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/slab.h>
13 #include <linux/shm.h>
14 #include <linux/mman.h>
15 #include <linux/swap.h>
16 #include <linux/capability.h>
17 #include <linux/fs.h>
18 #include <linux/highmem.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/mmu_notifier.h>
22
23 #include <asm/uaccess.h>
24 #include <asm/cacheflush.h>
25 #include <asm/tlbflush.h>
26
27 #include "internal.h"
28
29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
30 {
31 pgd_t *pgd;
32 pud_t *pud;
33 pmd_t *pmd;
34
35 pgd = pgd_offset(mm, addr);
36 if (pgd_none_or_clear_bad(pgd))
37 return NULL;
38
39 pud = pud_offset(pgd, addr);
40 if (pud_none_or_clear_bad(pud))
41 return NULL;
42
43 pmd = pmd_offset(pud, addr);
44 if (pmd_none_or_clear_bad(pmd))
45 return NULL;
46
47 return pmd;
48 }
49
50 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
51 {
52 pgd_t *pgd;
53 pud_t *pud;
54 pmd_t *pmd;
55
56 pgd = pgd_offset(mm, addr);
57 pud = pud_alloc(mm, pgd, addr);
58 if (!pud)
59 return NULL;
60
61 pmd = pmd_alloc(mm, pud, addr);
62 if (!pmd)
63 return NULL;
64
65 if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
66 return NULL;
67
68 return pmd;
69 }
70
71 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
72 unsigned long old_addr, unsigned long old_end,
73 struct vm_area_struct *new_vma, pmd_t *new_pmd,
74 unsigned long new_addr)
75 {
76 struct address_space *mapping = NULL;
77 struct mm_struct *mm = vma->vm_mm;
78 pte_t *old_pte, *new_pte, pte;
79 spinlock_t *old_ptl, *new_ptl;
80 unsigned long old_start;
81
82 old_start = old_addr;
83 mmu_notifier_invalidate_range_start(vma->vm_mm,
84 old_start, old_end);
85 if (vma->vm_file) {
86 /*
87 * Subtle point from Rajesh Venkatasubramanian: before
88 * moving file-based ptes, we must lock vmtruncate out,
89 * since it might clean the dst vma before the src vma,
90 * and we propagate stale pages into the dst afterward.
91 */
92 mapping = vma->vm_file->f_mapping;
93 spin_lock(&mapping->i_mmap_lock);
94 if (new_vma->vm_truncate_count &&
95 new_vma->vm_truncate_count != vma->vm_truncate_count)
96 new_vma->vm_truncate_count = 0;
97 }
98
99 /*
100 * We don't have to worry about the ordering of src and dst
101 * pte locks because exclusive mmap_sem prevents deadlock.
102 */
103 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
104 new_pte = pte_offset_map_nested(new_pmd, new_addr);
105 new_ptl = pte_lockptr(mm, new_pmd);
106 if (new_ptl != old_ptl)
107 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
108 arch_enter_lazy_mmu_mode();
109
110 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
111 new_pte++, new_addr += PAGE_SIZE) {
112 if (pte_none(*old_pte))
113 continue;
114 pte = ptep_clear_flush(vma, old_addr, old_pte);
115 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
116 set_pte_at(mm, new_addr, new_pte, pte);
117 }
118
119 arch_leave_lazy_mmu_mode();
120 if (new_ptl != old_ptl)
121 spin_unlock(new_ptl);
122 pte_unmap_nested(new_pte - 1);
123 pte_unmap_unlock(old_pte - 1, old_ptl);
124 if (mapping)
125 spin_unlock(&mapping->i_mmap_lock);
126 mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
127 }
128
129 #define LATENCY_LIMIT (64 * PAGE_SIZE)
130
131 unsigned long move_page_tables(struct vm_area_struct *vma,
132 unsigned long old_addr, struct vm_area_struct *new_vma,
133 unsigned long new_addr, unsigned long len)
134 {
135 unsigned long extent, next, old_end;
136 pmd_t *old_pmd, *new_pmd;
137
138 old_end = old_addr + len;
139 flush_cache_range(vma, old_addr, old_end);
140
141 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
142 cond_resched();
143 next = (old_addr + PMD_SIZE) & PMD_MASK;
144 if (next - 1 > old_end)
145 next = old_end;
146 extent = next - old_addr;
147 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
148 if (!old_pmd)
149 continue;
150 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
151 if (!new_pmd)
152 break;
153 next = (new_addr + PMD_SIZE) & PMD_MASK;
154 if (extent > next - new_addr)
155 extent = next - new_addr;
156 if (extent > LATENCY_LIMIT)
157 extent = LATENCY_LIMIT;
158 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
159 new_vma, new_pmd, new_addr);
160 }
161
162 return len + old_addr - old_end; /* how much done */
163 }
164
165 static unsigned long move_vma(struct vm_area_struct *vma,
166 unsigned long old_addr, unsigned long old_len,
167 unsigned long new_len, unsigned long new_addr)
168 {
169 struct mm_struct *mm = vma->vm_mm;
170 struct vm_area_struct *new_vma;
171 unsigned long vm_flags = vma->vm_flags;
172 unsigned long new_pgoff;
173 unsigned long moved_len;
174 unsigned long excess = 0;
175 unsigned long hiwater_vm;
176 int split = 0;
177
178 /*
179 * We'd prefer to avoid failure later on in do_munmap:
180 * which may split one vma into three before unmapping.
181 */
182 if (mm->map_count >= sysctl_max_map_count - 3)
183 return -ENOMEM;
184
185 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
186 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
187 if (!new_vma)
188 return -ENOMEM;
189
190 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
191 if (moved_len < old_len) {
192 /*
193 * On error, move entries back from new area to old,
194 * which will succeed since page tables still there,
195 * and then proceed to unmap new area instead of old.
196 */
197 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
198 vma = new_vma;
199 old_len = new_len;
200 old_addr = new_addr;
201 new_addr = -ENOMEM;
202 }
203
204 /* Conceal VM_ACCOUNT so old reservation is not undone */
205 if (vm_flags & VM_ACCOUNT) {
206 vma->vm_flags &= ~VM_ACCOUNT;
207 excess = vma->vm_end - vma->vm_start - old_len;
208 if (old_addr > vma->vm_start &&
209 old_addr + old_len < vma->vm_end)
210 split = 1;
211 }
212
213 /*
214 * If we failed to move page tables we still do total_vm increment
215 * since do_munmap() will decrement it by old_len == new_len.
216 *
217 * Since total_vm is about to be raised artificially high for a
218 * moment, we need to restore high watermark afterwards: if stats
219 * are taken meanwhile, total_vm and hiwater_vm appear too high.
220 * If this were a serious issue, we'd add a flag to do_munmap().
221 */
222 hiwater_vm = mm->hiwater_vm;
223 mm->total_vm += new_len >> PAGE_SHIFT;
224 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
225
226 if (do_munmap(mm, old_addr, old_len) < 0) {
227 /* OOM: unable to split vma, just get accounts right */
228 vm_unacct_memory(excess >> PAGE_SHIFT);
229 excess = 0;
230 }
231 mm->hiwater_vm = hiwater_vm;
232
233 /* Restore VM_ACCOUNT if one or two pieces of vma left */
234 if (excess) {
235 vma->vm_flags |= VM_ACCOUNT;
236 if (split)
237 vma->vm_next->vm_flags |= VM_ACCOUNT;
238 }
239
240 if (vm_flags & VM_LOCKED) {
241 mm->locked_vm += new_len >> PAGE_SHIFT;
242 if (new_len > old_len)
243 mlock_vma_pages_range(new_vma, new_addr + old_len,
244 new_addr + new_len);
245 }
246
247 return new_addr;
248 }
249
250 /*
251 * Expand (or shrink) an existing mapping, potentially moving it at the
252 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
253 *
254 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
255 * This option implies MREMAP_MAYMOVE.
256 */
257 unsigned long do_mremap(unsigned long addr,
258 unsigned long old_len, unsigned long new_len,
259 unsigned long flags, unsigned long new_addr)
260 {
261 struct mm_struct *mm = current->mm;
262 struct vm_area_struct *vma;
263 unsigned long ret = -EINVAL;
264 unsigned long charged = 0;
265
266 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
267 goto out;
268
269 if (addr & ~PAGE_MASK)
270 goto out;
271
272 old_len = PAGE_ALIGN(old_len);
273 new_len = PAGE_ALIGN(new_len);
274
275 /*
276 * We allow a zero old-len as a special case
277 * for DOS-emu "duplicate shm area" thing. But
278 * a zero new-len is nonsensical.
279 */
280 if (!new_len)
281 goto out;
282
283 /* new_addr is only valid if MREMAP_FIXED is specified */
284 if (flags & MREMAP_FIXED) {
285 if (new_addr & ~PAGE_MASK)
286 goto out;
287 if (!(flags & MREMAP_MAYMOVE))
288 goto out;
289
290 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
291 goto out;
292
293 /* Check if the location we're moving into overlaps the
294 * old location at all, and fail if it does.
295 */
296 if ((new_addr <= addr) && (new_addr+new_len) > addr)
297 goto out;
298
299 if ((addr <= new_addr) && (addr+old_len) > new_addr)
300 goto out;
301
302 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
303 if (ret)
304 goto out;
305
306 ret = do_munmap(mm, new_addr, new_len);
307 if (ret)
308 goto out;
309 }
310
311 /*
312 * Always allow a shrinking remap: that just unmaps
313 * the unnecessary pages..
314 * do_munmap does all the needed commit accounting
315 */
316 if (old_len >= new_len) {
317 ret = do_munmap(mm, addr+new_len, old_len - new_len);
318 if (ret && old_len != new_len)
319 goto out;
320 ret = addr;
321 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
322 goto out;
323 old_len = new_len;
324 }
325
326 /*
327 * Ok, we need to grow.. or relocate.
328 */
329 ret = -EFAULT;
330 vma = find_vma(mm, addr);
331 if (!vma || vma->vm_start > addr)
332 goto out;
333 if (is_vm_hugetlb_page(vma)) {
334 ret = -EINVAL;
335 goto out;
336 }
337 /* We can't remap across vm area boundaries */
338 if (old_len > vma->vm_end - addr)
339 goto out;
340 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
341 if (new_len > old_len)
342 goto out;
343 }
344 if (vma->vm_flags & VM_LOCKED) {
345 unsigned long locked, lock_limit;
346 locked = mm->locked_vm << PAGE_SHIFT;
347 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
348 locked += new_len - old_len;
349 ret = -EAGAIN;
350 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
351 goto out;
352 }
353 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
354 ret = -ENOMEM;
355 goto out;
356 }
357
358 if (vma->vm_flags & VM_ACCOUNT) {
359 charged = (new_len - old_len) >> PAGE_SHIFT;
360 if (security_vm_enough_memory(charged))
361 goto out_nc;
362 }
363
364 /* old_len exactly to the end of the area..
365 * And we're not relocating the area.
366 */
367 if (old_len == vma->vm_end - addr &&
368 !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
369 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
370 unsigned long max_addr = TASK_SIZE;
371 if (vma->vm_next)
372 max_addr = vma->vm_next->vm_start;
373 /* can we just expand the current mapping? */
374 if (max_addr - addr >= new_len) {
375 int pages = (new_len - old_len) >> PAGE_SHIFT;
376
377 vma_adjust(vma, vma->vm_start,
378 addr + new_len, vma->vm_pgoff, NULL);
379
380 mm->total_vm += pages;
381 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
382 if (vma->vm_flags & VM_LOCKED) {
383 mm->locked_vm += pages;
384 mlock_vma_pages_range(vma, addr + old_len,
385 addr + new_len);
386 }
387 ret = addr;
388 goto out;
389 }
390 }
391
392 /*
393 * We weren't able to just expand or shrink the area,
394 * we need to create a new one and move it..
395 */
396 ret = -ENOMEM;
397 if (flags & MREMAP_MAYMOVE) {
398 if (!(flags & MREMAP_FIXED)) {
399 unsigned long map_flags = 0;
400 if (vma->vm_flags & VM_MAYSHARE)
401 map_flags |= MAP_SHARED;
402
403 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
404 vma->vm_pgoff, map_flags);
405 if (new_addr & ~PAGE_MASK) {
406 ret = new_addr;
407 goto out;
408 }
409
410 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
411 if (ret)
412 goto out;
413 }
414 ret = move_vma(vma, addr, old_len, new_len, new_addr);
415 }
416 out:
417 if (ret & ~PAGE_MASK)
418 vm_unacct_memory(charged);
419 out_nc:
420 return ret;
421 }
422
423 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
424 unsigned long, new_len, unsigned long, flags,
425 unsigned long, new_addr)
426 {
427 unsigned long ret;
428
429 down_write(¤t->mm->mmap_sem);
430 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
431 up_write(¤t->mm->mmap_sem);
432 return ret;
433 }
434
|
This page was automatically generated by the
LXR engine.
|