]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * mm/mremap.c | |
3 | * | |
4 | * (C) Copyright 1996 Linus Torvalds | |
5 | * | |
6 | * Address space accounting code <alan@lxorguk.ukuu.org.uk> | |
7 | * (C) Copyright 2002 Red Hat Inc, All Rights Reserved | |
8 | */ | |
9 | ||
10 | #include <linux/mm.h> | |
11 | #include <linux/hugetlb.h> | |
12 | #include <linux/shm.h> | |
13 | #include <linux/ksm.h> | |
14 | #include <linux/mman.h> | |
15 | #include <linux/swap.h> | |
16 | #include <linux/capability.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/swapops.h> | |
19 | #include <linux/highmem.h> | |
20 | #include <linux/security.h> | |
21 | #include <linux/syscalls.h> | |
22 | #include <linux/mmu_notifier.h> | |
23 | #include <linux/uaccess.h> | |
24 | #include <linux/mm-arch-hooks.h> | |
25 | #include <linux/userfaultfd_k.h> | |
26 | ||
27 | #include <asm/cacheflush.h> | |
28 | #include <asm/tlbflush.h> | |
29 | ||
30 | #include "internal.h" | |
31 | ||
32 | static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) | |
33 | { | |
34 | pgd_t *pgd; | |
35 | p4d_t *p4d; | |
36 | pud_t *pud; | |
37 | pmd_t *pmd; | |
38 | ||
39 | pgd = pgd_offset(mm, addr); | |
40 | if (pgd_none_or_clear_bad(pgd)) | |
41 | return NULL; | |
42 | ||
43 | p4d = p4d_offset(pgd, addr); | |
44 | if (p4d_none_or_clear_bad(p4d)) | |
45 | return NULL; | |
46 | ||
47 | pud = pud_offset(p4d, addr); | |
48 | if (pud_none_or_clear_bad(pud)) | |
49 | return NULL; | |
50 | ||
51 | pmd = pmd_offset(pud, addr); | |
52 | if (pmd_none(*pmd)) | |
53 | return NULL; | |
54 | ||
55 | return pmd; | |
56 | } | |
57 | ||
58 | static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, | |
59 | unsigned long addr) | |
60 | { | |
61 | pgd_t *pgd; | |
62 | p4d_t *p4d; | |
63 | pud_t *pud; | |
64 | pmd_t *pmd; | |
65 | ||
66 | pgd = pgd_offset(mm, addr); | |
67 | p4d = p4d_alloc(mm, pgd, addr); | |
68 | if (!p4d) | |
69 | return NULL; | |
70 | pud = pud_alloc(mm, p4d, addr); | |
71 | if (!pud) | |
72 | return NULL; | |
73 | ||
74 | pmd = pmd_alloc(mm, pud, addr); | |
75 | if (!pmd) | |
76 | return NULL; | |
77 | ||
78 | VM_BUG_ON(pmd_trans_huge(*pmd)); | |
79 | ||
80 | return pmd; | |
81 | } | |
82 | ||
83 | static void take_rmap_locks(struct vm_area_struct *vma) | |
84 | { | |
85 | if (vma->vm_file) | |
86 | i_mmap_lock_write(vma->vm_file->f_mapping); | |
87 | if (vma->anon_vma) | |
88 | anon_vma_lock_write(vma->anon_vma); | |
89 | } | |
90 | ||
91 | static void drop_rmap_locks(struct vm_area_struct *vma) | |
92 | { | |
93 | if (vma->anon_vma) | |
94 | anon_vma_unlock_write(vma->anon_vma); | |
95 | if (vma->vm_file) | |
96 | i_mmap_unlock_write(vma->vm_file->f_mapping); | |
97 | } | |
98 | ||
99 | static pte_t move_soft_dirty_pte(pte_t pte) | |
100 | { | |
101 | /* | |
102 | * Set soft dirty bit so we can notice | |
103 | * in userspace the ptes were moved. | |
104 | */ | |
105 | #ifdef CONFIG_MEM_SOFT_DIRTY | |
106 | if (pte_present(pte)) | |
107 | pte = pte_mksoft_dirty(pte); | |
108 | else if (is_swap_pte(pte)) | |
109 | pte = pte_swp_mksoft_dirty(pte); | |
110 | #endif | |
111 | return pte; | |
112 | } | |
113 | ||
114 | static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, | |
115 | unsigned long old_addr, unsigned long old_end, | |
116 | struct vm_area_struct *new_vma, pmd_t *new_pmd, | |
117 | unsigned long new_addr, bool need_rmap_locks, bool *need_flush) | |
118 | { | |
119 | struct mm_struct *mm = vma->vm_mm; | |
120 | pte_t *old_pte, *new_pte, pte; | |
121 | spinlock_t *old_ptl, *new_ptl; | |
122 | bool force_flush = false; | |
123 | unsigned long len = old_end - old_addr; | |
124 | ||
125 | /* | |
126 | * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma | |
127 | * locks to ensure that rmap will always observe either the old or the | |
128 | * new ptes. This is the easiest way to avoid races with | |
129 | * truncate_pagecache(), page migration, etc... | |
130 | * | |
131 | * When need_rmap_locks is false, we use other ways to avoid | |
132 | * such races: | |
133 | * | |
134 | * - During exec() shift_arg_pages(), we use a specially tagged vma | |
135 | * which rmap call sites look for using is_vma_temporary_stack(). | |
136 | * | |
137 | * - During mremap(), new_vma is often known to be placed after vma | |
138 | * in rmap traversal order. This ensures rmap will always observe | |
139 | * either the old pte, or the new pte, or both (the page table locks | |
140 | * serialize access to individual ptes, but only rmap traversal | |
141 | * order guarantees that we won't miss both the old and new ptes). | |
142 | */ | |
143 | if (need_rmap_locks) | |
144 | take_rmap_locks(vma); | |
145 | ||
146 | /* | |
147 | * We don't have to worry about the ordering of src and dst | |
148 | * pte locks because exclusive mmap_sem prevents deadlock. | |
149 | */ | |
150 | old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); | |
151 | new_pte = pte_offset_map(new_pmd, new_addr); | |
152 | new_ptl = pte_lockptr(mm, new_pmd); | |
153 | if (new_ptl != old_ptl) | |
154 | spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); | |
155 | flush_tlb_batched_pending(vma->vm_mm); | |
156 | arch_enter_lazy_mmu_mode(); | |
157 | ||
158 | for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, | |
159 | new_pte++, new_addr += PAGE_SIZE) { | |
160 | if (pte_none(*old_pte)) | |
161 | continue; | |
162 | ||
163 | pte = ptep_get_and_clear(mm, old_addr, old_pte); | |
164 | /* | |
165 | * If we are remapping a dirty PTE, make sure | |
166 | * to flush TLB before we drop the PTL for the | |
167 | * old PTE or we may race with page_mkclean(). | |
168 | * | |
169 | * This check has to be done after we removed the | |
170 | * old PTE from page tables or another thread may | |
171 | * dirty it after the check and before the removal. | |
172 | */ | |
173 | if (pte_present(pte) && pte_dirty(pte)) | |
174 | force_flush = true; | |
175 | pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); | |
176 | pte = move_soft_dirty_pte(pte); | |
177 | set_pte_at(mm, new_addr, new_pte, pte); | |
178 | } | |
179 | ||
180 | arch_leave_lazy_mmu_mode(); | |
181 | if (new_ptl != old_ptl) | |
182 | spin_unlock(new_ptl); | |
183 | pte_unmap(new_pte - 1); | |
184 | if (force_flush) | |
185 | flush_tlb_range(vma, old_end - len, old_end); | |
186 | else | |
187 | *need_flush = true; | |
188 | pte_unmap_unlock(old_pte - 1, old_ptl); | |
189 | if (need_rmap_locks) | |
190 | drop_rmap_locks(vma); | |
191 | } | |
192 | ||
193 | #define LATENCY_LIMIT (64 * PAGE_SIZE) | |
194 | ||
195 | unsigned long move_page_tables(struct vm_area_struct *vma, | |
196 | unsigned long old_addr, struct vm_area_struct *new_vma, | |
197 | unsigned long new_addr, unsigned long len, | |
198 | bool need_rmap_locks) | |
199 | { | |
200 | unsigned long extent, next, old_end; | |
201 | pmd_t *old_pmd, *new_pmd; | |
202 | bool need_flush = false; | |
203 | unsigned long mmun_start; /* For mmu_notifiers */ | |
204 | unsigned long mmun_end; /* For mmu_notifiers */ | |
205 | ||
206 | old_end = old_addr + len; | |
207 | flush_cache_range(vma, old_addr, old_end); | |
208 | ||
209 | mmun_start = old_addr; | |
210 | mmun_end = old_end; | |
211 | mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); | |
212 | ||
213 | for (; old_addr < old_end; old_addr += extent, new_addr += extent) { | |
214 | cond_resched(); | |
215 | next = (old_addr + PMD_SIZE) & PMD_MASK; | |
216 | /* even if next overflowed, extent below will be ok */ | |
217 | extent = next - old_addr; | |
218 | if (extent > old_end - old_addr) | |
219 | extent = old_end - old_addr; | |
220 | old_pmd = get_old_pmd(vma->vm_mm, old_addr); | |
221 | if (!old_pmd) | |
222 | continue; | |
223 | new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); | |
224 | if (!new_pmd) | |
225 | break; | |
226 | if (pmd_trans_huge(*old_pmd)) { | |
227 | if (extent == HPAGE_PMD_SIZE) { | |
228 | bool moved; | |
229 | /* See comment in move_ptes() */ | |
230 | if (need_rmap_locks) | |
231 | take_rmap_locks(vma); | |
232 | moved = move_huge_pmd(vma, old_addr, new_addr, | |
233 | old_end, old_pmd, new_pmd, | |
234 | &need_flush); | |
235 | if (need_rmap_locks) | |
236 | drop_rmap_locks(vma); | |
237 | if (moved) | |
238 | continue; | |
239 | } | |
240 | split_huge_pmd(vma, old_pmd, old_addr); | |
241 | if (pmd_trans_unstable(old_pmd)) | |
242 | continue; | |
243 | } | |
244 | if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr)) | |
245 | break; | |
246 | next = (new_addr + PMD_SIZE) & PMD_MASK; | |
247 | if (extent > next - new_addr) | |
248 | extent = next - new_addr; | |
249 | if (extent > LATENCY_LIMIT) | |
250 | extent = LATENCY_LIMIT; | |
251 | move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, | |
252 | new_pmd, new_addr, need_rmap_locks, &need_flush); | |
253 | } | |
254 | if (need_flush) | |
255 | flush_tlb_range(vma, old_end-len, old_addr); | |
256 | ||
257 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
258 | ||
259 | return len + old_addr - old_end; /* how much done */ | |
260 | } | |
261 | ||
262 | static unsigned long move_vma(struct vm_area_struct *vma, | |
263 | unsigned long old_addr, unsigned long old_len, | |
264 | unsigned long new_len, unsigned long new_addr, | |
265 | bool *locked, struct vm_userfaultfd_ctx *uf, | |
266 | struct list_head *uf_unmap) | |
267 | { | |
268 | struct mm_struct *mm = vma->vm_mm; | |
269 | struct vm_area_struct *new_vma; | |
270 | unsigned long vm_flags = vma->vm_flags; | |
271 | unsigned long new_pgoff; | |
272 | unsigned long moved_len; | |
273 | unsigned long excess = 0; | |
274 | unsigned long hiwater_vm; | |
275 | int split = 0; | |
276 | int err; | |
277 | bool need_rmap_locks; | |
278 | ||
279 | /* | |
280 | * We'd prefer to avoid failure later on in do_munmap: | |
281 | * which may split one vma into three before unmapping. | |
282 | */ | |
283 | if (mm->map_count >= sysctl_max_map_count - 3) | |
284 | return -ENOMEM; | |
285 | ||
286 | /* | |
287 | * Advise KSM to break any KSM pages in the area to be moved: | |
288 | * it would be confusing if they were to turn up at the new | |
289 | * location, where they happen to coincide with different KSM | |
290 | * pages recently unmapped. But leave vma->vm_flags as it was, | |
291 | * so KSM can come around to merge on vma and new_vma afterwards. | |
292 | */ | |
293 | err = ksm_madvise(vma, old_addr, old_addr + old_len, | |
294 | MADV_UNMERGEABLE, &vm_flags); | |
295 | if (err) | |
296 | return err; | |
297 | ||
298 | new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); | |
299 | new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, | |
300 | &need_rmap_locks); | |
301 | if (!new_vma) | |
302 | return -ENOMEM; | |
303 | ||
304 | moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, | |
305 | need_rmap_locks); | |
306 | if (moved_len < old_len) { | |
307 | err = -ENOMEM; | |
308 | } else if (vma->vm_ops && vma->vm_ops->mremap) { | |
309 | err = vma->vm_ops->mremap(new_vma); | |
310 | } | |
311 | ||
312 | if (unlikely(err)) { | |
313 | /* | |
314 | * On error, move entries back from new area to old, | |
315 | * which will succeed since page tables still there, | |
316 | * and then proceed to unmap new area instead of old. | |
317 | */ | |
318 | move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, | |
319 | true); | |
320 | vma = new_vma; | |
321 | old_len = new_len; | |
322 | old_addr = new_addr; | |
323 | new_addr = err; | |
324 | } else { | |
325 | mremap_userfaultfd_prep(new_vma, uf); | |
326 | arch_remap(mm, old_addr, old_addr + old_len, | |
327 | new_addr, new_addr + new_len); | |
328 | } | |
329 | ||
330 | /* Conceal VM_ACCOUNT so old reservation is not undone */ | |
331 | if (vm_flags & VM_ACCOUNT) { | |
332 | vma->vm_flags &= ~VM_ACCOUNT; | |
333 | excess = vma->vm_end - vma->vm_start - old_len; | |
334 | if (old_addr > vma->vm_start && | |
335 | old_addr + old_len < vma->vm_end) | |
336 | split = 1; | |
337 | } | |
338 | ||
339 | /* | |
340 | * If we failed to move page tables we still do total_vm increment | |
341 | * since do_munmap() will decrement it by old_len == new_len. | |
342 | * | |
343 | * Since total_vm is about to be raised artificially high for a | |
344 | * moment, we need to restore high watermark afterwards: if stats | |
345 | * are taken meanwhile, total_vm and hiwater_vm appear too high. | |
346 | * If this were a serious issue, we'd add a flag to do_munmap(). | |
347 | */ | |
348 | hiwater_vm = mm->hiwater_vm; | |
349 | vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); | |
350 | ||
351 | /* Tell pfnmap has moved from this vma */ | |
352 | if (unlikely(vma->vm_flags & VM_PFNMAP)) | |
353 | untrack_pfn_moved(vma); | |
354 | ||
355 | if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { | |
356 | /* OOM: unable to split vma, just get accounts right */ | |
357 | vm_unacct_memory(excess >> PAGE_SHIFT); | |
358 | excess = 0; | |
359 | } | |
360 | mm->hiwater_vm = hiwater_vm; | |
361 | ||
362 | /* Restore VM_ACCOUNT if one or two pieces of vma left */ | |
363 | if (excess) { | |
364 | vma->vm_flags |= VM_ACCOUNT; | |
365 | if (split) | |
366 | vma->vm_next->vm_flags |= VM_ACCOUNT; | |
367 | } | |
368 | ||
369 | if (vm_flags & VM_LOCKED) { | |
370 | mm->locked_vm += new_len >> PAGE_SHIFT; | |
371 | *locked = true; | |
372 | } | |
373 | ||
374 | return new_addr; | |
375 | } | |
376 | ||
377 | static struct vm_area_struct *vma_to_resize(unsigned long addr, | |
378 | unsigned long old_len, unsigned long new_len, unsigned long *p) | |
379 | { | |
380 | struct mm_struct *mm = current->mm; | |
381 | struct vm_area_struct *vma = find_vma(mm, addr); | |
382 | unsigned long pgoff; | |
383 | ||
384 | if (!vma || vma->vm_start > addr) | |
385 | return ERR_PTR(-EFAULT); | |
386 | ||
387 | if (is_vm_hugetlb_page(vma)) | |
388 | return ERR_PTR(-EINVAL); | |
389 | ||
390 | /* We can't remap across vm area boundaries */ | |
391 | if (old_len > vma->vm_end - addr) | |
392 | return ERR_PTR(-EFAULT); | |
393 | ||
394 | if (new_len == old_len) | |
395 | return vma; | |
396 | ||
397 | /* Need to be careful about a growing mapping */ | |
398 | pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; | |
399 | pgoff += vma->vm_pgoff; | |
400 | if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) | |
401 | return ERR_PTR(-EINVAL); | |
402 | ||
403 | if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) | |
404 | return ERR_PTR(-EFAULT); | |
405 | ||
406 | if (vma->vm_flags & VM_LOCKED) { | |
407 | unsigned long locked, lock_limit; | |
408 | locked = mm->locked_vm << PAGE_SHIFT; | |
409 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
410 | locked += new_len - old_len; | |
411 | if (locked > lock_limit && !capable(CAP_IPC_LOCK)) | |
412 | return ERR_PTR(-EAGAIN); | |
413 | } | |
414 | ||
415 | if (!may_expand_vm(mm, vma->vm_flags, | |
416 | (new_len - old_len) >> PAGE_SHIFT)) | |
417 | return ERR_PTR(-ENOMEM); | |
418 | ||
419 | if (vma->vm_flags & VM_ACCOUNT) { | |
420 | unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; | |
421 | if (security_vm_enough_memory_mm(mm, charged)) | |
422 | return ERR_PTR(-ENOMEM); | |
423 | *p = charged; | |
424 | } | |
425 | ||
426 | return vma; | |
427 | } | |
428 | ||
429 | static unsigned long mremap_to(unsigned long addr, unsigned long old_len, | |
430 | unsigned long new_addr, unsigned long new_len, bool *locked, | |
431 | struct vm_userfaultfd_ctx *uf, | |
432 | struct list_head *uf_unmap_early, | |
433 | struct list_head *uf_unmap) | |
434 | { | |
435 | struct mm_struct *mm = current->mm; | |
436 | struct vm_area_struct *vma; | |
437 | unsigned long ret = -EINVAL; | |
438 | unsigned long charged = 0; | |
439 | unsigned long map_flags; | |
440 | ||
441 | if (offset_in_page(new_addr)) | |
442 | goto out; | |
443 | ||
444 | if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) | |
445 | goto out; | |
446 | ||
447 | /* Ensure the old/new locations do not overlap */ | |
448 | if (addr + old_len > new_addr && new_addr + new_len > addr) | |
449 | goto out; | |
450 | ||
451 | ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); | |
452 | if (ret) | |
453 | goto out; | |
454 | ||
455 | if (old_len >= new_len) { | |
456 | ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap); | |
457 | if (ret && old_len != new_len) | |
458 | goto out; | |
459 | old_len = new_len; | |
460 | } | |
461 | ||
462 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
463 | if (IS_ERR(vma)) { | |
464 | ret = PTR_ERR(vma); | |
465 | goto out; | |
466 | } | |
467 | ||
468 | map_flags = MAP_FIXED; | |
469 | if (vma->vm_flags & VM_MAYSHARE) | |
470 | map_flags |= MAP_SHARED; | |
471 | ||
472 | ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + | |
473 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
474 | map_flags); | |
475 | if (offset_in_page(ret)) | |
476 | goto out1; | |
477 | ||
478 | ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf, | |
479 | uf_unmap); | |
480 | if (!(offset_in_page(ret))) | |
481 | goto out; | |
482 | out1: | |
483 | vm_unacct_memory(charged); | |
484 | ||
485 | out: | |
486 | return ret; | |
487 | } | |
488 | ||
489 | static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) | |
490 | { | |
491 | unsigned long end = vma->vm_end + delta; | |
492 | if (end < vma->vm_end) /* overflow */ | |
493 | return 0; | |
494 | if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ | |
495 | return 0; | |
496 | if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, | |
497 | 0, MAP_FIXED) & ~PAGE_MASK) | |
498 | return 0; | |
499 | return 1; | |
500 | } | |
501 | ||
502 | /* | |
503 | * Expand (or shrink) an existing mapping, potentially moving it at the | |
504 | * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) | |
505 | * | |
506 | * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise | |
507 | * This option implies MREMAP_MAYMOVE. | |
508 | */ | |
509 | SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, | |
510 | unsigned long, new_len, unsigned long, flags, | |
511 | unsigned long, new_addr) | |
512 | { | |
513 | struct mm_struct *mm = current->mm; | |
514 | struct vm_area_struct *vma; | |
515 | unsigned long ret = -EINVAL; | |
516 | unsigned long charged = 0; | |
517 | bool locked = false; | |
518 | struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; | |
519 | LIST_HEAD(uf_unmap_early); | |
520 | LIST_HEAD(uf_unmap); | |
521 | ||
522 | if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) | |
523 | return ret; | |
524 | ||
525 | if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) | |
526 | return ret; | |
527 | ||
528 | if (offset_in_page(addr)) | |
529 | return ret; | |
530 | ||
531 | old_len = PAGE_ALIGN(old_len); | |
532 | new_len = PAGE_ALIGN(new_len); | |
533 | ||
534 | /* | |
535 | * We allow a zero old-len as a special case | |
536 | * for DOS-emu "duplicate shm area" thing. But | |
537 | * a zero new-len is nonsensical. | |
538 | */ | |
539 | if (!new_len) | |
540 | return ret; | |
541 | ||
542 | if (down_write_killable(¤t->mm->mmap_sem)) | |
543 | return -EINTR; | |
544 | ||
545 | if (flags & MREMAP_FIXED) { | |
546 | ret = mremap_to(addr, old_len, new_addr, new_len, | |
547 | &locked, &uf, &uf_unmap_early, &uf_unmap); | |
548 | goto out; | |
549 | } | |
550 | ||
551 | /* | |
552 | * Always allow a shrinking remap: that just unmaps | |
553 | * the unnecessary pages.. | |
554 | * do_munmap does all the needed commit accounting | |
555 | */ | |
556 | if (old_len >= new_len) { | |
557 | ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap); | |
558 | if (ret && old_len != new_len) | |
559 | goto out; | |
560 | ret = addr; | |
561 | goto out; | |
562 | } | |
563 | ||
564 | /* | |
565 | * Ok, we need to grow.. | |
566 | */ | |
567 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
568 | if (IS_ERR(vma)) { | |
569 | ret = PTR_ERR(vma); | |
570 | goto out; | |
571 | } | |
572 | ||
573 | /* old_len exactly to the end of the area.. | |
574 | */ | |
575 | if (old_len == vma->vm_end - addr) { | |
576 | /* can we just expand the current mapping? */ | |
577 | if (vma_expandable(vma, new_len - old_len)) { | |
578 | int pages = (new_len - old_len) >> PAGE_SHIFT; | |
579 | ||
580 | if (vma_adjust(vma, vma->vm_start, addr + new_len, | |
581 | vma->vm_pgoff, NULL)) { | |
582 | ret = -ENOMEM; | |
583 | goto out; | |
584 | } | |
585 | ||
586 | vm_stat_account(mm, vma->vm_flags, pages); | |
587 | if (vma->vm_flags & VM_LOCKED) { | |
588 | mm->locked_vm += pages; | |
589 | locked = true; | |
590 | new_addr = addr; | |
591 | } | |
592 | ret = addr; | |
593 | goto out; | |
594 | } | |
595 | } | |
596 | ||
597 | /* | |
598 | * We weren't able to just expand or shrink the area, | |
599 | * we need to create a new one and move it.. | |
600 | */ | |
601 | ret = -ENOMEM; | |
602 | if (flags & MREMAP_MAYMOVE) { | |
603 | unsigned long map_flags = 0; | |
604 | if (vma->vm_flags & VM_MAYSHARE) | |
605 | map_flags |= MAP_SHARED; | |
606 | ||
607 | new_addr = get_unmapped_area(vma->vm_file, 0, new_len, | |
608 | vma->vm_pgoff + | |
609 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
610 | map_flags); | |
611 | if (offset_in_page(new_addr)) { | |
612 | ret = new_addr; | |
613 | goto out; | |
614 | } | |
615 | ||
616 | ret = move_vma(vma, addr, old_len, new_len, new_addr, | |
617 | &locked, &uf, &uf_unmap); | |
618 | } | |
619 | out: | |
620 | if (offset_in_page(ret)) { | |
621 | vm_unacct_memory(charged); | |
622 | locked = 0; | |
623 | } | |
624 | up_write(¤t->mm->mmap_sem); | |
625 | if (locked && new_len > old_len) | |
626 | mm_populate(new_addr + old_len, new_len - old_len); | |
627 | userfaultfd_unmap_complete(mm, &uf_unmap_early); | |
628 | mremap_userfaultfd_complete(&uf, addr, new_addr, old_len); | |
629 | userfaultfd_unmap_complete(mm, &uf_unmap); | |
630 | return ret; | |
631 | } |