// SPDX-License-Identifier: GPL-2.0 /* * linux/mm/mincore.c * * Copyright (C) 1994-2006 Linus Torvalds */ /* * The mincore() system call. */ #include <linux/pagemap.h> #include <linux/gfp.h> #include <linux/pagewalk.h> #include <linux/mman.h> #include <linux/syscalls.h> #include <linux/swap.h> #include <linux/swapops.h> #include <linux/shmem_fs.h> #include <linux/hugetlb.h> #include <linux/uaccess.h> #include <asm/pgtable.h> static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, unsigned long end, struct mm_walk *walk) { #ifdef CONFIG_HUGETLB_PAGE unsigned char present; unsigned char *vec = walk->private; /* * Hugepages under user process are always in RAM and never * swapped out, but theoretically it needs to be checked. */ present = pte && !huge_pte_none(huge_ptep_get(pte)); for (; addr != end; vec++, addr += PAGE_SIZE) *vec = present; walk->private = vec; #else BUG(); #endif return 0; } /* * Later we can get more picky about what "in core" means precisely. * For now, simply check to see if the page is in the page cache, * and is up to date; i.e. that no page-in operation would be required * at this time if an application were to map and access this page. */ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) { unsigned char present = 0; struct page *page; /* * When tmpfs swaps out a page from a file, any process mapping that * file will not get a swp_entry_t in its pte, but rather it is like * any other file mapping (ie. marked !present and faulted in with * tmpfs's .fault). So swapped out tmpfs mappings are tested here. */ #ifdef CONFIG_SWAP if (shmem_mapping(mapping)) { page = find_get_entry(mapping, pgoff); /* * shmem/tmpfs may return swap: account for swapcache * page too. */ if (xa_is_value(page)) { swp_entry_t swp = radix_to_swp_entry(page); struct swap_info_struct *si; /* Prevent swap device to being swapoff under us */ si = get_swap_device(swp); if (si) { page = find_get_page(swap_address_space(swp), swp_offset(swp)); put_swap_device(si); } else page = NULL; } } else page = find_get_page(mapping, pgoff); #else page = find_get_page(mapping, pgoff); #endif if (page) { present = PageUptodate(page); put_page(page); } return present; } static int __mincore_unmapped_range(unsigned long addr, unsigned long end, struct vm_area_struct *vma, unsigned char *vec) { unsigned long nr = (end - addr) >> PAGE_SHIFT; int i; if (vma->vm_file) { pgoff_t pgoff; pgoff = linear_page_index(vma, addr); for (i = 0; i < nr; i++, pgoff++) vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); } else { for (i = 0; i < nr; i++) vec[i] = 0; } return nr; } static int mincore_unmapped_range(unsigned long addr, unsigned long end, __always_unused int depth, struct mm_walk *walk) { walk->private += __mincore_unmapped_range(addr, end, walk->vma, walk->private); return 0; } static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) { spinlock_t *ptl; struct vm_area_struct *vma = walk->vma; pte_t *ptep; unsigned char *vec = walk->private; int nr = (end - addr) >> PAGE_SHIFT; ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { memset(vec, 1, nr); spin_unlock(ptl); goto out; } if (pmd_trans_unstable(pmd)) { __mincore_unmapped_range(addr, end, vma, vec); goto out; } ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); for (; addr != end; ptep++, addr += PAGE_SIZE) { pte_t pte = *ptep; if (pte_none(pte)) __mincore_unmapped_range(addr, addr + PAGE_SIZE, vma, vec); else if (pte_present(pte)) *vec = 1; else { /* pte is a swap entry */ swp_entry_t entry = pte_to_swp_entry(pte); if (non_swap_entry(entry)) { /* * migration or hwpoison entries are always * uptodate */ *vec = 1; } else { #ifdef CONFIG_SWAP *vec = mincore_page(swap_address_space(entry), swp_offset(entry)); #else WARN_ON(1); *vec = 1; #endif } } vec++; } pte_unmap_unlock(ptep - 1, ptl); out: walk->private += nr; cond_resched(); return 0; } static inline bool can_do_mincore(struct vm_area_struct *vma) { if (vma_is_anonymous(vma)) return true; if (!vma->vm_file) return false; /* * Reveal pagecache information only for non-anonymous mappings that * correspond to the files the calling process could (if tried) open * for writing; otherwise we'd be including shared non-exclusive * mappings, which opens a side channel. */ return inode_owner_or_capable(file_inode(vma->vm_file)) || inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0; } static const struct mm_walk_ops mincore_walk_ops = { .pmd_entry = mincore_pte_range, .pte_hole = mincore_unmapped_range, .hugetlb_entry = mincore_hugetlb, }; /* * Do a chunk of "sys_mincore()". We've already checked * all the arguments, we hold the mmap semaphore: we should * just return the amount of info we're asked for. */ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) { struct vm_area_struct *vma; unsigned long end; int err; vma = find_vma(current->mm, addr); if (!vma || addr < vma->vm_start) return -ENOMEM; end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); if (!can_do_mincore(vma)) { unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); memset(vec, 1, pages); return pages; } err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); if (err < 0) return err; return (end - addr) >> PAGE_SHIFT; } /* * The mincore(2) system call. * * mincore() returns the memory residency status of the pages in the * current process's address space specified by [addr, addr + len). * The status is returned in a vector of bytes. The least significant * bit of each byte is 1 if the referenced page is in memory, otherwise * it is zero. * * Because the status of a page can change after mincore() checks it * but before it returns to the application, the returned vector may * contain stale information. Only locked pages are guaranteed to * remain in memory. * * return values: * zero - success * -EFAULT - vec points to an illegal address * -EINVAL - addr is not a multiple of PAGE_SIZE * -ENOMEM - Addresses in the range [addr, addr + len] are * invalid for the address space of this process, or * specify one or more pages which are not currently * mapped * -EAGAIN - A kernel resource was temporarily unavailable. */ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, unsigned char __user *, vec) { long retval; unsigned long pages; unsigned char *tmp; start = untagged_addr(start); /* Check the start address: needs to be page-aligned.. */ if (start & ~PAGE_MASK) return -EINVAL; /* ..and we need to be passed a valid user-space range */ if (!access_ok((void __user *) start, len)) return -ENOMEM; /* This also avoids any overflows on PAGE_ALIGN */ pages = len >> PAGE_SHIFT; pages += (offset_in_page(len)) != 0; if (!access_ok(vec, pages)) return -EFAULT; tmp = (void *) __get_free_page(GFP_USER); if (!tmp) return -EAGAIN; retval = 0; while (pages) { /* * Do at most PAGE_SIZE entries per iteration, due to * the temporary buffer size. */ down_read(¤t->mm->mmap_sem); retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); up_read(¤t->mm->mmap_sem); if (retval <= 0) break; if (copy_to_user(vec, tmp, retval)) { retval = -EFAULT; break; } pages -= retval; vec += retval; start += retval << PAGE_SHIFT; retval = 0; } free_page((unsigned long) tmp); return retval; }