1// SPDX-License-Identifier: GPL-2.0
2/*
3 *	Memory preserving reboot related code.
4 *
5 *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
6 *	Copyright (C) IBM Corporation, 2004. All rights reserved
7 */
8
9#include <linux/slab.h>
10#include <linux/errno.h>
11#include <linux/highmem.h>
12#include <linux/crash_dump.h>
13#include <linux/uio.h>
14
15static inline bool is_crashed_pfn_valid(unsigned long pfn)
16{
17#ifndef CONFIG_X86_PAE
18	/*
19	 * non-PAE kdump kernel executed from a PAE one will crop high pte
20	 * bits and poke unwanted space counting again from address 0, we
21	 * don't want that. pte must fit into unsigned long. In fact the
22	 * test checks high 12 bits for being zero (pfn will be shifted left
23	 * by PAGE_SHIFT).
24	 */
25	return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
26#else
27	return true;
28#endif
29}
30
31ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
32			 unsigned long offset)
33{
34	void  *vaddr;
35
36	if (!csize)
37		return 0;
38
39	if (!is_crashed_pfn_valid(pfn))
40		return -EFAULT;
41
42	vaddr = kmap_local_pfn(pfn);
43	csize = copy_to_iter(vaddr + offset, csize, iter);
44	kunmap_local(vaddr);
45
46	return csize;
47}
48