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 15 #include <asm/uaccess.h> 16 #include <asm/pgtable.h> 17 18 /* 19 * Later we can get more picky about what "in core" means precisely. 20 * For now, simply check to see if the page is in the page cache, 21 * and is up to date; i.e. that no page-in operation would be required 22 * at this time if an application were to map and access this page. 23 */ 24 static unsigned char mincore_page(struct vm_area_struct * vma, 25 unsigned long pgoff) 26 { 27 unsigned char present = 0; 28 struct address_space * as = vma->vm_file->f_mapping; 29 struct page * page; 30 31 page = find_get_page(as, pgoff); 32 if (page) { 33 present = PageUptodate(page); 34 page_cache_release(page); 35 } 36 37 return present; 38 } 39 40 static long mincore_vma(struct vm_area_struct * vma, 41 unsigned long start, unsigned long end, unsigned char __user * vec) 42 { 43 long error, i, remaining; 44 unsigned char * tmp; 45 46 error = -ENOMEM; 47 if (!vma->vm_file) 48 return error; 49 50 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 51 if (end > vma->vm_end) 52 end = vma->vm_end; 53 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 54 55 error = -EAGAIN; 56 tmp = (unsigned char *) __get_free_page(GFP_KERNEL); 57 if (!tmp) 58 return error; 59 60 /* (end - start) is # of pages, and also # of bytes in "vec */ 61 remaining = (end - start), 62 63 error = 0; 64 for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) { 65 int j = 0; 66 long thispiece = (remaining < PAGE_SIZE) ? 67 remaining : PAGE_SIZE; 68 69 while (j < thispiece) 70 tmp[j++] = mincore_page(vma, start++); 71 72 if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) { 73 error = -EFAULT; 74 break; 75 } 76 } 77 78 free_page((unsigned long) tmp); 79 return error; 80 } 81 82 /* 83 * The mincore(2) system call. 84 * 85 * mincore() returns the memory residency status of the pages in the 86 * current process's address space specified by [addr, addr + len). 87 * The status is returned in a vector of bytes. The least significant 88 * bit of each byte is 1 if the referenced page is in memory, otherwise 89 * it is zero. 90 * 91 * Because the status of a page can change after mincore() checks it 92 * but before it returns to the application, the returned vector may 93 * contain stale information. Only locked pages are guaranteed to 94 * remain in memory. 95 * 96 * return values: 97 * zero - success 98 * -EFAULT - vec points to an illegal address 99 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE, 100 * or len has a nonpositive value 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; 112 struct vm_area_struct * vma; 113 int unmapped_error = 0; 114 long error = -EINVAL; 115 116 down_read(¤t->mm->mmap_sem); 117 118 if (start & ~PAGE_CACHE_MASK) 119 goto out; 120 len = (len + ~PAGE_CACHE_MASK) & PAGE_CACHE_MASK; 121 end = start + len; 122 if (end < start) 123 goto out; 124 125 error = -EFAULT; 126 if (!access_ok(VERIFY_WRITE, vec, len >> PAGE_SHIFT)) 127 goto out; 128 129 error = 0; 130 if (end == start) 131 goto out; 132 133 /* 134 * If the interval [start,end) covers some unmapped address 135 * ranges, just ignore them, but return -ENOMEM at the end. 136 */ 137 vma = find_vma(current->mm, start); 138 for (;;) { 139 /* Still start < end. */ 140 error = -ENOMEM; 141 if (!vma) 142 goto out; 143 144 /* Here start < vma->vm_end. */ 145 if (start < vma->vm_start) { 146 unmapped_error = -ENOMEM; 147 start = vma->vm_start; 148 } 149 150 /* Here vma->vm_start <= start < vma->vm_end. */ 151 if (end <= vma->vm_end) { 152 if (start < end) { 153 error = mincore_vma(vma, start, end, 154 &vec[index]); 155 if (error) 156 goto out; 157 } 158 error = unmapped_error; 159 goto out; 160 } 161 162 /* Here vma->vm_start <= start < vma->vm_end < end. */ 163 error = mincore_vma(vma, start, vma->vm_end, &vec[index]); 164 if (error) 165 goto out; 166 index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT; 167 start = vma->vm_end; 168 vma = vma->vm_next; 169 } 170 171 out: 172 up_read(¤t->mm->mmap_sem); 173 return error; 174 } 175
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