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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/mm/mincore.c4 *5 * Copyright (C) 1994-2006 Linus Torvalds6 */7 8/*9 * The mincore() system call.10 */11#include <linux/pagemap.h>12#include <linux/gfp.h>13#include <linux/pagewalk.h>14#include <linux/mman.h>15#include <linux/syscalls.h>16#include <linux/swap.h>17#include <linux/swapops.h>18#include <linux/shmem_fs.h>19#include <linux/hugetlb.h>20#include <linux/pgtable.h>21 22#include <linux/uaccess.h>23#include "swap.h"24 25static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,26 unsigned long end, struct mm_walk *walk)27{28#ifdef CONFIG_HUGETLB_PAGE29 unsigned char present;30 unsigned char *vec = walk->private;31 32 /*33 * Hugepages under user process are always in RAM and never34 * swapped out, but theoretically it needs to be checked.35 */36 present = pte && !huge_pte_none_mostly(huge_ptep_get(walk->mm, addr, pte));37 for (; addr != end; vec++, addr += PAGE_SIZE)38 *vec = present;39 walk->private = vec;40#else41 BUG();42#endif43 return 0;44}45 46/*47 * Later we can get more picky about what "in core" means precisely.48 * For now, simply check to see if the page is in the page cache,49 * and is up to date; i.e. that no page-in operation would be required50 * at this time if an application were to map and access this page.51 */52static HWJS_SUSPENDS unsigned char mincore_page(struct address_space *mapping, pgoff_t index)53{54 unsigned char present = 0;55 struct folio *folio;56 57 /*58 * When tmpfs swaps out a page from a file, any process mapping that59 * file will not get a swp_entry_t in its pte, but rather it is like60 * any other file mapping (ie. marked !present and faulted in with61 * tmpfs's .fault). So swapped out tmpfs mappings are tested here.62 */63 folio = filemap_get_incore_folio(mapping, index);64 if (!IS_ERR(folio)) {65 present = folio_test_uptodate(folio);66 folio_put(folio);67 }68 69 return present;70}71 72static HWJS_SUSPENDS int __mincore_unmapped_range(unsigned long addr, unsigned long end,73 struct vm_area_struct *vma, unsigned char *vec)74{75 unsigned long nr = (end - addr) >> PAGE_SHIFT;76 int i;77 78 if (vma->vm_file) {79 pgoff_t pgoff;80 81 pgoff = linear_page_index(vma, addr);82 for (i = 0; i < nr; i++, pgoff++)83 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);84 } else {85 for (i = 0; i < nr; i++)86 vec[i] = 0;87 }88 return nr;89}90 91static HWJS_SUSPENDS int mincore_unmapped_range(unsigned long addr, unsigned long end,92 __always_unused int depth,93 struct mm_walk *walk)94{95 walk->private += __mincore_unmapped_range(addr, end,96 walk->vma, walk->private);97 return 0;98}99 100static HWJS_SUSPENDS int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,101 struct mm_walk *walk)102{103 spinlock_t *ptl;104 struct vm_area_struct *vma = walk->vma;105 pte_t *ptep;106 unsigned char *vec = walk->private;107 int nr = (end - addr) >> PAGE_SHIFT;108 109 ptl = pmd_trans_huge_lock(pmd, vma);110 if (ptl) {111 memset(vec, 1, nr);112 spin_unlock(ptl);113 goto out;114 }115 116 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);117 if (!ptep) {118 walk->action = ACTION_AGAIN;119 return 0;120 }121 for (; addr != end; ptep++, addr += PAGE_SIZE) {122 pte_t pte = ptep_get(ptep);123 124 /* We need to do cache lookup too for pte markers */125 if (pte_none_mostly(pte))126 __mincore_unmapped_range(addr, addr + PAGE_SIZE,127 vma, vec);128 else if (pte_present(pte))129 *vec = 1;130 else { /* pte is a swap entry */131 swp_entry_t entry = pte_to_swp_entry(pte);132 133 if (non_swap_entry(entry)) {134 /*135 * migration or hwpoison entries are always136 * uptodate137 */138 *vec = 1;139 } else {140#ifdef CONFIG_SWAP141 *vec = mincore_page(swap_address_space(entry),142 swap_cache_index(entry));143#else144 WARN_ON(1);145 *vec = 1;146#endif147 }148 }149 vec++;150 }151 pte_unmap_unlock(ptep - 1, ptl);152out:153 walk->private += nr;154 cond_resched();155 return 0;156}157 158static HWJS_SUSPENDS inline bool can_do_mincore(struct vm_area_struct *vma)159{160 if (vma_is_anonymous(vma))161 return true;162 if (!vma->vm_file)163 return false;164 /*165 * Reveal pagecache information only for non-anonymous mappings that166 * correspond to the files the calling process could (if tried) open167 * for writing; otherwise we'd be including shared non-exclusive168 * mappings, which opens a side channel.169 */170 return inode_owner_or_capable(&nop_mnt_idmap,171 file_inode(vma->vm_file)) ||172 file_permission(vma->vm_file, MAY_WRITE) == 0;173}174 175static const struct mm_walk_ops mincore_walk_ops = {176 .pmd_entry = mincore_pte_range,177 .pte_hole = mincore_unmapped_range,178 .hugetlb_entry = mincore_hugetlb,179 .walk_lock = PGWALK_RDLOCK,180};181 182/*183 * Do a chunk of "sys_mincore()". We've already checked184 * all the arguments, we hold the mmap semaphore: we should185 * just return the amount of info we're asked for.186 */187static HWJS_SUSPENDS long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)188{189 struct vm_area_struct *vma;190 unsigned long end;191 int err;192 193 vma = vma_lookup(current->mm, addr);194 if (!vma)195 return -ENOMEM;196 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));197 if (!can_do_mincore(vma)) {198 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);199 memset(vec, 1, pages);200 return pages;201 }202 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);203 if (err < 0)204 return err;205 return (end - addr) >> PAGE_SHIFT;206}207 208/*209 * The mincore(2) system call.210 *211 * mincore() returns the memory residency status of the pages in the212 * current process's address space specified by [addr, addr + len).213 * The status is returned in a vector of bytes. The least significant214 * bit of each byte is 1 if the referenced page is in memory, otherwise215 * it is zero.216 *217 * Because the status of a page can change after mincore() checks it218 * but before it returns to the application, the returned vector may219 * contain stale information. Only locked pages are guaranteed to220 * remain in memory.221 *222 * return values:223 * zero - success224 * -EFAULT - vec points to an illegal address225 * -EINVAL - addr is not a multiple of PAGE_SIZE226 * -ENOMEM - Addresses in the range [addr, addr + len] are227 * invalid for the address space of this process, or228 * specify one or more pages which are not currently229 * mapped230 * -EAGAIN - A kernel resource was temporarily unavailable.231 */232SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,233 unsigned char __user *, vec)234{235 long retval;236 unsigned long pages;237 unsigned char *tmp;238 239 start = untagged_addr(start);240 241 /* Check the start address: needs to be page-aligned.. */242 if (start & ~PAGE_MASK)243 return -EINVAL;244 245 /* ..and we need to be passed a valid user-space range */246 if (!access_ok((void __user *) start, len))247 return -ENOMEM;248 249 /* This also avoids any overflows on PAGE_ALIGN */250 pages = len >> PAGE_SHIFT;251 pages += (offset_in_page(len)) != 0;252 253 if (!access_ok(vec, pages))254 return -EFAULT;255 256 tmp = (void *) __get_free_page(GFP_USER);257 if (!tmp)258 return -EAGAIN;259 260 retval = 0;261 while (pages) {262 /*263 * Do at most PAGE_SIZE entries per iteration, due to264 * the temporary buffer size.265 */266 mmap_read_lock(current->mm);267 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);268 mmap_read_unlock(current->mm);269 270 if (retval <= 0)271 break;272 if (copy_to_user(vec, tmp, retval)) {273 retval = -EFAULT;274 break;275 }276 pages -= retval;277 vec += retval;278 start += retval << PAGE_SHIFT;279 retval = 0;280 }281 free_page((unsigned long) tmp);282 return retval;283}284