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
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/module.h>
17 #include <linux/syscalls.h>
18
19 #include <asm/mmu_context.h>
20 #include <asm/cacheflush.h>
21 #include <asm/tlbflush.h>
22
23 static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
24 unsigned long addr, pte_t *ptep)
25 {
26 pte_t pte = *ptep;
27 struct page *page = NULL;
28
29 if (pte_present(pte)) {
30 flush_cache_page(vma, addr, pte_pfn(pte));
31 pte = ptep_clear_flush(vma, addr, ptep);
32 page = vm_normal_page(vma, addr, pte);
33 if (page) {
34 if (pte_dirty(pte))
35 set_page_dirty(page);
36 page_remove_rmap(page);
37 page_cache_release(page);
38 }
39 } else {
40 if (!pte_file(pte))
41 free_swap_and_cache(pte_to_swp_entry(pte));
42 pte_clear(mm, addr, ptep);
43 }
44 return !!page;
45 }
46
47 /*
48 * Install a file page to a given virtual memory address, release any
49 * previously existing mapping.
50 */
51 int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
52 unsigned long addr, struct page *page, pgprot_t prot)
53 {
54 struct inode *inode;
55 pgoff_t size;
56 int err = -ENOMEM;
57 pte_t *pte;
58 pte_t pte_val;
59 spinlock_t *ptl;
60
61 pte = get_locked_pte(mm, addr, &ptl);
62 if (!pte)
63 goto out;
64
65 /*
66 * This page may have been truncated. Tell the
67 * caller about it.
68 */
69 err = -EINVAL;
70 inode = vma->vm_file->f_mapping->host;
71 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
72 if (!page->mapping || page->index >= size)
73 goto unlock;
74 err = -ENOMEM;
75 if (page_mapcount(page) > INT_MAX/2)
76 goto unlock;
77
78 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
79 inc_mm_counter(mm, file_rss);
80
81 flush_icache_page(vma, page);
82 set_pte_at(mm, addr, pte, mk_pte(page, prot));
83 page_add_file_rmap(page);
84 pte_val = *pte;
85 update_mmu_cache(vma, addr, pte_val);
86 err = 0;
87 unlock:
88 pte_unmap_unlock(pte, ptl);
89 out:
90 return err;
91 }
92 EXPORT_SYMBOL(install_page);
93
94 /*
95 * Install a file pte to a given virtual memory address, release any
96 * previously existing mapping.
97 */
98 int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
99 unsigned long addr, unsigned long pgoff, pgprot_t prot)
100 {
101 int err = -ENOMEM;
102 pte_t *pte;
103 pte_t pte_val;
104 spinlock_t *ptl;
105
106 pte = get_locked_pte(mm, addr, &ptl);
107 if (!pte)
108 goto out;
109
110 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
111 update_hiwater_rss(mm);
112 dec_mm_counter(mm, file_rss);
113 }
114
115 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
116 pte_val = *pte;
117 update_mmu_cache(vma, addr, pte_val);
118 pte_unmap_unlock(pte, ptl);
119 err = 0;
120 out:
121 return err;
122 }
123
124 /***
125 * sys_remap_file_pages - remap arbitrary pages of a shared backing store
126 * file within an existing 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
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 * this syscall works purely via pagetables, so it's the most efficient
134 * way to map the same (large) file into a given virtual window. Unlike
135 * mmap()/mremap() it does not create any new vmas. The new mappings are
136 * also safe across swapout.
137 *
138 * NOTE: the 'prot' parameter right now is ignored, and the vma's default
139 * protection is used. Arbitrary protections might be implemented in the
140 * future.
141 */
142 asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
143 unsigned long __prot, unsigned long pgoff, unsigned long flags)
144 {
145 struct mm_struct *mm = current->mm;
146 struct address_space *mapping;
147 unsigned long end = start + size;
148 struct vm_area_struct *vma;
149 int err = -EINVAL;
150 int has_write_lock = 0;
151
152 if (__prot)
153 return err;
154 /*
155 * Sanitize the syscall parameters:
156 */
157 start = start & PAGE_MASK;
158 size = size & PAGE_MASK;
159
160 /* Does the address range wrap, or is the span zero-sized? */
161 if (start + size <= start)
162 return err;
163
164 /* Can we represent this offset inside this architecture's pte's? */
165 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
166 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
167 return err;
168 #endif
169
170 /* We need down_write() to change vma->vm_flags. */
171 down_read(&mm->mmap_sem);
172 retry:
173 vma = find_vma(mm, start);
174
175 /*
176 * Make sure the vma is shared, that it supports prefaulting,
177 * and that the remapped range is valid and fully within
178 * the single existing vma. vm_private_data is used as a
179 * swapout cursor in a VM_NONLINEAR vma.
180 */
181 if (vma && (vma->vm_flags & VM_SHARED) &&
182 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
183 vma->vm_ops && vma->vm_ops->populate &&
184 end > start && start >= vma->vm_start &&
185 end <= vma->vm_end) {
186
187 /* Must set VM_NONLINEAR before any pages are populated. */
188 if (pgoff != linear_page_index(vma, start) &&
189 !(vma->vm_flags & VM_NONLINEAR)) {
190 if (!has_write_lock) {
191 up_read(&mm->mmap_sem);
192 down_write(&mm->mmap_sem);
193 has_write_lock = 1;
194 goto retry;
195 }
196 mapping = vma->vm_file->f_mapping;
197 spin_lock(&mapping->i_mmap_lock);
198 flush_dcache_mmap_lock(mapping);
199 vma->vm_flags |= VM_NONLINEAR;
200 vma_prio_tree_remove(vma, &mapping->i_mmap);
201 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
202 flush_dcache_mmap_unlock(mapping);
203 spin_unlock(&mapping->i_mmap_lock);
204 }
205
206 err = vma->vm_ops->populate(vma, start, size,
207 vma->vm_page_prot,
208 pgoff, flags & MAP_NONBLOCK);
209
210 /*
211 * We can't clear VM_NONLINEAR because we'd have to do
212 * it after ->populate completes, and that would prevent
213 * downgrading the lock. (Locks can't be upgraded).
214 */
215 }
216 if (likely(!has_write_lock))
217 up_read(&mm->mmap_sem);
218 else
219 up_write(&mm->mmap_sem);
220
221 return err;
222 }
223
224
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