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1/*
2 * linux/mm/fremap.c
3 *
4 * Explicit pagetable population and nonlinear (random) mappings support.
5 *
6 * started by Ingo Molnar, Copyright (C) 2002, 2003
7 */
8#include <linux/export.h>
9#include <linux/backing-dev.h>
10#include <linux/mm.h>
11#include <linux/swap.h>
12#include <linux/file.h>
13#include <linux/mman.h>
14#include <linux/pagemap.h>
15#include <linux/swapops.h>
16#include <linux/rmap.h>
17#include <linux/syscalls.h>
18#include <linux/mmu_notifier.h>
19
20#include <asm/mmu_context.h>
21#include <asm/cacheflush.h>
22#include <asm/tlbflush.h>
23
24#include "internal.h"
25
26static int mm_counter(struct page *page)
27{
28 return PageAnon(page) ? MM_ANONPAGES : MM_FILEPAGES;
29}
30
31static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
32 unsigned long addr, pte_t *ptep)
33{
34 pte_t pte = *ptep;
35 struct page *page;
36 swp_entry_t entry;
37
38 if (pte_present(pte)) {
39 flush_cache_page(vma, addr, pte_pfn(pte));
40 pte = ptep_clear_flush(vma, addr, ptep);
41 page = vm_normal_page(vma, addr, pte);
42 if (page) {
43 if (pte_dirty(pte))
44 set_page_dirty(page);
45 update_hiwater_rss(mm);
46 dec_mm_counter(mm, mm_counter(page));
47 page_remove_rmap(page);
48 page_cache_release(page);
49 }
50 } else { /* zap_pte() is not called when pte_none() */
51 if (!pte_file(pte)) {
52 update_hiwater_rss(mm);
53 entry = pte_to_swp_entry(pte);
54 if (non_swap_entry(entry)) {
55 if (is_migration_entry(entry)) {
56 page = migration_entry_to_page(entry);
57 dec_mm_counter(mm, mm_counter(page));
58 }
59 } else {
60 free_swap_and_cache(entry);
61 dec_mm_counter(mm, MM_SWAPENTS);
62 }
63 }
64 pte_clear_not_present_full(mm, addr, ptep, 0);
65 }
66}
67
68/*
69 * Install a file pte to a given virtual memory address, release any
70 * previously existing mapping.
71 */
72static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
73 unsigned long addr, unsigned long pgoff, pgprot_t prot)
74{
75 int err = -ENOMEM;
76 pte_t *pte, ptfile;
77 spinlock_t *ptl;
78
79 pte = get_locked_pte(mm, addr, &ptl);
80 if (!pte)
81 goto out;
82
83 ptfile = pgoff_to_pte(pgoff);
84
85 if (!pte_none(*pte)) {
86 if (pte_present(*pte) && pte_soft_dirty(*pte))
87 pte_file_mksoft_dirty(ptfile);
88 zap_pte(mm, vma, addr, pte);
89 }
90
91 set_pte_at(mm, addr, pte, ptfile);
92 /*
93 * We don't need to run update_mmu_cache() here because the "file pte"
94 * being installed by install_file_pte() is not a real pte - it's a
95 * non-present entry (like a swap entry), noting what file offset should
96 * be mapped there when there's a fault (in a non-linear vma where
97 * that's not obvious).
98 */
99 pte_unmap_unlock(pte, ptl);
100 err = 0;
101out:
102 return err;
103}
104
105int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr,
106 unsigned long size, pgoff_t pgoff)
107{
108 struct mm_struct *mm = vma->vm_mm;
109 int err;
110
111 do {
112 err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
113 if (err)
114 return err;
115
116 size -= PAGE_SIZE;
117 addr += PAGE_SIZE;
118 pgoff++;
119 } while (size);
120
121 return 0;
122}
123EXPORT_SYMBOL(generic_file_remap_pages);
124
125/**
126 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
127 * @start: start of the remapped virtual memory range
128 * @size: size of the remapped virtual memory range
129 * @prot: new protection bits of the range (see NOTE)
130 * @pgoff: to-be-mapped page of the backing store file
131 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
132 *
133 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
134 * (shared backing store file).
135 *
136 * This syscall works purely via pagetables, so it's the most efficient
137 * way to map the same (large) file into a given virtual window. Unlike
138 * mmap()/mremap() it does not create any new vmas. The new mappings are
139 * also safe across swapout.
140 *
141 * NOTE: the @prot parameter right now is ignored (but must be zero),
142 * and the vma's default protection is used. Arbitrary protections
143 * might be implemented in the future.
144 */
145SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
146 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
147{
148 struct mm_struct *mm = current->mm;
149 struct address_space *mapping;
150 struct vm_area_struct *vma;
151 int err = -EINVAL;
152 int has_write_lock = 0;
153 vm_flags_t vm_flags = 0;
154
155 if (prot)
156 return err;
157 /*
158 * Sanitize the syscall parameters:
159 */
160 start = start & PAGE_MASK;
161 size = size & PAGE_MASK;
162
163 /* Does the address range wrap, or is the span zero-sized? */
164 if (start + size <= start)
165 return err;
166
167 /* Does pgoff wrap? */
168 if (pgoff + (size >> PAGE_SHIFT) < pgoff)
169 return err;
170
171 /* Can we represent this offset inside this architecture's pte's? */
172#if PTE_FILE_MAX_BITS < BITS_PER_LONG
173 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
174 return err;
175#endif
176
177 /* We need down_write() to change vma->vm_flags. */
178 down_read(&mm->mmap_sem);
179 retry:
180 vma = find_vma(mm, start);
181
182 /*
183 * Make sure the vma is shared, that it supports prefaulting,
184 * and that the remapped range is valid and fully within
185 * the single existing vma.
186 */
187 if (!vma || !(vma->vm_flags & VM_SHARED))
188 goto out;
189
190 if (!vma->vm_ops || !vma->vm_ops->remap_pages)
191 goto out;
192
193 if (start < vma->vm_start || start + size > vma->vm_end)
194 goto out;
195
196 /* Must set VM_NONLINEAR before any pages are populated. */
197 if (!(vma->vm_flags & VM_NONLINEAR)) {
198 /*
199 * vm_private_data is used as a swapout cursor
200 * in a VM_NONLINEAR vma.
201 */
202 if (vma->vm_private_data)
203 goto out;
204
205 /* Don't need a nonlinear mapping, exit success */
206 if (pgoff == linear_page_index(vma, start)) {
207 err = 0;
208 goto out;
209 }
210
211 if (!has_write_lock) {
212get_write_lock:
213 up_read(&mm->mmap_sem);
214 down_write(&mm->mmap_sem);
215 has_write_lock = 1;
216 goto retry;
217 }
218 mapping = vma->vm_file->f_mapping;
219 /*
220 * page_mkclean doesn't work on nonlinear vmas, so if
221 * dirty pages need to be accounted, emulate with linear
222 * vmas.
223 */
224 if (mapping_cap_account_dirty(mapping)) {
225 unsigned long addr;
226 struct file *file = get_file(vma->vm_file);
227 /* mmap_region may free vma; grab the info now */
228 vm_flags = vma->vm_flags;
229
230 addr = mmap_region(file, start, size, vm_flags, pgoff);
231 fput(file);
232 if (IS_ERR_VALUE(addr)) {
233 err = addr;
234 } else {
235 BUG_ON(addr != start);
236 err = 0;
237 }
238 goto out_freed;
239 }
240 mutex_lock(&mapping->i_mmap_mutex);
241 flush_dcache_mmap_lock(mapping);
242 vma->vm_flags |= VM_NONLINEAR;
243 vma_interval_tree_remove(vma, &mapping->i_mmap);
244 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
245 flush_dcache_mmap_unlock(mapping);
246 mutex_unlock(&mapping->i_mmap_mutex);
247 }
248
249 if (vma->vm_flags & VM_LOCKED) {
250 /*
251 * drop PG_Mlocked flag for over-mapped range
252 */
253 if (!has_write_lock)
254 goto get_write_lock;
255 vm_flags = vma->vm_flags;
256 munlock_vma_pages_range(vma, start, start + size);
257 vma->vm_flags = vm_flags;
258 }
259
260 mmu_notifier_invalidate_range_start(mm, start, start + size);
261 err = vma->vm_ops->remap_pages(vma, start, size, pgoff);
262 mmu_notifier_invalidate_range_end(mm, start, start + size);
263
264 /*
265 * We can't clear VM_NONLINEAR because we'd have to do
266 * it after ->populate completes, and that would prevent
267 * downgrading the lock. (Locks can't be upgraded).
268 */
269
270out:
271 if (vma)
272 vm_flags = vma->vm_flags;
273out_freed:
274 if (likely(!has_write_lock))
275 up_read(&mm->mmap_sem);
276 else
277 up_write(&mm->mmap_sem);
278 if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK)))
279 mm_populate(start, size);
280
281 return err;
282}
1/*
2 * linux/mm/fremap.c
3 *
4 * Explicit pagetable population and nonlinear (random) mappings support.
5 *
6 * started by Ingo Molnar, Copyright (C) 2002, 2003
7 */
8#include <linux/backing-dev.h>
9#include <linux/mm.h>
10#include <linux/swap.h>
11#include <linux/file.h>
12#include <linux/mman.h>
13#include <linux/pagemap.h>
14#include <linux/swapops.h>
15#include <linux/rmap.h>
16#include <linux/syscalls.h>
17#include <linux/mmu_notifier.h>
18
19#include <asm/mmu_context.h>
20#include <asm/cacheflush.h>
21#include <asm/tlbflush.h>
22
23#include "internal.h"
24
25static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
26 unsigned long addr, pte_t *ptep)
27{
28 pte_t pte = *ptep;
29
30 if (pte_present(pte)) {
31 struct page *page;
32
33 flush_cache_page(vma, addr, pte_pfn(pte));
34 pte = ptep_clear_flush(vma, addr, ptep);
35 page = vm_normal_page(vma, addr, pte);
36 if (page) {
37 if (pte_dirty(pte))
38 set_page_dirty(page);
39 page_remove_rmap(page);
40 page_cache_release(page);
41 update_hiwater_rss(mm);
42 dec_mm_counter(mm, MM_FILEPAGES);
43 }
44 } else {
45 if (!pte_file(pte))
46 free_swap_and_cache(pte_to_swp_entry(pte));
47 pte_clear_not_present_full(mm, addr, ptep, 0);
48 }
49}
50
51/*
52 * Install a file pte to a given virtual memory address, release any
53 * previously existing mapping.
54 */
55static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
56 unsigned long addr, unsigned long pgoff, pgprot_t prot)
57{
58 int err = -ENOMEM;
59 pte_t *pte;
60 spinlock_t *ptl;
61
62 pte = get_locked_pte(mm, addr, &ptl);
63 if (!pte)
64 goto out;
65
66 if (!pte_none(*pte))
67 zap_pte(mm, vma, addr, pte);
68
69 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
70 /*
71 * We don't need to run update_mmu_cache() here because the "file pte"
72 * being installed by install_file_pte() is not a real pte - it's a
73 * non-present entry (like a swap entry), noting what file offset should
74 * be mapped there when there's a fault (in a non-linear vma where
75 * that's not obvious).
76 */
77 pte_unmap_unlock(pte, ptl);
78 err = 0;
79out:
80 return err;
81}
82
83static int populate_range(struct mm_struct *mm, struct vm_area_struct *vma,
84 unsigned long addr, unsigned long size, pgoff_t pgoff)
85{
86 int err;
87
88 do {
89 err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
90 if (err)
91 return err;
92
93 size -= PAGE_SIZE;
94 addr += PAGE_SIZE;
95 pgoff++;
96 } while (size);
97
98 return 0;
99
100}
101
102/**
103 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
104 * @start: start of the remapped virtual memory range
105 * @size: size of the remapped virtual memory range
106 * @prot: new protection bits of the range (see NOTE)
107 * @pgoff: to-be-mapped page of the backing store file
108 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
109 *
110 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
111 * (shared backing store file).
112 *
113 * This syscall works purely via pagetables, so it's the most efficient
114 * way to map the same (large) file into a given virtual window. Unlike
115 * mmap()/mremap() it does not create any new vmas. The new mappings are
116 * also safe across swapout.
117 *
118 * NOTE: the @prot parameter right now is ignored (but must be zero),
119 * and the vma's default protection is used. Arbitrary protections
120 * might be implemented in the future.
121 */
122SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
123 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
124{
125 struct mm_struct *mm = current->mm;
126 struct address_space *mapping;
127 struct vm_area_struct *vma;
128 int err = -EINVAL;
129 int has_write_lock = 0;
130
131 if (prot)
132 return err;
133 /*
134 * Sanitize the syscall parameters:
135 */
136 start = start & PAGE_MASK;
137 size = size & PAGE_MASK;
138
139 /* Does the address range wrap, or is the span zero-sized? */
140 if (start + size <= start)
141 return err;
142
143 /* Does pgoff wrap? */
144 if (pgoff + (size >> PAGE_SHIFT) < pgoff)
145 return err;
146
147 /* Can we represent this offset inside this architecture's pte's? */
148#if PTE_FILE_MAX_BITS < BITS_PER_LONG
149 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
150 return err;
151#endif
152
153 /* We need down_write() to change vma->vm_flags. */
154 down_read(&mm->mmap_sem);
155 retry:
156 vma = find_vma(mm, start);
157
158 /*
159 * Make sure the vma is shared, that it supports prefaulting,
160 * and that the remapped range is valid and fully within
161 * the single existing vma. vm_private_data is used as a
162 * swapout cursor in a VM_NONLINEAR vma.
163 */
164 if (!vma || !(vma->vm_flags & VM_SHARED))
165 goto out;
166
167 if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
168 goto out;
169
170 if (!(vma->vm_flags & VM_CAN_NONLINEAR))
171 goto out;
172
173 if (start < vma->vm_start || start + size > vma->vm_end)
174 goto out;
175
176 /* Must set VM_NONLINEAR before any pages are populated. */
177 if (!(vma->vm_flags & VM_NONLINEAR)) {
178 /* Don't need a nonlinear mapping, exit success */
179 if (pgoff == linear_page_index(vma, start)) {
180 err = 0;
181 goto out;
182 }
183
184 if (!has_write_lock) {
185 up_read(&mm->mmap_sem);
186 down_write(&mm->mmap_sem);
187 has_write_lock = 1;
188 goto retry;
189 }
190 mapping = vma->vm_file->f_mapping;
191 /*
192 * page_mkclean doesn't work on nonlinear vmas, so if
193 * dirty pages need to be accounted, emulate with linear
194 * vmas.
195 */
196 if (mapping_cap_account_dirty(mapping)) {
197 unsigned long addr;
198 struct file *file = vma->vm_file;
199
200 flags &= MAP_NONBLOCK;
201 get_file(file);
202 addr = mmap_region(file, start, size,
203 flags, vma->vm_flags, pgoff);
204 fput(file);
205 if (IS_ERR_VALUE(addr)) {
206 err = addr;
207 } else {
208 BUG_ON(addr != start);
209 err = 0;
210 }
211 goto out;
212 }
213 mutex_lock(&mapping->i_mmap_mutex);
214 flush_dcache_mmap_lock(mapping);
215 vma->vm_flags |= VM_NONLINEAR;
216 vma_prio_tree_remove(vma, &mapping->i_mmap);
217 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
218 flush_dcache_mmap_unlock(mapping);
219 mutex_unlock(&mapping->i_mmap_mutex);
220 }
221
222 if (vma->vm_flags & VM_LOCKED) {
223 /*
224 * drop PG_Mlocked flag for over-mapped range
225 */
226 vm_flags_t saved_flags = vma->vm_flags;
227 munlock_vma_pages_range(vma, start, start + size);
228 vma->vm_flags = saved_flags;
229 }
230
231 mmu_notifier_invalidate_range_start(mm, start, start + size);
232 err = populate_range(mm, vma, start, size, pgoff);
233 mmu_notifier_invalidate_range_end(mm, start, start + size);
234 if (!err && !(flags & MAP_NONBLOCK)) {
235 if (vma->vm_flags & VM_LOCKED) {
236 /*
237 * might be mapping previously unmapped range of file
238 */
239 mlock_vma_pages_range(vma, start, start + size);
240 } else {
241 if (unlikely(has_write_lock)) {
242 downgrade_write(&mm->mmap_sem);
243 has_write_lock = 0;
244 }
245 make_pages_present(start, start+size);
246 }
247 }
248
249 /*
250 * We can't clear VM_NONLINEAR because we'd have to do
251 * it after ->populate completes, and that would prevent
252 * downgrading the lock. (Locks can't be upgraded).
253 */
254
255out:
256 if (likely(!has_write_lock))
257 up_read(&mm->mmap_sem);
258 else
259 up_write(&mm->mmap_sem);
260
261 return err;
262}