FreeBSD/Linux Kernel Cross Reference
sys/mm/mremap.c
1 /*
2 * linux/mm/remap.c
3 *
4 * (C) Copyright 1996 Linus Torvalds
5 */
6
7 #include <linux/slab.h>
8 #include <linux/smp_lock.h>
9 #include <linux/shm.h>
10 #include <linux/mman.h>
11 #include <linux/swap.h>
12
13 #include <asm/uaccess.h>
14 #include <asm/pgalloc.h>
15
16 extern int vm_enough_memory(long pages);
17
18 static inline pte_t *get_one_pte(struct mm_struct *mm, unsigned long addr)
19 {
20 pgd_t * pgd;
21 pmd_t * pmd;
22 pte_t * pte = NULL;
23
24 pgd = pgd_offset(mm, addr);
25 if (pgd_none(*pgd))
26 goto end;
27 if (pgd_bad(*pgd)) {
28 pgd_ERROR(*pgd);
29 pgd_clear(pgd);
30 goto end;
31 }
32
33 pmd = pmd_offset(pgd, addr);
34 if (pmd_none(*pmd))
35 goto end;
36 if (pmd_bad(*pmd)) {
37 pmd_ERROR(*pmd);
38 pmd_clear(pmd);
39 goto end;
40 }
41
42 pte = pte_offset(pmd, addr);
43 if (pte_none(*pte))
44 pte = NULL;
45 end:
46 return pte;
47 }
48
49 static inline pte_t *alloc_one_pte(struct mm_struct *mm, unsigned long addr)
50 {
51 pmd_t * pmd;
52 pte_t * pte = NULL;
53
54 pmd = pmd_alloc(mm, pgd_offset(mm, addr), addr);
55 if (pmd)
56 pte = pte_alloc(mm, pmd, addr);
57 return pte;
58 }
59
60 static inline int copy_one_pte(struct mm_struct *mm, pte_t * src, pte_t * dst)
61 {
62 int error = 0;
63 pte_t pte;
64
65 if (!pte_none(*src)) {
66 pte = ptep_get_and_clear(src);
67 if (!dst) {
68 /* No dest? We must put it back. */
69 dst = src;
70 error++;
71 }
72 set_pte(dst, pte);
73 }
74 return error;
75 }
76
77 static int move_one_page(struct mm_struct *mm, unsigned long old_addr, unsigned long new_addr)
78 {
79 int error = 0;
80 pte_t * src;
81
82 spin_lock(&mm->page_table_lock);
83 src = get_one_pte(mm, old_addr);
84 if (src)
85 error = copy_one_pte(mm, src, alloc_one_pte(mm, new_addr));
86 spin_unlock(&mm->page_table_lock);
87 return error;
88 }
89
90 static int move_page_tables(struct mm_struct * mm,
91 unsigned long new_addr, unsigned long old_addr, unsigned long len)
92 {
93 unsigned long offset = len;
94
95 flush_cache_range(mm, old_addr, old_addr + len);
96
97 /*
98 * This is not the clever way to do this, but we're taking the
99 * easy way out on the assumption that most remappings will be
100 * only a few pages.. This also makes error recovery easier.
101 */
102 while (offset) {
103 offset -= PAGE_SIZE;
104 if (move_one_page(mm, old_addr + offset, new_addr + offset))
105 goto oops_we_failed;
106 }
107 flush_tlb_range(mm, old_addr, old_addr + len);
108 return 0;
109
110 /*
111 * Ok, the move failed because we didn't have enough pages for
112 * the new page table tree. This is unlikely, but we have to
113 * take the possibility into account. In that case we just move
114 * all the pages back (this will work, because we still have
115 * the old page tables)
116 */
117 oops_we_failed:
118 flush_cache_range(mm, new_addr, new_addr + len);
119 while ((offset += PAGE_SIZE) < len)
120 move_one_page(mm, new_addr + offset, old_addr + offset);
121 zap_page_range(mm, new_addr, len);
122 return -1;
123 }
124
125 static inline unsigned long move_vma(struct vm_area_struct * vma,
126 unsigned long addr, unsigned long old_len, unsigned long new_len,
127 unsigned long new_addr)
128 {
129 struct mm_struct * mm = vma->vm_mm;
130 struct vm_area_struct * new_vma, * next, * prev;
131 int allocated_vma;
132
133 new_vma = NULL;
134 next = find_vma_prev(mm, new_addr, &prev);
135 if (next) {
136 if (prev && prev->vm_end == new_addr &&
137 can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
138 spin_lock(&mm->page_table_lock);
139 prev->vm_end = new_addr + new_len;
140 spin_unlock(&mm->page_table_lock);
141 new_vma = prev;
142 if (next != prev->vm_next)
143 BUG();
144 if (prev->vm_end == next->vm_start && can_vma_merge(next, prev->vm_flags)) {
145 spin_lock(&mm->page_table_lock);
146 prev->vm_end = next->vm_end;
147 __vma_unlink(mm, next, prev);
148 spin_unlock(&mm->page_table_lock);
149
150 mm->map_count--;
151 kmem_cache_free(vm_area_cachep, next);
152 }
153 } else if (next->vm_start == new_addr + new_len &&
154 can_vma_merge(next, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
155 spin_lock(&mm->page_table_lock);
156 next->vm_start = new_addr;
157 spin_unlock(&mm->page_table_lock);
158 new_vma = next;
159 }
160 } else {
161 prev = find_vma(mm, new_addr-1);
162 if (prev && prev->vm_end == new_addr &&
163 can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
164 spin_lock(&mm->page_table_lock);
165 prev->vm_end = new_addr + new_len;
166 spin_unlock(&mm->page_table_lock);
167 new_vma = prev;
168 }
169 }
170
171 allocated_vma = 0;
172 if (!new_vma) {
173 new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
174 if (!new_vma)
175 goto out;
176 allocated_vma = 1;
177 }
178
179 if (!move_page_tables(current->mm, new_addr, addr, old_len)) {
180 unsigned long vm_locked = vma->vm_flags & VM_LOCKED;
181
182 if (allocated_vma) {
183 *new_vma = *vma;
184 new_vma->vm_start = new_addr;
185 new_vma->vm_end = new_addr+new_len;
186 new_vma->vm_pgoff += (addr-vma->vm_start) >> PAGE_SHIFT;
187 new_vma->vm_raend = 0;
188 if (new_vma->vm_file)
189 get_file(new_vma->vm_file);
190 if (new_vma->vm_ops && new_vma->vm_ops->open)
191 new_vma->vm_ops->open(new_vma);
192 insert_vm_struct(current->mm, new_vma);
193 }
194
195 do_munmap(current->mm, addr, old_len);
196
197 current->mm->total_vm += new_len >> PAGE_SHIFT;
198 if (vm_locked) {
199 current->mm->locked_vm += new_len >> PAGE_SHIFT;
200 if (new_len > old_len)
201 make_pages_present(new_addr + old_len,
202 new_addr + new_len);
203 }
204 return new_addr;
205 }
206 if (allocated_vma)
207 kmem_cache_free(vm_area_cachep, new_vma);
208 out:
209 return -ENOMEM;
210 }
211
212 /*
213 * Expand (or shrink) an existing mapping, potentially moving it at the
214 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
215 *
216 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
217 * This option implies MREMAP_MAYMOVE.
218 */
219 unsigned long do_mremap(unsigned long addr,
220 unsigned long old_len, unsigned long new_len,
221 unsigned long flags, unsigned long new_addr)
222 {
223 struct vm_area_struct *vma;
224 unsigned long ret = -EINVAL;
225
226 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
227 goto out;
228
229 if (addr & ~PAGE_MASK)
230 goto out;
231
232 old_len = PAGE_ALIGN(old_len);
233 new_len = PAGE_ALIGN(new_len);
234
235 /* new_addr is only valid if MREMAP_FIXED is specified */
236 if (flags & MREMAP_FIXED) {
237 if (new_addr & ~PAGE_MASK)
238 goto out;
239 if (!(flags & MREMAP_MAYMOVE))
240 goto out;
241
242 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
243 goto out;
244
245 /* Check if the location we're moving into overlaps the
246 * old location at all, and fail if it does.
247 */
248 if ((new_addr <= addr) && (new_addr+new_len) > addr)
249 goto out;
250
251 if ((addr <= new_addr) && (addr+old_len) > new_addr)
252 goto out;
253
254 do_munmap(current->mm, new_addr, new_len);
255 }
256
257 /*
258 * Always allow a shrinking remap: that just unmaps
259 * the unnecessary pages..
260 */
261 ret = addr;
262 if (old_len >= new_len) {
263 do_munmap(current->mm, addr+new_len, old_len - new_len);
264 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
265 goto out;
266 }
267
268 /*
269 * Ok, we need to grow.. or relocate.
270 */
271 ret = -EFAULT;
272 vma = find_vma(current->mm, addr);
273 if (!vma || vma->vm_start > addr)
274 goto out;
275 /* We can't remap across vm area boundaries */
276 if (old_len > vma->vm_end - addr)
277 goto out;
278 if (vma->vm_flags & VM_DONTEXPAND) {
279 if (new_len > old_len)
280 goto out;
281 }
282 if (vma->vm_flags & VM_LOCKED) {
283 unsigned long locked = current->mm->locked_vm << PAGE_SHIFT;
284 locked += new_len - old_len;
285 ret = -EAGAIN;
286 if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
287 goto out;
288 }
289 ret = -ENOMEM;
290 if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
291 > current->rlim[RLIMIT_AS].rlim_cur)
292 goto out;
293 /* Private writable mapping? Check memory availability.. */
294 if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE &&
295 !(flags & MAP_NORESERVE) &&
296 !vm_enough_memory((new_len - old_len) >> PAGE_SHIFT))
297 goto out;
298
299 /* old_len exactly to the end of the area..
300 * And we're not relocating the area.
301 */
302 if (old_len == vma->vm_end - addr &&
303 !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
304 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
305 unsigned long max_addr = TASK_SIZE;
306 if (vma->vm_next)
307 max_addr = vma->vm_next->vm_start;
308 /* can we just expand the current mapping? */
309 if (max_addr - addr >= new_len) {
310 int pages = (new_len - old_len) >> PAGE_SHIFT;
311 spin_lock(&vma->vm_mm->page_table_lock);
312 vma->vm_end = addr + new_len;
313 spin_unlock(&vma->vm_mm->page_table_lock);
314 current->mm->total_vm += pages;
315 if (vma->vm_flags & VM_LOCKED) {
316 current->mm->locked_vm += pages;
317 make_pages_present(addr + old_len,
318 addr + new_len);
319 }
320 ret = addr;
321 goto out;
322 }
323 }
324
325 /*
326 * We weren't able to just expand or shrink the area,
327 * we need to create a new one and move it..
328 */
329 ret = -ENOMEM;
330 if (flags & MREMAP_MAYMOVE) {
331 if (!(flags & MREMAP_FIXED)) {
332 unsigned long map_flags = 0;
333 if (vma->vm_flags & VM_SHARED)
334 map_flags |= MAP_SHARED;
335
336 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, vma->vm_pgoff, map_flags);
337 ret = new_addr;
338 if (new_addr & ~PAGE_MASK)
339 goto out;
340 }
341 ret = move_vma(vma, addr, old_len, new_len, new_addr);
342 }
343 out:
344 return ret;
345 }
346
347 asmlinkage unsigned long sys_mremap(unsigned long addr,
348 unsigned long old_len, unsigned long new_len,
349 unsigned long flags, unsigned long new_addr)
350 {
351 unsigned long ret;
352
353 down_write(¤t->mm->mmap_sem);
354 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
355 up_write(¤t->mm->mmap_sem);
356 return ret;
357 }
Cache object: 5be368bcdf841b936330c3ef5a108fae
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