1 /* 2 * linux/mm/mincore.c 3 * 4 * Copyright (C) 1994-1999 Linus Torvalds 5 */ 6 7 /* 8 * The mincore() system call. 9 */ 10 #include <linux/slab.h> 11 #include <linux/pagemap.h> 12 #include <linux/mm.h> 13 #include <linux/mman.h> 14 #include <linux/syscalls.h> 15 16 #include <asm/uaccess.h> 17 #include <asm/pgtable.h> 18 19 /* 20 * Later we can get more picky about what "in core" means precisely. 21 * For now, simply check to see if the page is in the page cache, 22 * and is up to date; i.e. that no page-in operation would be required 23 * at this time if an application were to map and access this page. 24 */ 25 static unsigned char mincore_page(struct vm_area_struct * vma, 26 unsigned long pgoff) 27 { 28 unsigned char present = 0; 29 struct address_space * as = vma->vm_file->f_mapping; 30 struct page * page; 31 32 page = find_get_page(as, pgoff); 33 if (page) { 34 present = PageUptodate(page); 35 page_cache_release(page); 36 } 37 38 return present; 39 } 40 41 static long mincore_vma(struct vm_area_struct * vma, 42 unsigned long start, unsigned long end, unsigned char __user * vec) 43 { 44 long error, i, remaining; 45 unsigned char * tmp; 46 47 error = -ENOMEM; 48 if (!vma->vm_file) 49 return error; 50 51 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 52 if (end > vma->vm_end) 53 end = vma->vm_end; 54 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 55 56 error = -EAGAIN; 57 tmp = (unsigned char *) __get_free_page(GFP_KERNEL); 58 if (!tmp) 59 return error; 60 61 /* (end - start) is # of pages, and also # of bytes in "vec */ 62 remaining = (end - start), 63 64 error = 0; 65 for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) { 66 int j = 0; 67 long thispiece = (remaining < PAGE_SIZE) ? 68 remaining : PAGE_SIZE; 69 70 while (j < thispiece) 71 tmp[j++] = mincore_page(vma, start++); 72 73 if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) { 74 error = -EFAULT; 75 break; 76 } 77 } 78 79 free_page((unsigned long) tmp); 80 return error; 81 } 82 83 /* 84 * The mincore(2) system call. 85 * 86 * mincore() returns the memory residency status of the pages in the 87 * current process's address space specified by [addr, addr + len). 88 * The status is returned in a vector of bytes. The least significant 89 * bit of each byte is 1 if the referenced page is in memory, otherwise 90 * it is zero. 91 * 92 * Because the status of a page can change after mincore() checks it 93 * but before it returns to the application, the returned vector may 94 * contain stale information. Only locked pages are guaranteed to 95 * remain in memory. 96 * 97 * return values: 98 * zero - success 99 * -EFAULT - vec points to an illegal address 100 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE 101 * -ENOMEM - Addresses in the range [addr, addr + len] are 102 * invalid for the address space of this process, or 103 * specify one or more pages which are not currently 104 * mapped 105 * -EAGAIN - A kernel resource was temporarily unavailable. 106 */ 107 asmlinkage long sys_mincore(unsigned long start, size_t len, 108 unsigned char __user * vec) 109 { 110 int index = 0; 111 unsigned long end, limit; 112 struct vm_area_struct * vma; 113 size_t max; 114 int unmapped_error = 0; 115 long error; 116 117 /* check the arguments */ 118 if (start & ~PAGE_CACHE_MASK) 119 goto einval; 120 121 limit = TASK_SIZE; 122 if (start >= limit) 123 goto enomem; 124 125 if (!len) 126 return 0; 127 128 max = limit - start; 129 len = PAGE_CACHE_ALIGN(len); 130 if (len > max || !len) 131 goto enomem; 132 133 end = start + len; 134 135 /* check the output buffer whilst holding the lock */ 136 error = -EFAULT; 137 down_read(¤t->mm->mmap_sem); 138 139 if (!access_ok(VERIFY_WRITE, vec, len >> PAGE_SHIFT)) 140 goto out; 141 142 /* 143 * If the interval [start,end) covers some unmapped address 144 * ranges, just ignore them, but return -ENOMEM at the end. 145 */ 146 error = 0; 147 148 vma = find_vma(current->mm, start); 149 while (vma) { 150 /* Here start < vma->vm_end. */ 151 if (start < vma->vm_start) { 152 unmapped_error = -ENOMEM; 153 start = vma->vm_start; 154 } 155 156 /* Here vma->vm_start <= start < vma->vm_end. */ 157 if (end <= vma->vm_end) { 158 if (start < end) { 159 error = mincore_vma(vma, start, end, 160 &vec[index]); 161 if (error) 162 goto out; 163 } 164 error = unmapped_error; 165 goto out; 166 } 167 168 /* Here vma->vm_start <= start < vma->vm_end < end. */ 169 error = mincore_vma(vma, start, vma->vm_end, &vec[index]); 170 if (error) 171 goto out; 172 index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT; 173 start = vma->vm_end; 174 vma = vma->vm_next; 175 } 176 177 /* we found a hole in the area queried if we arrive here */ 178 error = -ENOMEM; 179 180 out: 181 up_read(¤t->mm->mmap_sem); 182 return error; 183 184 einval: 185 return -EINVAL; 186 enomem: 187 return -ENOMEM; 188 } 189