1 files changed, 283 insertions, 0 deletions
diff --git a/mm/mincore.c b/mm/mincore.c
new file mode 100644
index 000000000..dad3622cc
--- /dev/null
+++ b/mm/mincore.c
@@ -0,0 +1,283 @@
+// 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/pgtable.h>
+
+#include <linux/uaccess.h>
+#include "swap.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_mostly(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 index)
+{
+	unsigned char present = 0;
+	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_incore_folio(mapping, index);
+	if (!IS_ERR(folio)) {
+		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_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;
+	}
+
+	ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!ptep) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+	for (; addr != end; ptep++, addr += PAGE_SIZE) {
+		pte_t pte = ptep_get(ptep);
+
+		/* We need to do cache lookup too for pte markers */
+		if (pte_none_mostly(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(&nop_mnt_idmap,
+				      file_inode(vma->vm_file)) ||
+	       file_permission(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,
+	.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->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.
+		 */
+		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;
+	}
+	free_page((unsigned long) tmp);
+	return retval;
+}