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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 | /* * linux/mm/mprotect.c * * (C) Copyright 1994 Linus Torvalds */ #include <linux/stat.h> #include <linux/sched.h> #include <linux/kernel.h> #include <linux/mm.h> #include <linux/shm.h> #include <linux/errno.h> #include <linux/mman.h> #include <linux/string.h> #include <linux/malloc.h> #include <asm/segment.h> #include <asm/system.h> static void change_protection(unsigned long start, unsigned long end, int prot) { unsigned long *page_table, *dir; unsigned long page, offset; int nr; dir = PAGE_DIR_OFFSET(current, start); offset = (start >> PAGE_SHIFT) & (PTRS_PER_PAGE-1); nr = (end - start) >> PAGE_SHIFT; while (nr > 0) { page = *dir; dir++; if (!(page & PAGE_PRESENT)) { nr = nr - PTRS_PER_PAGE + offset; offset = 0; continue; } page_table = offset + (unsigned long *) (page & PAGE_MASK); offset = PTRS_PER_PAGE - offset; if (offset > nr) offset = nr; nr = nr - offset; do { page = *page_table; if (page & PAGE_PRESENT) *page_table = (page & PAGE_CHG_MASK) | prot; ++page_table; } while (--offset); } return; } static inline int mprotect_fixup_all(struct vm_area_struct * vma, int newflags, int prot) { vma->vm_flags = newflags; vma->vm_page_prot = prot; return 0; } static inline int mprotect_fixup_start(struct vm_area_struct * vma, unsigned long end, int newflags, int prot) { struct vm_area_struct * n; n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); if (!n) return -ENOMEM; *n = *vma; vma->vm_start = end; n->vm_end = end; vma->vm_offset += vma->vm_start - n->vm_start; n->vm_flags = newflags; n->vm_page_prot = prot; if (n->vm_inode) n->vm_inode->i_count++; if (n->vm_ops && n->vm_ops->open) n->vm_ops->open(n); insert_vm_struct(current, n); return 0; } static inline int mprotect_fixup_end(struct vm_area_struct * vma, unsigned long start, int newflags, int prot) { struct vm_area_struct * n; n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); if (!n) return -ENOMEM; *n = *vma; vma->vm_end = start; n->vm_start = start; n->vm_offset += n->vm_start - vma->vm_start; n->vm_flags = newflags; n->vm_page_prot = prot; if (n->vm_inode) n->vm_inode->i_count++; if (n->vm_ops && n->vm_ops->open) n->vm_ops->open(n); insert_vm_struct(current, n); return 0; } static inline int mprotect_fixup_middle(struct vm_area_struct * vma, unsigned long start, unsigned long end, int newflags, int prot) { struct vm_area_struct * left, * right; left = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); if (!left) return -ENOMEM; right = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); if (!right) { kfree(left); return -ENOMEM; } *left = *vma; *right = *vma; left->vm_end = start; vma->vm_start = start; vma->vm_end = end; right->vm_start = end; vma->vm_offset += vma->vm_start - left->vm_start; right->vm_offset += right->vm_start - left->vm_start; vma->vm_flags = newflags; vma->vm_page_prot = prot; if (vma->vm_inode) vma->vm_inode->i_count += 2; if (vma->vm_ops && vma->vm_ops->open) { vma->vm_ops->open(left); vma->vm_ops->open(right); } insert_vm_struct(current, left); insert_vm_struct(current, right); return 0; } static int mprotect_fixup(struct vm_area_struct * vma, unsigned long start, unsigned long end, unsigned int newflags) { int prot, error; if (newflags == vma->vm_flags) return 0; prot = PAGE_PRESENT; if (newflags & (VM_READ | VM_EXEC)) prot |= PAGE_READONLY; if (newflags & VM_WRITE) if (newflags & VM_SHARED) prot |= PAGE_SHARED; else prot |= PAGE_COPY; if (start == vma->vm_start) if (end == vma->vm_end) error = mprotect_fixup_all(vma, newflags, prot); else error = mprotect_fixup_start(vma, end, newflags, prot); else if (end == vma->vm_end) error = mprotect_fixup_end(vma, start, newflags, prot); else error = mprotect_fixup_middle(vma, start, end, newflags, prot); if (error) return error; change_protection(start, end, prot); return 0; } asmlinkage int sys_mprotect(unsigned long start, size_t len, unsigned long prot) { unsigned long end, tmp; struct vm_area_struct * vma, * next; int error; if (start & ~PAGE_MASK) return -EINVAL; len = (len + ~PAGE_MASK) & PAGE_MASK; end = start + len; if (end < start) return -EINVAL; if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)) return -EINVAL; if (end == start) return 0; for (vma = current->mm->mmap ; ; vma = vma->vm_next) { if (!vma) return -EFAULT; if (vma->vm_end > start) break; } if (vma->vm_start > start) return -EFAULT; for ( ; ; ) { unsigned int newflags; /* Here we know that vma->vm_start <= start < vma->vm_end. */ newflags = prot | (vma->vm_flags & ~(PROT_READ | PROT_WRITE | PROT_EXEC)); if ((newflags & ~(newflags >> 4)) & 0xf) { error = -EACCES; break; } if (vma->vm_end >= end) { error = mprotect_fixup(vma, start, end, newflags); break; } tmp = vma->vm_end; next = vma->vm_next; error = mprotect_fixup(vma, start, tmp, newflags); if (error) break; start = tmp; vma = next; if (!vma || vma->vm_start != start) { error = -EFAULT; break; } } merge_segments(current->mm->mmap); return error; } |