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mm/mincore.c
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// SPDX-License-Identifier: GPL-2.0 |
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/* * linux/mm/mincore.c * |
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* Copyright (C) 1994-2006 Linus Torvalds |
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*/ /* * The mincore() system call. */ |
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#include <linux/pagemap.h> |
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#include <linux/gfp.h> |
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#include <linux/pagewalk.h> |
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#include <linux/mman.h> #include <linux/syscalls.h> |
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#include <linux/swap.h> #include <linux/swapops.h> |
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#include <linux/shmem_fs.h> |
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#include <linux/hugetlb.h> |
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#include <linux/uaccess.h> |
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#include <asm/pgtable.h> |
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static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, unsigned long end, struct mm_walk *walk) |
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{ #ifdef CONFIG_HUGETLB_PAGE |
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unsigned char present; unsigned char *vec = walk->private; |
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/* * 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; |
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#else BUG(); #endif |
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return 0; |
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} |
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/* * 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); |
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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; |
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} } 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) |
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{ |
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unsigned long nr = (end - addr) >> PAGE_SHIFT; |
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int i; |
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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, struct mm_walk *walk) { walk->private += __mincore_unmapped_range(addr, end, walk->vma, walk->private); |
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return 0; |
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} |
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static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) |
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{ spinlock_t *ptl; |
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struct vm_area_struct *vma = walk->vma; |
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pte_t *ptep; |
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unsigned char *vec = walk->private; int nr = (end - addr) >> PAGE_SHIFT; |
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ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { |
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memset(vec, 1, nr); spin_unlock(ptl); goto out; } |
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if (pmd_trans_unstable(pmd)) { |
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__mincore_unmapped_range(addr, end, vma, vec); |
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goto out; } ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); for (; addr != end; ptep++, addr += PAGE_SIZE) { |
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pte_t pte = *ptep; |
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if (pte_none(pte)) |
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__mincore_unmapped_range(addr, addr + PAGE_SIZE, vma, vec); |
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else if (pte_present(pte)) |
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*vec = 1; |
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else { /* pte is a swap entry */ |
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swp_entry_t entry = pte_to_swp_entry(pte); |
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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 } |
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} |
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vec++; |
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} |
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pte_unmap_unlock(ptep - 1, ptl); |
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out: walk->private += nr; cond_resched(); return 0; |
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} |
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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; } |
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static const struct mm_walk_ops mincore_walk_ops = { .pmd_entry = mincore_pte_range, .pte_hole = mincore_unmapped_range, .hugetlb_entry = mincore_hugetlb, }; |
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/* * 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. */ |
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static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) |
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{ |
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struct vm_area_struct *vma; |
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unsigned long end; |
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int err; |
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vma = find_vma(current->mm, addr); |
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if (!vma || addr < vma->vm_start) return -ENOMEM; |
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end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); |
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if (!can_do_mincore(vma)) { unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); memset(vec, 1, pages); return pages; } |
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err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); |
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if (err < 0) return err; |
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return (end - addr) >> PAGE_SHIFT; |
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} /* * 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 |
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* -EINVAL - addr is not a multiple of PAGE_SIZE |
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* -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. */ |
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SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, unsigned char __user *, vec) |
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{ |
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long retval; unsigned long pages; unsigned char *tmp; |
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start = untagged_addr(start); |
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/* Check the start address: needs to be page-aligned.. */ |
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if (start & ~PAGE_MASK) |
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return -EINVAL; |
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|
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/* ..and we need to be passed a valid user-space range */ |
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if (!access_ok((void __user *) start, len)) |
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return -ENOMEM; |
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/* This also avoids any overflows on PAGE_ALIGN */ |
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pages = len >> PAGE_SHIFT; |
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pages += (offset_in_page(len)) != 0; |
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if (!access_ok(vec, pages)) |
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return -EFAULT; |
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|
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tmp = (void *) __get_free_page(GFP_USER); if (!tmp) |
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return -EAGAIN; |
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retval = 0; while (pages) { /* * Do at most PAGE_SIZE entries per iteration, due to * the temporary buffer size. */ down_read(¤t->mm->mmap_sem); |
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retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); |
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up_read(¤t->mm->mmap_sem); if (retval <= 0) break; if (copy_to_user(vec, tmp, retval)) { retval = -EFAULT; break; |
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} |
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pages -= retval; vec += retval; start += retval << PAGE_SHIFT; retval = 0; |
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} |
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free_page((unsigned long) tmp); return retval; |
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} |