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(pgd_offset(mm, addr), addr);
55 if (pmd)
56 pte = pte_alloc(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 spin_lock(&mm->page_table_lock);
66 if (!pte_none(*src)) {
67 pte = ptep_get_and_clear(src);
68 if (!dst) {
69 /* No dest? We must put it back. */
70 dst = src;
71 error++;
72 }
73 set_pte(dst, pte);
74 }
75 spin_unlock(&mm->page_table_lock);
76 return error;
77 }
78
79 static int move_one_page(struct mm_struct *mm, unsigned long old_addr, unsigned long new_addr)
80 {
81 int error = 0;
82 pte_t * src;
83
84 src = get_one_pte(mm, old_addr);
85 if (src)
86 error = copy_one_pte(mm, src, alloc_one_pte(mm, new_addr));
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 flush_tlb_range(mm, new_addr, new_addr + len);
123 return -1;
124 }
125
126 static inline unsigned long move_vma(struct vm_area_struct * vma,
127 unsigned long addr, unsigned long old_len, unsigned long new_len,
128 unsigned long new_addr)
129 {
130 struct vm_area_struct * new_vma;
131
132 new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
133 if (new_vma) {
134 if (!move_page_tables(current->mm, new_addr, addr, old_len)) {
135 *new_vma = *vma;
136 new_vma->vm_start = new_addr;
137 new_vma->vm_end = new_addr+new_len;
138 new_vma->vm_pgoff += (addr - vma->vm_start) >> PAGE_SHIFT;
139 new_vma->vm_raend = 0;
140 if (new_vma->vm_file)
141 get_file(new_vma->vm_file);
142 if (new_vma->vm_ops && new_vma->vm_ops->open)
143 new_vma->vm_ops->open(new_vma);
144 insert_vm_struct(current->mm, new_vma);
145 do_munmap(current->mm, addr, old_len);
146 current->mm->total_vm += new_len >> PAGE_SHIFT;
147 if (new_vma->vm_flags & VM_LOCKED) {
148 current->mm->locked_vm += new_len >> PAGE_SHIFT;
149 make_pages_present(new_vma->vm_start,
150 new_vma->vm_end);
151 }
152 return new_addr;
153 }
154 kmem_cache_free(vm_area_cachep, new_vma);
155 }
156 return -ENOMEM;
157 }
158
159 /*
160 * Expand (or shrink) an existing mapping, potentially moving it at the
161 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
162 *
163 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
164 * This option implies MREMAP_MAYMOVE.
165 */
166 unsigned long do_mremap(unsigned long addr,
167 unsigned long old_len, unsigned long new_len,
168 unsigned long flags, unsigned long new_addr)
169 {
170 struct vm_area_struct *vma;
171 unsigned long ret = -EINVAL;
172
173 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
174 goto out;
175
176 if (addr & ~PAGE_MASK)
177 goto out;
178
179 old_len = PAGE_ALIGN(old_len);
180 new_len = PAGE_ALIGN(new_len);
181
182 /* new_addr is only valid if MREMAP_FIXED is specified */
183 if (flags & MREMAP_FIXED) {
184 if (new_addr & ~PAGE_MASK)
185 goto out;
186 if (!(flags & MREMAP_MAYMOVE))
187 goto out;
188
189 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
190 goto out;
191
192 /* Check if the location we're moving into overlaps the
193 * old location at all, and fail if it does.
194 */
195 if ((new_addr <= addr) && (new_addr+new_len) > addr)
196 goto out;
197
198 if ((addr <= new_addr) && (addr+old_len) > new_addr)
199 goto out;
200
201 do_munmap(current->mm, new_addr, new_len);
202 }
203
204 /*
205 * Always allow a shrinking remap: that just unmaps
206 * the unnecessary pages..
207 */
208 ret = addr;
209 if (old_len >= new_len) {
210 do_munmap(current->mm, addr+new_len, old_len - new_len);
211 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
212 goto out;
213 }
214
215 /*
216 * Ok, we need to grow.. or relocate.
217 */
218 ret = -EFAULT;
219 vma = find_vma(current->mm, addr);
220 if (!vma || vma->vm_start > addr)
221 goto out;
222 /* We can't remap across vm area boundaries */
223 if (old_len > vma->vm_end - addr)
224 goto out;
225 if (vma->vm_flags & VM_DONTEXPAND) {
226 if (new_len > old_len)
227 goto out;
228 }
229 if (vma->vm_flags & VM_LOCKED) {
230 unsigned long locked = current->mm->locked_vm << PAGE_SHIFT;
231 locked += new_len - old_len;
232 ret = -EAGAIN;
233 if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
234 goto out;
235 }
236 ret = -ENOMEM;
237 if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
238 > current->rlim[RLIMIT_AS].rlim_cur)
239 goto out;
240 /* Private writable mapping? Check memory availability.. */
241 if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE &&
242 !(flags & MAP_NORESERVE) &&
243 !vm_enough_memory((new_len - old_len) >> PAGE_SHIFT))
244 goto out;
245
246 /* old_len exactly to the end of the area..
247 * And we're not relocating the area.
248 */
249 if (old_len == vma->vm_end - addr &&
250 !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
251 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
252 unsigned long max_addr = TASK_SIZE;
253 if (vma->vm_next)
254 max_addr = vma->vm_next->vm_start;
255 /* can we just expand the current mapping? */
256 if (max_addr - addr >= new_len) {
257 int pages = (new_len - old_len) >> PAGE_SHIFT;
258 spin_lock(&vma->vm_mm->page_table_lock);
259 vma->vm_end = addr + new_len;
260 spin_unlock(&vma->vm_mm->page_table_lock);
261 current->mm->total_vm += pages;
262 if (vma->vm_flags & VM_LOCKED) {
263 current->mm->locked_vm += pages;
264 make_pages_present(addr + old_len,
265 addr + new_len);
266 }
267 ret = addr;
268 goto out;
269 }
270 }
271
272 /*
273 * We weren't able to just expand or shrink the area,
274 * we need to create a new one and move it..
275 */
276 ret = -ENOMEM;
277 if (flags & MREMAP_MAYMOVE) {
278 if (!(flags & MREMAP_FIXED)) {
279 new_addr = get_unmapped_area(0, new_len);
280 if (!new_addr)
281 goto out;
282 }
283 ret = move_vma(vma, addr, old_len, new_len, new_addr);
284 }
285 out:
286 return ret;
287 }
288
289 asmlinkage unsigned long sys_mremap(unsigned long addr,
290 unsigned long old_len, unsigned long new_len,
291 unsigned long flags, unsigned long new_addr)
292 {
293 unsigned long ret;
294
295 down(¤t->mm->mmap_sem);
296 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
297 up(¤t->mm->mmap_sem);
298 return ret;
299 }
300
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