1/* 2 * linux/mm/mincore.c 3 * 4 * Copyright (C) 1994-2006 Linus Torvalds 5 */ 6 7/* 8 * The mincore() system call. 9 */ 10#include <linux/pagemap.h> 11#include <linux/gfp.h> 12#include <linux/mm.h> 13#include <linux/mman.h> 14#include <linux/syscalls.h> 15#include <linux/swap.h> 16#include <linux/swapops.h> 17#include <linux/hugetlb.h> 18 19#include <asm/uaccess.h> 20#include <asm/pgtable.h> 21 22static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, 23 unsigned long end, struct mm_walk *walk) 24{ 25#ifdef CONFIG_HUGETLB_PAGE 26 unsigned char present; 27 unsigned char *vec = walk->private; 28 29 /* 30 * Hugepages under user process are always in RAM and never 31 * swapped out, but theoretically it needs to be checked. 32 */ 33 present = pte && !huge_pte_none(huge_ptep_get(pte)); 34 for (; addr != end; vec++, addr += PAGE_SIZE) 35 *vec = present; 36 walk->private = vec; 37#else 38 BUG(); 39#endif 40 return 0; 41} 42 43/* 44 * Later we can get more picky about what "in core" means precisely. 45 * For now, simply check to see if the page is in the page cache, 46 * and is up to date; i.e. that no page-in operation would be required 47 * at this time if an application were to map and access this page. 48 */ 49static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) 50{ 51 unsigned char present = 0; 52 struct page *page; 53 54 /* 55 * When tmpfs swaps out a page from a file, any process mapping that 56 * file will not get a swp_entry_t in its pte, but rather it is like 57 * any other file mapping (ie. marked !present and faulted in with 58 * tmpfs's .fault). So swapped out tmpfs mappings are tested here. 59 */ 60#ifdef CONFIG_SWAP 61 if (shmem_mapping(mapping)) { 62 page = find_get_entry(mapping, pgoff); 63 /* 64 * shmem/tmpfs may return swap: account for swapcache 65 * page too. 66 */ 67 if (radix_tree_exceptional_entry(page)) { 68 swp_entry_t swp = radix_to_swp_entry(page); 69 page = find_get_page(swap_address_space(swp), swp.val); 70 } 71 } else 72 page = find_get_page(mapping, pgoff); 73#else 74 page = find_get_page(mapping, pgoff); 75#endif 76 if (page) { 77 present = PageUptodate(page); 78 page_cache_release(page); 79 } 80 81 return present; 82} 83 84static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 85 struct vm_area_struct *vma, unsigned char *vec) 86{ 87 unsigned long nr = (end - addr) >> PAGE_SHIFT; 88 int i; 89 90 if (vma->vm_file) { 91 pgoff_t pgoff; 92 93 pgoff = linear_page_index(vma, addr); 94 for (i = 0; i < nr; i++, pgoff++) 95 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 96 } else { 97 for (i = 0; i < nr; i++) 98 vec[i] = 0; 99 } 100 return nr; 101} 102 103static int mincore_unmapped_range(unsigned long addr, unsigned long end, 104 struct mm_walk *walk) 105{ 106 walk->private += __mincore_unmapped_range(addr, end, 107 walk->vma, walk->private); 108 return 0; 109} 110 111static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 112 struct mm_walk *walk) 113{ 114 spinlock_t *ptl; 115 struct vm_area_struct *vma = walk->vma; 116 pte_t *ptep; 117 unsigned char *vec = walk->private; 118 int nr = (end - addr) >> PAGE_SHIFT; 119 120 if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 121 memset(vec, 1, nr); 122 spin_unlock(ptl); 123 goto out; 124 } 125 126 if (pmd_trans_unstable(pmd)) { 127 __mincore_unmapped_range(addr, end, vma, vec); 128 goto out; 129 } 130 131 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 132 for (; addr != end; ptep++, addr += PAGE_SIZE) { 133 pte_t pte = *ptep; 134 135 if (pte_none(pte)) 136 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 137 vma, vec); 138 else if (pte_present(pte)) 139 *vec = 1; 140 else { /* pte is a swap entry */ 141 swp_entry_t entry = pte_to_swp_entry(pte); 142 143 if (non_swap_entry(entry)) { 144 /* 145 * migration or hwpoison entries are always 146 * uptodate 147 */ 148 *vec = 1; 149 } else { 150#ifdef CONFIG_SWAP 151 *vec = mincore_page(swap_address_space(entry), 152 entry.val); 153#else 154 WARN_ON(1); 155 *vec = 1; 156#endif 157 } 158 } 159 vec++; 160 } 161 pte_unmap_unlock(ptep - 1, ptl); 162out: 163 walk->private += nr; 164 cond_resched(); 165 return 0; 166} 167 168/* 169 * Do a chunk of "sys_mincore()". We've already checked 170 * all the arguments, we hold the mmap semaphore: we should 171 * just return the amount of info we're asked for. 172 */ 173static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 174{ 175 struct vm_area_struct *vma; 176 unsigned long end; 177 int err; 178 struct mm_walk mincore_walk = { 179 .pmd_entry = mincore_pte_range, 180 .pte_hole = mincore_unmapped_range, 181 .hugetlb_entry = mincore_hugetlb, 182 .private = vec, 183 }; 184 185 vma = find_vma(current->mm, addr); 186 if (!vma || addr < vma->vm_start) 187 return -ENOMEM; 188 mincore_walk.mm = vma->vm_mm; 189 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 190 err = walk_page_range(addr, end, &mincore_walk); 191 if (err < 0) 192 return err; 193 return (end - addr) >> PAGE_SHIFT; 194} 195 196/* 197 * The mincore(2) system call. 198 * 199 * mincore() returns the memory residency status of the pages in the 200 * current process's address space specified by [addr, addr + len). 201 * The status is returned in a vector of bytes. The least significant 202 * bit of each byte is 1 if the referenced page is in memory, otherwise 203 * it is zero. 204 * 205 * Because the status of a page can change after mincore() checks it 206 * but before it returns to the application, the returned vector may 207 * contain stale information. Only locked pages are guaranteed to 208 * remain in memory. 209 * 210 * return values: 211 * zero - success 212 * -EFAULT - vec points to an illegal address 213 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE 214 * -ENOMEM - Addresses in the range [addr, addr + len] are 215 * invalid for the address space of this process, or 216 * specify one or more pages which are not currently 217 * mapped 218 * -EAGAIN - A kernel resource was temporarily unavailable. 219 */ 220SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 221 unsigned char __user *, vec) 222{ 223 long retval; 224 unsigned long pages; 225 unsigned char *tmp; 226 227 /* Check the start address: needs to be page-aligned.. */ 228 if (start & ~PAGE_CACHE_MASK) 229 return -EINVAL; 230 231 /* ..and we need to be passed a valid user-space range */ 232 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 233 return -ENOMEM; 234 235 /* This also avoids any overflows on PAGE_CACHE_ALIGN */ 236 pages = len >> PAGE_SHIFT; 237 pages += (len & ~PAGE_MASK) != 0; 238 239 if (!access_ok(VERIFY_WRITE, vec, pages)) 240 return -EFAULT; 241 242 tmp = (void *) __get_free_page(GFP_USER); 243 if (!tmp) 244 return -EAGAIN; 245 246 retval = 0; 247 while (pages) { 248 /* 249 * Do at most PAGE_SIZE entries per iteration, due to 250 * the temporary buffer size. 251 */ 252 down_read(¤t->mm->mmap_sem); 253 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 254 up_read(¤t->mm->mmap_sem); 255 256 if (retval <= 0) 257 break; 258 if (copy_to_user(vec, tmp, retval)) { 259 retval = -EFAULT; 260 break; 261 } 262 pages -= retval; 263 vec += retval; 264 start += retval << PAGE_SHIFT; 265 retval = 0; 266 } 267 free_page((unsigned long) tmp); 268 return retval; 269} 270