mremap.c revision c74df32c724a1652ad8399b4891bb02c9d43743a 
1/*
2 *	mm/mremap.c
3 *
4 *	(C) Copyright 1996 Linus Torvalds
5 *
6 *	Address space accounting code	<alan@redhat.com>
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/fs.h>
17#include <linux/highmem.h>
18#include <linux/security.h>
19#include <linux/syscalls.h>
20
21#include <asm/uaccess.h>
22#include <asm/cacheflush.h>
23#include <asm/tlbflush.h>
24
25static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
26{
27	pgd_t *pgd;
28	pud_t *pud;
29	pmd_t *pmd;
30
31	pgd = pgd_offset(mm, addr);
32	if (pgd_none_or_clear_bad(pgd))
33		return NULL;
34
35	pud = pud_offset(pgd, addr);
36	if (pud_none_or_clear_bad(pud))
37		return NULL;
38
39	pmd = pmd_offset(pud, addr);
40	if (pmd_none_or_clear_bad(pmd))
41		return NULL;
42
43	return pmd;
44}
45
46static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
47{
48	pgd_t *pgd;
49	pud_t *pud;
50	pmd_t *pmd;
51
52	pgd = pgd_offset(mm, addr);
53	pud = pud_alloc(mm, pgd, addr);
54	if (!pud)
55		return NULL;
56
57	pmd = pmd_alloc(mm, pud, addr);
58	if (!pmd)
59		return NULL;
60
61	if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
62		return NULL;
63
64	return pmd;
65}
66
67static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
68		unsigned long old_addr, unsigned long old_end,
69		struct vm_area_struct *new_vma, pmd_t *new_pmd,
70		unsigned long new_addr)
71{
72	struct address_space *mapping = NULL;
73	struct mm_struct *mm = vma->vm_mm;
74	pte_t *old_pte, *new_pte, pte;
75	spinlock_t *old_ptl;
76
77	if (vma->vm_file) {
78		/*
79		 * Subtle point from Rajesh Venkatasubramanian: before
80		 * moving file-based ptes, we must lock vmtruncate out,
81		 * since it might clean the dst vma before the src vma,
82		 * and we propagate stale pages into the dst afterward.
83		 */
84		mapping = vma->vm_file->f_mapping;
85		spin_lock(&mapping->i_mmap_lock);
86		if (new_vma->vm_truncate_count &&
87		    new_vma->vm_truncate_count != vma->vm_truncate_count)
88			new_vma->vm_truncate_count = 0;
89	}
90
91	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
92 	new_pte = pte_offset_map_nested(new_pmd, new_addr);
93
94	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
95				   new_pte++, new_addr += PAGE_SIZE) {
96		if (pte_none(*old_pte))
97			continue;
98		pte = ptep_clear_flush(vma, old_addr, old_pte);
99		/* ZERO_PAGE can be dependant on virtual addr */
100		pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
101		set_pte_at(mm, new_addr, new_pte, pte);
102	}
103
104	pte_unmap_nested(new_pte - 1);
105	pte_unmap_unlock(old_pte - 1, old_ptl);
106	if (mapping)
107		spin_unlock(&mapping->i_mmap_lock);
108}
109
110#define LATENCY_LIMIT	(64 * PAGE_SIZE)
111
112static unsigned long move_page_tables(struct vm_area_struct *vma,
113		unsigned long old_addr, struct vm_area_struct *new_vma,
114		unsigned long new_addr, unsigned long len)
115{
116	unsigned long extent, next, old_end;
117	pmd_t *old_pmd, *new_pmd;
118
119	old_end = old_addr + len;
120	flush_cache_range(vma, old_addr, old_end);
121
122	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
123		cond_resched();
124		next = (old_addr + PMD_SIZE) & PMD_MASK;
125		if (next - 1 > old_end)
126			next = old_end;
127		extent = next - old_addr;
128		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
129		if (!old_pmd)
130			continue;
131		new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
132		if (!new_pmd)
133			break;
134		next = (new_addr + PMD_SIZE) & PMD_MASK;
135		if (extent > next - new_addr)
136			extent = next - new_addr;
137		if (extent > LATENCY_LIMIT)
138			extent = LATENCY_LIMIT;
139		move_ptes(vma, old_pmd, old_addr, old_addr + extent,
140				new_vma, new_pmd, new_addr);
141	}
142
143	return len + old_addr - old_end;	/* how much done */
144}
145
146static unsigned long move_vma(struct vm_area_struct *vma,
147		unsigned long old_addr, unsigned long old_len,
148		unsigned long new_len, unsigned long new_addr)
149{
150	struct mm_struct *mm = vma->vm_mm;
151	struct vm_area_struct *new_vma;
152	unsigned long vm_flags = vma->vm_flags;
153	unsigned long new_pgoff;
154	unsigned long moved_len;
155	unsigned long excess = 0;
156	unsigned long hiwater_vm;
157	int split = 0;
158
159	/*
160	 * We'd prefer to avoid failure later on in do_munmap:
161	 * which may split one vma into three before unmapping.
162	 */
163	if (mm->map_count >= sysctl_max_map_count - 3)
164		return -ENOMEM;
165
166	new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
167	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
168	if (!new_vma)
169		return -ENOMEM;
170
171	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
172	if (moved_len < old_len) {
173		/*
174		 * On error, move entries back from new area to old,
175		 * which will succeed since page tables still there,
176		 * and then proceed to unmap new area instead of old.
177		 */
178		move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
179		vma = new_vma;
180		old_len = new_len;
181		old_addr = new_addr;
182		new_addr = -ENOMEM;
183	}
184
185	/* Conceal VM_ACCOUNT so old reservation is not undone */
186	if (vm_flags & VM_ACCOUNT) {
187		vma->vm_flags &= ~VM_ACCOUNT;
188		excess = vma->vm_end - vma->vm_start - old_len;
189		if (old_addr > vma->vm_start &&
190		    old_addr + old_len < vma->vm_end)
191			split = 1;
192	}
193
194	/*
195	 * If we failed to move page tables we still do total_vm increment
196	 * since do_munmap() will decrement it by old_len == new_len.
197	 *
198	 * Since total_vm is about to be raised artificially high for a
199	 * moment, we need to restore high watermark afterwards: if stats
200	 * are taken meanwhile, total_vm and hiwater_vm appear too high.
201	 * If this were a serious issue, we'd add a flag to do_munmap().
202	 */
203	hiwater_vm = mm->hiwater_vm;
204	mm->total_vm += new_len >> PAGE_SHIFT;
205	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
206
207	if (do_munmap(mm, old_addr, old_len) < 0) {
208		/* OOM: unable to split vma, just get accounts right */
209		vm_unacct_memory(excess >> PAGE_SHIFT);
210		excess = 0;
211	}
212	mm->hiwater_vm = hiwater_vm;
213
214	/* Restore VM_ACCOUNT if one or two pieces of vma left */
215	if (excess) {
216		vma->vm_flags |= VM_ACCOUNT;
217		if (split)
218			vma->vm_next->vm_flags |= VM_ACCOUNT;
219	}
220
221	if (vm_flags & VM_LOCKED) {
222		mm->locked_vm += new_len >> PAGE_SHIFT;
223		if (new_len > old_len)
224			make_pages_present(new_addr + old_len,
225					   new_addr + new_len);
226	}
227
228	return new_addr;
229}
230
231/*
232 * Expand (or shrink) an existing mapping, potentially moving it at the
233 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
234 *
235 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
236 * This option implies MREMAP_MAYMOVE.
237 */
238unsigned long do_mremap(unsigned long addr,
239	unsigned long old_len, unsigned long new_len,
240	unsigned long flags, unsigned long new_addr)
241{
242	struct mm_struct *mm = current->mm;
243	struct vm_area_struct *vma;
244	unsigned long ret = -EINVAL;
245	unsigned long charged = 0;
246
247	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
248		goto out;
249
250	if (addr & ~PAGE_MASK)
251		goto out;
252
253	old_len = PAGE_ALIGN(old_len);
254	new_len = PAGE_ALIGN(new_len);
255
256	/*
257	 * We allow a zero old-len as a special case
258	 * for DOS-emu "duplicate shm area" thing. But
259	 * a zero new-len is nonsensical.
260	 */
261	if (!new_len)
262		goto out;
263
264	/* new_addr is only valid if MREMAP_FIXED is specified */
265	if (flags & MREMAP_FIXED) {
266		if (new_addr & ~PAGE_MASK)
267			goto out;
268		if (!(flags & MREMAP_MAYMOVE))
269			goto out;
270
271		if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
272			goto out;
273
274		/* Check if the location we're moving into overlaps the
275		 * old location at all, and fail if it does.
276		 */
277		if ((new_addr <= addr) && (new_addr+new_len) > addr)
278			goto out;
279
280		if ((addr <= new_addr) && (addr+old_len) > new_addr)
281			goto out;
282
283		ret = do_munmap(mm, new_addr, new_len);
284		if (ret)
285			goto out;
286	}
287
288	/*
289	 * Always allow a shrinking remap: that just unmaps
290	 * the unnecessary pages..
291	 * do_munmap does all the needed commit accounting
292	 */
293	if (old_len >= new_len) {
294		ret = do_munmap(mm, addr+new_len, old_len - new_len);
295		if (ret && old_len != new_len)
296			goto out;
297		ret = addr;
298		if (!(flags & MREMAP_FIXED) || (new_addr == addr))
299			goto out;
300		old_len = new_len;
301	}
302
303	/*
304	 * Ok, we need to grow..  or relocate.
305	 */
306	ret = -EFAULT;
307	vma = find_vma(mm, addr);
308	if (!vma || vma->vm_start > addr)
309		goto out;
310	if (is_vm_hugetlb_page(vma)) {
311		ret = -EINVAL;
312		goto out;
313	}
314	/* We can't remap across vm area boundaries */
315	if (old_len > vma->vm_end - addr)
316		goto out;
317	if (vma->vm_flags & VM_DONTEXPAND) {
318		if (new_len > old_len)
319			goto out;
320	}
321	if (vma->vm_flags & VM_LOCKED) {
322		unsigned long locked, lock_limit;
323		locked = mm->locked_vm << PAGE_SHIFT;
324		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
325		locked += new_len - old_len;
326		ret = -EAGAIN;
327		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
328			goto out;
329	}
330	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
331		ret = -ENOMEM;
332		goto out;
333	}
334
335	if (vma->vm_flags & VM_ACCOUNT) {
336		charged = (new_len - old_len) >> PAGE_SHIFT;
337		if (security_vm_enough_memory(charged))
338			goto out_nc;
339	}
340
341	/* old_len exactly to the end of the area..
342	 * And we're not relocating the area.
343	 */
344	if (old_len == vma->vm_end - addr &&
345	    !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
346	    (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
347		unsigned long max_addr = TASK_SIZE;
348		if (vma->vm_next)
349			max_addr = vma->vm_next->vm_start;
350		/* can we just expand the current mapping? */
351		if (max_addr - addr >= new_len) {
352			int pages = (new_len - old_len) >> PAGE_SHIFT;
353
354			vma_adjust(vma, vma->vm_start,
355				addr + new_len, vma->vm_pgoff, NULL);
356
357			mm->total_vm += pages;
358			vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
359			if (vma->vm_flags & VM_LOCKED) {
360				mm->locked_vm += pages;
361				make_pages_present(addr + old_len,
362						   addr + new_len);
363			}
364			ret = addr;
365			goto out;
366		}
367	}
368
369	/*
370	 * We weren't able to just expand or shrink the area,
371	 * we need to create a new one and move it..
372	 */
373	ret = -ENOMEM;
374	if (flags & MREMAP_MAYMOVE) {
375		if (!(flags & MREMAP_FIXED)) {
376			unsigned long map_flags = 0;
377			if (vma->vm_flags & VM_MAYSHARE)
378				map_flags |= MAP_SHARED;
379
380			new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
381						vma->vm_pgoff, map_flags);
382			ret = new_addr;
383			if (new_addr & ~PAGE_MASK)
384				goto out;
385		}
386		ret = move_vma(vma, addr, old_len, new_len, new_addr);
387	}
388out:
389	if (ret & ~PAGE_MASK)
390		vm_unacct_memory(charged);
391out_nc:
392	return ret;
393}
394
395asmlinkage unsigned long sys_mremap(unsigned long addr,
396	unsigned long old_len, unsigned long new_len,
397	unsigned long flags, unsigned long new_addr)
398{
399	unsigned long ret;
400
401	down_write(&current->mm->mmap_sem);
402	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
403	up_write(&current->mm->mmap_sem);
404	return ret;
405}
406