xref: /linux/mm/mmap.c (revision 6c21a7fb492bf7e2c4985937082ce58ddeca84bd)
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 	error = arch_mmap_check(addr, len, flags);
935 	if (error)
936 		return error;
937 
938 	/* Careful about overflows.. */
939 	len = PAGE_ALIGN(len);
940 	if (!len || len > TASK_SIZE)
941 		return -ENOMEM;
942 
943 	/* offset overflow? */
944 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
945                return -EOVERFLOW;
946 
947 	/* Too many mappings? */
948 	if (mm->map_count > sysctl_max_map_count)
949 		return -ENOMEM;
950 
951 	if (flags & MAP_HUGETLB) {
952 		struct user_struct *user = NULL;
953 		if (file)
954 			return -EINVAL;
955 
956 		/*
957 		 * VM_NORESERVE is used because the reservations will be
958 		 * taken when vm_ops->mmap() is called
959 		 * A dummy user value is used because we are not locking
960 		 * memory so no accounting is necessary
961 		 */
962 		len = ALIGN(len, huge_page_size(&default_hstate));
963 		file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
964 						&user, HUGETLB_ANONHUGE_INODE);
965 		if (IS_ERR(file))
966 			return PTR_ERR(file);
967 	}
968 
969 	/* Obtain the address to map to. we verify (or select) it and ensure
970 	 * that it represents a valid section of the address space.
971 	 */
972 	addr = get_unmapped_area(file, addr, len, pgoff, flags);
973 	if (addr & ~PAGE_MASK)
974 		return addr;
975 
976 	/* Do simple checking here so the lower-level routines won't have
977 	 * to. we assume access permissions have been handled by the open
978 	 * of the memory object, so we don't do any here.
979 	 */
980 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
981 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
982 
983 	if (flags & MAP_LOCKED)
984 		if (!can_do_mlock())
985 			return -EPERM;
986 
987 	/* mlock MCL_FUTURE? */
988 	if (vm_flags & VM_LOCKED) {
989 		unsigned long locked, lock_limit;
990 		locked = len >> PAGE_SHIFT;
991 		locked += mm->locked_vm;
992 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
993 		lock_limit >>= PAGE_SHIFT;
994 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
995 			return -EAGAIN;
996 	}
997 
998 	inode = file ? file->f_path.dentry->d_inode : NULL;
999 
1000 	if (file) {
1001 		switch (flags & MAP_TYPE) {
1002 		case MAP_SHARED:
1003 			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1004 				return -EACCES;
1005 
1006 			/*
1007 			 * Make sure we don't allow writing to an append-only
1008 			 * file..
1009 			 */
1010 			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1011 				return -EACCES;
1012 
1013 			/*
1014 			 * Make sure there are no mandatory locks on the file.
1015 			 */
1016 			if (locks_verify_locked(inode))
1017 				return -EAGAIN;
1018 
1019 			vm_flags |= VM_SHARED | VM_MAYSHARE;
1020 			if (!(file->f_mode & FMODE_WRITE))
1021 				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1022 
1023 			/* fall through */
1024 		case MAP_PRIVATE:
1025 			if (!(file->f_mode & FMODE_READ))
1026 				return -EACCES;
1027 			if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1028 				if (vm_flags & VM_EXEC)
1029 					return -EPERM;
1030 				vm_flags &= ~VM_MAYEXEC;
1031 			}
1032 
1033 			if (!file->f_op || !file->f_op->mmap)
1034 				return -ENODEV;
1035 			break;
1036 
1037 		default:
1038 			return -EINVAL;
1039 		}
1040 	} else {
1041 		switch (flags & MAP_TYPE) {
1042 		case MAP_SHARED:
1043 			/*
1044 			 * Ignore pgoff.
1045 			 */
1046 			pgoff = 0;
1047 			vm_flags |= VM_SHARED | VM_MAYSHARE;
1048 			break;
1049 		case MAP_PRIVATE:
1050 			/*
1051 			 * Set pgoff according to addr for anon_vma.
1052 			 */
1053 			pgoff = addr >> PAGE_SHIFT;
1054 			break;
1055 		default:
1056 			return -EINVAL;
1057 		}
1058 	}
1059 
1060 	error = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1061 	if (error)
1062 		return error;
1063 
1064 	return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1065 }
1066 EXPORT_SYMBOL(do_mmap_pgoff);
1067 
1068 /*
1069  * Some shared mappigns will want the pages marked read-only
1070  * to track write events. If so, we'll downgrade vm_page_prot
1071  * to the private version (using protection_map[] without the
1072  * VM_SHARED bit).
1073  */
1074 int vma_wants_writenotify(struct vm_area_struct *vma)
1075 {
1076 	unsigned int vm_flags = vma->vm_flags;
1077 
1078 	/* If it was private or non-writable, the write bit is already clear */
1079 	if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1080 		return 0;
1081 
1082 	/* The backer wishes to know when pages are first written to? */
1083 	if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1084 		return 1;
1085 
1086 	/* The open routine did something to the protections already? */
1087 	if (pgprot_val(vma->vm_page_prot) !=
1088 	    pgprot_val(vm_get_page_prot(vm_flags)))
1089 		return 0;
1090 
1091 	/* Specialty mapping? */
1092 	if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1093 		return 0;
1094 
1095 	/* Can the mapping track the dirty pages? */
1096 	return vma->vm_file && vma->vm_file->f_mapping &&
1097 		mapping_cap_account_dirty(vma->vm_file->f_mapping);
1098 }
1099 
1100 /*
1101  * We account for memory if it's a private writeable mapping,
1102  * not hugepages and VM_NORESERVE wasn't set.
1103  */
1104 static inline int accountable_mapping(struct file *file, unsigned int vm_flags)
1105 {
1106 	/*
1107 	 * hugetlb has its own accounting separate from the core VM
1108 	 * VM_HUGETLB may not be set yet so we cannot check for that flag.
1109 	 */
1110 	if (file && is_file_hugepages(file))
1111 		return 0;
1112 
1113 	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1114 }
1115 
1116 unsigned long mmap_region(struct file *file, unsigned long addr,
1117 			  unsigned long len, unsigned long flags,
1118 			  unsigned int vm_flags, unsigned long pgoff)
1119 {
1120 	struct mm_struct *mm = current->mm;
1121 	struct vm_area_struct *vma, *prev;
1122 	int correct_wcount = 0;
1123 	int error;
1124 	struct rb_node **rb_link, *rb_parent;
1125 	unsigned long charged = 0;
1126 	struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
1127 
1128 	/* Clear old maps */
1129 	error = -ENOMEM;
1130 munmap_back:
1131 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1132 	if (vma && vma->vm_start < addr + len) {
1133 		if (do_munmap(mm, addr, len))
1134 			return -ENOMEM;
1135 		goto munmap_back;
1136 	}
1137 
1138 	/* Check against address space limit. */
1139 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1140 		return -ENOMEM;
1141 
1142 	/*
1143 	 * Set 'VM_NORESERVE' if we should not account for the
1144 	 * memory use of this mapping.
1145 	 */
1146 	if ((flags & MAP_NORESERVE)) {
1147 		/* We honor MAP_NORESERVE if allowed to overcommit */
1148 		if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1149 			vm_flags |= VM_NORESERVE;
1150 
1151 		/* hugetlb applies strict overcommit unless MAP_NORESERVE */
1152 		if (file && is_file_hugepages(file))
1153 			vm_flags |= VM_NORESERVE;
1154 	}
1155 
1156 	/*
1157 	 * Private writable mapping: check memory availability
1158 	 */
1159 	if (accountable_mapping(file, vm_flags)) {
1160 		charged = len >> PAGE_SHIFT;
1161 		if (security_vm_enough_memory(charged))
1162 			return -ENOMEM;
1163 		vm_flags |= VM_ACCOUNT;
1164 	}
1165 
1166 	/*
1167 	 * Can we just expand an old mapping?
1168 	 */
1169 	vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1170 	if (vma)
1171 		goto out;
1172 
1173 	/*
1174 	 * Determine the object being mapped and call the appropriate
1175 	 * specific mapper. the address has already been validated, but
1176 	 * not unmapped, but the maps are removed from the list.
1177 	 */
1178 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1179 	if (!vma) {
1180 		error = -ENOMEM;
1181 		goto unacct_error;
1182 	}
1183 
1184 	vma->vm_mm = mm;
1185 	vma->vm_start = addr;
1186 	vma->vm_end = addr + len;
1187 	vma->vm_flags = vm_flags;
1188 	vma->vm_page_prot = vm_get_page_prot(vm_flags);
1189 	vma->vm_pgoff = pgoff;
1190 
1191 	if (file) {
1192 		error = -EINVAL;
1193 		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1194 			goto free_vma;
1195 		if (vm_flags & VM_DENYWRITE) {
1196 			error = deny_write_access(file);
1197 			if (error)
1198 				goto free_vma;
1199 			correct_wcount = 1;
1200 		}
1201 		vma->vm_file = file;
1202 		get_file(file);
1203 		error = file->f_op->mmap(file, vma);
1204 		if (error)
1205 			goto unmap_and_free_vma;
1206 		if (vm_flags & VM_EXECUTABLE)
1207 			added_exe_file_vma(mm);
1208 
1209 		/* Can addr have changed??
1210 		 *
1211 		 * Answer: Yes, several device drivers can do it in their
1212 		 *         f_op->mmap method. -DaveM
1213 		 */
1214 		addr = vma->vm_start;
1215 		pgoff = vma->vm_pgoff;
1216 		vm_flags = vma->vm_flags;
1217 	} else if (vm_flags & VM_SHARED) {
1218 		error = shmem_zero_setup(vma);
1219 		if (error)
1220 			goto free_vma;
1221 	}
1222 
1223 	if (vma_wants_writenotify(vma))
1224 		vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1225 
1226 	vma_link(mm, vma, prev, rb_link, rb_parent);
1227 	file = vma->vm_file;
1228 
1229 	/* Once vma denies write, undo our temporary denial count */
1230 	if (correct_wcount)
1231 		atomic_inc(&inode->i_writecount);
1232 out:
1233 	perf_event_mmap(vma);
1234 
1235 	mm->total_vm += len >> PAGE_SHIFT;
1236 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1237 	if (vm_flags & VM_LOCKED) {
1238 		/*
1239 		 * makes pages present; downgrades, drops, reacquires mmap_sem
1240 		 */
1241 		long nr_pages = mlock_vma_pages_range(vma, addr, addr + len);
1242 		if (nr_pages < 0)
1243 			return nr_pages;	/* vma gone! */
1244 		mm->locked_vm += (len >> PAGE_SHIFT) - nr_pages;
1245 	} else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1246 		make_pages_present(addr, addr + len);
1247 	return addr;
1248 
1249 unmap_and_free_vma:
1250 	if (correct_wcount)
1251 		atomic_inc(&inode->i_writecount);
1252 	vma->vm_file = NULL;
1253 	fput(file);
1254 
1255 	/* Undo any partial mapping done by a device driver. */
1256 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1257 	charged = 0;
1258 free_vma:
1259 	kmem_cache_free(vm_area_cachep, vma);
1260 unacct_error:
1261 	if (charged)
1262 		vm_unacct_memory(charged);
1263 	return error;
1264 }
1265 
1266 /* Get an address range which is currently unmapped.
1267  * For shmat() with addr=0.
1268  *
1269  * Ugly calling convention alert:
1270  * Return value with the low bits set means error value,
1271  * ie
1272  *	if (ret & ~PAGE_MASK)
1273  *		error = ret;
1274  *
1275  * This function "knows" that -ENOMEM has the bits set.
1276  */
1277 #ifndef HAVE_ARCH_UNMAPPED_AREA
1278 unsigned long
1279 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1280 		unsigned long len, unsigned long pgoff, unsigned long flags)
1281 {
1282 	struct mm_struct *mm = current->mm;
1283 	struct vm_area_struct *vma;
1284 	unsigned long start_addr;
1285 
1286 	if (len > TASK_SIZE)
1287 		return -ENOMEM;
1288 
1289 	if (flags & MAP_FIXED)
1290 		return addr;
1291 
1292 	if (addr) {
1293 		addr = PAGE_ALIGN(addr);
1294 		vma = find_vma(mm, addr);
1295 		if (TASK_SIZE - len >= addr &&
1296 		    (!vma || addr + len <= vma->vm_start))
1297 			return addr;
1298 	}
1299 	if (len > mm->cached_hole_size) {
1300 	        start_addr = addr = mm->free_area_cache;
1301 	} else {
1302 	        start_addr = addr = TASK_UNMAPPED_BASE;
1303 	        mm->cached_hole_size = 0;
1304 	}
1305 
1306 full_search:
1307 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1308 		/* At this point:  (!vma || addr < vma->vm_end). */
1309 		if (TASK_SIZE - len < addr) {
1310 			/*
1311 			 * Start a new search - just in case we missed
1312 			 * some holes.
1313 			 */
1314 			if (start_addr != TASK_UNMAPPED_BASE) {
1315 				addr = TASK_UNMAPPED_BASE;
1316 			        start_addr = addr;
1317 				mm->cached_hole_size = 0;
1318 				goto full_search;
1319 			}
1320 			return -ENOMEM;
1321 		}
1322 		if (!vma || addr + len <= vma->vm_start) {
1323 			/*
1324 			 * Remember the place where we stopped the search:
1325 			 */
1326 			mm->free_area_cache = addr + len;
1327 			return addr;
1328 		}
1329 		if (addr + mm->cached_hole_size < vma->vm_start)
1330 		        mm->cached_hole_size = vma->vm_start - addr;
1331 		addr = vma->vm_end;
1332 	}
1333 }
1334 #endif
1335 
1336 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1337 {
1338 	/*
1339 	 * Is this a new hole at the lowest possible address?
1340 	 */
1341 	if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1342 		mm->free_area_cache = addr;
1343 		mm->cached_hole_size = ~0UL;
1344 	}
1345 }
1346 
1347 /*
1348  * This mmap-allocator allocates new areas top-down from below the
1349  * stack's low limit (the base):
1350  */
1351 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1352 unsigned long
1353 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1354 			  const unsigned long len, const unsigned long pgoff,
1355 			  const unsigned long flags)
1356 {
1357 	struct vm_area_struct *vma;
1358 	struct mm_struct *mm = current->mm;
1359 	unsigned long addr = addr0;
1360 
1361 	/* requested length too big for entire address space */
1362 	if (len > TASK_SIZE)
1363 		return -ENOMEM;
1364 
1365 	if (flags & MAP_FIXED)
1366 		return addr;
1367 
1368 	/* requesting a specific address */
1369 	if (addr) {
1370 		addr = PAGE_ALIGN(addr);
1371 		vma = find_vma(mm, addr);
1372 		if (TASK_SIZE - len >= addr &&
1373 				(!vma || addr + len <= vma->vm_start))
1374 			return addr;
1375 	}
1376 
1377 	/* check if free_area_cache is useful for us */
1378 	if (len <= mm->cached_hole_size) {
1379  	        mm->cached_hole_size = 0;
1380  		mm->free_area_cache = mm->mmap_base;
1381  	}
1382 
1383 	/* either no address requested or can't fit in requested address hole */
1384 	addr = mm->free_area_cache;
1385 
1386 	/* make sure it can fit in the remaining address space */
1387 	if (addr > len) {
1388 		vma = find_vma(mm, addr-len);
1389 		if (!vma || addr <= vma->vm_start)
1390 			/* remember the address as a hint for next time */
1391 			return (mm->free_area_cache = addr-len);
1392 	}
1393 
1394 	if (mm->mmap_base < len)
1395 		goto bottomup;
1396 
1397 	addr = mm->mmap_base-len;
1398 
1399 	do {
1400 		/*
1401 		 * Lookup failure means no vma is above this address,
1402 		 * else if new region fits below vma->vm_start,
1403 		 * return with success:
1404 		 */
1405 		vma = find_vma(mm, addr);
1406 		if (!vma || addr+len <= vma->vm_start)
1407 			/* remember the address as a hint for next time */
1408 			return (mm->free_area_cache = addr);
1409 
1410  		/* remember the largest hole we saw so far */
1411  		if (addr + mm->cached_hole_size < vma->vm_start)
1412  		        mm->cached_hole_size = vma->vm_start - addr;
1413 
1414 		/* try just below the current vma->vm_start */
1415 		addr = vma->vm_start-len;
1416 	} while (len < vma->vm_start);
1417 
1418 bottomup:
1419 	/*
1420 	 * A failed mmap() very likely causes application failure,
1421 	 * so fall back to the bottom-up function here. This scenario
1422 	 * can happen with large stack limits and large mmap()
1423 	 * allocations.
1424 	 */
1425 	mm->cached_hole_size = ~0UL;
1426   	mm->free_area_cache = TASK_UNMAPPED_BASE;
1427 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1428 	/*
1429 	 * Restore the topdown base:
1430 	 */
1431 	mm->free_area_cache = mm->mmap_base;
1432 	mm->cached_hole_size = ~0UL;
1433 
1434 	return addr;
1435 }
1436 #endif
1437 
1438 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1439 {
1440 	/*
1441 	 * Is this a new hole at the highest possible address?
1442 	 */
1443 	if (addr > mm->free_area_cache)
1444 		mm->free_area_cache = addr;
1445 
1446 	/* dont allow allocations above current base */
1447 	if (mm->free_area_cache > mm->mmap_base)
1448 		mm->free_area_cache = mm->mmap_base;
1449 }
1450 
1451 unsigned long
1452 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1453 		unsigned long pgoff, unsigned long flags)
1454 {
1455 	unsigned long (*get_area)(struct file *, unsigned long,
1456 				  unsigned long, unsigned long, unsigned long);
1457 
1458 	get_area = current->mm->get_unmapped_area;
1459 	if (file && file->f_op && file->f_op->get_unmapped_area)
1460 		get_area = file->f_op->get_unmapped_area;
1461 	addr = get_area(file, addr, len, pgoff, flags);
1462 	if (IS_ERR_VALUE(addr))
1463 		return addr;
1464 
1465 	if (addr > TASK_SIZE - len)
1466 		return -ENOMEM;
1467 	if (addr & ~PAGE_MASK)
1468 		return -EINVAL;
1469 
1470 	return arch_rebalance_pgtables(addr, len);
1471 }
1472 
1473 EXPORT_SYMBOL(get_unmapped_area);
1474 
1475 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1476 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1477 {
1478 	struct vm_area_struct *vma = NULL;
1479 
1480 	if (mm) {
1481 		/* Check the cache first. */
1482 		/* (Cache hit rate is typically around 35%.) */
1483 		vma = mm->mmap_cache;
1484 		if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1485 			struct rb_node * rb_node;
1486 
1487 			rb_node = mm->mm_rb.rb_node;
1488 			vma = NULL;
1489 
1490 			while (rb_node) {
1491 				struct vm_area_struct * vma_tmp;
1492 
1493 				vma_tmp = rb_entry(rb_node,
1494 						struct vm_area_struct, vm_rb);
1495 
1496 				if (vma_tmp->vm_end > addr) {
1497 					vma = vma_tmp;
1498 					if (vma_tmp->vm_start <= addr)
1499 						break;
1500 					rb_node = rb_node->rb_left;
1501 				} else
1502 					rb_node = rb_node->rb_right;
1503 			}
1504 			if (vma)
1505 				mm->mmap_cache = vma;
1506 		}
1507 	}
1508 	return vma;
1509 }
1510 
1511 EXPORT_SYMBOL(find_vma);
1512 
1513 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1514 struct vm_area_struct *
1515 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1516 			struct vm_area_struct **pprev)
1517 {
1518 	struct vm_area_struct *vma = NULL, *prev = NULL;
1519 	struct rb_node *rb_node;
1520 	if (!mm)
1521 		goto out;
1522 
1523 	/* Guard against addr being lower than the first VMA */
1524 	vma = mm->mmap;
1525 
1526 	/* Go through the RB tree quickly. */
1527 	rb_node = mm->mm_rb.rb_node;
1528 
1529 	while (rb_node) {
1530 		struct vm_area_struct *vma_tmp;
1531 		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1532 
1533 		if (addr < vma_tmp->vm_end) {
1534 			rb_node = rb_node->rb_left;
1535 		} else {
1536 			prev = vma_tmp;
1537 			if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1538 				break;
1539 			rb_node = rb_node->rb_right;
1540 		}
1541 	}
1542 
1543 out:
1544 	*pprev = prev;
1545 	return prev ? prev->vm_next : vma;
1546 }
1547 
1548 /*
1549  * Verify that the stack growth is acceptable and
1550  * update accounting. This is shared with both the
1551  * grow-up and grow-down cases.
1552  */
1553 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1554 {
1555 	struct mm_struct *mm = vma->vm_mm;
1556 	struct rlimit *rlim = current->signal->rlim;
1557 	unsigned long new_start;
1558 
1559 	/* address space limit tests */
1560 	if (!may_expand_vm(mm, grow))
1561 		return -ENOMEM;
1562 
1563 	/* Stack limit test */
1564 	if (size > rlim[RLIMIT_STACK].rlim_cur)
1565 		return -ENOMEM;
1566 
1567 	/* mlock limit tests */
1568 	if (vma->vm_flags & VM_LOCKED) {
1569 		unsigned long locked;
1570 		unsigned long limit;
1571 		locked = mm->locked_vm + grow;
1572 		limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
1573 		if (locked > limit && !capable(CAP_IPC_LOCK))
1574 			return -ENOMEM;
1575 	}
1576 
1577 	/* Check to ensure the stack will not grow into a hugetlb-only region */
1578 	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1579 			vma->vm_end - size;
1580 	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1581 		return -EFAULT;
1582 
1583 	/*
1584 	 * Overcommit..  This must be the final test, as it will
1585 	 * update security statistics.
1586 	 */
1587 	if (security_vm_enough_memory_mm(mm, grow))
1588 		return -ENOMEM;
1589 
1590 	/* Ok, everything looks good - let it rip */
1591 	mm->total_vm += grow;
1592 	if (vma->vm_flags & VM_LOCKED)
1593 		mm->locked_vm += grow;
1594 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1595 	return 0;
1596 }
1597 
1598 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1599 /*
1600  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1601  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1602  */
1603 #ifndef CONFIG_IA64
1604 static
1605 #endif
1606 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1607 {
1608 	int error;
1609 
1610 	if (!(vma->vm_flags & VM_GROWSUP))
1611 		return -EFAULT;
1612 
1613 	/*
1614 	 * We must make sure the anon_vma is allocated
1615 	 * so that the anon_vma locking is not a noop.
1616 	 */
1617 	if (unlikely(anon_vma_prepare(vma)))
1618 		return -ENOMEM;
1619 	anon_vma_lock(vma);
1620 
1621 	/*
1622 	 * vma->vm_start/vm_end cannot change under us because the caller
1623 	 * is required to hold the mmap_sem in read mode.  We need the
1624 	 * anon_vma lock to serialize against concurrent expand_stacks.
1625 	 * Also guard against wrapping around to address 0.
1626 	 */
1627 	if (address < PAGE_ALIGN(address+4))
1628 		address = PAGE_ALIGN(address+4);
1629 	else {
1630 		anon_vma_unlock(vma);
1631 		return -ENOMEM;
1632 	}
1633 	error = 0;
1634 
1635 	/* Somebody else might have raced and expanded it already */
1636 	if (address > vma->vm_end) {
1637 		unsigned long size, grow;
1638 
1639 		size = address - vma->vm_start;
1640 		grow = (address - vma->vm_end) >> PAGE_SHIFT;
1641 
1642 		error = acct_stack_growth(vma, size, grow);
1643 		if (!error)
1644 			vma->vm_end = address;
1645 	}
1646 	anon_vma_unlock(vma);
1647 	return error;
1648 }
1649 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1650 
1651 /*
1652  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1653  */
1654 static int expand_downwards(struct vm_area_struct *vma,
1655 				   unsigned long address)
1656 {
1657 	int error;
1658 
1659 	/*
1660 	 * We must make sure the anon_vma is allocated
1661 	 * so that the anon_vma locking is not a noop.
1662 	 */
1663 	if (unlikely(anon_vma_prepare(vma)))
1664 		return -ENOMEM;
1665 
1666 	address &= PAGE_MASK;
1667 	error = security_file_mmap(NULL, 0, 0, 0, address, 1);
1668 	if (error)
1669 		return error;
1670 
1671 	anon_vma_lock(vma);
1672 
1673 	/*
1674 	 * vma->vm_start/vm_end cannot change under us because the caller
1675 	 * is required to hold the mmap_sem in read mode.  We need the
1676 	 * anon_vma lock to serialize against concurrent expand_stacks.
1677 	 */
1678 
1679 	/* Somebody else might have raced and expanded it already */
1680 	if (address < vma->vm_start) {
1681 		unsigned long size, grow;
1682 
1683 		size = vma->vm_end - address;
1684 		grow = (vma->vm_start - address) >> PAGE_SHIFT;
1685 
1686 		error = acct_stack_growth(vma, size, grow);
1687 		if (!error) {
1688 			vma->vm_start = address;
1689 			vma->vm_pgoff -= grow;
1690 		}
1691 	}
1692 	anon_vma_unlock(vma);
1693 	return error;
1694 }
1695 
1696 int expand_stack_downwards(struct vm_area_struct *vma, unsigned long address)
1697 {
1698 	return expand_downwards(vma, address);
1699 }
1700 
1701 #ifdef CONFIG_STACK_GROWSUP
1702 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1703 {
1704 	return expand_upwards(vma, address);
1705 }
1706 
1707 struct vm_area_struct *
1708 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1709 {
1710 	struct vm_area_struct *vma, *prev;
1711 
1712 	addr &= PAGE_MASK;
1713 	vma = find_vma_prev(mm, addr, &prev);
1714 	if (vma && (vma->vm_start <= addr))
1715 		return vma;
1716 	if (!prev || expand_stack(prev, addr))
1717 		return NULL;
1718 	if (prev->vm_flags & VM_LOCKED) {
1719 		if (mlock_vma_pages_range(prev, addr, prev->vm_end) < 0)
1720 			return NULL;	/* vma gone! */
1721 	}
1722 	return prev;
1723 }
1724 #else
1725 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1726 {
1727 	return expand_downwards(vma, address);
1728 }
1729 
1730 struct vm_area_struct *
1731 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1732 {
1733 	struct vm_area_struct * vma;
1734 	unsigned long start;
1735 
1736 	addr &= PAGE_MASK;
1737 	vma = find_vma(mm,addr);
1738 	if (!vma)
1739 		return NULL;
1740 	if (vma->vm_start <= addr)
1741 		return vma;
1742 	if (!(vma->vm_flags & VM_GROWSDOWN))
1743 		return NULL;
1744 	start = vma->vm_start;
1745 	if (expand_stack(vma, addr))
1746 		return NULL;
1747 	if (vma->vm_flags & VM_LOCKED) {
1748 		if (mlock_vma_pages_range(vma, addr, start) < 0)
1749 			return NULL;	/* vma gone! */
1750 	}
1751 	return vma;
1752 }
1753 #endif
1754 
1755 /*
1756  * Ok - we have the memory areas we should free on the vma list,
1757  * so release them, and do the vma updates.
1758  *
1759  * Called with the mm semaphore held.
1760  */
1761 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1762 {
1763 	/* Update high watermark before we lower total_vm */
1764 	update_hiwater_vm(mm);
1765 	do {
1766 		long nrpages = vma_pages(vma);
1767 
1768 		mm->total_vm -= nrpages;
1769 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1770 		vma = remove_vma(vma);
1771 	} while (vma);
1772 	validate_mm(mm);
1773 }
1774 
1775 /*
1776  * Get rid of page table information in the indicated region.
1777  *
1778  * Called with the mm semaphore held.
1779  */
1780 static void unmap_region(struct mm_struct *mm,
1781 		struct vm_area_struct *vma, struct vm_area_struct *prev,
1782 		unsigned long start, unsigned long end)
1783 {
1784 	struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1785 	struct mmu_gather *tlb;
1786 	unsigned long nr_accounted = 0;
1787 
1788 	lru_add_drain();
1789 	tlb = tlb_gather_mmu(mm, 0);
1790 	update_hiwater_rss(mm);
1791 	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1792 	vm_unacct_memory(nr_accounted);
1793 	free_pgtables(tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
1794 				 next? next->vm_start: 0);
1795 	tlb_finish_mmu(tlb, start, end);
1796 }
1797 
1798 /*
1799  * Create a list of vma's touched by the unmap, removing them from the mm's
1800  * vma list as we go..
1801  */
1802 static void
1803 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1804 	struct vm_area_struct *prev, unsigned long end)
1805 {
1806 	struct vm_area_struct **insertion_point;
1807 	struct vm_area_struct *tail_vma = NULL;
1808 	unsigned long addr;
1809 
1810 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1811 	do {
1812 		rb_erase(&vma->vm_rb, &mm->mm_rb);
1813 		mm->map_count--;
1814 		tail_vma = vma;
1815 		vma = vma->vm_next;
1816 	} while (vma && vma->vm_start < end);
1817 	*insertion_point = vma;
1818 	tail_vma->vm_next = NULL;
1819 	if (mm->unmap_area == arch_unmap_area)
1820 		addr = prev ? prev->vm_end : mm->mmap_base;
1821 	else
1822 		addr = vma ?  vma->vm_start : mm->mmap_base;
1823 	mm->unmap_area(mm, addr);
1824 	mm->mmap_cache = NULL;		/* Kill the cache. */
1825 }
1826 
1827 /*
1828  * Split a vma into two pieces at address 'addr', a new vma is allocated
1829  * either for the first part or the tail.
1830  */
1831 int split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1832 	      unsigned long addr, int new_below)
1833 {
1834 	struct mempolicy *pol;
1835 	struct vm_area_struct *new;
1836 
1837 	if (is_vm_hugetlb_page(vma) && (addr &
1838 					~(huge_page_mask(hstate_vma(vma)))))
1839 		return -EINVAL;
1840 
1841 	if (mm->map_count >= sysctl_max_map_count)
1842 		return -ENOMEM;
1843 
1844 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1845 	if (!new)
1846 		return -ENOMEM;
1847 
1848 	/* most fields are the same, copy all, and then fixup */
1849 	*new = *vma;
1850 
1851 	if (new_below)
1852 		new->vm_end = addr;
1853 	else {
1854 		new->vm_start = addr;
1855 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1856 	}
1857 
1858 	pol = mpol_dup(vma_policy(vma));
1859 	if (IS_ERR(pol)) {
1860 		kmem_cache_free(vm_area_cachep, new);
1861 		return PTR_ERR(pol);
1862 	}
1863 	vma_set_policy(new, pol);
1864 
1865 	if (new->vm_file) {
1866 		get_file(new->vm_file);
1867 		if (vma->vm_flags & VM_EXECUTABLE)
1868 			added_exe_file_vma(mm);
1869 	}
1870 
1871 	if (new->vm_ops && new->vm_ops->open)
1872 		new->vm_ops->open(new);
1873 
1874 	if (new_below)
1875 		vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1876 			((addr - new->vm_start) >> PAGE_SHIFT), new);
1877 	else
1878 		vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1879 
1880 	return 0;
1881 }
1882 
1883 /* Munmap is split into 2 main parts -- this part which finds
1884  * what needs doing, and the areas themselves, which do the
1885  * work.  This now handles partial unmappings.
1886  * Jeremy Fitzhardinge <jeremy@goop.org>
1887  */
1888 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1889 {
1890 	unsigned long end;
1891 	struct vm_area_struct *vma, *prev, *last;
1892 
1893 	if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
1894 		return -EINVAL;
1895 
1896 	if ((len = PAGE_ALIGN(len)) == 0)
1897 		return -EINVAL;
1898 
1899 	/* Find the first overlapping VMA */
1900 	vma = find_vma_prev(mm, start, &prev);
1901 	if (!vma)
1902 		return 0;
1903 	/* we have  start < vma->vm_end  */
1904 
1905 	/* if it doesn't overlap, we have nothing.. */
1906 	end = start + len;
1907 	if (vma->vm_start >= end)
1908 		return 0;
1909 
1910 	/*
1911 	 * If we need to split any vma, do it now to save pain later.
1912 	 *
1913 	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
1914 	 * unmapped vm_area_struct will remain in use: so lower split_vma
1915 	 * places tmp vma above, and higher split_vma places tmp vma below.
1916 	 */
1917 	if (start > vma->vm_start) {
1918 		int error = split_vma(mm, vma, start, 0);
1919 		if (error)
1920 			return error;
1921 		prev = vma;
1922 	}
1923 
1924 	/* Does it split the last one? */
1925 	last = find_vma(mm, end);
1926 	if (last && end > last->vm_start) {
1927 		int error = split_vma(mm, last, end, 1);
1928 		if (error)
1929 			return error;
1930 	}
1931 	vma = prev? prev->vm_next: mm->mmap;
1932 
1933 	/*
1934 	 * unlock any mlock()ed ranges before detaching vmas
1935 	 */
1936 	if (mm->locked_vm) {
1937 		struct vm_area_struct *tmp = vma;
1938 		while (tmp && tmp->vm_start < end) {
1939 			if (tmp->vm_flags & VM_LOCKED) {
1940 				mm->locked_vm -= vma_pages(tmp);
1941 				munlock_vma_pages_all(tmp);
1942 			}
1943 			tmp = tmp->vm_next;
1944 		}
1945 	}
1946 
1947 	/*
1948 	 * Remove the vma's, and unmap the actual pages
1949 	 */
1950 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
1951 	unmap_region(mm, vma, prev, start, end);
1952 
1953 	/* Fix up all other VM information */
1954 	remove_vma_list(mm, vma);
1955 
1956 	return 0;
1957 }
1958 
1959 EXPORT_SYMBOL(do_munmap);
1960 
1961 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1962 {
1963 	int ret;
1964 	struct mm_struct *mm = current->mm;
1965 
1966 	profile_munmap(addr);
1967 
1968 	down_write(&mm->mmap_sem);
1969 	ret = do_munmap(mm, addr, len);
1970 	up_write(&mm->mmap_sem);
1971 	return ret;
1972 }
1973 
1974 static inline void verify_mm_writelocked(struct mm_struct *mm)
1975 {
1976 #ifdef CONFIG_DEBUG_VM
1977 	if (unlikely(down_read_trylock(&mm->mmap_sem))) {
1978 		WARN_ON(1);
1979 		up_read(&mm->mmap_sem);
1980 	}
1981 #endif
1982 }
1983 
1984 /*
1985  *  this is really a simplified "do_mmap".  it only handles
1986  *  anonymous maps.  eventually we may be able to do some
1987  *  brk-specific accounting here.
1988  */
1989 unsigned long do_brk(unsigned long addr, unsigned long len)
1990 {
1991 	struct mm_struct * mm = current->mm;
1992 	struct vm_area_struct * vma, * prev;
1993 	unsigned long flags;
1994 	struct rb_node ** rb_link, * rb_parent;
1995 	pgoff_t pgoff = addr >> PAGE_SHIFT;
1996 	int error;
1997 
1998 	len = PAGE_ALIGN(len);
1999 	if (!len)
2000 		return addr;
2001 
2002 	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
2003 		return -EINVAL;
2004 
2005 	if (is_hugepage_only_range(mm, addr, len))
2006 		return -EINVAL;
2007 
2008 	error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
2009 	if (error)
2010 		return error;
2011 
2012 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2013 
2014 	error = arch_mmap_check(addr, len, flags);
2015 	if (error)
2016 		return error;
2017 
2018 	/*
2019 	 * mlock MCL_FUTURE?
2020 	 */
2021 	if (mm->def_flags & VM_LOCKED) {
2022 		unsigned long locked, lock_limit;
2023 		locked = len >> PAGE_SHIFT;
2024 		locked += mm->locked_vm;
2025 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
2026 		lock_limit >>= PAGE_SHIFT;
2027 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2028 			return -EAGAIN;
2029 	}
2030 
2031 	/*
2032 	 * mm->mmap_sem is required to protect against another thread
2033 	 * changing the mappings in case we sleep.
2034 	 */
2035 	verify_mm_writelocked(mm);
2036 
2037 	/*
2038 	 * Clear old maps.  this also does some error checking for us
2039 	 */
2040  munmap_back:
2041 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2042 	if (vma && vma->vm_start < addr + len) {
2043 		if (do_munmap(mm, addr, len))
2044 			return -ENOMEM;
2045 		goto munmap_back;
2046 	}
2047 
2048 	/* Check against address space limits *after* clearing old maps... */
2049 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2050 		return -ENOMEM;
2051 
2052 	if (mm->map_count > sysctl_max_map_count)
2053 		return -ENOMEM;
2054 
2055 	if (security_vm_enough_memory(len >> PAGE_SHIFT))
2056 		return -ENOMEM;
2057 
2058 	/* Can we just expand an old private anonymous mapping? */
2059 	vma = vma_merge(mm, prev, addr, addr + len, flags,
2060 					NULL, NULL, pgoff, NULL);
2061 	if (vma)
2062 		goto out;
2063 
2064 	/*
2065 	 * create a vma struct for an anonymous mapping
2066 	 */
2067 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2068 	if (!vma) {
2069 		vm_unacct_memory(len >> PAGE_SHIFT);
2070 		return -ENOMEM;
2071 	}
2072 
2073 	vma->vm_mm = mm;
2074 	vma->vm_start = addr;
2075 	vma->vm_end = addr + len;
2076 	vma->vm_pgoff = pgoff;
2077 	vma->vm_flags = flags;
2078 	vma->vm_page_prot = vm_get_page_prot(flags);
2079 	vma_link(mm, vma, prev, rb_link, rb_parent);
2080 out:
2081 	mm->total_vm += len >> PAGE_SHIFT;
2082 	if (flags & VM_LOCKED) {
2083 		if (!mlock_vma_pages_range(vma, addr, addr + len))
2084 			mm->locked_vm += (len >> PAGE_SHIFT);
2085 	}
2086 	return addr;
2087 }
2088 
2089 EXPORT_SYMBOL(do_brk);
2090 
2091 /* Release all mmaps. */
2092 void exit_mmap(struct mm_struct *mm)
2093 {
2094 	struct mmu_gather *tlb;
2095 	struct vm_area_struct *vma;
2096 	unsigned long nr_accounted = 0;
2097 	unsigned long end;
2098 
2099 	/* mm's last user has gone, and its about to be pulled down */
2100 	mmu_notifier_release(mm);
2101 
2102 	if (mm->locked_vm) {
2103 		vma = mm->mmap;
2104 		while (vma) {
2105 			if (vma->vm_flags & VM_LOCKED)
2106 				munlock_vma_pages_all(vma);
2107 			vma = vma->vm_next;
2108 		}
2109 	}
2110 
2111 	arch_exit_mmap(mm);
2112 
2113 	vma = mm->mmap;
2114 	if (!vma)	/* Can happen if dup_mmap() received an OOM */
2115 		return;
2116 
2117 	lru_add_drain();
2118 	flush_cache_mm(mm);
2119 	tlb = tlb_gather_mmu(mm, 1);
2120 	/* update_hiwater_rss(mm) here? but nobody should be looking */
2121 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
2122 	end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
2123 	vm_unacct_memory(nr_accounted);
2124 
2125 	free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0);
2126 	tlb_finish_mmu(tlb, 0, end);
2127 
2128 	/*
2129 	 * Walk the list again, actually closing and freeing it,
2130 	 * with preemption enabled, without holding any MM locks.
2131 	 */
2132 	while (vma)
2133 		vma = remove_vma(vma);
2134 
2135 	BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2136 }
2137 
2138 /* Insert vm structure into process list sorted by address
2139  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2140  * then i_mmap_lock is taken here.
2141  */
2142 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2143 {
2144 	struct vm_area_struct * __vma, * prev;
2145 	struct rb_node ** rb_link, * rb_parent;
2146 
2147 	/*
2148 	 * The vm_pgoff of a purely anonymous vma should be irrelevant
2149 	 * until its first write fault, when page's anon_vma and index
2150 	 * are set.  But now set the vm_pgoff it will almost certainly
2151 	 * end up with (unless mremap moves it elsewhere before that
2152 	 * first wfault), so /proc/pid/maps tells a consistent story.
2153 	 *
2154 	 * By setting it to reflect the virtual start address of the
2155 	 * vma, merges and splits can happen in a seamless way, just
2156 	 * using the existing file pgoff checks and manipulations.
2157 	 * Similarly in do_mmap_pgoff and in do_brk.
2158 	 */
2159 	if (!vma->vm_file) {
2160 		BUG_ON(vma->anon_vma);
2161 		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2162 	}
2163 	__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2164 	if (__vma && __vma->vm_start < vma->vm_end)
2165 		return -ENOMEM;
2166 	if ((vma->vm_flags & VM_ACCOUNT) &&
2167 	     security_vm_enough_memory_mm(mm, vma_pages(vma)))
2168 		return -ENOMEM;
2169 	vma_link(mm, vma, prev, rb_link, rb_parent);
2170 	return 0;
2171 }
2172 
2173 /*
2174  * Copy the vma structure to a new location in the same mm,
2175  * prior to moving page table entries, to effect an mremap move.
2176  */
2177 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2178 	unsigned long addr, unsigned long len, pgoff_t pgoff)
2179 {
2180 	struct vm_area_struct *vma = *vmap;
2181 	unsigned long vma_start = vma->vm_start;
2182 	struct mm_struct *mm = vma->vm_mm;
2183 	struct vm_area_struct *new_vma, *prev;
2184 	struct rb_node **rb_link, *rb_parent;
2185 	struct mempolicy *pol;
2186 
2187 	/*
2188 	 * If anonymous vma has not yet been faulted, update new pgoff
2189 	 * to match new location, to increase its chance of merging.
2190 	 */
2191 	if (!vma->vm_file && !vma->anon_vma)
2192 		pgoff = addr >> PAGE_SHIFT;
2193 
2194 	find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2195 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2196 			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2197 	if (new_vma) {
2198 		/*
2199 		 * Source vma may have been merged into new_vma
2200 		 */
2201 		if (vma_start >= new_vma->vm_start &&
2202 		    vma_start < new_vma->vm_end)
2203 			*vmap = new_vma;
2204 	} else {
2205 		new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2206 		if (new_vma) {
2207 			*new_vma = *vma;
2208 			pol = mpol_dup(vma_policy(vma));
2209 			if (IS_ERR(pol)) {
2210 				kmem_cache_free(vm_area_cachep, new_vma);
2211 				return NULL;
2212 			}
2213 			vma_set_policy(new_vma, pol);
2214 			new_vma->vm_start = addr;
2215 			new_vma->vm_end = addr + len;
2216 			new_vma->vm_pgoff = pgoff;
2217 			if (new_vma->vm_file) {
2218 				get_file(new_vma->vm_file);
2219 				if (vma->vm_flags & VM_EXECUTABLE)
2220 					added_exe_file_vma(mm);
2221 			}
2222 			if (new_vma->vm_ops && new_vma->vm_ops->open)
2223 				new_vma->vm_ops->open(new_vma);
2224 			vma_link(mm, new_vma, prev, rb_link, rb_parent);
2225 		}
2226 	}
2227 	return new_vma;
2228 }
2229 
2230 /*
2231  * Return true if the calling process may expand its vm space by the passed
2232  * number of pages
2233  */
2234 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2235 {
2236 	unsigned long cur = mm->total_vm;	/* pages */
2237 	unsigned long lim;
2238 
2239 	lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
2240 
2241 	if (cur + npages > lim)
2242 		return 0;
2243 	return 1;
2244 }
2245 
2246 
2247 static int special_mapping_fault(struct vm_area_struct *vma,
2248 				struct vm_fault *vmf)
2249 {
2250 	pgoff_t pgoff;
2251 	struct page **pages;
2252 
2253 	/*
2254 	 * special mappings have no vm_file, and in that case, the mm
2255 	 * uses vm_pgoff internally. So we have to subtract it from here.
2256 	 * We are allowed to do this because we are the mm; do not copy
2257 	 * this code into drivers!
2258 	 */
2259 	pgoff = vmf->pgoff - vma->vm_pgoff;
2260 
2261 	for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2262 		pgoff--;
2263 
2264 	if (*pages) {
2265 		struct page *page = *pages;
2266 		get_page(page);
2267 		vmf->page = page;
2268 		return 0;
2269 	}
2270 
2271 	return VM_FAULT_SIGBUS;
2272 }
2273 
2274 /*
2275  * Having a close hook prevents vma merging regardless of flags.
2276  */
2277 static void special_mapping_close(struct vm_area_struct *vma)
2278 {
2279 }
2280 
2281 static const struct vm_operations_struct special_mapping_vmops = {
2282 	.close = special_mapping_close,
2283 	.fault = special_mapping_fault,
2284 };
2285 
2286 /*
2287  * Called with mm->mmap_sem held for writing.
2288  * Insert a new vma covering the given region, with the given flags.
2289  * Its pages are supplied by the given array of struct page *.
2290  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2291  * The region past the last page supplied will always produce SIGBUS.
2292  * The array pointer and the pages it points to are assumed to stay alive
2293  * for as long as this mapping might exist.
2294  */
2295 int install_special_mapping(struct mm_struct *mm,
2296 			    unsigned long addr, unsigned long len,
2297 			    unsigned long vm_flags, struct page **pages)
2298 {
2299 	struct vm_area_struct *vma;
2300 
2301 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2302 	if (unlikely(vma == NULL))
2303 		return -ENOMEM;
2304 
2305 	vma->vm_mm = mm;
2306 	vma->vm_start = addr;
2307 	vma->vm_end = addr + len;
2308 
2309 	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2310 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2311 
2312 	vma->vm_ops = &special_mapping_vmops;
2313 	vma->vm_private_data = pages;
2314 
2315 	if (unlikely(insert_vm_struct(mm, vma))) {
2316 		kmem_cache_free(vm_area_cachep, vma);
2317 		return -ENOMEM;
2318 	}
2319 
2320 	mm->total_vm += len >> PAGE_SHIFT;
2321 
2322 	perf_event_mmap(vma);
2323 
2324 	return 0;
2325 }
2326 
2327 static DEFINE_MUTEX(mm_all_locks_mutex);
2328 
2329 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2330 {
2331 	if (!test_bit(0, (unsigned long *) &anon_vma->head.next)) {
2332 		/*
2333 		 * The LSB of head.next can't change from under us
2334 		 * because we hold the mm_all_locks_mutex.
2335 		 */
2336 		spin_lock_nest_lock(&anon_vma->lock, &mm->mmap_sem);
2337 		/*
2338 		 * We can safely modify head.next after taking the
2339 		 * anon_vma->lock. If some other vma in this mm shares
2340 		 * the same anon_vma we won't take it again.
2341 		 *
2342 		 * No need of atomic instructions here, head.next
2343 		 * can't change from under us thanks to the
2344 		 * anon_vma->lock.
2345 		 */
2346 		if (__test_and_set_bit(0, (unsigned long *)
2347 				       &anon_vma->head.next))
2348 			BUG();
2349 	}
2350 }
2351 
2352 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2353 {
2354 	if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2355 		/*
2356 		 * AS_MM_ALL_LOCKS can't change from under us because
2357 		 * we hold the mm_all_locks_mutex.
2358 		 *
2359 		 * Operations on ->flags have to be atomic because
2360 		 * even if AS_MM_ALL_LOCKS is stable thanks to the
2361 		 * mm_all_locks_mutex, there may be other cpus
2362 		 * changing other bitflags in parallel to us.
2363 		 */
2364 		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2365 			BUG();
2366 		spin_lock_nest_lock(&mapping->i_mmap_lock, &mm->mmap_sem);
2367 	}
2368 }
2369 
2370 /*
2371  * This operation locks against the VM for all pte/vma/mm related
2372  * operations that could ever happen on a certain mm. This includes
2373  * vmtruncate, try_to_unmap, and all page faults.
2374  *
2375  * The caller must take the mmap_sem in write mode before calling
2376  * mm_take_all_locks(). The caller isn't allowed to release the
2377  * mmap_sem until mm_drop_all_locks() returns.
2378  *
2379  * mmap_sem in write mode is required in order to block all operations
2380  * that could modify pagetables and free pages without need of
2381  * altering the vma layout (for example populate_range() with
2382  * nonlinear vmas). It's also needed in write mode to avoid new
2383  * anon_vmas to be associated with existing vmas.
2384  *
2385  * A single task can't take more than one mm_take_all_locks() in a row
2386  * or it would deadlock.
2387  *
2388  * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in
2389  * mapping->flags avoid to take the same lock twice, if more than one
2390  * vma in this mm is backed by the same anon_vma or address_space.
2391  *
2392  * We can take all the locks in random order because the VM code
2393  * taking i_mmap_lock or anon_vma->lock outside the mmap_sem never
2394  * takes more than one of them in a row. Secondly we're protected
2395  * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2396  *
2397  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2398  * that may have to take thousand of locks.
2399  *
2400  * mm_take_all_locks() can fail if it's interrupted by signals.
2401  */
2402 int mm_take_all_locks(struct mm_struct *mm)
2403 {
2404 	struct vm_area_struct *vma;
2405 	int ret = -EINTR;
2406 
2407 	BUG_ON(down_read_trylock(&mm->mmap_sem));
2408 
2409 	mutex_lock(&mm_all_locks_mutex);
2410 
2411 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2412 		if (signal_pending(current))
2413 			goto out_unlock;
2414 		if (vma->vm_file && vma->vm_file->f_mapping)
2415 			vm_lock_mapping(mm, vma->vm_file->f_mapping);
2416 	}
2417 
2418 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2419 		if (signal_pending(current))
2420 			goto out_unlock;
2421 		if (vma->anon_vma)
2422 			vm_lock_anon_vma(mm, vma->anon_vma);
2423 	}
2424 
2425 	ret = 0;
2426 
2427 out_unlock:
2428 	if (ret)
2429 		mm_drop_all_locks(mm);
2430 
2431 	return ret;
2432 }
2433 
2434 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2435 {
2436 	if (test_bit(0, (unsigned long *) &anon_vma->head.next)) {
2437 		/*
2438 		 * The LSB of head.next can't change to 0 from under
2439 		 * us because we hold the mm_all_locks_mutex.
2440 		 *
2441 		 * We must however clear the bitflag before unlocking
2442 		 * the vma so the users using the anon_vma->head will
2443 		 * never see our bitflag.
2444 		 *
2445 		 * No need of atomic instructions here, head.next
2446 		 * can't change from under us until we release the
2447 		 * anon_vma->lock.
2448 		 */
2449 		if (!__test_and_clear_bit(0, (unsigned long *)
2450 					  &anon_vma->head.next))
2451 			BUG();
2452 		spin_unlock(&anon_vma->lock);
2453 	}
2454 }
2455 
2456 static void vm_unlock_mapping(struct address_space *mapping)
2457 {
2458 	if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2459 		/*
2460 		 * AS_MM_ALL_LOCKS can't change to 0 from under us
2461 		 * because we hold the mm_all_locks_mutex.
2462 		 */
2463 		spin_unlock(&mapping->i_mmap_lock);
2464 		if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2465 					&mapping->flags))
2466 			BUG();
2467 	}
2468 }
2469 
2470 /*
2471  * The mmap_sem cannot be released by the caller until
2472  * mm_drop_all_locks() returns.
2473  */
2474 void mm_drop_all_locks(struct mm_struct *mm)
2475 {
2476 	struct vm_area_struct *vma;
2477 
2478 	BUG_ON(down_read_trylock(&mm->mmap_sem));
2479 	BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2480 
2481 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
2482 		if (vma->anon_vma)
2483 			vm_unlock_anon_vma(vma->anon_vma);
2484 		if (vma->vm_file && vma->vm_file->f_mapping)
2485 			vm_unlock_mapping(vma->vm_file->f_mapping);
2486 	}
2487 
2488 	mutex_unlock(&mm_all_locks_mutex);
2489 }
2490 
2491 /*
2492  * initialise the VMA slab
2493  */
2494 void __init mmap_init(void)
2495 {
2496 	int ret;
2497 
2498 	ret = percpu_counter_init(&vm_committed_as, 0);
2499 	VM_BUG_ON(ret);
2500 }
2501