xref: /openbmc/linux/mm/mmap.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
1 /*
2  * mm/mmap.c
3  *
4  * Written by obz.
5  *
6  * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/backing-dev.h>
11 #include <linux/mm.h>
12 #include <linux/shm.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swap.h>
16 #include <linux/syscalls.h>
17 #include <linux/capability.h>
18 #include <linux/init.h>
19 #include <linux/file.h>
20 #include <linux/fs.h>
21 #include <linux/personality.h>
22 #include <linux/security.h>
23 #include <linux/hugetlb.h>
24 #include <linux/profile.h>
25 #include <linux/module.h>
26 #include <linux/mount.h>
27 #include <linux/mempolicy.h>
28 #include <linux/rmap.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/perf_event.h>
31 
32 #include <asm/uaccess.h>
33 #include <asm/cacheflush.h>
34 #include <asm/tlb.h>
35 #include <asm/mmu_context.h>
36 
37 #include "internal.h"
38 
39 #ifndef arch_mmap_check
40 #define arch_mmap_check(addr, len, flags)	(0)
41 #endif
42 
43 #ifndef arch_rebalance_pgtables
44 #define arch_rebalance_pgtables(addr, len)		(addr)
45 #endif
46 
47 static void unmap_region(struct mm_struct *mm,
48 		struct vm_area_struct *vma, struct vm_area_struct *prev,
49 		unsigned long start, unsigned long end);
50 
51 /*
52  * WARNING: the debugging will use recursive algorithms so never enable this
53  * unless you know what you are doing.
54  */
55 #undef DEBUG_MM_RB
56 
57 /* description of effects of mapping type and prot in current implementation.
58  * this is due to the limited x86 page protection hardware.  The expected
59  * behavior is in parens:
60  *
61  * map_type	prot
62  *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
63  * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
64  *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
65  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
66  *
67  * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
68  *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
69  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
70  *
71  */
72 pgprot_t protection_map[16] = {
73 	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
74 	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
75 };
76 
77 pgprot_t vm_get_page_prot(unsigned long vm_flags)
78 {
79 	return __pgprot(pgprot_val(protection_map[vm_flags &
80 				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
81 			pgprot_val(arch_vm_get_page_prot(vm_flags)));
82 }
83 EXPORT_SYMBOL(vm_get_page_prot);
84 
85 int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
86 int sysctl_overcommit_ratio = 50;	/* default is 50% */
87 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
88 struct percpu_counter vm_committed_as;
89 
90 /*
91  * Check that a process has enough memory to allocate a new virtual
92  * mapping. 0 means there is enough memory for the allocation to
93  * succeed and -ENOMEM implies there is not.
94  *
95  * We currently support three overcommit policies, which are set via the
96  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
97  *
98  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
99  * Additional code 2002 Jul 20 by Robert Love.
100  *
101  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
102  *
103  * Note this is a helper function intended to be used by LSMs which
104  * wish to use this logic.
105  */
106 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
107 {
108 	unsigned long free, allowed;
109 
110 	vm_acct_memory(pages);
111 
112 	/*
113 	 * Sometimes we want to use more memory than we have
114 	 */
115 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
116 		return 0;
117 
118 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
119 		unsigned long n;
120 
121 		free = global_page_state(NR_FILE_PAGES);
122 		free += nr_swap_pages;
123 
124 		/*
125 		 * Any slabs which are created with the
126 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
127 		 * which are reclaimable, under pressure.  The dentry
128 		 * cache and most inode caches should fall into this
129 		 */
130 		free += global_page_state(NR_SLAB_RECLAIMABLE);
131 
132 		/*
133 		 * Leave the last 3% for root
134 		 */
135 		if (!cap_sys_admin)
136 			free -= free / 32;
137 
138 		if (free > pages)
139 			return 0;
140 
141 		/*
142 		 * nr_free_pages() is very expensive on large systems,
143 		 * only call if we're about to fail.
144 		 */
145 		n = nr_free_pages();
146 
147 		/*
148 		 * Leave reserved pages. The pages are not for anonymous pages.
149 		 */
150 		if (n <= totalreserve_pages)
151 			goto error;
152 		else
153 			n -= totalreserve_pages;
154 
155 		/*
156 		 * Leave the last 3% for root
157 		 */
158 		if (!cap_sys_admin)
159 			n -= n / 32;
160 		free += n;
161 
162 		if (free > pages)
163 			return 0;
164 
165 		goto error;
166 	}
167 
168 	allowed = (totalram_pages - hugetlb_total_pages())
169 	       	* sysctl_overcommit_ratio / 100;
170 	/*
171 	 * Leave the last 3% for root
172 	 */
173 	if (!cap_sys_admin)
174 		allowed -= allowed / 32;
175 	allowed += total_swap_pages;
176 
177 	/* Don't let a single process grow too big:
178 	   leave 3% of the size of this process for other processes */
179 	if (mm)
180 		allowed -= mm->total_vm / 32;
181 
182 	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
183 		return 0;
184 error:
185 	vm_unacct_memory(pages);
186 
187 	return -ENOMEM;
188 }
189 
190 /*
191  * Requires inode->i_mapping->i_mmap_lock
192  */
193 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
194 		struct file *file, struct address_space *mapping)
195 {
196 	if (vma->vm_flags & VM_DENYWRITE)
197 		atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
198 	if (vma->vm_flags & VM_SHARED)
199 		mapping->i_mmap_writable--;
200 
201 	flush_dcache_mmap_lock(mapping);
202 	if (unlikely(vma->vm_flags & VM_NONLINEAR))
203 		list_del_init(&vma->shared.vm_set.list);
204 	else
205 		vma_prio_tree_remove(vma, &mapping->i_mmap);
206 	flush_dcache_mmap_unlock(mapping);
207 }
208 
209 /*
210  * Unlink a file-based vm structure from its prio_tree, to hide
211  * vma from rmap and vmtruncate before freeing its page tables.
212  */
213 void unlink_file_vma(struct vm_area_struct *vma)
214 {
215 	struct file *file = vma->vm_file;
216 
217 	if (file) {
218 		struct address_space *mapping = file->f_mapping;
219 		spin_lock(&mapping->i_mmap_lock);
220 		__remove_shared_vm_struct(vma, file, mapping);
221 		spin_unlock(&mapping->i_mmap_lock);
222 	}
223 }
224 
225 /*
226  * Close a vm structure and free it, returning the next.
227  */
228 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
229 {
230 	struct vm_area_struct *next = vma->vm_next;
231 
232 	might_sleep();
233 	if (vma->vm_ops && vma->vm_ops->close)
234 		vma->vm_ops->close(vma);
235 	if (vma->vm_file) {
236 		fput(vma->vm_file);
237 		if (vma->vm_flags & VM_EXECUTABLE)
238 			removed_exe_file_vma(vma->vm_mm);
239 	}
240 	mpol_put(vma_policy(vma));
241 	kmem_cache_free(vm_area_cachep, vma);
242 	return next;
243 }
244 
245 SYSCALL_DEFINE1(brk, unsigned long, brk)
246 {
247 	unsigned long rlim, retval;
248 	unsigned long newbrk, oldbrk;
249 	struct mm_struct *mm = current->mm;
250 	unsigned long min_brk;
251 
252 	down_write(&mm->mmap_sem);
253 
254 #ifdef CONFIG_COMPAT_BRK
255 	min_brk = mm->end_code;
256 #else
257 	min_brk = mm->start_brk;
258 #endif
259 	if (brk < min_brk)
260 		goto out;
261 
262 	/*
263 	 * Check against rlimit here. If this check is done later after the test
264 	 * of oldbrk with newbrk then it can escape the test and let the data
265 	 * segment grow beyond its set limit the in case where the limit is
266 	 * not page aligned -Ram Gupta
267 	 */
268 	rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
269 	if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
270 			(mm->end_data - mm->start_data) > rlim)
271 		goto out;
272 
273 	newbrk = PAGE_ALIGN(brk);
274 	oldbrk = PAGE_ALIGN(mm->brk);
275 	if (oldbrk == newbrk)
276 		goto set_brk;
277 
278 	/* Always allow shrinking brk. */
279 	if (brk <= mm->brk) {
280 		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
281 			goto set_brk;
282 		goto out;
283 	}
284 
285 	/* Check against existing mmap mappings. */
286 	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
287 		goto out;
288 
289 	/* Ok, looks good - let it rip. */
290 	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
291 		goto out;
292 set_brk:
293 	mm->brk = brk;
294 out:
295 	retval = mm->brk;
296 	up_write(&mm->mmap_sem);
297 	return retval;
298 }
299 
300 #ifdef DEBUG_MM_RB
301 static int browse_rb(struct rb_root *root)
302 {
303 	int i = 0, j;
304 	struct rb_node *nd, *pn = NULL;
305 	unsigned long prev = 0, pend = 0;
306 
307 	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
308 		struct vm_area_struct *vma;
309 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
310 		if (vma->vm_start < prev)
311 			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
312 		if (vma->vm_start < pend)
313 			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
314 		if (vma->vm_start > vma->vm_end)
315 			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
316 		i++;
317 		pn = nd;
318 		prev = vma->vm_start;
319 		pend = vma->vm_end;
320 	}
321 	j = 0;
322 	for (nd = pn; nd; nd = rb_prev(nd)) {
323 		j++;
324 	}
325 	if (i != j)
326 		printk("backwards %d, forwards %d\n", j, i), i = 0;
327 	return i;
328 }
329 
330 void validate_mm(struct mm_struct *mm)
331 {
332 	int bug = 0;
333 	int i = 0;
334 	struct vm_area_struct *tmp = mm->mmap;
335 	while (tmp) {
336 		tmp = tmp->vm_next;
337 		i++;
338 	}
339 	if (i != mm->map_count)
340 		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
341 	i = browse_rb(&mm->mm_rb);
342 	if (i != mm->map_count)
343 		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
344 	BUG_ON(bug);
345 }
346 #else
347 #define validate_mm(mm) do { } while (0)
348 #endif
349 
350 static struct vm_area_struct *
351 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
352 		struct vm_area_struct **pprev, struct rb_node ***rb_link,
353 		struct rb_node ** rb_parent)
354 {
355 	struct vm_area_struct * vma;
356 	struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
357 
358 	__rb_link = &mm->mm_rb.rb_node;
359 	rb_prev = __rb_parent = NULL;
360 	vma = NULL;
361 
362 	while (*__rb_link) {
363 		struct vm_area_struct *vma_tmp;
364 
365 		__rb_parent = *__rb_link;
366 		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
367 
368 		if (vma_tmp->vm_end > addr) {
369 			vma = vma_tmp;
370 			if (vma_tmp->vm_start <= addr)
371 				break;
372 			__rb_link = &__rb_parent->rb_left;
373 		} else {
374 			rb_prev = __rb_parent;
375 			__rb_link = &__rb_parent->rb_right;
376 		}
377 	}
378 
379 	*pprev = NULL;
380 	if (rb_prev)
381 		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
382 	*rb_link = __rb_link;
383 	*rb_parent = __rb_parent;
384 	return vma;
385 }
386 
387 static inline void
388 __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
389 		struct vm_area_struct *prev, struct rb_node *rb_parent)
390 {
391 	if (prev) {
392 		vma->vm_next = prev->vm_next;
393 		prev->vm_next = vma;
394 	} else {
395 		mm->mmap = vma;
396 		if (rb_parent)
397 			vma->vm_next = rb_entry(rb_parent,
398 					struct vm_area_struct, vm_rb);
399 		else
400 			vma->vm_next = NULL;
401 	}
402 }
403 
404 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
405 		struct rb_node **rb_link, struct rb_node *rb_parent)
406 {
407 	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
408 	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
409 }
410 
411 static void __vma_link_file(struct vm_area_struct *vma)
412 {
413 	struct file *file;
414 
415 	file = vma->vm_file;
416 	if (file) {
417 		struct address_space *mapping = file->f_mapping;
418 
419 		if (vma->vm_flags & VM_DENYWRITE)
420 			atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
421 		if (vma->vm_flags & VM_SHARED)
422 			mapping->i_mmap_writable++;
423 
424 		flush_dcache_mmap_lock(mapping);
425 		if (unlikely(vma->vm_flags & VM_NONLINEAR))
426 			vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
427 		else
428 			vma_prio_tree_insert(vma, &mapping->i_mmap);
429 		flush_dcache_mmap_unlock(mapping);
430 	}
431 }
432 
433 static void
434 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
435 	struct vm_area_struct *prev, struct rb_node **rb_link,
436 	struct rb_node *rb_parent)
437 {
438 	__vma_link_list(mm, vma, prev, rb_parent);
439 	__vma_link_rb(mm, vma, rb_link, rb_parent);
440 	__anon_vma_link(vma);
441 }
442 
443 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
444 			struct vm_area_struct *prev, struct rb_node **rb_link,
445 			struct rb_node *rb_parent)
446 {
447 	struct address_space *mapping = NULL;
448 
449 	if (vma->vm_file)
450 		mapping = vma->vm_file->f_mapping;
451 
452 	if (mapping) {
453 		spin_lock(&mapping->i_mmap_lock);
454 		vma->vm_truncate_count = mapping->truncate_count;
455 	}
456 	anon_vma_lock(vma);
457 
458 	__vma_link(mm, vma, prev, rb_link, rb_parent);
459 	__vma_link_file(vma);
460 
461 	anon_vma_unlock(vma);
462 	if (mapping)
463 		spin_unlock(&mapping->i_mmap_lock);
464 
465 	mm->map_count++;
466 	validate_mm(mm);
467 }
468 
469 /*
470  * Helper for vma_adjust in the split_vma insert case:
471  * insert vm structure into list and rbtree and anon_vma,
472  * but it has already been inserted into prio_tree earlier.
473  */
474 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
475 {
476 	struct vm_area_struct *__vma, *prev;
477 	struct rb_node **rb_link, *rb_parent;
478 
479 	__vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
480 	BUG_ON(__vma && __vma->vm_start < vma->vm_end);
481 	__vma_link(mm, vma, prev, rb_link, rb_parent);
482 	mm->map_count++;
483 }
484 
485 static inline void
486 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
487 		struct vm_area_struct *prev)
488 {
489 	prev->vm_next = vma->vm_next;
490 	rb_erase(&vma->vm_rb, &mm->mm_rb);
491 	if (mm->mmap_cache == vma)
492 		mm->mmap_cache = prev;
493 }
494 
495 /*
496  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
497  * is already present in an i_mmap tree without adjusting the tree.
498  * The following helper function should be used when such adjustments
499  * are necessary.  The "insert" vma (if any) is to be inserted
500  * before we drop the necessary locks.
501  */
502 void vma_adjust(struct vm_area_struct *vma, unsigned long start,
503 	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
504 {
505 	struct mm_struct *mm = vma->vm_mm;
506 	struct vm_area_struct *next = vma->vm_next;
507 	struct vm_area_struct *importer = NULL;
508 	struct address_space *mapping = NULL;
509 	struct prio_tree_root *root = NULL;
510 	struct file *file = vma->vm_file;
511 	struct anon_vma *anon_vma = NULL;
512 	long adjust_next = 0;
513 	int remove_next = 0;
514 
515 	if (next && !insert) {
516 		if (end >= next->vm_end) {
517 			/*
518 			 * vma expands, overlapping all the next, and
519 			 * perhaps the one after too (mprotect case 6).
520 			 */
521 again:			remove_next = 1 + (end > next->vm_end);
522 			end = next->vm_end;
523 			anon_vma = next->anon_vma;
524 			importer = vma;
525 		} else if (end > next->vm_start) {
526 			/*
527 			 * vma expands, overlapping part of the next:
528 			 * mprotect case 5 shifting the boundary up.
529 			 */
530 			adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
531 			anon_vma = next->anon_vma;
532 			importer = vma;
533 		} else if (end < vma->vm_end) {
534 			/*
535 			 * vma shrinks, and !insert tells it's not
536 			 * split_vma inserting another: so it must be
537 			 * mprotect case 4 shifting the boundary down.
538 			 */
539 			adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
540 			anon_vma = next->anon_vma;
541 			importer = next;
542 		}
543 	}
544 
545 	if (file) {
546 		mapping = file->f_mapping;
547 		if (!(vma->vm_flags & VM_NONLINEAR))
548 			root = &mapping->i_mmap;
549 		spin_lock(&mapping->i_mmap_lock);
550 		if (importer &&
551 		    vma->vm_truncate_count != next->vm_truncate_count) {
552 			/*
553 			 * unmap_mapping_range might be in progress:
554 			 * ensure that the expanding vma is rescanned.
555 			 */
556 			importer->vm_truncate_count = 0;
557 		}
558 		if (insert) {
559 			insert->vm_truncate_count = vma->vm_truncate_count;
560 			/*
561 			 * Put into prio_tree now, so instantiated pages
562 			 * are visible to arm/parisc __flush_dcache_page
563 			 * throughout; but we cannot insert into address
564 			 * space until vma start or end is updated.
565 			 */
566 			__vma_link_file(insert);
567 		}
568 	}
569 
570 	/*
571 	 * When changing only vma->vm_end, we don't really need
572 	 * anon_vma lock.
573 	 */
574 	if (vma->anon_vma && (insert || importer || start != vma->vm_start))
575 		anon_vma = vma->anon_vma;
576 	if (anon_vma) {
577 		spin_lock(&anon_vma->lock);
578 		/*
579 		 * Easily overlooked: when mprotect shifts the boundary,
580 		 * make sure the expanding vma has anon_vma set if the
581 		 * shrinking vma had, to cover any anon pages imported.
582 		 */
583 		if (importer && !importer->anon_vma) {
584 			importer->anon_vma = anon_vma;
585 			__anon_vma_link(importer);
586 		}
587 	}
588 
589 	if (root) {
590 		flush_dcache_mmap_lock(mapping);
591 		vma_prio_tree_remove(vma, root);
592 		if (adjust_next)
593 			vma_prio_tree_remove(next, root);
594 	}
595 
596 	vma->vm_start = start;
597 	vma->vm_end = end;
598 	vma->vm_pgoff = pgoff;
599 	if (adjust_next) {
600 		next->vm_start += adjust_next << PAGE_SHIFT;
601 		next->vm_pgoff += adjust_next;
602 	}
603 
604 	if (root) {
605 		if (adjust_next)
606 			vma_prio_tree_insert(next, root);
607 		vma_prio_tree_insert(vma, root);
608 		flush_dcache_mmap_unlock(mapping);
609 	}
610 
611 	if (remove_next) {
612 		/*
613 		 * vma_merge has merged next into vma, and needs
614 		 * us to remove next before dropping the locks.
615 		 */
616 		__vma_unlink(mm, next, vma);
617 		if (file)
618 			__remove_shared_vm_struct(next, file, mapping);
619 		if (next->anon_vma)
620 			__anon_vma_merge(vma, next);
621 	} else if (insert) {
622 		/*
623 		 * split_vma has split insert from vma, and needs
624 		 * us to insert it before dropping the locks
625 		 * (it may either follow vma or precede it).
626 		 */
627 		__insert_vm_struct(mm, insert);
628 	}
629 
630 	if (anon_vma)
631 		spin_unlock(&anon_vma->lock);
632 	if (mapping)
633 		spin_unlock(&mapping->i_mmap_lock);
634 
635 	if (remove_next) {
636 		if (file) {
637 			fput(file);
638 			if (next->vm_flags & VM_EXECUTABLE)
639 				removed_exe_file_vma(mm);
640 		}
641 		mm->map_count--;
642 		mpol_put(vma_policy(next));
643 		kmem_cache_free(vm_area_cachep, next);
644 		/*
645 		 * In mprotect's case 6 (see comments on vma_merge),
646 		 * we must remove another next too. It would clutter
647 		 * up the code too much to do both in one go.
648 		 */
649 		if (remove_next == 2) {
650 			next = vma->vm_next;
651 			goto again;
652 		}
653 	}
654 
655 	validate_mm(mm);
656 }
657 
658 /*
659  * If the vma has a ->close operation then the driver probably needs to release
660  * per-vma resources, so we don't attempt to merge those.
661  */
662 static inline int is_mergeable_vma(struct vm_area_struct *vma,
663 			struct file *file, unsigned long vm_flags)
664 {
665 	/* VM_CAN_NONLINEAR may get set later by f_op->mmap() */
666 	if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR)
667 		return 0;
668 	if (vma->vm_file != file)
669 		return 0;
670 	if (vma->vm_ops && vma->vm_ops->close)
671 		return 0;
672 	return 1;
673 }
674 
675 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
676 					struct anon_vma *anon_vma2)
677 {
678 	return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
679 }
680 
681 /*
682  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
683  * in front of (at a lower virtual address and file offset than) the vma.
684  *
685  * We cannot merge two vmas if they have differently assigned (non-NULL)
686  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
687  *
688  * We don't check here for the merged mmap wrapping around the end of pagecache
689  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
690  * wrap, nor mmaps which cover the final page at index -1UL.
691  */
692 static int
693 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
694 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
695 {
696 	if (is_mergeable_vma(vma, file, vm_flags) &&
697 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
698 		if (vma->vm_pgoff == vm_pgoff)
699 			return 1;
700 	}
701 	return 0;
702 }
703 
704 /*
705  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
706  * beyond (at a higher virtual address and file offset than) the vma.
707  *
708  * We cannot merge two vmas if they have differently assigned (non-NULL)
709  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
710  */
711 static int
712 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
713 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
714 {
715 	if (is_mergeable_vma(vma, file, vm_flags) &&
716 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
717 		pgoff_t vm_pglen;
718 		vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
719 		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
720 			return 1;
721 	}
722 	return 0;
723 }
724 
725 /*
726  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
727  * whether that can be merged with its predecessor or its successor.
728  * Or both (it neatly fills a hole).
729  *
730  * In most cases - when called for mmap, brk or mremap - [addr,end) is
731  * certain not to be mapped by the time vma_merge is called; but when
732  * called for mprotect, it is certain to be already mapped (either at
733  * an offset within prev, or at the start of next), and the flags of
734  * this area are about to be changed to vm_flags - and the no-change
735  * case has already been eliminated.
736  *
737  * The following mprotect cases have to be considered, where AAAA is
738  * the area passed down from mprotect_fixup, never extending beyond one
739  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
740  *
741  *     AAAA             AAAA                AAAA          AAAA
742  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
743  *    cannot merge    might become    might become    might become
744  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
745  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
746  *    mremap move:                                    PPPPNNNNNNNN 8
747  *        AAAA
748  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
749  *    might become    case 1 below    case 2 below    case 3 below
750  *
751  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
752  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
753  */
754 struct vm_area_struct *vma_merge(struct mm_struct *mm,
755 			struct vm_area_struct *prev, unsigned long addr,
756 			unsigned long end, unsigned long vm_flags,
757 		     	struct anon_vma *anon_vma, struct file *file,
758 			pgoff_t pgoff, struct mempolicy *policy)
759 {
760 	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
761 	struct vm_area_struct *area, *next;
762 
763 	/*
764 	 * We later require that vma->vm_flags == vm_flags,
765 	 * so this tests vma->vm_flags & VM_SPECIAL, too.
766 	 */
767 	if (vm_flags & VM_SPECIAL)
768 		return NULL;
769 
770 	if (prev)
771 		next = prev->vm_next;
772 	else
773 		next = mm->mmap;
774 	area = next;
775 	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
776 		next = next->vm_next;
777 
778 	/*
779 	 * Can it merge with the predecessor?
780 	 */
781 	if (prev && prev->vm_end == addr &&
782   			mpol_equal(vma_policy(prev), policy) &&
783 			can_vma_merge_after(prev, vm_flags,
784 						anon_vma, file, pgoff)) {
785 		/*
786 		 * OK, it can.  Can we now merge in the successor as well?
787 		 */
788 		if (next && end == next->vm_start &&
789 				mpol_equal(policy, vma_policy(next)) &&
790 				can_vma_merge_before(next, vm_flags,
791 					anon_vma, file, pgoff+pglen) &&
792 				is_mergeable_anon_vma(prev->anon_vma,
793 						      next->anon_vma)) {
794 							/* cases 1, 6 */
795 			vma_adjust(prev, prev->vm_start,
796 				next->vm_end, prev->vm_pgoff, NULL);
797 		} else					/* cases 2, 5, 7 */
798 			vma_adjust(prev, prev->vm_start,
799 				end, prev->vm_pgoff, NULL);
800 		return prev;
801 	}
802 
803 	/*
804 	 * Can this new request be merged in front of next?
805 	 */
806 	if (next && end == next->vm_start &&
807  			mpol_equal(policy, vma_policy(next)) &&
808 			can_vma_merge_before(next, vm_flags,
809 					anon_vma, file, pgoff+pglen)) {
810 		if (prev && addr < prev->vm_end)	/* case 4 */
811 			vma_adjust(prev, prev->vm_start,
812 				addr, prev->vm_pgoff, NULL);
813 		else					/* cases 3, 8 */
814 			vma_adjust(area, addr, next->vm_end,
815 				next->vm_pgoff - pglen, NULL);
816 		return area;
817 	}
818 
819 	return NULL;
820 }
821 
822 /*
823  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
824  * neighbouring vmas for a suitable anon_vma, before it goes off
825  * to allocate a new anon_vma.  It checks because a repetitive
826  * sequence of mprotects and faults may otherwise lead to distinct
827  * anon_vmas being allocated, preventing vma merge in subsequent
828  * mprotect.
829  */
830 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
831 {
832 	struct vm_area_struct *near;
833 	unsigned long vm_flags;
834 
835 	near = vma->vm_next;
836 	if (!near)
837 		goto try_prev;
838 
839 	/*
840 	 * Since only mprotect tries to remerge vmas, match flags
841 	 * which might be mprotected into each other later on.
842 	 * Neither mlock nor madvise tries to remerge at present,
843 	 * so leave their flags as obstructing a merge.
844 	 */
845 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
846 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
847 
848 	if (near->anon_vma && vma->vm_end == near->vm_start &&
849  			mpol_equal(vma_policy(vma), vma_policy(near)) &&
850 			can_vma_merge_before(near, vm_flags,
851 				NULL, vma->vm_file, vma->vm_pgoff +
852 				((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)))
853 		return near->anon_vma;
854 try_prev:
855 	/*
856 	 * It is potentially slow to have to call find_vma_prev here.
857 	 * But it's only on the first write fault on the vma, not
858 	 * every time, and we could devise a way to avoid it later
859 	 * (e.g. stash info in next's anon_vma_node when assigning
860 	 * an anon_vma, or when trying vma_merge).  Another time.
861 	 */
862 	BUG_ON(find_vma_prev(vma->vm_mm, vma->vm_start, &near) != vma);
863 	if (!near)
864 		goto none;
865 
866 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
867 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
868 
869 	if (near->anon_vma && near->vm_end == vma->vm_start &&
870   			mpol_equal(vma_policy(near), vma_policy(vma)) &&
871 			can_vma_merge_after(near, vm_flags,
872 				NULL, vma->vm_file, vma->vm_pgoff))
873 		return near->anon_vma;
874 none:
875 	/*
876 	 * There's no absolute need to look only at touching neighbours:
877 	 * we could search further afield for "compatible" anon_vmas.
878 	 * But it would probably just be a waste of time searching,
879 	 * or lead to too many vmas hanging off the same anon_vma.
880 	 * We're trying to allow mprotect remerging later on,
881 	 * not trying to minimize memory used for anon_vmas.
882 	 */
883 	return NULL;
884 }
885 
886 #ifdef CONFIG_PROC_FS
887 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
888 						struct file *file, long pages)
889 {
890 	const unsigned long stack_flags
891 		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
892 
893 	if (file) {
894 		mm->shared_vm += pages;
895 		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
896 			mm->exec_vm += pages;
897 	} else if (flags & stack_flags)
898 		mm->stack_vm += pages;
899 	if (flags & (VM_RESERVED|VM_IO))
900 		mm->reserved_vm += pages;
901 }
902 #endif /* CONFIG_PROC_FS */
903 
904 /*
905  * The caller must hold down_write(&current->mm->mmap_sem).
906  */
907 
908 unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
909 			unsigned long len, unsigned long prot,
910 			unsigned long flags, unsigned long pgoff)
911 {
912 	struct mm_struct * mm = current->mm;
913 	struct inode *inode;
914 	unsigned int vm_flags;
915 	int error;
916 	unsigned long reqprot = prot;
917 
918 	/*
919 	 * Does the application expect PROT_READ to imply PROT_EXEC?
920 	 *
921 	 * (the exception is when the underlying filesystem is noexec
922 	 *  mounted, in which case we dont add PROT_EXEC.)
923 	 */
924 	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
925 		if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
926 			prot |= PROT_EXEC;
927 
928 	if (!len)
929 		return -EINVAL;
930 
931 	if (!(flags & MAP_FIXED))
932 		addr = round_hint_to_min(addr);
933 
934 	/* Careful about overflows.. */
935 	len = PAGE_ALIGN(len);
936 	if (!len)
937 		return -ENOMEM;
938 
939 	/* offset overflow? */
940 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
941                return -EOVERFLOW;
942 
943 	/* Too many mappings? */
944 	if (mm->map_count > sysctl_max_map_count)
945 		return -ENOMEM;
946 
947 	/* Obtain the address to map to. we verify (or select) it and ensure
948 	 * that it represents a valid section of the address space.
949 	 */
950 	addr = get_unmapped_area(file, addr, len, pgoff, flags);
951 	if (addr & ~PAGE_MASK)
952 		return addr;
953 
954 	/* Do simple checking here so the lower-level routines won't have
955 	 * to. we assume access permissions have been handled by the open
956 	 * of the memory object, so we don't do any here.
957 	 */
958 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
959 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
960 
961 	if (flags & MAP_LOCKED)
962 		if (!can_do_mlock())
963 			return -EPERM;
964 
965 	/* mlock MCL_FUTURE? */
966 	if (vm_flags & VM_LOCKED) {
967 		unsigned long locked, lock_limit;
968 		locked = len >> PAGE_SHIFT;
969 		locked += mm->locked_vm;
970 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
971 		lock_limit >>= PAGE_SHIFT;
972 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
973 			return -EAGAIN;
974 	}
975 
976 	inode = file ? file->f_path.dentry->d_inode : NULL;
977 
978 	if (file) {
979 		switch (flags & MAP_TYPE) {
980 		case MAP_SHARED:
981 			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
982 				return -EACCES;
983 
984 			/*
985 			 * Make sure we don't allow writing to an append-only
986 			 * file..
987 			 */
988 			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
989 				return -EACCES;
990 
991 			/*
992 			 * Make sure there are no mandatory locks on the file.
993 			 */
994 			if (locks_verify_locked(inode))
995 				return -EAGAIN;
996 
997 			vm_flags |= VM_SHARED | VM_MAYSHARE;
998 			if (!(file->f_mode & FMODE_WRITE))
999 				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1000 
1001 			/* fall through */
1002 		case MAP_PRIVATE:
1003 			if (!(file->f_mode & FMODE_READ))
1004 				return -EACCES;
1005 			if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1006 				if (vm_flags & VM_EXEC)
1007 					return -EPERM;
1008 				vm_flags &= ~VM_MAYEXEC;
1009 			}
1010 
1011 			if (!file->f_op || !file->f_op->mmap)
1012 				return -ENODEV;
1013 			break;
1014 
1015 		default:
1016 			return -EINVAL;
1017 		}
1018 	} else {
1019 		switch (flags & MAP_TYPE) {
1020 		case MAP_SHARED:
1021 			/*
1022 			 * Ignore pgoff.
1023 			 */
1024 			pgoff = 0;
1025 			vm_flags |= VM_SHARED | VM_MAYSHARE;
1026 			break;
1027 		case MAP_PRIVATE:
1028 			/*
1029 			 * Set pgoff according to addr for anon_vma.
1030 			 */
1031 			pgoff = addr >> PAGE_SHIFT;
1032 			break;
1033 		default:
1034 			return -EINVAL;
1035 		}
1036 	}
1037 
1038 	error = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1039 	if (error)
1040 		return error;
1041 
1042 	return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1043 }
1044 EXPORT_SYMBOL(do_mmap_pgoff);
1045 
1046 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1047 		unsigned long, prot, unsigned long, flags,
1048 		unsigned long, fd, unsigned long, pgoff)
1049 {
1050 	struct file *file = NULL;
1051 	unsigned long retval = -EBADF;
1052 
1053 	if (!(flags & MAP_ANONYMOUS)) {
1054 		if (unlikely(flags & MAP_HUGETLB))
1055 			return -EINVAL;
1056 		file = fget(fd);
1057 		if (!file)
1058 			goto out;
1059 	} else if (flags & MAP_HUGETLB) {
1060 		struct user_struct *user = NULL;
1061 		/*
1062 		 * VM_NORESERVE is used because the reservations will be
1063 		 * taken when vm_ops->mmap() is called
1064 		 * A dummy user value is used because we are not locking
1065 		 * memory so no accounting is necessary
1066 		 */
1067 		len = ALIGN(len, huge_page_size(&default_hstate));
1068 		file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
1069 						&user, HUGETLB_ANONHUGE_INODE);
1070 		if (IS_ERR(file))
1071 			return PTR_ERR(file);
1072 	}
1073 
1074 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1075 
1076 	down_write(&current->mm->mmap_sem);
1077 	retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1078 	up_write(&current->mm->mmap_sem);
1079 
1080 	if (file)
1081 		fput(file);
1082 out:
1083 	return retval;
1084 }
1085 
1086 /*
1087  * Some shared mappigns will want the pages marked read-only
1088  * to track write events. If so, we'll downgrade vm_page_prot
1089  * to the private version (using protection_map[] without the
1090  * VM_SHARED bit).
1091  */
1092 int vma_wants_writenotify(struct vm_area_struct *vma)
1093 {
1094 	unsigned int vm_flags = vma->vm_flags;
1095 
1096 	/* If it was private or non-writable, the write bit is already clear */
1097 	if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1098 		return 0;
1099 
1100 	/* The backer wishes to know when pages are first written to? */
1101 	if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1102 		return 1;
1103 
1104 	/* The open routine did something to the protections already? */
1105 	if (pgprot_val(vma->vm_page_prot) !=
1106 	    pgprot_val(vm_get_page_prot(vm_flags)))
1107 		return 0;
1108 
1109 	/* Specialty mapping? */
1110 	if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1111 		return 0;
1112 
1113 	/* Can the mapping track the dirty pages? */
1114 	return vma->vm_file && vma->vm_file->f_mapping &&
1115 		mapping_cap_account_dirty(vma->vm_file->f_mapping);
1116 }
1117 
1118 /*
1119  * We account for memory if it's a private writeable mapping,
1120  * not hugepages and VM_NORESERVE wasn't set.
1121  */
1122 static inline int accountable_mapping(struct file *file, unsigned int vm_flags)
1123 {
1124 	/*
1125 	 * hugetlb has its own accounting separate from the core VM
1126 	 * VM_HUGETLB may not be set yet so we cannot check for that flag.
1127 	 */
1128 	if (file && is_file_hugepages(file))
1129 		return 0;
1130 
1131 	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1132 }
1133 
1134 unsigned long mmap_region(struct file *file, unsigned long addr,
1135 			  unsigned long len, unsigned long flags,
1136 			  unsigned int vm_flags, unsigned long pgoff)
1137 {
1138 	struct mm_struct *mm = current->mm;
1139 	struct vm_area_struct *vma, *prev;
1140 	int correct_wcount = 0;
1141 	int error;
1142 	struct rb_node **rb_link, *rb_parent;
1143 	unsigned long charged = 0;
1144 	struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
1145 
1146 	/* Clear old maps */
1147 	error = -ENOMEM;
1148 munmap_back:
1149 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1150 	if (vma && vma->vm_start < addr + len) {
1151 		if (do_munmap(mm, addr, len))
1152 			return -ENOMEM;
1153 		goto munmap_back;
1154 	}
1155 
1156 	/* Check against address space limit. */
1157 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1158 		return -ENOMEM;
1159 
1160 	/*
1161 	 * Set 'VM_NORESERVE' if we should not account for the
1162 	 * memory use of this mapping.
1163 	 */
1164 	if ((flags & MAP_NORESERVE)) {
1165 		/* We honor MAP_NORESERVE if allowed to overcommit */
1166 		if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1167 			vm_flags |= VM_NORESERVE;
1168 
1169 		/* hugetlb applies strict overcommit unless MAP_NORESERVE */
1170 		if (file && is_file_hugepages(file))
1171 			vm_flags |= VM_NORESERVE;
1172 	}
1173 
1174 	/*
1175 	 * Private writable mapping: check memory availability
1176 	 */
1177 	if (accountable_mapping(file, vm_flags)) {
1178 		charged = len >> PAGE_SHIFT;
1179 		if (security_vm_enough_memory(charged))
1180 			return -ENOMEM;
1181 		vm_flags |= VM_ACCOUNT;
1182 	}
1183 
1184 	/*
1185 	 * Can we just expand an old mapping?
1186 	 */
1187 	vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1188 	if (vma)
1189 		goto out;
1190 
1191 	/*
1192 	 * Determine the object being mapped and call the appropriate
1193 	 * specific mapper. the address has already been validated, but
1194 	 * not unmapped, but the maps are removed from the list.
1195 	 */
1196 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1197 	if (!vma) {
1198 		error = -ENOMEM;
1199 		goto unacct_error;
1200 	}
1201 
1202 	vma->vm_mm = mm;
1203 	vma->vm_start = addr;
1204 	vma->vm_end = addr + len;
1205 	vma->vm_flags = vm_flags;
1206 	vma->vm_page_prot = vm_get_page_prot(vm_flags);
1207 	vma->vm_pgoff = pgoff;
1208 
1209 	if (file) {
1210 		error = -EINVAL;
1211 		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1212 			goto free_vma;
1213 		if (vm_flags & VM_DENYWRITE) {
1214 			error = deny_write_access(file);
1215 			if (error)
1216 				goto free_vma;
1217 			correct_wcount = 1;
1218 		}
1219 		vma->vm_file = file;
1220 		get_file(file);
1221 		error = file->f_op->mmap(file, vma);
1222 		if (error)
1223 			goto unmap_and_free_vma;
1224 		if (vm_flags & VM_EXECUTABLE)
1225 			added_exe_file_vma(mm);
1226 
1227 		/* Can addr have changed??
1228 		 *
1229 		 * Answer: Yes, several device drivers can do it in their
1230 		 *         f_op->mmap method. -DaveM
1231 		 */
1232 		addr = vma->vm_start;
1233 		pgoff = vma->vm_pgoff;
1234 		vm_flags = vma->vm_flags;
1235 	} else if (vm_flags & VM_SHARED) {
1236 		error = shmem_zero_setup(vma);
1237 		if (error)
1238 			goto free_vma;
1239 	}
1240 
1241 	if (vma_wants_writenotify(vma)) {
1242 		pgprot_t pprot = vma->vm_page_prot;
1243 
1244 		/* Can vma->vm_page_prot have changed??
1245 		 *
1246 		 * Answer: Yes, drivers may have changed it in their
1247 		 *         f_op->mmap method.
1248 		 *
1249 		 * Ensures that vmas marked as uncached stay that way.
1250 		 */
1251 		vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1252 		if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
1253 			vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
1254 	}
1255 
1256 	vma_link(mm, vma, prev, rb_link, rb_parent);
1257 	file = vma->vm_file;
1258 
1259 	/* Once vma denies write, undo our temporary denial count */
1260 	if (correct_wcount)
1261 		atomic_inc(&inode->i_writecount);
1262 out:
1263 	perf_event_mmap(vma);
1264 
1265 	mm->total_vm += len >> PAGE_SHIFT;
1266 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1267 	if (vm_flags & VM_LOCKED) {
1268 		/*
1269 		 * makes pages present; downgrades, drops, reacquires mmap_sem
1270 		 */
1271 		long nr_pages = mlock_vma_pages_range(vma, addr, addr + len);
1272 		if (nr_pages < 0)
1273 			return nr_pages;	/* vma gone! */
1274 		mm->locked_vm += (len >> PAGE_SHIFT) - nr_pages;
1275 	} else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1276 		make_pages_present(addr, addr + len);
1277 	return addr;
1278 
1279 unmap_and_free_vma:
1280 	if (correct_wcount)
1281 		atomic_inc(&inode->i_writecount);
1282 	vma->vm_file = NULL;
1283 	fput(file);
1284 
1285 	/* Undo any partial mapping done by a device driver. */
1286 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1287 	charged = 0;
1288 free_vma:
1289 	kmem_cache_free(vm_area_cachep, vma);
1290 unacct_error:
1291 	if (charged)
1292 		vm_unacct_memory(charged);
1293 	return error;
1294 }
1295 
1296 /* Get an address range which is currently unmapped.
1297  * For shmat() with addr=0.
1298  *
1299  * Ugly calling convention alert:
1300  * Return value with the low bits set means error value,
1301  * ie
1302  *	if (ret & ~PAGE_MASK)
1303  *		error = ret;
1304  *
1305  * This function "knows" that -ENOMEM has the bits set.
1306  */
1307 #ifndef HAVE_ARCH_UNMAPPED_AREA
1308 unsigned long
1309 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1310 		unsigned long len, unsigned long pgoff, unsigned long flags)
1311 {
1312 	struct mm_struct *mm = current->mm;
1313 	struct vm_area_struct *vma;
1314 	unsigned long start_addr;
1315 
1316 	if (len > TASK_SIZE)
1317 		return -ENOMEM;
1318 
1319 	if (flags & MAP_FIXED)
1320 		return addr;
1321 
1322 	if (addr) {
1323 		addr = PAGE_ALIGN(addr);
1324 		vma = find_vma(mm, addr);
1325 		if (TASK_SIZE - len >= addr &&
1326 		    (!vma || addr + len <= vma->vm_start))
1327 			return addr;
1328 	}
1329 	if (len > mm->cached_hole_size) {
1330 	        start_addr = addr = mm->free_area_cache;
1331 	} else {
1332 	        start_addr = addr = TASK_UNMAPPED_BASE;
1333 	        mm->cached_hole_size = 0;
1334 	}
1335 
1336 full_search:
1337 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1338 		/* At this point:  (!vma || addr < vma->vm_end). */
1339 		if (TASK_SIZE - len < addr) {
1340 			/*
1341 			 * Start a new search - just in case we missed
1342 			 * some holes.
1343 			 */
1344 			if (start_addr != TASK_UNMAPPED_BASE) {
1345 				addr = TASK_UNMAPPED_BASE;
1346 			        start_addr = addr;
1347 				mm->cached_hole_size = 0;
1348 				goto full_search;
1349 			}
1350 			return -ENOMEM;
1351 		}
1352 		if (!vma || addr + len <= vma->vm_start) {
1353 			/*
1354 			 * Remember the place where we stopped the search:
1355 			 */
1356 			mm->free_area_cache = addr + len;
1357 			return addr;
1358 		}
1359 		if (addr + mm->cached_hole_size < vma->vm_start)
1360 		        mm->cached_hole_size = vma->vm_start - addr;
1361 		addr = vma->vm_end;
1362 	}
1363 }
1364 #endif
1365 
1366 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1367 {
1368 	/*
1369 	 * Is this a new hole at the lowest possible address?
1370 	 */
1371 	if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1372 		mm->free_area_cache = addr;
1373 		mm->cached_hole_size = ~0UL;
1374 	}
1375 }
1376 
1377 /*
1378  * This mmap-allocator allocates new areas top-down from below the
1379  * stack's low limit (the base):
1380  */
1381 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1382 unsigned long
1383 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1384 			  const unsigned long len, const unsigned long pgoff,
1385 			  const unsigned long flags)
1386 {
1387 	struct vm_area_struct *vma;
1388 	struct mm_struct *mm = current->mm;
1389 	unsigned long addr = addr0;
1390 
1391 	/* requested length too big for entire address space */
1392 	if (len > TASK_SIZE)
1393 		return -ENOMEM;
1394 
1395 	if (flags & MAP_FIXED)
1396 		return addr;
1397 
1398 	/* requesting a specific address */
1399 	if (addr) {
1400 		addr = PAGE_ALIGN(addr);
1401 		vma = find_vma(mm, addr);
1402 		if (TASK_SIZE - len >= addr &&
1403 				(!vma || addr + len <= vma->vm_start))
1404 			return addr;
1405 	}
1406 
1407 	/* check if free_area_cache is useful for us */
1408 	if (len <= mm->cached_hole_size) {
1409  	        mm->cached_hole_size = 0;
1410  		mm->free_area_cache = mm->mmap_base;
1411  	}
1412 
1413 	/* either no address requested or can't fit in requested address hole */
1414 	addr = mm->free_area_cache;
1415 
1416 	/* make sure it can fit in the remaining address space */
1417 	if (addr > len) {
1418 		vma = find_vma(mm, addr-len);
1419 		if (!vma || addr <= vma->vm_start)
1420 			/* remember the address as a hint for next time */
1421 			return (mm->free_area_cache = addr-len);
1422 	}
1423 
1424 	if (mm->mmap_base < len)
1425 		goto bottomup;
1426 
1427 	addr = mm->mmap_base-len;
1428 
1429 	do {
1430 		/*
1431 		 * Lookup failure means no vma is above this address,
1432 		 * else if new region fits below vma->vm_start,
1433 		 * return with success:
1434 		 */
1435 		vma = find_vma(mm, addr);
1436 		if (!vma || addr+len <= vma->vm_start)
1437 			/* remember the address as a hint for next time */
1438 			return (mm->free_area_cache = addr);
1439 
1440  		/* remember the largest hole we saw so far */
1441  		if (addr + mm->cached_hole_size < vma->vm_start)
1442  		        mm->cached_hole_size = vma->vm_start - addr;
1443 
1444 		/* try just below the current vma->vm_start */
1445 		addr = vma->vm_start-len;
1446 	} while (len < vma->vm_start);
1447 
1448 bottomup:
1449 	/*
1450 	 * A failed mmap() very likely causes application failure,
1451 	 * so fall back to the bottom-up function here. This scenario
1452 	 * can happen with large stack limits and large mmap()
1453 	 * allocations.
1454 	 */
1455 	mm->cached_hole_size = ~0UL;
1456   	mm->free_area_cache = TASK_UNMAPPED_BASE;
1457 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1458 	/*
1459 	 * Restore the topdown base:
1460 	 */
1461 	mm->free_area_cache = mm->mmap_base;
1462 	mm->cached_hole_size = ~0UL;
1463 
1464 	return addr;
1465 }
1466 #endif
1467 
1468 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1469 {
1470 	/*
1471 	 * Is this a new hole at the highest possible address?
1472 	 */
1473 	if (addr > mm->free_area_cache)
1474 		mm->free_area_cache = addr;
1475 
1476 	/* dont allow allocations above current base */
1477 	if (mm->free_area_cache > mm->mmap_base)
1478 		mm->free_area_cache = mm->mmap_base;
1479 }
1480 
1481 unsigned long
1482 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1483 		unsigned long pgoff, unsigned long flags)
1484 {
1485 	unsigned long (*get_area)(struct file *, unsigned long,
1486 				  unsigned long, unsigned long, unsigned long);
1487 
1488 	unsigned long error = arch_mmap_check(addr, len, flags);
1489 	if (error)
1490 		return error;
1491 
1492 	/* Careful about overflows.. */
1493 	if (len > TASK_SIZE)
1494 		return -ENOMEM;
1495 
1496 	get_area = current->mm->get_unmapped_area;
1497 	if (file && file->f_op && file->f_op->get_unmapped_area)
1498 		get_area = file->f_op->get_unmapped_area;
1499 	addr = get_area(file, addr, len, pgoff, flags);
1500 	if (IS_ERR_VALUE(addr))
1501 		return addr;
1502 
1503 	if (addr > TASK_SIZE - len)
1504 		return -ENOMEM;
1505 	if (addr & ~PAGE_MASK)
1506 		return -EINVAL;
1507 
1508 	return arch_rebalance_pgtables(addr, len);
1509 }
1510 
1511 EXPORT_SYMBOL(get_unmapped_area);
1512 
1513 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1514 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1515 {
1516 	struct vm_area_struct *vma = NULL;
1517 
1518 	if (mm) {
1519 		/* Check the cache first. */
1520 		/* (Cache hit rate is typically around 35%.) */
1521 		vma = mm->mmap_cache;
1522 		if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1523 			struct rb_node * rb_node;
1524 
1525 			rb_node = mm->mm_rb.rb_node;
1526 			vma = NULL;
1527 
1528 			while (rb_node) {
1529 				struct vm_area_struct * vma_tmp;
1530 
1531 				vma_tmp = rb_entry(rb_node,
1532 						struct vm_area_struct, vm_rb);
1533 
1534 				if (vma_tmp->vm_end > addr) {
1535 					vma = vma_tmp;
1536 					if (vma_tmp->vm_start <= addr)
1537 						break;
1538 					rb_node = rb_node->rb_left;
1539 				} else
1540 					rb_node = rb_node->rb_right;
1541 			}
1542 			if (vma)
1543 				mm->mmap_cache = vma;
1544 		}
1545 	}
1546 	return vma;
1547 }
1548 
1549 EXPORT_SYMBOL(find_vma);
1550 
1551 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1552 struct vm_area_struct *
1553 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1554 			struct vm_area_struct **pprev)
1555 {
1556 	struct vm_area_struct *vma = NULL, *prev = NULL;
1557 	struct rb_node *rb_node;
1558 	if (!mm)
1559 		goto out;
1560 
1561 	/* Guard against addr being lower than the first VMA */
1562 	vma = mm->mmap;
1563 
1564 	/* Go through the RB tree quickly. */
1565 	rb_node = mm->mm_rb.rb_node;
1566 
1567 	while (rb_node) {
1568 		struct vm_area_struct *vma_tmp;
1569 		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1570 
1571 		if (addr < vma_tmp->vm_end) {
1572 			rb_node = rb_node->rb_left;
1573 		} else {
1574 			prev = vma_tmp;
1575 			if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1576 				break;
1577 			rb_node = rb_node->rb_right;
1578 		}
1579 	}
1580 
1581 out:
1582 	*pprev = prev;
1583 	return prev ? prev->vm_next : vma;
1584 }
1585 
1586 /*
1587  * Verify that the stack growth is acceptable and
1588  * update accounting. This is shared with both the
1589  * grow-up and grow-down cases.
1590  */
1591 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1592 {
1593 	struct mm_struct *mm = vma->vm_mm;
1594 	struct rlimit *rlim = current->signal->rlim;
1595 	unsigned long new_start;
1596 
1597 	/* address space limit tests */
1598 	if (!may_expand_vm(mm, grow))
1599 		return -ENOMEM;
1600 
1601 	/* Stack limit test */
1602 	if (size > rlim[RLIMIT_STACK].rlim_cur)
1603 		return -ENOMEM;
1604 
1605 	/* mlock limit tests */
1606 	if (vma->vm_flags & VM_LOCKED) {
1607 		unsigned long locked;
1608 		unsigned long limit;
1609 		locked = mm->locked_vm + grow;
1610 		limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
1611 		if (locked > limit && !capable(CAP_IPC_LOCK))
1612 			return -ENOMEM;
1613 	}
1614 
1615 	/* Check to ensure the stack will not grow into a hugetlb-only region */
1616 	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1617 			vma->vm_end - size;
1618 	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1619 		return -EFAULT;
1620 
1621 	/*
1622 	 * Overcommit..  This must be the final test, as it will
1623 	 * update security statistics.
1624 	 */
1625 	if (security_vm_enough_memory_mm(mm, grow))
1626 		return -ENOMEM;
1627 
1628 	/* Ok, everything looks good - let it rip */
1629 	mm->total_vm += grow;
1630 	if (vma->vm_flags & VM_LOCKED)
1631 		mm->locked_vm += grow;
1632 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1633 	return 0;
1634 }
1635 
1636 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1637 /*
1638  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1639  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1640  */
1641 #ifndef CONFIG_IA64
1642 static
1643 #endif
1644 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1645 {
1646 	int error;
1647 
1648 	if (!(vma->vm_flags & VM_GROWSUP))
1649 		return -EFAULT;
1650 
1651 	/*
1652 	 * We must make sure the anon_vma is allocated
1653 	 * so that the anon_vma locking is not a noop.
1654 	 */
1655 	if (unlikely(anon_vma_prepare(vma)))
1656 		return -ENOMEM;
1657 	anon_vma_lock(vma);
1658 
1659 	/*
1660 	 * vma->vm_start/vm_end cannot change under us because the caller
1661 	 * is required to hold the mmap_sem in read mode.  We need the
1662 	 * anon_vma lock to serialize against concurrent expand_stacks.
1663 	 * Also guard against wrapping around to address 0.
1664 	 */
1665 	if (address < PAGE_ALIGN(address+4))
1666 		address = PAGE_ALIGN(address+4);
1667 	else {
1668 		anon_vma_unlock(vma);
1669 		return -ENOMEM;
1670 	}
1671 	error = 0;
1672 
1673 	/* Somebody else might have raced and expanded it already */
1674 	if (address > vma->vm_end) {
1675 		unsigned long size, grow;
1676 
1677 		size = address - vma->vm_start;
1678 		grow = (address - vma->vm_end) >> PAGE_SHIFT;
1679 
1680 		error = acct_stack_growth(vma, size, grow);
1681 		if (!error)
1682 			vma->vm_end = address;
1683 	}
1684 	anon_vma_unlock(vma);
1685 	return error;
1686 }
1687 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1688 
1689 /*
1690  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1691  */
1692 static int expand_downwards(struct vm_area_struct *vma,
1693 				   unsigned long address)
1694 {
1695 	int error;
1696 
1697 	/*
1698 	 * We must make sure the anon_vma is allocated
1699 	 * so that the anon_vma locking is not a noop.
1700 	 */
1701 	if (unlikely(anon_vma_prepare(vma)))
1702 		return -ENOMEM;
1703 
1704 	address &= PAGE_MASK;
1705 	error = security_file_mmap(NULL, 0, 0, 0, address, 1);
1706 	if (error)
1707 		return error;
1708 
1709 	anon_vma_lock(vma);
1710 
1711 	/*
1712 	 * vma->vm_start/vm_end cannot change under us because the caller
1713 	 * is required to hold the mmap_sem in read mode.  We need the
1714 	 * anon_vma lock to serialize against concurrent expand_stacks.
1715 	 */
1716 
1717 	/* Somebody else might have raced and expanded it already */
1718 	if (address < vma->vm_start) {
1719 		unsigned long size, grow;
1720 
1721 		size = vma->vm_end - address;
1722 		grow = (vma->vm_start - address) >> PAGE_SHIFT;
1723 
1724 		error = acct_stack_growth(vma, size, grow);
1725 		if (!error) {
1726 			vma->vm_start = address;
1727 			vma->vm_pgoff -= grow;
1728 		}
1729 	}
1730 	anon_vma_unlock(vma);
1731 	return error;
1732 }
1733 
1734 int expand_stack_downwards(struct vm_area_struct *vma, unsigned long address)
1735 {
1736 	return expand_downwards(vma, address);
1737 }
1738 
1739 #ifdef CONFIG_STACK_GROWSUP
1740 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1741 {
1742 	return expand_upwards(vma, address);
1743 }
1744 
1745 struct vm_area_struct *
1746 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1747 {
1748 	struct vm_area_struct *vma, *prev;
1749 
1750 	addr &= PAGE_MASK;
1751 	vma = find_vma_prev(mm, addr, &prev);
1752 	if (vma && (vma->vm_start <= addr))
1753 		return vma;
1754 	if (!prev || expand_stack(prev, addr))
1755 		return NULL;
1756 	if (prev->vm_flags & VM_LOCKED) {
1757 		if (mlock_vma_pages_range(prev, addr, prev->vm_end) < 0)
1758 			return NULL;	/* vma gone! */
1759 	}
1760 	return prev;
1761 }
1762 #else
1763 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1764 {
1765 	return expand_downwards(vma, address);
1766 }
1767 
1768 struct vm_area_struct *
1769 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1770 {
1771 	struct vm_area_struct * vma;
1772 	unsigned long start;
1773 
1774 	addr &= PAGE_MASK;
1775 	vma = find_vma(mm,addr);
1776 	if (!vma)
1777 		return NULL;
1778 	if (vma->vm_start <= addr)
1779 		return vma;
1780 	if (!(vma->vm_flags & VM_GROWSDOWN))
1781 		return NULL;
1782 	start = vma->vm_start;
1783 	if (expand_stack(vma, addr))
1784 		return NULL;
1785 	if (vma->vm_flags & VM_LOCKED) {
1786 		if (mlock_vma_pages_range(vma, addr, start) < 0)
1787 			return NULL;	/* vma gone! */
1788 	}
1789 	return vma;
1790 }
1791 #endif
1792 
1793 /*
1794  * Ok - we have the memory areas we should free on the vma list,
1795  * so release them, and do the vma updates.
1796  *
1797  * Called with the mm semaphore held.
1798  */
1799 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1800 {
1801 	/* Update high watermark before we lower total_vm */
1802 	update_hiwater_vm(mm);
1803 	do {
1804 		long nrpages = vma_pages(vma);
1805 
1806 		mm->total_vm -= nrpages;
1807 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1808 		vma = remove_vma(vma);
1809 	} while (vma);
1810 	validate_mm(mm);
1811 }
1812 
1813 /*
1814  * Get rid of page table information in the indicated region.
1815  *
1816  * Called with the mm semaphore held.
1817  */
1818 static void unmap_region(struct mm_struct *mm,
1819 		struct vm_area_struct *vma, struct vm_area_struct *prev,
1820 		unsigned long start, unsigned long end)
1821 {
1822 	struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1823 	struct mmu_gather *tlb;
1824 	unsigned long nr_accounted = 0;
1825 
1826 	lru_add_drain();
1827 	tlb = tlb_gather_mmu(mm, 0);
1828 	update_hiwater_rss(mm);
1829 	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1830 	vm_unacct_memory(nr_accounted);
1831 	free_pgtables(tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
1832 				 next? next->vm_start: 0);
1833 	tlb_finish_mmu(tlb, start, end);
1834 }
1835 
1836 /*
1837  * Create a list of vma's touched by the unmap, removing them from the mm's
1838  * vma list as we go..
1839  */
1840 static void
1841 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1842 	struct vm_area_struct *prev, unsigned long end)
1843 {
1844 	struct vm_area_struct **insertion_point;
1845 	struct vm_area_struct *tail_vma = NULL;
1846 	unsigned long addr;
1847 
1848 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1849 	do {
1850 		rb_erase(&vma->vm_rb, &mm->mm_rb);
1851 		mm->map_count--;
1852 		tail_vma = vma;
1853 		vma = vma->vm_next;
1854 	} while (vma && vma->vm_start < end);
1855 	*insertion_point = vma;
1856 	tail_vma->vm_next = NULL;
1857 	if (mm->unmap_area == arch_unmap_area)
1858 		addr = prev ? prev->vm_end : mm->mmap_base;
1859 	else
1860 		addr = vma ?  vma->vm_start : mm->mmap_base;
1861 	mm->unmap_area(mm, addr);
1862 	mm->mmap_cache = NULL;		/* Kill the cache. */
1863 }
1864 
1865 /*
1866  * __split_vma() bypasses sysctl_max_map_count checking.  We use this on the
1867  * munmap path where it doesn't make sense to fail.
1868  */
1869 static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1870 	      unsigned long addr, int new_below)
1871 {
1872 	struct mempolicy *pol;
1873 	struct vm_area_struct *new;
1874 
1875 	if (is_vm_hugetlb_page(vma) && (addr &
1876 					~(huge_page_mask(hstate_vma(vma)))))
1877 		return -EINVAL;
1878 
1879 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1880 	if (!new)
1881 		return -ENOMEM;
1882 
1883 	/* most fields are the same, copy all, and then fixup */
1884 	*new = *vma;
1885 
1886 	if (new_below)
1887 		new->vm_end = addr;
1888 	else {
1889 		new->vm_start = addr;
1890 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1891 	}
1892 
1893 	pol = mpol_dup(vma_policy(vma));
1894 	if (IS_ERR(pol)) {
1895 		kmem_cache_free(vm_area_cachep, new);
1896 		return PTR_ERR(pol);
1897 	}
1898 	vma_set_policy(new, pol);
1899 
1900 	if (new->vm_file) {
1901 		get_file(new->vm_file);
1902 		if (vma->vm_flags & VM_EXECUTABLE)
1903 			added_exe_file_vma(mm);
1904 	}
1905 
1906 	if (new->vm_ops && new->vm_ops->open)
1907 		new->vm_ops->open(new);
1908 
1909 	if (new_below)
1910 		vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1911 			((addr - new->vm_start) >> PAGE_SHIFT), new);
1912 	else
1913 		vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1914 
1915 	return 0;
1916 }
1917 
1918 /*
1919  * Split a vma into two pieces at address 'addr', a new vma is allocated
1920  * either for the first part or the tail.
1921  */
1922 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1923 	      unsigned long addr, int new_below)
1924 {
1925 	if (mm->map_count >= sysctl_max_map_count)
1926 		return -ENOMEM;
1927 
1928 	return __split_vma(mm, vma, addr, new_below);
1929 }
1930 
1931 /* Munmap is split into 2 main parts -- this part which finds
1932  * what needs doing, and the areas themselves, which do the
1933  * work.  This now handles partial unmappings.
1934  * Jeremy Fitzhardinge <jeremy@goop.org>
1935  */
1936 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1937 {
1938 	unsigned long end;
1939 	struct vm_area_struct *vma, *prev, *last;
1940 
1941 	if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
1942 		return -EINVAL;
1943 
1944 	if ((len = PAGE_ALIGN(len)) == 0)
1945 		return -EINVAL;
1946 
1947 	/* Find the first overlapping VMA */
1948 	vma = find_vma_prev(mm, start, &prev);
1949 	if (!vma)
1950 		return 0;
1951 	/* we have  start < vma->vm_end  */
1952 
1953 	/* if it doesn't overlap, we have nothing.. */
1954 	end = start + len;
1955 	if (vma->vm_start >= end)
1956 		return 0;
1957 
1958 	/*
1959 	 * If we need to split any vma, do it now to save pain later.
1960 	 *
1961 	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
1962 	 * unmapped vm_area_struct will remain in use: so lower split_vma
1963 	 * places tmp vma above, and higher split_vma places tmp vma below.
1964 	 */
1965 	if (start > vma->vm_start) {
1966 		int error;
1967 
1968 		/*
1969 		 * Make sure that map_count on return from munmap() will
1970 		 * not exceed its limit; but let map_count go just above
1971 		 * its limit temporarily, to help free resources as expected.
1972 		 */
1973 		if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
1974 			return -ENOMEM;
1975 
1976 		error = __split_vma(mm, vma, start, 0);
1977 		if (error)
1978 			return error;
1979 		prev = vma;
1980 	}
1981 
1982 	/* Does it split the last one? */
1983 	last = find_vma(mm, end);
1984 	if (last && end > last->vm_start) {
1985 		int error = __split_vma(mm, last, end, 1);
1986 		if (error)
1987 			return error;
1988 	}
1989 	vma = prev? prev->vm_next: mm->mmap;
1990 
1991 	/*
1992 	 * unlock any mlock()ed ranges before detaching vmas
1993 	 */
1994 	if (mm->locked_vm) {
1995 		struct vm_area_struct *tmp = vma;
1996 		while (tmp && tmp->vm_start < end) {
1997 			if (tmp->vm_flags & VM_LOCKED) {
1998 				mm->locked_vm -= vma_pages(tmp);
1999 				munlock_vma_pages_all(tmp);
2000 			}
2001 			tmp = tmp->vm_next;
2002 		}
2003 	}
2004 
2005 	/*
2006 	 * Remove the vma's, and unmap the actual pages
2007 	 */
2008 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
2009 	unmap_region(mm, vma, prev, start, end);
2010 
2011 	/* Fix up all other VM information */
2012 	remove_vma_list(mm, vma);
2013 
2014 	return 0;
2015 }
2016 
2017 EXPORT_SYMBOL(do_munmap);
2018 
2019 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2020 {
2021 	int ret;
2022 	struct mm_struct *mm = current->mm;
2023 
2024 	profile_munmap(addr);
2025 
2026 	down_write(&mm->mmap_sem);
2027 	ret = do_munmap(mm, addr, len);
2028 	up_write(&mm->mmap_sem);
2029 	return ret;
2030 }
2031 
2032 static inline void verify_mm_writelocked(struct mm_struct *mm)
2033 {
2034 #ifdef CONFIG_DEBUG_VM
2035 	if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2036 		WARN_ON(1);
2037 		up_read(&mm->mmap_sem);
2038 	}
2039 #endif
2040 }
2041 
2042 /*
2043  *  this is really a simplified "do_mmap".  it only handles
2044  *  anonymous maps.  eventually we may be able to do some
2045  *  brk-specific accounting here.
2046  */
2047 unsigned long do_brk(unsigned long addr, unsigned long len)
2048 {
2049 	struct mm_struct * mm = current->mm;
2050 	struct vm_area_struct * vma, * prev;
2051 	unsigned long flags;
2052 	struct rb_node ** rb_link, * rb_parent;
2053 	pgoff_t pgoff = addr >> PAGE_SHIFT;
2054 	int error;
2055 
2056 	len = PAGE_ALIGN(len);
2057 	if (!len)
2058 		return addr;
2059 
2060 	error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
2061 	if (error)
2062 		return error;
2063 
2064 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2065 
2066 	error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2067 	if (error & ~PAGE_MASK)
2068 		return error;
2069 
2070 	/*
2071 	 * mlock MCL_FUTURE?
2072 	 */
2073 	if (mm->def_flags & VM_LOCKED) {
2074 		unsigned long locked, lock_limit;
2075 		locked = len >> PAGE_SHIFT;
2076 		locked += mm->locked_vm;
2077 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
2078 		lock_limit >>= PAGE_SHIFT;
2079 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2080 			return -EAGAIN;
2081 	}
2082 
2083 	/*
2084 	 * mm->mmap_sem is required to protect against another thread
2085 	 * changing the mappings in case we sleep.
2086 	 */
2087 	verify_mm_writelocked(mm);
2088 
2089 	/*
2090 	 * Clear old maps.  this also does some error checking for us
2091 	 */
2092  munmap_back:
2093 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2094 	if (vma && vma->vm_start < addr + len) {
2095 		if (do_munmap(mm, addr, len))
2096 			return -ENOMEM;
2097 		goto munmap_back;
2098 	}
2099 
2100 	/* Check against address space limits *after* clearing old maps... */
2101 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2102 		return -ENOMEM;
2103 
2104 	if (mm->map_count > sysctl_max_map_count)
2105 		return -ENOMEM;
2106 
2107 	if (security_vm_enough_memory(len >> PAGE_SHIFT))
2108 		return -ENOMEM;
2109 
2110 	/* Can we just expand an old private anonymous mapping? */
2111 	vma = vma_merge(mm, prev, addr, addr + len, flags,
2112 					NULL, NULL, pgoff, NULL);
2113 	if (vma)
2114 		goto out;
2115 
2116 	/*
2117 	 * create a vma struct for an anonymous mapping
2118 	 */
2119 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2120 	if (!vma) {
2121 		vm_unacct_memory(len >> PAGE_SHIFT);
2122 		return -ENOMEM;
2123 	}
2124 
2125 	vma->vm_mm = mm;
2126 	vma->vm_start = addr;
2127 	vma->vm_end = addr + len;
2128 	vma->vm_pgoff = pgoff;
2129 	vma->vm_flags = flags;
2130 	vma->vm_page_prot = vm_get_page_prot(flags);
2131 	vma_link(mm, vma, prev, rb_link, rb_parent);
2132 out:
2133 	mm->total_vm += len >> PAGE_SHIFT;
2134 	if (flags & VM_LOCKED) {
2135 		if (!mlock_vma_pages_range(vma, addr, addr + len))
2136 			mm->locked_vm += (len >> PAGE_SHIFT);
2137 	}
2138 	return addr;
2139 }
2140 
2141 EXPORT_SYMBOL(do_brk);
2142 
2143 /* Release all mmaps. */
2144 void exit_mmap(struct mm_struct *mm)
2145 {
2146 	struct mmu_gather *tlb;
2147 	struct vm_area_struct *vma;
2148 	unsigned long nr_accounted = 0;
2149 	unsigned long end;
2150 
2151 	/* mm's last user has gone, and its about to be pulled down */
2152 	mmu_notifier_release(mm);
2153 
2154 	if (mm->locked_vm) {
2155 		vma = mm->mmap;
2156 		while (vma) {
2157 			if (vma->vm_flags & VM_LOCKED)
2158 				munlock_vma_pages_all(vma);
2159 			vma = vma->vm_next;
2160 		}
2161 	}
2162 
2163 	arch_exit_mmap(mm);
2164 
2165 	vma = mm->mmap;
2166 	if (!vma)	/* Can happen if dup_mmap() received an OOM */
2167 		return;
2168 
2169 	lru_add_drain();
2170 	flush_cache_mm(mm);
2171 	tlb = tlb_gather_mmu(mm, 1);
2172 	/* update_hiwater_rss(mm) here? but nobody should be looking */
2173 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
2174 	end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
2175 	vm_unacct_memory(nr_accounted);
2176 
2177 	free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0);
2178 	tlb_finish_mmu(tlb, 0, end);
2179 
2180 	/*
2181 	 * Walk the list again, actually closing and freeing it,
2182 	 * with preemption enabled, without holding any MM locks.
2183 	 */
2184 	while (vma)
2185 		vma = remove_vma(vma);
2186 
2187 	BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2188 }
2189 
2190 /* Insert vm structure into process list sorted by address
2191  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2192  * then i_mmap_lock is taken here.
2193  */
2194 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2195 {
2196 	struct vm_area_struct * __vma, * prev;
2197 	struct rb_node ** rb_link, * rb_parent;
2198 
2199 	/*
2200 	 * The vm_pgoff of a purely anonymous vma should be irrelevant
2201 	 * until its first write fault, when page's anon_vma and index
2202 	 * are set.  But now set the vm_pgoff it will almost certainly
2203 	 * end up with (unless mremap moves it elsewhere before that
2204 	 * first wfault), so /proc/pid/maps tells a consistent story.
2205 	 *
2206 	 * By setting it to reflect the virtual start address of the
2207 	 * vma, merges and splits can happen in a seamless way, just
2208 	 * using the existing file pgoff checks and manipulations.
2209 	 * Similarly in do_mmap_pgoff and in do_brk.
2210 	 */
2211 	if (!vma->vm_file) {
2212 		BUG_ON(vma->anon_vma);
2213 		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2214 	}
2215 	__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2216 	if (__vma && __vma->vm_start < vma->vm_end)
2217 		return -ENOMEM;
2218 	if ((vma->vm_flags & VM_ACCOUNT) &&
2219 	     security_vm_enough_memory_mm(mm, vma_pages(vma)))
2220 		return -ENOMEM;
2221 	vma_link(mm, vma, prev, rb_link, rb_parent);
2222 	return 0;
2223 }
2224 
2225 /*
2226  * Copy the vma structure to a new location in the same mm,
2227  * prior to moving page table entries, to effect an mremap move.
2228  */
2229 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2230 	unsigned long addr, unsigned long len, pgoff_t pgoff)
2231 {
2232 	struct vm_area_struct *vma = *vmap;
2233 	unsigned long vma_start = vma->vm_start;
2234 	struct mm_struct *mm = vma->vm_mm;
2235 	struct vm_area_struct *new_vma, *prev;
2236 	struct rb_node **rb_link, *rb_parent;
2237 	struct mempolicy *pol;
2238 
2239 	/*
2240 	 * If anonymous vma has not yet been faulted, update new pgoff
2241 	 * to match new location, to increase its chance of merging.
2242 	 */
2243 	if (!vma->vm_file && !vma->anon_vma)
2244 		pgoff = addr >> PAGE_SHIFT;
2245 
2246 	find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2247 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2248 			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2249 	if (new_vma) {
2250 		/*
2251 		 * Source vma may have been merged into new_vma
2252 		 */
2253 		if (vma_start >= new_vma->vm_start &&
2254 		    vma_start < new_vma->vm_end)
2255 			*vmap = new_vma;
2256 	} else {
2257 		new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2258 		if (new_vma) {
2259 			*new_vma = *vma;
2260 			pol = mpol_dup(vma_policy(vma));
2261 			if (IS_ERR(pol)) {
2262 				kmem_cache_free(vm_area_cachep, new_vma);
2263 				return NULL;
2264 			}
2265 			vma_set_policy(new_vma, pol);
2266 			new_vma->vm_start = addr;
2267 			new_vma->vm_end = addr + len;
2268 			new_vma->vm_pgoff = pgoff;
2269 			if (new_vma->vm_file) {
2270 				get_file(new_vma->vm_file);
2271 				if (vma->vm_flags & VM_EXECUTABLE)
2272 					added_exe_file_vma(mm);
2273 			}
2274 			if (new_vma->vm_ops && new_vma->vm_ops->open)
2275 				new_vma->vm_ops->open(new_vma);
2276 			vma_link(mm, new_vma, prev, rb_link, rb_parent);
2277 		}
2278 	}
2279 	return new_vma;
2280 }
2281 
2282 /*
2283  * Return true if the calling process may expand its vm space by the passed
2284  * number of pages
2285  */
2286 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2287 {
2288 	unsigned long cur = mm->total_vm;	/* pages */
2289 	unsigned long lim;
2290 
2291 	lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
2292 
2293 	if (cur + npages > lim)
2294 		return 0;
2295 	return 1;
2296 }
2297 
2298 
2299 static int special_mapping_fault(struct vm_area_struct *vma,
2300 				struct vm_fault *vmf)
2301 {
2302 	pgoff_t pgoff;
2303 	struct page **pages;
2304 
2305 	/*
2306 	 * special mappings have no vm_file, and in that case, the mm
2307 	 * uses vm_pgoff internally. So we have to subtract it from here.
2308 	 * We are allowed to do this because we are the mm; do not copy
2309 	 * this code into drivers!
2310 	 */
2311 	pgoff = vmf->pgoff - vma->vm_pgoff;
2312 
2313 	for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2314 		pgoff--;
2315 
2316 	if (*pages) {
2317 		struct page *page = *pages;
2318 		get_page(page);
2319 		vmf->page = page;
2320 		return 0;
2321 	}
2322 
2323 	return VM_FAULT_SIGBUS;
2324 }
2325 
2326 /*
2327  * Having a close hook prevents vma merging regardless of flags.
2328  */
2329 static void special_mapping_close(struct vm_area_struct *vma)
2330 {
2331 }
2332 
2333 static const struct vm_operations_struct special_mapping_vmops = {
2334 	.close = special_mapping_close,
2335 	.fault = special_mapping_fault,
2336 };
2337 
2338 /*
2339  * Called with mm->mmap_sem held for writing.
2340  * Insert a new vma covering the given region, with the given flags.
2341  * Its pages are supplied by the given array of struct page *.
2342  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2343  * The region past the last page supplied will always produce SIGBUS.
2344  * The array pointer and the pages it points to are assumed to stay alive
2345  * for as long as this mapping might exist.
2346  */
2347 int install_special_mapping(struct mm_struct *mm,
2348 			    unsigned long addr, unsigned long len,
2349 			    unsigned long vm_flags, struct page **pages)
2350 {
2351 	struct vm_area_struct *vma;
2352 
2353 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2354 	if (unlikely(vma == NULL))
2355 		return -ENOMEM;
2356 
2357 	vma->vm_mm = mm;
2358 	vma->vm_start = addr;
2359 	vma->vm_end = addr + len;
2360 
2361 	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2362 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2363 
2364 	vma->vm_ops = &special_mapping_vmops;
2365 	vma->vm_private_data = pages;
2366 
2367 	if (unlikely(insert_vm_struct(mm, vma))) {
2368 		kmem_cache_free(vm_area_cachep, vma);
2369 		return -ENOMEM;
2370 	}
2371 
2372 	mm->total_vm += len >> PAGE_SHIFT;
2373 
2374 	perf_event_mmap(vma);
2375 
2376 	return 0;
2377 }
2378 
2379 static DEFINE_MUTEX(mm_all_locks_mutex);
2380 
2381 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2382 {
2383 	if (!test_bit(0, (unsigned long *) &anon_vma->head.next)) {
2384 		/*
2385 		 * The LSB of head.next can't change from under us
2386 		 * because we hold the mm_all_locks_mutex.
2387 		 */
2388 		spin_lock_nest_lock(&anon_vma->lock, &mm->mmap_sem);
2389 		/*
2390 		 * We can safely modify head.next after taking the
2391 		 * anon_vma->lock. If some other vma in this mm shares
2392 		 * the same anon_vma we won't take it again.
2393 		 *
2394 		 * No need of atomic instructions here, head.next
2395 		 * can't change from under us thanks to the
2396 		 * anon_vma->lock.
2397 		 */
2398 		if (__test_and_set_bit(0, (unsigned long *)
2399 				       &anon_vma->head.next))
2400 			BUG();
2401 	}
2402 }
2403 
2404 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2405 {
2406 	if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2407 		/*
2408 		 * AS_MM_ALL_LOCKS can't change from under us because
2409 		 * we hold the mm_all_locks_mutex.
2410 		 *
2411 		 * Operations on ->flags have to be atomic because
2412 		 * even if AS_MM_ALL_LOCKS is stable thanks to the
2413 		 * mm_all_locks_mutex, there may be other cpus
2414 		 * changing other bitflags in parallel to us.
2415 		 */
2416 		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2417 			BUG();
2418 		spin_lock_nest_lock(&mapping->i_mmap_lock, &mm->mmap_sem);
2419 	}
2420 }
2421 
2422 /*
2423  * This operation locks against the VM for all pte/vma/mm related
2424  * operations that could ever happen on a certain mm. This includes
2425  * vmtruncate, try_to_unmap, and all page faults.
2426  *
2427  * The caller must take the mmap_sem in write mode before calling
2428  * mm_take_all_locks(). The caller isn't allowed to release the
2429  * mmap_sem until mm_drop_all_locks() returns.
2430  *
2431  * mmap_sem in write mode is required in order to block all operations
2432  * that could modify pagetables and free pages without need of
2433  * altering the vma layout (for example populate_range() with
2434  * nonlinear vmas). It's also needed in write mode to avoid new
2435  * anon_vmas to be associated with existing vmas.
2436  *
2437  * A single task can't take more than one mm_take_all_locks() in a row
2438  * or it would deadlock.
2439  *
2440  * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in
2441  * mapping->flags avoid to take the same lock twice, if more than one
2442  * vma in this mm is backed by the same anon_vma or address_space.
2443  *
2444  * We can take all the locks in random order because the VM code
2445  * taking i_mmap_lock or anon_vma->lock outside the mmap_sem never
2446  * takes more than one of them in a row. Secondly we're protected
2447  * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2448  *
2449  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2450  * that may have to take thousand of locks.
2451  *
2452  * mm_take_all_locks() can fail if it's interrupted by signals.
2453  */
2454 int mm_take_all_locks(struct mm_struct *mm)
2455 {
2456 	struct vm_area_struct *vma;
2457 	int ret = -EINTR;
2458 
2459 	BUG_ON(down_read_trylock(&mm->mmap_sem));
2460 
2461 	mutex_lock(&mm_all_locks_mutex);
2462 
2463 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2464 		if (signal_pending(current))
2465 			goto out_unlock;
2466 		if (vma->vm_file && vma->vm_file->f_mapping)
2467 			vm_lock_mapping(mm, vma->vm_file->f_mapping);
2468 	}
2469 
2470 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2471 		if (signal_pending(current))
2472 			goto out_unlock;
2473 		if (vma->anon_vma)
2474 			vm_lock_anon_vma(mm, vma->anon_vma);
2475 	}
2476 
2477 	ret = 0;
2478 
2479 out_unlock:
2480 	if (ret)
2481 		mm_drop_all_locks(mm);
2482 
2483 	return ret;
2484 }
2485 
2486 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2487 {
2488 	if (test_bit(0, (unsigned long *) &anon_vma->head.next)) {
2489 		/*
2490 		 * The LSB of head.next can't change to 0 from under
2491 		 * us because we hold the mm_all_locks_mutex.
2492 		 *
2493 		 * We must however clear the bitflag before unlocking
2494 		 * the vma so the users using the anon_vma->head will
2495 		 * never see our bitflag.
2496 		 *
2497 		 * No need of atomic instructions here, head.next
2498 		 * can't change from under us until we release the
2499 		 * anon_vma->lock.
2500 		 */
2501 		if (!__test_and_clear_bit(0, (unsigned long *)
2502 					  &anon_vma->head.next))
2503 			BUG();
2504 		spin_unlock(&anon_vma->lock);
2505 	}
2506 }
2507 
2508 static void vm_unlock_mapping(struct address_space *mapping)
2509 {
2510 	if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2511 		/*
2512 		 * AS_MM_ALL_LOCKS can't change to 0 from under us
2513 		 * because we hold the mm_all_locks_mutex.
2514 		 */
2515 		spin_unlock(&mapping->i_mmap_lock);
2516 		if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2517 					&mapping->flags))
2518 			BUG();
2519 	}
2520 }
2521 
2522 /*
2523  * The mmap_sem cannot be released by the caller until
2524  * mm_drop_all_locks() returns.
2525  */
2526 void mm_drop_all_locks(struct mm_struct *mm)
2527 {
2528 	struct vm_area_struct *vma;
2529 
2530 	BUG_ON(down_read_trylock(&mm->mmap_sem));
2531 	BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2532 
2533 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2534 		if (vma->anon_vma)
2535 			vm_unlock_anon_vma(vma->anon_vma);
2536 		if (vma->vm_file && vma->vm_file->f_mapping)
2537 			vm_unlock_mapping(vma->vm_file->f_mapping);
2538 	}
2539 
2540 	mutex_unlock(&mm_all_locks_mutex);
2541 }
2542 
2543 /*
2544  * initialise the VMA slab
2545  */
2546 void __init mmap_init(void)
2547 {
2548 	int ret;
2549 
2550 	ret = percpu_counter_init(&vm_committed_as, 0);
2551 	VM_BUG_ON(ret);
2552 }
2553