = tmp->vm_next;
		i++;
	}
	if (i != mm->map_count)
		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
	i = browse_rb(&mm->mm_rb);
	if (i != mm->map_count)
		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
350
	BUG_ON(bug);
Linus Torvalds's avatar
Linus Torvalds committed
351
352
353
354
355
}
#else
#define validate_mm(mm) do { } while (0)
#endif

356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
/*
 * vma has some anon_vma assigned, and is already inserted on that
 * anon_vma's interval trees.
 *
 * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
 * vma must be removed from the anon_vma's interval trees using
 * anon_vma_interval_tree_pre_update_vma().
 *
 * After the update, the vma will be reinserted using
 * anon_vma_interval_tree_post_update_vma().
 *
 * The entire update must be protected by exclusive mmap_sem and by
 * the root anon_vma's mutex.
 */
static inline void
anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
{
	struct anon_vma_chain *avc;

	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
		anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
}

static inline void
anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
{
	struct anon_vma_chain *avc;

	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
		anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
}

388
389
390
static int find_vma_links(struct mm_struct *mm, unsigned long addr,
		unsigned long end, struct vm_area_struct **pprev,
		struct rb_node ***rb_link, struct rb_node **rb_parent)
Linus Torvalds's avatar
Linus Torvalds committed
391
{
392
	struct rb_node **__rb_link, *__rb_parent, *rb_prev;
Linus Torvalds's avatar
Linus Torvalds committed
393
394
395
396
397
398
399
400
401
402
403

	__rb_link = &mm->mm_rb.rb_node;
	rb_prev = __rb_parent = NULL;

	while (*__rb_link) {
		struct vm_area_struct *vma_tmp;

		__rb_parent = *__rb_link;
		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);

		if (vma_tmp->vm_end > addr) {
404
405
406
			/* Fail if an existing vma overlaps the area */
			if (vma_tmp->vm_start < end)
				return -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
407
408
409
410
411
412
413
414
415
416
417
418
			__rb_link = &__rb_parent->rb_left;
		} else {
			rb_prev = __rb_parent;
			__rb_link = &__rb_parent->rb_right;
		}
	}

	*pprev = NULL;
	if (rb_prev)
		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
	*rb_link = __rb_link;
	*rb_parent = __rb_parent;
419
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
420
421
422
423
424
425
426
427
428
}

void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
		struct rb_node **rb_link, struct rb_node *rb_parent)
{
	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
}

429
static void __vma_link_file(struct vm_area_struct *vma)
Linus Torvalds's avatar
Linus Torvalds committed
430
{
ZhenwenXu's avatar
ZhenwenXu committed
431
	struct file *file;
Linus Torvalds's avatar
Linus Torvalds committed
432
433
434
435
436
437

	file = vma->vm_file;
	if (file) {
		struct address_space *mapping = file->f_mapping;

		if (vma->vm_flags & VM_DENYWRITE)
438
			atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
Linus Torvalds's avatar
Linus Torvalds committed
439
440
441
442
443
444
445
		if (vma->vm_flags & VM_SHARED)
			mapping->i_mmap_writable++;

		flush_dcache_mmap_lock(mapping);
		if (unlikely(vma->vm_flags & VM_NONLINEAR))
			vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
		else
446
			vma_interval_tree_insert(vma, &mapping->i_mmap);
Linus Torvalds's avatar
Linus Torvalds committed
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
		flush_dcache_mmap_unlock(mapping);
	}
}

static void
__vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
	struct vm_area_struct *prev, struct rb_node **rb_link,
	struct rb_node *rb_parent)
{
	__vma_link_list(mm, vma, prev, rb_parent);
	__vma_link_rb(mm, vma, rb_link, rb_parent);
}

static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
			struct vm_area_struct *prev, struct rb_node **rb_link,
			struct rb_node *rb_parent)
{
	struct address_space *mapping = NULL;

	if (vma->vm_file)
		mapping = vma->vm_file->f_mapping;

469
	if (mapping)
470
		mutex_lock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
471
472
473
474
475

	__vma_link(mm, vma, prev, rb_link, rb_parent);
	__vma_link_file(vma);

	if (mapping)
476
		mutex_unlock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
477
478
479
480
481
482

	mm->map_count++;
	validate_mm(mm);
}

/*
483
 * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
484
 * mm's list and rbtree.  It has already been inserted into the interval tree.
Linus Torvalds's avatar
Linus Torvalds committed
485
 */
ZhenwenXu's avatar
ZhenwenXu committed
486
static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
Linus Torvalds's avatar
Linus Torvalds committed
487
{
488
	struct vm_area_struct *prev;
ZhenwenXu's avatar
ZhenwenXu committed
489
	struct rb_node **rb_link, *rb_parent;
Linus Torvalds's avatar
Linus Torvalds committed
490

491
492
493
	if (find_vma_links(mm, vma->vm_start, vma->vm_end,
			   &prev, &rb_link, &rb_parent))
		BUG();
Linus Torvalds's avatar
Linus Torvalds committed
494
495
496
497
498
499
500
501
	__vma_link(mm, vma, prev, rb_link, rb_parent);
	mm->map_count++;
}

static inline void
__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
		struct vm_area_struct *prev)
{
502
503
504
505
506
	struct vm_area_struct *next = vma->vm_next;

	prev->vm_next = next;
	if (next)
		next->vm_prev = prev;
Linus Torvalds's avatar
Linus Torvalds committed
507
508
509
510
511
512
513
514
515
516
517
518
	rb_erase(&vma->vm_rb, &mm->mm_rb);
	if (mm->mmap_cache == vma)
		mm->mmap_cache = prev;
}

/*
 * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
 * is already present in an i_mmap tree without adjusting the tree.
 * The following helper function should be used when such adjustments
 * are necessary.  The "insert" vma (if any) is to be inserted
 * before we drop the necessary locks.
 */
519
int vma_adjust(struct vm_area_struct *vma, unsigned long start,
Linus Torvalds's avatar
Linus Torvalds committed
520
521
522
523
524
525
	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
{
	struct mm_struct *mm = vma->vm_mm;
	struct vm_area_struct *next = vma->vm_next;
	struct vm_area_struct *importer = NULL;
	struct address_space *mapping = NULL;
526
	struct rb_root *root = NULL;
527
	struct anon_vma *anon_vma = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
528
529
530
531
532
	struct file *file = vma->vm_file;
	long adjust_next = 0;
	int remove_next = 0;

	if (next && !insert) {
533
534
		struct vm_area_struct *exporter = NULL;

Linus Torvalds's avatar
Linus Torvalds committed
535
536
537
538
539
540
541
		if (end >= next->vm_end) {
			/*
			 * vma expands, overlapping all the next, and
			 * perhaps the one after too (mprotect case 6).
			 */
again:			remove_next = 1 + (end > next->vm_end);
			end = next->vm_end;
542
			exporter = next;
Linus Torvalds's avatar
Linus Torvalds committed
543
544
545
546
547
548
549
			importer = vma;
		} else if (end > next->vm_start) {
			/*
			 * vma expands, overlapping part of the next:
			 * mprotect case 5 shifting the boundary up.
			 */
			adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
550
			exporter = next;
Linus Torvalds's avatar
Linus Torvalds committed
551
552
553
554
555
556
557
558
			importer = vma;
		} else if (end < vma->vm_end) {
			/*
			 * vma shrinks, and !insert tells it's not
			 * split_vma inserting another: so it must be
			 * mprotect case 4 shifting the boundary down.
			 */
			adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
559
			exporter = vma;
Linus Torvalds's avatar
Linus Torvalds committed
560
561
562
			importer = next;
		}

563
564
565
566
567
		/*
		 * Easily overlooked: when mprotect shifts the boundary,
		 * make sure the expanding vma has anon_vma set if the
		 * shrinking vma had, to cover any anon pages imported.
		 */
568
569
		if (exporter && exporter->anon_vma && !importer->anon_vma) {
			if (anon_vma_clone(importer, exporter))
570
				return -ENOMEM;
571
			importer->anon_vma = exporter->anon_vma;
572
573
574
		}
	}

Linus Torvalds's avatar
Linus Torvalds committed
575
576
	if (file) {
		mapping = file->f_mapping;
577
		if (!(vma->vm_flags & VM_NONLINEAR)) {
Linus Torvalds's avatar
Linus Torvalds committed
578
			root = &mapping->i_mmap;
579
			uprobe_munmap(vma, vma->vm_start, vma->vm_end);
580
581

			if (adjust_next)
582
583
				uprobe_munmap(next, next->vm_start,
							next->vm_end);
584
585
		}

586
		mutex_lock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
587
588
		if (insert) {
			/*
589
			 * Put into interval tree now, so instantiated pages
Linus Torvalds's avatar
Linus Torvalds committed
590
591
592
593
594
595
596
597
			 * are visible to arm/parisc __flush_dcache_page
			 * throughout; but we cannot insert into address
			 * space until vma start or end is updated.
			 */
			__vma_link_file(insert);
		}
	}

598
599
	vma_adjust_trans_huge(vma, start, end, adjust_next);

600
601
602
603
	anon_vma = vma->anon_vma;
	if (!anon_vma && adjust_next)
		anon_vma = next->anon_vma;
	if (anon_vma) {
604
605
		VM_BUG_ON(adjust_next && next->anon_vma &&
			  anon_vma != next->anon_vma);
606
		anon_vma_lock(anon_vma);
607
608
609
610
		anon_vma_interval_tree_pre_update_vma(vma);
		if (adjust_next)
			anon_vma_interval_tree_pre_update_vma(next);
	}
611

Linus Torvalds's avatar
Linus Torvalds committed
612
613
	if (root) {
		flush_dcache_mmap_lock(mapping);
614
		vma_interval_tree_remove(vma, root);
Linus Torvalds's avatar
Linus Torvalds committed
615
		if (adjust_next)
616
			vma_interval_tree_remove(next, root);
Linus Torvalds's avatar
Linus Torvalds committed
617
618
619
620
621
622
623
624
625
626
627
628
	}

	vma->vm_start = start;
	vma->vm_end = end;
	vma->vm_pgoff = pgoff;
	if (adjust_next) {
		next->vm_start += adjust_next << PAGE_SHIFT;
		next->vm_pgoff += adjust_next;
	}

	if (root) {
		if (adjust_next)
629
630
			vma_interval_tree_insert(next, root);
		vma_interval_tree_insert(vma, root);
Linus Torvalds's avatar
Linus Torvalds committed
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
		flush_dcache_mmap_unlock(mapping);
	}

	if (remove_next) {
		/*
		 * vma_merge has merged next into vma, and needs
		 * us to remove next before dropping the locks.
		 */
		__vma_unlink(mm, next, vma);
		if (file)
			__remove_shared_vm_struct(next, file, mapping);
	} else if (insert) {
		/*
		 * split_vma has split insert from vma, and needs
		 * us to insert it before dropping the locks
		 * (it may either follow vma or precede it).
		 */
		__insert_vm_struct(mm, insert);
	}

651
652
653
654
	if (anon_vma) {
		anon_vma_interval_tree_post_update_vma(vma);
		if (adjust_next)
			anon_vma_interval_tree_post_update_vma(next);
655
		anon_vma_unlock(anon_vma);
656
	}
Linus Torvalds's avatar
Linus Torvalds committed
657
	if (mapping)
658
		mutex_unlock(&mapping->i_mmap_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
659

660
	if (root) {
661
		uprobe_mmap(vma);
662
663

		if (adjust_next)
664
			uprobe_mmap(next);
665
666
	}

Linus Torvalds's avatar
Linus Torvalds committed
667
	if (remove_next) {
Matt Helsley's avatar
Matt Helsley committed
668
		if (file) {
669
			uprobe_munmap(next, next->vm_start, next->vm_end);
Linus Torvalds's avatar
Linus Torvalds committed
670
			fput(file);
Matt Helsley's avatar
Matt Helsley committed
671
		}
672
673
		if (next->anon_vma)
			anon_vma_merge(vma, next);
Linus Torvalds's avatar
Linus Torvalds committed
674
		mm->map_count--;
675
		mpol_put(vma_policy(next));
Linus Torvalds's avatar
Linus Torvalds committed
676
677
678
679
680
681
682
683
684
685
686
		kmem_cache_free(vm_area_cachep, next);
		/*
		 * In mprotect's case 6 (see comments on vma_merge),
		 * we must remove another next too. It would clutter
		 * up the code too much to do both in one go.
		 */
		if (remove_next == 2) {
			next = vma->vm_next;
			goto again;
		}
	}
687
	if (insert && file)
688
		uprobe_mmap(insert);
Linus Torvalds's avatar
Linus Torvalds committed
689
690

	validate_mm(mm);
691
692

	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
693
694
695
696
697
698
699
700
701
}

/*
 * If the vma has a ->close operation then the driver probably needs to release
 * per-vma resources, so we don't attempt to merge those.
 */
static inline int is_mergeable_vma(struct vm_area_struct *vma,
			struct file *file, unsigned long vm_flags)
{
702
	if (vma->vm_flags ^ vm_flags)
Linus Torvalds's avatar
Linus Torvalds committed
703
704
705
706
707
708
709
710
711
		return 0;
	if (vma->vm_file != file)
		return 0;
	if (vma->vm_ops && vma->vm_ops->close)
		return 0;
	return 1;
}

static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
Shaohua Li's avatar
Shaohua Li committed
712
713
					struct anon_vma *anon_vma2,
					struct vm_area_struct *vma)
Linus Torvalds's avatar
Linus Torvalds committed
714
{
Shaohua Li's avatar
Shaohua Li committed
715
716
717
718
719
720
721
722
	/*
	 * The list_is_singular() test is to avoid merging VMA cloned from
	 * parents. This can improve scalability caused by anon_vma lock.
	 */
	if ((!anon_vma1 || !anon_vma2) && (!vma ||
		list_is_singular(&vma->anon_vma_chain)))
		return 1;
	return anon_vma1 == anon_vma2;
Linus Torvalds's avatar
Linus Torvalds committed
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
}

/*
 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
 * in front of (at a lower virtual address and file offset than) the vma.
 *
 * We cannot merge two vmas if they have differently assigned (non-NULL)
 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
 *
 * We don't check here for the merged mmap wrapping around the end of pagecache
 * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
 * wrap, nor mmaps which cover the final page at index -1UL.
 */
static int
can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
{
	if (is_mergeable_vma(vma, file, vm_flags) &&
Shaohua Li's avatar
Shaohua Li committed
741
	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
Linus Torvalds's avatar
Linus Torvalds committed
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
		if (vma->vm_pgoff == vm_pgoff)
			return 1;
	}
	return 0;
}

/*
 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
 * beyond (at a higher virtual address and file offset than) the vma.
 *
 * We cannot merge two vmas if they have differently assigned (non-NULL)
 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
 */
static int
can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
{
	if (is_mergeable_vma(vma, file, vm_flags) &&
Shaohua Li's avatar
Shaohua Li committed
760
	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
Linus Torvalds's avatar
Linus Torvalds committed
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
		pgoff_t vm_pglen;
		vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
			return 1;
	}
	return 0;
}

/*
 * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
 * whether that can be merged with its predecessor or its successor.
 * Or both (it neatly fills a hole).
 *
 * In most cases - when called for mmap, brk or mremap - [addr,end) is
 * certain not to be mapped by the time vma_merge is called; but when
 * called for mprotect, it is certain to be already mapped (either at
 * an offset within prev, or at the start of next), and the flags of
 * this area are about to be changed to vm_flags - and the no-change
 * case has already been eliminated.
 *
 * The following mprotect cases have to be considered, where AAAA is
 * the area passed down from mprotect_fixup, never extending beyond one
 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
 *
 *     AAAA             AAAA                AAAA          AAAA
 *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
 *    cannot merge    might become    might become    might become
 *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
 *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
 *    mremap move:                                    PPPPNNNNNNNN 8
 *        AAAA
 *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
 *    might become    case 1 below    case 2 below    case 3 below
 *
 * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
 * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
 */
struct vm_area_struct *vma_merge(struct mm_struct *mm,
			struct vm_area_struct *prev, unsigned long addr,
			unsigned long end, unsigned long vm_flags,
		     	struct anon_vma *anon_vma, struct file *file,
			pgoff_t pgoff, struct mempolicy *policy)
{
	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
	struct vm_area_struct *area, *next;
806
	int err;
Linus Torvalds's avatar
Linus Torvalds committed
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837

	/*
	 * We later require that vma->vm_flags == vm_flags,
	 * so this tests vma->vm_flags & VM_SPECIAL, too.
	 */
	if (vm_flags & VM_SPECIAL)
		return NULL;

	if (prev)
		next = prev->vm_next;
	else
		next = mm->mmap;
	area = next;
	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
		next = next->vm_next;

	/*
	 * Can it merge with the predecessor?
	 */
	if (prev && prev->vm_end == addr &&
  			mpol_equal(vma_policy(prev), policy) &&
			can_vma_merge_after(prev, vm_flags,
						anon_vma, file, pgoff)) {
		/*
		 * OK, it can.  Can we now merge in the successor as well?
		 */
		if (next && end == next->vm_start &&
				mpol_equal(policy, vma_policy(next)) &&
				can_vma_merge_before(next, vm_flags,
					anon_vma, file, pgoff+pglen) &&
				is_mergeable_anon_vma(prev->anon_vma,
Shaohua Li's avatar
Shaohua Li committed
838
						      next->anon_vma, NULL)) {
Linus Torvalds's avatar
Linus Torvalds committed
839
							/* cases 1, 6 */
840
			err = vma_adjust(prev, prev->vm_start,
Linus Torvalds's avatar
Linus Torvalds committed
841
842
				next->vm_end, prev->vm_pgoff, NULL);
		} else					/* cases 2, 5, 7 */
843
			err = vma_adjust(prev, prev->vm_start,
Linus Torvalds's avatar
Linus Torvalds committed
844
				end, prev->vm_pgoff, NULL);
845
846
		if (err)
			return NULL;
Andrea Arcangeli's avatar
Andrea Arcangeli committed
847
		khugepaged_enter_vma_merge(prev);
Linus Torvalds's avatar
Linus Torvalds committed
848
849
850
851
852
853
854
855
856
857
858
		return prev;
	}

	/*
	 * Can this new request be merged in front of next?
	 */
	if (next && end == next->vm_start &&
 			mpol_equal(policy, vma_policy(next)) &&
			can_vma_merge_before(next, vm_flags,
					anon_vma, file, pgoff+pglen)) {
		if (prev && addr < prev->vm_end)	/* case 4 */
859
			err = vma_adjust(prev, prev->vm_start,
Linus Torvalds's avatar
Linus Torvalds committed
860
861
				addr, prev->vm_pgoff, NULL);
		else					/* cases 3, 8 */
862
			err = vma_adjust(area, addr, next->vm_end,
Linus Torvalds's avatar
Linus Torvalds committed
863
				next->vm_pgoff - pglen, NULL);
864
865
		if (err)
			return NULL;
Andrea Arcangeli's avatar
Andrea Arcangeli committed
866
		khugepaged_enter_vma_merge(area);
Linus Torvalds's avatar
Linus Torvalds committed
867
868
869
870
871
872
		return area;
	}

	return NULL;
}

873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
/*
 * Rough compatbility check to quickly see if it's even worth looking
 * at sharing an anon_vma.
 *
 * They need to have the same vm_file, and the flags can only differ
 * in things that mprotect may change.
 *
 * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
 * we can merge the two vma's. For example, we refuse to merge a vma if
 * there is a vm_ops->close() function, because that indicates that the
 * driver is doing some kind of reference counting. But that doesn't
 * really matter for the anon_vma sharing case.
 */
static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
{
	return a->vm_end == b->vm_start &&
		mpol_equal(vma_policy(a), vma_policy(b)) &&
		a->vm_file == b->vm_file &&
		!((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) &&
		b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
}

/*
 * Do some basic sanity checking to see if we can re-use the anon_vma
 * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
 * the same as 'old', the other will be the new one that is trying
 * to share the anon_vma.
 *
 * NOTE! This runs with mm_sem held for reading, so it is possible that
 * the anon_vma of 'old' is concurrently in the process of being set up
 * by another page fault trying to merge _that_. But that's ok: if it
 * is being set up, that automatically means that it will be a singleton
 * acceptable for merging, so we can do all of this optimistically. But
 * we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
 *
 * IOW: that the "list_is_singular()" test on the anon_vma_chain only
 * matters for the 'stable anon_vma' case (ie the thing we want to avoid
 * is to return an anon_vma that is "complex" due to having gone through
 * a fork).
 *
 * We also make sure that the two vma's are compatible (adjacent,
 * and with the same memory policies). That's all stable, even with just
 * a read lock on the mm_sem.
 */
static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
{
	if (anon_vma_compatible(a, b)) {
		struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);

		if (anon_vma && list_is_singular(&old->anon_vma_chain))
			return anon_vma;
	}
	return NULL;
}

Linus Torvalds's avatar
Linus Torvalds committed
928
929
930
931
932
933
934
935
936
937
/*
 * find_mergeable_anon_vma is used by anon_vma_prepare, to check
 * neighbouring vmas for a suitable anon_vma, before it goes off
 * to allocate a new anon_vma.  It checks because a repetitive
 * sequence of mprotects and faults may otherwise lead to distinct
 * anon_vmas being allocated, preventing vma merge in subsequent
 * mprotect.
 */
struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
{
938
	struct anon_vma *anon_vma;
Linus Torvalds's avatar
Linus Torvalds committed
939
940
941
942
943
944
	struct vm_area_struct *near;

	near = vma->vm_next;
	if (!near)
		goto try_prev;

945
946
947
	anon_vma = reusable_anon_vma(near, vma, near);
	if (anon_vma)
		return anon_vma;
Linus Torvalds's avatar
Linus Torvalds committed
948
try_prev:
949
	near = vma->vm_prev;
Linus Torvalds's avatar
Linus Torvalds committed
950
951
952
	if (!near)
		goto none;

953
954
955
	anon_vma = reusable_anon_vma(near, near, vma);
	if (anon_vma)
		return anon_vma;
Linus Torvalds's avatar
Linus Torvalds committed
956
957
958
959
960
961
962
963
964
965
966
967
968
none:
	/*
	 * There's no absolute need to look only at touching neighbours:
	 * we could search further afield for "compatible" anon_vmas.
	 * But it would probably just be a waste of time searching,
	 * or lead to too many vmas hanging off the same anon_vma.
	 * We're trying to allow mprotect remerging later on,
	 * not trying to minimize memory used for anon_vmas.
	 */
	return NULL;
}

#ifdef CONFIG_PROC_FS
969
void vm_stat_account(struct mm_struct *mm, unsigned long flags,
Linus Torvalds's avatar
Linus Torvalds committed
970
971
972
973
974
						struct file *file, long pages)
{
	const unsigned long stack_flags
		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);

975
976
	mm->total_vm += pages;

Linus Torvalds's avatar
Linus Torvalds committed
977
978
979
980
981
982
983
984
985
	if (file) {
		mm->shared_vm += pages;
		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
			mm->exec_vm += pages;
	} else if (flags & stack_flags)
		mm->stack_vm += pages;
}
#endif /* CONFIG_PROC_FS */

Al Viro's avatar
Al Viro committed
986
987
988
989
990
991
992
993
994
995
996
997
998
/*
 * If a hint addr is less than mmap_min_addr change hint to be as
 * low as possible but still greater than mmap_min_addr
 */
static inline unsigned long round_hint_to_min(unsigned long hint)
{
	hint &= PAGE_MASK;
	if (((void *)hint != NULL) &&
	    (hint < mmap_min_addr))
		return PAGE_ALIGN(mmap_min_addr);
	return hint;
}

Linus Torvalds's avatar
Linus Torvalds committed
999
/*
1000
 * The caller must hold down_write(&current->mm->mmap_sem).