xref: /openbmc/linux/mm/mmap.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * mm/mmap.c
3  *
4  * Written by obz.
5  *
6  * Address space accounting code	<alan@redhat.com>
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/mm.h>
11 #include <linux/shm.h>
12 #include <linux/mman.h>
13 #include <linux/pagemap.h>
14 #include <linux/swap.h>
15 #include <linux/syscalls.h>
16 #include <linux/init.h>
17 #include <linux/file.h>
18 #include <linux/fs.h>
19 #include <linux/personality.h>
20 #include <linux/security.h>
21 #include <linux/hugetlb.h>
22 #include <linux/profile.h>
23 #include <linux/module.h>
24 #include <linux/mount.h>
25 #include <linux/mempolicy.h>
26 #include <linux/rmap.h>
27 
28 #include <asm/uaccess.h>
29 #include <asm/cacheflush.h>
30 #include <asm/tlb.h>
31 
32 static void unmap_region(struct mm_struct *mm,
33 		struct vm_area_struct *vma, struct vm_area_struct *prev,
34 		unsigned long start, unsigned long end);
35 
36 /*
37  * WARNING: the debugging will use recursive algorithms so never enable this
38  * unless you know what you are doing.
39  */
40 #undef DEBUG_MM_RB
41 
42 /* description of effects of mapping type and prot in current implementation.
43  * this is due to the limited x86 page protection hardware.  The expected
44  * behavior is in parens:
45  *
46  * map_type	prot
47  *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
48  * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
49  *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
50  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
51  *
52  * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
53  *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
54  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
55  *
56  */
57 pgprot_t protection_map[16] = {
58 	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
59 	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
60 };
61 
62 int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
63 int sysctl_overcommit_ratio = 50;	/* default is 50% */
64 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
65 atomic_t vm_committed_space = ATOMIC_INIT(0);
66 
67 /*
68  * Check that a process has enough memory to allocate a new virtual
69  * mapping. 0 means there is enough memory for the allocation to
70  * succeed and -ENOMEM implies there is not.
71  *
72  * We currently support three overcommit policies, which are set via the
73  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
74  *
75  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
76  * Additional code 2002 Jul 20 by Robert Love.
77  *
78  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
79  *
80  * Note this is a helper function intended to be used by LSMs which
81  * wish to use this logic.
82  */
83 int __vm_enough_memory(long pages, int cap_sys_admin)
84 {
85 	unsigned long free, allowed;
86 
87 	vm_acct_memory(pages);
88 
89 	/*
90 	 * Sometimes we want to use more memory than we have
91 	 */
92 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
93 		return 0;
94 
95 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
96 		unsigned long n;
97 
98 		free = get_page_cache_size();
99 		free += nr_swap_pages;
100 
101 		/*
102 		 * Any slabs which are created with the
103 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
104 		 * which are reclaimable, under pressure.  The dentry
105 		 * cache and most inode caches should fall into this
106 		 */
107 		free += atomic_read(&slab_reclaim_pages);
108 
109 		/*
110 		 * Leave the last 3% for root
111 		 */
112 		if (!cap_sys_admin)
113 			free -= free / 32;
114 
115 		if (free > pages)
116 			return 0;
117 
118 		/*
119 		 * nr_free_pages() is very expensive on large systems,
120 		 * only call if we're about to fail.
121 		 */
122 		n = nr_free_pages();
123 		if (!cap_sys_admin)
124 			n -= n / 32;
125 		free += n;
126 
127 		if (free > pages)
128 			return 0;
129 		vm_unacct_memory(pages);
130 		return -ENOMEM;
131 	}
132 
133 	allowed = (totalram_pages - hugetlb_total_pages())
134 	       	* sysctl_overcommit_ratio / 100;
135 	/*
136 	 * Leave the last 3% for root
137 	 */
138 	if (!cap_sys_admin)
139 		allowed -= allowed / 32;
140 	allowed += total_swap_pages;
141 
142 	/* Don't let a single process grow too big:
143 	   leave 3% of the size of this process for other processes */
144 	allowed -= current->mm->total_vm / 32;
145 
146 	/*
147 	 * cast `allowed' as a signed long because vm_committed_space
148 	 * sometimes has a negative value
149 	 */
150 	if (atomic_read(&vm_committed_space) < (long)allowed)
151 		return 0;
152 
153 	vm_unacct_memory(pages);
154 
155 	return -ENOMEM;
156 }
157 
158 EXPORT_SYMBOL(sysctl_overcommit_memory);
159 EXPORT_SYMBOL(sysctl_overcommit_ratio);
160 EXPORT_SYMBOL(sysctl_max_map_count);
161 EXPORT_SYMBOL(vm_committed_space);
162 EXPORT_SYMBOL(__vm_enough_memory);
163 
164 /*
165  * Requires inode->i_mapping->i_mmap_lock
166  */
167 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
168 		struct file *file, struct address_space *mapping)
169 {
170 	if (vma->vm_flags & VM_DENYWRITE)
171 		atomic_inc(&file->f_dentry->d_inode->i_writecount);
172 	if (vma->vm_flags & VM_SHARED)
173 		mapping->i_mmap_writable--;
174 
175 	flush_dcache_mmap_lock(mapping);
176 	if (unlikely(vma->vm_flags & VM_NONLINEAR))
177 		list_del_init(&vma->shared.vm_set.list);
178 	else
179 		vma_prio_tree_remove(vma, &mapping->i_mmap);
180 	flush_dcache_mmap_unlock(mapping);
181 }
182 
183 /*
184  * Unlink a file-based vm structure from its prio_tree, to hide
185  * vma from rmap and vmtruncate before freeing its page tables.
186  */
187 void unlink_file_vma(struct vm_area_struct *vma)
188 {
189 	struct file *file = vma->vm_file;
190 
191 	if (file) {
192 		struct address_space *mapping = file->f_mapping;
193 		spin_lock(&mapping->i_mmap_lock);
194 		__remove_shared_vm_struct(vma, file, mapping);
195 		spin_unlock(&mapping->i_mmap_lock);
196 	}
197 }
198 
199 /*
200  * Close a vm structure and free it, returning the next.
201  */
202 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
203 {
204 	struct vm_area_struct *next = vma->vm_next;
205 
206 	might_sleep();
207 	if (vma->vm_ops && vma->vm_ops->close)
208 		vma->vm_ops->close(vma);
209 	if (vma->vm_file)
210 		fput(vma->vm_file);
211 	mpol_free(vma_policy(vma));
212 	kmem_cache_free(vm_area_cachep, vma);
213 	return next;
214 }
215 
216 asmlinkage unsigned long sys_brk(unsigned long brk)
217 {
218 	unsigned long rlim, retval;
219 	unsigned long newbrk, oldbrk;
220 	struct mm_struct *mm = current->mm;
221 
222 	down_write(&mm->mmap_sem);
223 
224 	if (brk < mm->end_code)
225 		goto out;
226 	newbrk = PAGE_ALIGN(brk);
227 	oldbrk = PAGE_ALIGN(mm->brk);
228 	if (oldbrk == newbrk)
229 		goto set_brk;
230 
231 	/* Always allow shrinking brk. */
232 	if (brk <= mm->brk) {
233 		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
234 			goto set_brk;
235 		goto out;
236 	}
237 
238 	/* Check against rlimit.. */
239 	rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
240 	if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
241 		goto out;
242 
243 	/* Check against existing mmap mappings. */
244 	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
245 		goto out;
246 
247 	/* Ok, looks good - let it rip. */
248 	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
249 		goto out;
250 set_brk:
251 	mm->brk = brk;
252 out:
253 	retval = mm->brk;
254 	up_write(&mm->mmap_sem);
255 	return retval;
256 }
257 
258 #ifdef DEBUG_MM_RB
259 static int browse_rb(struct rb_root *root)
260 {
261 	int i = 0, j;
262 	struct rb_node *nd, *pn = NULL;
263 	unsigned long prev = 0, pend = 0;
264 
265 	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
266 		struct vm_area_struct *vma;
267 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
268 		if (vma->vm_start < prev)
269 			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
270 		if (vma->vm_start < pend)
271 			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
272 		if (vma->vm_start > vma->vm_end)
273 			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
274 		i++;
275 		pn = nd;
276 	}
277 	j = 0;
278 	for (nd = pn; nd; nd = rb_prev(nd)) {
279 		j++;
280 	}
281 	if (i != j)
282 		printk("backwards %d, forwards %d\n", j, i), i = 0;
283 	return i;
284 }
285 
286 void validate_mm(struct mm_struct *mm)
287 {
288 	int bug = 0;
289 	int i = 0;
290 	struct vm_area_struct *tmp = mm->mmap;
291 	while (tmp) {
292 		tmp = tmp->vm_next;
293 		i++;
294 	}
295 	if (i != mm->map_count)
296 		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
297 	i = browse_rb(&mm->mm_rb);
298 	if (i != mm->map_count)
299 		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
300 	if (bug)
301 		BUG();
302 }
303 #else
304 #define validate_mm(mm) do { } while (0)
305 #endif
306 
307 static struct vm_area_struct *
308 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
309 		struct vm_area_struct **pprev, struct rb_node ***rb_link,
310 		struct rb_node ** rb_parent)
311 {
312 	struct vm_area_struct * vma;
313 	struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
314 
315 	__rb_link = &mm->mm_rb.rb_node;
316 	rb_prev = __rb_parent = NULL;
317 	vma = NULL;
318 
319 	while (*__rb_link) {
320 		struct vm_area_struct *vma_tmp;
321 
322 		__rb_parent = *__rb_link;
323 		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
324 
325 		if (vma_tmp->vm_end > addr) {
326 			vma = vma_tmp;
327 			if (vma_tmp->vm_start <= addr)
328 				return vma;
329 			__rb_link = &__rb_parent->rb_left;
330 		} else {
331 			rb_prev = __rb_parent;
332 			__rb_link = &__rb_parent->rb_right;
333 		}
334 	}
335 
336 	*pprev = NULL;
337 	if (rb_prev)
338 		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
339 	*rb_link = __rb_link;
340 	*rb_parent = __rb_parent;
341 	return vma;
342 }
343 
344 static inline void
345 __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
346 		struct vm_area_struct *prev, struct rb_node *rb_parent)
347 {
348 	if (prev) {
349 		vma->vm_next = prev->vm_next;
350 		prev->vm_next = vma;
351 	} else {
352 		mm->mmap = vma;
353 		if (rb_parent)
354 			vma->vm_next = rb_entry(rb_parent,
355 					struct vm_area_struct, vm_rb);
356 		else
357 			vma->vm_next = NULL;
358 	}
359 }
360 
361 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
362 		struct rb_node **rb_link, struct rb_node *rb_parent)
363 {
364 	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
365 	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
366 }
367 
368 static inline void __vma_link_file(struct vm_area_struct *vma)
369 {
370 	struct file * file;
371 
372 	file = vma->vm_file;
373 	if (file) {
374 		struct address_space *mapping = file->f_mapping;
375 
376 		if (vma->vm_flags & VM_DENYWRITE)
377 			atomic_dec(&file->f_dentry->d_inode->i_writecount);
378 		if (vma->vm_flags & VM_SHARED)
379 			mapping->i_mmap_writable++;
380 
381 		flush_dcache_mmap_lock(mapping);
382 		if (unlikely(vma->vm_flags & VM_NONLINEAR))
383 			vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
384 		else
385 			vma_prio_tree_insert(vma, &mapping->i_mmap);
386 		flush_dcache_mmap_unlock(mapping);
387 	}
388 }
389 
390 static void
391 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
392 	struct vm_area_struct *prev, struct rb_node **rb_link,
393 	struct rb_node *rb_parent)
394 {
395 	__vma_link_list(mm, vma, prev, rb_parent);
396 	__vma_link_rb(mm, vma, rb_link, rb_parent);
397 	__anon_vma_link(vma);
398 }
399 
400 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
401 			struct vm_area_struct *prev, struct rb_node **rb_link,
402 			struct rb_node *rb_parent)
403 {
404 	struct address_space *mapping = NULL;
405 
406 	if (vma->vm_file)
407 		mapping = vma->vm_file->f_mapping;
408 
409 	if (mapping) {
410 		spin_lock(&mapping->i_mmap_lock);
411 		vma->vm_truncate_count = mapping->truncate_count;
412 	}
413 	anon_vma_lock(vma);
414 
415 	__vma_link(mm, vma, prev, rb_link, rb_parent);
416 	__vma_link_file(vma);
417 
418 	anon_vma_unlock(vma);
419 	if (mapping)
420 		spin_unlock(&mapping->i_mmap_lock);
421 
422 	mm->map_count++;
423 	validate_mm(mm);
424 }
425 
426 /*
427  * Helper for vma_adjust in the split_vma insert case:
428  * insert vm structure into list and rbtree and anon_vma,
429  * but it has already been inserted into prio_tree earlier.
430  */
431 static void
432 __insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
433 {
434 	struct vm_area_struct * __vma, * prev;
435 	struct rb_node ** rb_link, * rb_parent;
436 
437 	__vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
438 	if (__vma && __vma->vm_start < vma->vm_end)
439 		BUG();
440 	__vma_link(mm, vma, prev, rb_link, rb_parent);
441 	mm->map_count++;
442 }
443 
444 static inline void
445 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
446 		struct vm_area_struct *prev)
447 {
448 	prev->vm_next = vma->vm_next;
449 	rb_erase(&vma->vm_rb, &mm->mm_rb);
450 	if (mm->mmap_cache == vma)
451 		mm->mmap_cache = prev;
452 }
453 
454 /*
455  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
456  * is already present in an i_mmap tree without adjusting the tree.
457  * The following helper function should be used when such adjustments
458  * are necessary.  The "insert" vma (if any) is to be inserted
459  * before we drop the necessary locks.
460  */
461 void vma_adjust(struct vm_area_struct *vma, unsigned long start,
462 	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
463 {
464 	struct mm_struct *mm = vma->vm_mm;
465 	struct vm_area_struct *next = vma->vm_next;
466 	struct vm_area_struct *importer = NULL;
467 	struct address_space *mapping = NULL;
468 	struct prio_tree_root *root = NULL;
469 	struct file *file = vma->vm_file;
470 	struct anon_vma *anon_vma = NULL;
471 	long adjust_next = 0;
472 	int remove_next = 0;
473 
474 	if (next && !insert) {
475 		if (end >= next->vm_end) {
476 			/*
477 			 * vma expands, overlapping all the next, and
478 			 * perhaps the one after too (mprotect case 6).
479 			 */
480 again:			remove_next = 1 + (end > next->vm_end);
481 			end = next->vm_end;
482 			anon_vma = next->anon_vma;
483 			importer = vma;
484 		} else if (end > next->vm_start) {
485 			/*
486 			 * vma expands, overlapping part of the next:
487 			 * mprotect case 5 shifting the boundary up.
488 			 */
489 			adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
490 			anon_vma = next->anon_vma;
491 			importer = vma;
492 		} else if (end < vma->vm_end) {
493 			/*
494 			 * vma shrinks, and !insert tells it's not
495 			 * split_vma inserting another: so it must be
496 			 * mprotect case 4 shifting the boundary down.
497 			 */
498 			adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
499 			anon_vma = next->anon_vma;
500 			importer = next;
501 		}
502 	}
503 
504 	if (file) {
505 		mapping = file->f_mapping;
506 		if (!(vma->vm_flags & VM_NONLINEAR))
507 			root = &mapping->i_mmap;
508 		spin_lock(&mapping->i_mmap_lock);
509 		if (importer &&
510 		    vma->vm_truncate_count != next->vm_truncate_count) {
511 			/*
512 			 * unmap_mapping_range might be in progress:
513 			 * ensure that the expanding vma is rescanned.
514 			 */
515 			importer->vm_truncate_count = 0;
516 		}
517 		if (insert) {
518 			insert->vm_truncate_count = vma->vm_truncate_count;
519 			/*
520 			 * Put into prio_tree now, so instantiated pages
521 			 * are visible to arm/parisc __flush_dcache_page
522 			 * throughout; but we cannot insert into address
523 			 * space until vma start or end is updated.
524 			 */
525 			__vma_link_file(insert);
526 		}
527 	}
528 
529 	/*
530 	 * When changing only vma->vm_end, we don't really need
531 	 * anon_vma lock: but is that case worth optimizing out?
532 	 */
533 	if (vma->anon_vma)
534 		anon_vma = vma->anon_vma;
535 	if (anon_vma) {
536 		spin_lock(&anon_vma->lock);
537 		/*
538 		 * Easily overlooked: when mprotect shifts the boundary,
539 		 * make sure the expanding vma has anon_vma set if the
540 		 * shrinking vma had, to cover any anon pages imported.
541 		 */
542 		if (importer && !importer->anon_vma) {
543 			importer->anon_vma = anon_vma;
544 			__anon_vma_link(importer);
545 		}
546 	}
547 
548 	if (root) {
549 		flush_dcache_mmap_lock(mapping);
550 		vma_prio_tree_remove(vma, root);
551 		if (adjust_next)
552 			vma_prio_tree_remove(next, root);
553 	}
554 
555 	vma->vm_start = start;
556 	vma->vm_end = end;
557 	vma->vm_pgoff = pgoff;
558 	if (adjust_next) {
559 		next->vm_start += adjust_next << PAGE_SHIFT;
560 		next->vm_pgoff += adjust_next;
561 	}
562 
563 	if (root) {
564 		if (adjust_next)
565 			vma_prio_tree_insert(next, root);
566 		vma_prio_tree_insert(vma, root);
567 		flush_dcache_mmap_unlock(mapping);
568 	}
569 
570 	if (remove_next) {
571 		/*
572 		 * vma_merge has merged next into vma, and needs
573 		 * us to remove next before dropping the locks.
574 		 */
575 		__vma_unlink(mm, next, vma);
576 		if (file)
577 			__remove_shared_vm_struct(next, file, mapping);
578 		if (next->anon_vma)
579 			__anon_vma_merge(vma, next);
580 	} else if (insert) {
581 		/*
582 		 * split_vma has split insert from vma, and needs
583 		 * us to insert it before dropping the locks
584 		 * (it may either follow vma or precede it).
585 		 */
586 		__insert_vm_struct(mm, insert);
587 	}
588 
589 	if (anon_vma)
590 		spin_unlock(&anon_vma->lock);
591 	if (mapping)
592 		spin_unlock(&mapping->i_mmap_lock);
593 
594 	if (remove_next) {
595 		if (file)
596 			fput(file);
597 		mm->map_count--;
598 		mpol_free(vma_policy(next));
599 		kmem_cache_free(vm_area_cachep, next);
600 		/*
601 		 * In mprotect's case 6 (see comments on vma_merge),
602 		 * we must remove another next too. It would clutter
603 		 * up the code too much to do both in one go.
604 		 */
605 		if (remove_next == 2) {
606 			next = vma->vm_next;
607 			goto again;
608 		}
609 	}
610 
611 	validate_mm(mm);
612 }
613 
614 /*
615  * If the vma has a ->close operation then the driver probably needs to release
616  * per-vma resources, so we don't attempt to merge those.
617  */
618 #define VM_SPECIAL (VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_RESERVED)
619 
620 static inline int is_mergeable_vma(struct vm_area_struct *vma,
621 			struct file *file, unsigned long vm_flags)
622 {
623 	if (vma->vm_flags != vm_flags)
624 		return 0;
625 	if (vma->vm_file != file)
626 		return 0;
627 	if (vma->vm_ops && vma->vm_ops->close)
628 		return 0;
629 	return 1;
630 }
631 
632 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
633 					struct anon_vma *anon_vma2)
634 {
635 	return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
636 }
637 
638 /*
639  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
640  * in front of (at a lower virtual address and file offset than) the vma.
641  *
642  * We cannot merge two vmas if they have differently assigned (non-NULL)
643  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
644  *
645  * We don't check here for the merged mmap wrapping around the end of pagecache
646  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
647  * wrap, nor mmaps which cover the final page at index -1UL.
648  */
649 static int
650 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
651 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
652 {
653 	if (is_mergeable_vma(vma, file, vm_flags) &&
654 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
655 		if (vma->vm_pgoff == vm_pgoff)
656 			return 1;
657 	}
658 	return 0;
659 }
660 
661 /*
662  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
663  * beyond (at a higher virtual address and file offset than) the vma.
664  *
665  * We cannot merge two vmas if they have differently assigned (non-NULL)
666  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
667  */
668 static int
669 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
670 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
671 {
672 	if (is_mergeable_vma(vma, file, vm_flags) &&
673 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
674 		pgoff_t vm_pglen;
675 		vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
676 		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
677 			return 1;
678 	}
679 	return 0;
680 }
681 
682 /*
683  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
684  * whether that can be merged with its predecessor or its successor.
685  * Or both (it neatly fills a hole).
686  *
687  * In most cases - when called for mmap, brk or mremap - [addr,end) is
688  * certain not to be mapped by the time vma_merge is called; but when
689  * called for mprotect, it is certain to be already mapped (either at
690  * an offset within prev, or at the start of next), and the flags of
691  * this area are about to be changed to vm_flags - and the no-change
692  * case has already been eliminated.
693  *
694  * The following mprotect cases have to be considered, where AAAA is
695  * the area passed down from mprotect_fixup, never extending beyond one
696  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
697  *
698  *     AAAA             AAAA                AAAA          AAAA
699  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
700  *    cannot merge    might become    might become    might become
701  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
702  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
703  *    mremap move:                                    PPPPNNNNNNNN 8
704  *        AAAA
705  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
706  *    might become    case 1 below    case 2 below    case 3 below
707  *
708  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
709  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
710  */
711 struct vm_area_struct *vma_merge(struct mm_struct *mm,
712 			struct vm_area_struct *prev, unsigned long addr,
713 			unsigned long end, unsigned long vm_flags,
714 		     	struct anon_vma *anon_vma, struct file *file,
715 			pgoff_t pgoff, struct mempolicy *policy)
716 {
717 	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
718 	struct vm_area_struct *area, *next;
719 
720 	/*
721 	 * We later require that vma->vm_flags == vm_flags,
722 	 * so this tests vma->vm_flags & VM_SPECIAL, too.
723 	 */
724 	if (vm_flags & VM_SPECIAL)
725 		return NULL;
726 
727 	if (prev)
728 		next = prev->vm_next;
729 	else
730 		next = mm->mmap;
731 	area = next;
732 	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
733 		next = next->vm_next;
734 
735 	/*
736 	 * Can it merge with the predecessor?
737 	 */
738 	if (prev && prev->vm_end == addr &&
739   			mpol_equal(vma_policy(prev), policy) &&
740 			can_vma_merge_after(prev, vm_flags,
741 						anon_vma, file, pgoff)) {
742 		/*
743 		 * OK, it can.  Can we now merge in the successor as well?
744 		 */
745 		if (next && end == next->vm_start &&
746 				mpol_equal(policy, vma_policy(next)) &&
747 				can_vma_merge_before(next, vm_flags,
748 					anon_vma, file, pgoff+pglen) &&
749 				is_mergeable_anon_vma(prev->anon_vma,
750 						      next->anon_vma)) {
751 							/* cases 1, 6 */
752 			vma_adjust(prev, prev->vm_start,
753 				next->vm_end, prev->vm_pgoff, NULL);
754 		} else					/* cases 2, 5, 7 */
755 			vma_adjust(prev, prev->vm_start,
756 				end, prev->vm_pgoff, NULL);
757 		return prev;
758 	}
759 
760 	/*
761 	 * Can this new request be merged in front of next?
762 	 */
763 	if (next && end == next->vm_start &&
764  			mpol_equal(policy, vma_policy(next)) &&
765 			can_vma_merge_before(next, vm_flags,
766 					anon_vma, file, pgoff+pglen)) {
767 		if (prev && addr < prev->vm_end)	/* case 4 */
768 			vma_adjust(prev, prev->vm_start,
769 				addr, prev->vm_pgoff, NULL);
770 		else					/* cases 3, 8 */
771 			vma_adjust(area, addr, next->vm_end,
772 				next->vm_pgoff - pglen, NULL);
773 		return area;
774 	}
775 
776 	return NULL;
777 }
778 
779 /*
780  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
781  * neighbouring vmas for a suitable anon_vma, before it goes off
782  * to allocate a new anon_vma.  It checks because a repetitive
783  * sequence of mprotects and faults may otherwise lead to distinct
784  * anon_vmas being allocated, preventing vma merge in subsequent
785  * mprotect.
786  */
787 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
788 {
789 	struct vm_area_struct *near;
790 	unsigned long vm_flags;
791 
792 	near = vma->vm_next;
793 	if (!near)
794 		goto try_prev;
795 
796 	/*
797 	 * Since only mprotect tries to remerge vmas, match flags
798 	 * which might be mprotected into each other later on.
799 	 * Neither mlock nor madvise tries to remerge at present,
800 	 * so leave their flags as obstructing a merge.
801 	 */
802 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
803 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
804 
805 	if (near->anon_vma && vma->vm_end == near->vm_start &&
806  			mpol_equal(vma_policy(vma), vma_policy(near)) &&
807 			can_vma_merge_before(near, vm_flags,
808 				NULL, vma->vm_file, vma->vm_pgoff +
809 				((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)))
810 		return near->anon_vma;
811 try_prev:
812 	/*
813 	 * It is potentially slow to have to call find_vma_prev here.
814 	 * But it's only on the first write fault on the vma, not
815 	 * every time, and we could devise a way to avoid it later
816 	 * (e.g. stash info in next's anon_vma_node when assigning
817 	 * an anon_vma, or when trying vma_merge).  Another time.
818 	 */
819 	if (find_vma_prev(vma->vm_mm, vma->vm_start, &near) != vma)
820 		BUG();
821 	if (!near)
822 		goto none;
823 
824 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
825 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
826 
827 	if (near->anon_vma && near->vm_end == vma->vm_start &&
828   			mpol_equal(vma_policy(near), vma_policy(vma)) &&
829 			can_vma_merge_after(near, vm_flags,
830 				NULL, vma->vm_file, vma->vm_pgoff))
831 		return near->anon_vma;
832 none:
833 	/*
834 	 * There's no absolute need to look only at touching neighbours:
835 	 * we could search further afield for "compatible" anon_vmas.
836 	 * But it would probably just be a waste of time searching,
837 	 * or lead to too many vmas hanging off the same anon_vma.
838 	 * We're trying to allow mprotect remerging later on,
839 	 * not trying to minimize memory used for anon_vmas.
840 	 */
841 	return NULL;
842 }
843 
844 #ifdef CONFIG_PROC_FS
845 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
846 						struct file *file, long pages)
847 {
848 	const unsigned long stack_flags
849 		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
850 
851 #ifdef CONFIG_HUGETLB
852 	if (flags & VM_HUGETLB) {
853 		if (!(flags & VM_DONTCOPY))
854 			mm->shared_vm += pages;
855 		return;
856 	}
857 #endif /* CONFIG_HUGETLB */
858 
859 	if (file) {
860 		mm->shared_vm += pages;
861 		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
862 			mm->exec_vm += pages;
863 	} else if (flags & stack_flags)
864 		mm->stack_vm += pages;
865 	if (flags & (VM_RESERVED|VM_IO))
866 		mm->reserved_vm += pages;
867 }
868 #endif /* CONFIG_PROC_FS */
869 
870 /*
871  * The caller must hold down_write(current->mm->mmap_sem).
872  */
873 
874 unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
875 			unsigned long len, unsigned long prot,
876 			unsigned long flags, unsigned long pgoff)
877 {
878 	struct mm_struct * mm = current->mm;
879 	struct vm_area_struct * vma, * prev;
880 	struct inode *inode;
881 	unsigned int vm_flags;
882 	int correct_wcount = 0;
883 	int error;
884 	struct rb_node ** rb_link, * rb_parent;
885 	int accountable = 1;
886 	unsigned long charged = 0, reqprot = prot;
887 
888 	if (file) {
889 		if (is_file_hugepages(file))
890 			accountable = 0;
891 
892 		if (!file->f_op || !file->f_op->mmap)
893 			return -ENODEV;
894 
895 		if ((prot & PROT_EXEC) &&
896 		    (file->f_vfsmnt->mnt_flags & MNT_NOEXEC))
897 			return -EPERM;
898 	}
899 	/*
900 	 * Does the application expect PROT_READ to imply PROT_EXEC?
901 	 *
902 	 * (the exception is when the underlying filesystem is noexec
903 	 *  mounted, in which case we dont add PROT_EXEC.)
904 	 */
905 	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
906 		if (!(file && (file->f_vfsmnt->mnt_flags & MNT_NOEXEC)))
907 			prot |= PROT_EXEC;
908 
909 	if (!len)
910 		return -EINVAL;
911 
912 	/* Careful about overflows.. */
913 	len = PAGE_ALIGN(len);
914 	if (!len || len > TASK_SIZE)
915 		return -ENOMEM;
916 
917 	/* offset overflow? */
918 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
919                return -EOVERFLOW;
920 
921 	/* Too many mappings? */
922 	if (mm->map_count > sysctl_max_map_count)
923 		return -ENOMEM;
924 
925 	/* Obtain the address to map to. we verify (or select) it and ensure
926 	 * that it represents a valid section of the address space.
927 	 */
928 	addr = get_unmapped_area(file, addr, len, pgoff, flags);
929 	if (addr & ~PAGE_MASK)
930 		return addr;
931 
932 	/* Do simple checking here so the lower-level routines won't have
933 	 * to. we assume access permissions have been handled by the open
934 	 * of the memory object, so we don't do any here.
935 	 */
936 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
937 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
938 
939 	if (flags & MAP_LOCKED) {
940 		if (!can_do_mlock())
941 			return -EPERM;
942 		vm_flags |= VM_LOCKED;
943 	}
944 	/* mlock MCL_FUTURE? */
945 	if (vm_flags & VM_LOCKED) {
946 		unsigned long locked, lock_limit;
947 		locked = len >> PAGE_SHIFT;
948 		locked += mm->locked_vm;
949 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
950 		lock_limit >>= PAGE_SHIFT;
951 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
952 			return -EAGAIN;
953 	}
954 
955 	inode = file ? file->f_dentry->d_inode : NULL;
956 
957 	if (file) {
958 		switch (flags & MAP_TYPE) {
959 		case MAP_SHARED:
960 			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
961 				return -EACCES;
962 
963 			/*
964 			 * Make sure we don't allow writing to an append-only
965 			 * file..
966 			 */
967 			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
968 				return -EACCES;
969 
970 			/*
971 			 * Make sure there are no mandatory locks on the file.
972 			 */
973 			if (locks_verify_locked(inode))
974 				return -EAGAIN;
975 
976 			vm_flags |= VM_SHARED | VM_MAYSHARE;
977 			if (!(file->f_mode & FMODE_WRITE))
978 				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
979 
980 			/* fall through */
981 		case MAP_PRIVATE:
982 			if (!(file->f_mode & FMODE_READ))
983 				return -EACCES;
984 			break;
985 
986 		default:
987 			return -EINVAL;
988 		}
989 	} else {
990 		switch (flags & MAP_TYPE) {
991 		case MAP_SHARED:
992 			vm_flags |= VM_SHARED | VM_MAYSHARE;
993 			break;
994 		case MAP_PRIVATE:
995 			/*
996 			 * Set pgoff according to addr for anon_vma.
997 			 */
998 			pgoff = addr >> PAGE_SHIFT;
999 			break;
1000 		default:
1001 			return -EINVAL;
1002 		}
1003 	}
1004 
1005 	error = security_file_mmap(file, reqprot, prot, flags);
1006 	if (error)
1007 		return error;
1008 
1009 	/* Clear old maps */
1010 	error = -ENOMEM;
1011 munmap_back:
1012 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1013 	if (vma && vma->vm_start < addr + len) {
1014 		if (do_munmap(mm, addr, len))
1015 			return -ENOMEM;
1016 		goto munmap_back;
1017 	}
1018 
1019 	/* Check against address space limit. */
1020 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1021 		return -ENOMEM;
1022 
1023 	if (accountable && (!(flags & MAP_NORESERVE) ||
1024 			    sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
1025 		if (vm_flags & VM_SHARED) {
1026 			/* Check memory availability in shmem_file_setup? */
1027 			vm_flags |= VM_ACCOUNT;
1028 		} else if (vm_flags & VM_WRITE) {
1029 			/*
1030 			 * Private writable mapping: check memory availability
1031 			 */
1032 			charged = len >> PAGE_SHIFT;
1033 			if (security_vm_enough_memory(charged))
1034 				return -ENOMEM;
1035 			vm_flags |= VM_ACCOUNT;
1036 		}
1037 	}
1038 
1039 	/*
1040 	 * Can we just expand an old private anonymous mapping?
1041 	 * The VM_SHARED test is necessary because shmem_zero_setup
1042 	 * will create the file object for a shared anonymous map below.
1043 	 */
1044 	if (!file && !(vm_flags & VM_SHARED) &&
1045 	    vma_merge(mm, prev, addr, addr + len, vm_flags,
1046 					NULL, NULL, pgoff, NULL))
1047 		goto out;
1048 
1049 	/*
1050 	 * Determine the object being mapped and call the appropriate
1051 	 * specific mapper. the address has already been validated, but
1052 	 * not unmapped, but the maps are removed from the list.
1053 	 */
1054 	vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
1055 	if (!vma) {
1056 		error = -ENOMEM;
1057 		goto unacct_error;
1058 	}
1059 	memset(vma, 0, sizeof(*vma));
1060 
1061 	vma->vm_mm = mm;
1062 	vma->vm_start = addr;
1063 	vma->vm_end = addr + len;
1064 	vma->vm_flags = vm_flags;
1065 	vma->vm_page_prot = protection_map[vm_flags & 0x0f];
1066 	vma->vm_pgoff = pgoff;
1067 
1068 	if (file) {
1069 		error = -EINVAL;
1070 		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1071 			goto free_vma;
1072 		if (vm_flags & VM_DENYWRITE) {
1073 			error = deny_write_access(file);
1074 			if (error)
1075 				goto free_vma;
1076 			correct_wcount = 1;
1077 		}
1078 		vma->vm_file = file;
1079 		get_file(file);
1080 		error = file->f_op->mmap(file, vma);
1081 		if (error)
1082 			goto unmap_and_free_vma;
1083 		if ((vma->vm_flags & (VM_SHARED | VM_WRITE | VM_RESERVED))
1084 						== (VM_WRITE | VM_RESERVED)) {
1085 			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
1086 				"PROT_WRITE mmap of VM_RESERVED memory, which "
1087 				"is deprecated. Please report this to "
1088 				"linux-kernel@vger.kernel.org\n",current->comm);
1089 			if (vma->vm_ops && vma->vm_ops->close)
1090 				vma->vm_ops->close(vma);
1091 			error = -EACCES;
1092 			goto unmap_and_free_vma;
1093 		}
1094 	} else if (vm_flags & VM_SHARED) {
1095 		error = shmem_zero_setup(vma);
1096 		if (error)
1097 			goto free_vma;
1098 	}
1099 
1100 	/* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform
1101 	 * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)
1102 	 * that memory reservation must be checked; but that reservation
1103 	 * belongs to shared memory object, not to vma: so now clear it.
1104 	 */
1105 	if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))
1106 		vma->vm_flags &= ~VM_ACCOUNT;
1107 
1108 	/* Can addr have changed??
1109 	 *
1110 	 * Answer: Yes, several device drivers can do it in their
1111 	 *         f_op->mmap method. -DaveM
1112 	 */
1113 	addr = vma->vm_start;
1114 	pgoff = vma->vm_pgoff;
1115 	vm_flags = vma->vm_flags;
1116 
1117 	if (!file || !vma_merge(mm, prev, addr, vma->vm_end,
1118 			vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
1119 		file = vma->vm_file;
1120 		vma_link(mm, vma, prev, rb_link, rb_parent);
1121 		if (correct_wcount)
1122 			atomic_inc(&inode->i_writecount);
1123 	} else {
1124 		if (file) {
1125 			if (correct_wcount)
1126 				atomic_inc(&inode->i_writecount);
1127 			fput(file);
1128 		}
1129 		mpol_free(vma_policy(vma));
1130 		kmem_cache_free(vm_area_cachep, vma);
1131 	}
1132 out:
1133 	mm->total_vm += len >> PAGE_SHIFT;
1134 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1135 	if (vm_flags & VM_LOCKED) {
1136 		mm->locked_vm += len >> PAGE_SHIFT;
1137 		make_pages_present(addr, addr + len);
1138 	}
1139 	if (flags & MAP_POPULATE) {
1140 		up_write(&mm->mmap_sem);
1141 		sys_remap_file_pages(addr, len, 0,
1142 					pgoff, flags & MAP_NONBLOCK);
1143 		down_write(&mm->mmap_sem);
1144 	}
1145 	return addr;
1146 
1147 unmap_and_free_vma:
1148 	if (correct_wcount)
1149 		atomic_inc(&inode->i_writecount);
1150 	vma->vm_file = NULL;
1151 	fput(file);
1152 
1153 	/* Undo any partial mapping done by a device driver. */
1154 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1155 	charged = 0;
1156 free_vma:
1157 	kmem_cache_free(vm_area_cachep, vma);
1158 unacct_error:
1159 	if (charged)
1160 		vm_unacct_memory(charged);
1161 	return error;
1162 }
1163 
1164 EXPORT_SYMBOL(do_mmap_pgoff);
1165 
1166 /* Get an address range which is currently unmapped.
1167  * For shmat() with addr=0.
1168  *
1169  * Ugly calling convention alert:
1170  * Return value with the low bits set means error value,
1171  * ie
1172  *	if (ret & ~PAGE_MASK)
1173  *		error = ret;
1174  *
1175  * This function "knows" that -ENOMEM has the bits set.
1176  */
1177 #ifndef HAVE_ARCH_UNMAPPED_AREA
1178 unsigned long
1179 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1180 		unsigned long len, unsigned long pgoff, unsigned long flags)
1181 {
1182 	struct mm_struct *mm = current->mm;
1183 	struct vm_area_struct *vma;
1184 	unsigned long start_addr;
1185 
1186 	if (len > TASK_SIZE)
1187 		return -ENOMEM;
1188 
1189 	if (addr) {
1190 		addr = PAGE_ALIGN(addr);
1191 		vma = find_vma(mm, addr);
1192 		if (TASK_SIZE - len >= addr &&
1193 		    (!vma || addr + len <= vma->vm_start))
1194 			return addr;
1195 	}
1196 	if (len > mm->cached_hole_size) {
1197 	        start_addr = addr = mm->free_area_cache;
1198 	} else {
1199 	        start_addr = addr = TASK_UNMAPPED_BASE;
1200 	        mm->cached_hole_size = 0;
1201 	}
1202 
1203 full_search:
1204 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1205 		/* At this point:  (!vma || addr < vma->vm_end). */
1206 		if (TASK_SIZE - len < addr) {
1207 			/*
1208 			 * Start a new search - just in case we missed
1209 			 * some holes.
1210 			 */
1211 			if (start_addr != TASK_UNMAPPED_BASE) {
1212 				addr = TASK_UNMAPPED_BASE;
1213 			        start_addr = addr;
1214 				mm->cached_hole_size = 0;
1215 				goto full_search;
1216 			}
1217 			return -ENOMEM;
1218 		}
1219 		if (!vma || addr + len <= vma->vm_start) {
1220 			/*
1221 			 * Remember the place where we stopped the search:
1222 			 */
1223 			mm->free_area_cache = addr + len;
1224 			return addr;
1225 		}
1226 		if (addr + mm->cached_hole_size < vma->vm_start)
1227 		        mm->cached_hole_size = vma->vm_start - addr;
1228 		addr = vma->vm_end;
1229 	}
1230 }
1231 #endif
1232 
1233 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1234 {
1235 	/*
1236 	 * Is this a new hole at the lowest possible address?
1237 	 */
1238 	if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1239 		mm->free_area_cache = addr;
1240 		mm->cached_hole_size = ~0UL;
1241 	}
1242 }
1243 
1244 /*
1245  * This mmap-allocator allocates new areas top-down from below the
1246  * stack's low limit (the base):
1247  */
1248 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1249 unsigned long
1250 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1251 			  const unsigned long len, const unsigned long pgoff,
1252 			  const unsigned long flags)
1253 {
1254 	struct vm_area_struct *vma;
1255 	struct mm_struct *mm = current->mm;
1256 	unsigned long addr = addr0;
1257 
1258 	/* requested length too big for entire address space */
1259 	if (len > TASK_SIZE)
1260 		return -ENOMEM;
1261 
1262 	/* requesting a specific address */
1263 	if (addr) {
1264 		addr = PAGE_ALIGN(addr);
1265 		vma = find_vma(mm, addr);
1266 		if (TASK_SIZE - len >= addr &&
1267 				(!vma || addr + len <= vma->vm_start))
1268 			return addr;
1269 	}
1270 
1271 	/* check if free_area_cache is useful for us */
1272 	if (len <= mm->cached_hole_size) {
1273  	        mm->cached_hole_size = 0;
1274  		mm->free_area_cache = mm->mmap_base;
1275  	}
1276 
1277 	/* either no address requested or can't fit in requested address hole */
1278 	addr = mm->free_area_cache;
1279 
1280 	/* make sure it can fit in the remaining address space */
1281 	if (addr > len) {
1282 		vma = find_vma(mm, addr-len);
1283 		if (!vma || addr <= vma->vm_start)
1284 			/* remember the address as a hint for next time */
1285 			return (mm->free_area_cache = addr-len);
1286 	}
1287 
1288 	if (mm->mmap_base < len)
1289 		goto bottomup;
1290 
1291 	addr = mm->mmap_base-len;
1292 
1293 	do {
1294 		/*
1295 		 * Lookup failure means no vma is above this address,
1296 		 * else if new region fits below vma->vm_start,
1297 		 * return with success:
1298 		 */
1299 		vma = find_vma(mm, addr);
1300 		if (!vma || addr+len <= vma->vm_start)
1301 			/* remember the address as a hint for next time */
1302 			return (mm->free_area_cache = addr);
1303 
1304  		/* remember the largest hole we saw so far */
1305  		if (addr + mm->cached_hole_size < vma->vm_start)
1306  		        mm->cached_hole_size = vma->vm_start - addr;
1307 
1308 		/* try just below the current vma->vm_start */
1309 		addr = vma->vm_start-len;
1310 	} while (len < vma->vm_start);
1311 
1312 bottomup:
1313 	/*
1314 	 * A failed mmap() very likely causes application failure,
1315 	 * so fall back to the bottom-up function here. This scenario
1316 	 * can happen with large stack limits and large mmap()
1317 	 * allocations.
1318 	 */
1319 	mm->cached_hole_size = ~0UL;
1320   	mm->free_area_cache = TASK_UNMAPPED_BASE;
1321 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1322 	/*
1323 	 * Restore the topdown base:
1324 	 */
1325 	mm->free_area_cache = mm->mmap_base;
1326 	mm->cached_hole_size = ~0UL;
1327 
1328 	return addr;
1329 }
1330 #endif
1331 
1332 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1333 {
1334 	/*
1335 	 * Is this a new hole at the highest possible address?
1336 	 */
1337 	if (addr > mm->free_area_cache)
1338 		mm->free_area_cache = addr;
1339 
1340 	/* dont allow allocations above current base */
1341 	if (mm->free_area_cache > mm->mmap_base)
1342 		mm->free_area_cache = mm->mmap_base;
1343 }
1344 
1345 unsigned long
1346 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1347 		unsigned long pgoff, unsigned long flags)
1348 {
1349 	unsigned long ret;
1350 
1351 	if (!(flags & MAP_FIXED)) {
1352 		unsigned long (*get_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
1353 
1354 		get_area = current->mm->get_unmapped_area;
1355 		if (file && file->f_op && file->f_op->get_unmapped_area)
1356 			get_area = file->f_op->get_unmapped_area;
1357 		addr = get_area(file, addr, len, pgoff, flags);
1358 		if (IS_ERR_VALUE(addr))
1359 			return addr;
1360 	}
1361 
1362 	if (addr > TASK_SIZE - len)
1363 		return -ENOMEM;
1364 	if (addr & ~PAGE_MASK)
1365 		return -EINVAL;
1366 	if (file && is_file_hugepages(file))  {
1367 		/*
1368 		 * Check if the given range is hugepage aligned, and
1369 		 * can be made suitable for hugepages.
1370 		 */
1371 		ret = prepare_hugepage_range(addr, len);
1372 	} else {
1373 		/*
1374 		 * Ensure that a normal request is not falling in a
1375 		 * reserved hugepage range.  For some archs like IA-64,
1376 		 * there is a separate region for hugepages.
1377 		 */
1378 		ret = is_hugepage_only_range(current->mm, addr, len);
1379 	}
1380 	if (ret)
1381 		return -EINVAL;
1382 	return addr;
1383 }
1384 
1385 EXPORT_SYMBOL(get_unmapped_area);
1386 
1387 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1388 struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr)
1389 {
1390 	struct vm_area_struct *vma = NULL;
1391 
1392 	if (mm) {
1393 		/* Check the cache first. */
1394 		/* (Cache hit rate is typically around 35%.) */
1395 		vma = mm->mmap_cache;
1396 		if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1397 			struct rb_node * rb_node;
1398 
1399 			rb_node = mm->mm_rb.rb_node;
1400 			vma = NULL;
1401 
1402 			while (rb_node) {
1403 				struct vm_area_struct * vma_tmp;
1404 
1405 				vma_tmp = rb_entry(rb_node,
1406 						struct vm_area_struct, vm_rb);
1407 
1408 				if (vma_tmp->vm_end > addr) {
1409 					vma = vma_tmp;
1410 					if (vma_tmp->vm_start <= addr)
1411 						break;
1412 					rb_node = rb_node->rb_left;
1413 				} else
1414 					rb_node = rb_node->rb_right;
1415 			}
1416 			if (vma)
1417 				mm->mmap_cache = vma;
1418 		}
1419 	}
1420 	return vma;
1421 }
1422 
1423 EXPORT_SYMBOL(find_vma);
1424 
1425 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1426 struct vm_area_struct *
1427 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1428 			struct vm_area_struct **pprev)
1429 {
1430 	struct vm_area_struct *vma = NULL, *prev = NULL;
1431 	struct rb_node * rb_node;
1432 	if (!mm)
1433 		goto out;
1434 
1435 	/* Guard against addr being lower than the first VMA */
1436 	vma = mm->mmap;
1437 
1438 	/* Go through the RB tree quickly. */
1439 	rb_node = mm->mm_rb.rb_node;
1440 
1441 	while (rb_node) {
1442 		struct vm_area_struct *vma_tmp;
1443 		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1444 
1445 		if (addr < vma_tmp->vm_end) {
1446 			rb_node = rb_node->rb_left;
1447 		} else {
1448 			prev = vma_tmp;
1449 			if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1450 				break;
1451 			rb_node = rb_node->rb_right;
1452 		}
1453 	}
1454 
1455 out:
1456 	*pprev = prev;
1457 	return prev ? prev->vm_next : vma;
1458 }
1459 
1460 /*
1461  * Verify that the stack growth is acceptable and
1462  * update accounting. This is shared with both the
1463  * grow-up and grow-down cases.
1464  */
1465 static int acct_stack_growth(struct vm_area_struct * vma, unsigned long size, unsigned long grow)
1466 {
1467 	struct mm_struct *mm = vma->vm_mm;
1468 	struct rlimit *rlim = current->signal->rlim;
1469 
1470 	/* address space limit tests */
1471 	if (!may_expand_vm(mm, grow))
1472 		return -ENOMEM;
1473 
1474 	/* Stack limit test */
1475 	if (size > rlim[RLIMIT_STACK].rlim_cur)
1476 		return -ENOMEM;
1477 
1478 	/* mlock limit tests */
1479 	if (vma->vm_flags & VM_LOCKED) {
1480 		unsigned long locked;
1481 		unsigned long limit;
1482 		locked = mm->locked_vm + grow;
1483 		limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
1484 		if (locked > limit && !capable(CAP_IPC_LOCK))
1485 			return -ENOMEM;
1486 	}
1487 
1488 	/*
1489 	 * Overcommit..  This must be the final test, as it will
1490 	 * update security statistics.
1491 	 */
1492 	if (security_vm_enough_memory(grow))
1493 		return -ENOMEM;
1494 
1495 	/* Ok, everything looks good - let it rip */
1496 	mm->total_vm += grow;
1497 	if (vma->vm_flags & VM_LOCKED)
1498 		mm->locked_vm += grow;
1499 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1500 	return 0;
1501 }
1502 
1503 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1504 /*
1505  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1506  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1507  */
1508 #ifdef CONFIG_STACK_GROWSUP
1509 static inline
1510 #endif
1511 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1512 {
1513 	int error;
1514 
1515 	if (!(vma->vm_flags & VM_GROWSUP))
1516 		return -EFAULT;
1517 
1518 	/*
1519 	 * We must make sure the anon_vma is allocated
1520 	 * so that the anon_vma locking is not a noop.
1521 	 */
1522 	if (unlikely(anon_vma_prepare(vma)))
1523 		return -ENOMEM;
1524 	anon_vma_lock(vma);
1525 
1526 	/*
1527 	 * vma->vm_start/vm_end cannot change under us because the caller
1528 	 * is required to hold the mmap_sem in read mode.  We need the
1529 	 * anon_vma lock to serialize against concurrent expand_stacks.
1530 	 */
1531 	address += 4 + PAGE_SIZE - 1;
1532 	address &= PAGE_MASK;
1533 	error = 0;
1534 
1535 	/* Somebody else might have raced and expanded it already */
1536 	if (address > vma->vm_end) {
1537 		unsigned long size, grow;
1538 
1539 		size = address - vma->vm_start;
1540 		grow = (address - vma->vm_end) >> PAGE_SHIFT;
1541 
1542 		error = acct_stack_growth(vma, size, grow);
1543 		if (!error)
1544 			vma->vm_end = address;
1545 	}
1546 	anon_vma_unlock(vma);
1547 	return error;
1548 }
1549 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1550 
1551 #ifdef CONFIG_STACK_GROWSUP
1552 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1553 {
1554 	return expand_upwards(vma, address);
1555 }
1556 
1557 struct vm_area_struct *
1558 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1559 {
1560 	struct vm_area_struct *vma, *prev;
1561 
1562 	addr &= PAGE_MASK;
1563 	vma = find_vma_prev(mm, addr, &prev);
1564 	if (vma && (vma->vm_start <= addr))
1565 		return vma;
1566 	if (!prev || expand_stack(prev, addr))
1567 		return NULL;
1568 	if (prev->vm_flags & VM_LOCKED) {
1569 		make_pages_present(addr, prev->vm_end);
1570 	}
1571 	return prev;
1572 }
1573 #else
1574 /*
1575  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1576  */
1577 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1578 {
1579 	int error;
1580 
1581 	/*
1582 	 * We must make sure the anon_vma is allocated
1583 	 * so that the anon_vma locking is not a noop.
1584 	 */
1585 	if (unlikely(anon_vma_prepare(vma)))
1586 		return -ENOMEM;
1587 	anon_vma_lock(vma);
1588 
1589 	/*
1590 	 * vma->vm_start/vm_end cannot change under us because the caller
1591 	 * is required to hold the mmap_sem in read mode.  We need the
1592 	 * anon_vma lock to serialize against concurrent expand_stacks.
1593 	 */
1594 	address &= PAGE_MASK;
1595 	error = 0;
1596 
1597 	/* Somebody else might have raced and expanded it already */
1598 	if (address < vma->vm_start) {
1599 		unsigned long size, grow;
1600 
1601 		size = vma->vm_end - address;
1602 		grow = (vma->vm_start - address) >> PAGE_SHIFT;
1603 
1604 		error = acct_stack_growth(vma, size, grow);
1605 		if (!error) {
1606 			vma->vm_start = address;
1607 			vma->vm_pgoff -= grow;
1608 		}
1609 	}
1610 	anon_vma_unlock(vma);
1611 	return error;
1612 }
1613 
1614 struct vm_area_struct *
1615 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1616 {
1617 	struct vm_area_struct * vma;
1618 	unsigned long start;
1619 
1620 	addr &= PAGE_MASK;
1621 	vma = find_vma(mm,addr);
1622 	if (!vma)
1623 		return NULL;
1624 	if (vma->vm_start <= addr)
1625 		return vma;
1626 	if (!(vma->vm_flags & VM_GROWSDOWN))
1627 		return NULL;
1628 	start = vma->vm_start;
1629 	if (expand_stack(vma, addr))
1630 		return NULL;
1631 	if (vma->vm_flags & VM_LOCKED) {
1632 		make_pages_present(addr, start);
1633 	}
1634 	return vma;
1635 }
1636 #endif
1637 
1638 /*
1639  * Ok - we have the memory areas we should free on the vma list,
1640  * so release them, and do the vma updates.
1641  *
1642  * Called with the mm semaphore held.
1643  */
1644 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1645 {
1646 	/* Update high watermark before we lower total_vm */
1647 	update_hiwater_vm(mm);
1648 	do {
1649 		long nrpages = vma_pages(vma);
1650 
1651 		mm->total_vm -= nrpages;
1652 		if (vma->vm_flags & VM_LOCKED)
1653 			mm->locked_vm -= nrpages;
1654 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1655 		vma = remove_vma(vma);
1656 	} while (vma);
1657 	validate_mm(mm);
1658 }
1659 
1660 /*
1661  * Get rid of page table information in the indicated region.
1662  *
1663  * Called with the mm semaphore held.
1664  */
1665 static void unmap_region(struct mm_struct *mm,
1666 		struct vm_area_struct *vma, struct vm_area_struct *prev,
1667 		unsigned long start, unsigned long end)
1668 {
1669 	struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1670 	struct mmu_gather *tlb;
1671 	unsigned long nr_accounted = 0;
1672 
1673 	lru_add_drain();
1674 	tlb = tlb_gather_mmu(mm, 0);
1675 	update_hiwater_rss(mm);
1676 	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1677 	vm_unacct_memory(nr_accounted);
1678 	free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
1679 				 next? next->vm_start: 0);
1680 	tlb_finish_mmu(tlb, start, end);
1681 }
1682 
1683 /*
1684  * Create a list of vma's touched by the unmap, removing them from the mm's
1685  * vma list as we go..
1686  */
1687 static void
1688 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1689 	struct vm_area_struct *prev, unsigned long end)
1690 {
1691 	struct vm_area_struct **insertion_point;
1692 	struct vm_area_struct *tail_vma = NULL;
1693 	unsigned long addr;
1694 
1695 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1696 	do {
1697 		rb_erase(&vma->vm_rb, &mm->mm_rb);
1698 		mm->map_count--;
1699 		tail_vma = vma;
1700 		vma = vma->vm_next;
1701 	} while (vma && vma->vm_start < end);
1702 	*insertion_point = vma;
1703 	tail_vma->vm_next = NULL;
1704 	if (mm->unmap_area == arch_unmap_area)
1705 		addr = prev ? prev->vm_end : mm->mmap_base;
1706 	else
1707 		addr = vma ?  vma->vm_start : mm->mmap_base;
1708 	mm->unmap_area(mm, addr);
1709 	mm->mmap_cache = NULL;		/* Kill the cache. */
1710 }
1711 
1712 /*
1713  * Split a vma into two pieces at address 'addr', a new vma is allocated
1714  * either for the first part or the the tail.
1715  */
1716 int split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1717 	      unsigned long addr, int new_below)
1718 {
1719 	struct mempolicy *pol;
1720 	struct vm_area_struct *new;
1721 
1722 	if (is_vm_hugetlb_page(vma) && (addr & ~HPAGE_MASK))
1723 		return -EINVAL;
1724 
1725 	if (mm->map_count >= sysctl_max_map_count)
1726 		return -ENOMEM;
1727 
1728 	new = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
1729 	if (!new)
1730 		return -ENOMEM;
1731 
1732 	/* most fields are the same, copy all, and then fixup */
1733 	*new = *vma;
1734 
1735 	if (new_below)
1736 		new->vm_end = addr;
1737 	else {
1738 		new->vm_start = addr;
1739 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1740 	}
1741 
1742 	pol = mpol_copy(vma_policy(vma));
1743 	if (IS_ERR(pol)) {
1744 		kmem_cache_free(vm_area_cachep, new);
1745 		return PTR_ERR(pol);
1746 	}
1747 	vma_set_policy(new, pol);
1748 
1749 	if (new->vm_file)
1750 		get_file(new->vm_file);
1751 
1752 	if (new->vm_ops && new->vm_ops->open)
1753 		new->vm_ops->open(new);
1754 
1755 	if (new_below)
1756 		vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1757 			((addr - new->vm_start) >> PAGE_SHIFT), new);
1758 	else
1759 		vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1760 
1761 	return 0;
1762 }
1763 
1764 /* Munmap is split into 2 main parts -- this part which finds
1765  * what needs doing, and the areas themselves, which do the
1766  * work.  This now handles partial unmappings.
1767  * Jeremy Fitzhardinge <jeremy@goop.org>
1768  */
1769 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1770 {
1771 	unsigned long end;
1772 	struct vm_area_struct *vma, *prev, *last;
1773 
1774 	if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
1775 		return -EINVAL;
1776 
1777 	if ((len = PAGE_ALIGN(len)) == 0)
1778 		return -EINVAL;
1779 
1780 	/* Find the first overlapping VMA */
1781 	vma = find_vma_prev(mm, start, &prev);
1782 	if (!vma)
1783 		return 0;
1784 	/* we have  start < vma->vm_end  */
1785 
1786 	/* if it doesn't overlap, we have nothing.. */
1787 	end = start + len;
1788 	if (vma->vm_start >= end)
1789 		return 0;
1790 
1791 	/*
1792 	 * If we need to split any vma, do it now to save pain later.
1793 	 *
1794 	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
1795 	 * unmapped vm_area_struct will remain in use: so lower split_vma
1796 	 * places tmp vma above, and higher split_vma places tmp vma below.
1797 	 */
1798 	if (start > vma->vm_start) {
1799 		int error = split_vma(mm, vma, start, 0);
1800 		if (error)
1801 			return error;
1802 		prev = vma;
1803 	}
1804 
1805 	/* Does it split the last one? */
1806 	last = find_vma(mm, end);
1807 	if (last && end > last->vm_start) {
1808 		int error = split_vma(mm, last, end, 1);
1809 		if (error)
1810 			return error;
1811 	}
1812 	vma = prev? prev->vm_next: mm->mmap;
1813 
1814 	/*
1815 	 * Remove the vma's, and unmap the actual pages
1816 	 */
1817 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
1818 	unmap_region(mm, vma, prev, start, end);
1819 
1820 	/* Fix up all other VM information */
1821 	remove_vma_list(mm, vma);
1822 
1823 	return 0;
1824 }
1825 
1826 EXPORT_SYMBOL(do_munmap);
1827 
1828 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1829 {
1830 	int ret;
1831 	struct mm_struct *mm = current->mm;
1832 
1833 	profile_munmap(addr);
1834 
1835 	down_write(&mm->mmap_sem);
1836 	ret = do_munmap(mm, addr, len);
1837 	up_write(&mm->mmap_sem);
1838 	return ret;
1839 }
1840 
1841 static inline void verify_mm_writelocked(struct mm_struct *mm)
1842 {
1843 #ifdef CONFIG_DEBUG_VM
1844 	if (unlikely(down_read_trylock(&mm->mmap_sem))) {
1845 		WARN_ON(1);
1846 		up_read(&mm->mmap_sem);
1847 	}
1848 #endif
1849 }
1850 
1851 /*
1852  *  this is really a simplified "do_mmap".  it only handles
1853  *  anonymous maps.  eventually we may be able to do some
1854  *  brk-specific accounting here.
1855  */
1856 unsigned long do_brk(unsigned long addr, unsigned long len)
1857 {
1858 	struct mm_struct * mm = current->mm;
1859 	struct vm_area_struct * vma, * prev;
1860 	unsigned long flags;
1861 	struct rb_node ** rb_link, * rb_parent;
1862 	pgoff_t pgoff = addr >> PAGE_SHIFT;
1863 
1864 	len = PAGE_ALIGN(len);
1865 	if (!len)
1866 		return addr;
1867 
1868 	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
1869 		return -EINVAL;
1870 
1871 	/*
1872 	 * mlock MCL_FUTURE?
1873 	 */
1874 	if (mm->def_flags & VM_LOCKED) {
1875 		unsigned long locked, lock_limit;
1876 		locked = len >> PAGE_SHIFT;
1877 		locked += mm->locked_vm;
1878 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
1879 		lock_limit >>= PAGE_SHIFT;
1880 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1881 			return -EAGAIN;
1882 	}
1883 
1884 	/*
1885 	 * mm->mmap_sem is required to protect against another thread
1886 	 * changing the mappings in case we sleep.
1887 	 */
1888 	verify_mm_writelocked(mm);
1889 
1890 	/*
1891 	 * Clear old maps.  this also does some error checking for us
1892 	 */
1893  munmap_back:
1894 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1895 	if (vma && vma->vm_start < addr + len) {
1896 		if (do_munmap(mm, addr, len))
1897 			return -ENOMEM;
1898 		goto munmap_back;
1899 	}
1900 
1901 	/* Check against address space limits *after* clearing old maps... */
1902 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1903 		return -ENOMEM;
1904 
1905 	if (mm->map_count > sysctl_max_map_count)
1906 		return -ENOMEM;
1907 
1908 	if (security_vm_enough_memory(len >> PAGE_SHIFT))
1909 		return -ENOMEM;
1910 
1911 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
1912 
1913 	/* Can we just expand an old private anonymous mapping? */
1914 	if (vma_merge(mm, prev, addr, addr + len, flags,
1915 					NULL, NULL, pgoff, NULL))
1916 		goto out;
1917 
1918 	/*
1919 	 * create a vma struct for an anonymous mapping
1920 	 */
1921 	vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
1922 	if (!vma) {
1923 		vm_unacct_memory(len >> PAGE_SHIFT);
1924 		return -ENOMEM;
1925 	}
1926 	memset(vma, 0, sizeof(*vma));
1927 
1928 	vma->vm_mm = mm;
1929 	vma->vm_start = addr;
1930 	vma->vm_end = addr + len;
1931 	vma->vm_pgoff = pgoff;
1932 	vma->vm_flags = flags;
1933 	vma->vm_page_prot = protection_map[flags & 0x0f];
1934 	vma_link(mm, vma, prev, rb_link, rb_parent);
1935 out:
1936 	mm->total_vm += len >> PAGE_SHIFT;
1937 	if (flags & VM_LOCKED) {
1938 		mm->locked_vm += len >> PAGE_SHIFT;
1939 		make_pages_present(addr, addr + len);
1940 	}
1941 	return addr;
1942 }
1943 
1944 EXPORT_SYMBOL(do_brk);
1945 
1946 /* Release all mmaps. */
1947 void exit_mmap(struct mm_struct *mm)
1948 {
1949 	struct mmu_gather *tlb;
1950 	struct vm_area_struct *vma = mm->mmap;
1951 	unsigned long nr_accounted = 0;
1952 	unsigned long end;
1953 
1954 	lru_add_drain();
1955 	flush_cache_mm(mm);
1956 	tlb = tlb_gather_mmu(mm, 1);
1957 	/* Don't update_hiwater_rss(mm) here, do_exit already did */
1958 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
1959 	end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
1960 	vm_unacct_memory(nr_accounted);
1961 	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
1962 	tlb_finish_mmu(tlb, 0, end);
1963 
1964 	/*
1965 	 * Walk the list again, actually closing and freeing it,
1966 	 * with preemption enabled, without holding any MM locks.
1967 	 */
1968 	while (vma)
1969 		vma = remove_vma(vma);
1970 
1971 	BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
1972 }
1973 
1974 /* Insert vm structure into process list sorted by address
1975  * and into the inode's i_mmap tree.  If vm_file is non-NULL
1976  * then i_mmap_lock is taken here.
1977  */
1978 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
1979 {
1980 	struct vm_area_struct * __vma, * prev;
1981 	struct rb_node ** rb_link, * rb_parent;
1982 
1983 	/*
1984 	 * The vm_pgoff of a purely anonymous vma should be irrelevant
1985 	 * until its first write fault, when page's anon_vma and index
1986 	 * are set.  But now set the vm_pgoff it will almost certainly
1987 	 * end up with (unless mremap moves it elsewhere before that
1988 	 * first wfault), so /proc/pid/maps tells a consistent story.
1989 	 *
1990 	 * By setting it to reflect the virtual start address of the
1991 	 * vma, merges and splits can happen in a seamless way, just
1992 	 * using the existing file pgoff checks and manipulations.
1993 	 * Similarly in do_mmap_pgoff and in do_brk.
1994 	 */
1995 	if (!vma->vm_file) {
1996 		BUG_ON(vma->anon_vma);
1997 		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
1998 	}
1999 	__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2000 	if (__vma && __vma->vm_start < vma->vm_end)
2001 		return -ENOMEM;
2002 	if ((vma->vm_flags & VM_ACCOUNT) &&
2003 	     security_vm_enough_memory(vma_pages(vma)))
2004 		return -ENOMEM;
2005 	vma_link(mm, vma, prev, rb_link, rb_parent);
2006 	return 0;
2007 }
2008 
2009 /*
2010  * Copy the vma structure to a new location in the same mm,
2011  * prior to moving page table entries, to effect an mremap move.
2012  */
2013 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2014 	unsigned long addr, unsigned long len, pgoff_t pgoff)
2015 {
2016 	struct vm_area_struct *vma = *vmap;
2017 	unsigned long vma_start = vma->vm_start;
2018 	struct mm_struct *mm = vma->vm_mm;
2019 	struct vm_area_struct *new_vma, *prev;
2020 	struct rb_node **rb_link, *rb_parent;
2021 	struct mempolicy *pol;
2022 
2023 	/*
2024 	 * If anonymous vma has not yet been faulted, update new pgoff
2025 	 * to match new location, to increase its chance of merging.
2026 	 */
2027 	if (!vma->vm_file && !vma->anon_vma)
2028 		pgoff = addr >> PAGE_SHIFT;
2029 
2030 	find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2031 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2032 			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2033 	if (new_vma) {
2034 		/*
2035 		 * Source vma may have been merged into new_vma
2036 		 */
2037 		if (vma_start >= new_vma->vm_start &&
2038 		    vma_start < new_vma->vm_end)
2039 			*vmap = new_vma;
2040 	} else {
2041 		new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
2042 		if (new_vma) {
2043 			*new_vma = *vma;
2044 			pol = mpol_copy(vma_policy(vma));
2045 			if (IS_ERR(pol)) {
2046 				kmem_cache_free(vm_area_cachep, new_vma);
2047 				return NULL;
2048 			}
2049 			vma_set_policy(new_vma, pol);
2050 			new_vma->vm_start = addr;
2051 			new_vma->vm_end = addr + len;
2052 			new_vma->vm_pgoff = pgoff;
2053 			if (new_vma->vm_file)
2054 				get_file(new_vma->vm_file);
2055 			if (new_vma->vm_ops && new_vma->vm_ops->open)
2056 				new_vma->vm_ops->open(new_vma);
2057 			vma_link(mm, new_vma, prev, rb_link, rb_parent);
2058 		}
2059 	}
2060 	return new_vma;
2061 }
2062 
2063 /*
2064  * Return true if the calling process may expand its vm space by the passed
2065  * number of pages
2066  */
2067 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2068 {
2069 	unsigned long cur = mm->total_vm;	/* pages */
2070 	unsigned long lim;
2071 
2072 	lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
2073 
2074 	if (cur + npages > lim)
2075 		return 0;
2076 	return 1;
2077 }
2078