// 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/slab.h>#include <linux/syscalls.h>#include <linux/swap.h>#include <linux/leafops.h>#include <linux/shmem_fs.h>#include <linux/hugetlb.h>#include <linux/pgtable.h> #include <linux/uaccess.h>#include "swap.h"#include "internal.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	const unsigned long nr = (end - addr) >> PAGE_SHIFT;	unsigned char resident;	spinlock_t *ptl;	pte_t ptep; 	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);	ptep = huge_ptep_get(walk->mm, addr, pte);	resident = !huge_pte_none(ptep) && !pte_is_marker(ptep);	memset(walk->private, resident, nr);	walk->private += nr;	spin_unlock(ptl);#else	BUG();#endif	return 0;} static unsigned char mincore_swap(swp_entry_t entry, bool shmem){	struct swap_info_struct *si;	struct folio *folio = NULL;	unsigned char present = 0; 	/*	 * Shmem mapping may contain swapin error entries, which are	 * absent. Page table may contain migration or hwpoison	 * entries which are always uptodate.	 */	if (!softleaf_is_swap(entry))		return !shmem; 	if (!IS_ENABLED(CONFIG_SWAP)) {		WARN_ON(1);		return 0;	} 	/*	 * Shmem mapping lookup is lockless, so we need to grab the swap	 * device. mincore page table walk locks the PTL, and the swap	 * device is stable, avoid touching the si for better performance.	 */	if (shmem) {		si = get_swap_device(entry);		if (!si)			return 0;	}	folio = swap_cache_get_folio(entry);	if (shmem)		put_swap_device(si);	if (folio) {		present = folio_test_uptodate(folio);		folio_put(folio);	} 	return present;} /* * 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 index){	unsigned char present;	struct folio *folio; 	/*	 * 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.	 */	folio = filemap_get_entry(mapping, index);	if (!folio)		return 0; 	if (xa_is_value(folio)) {		if (!shmem_mapping(mapping))			return 0;		return mincore_swap(radix_to_swp_entry(folio), true);	}	present = folio_test_uptodate(folio);	folio_put(folio); 	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_pud_entry(pud_t *pudp, unsigned long addr, unsigned long end,		struct mm_walk *walk){	if (pud_is_huge(pudp_get(pudp))) {		const unsigned long nr = (end - addr) >> PAGE_SHIFT; 		memset(walk->private, 1, nr);		walk->private += nr;		walk->action = ACTION_CONTINUE;	} 	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;	int step, i; 	ptl = pmd_trans_huge_lock(pmd, vma);	if (ptl) {		memset(vec, 1, nr);		spin_unlock(ptl);		goto out;	} 	ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);	if (!ptep) {		walk->action = ACTION_AGAIN;		return 0;	}	for (; addr != end; ptep += step, addr += step * PAGE_SIZE) {		pte_t pte = ptep_get(ptep); 		step = 1;		/* We need to do cache lookup too for markers */		if (pte_none(pte) || pte_is_marker(pte))			__mincore_unmapped_range(addr, addr + PAGE_SIZE,						 vma, vec);		else if (pte_present(pte)) {			unsigned int batch = pte_batch_hint(ptep, pte); 			if (batch > 1) {				unsigned int max_nr = (end - addr) >> PAGE_SHIFT; 				step = min_t(unsigned int, batch, max_nr);			} 			for (i = 0; i < step; i++)				vec[i] = 1;		} else { /* pte is a swap entry */			const softleaf_t entry = softleaf_from_pte(pte); 			*vec = mincore_swap(entry, false);		}		vec += step;	}	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 file_owner_or_capable(vma->vm_file) ||	       file_permission(vma->vm_file, MAY_WRITE) == 0;} static const struct mm_walk_ops mincore_walk_ops = {	.pud_entry		= mincore_pud_entry,	.pmd_entry		= mincore_pte_range,	.pte_hole		= mincore_unmapped_range,	.hugetlb_entry		= mincore_hugetlb,	.walk_lock		= PGWALK_RDLOCK,}; /* * 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 = vma_lookup(current->mm, addr);	if (!vma)		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(vma, 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 (unlikely(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 = kmalloc(PAGE_SIZE, GFP_KERNEL);	if (!tmp)		return -EAGAIN; 	retval = 0;	while (pages) {		/*		 * Do at most PAGE_SIZE entries per iteration, due to		 * the temporary buffer size.		 */		mmap_read_lock(current->mm);		retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);		mmap_read_unlock(current->mm); 		if (retval <= 0)			break;		if (copy_to_user(vec, tmp, retval)) {			retval = -EFAULT;			break;		}		pages -= retval;		vec += retval;		start += retval << PAGE_SHIFT;		retval = 0;	}	kfree(tmp);	return retval;}