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