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
14 #include <linux/uaccess.h>
15
is_crashed_pfn_valid(unsigned long pfn)16 static inline bool is_crashed_pfn_valid(unsigned long pfn)
17 {
18 #ifndef CONFIG_X86_PAE
19 /*
20 * non-PAE kdump kernel executed from a PAE one will crop high pte
21 * bits and poke unwanted space counting again from address 0, we
22 * don't want that. pte must fit into unsigned long. In fact the
23 * test checks high 12 bits for being zero (pfn will be shifted left
24 * by PAGE_SHIFT).
25 */
26 return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
27 #else
28 return true;
29 #endif
30 }
31
32 /**
33 * copy_oldmem_page - copy one page from "oldmem"
34 * @pfn: page frame number to be copied
35 * @buf: target memory address for the copy; this can be in kernel address
36 * space or user address space (see @userbuf)
37 * @csize: number of bytes to copy
38 * @offset: offset in bytes into the page (based on pfn) to begin the copy
39 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
40 * otherwise @buf is in kernel address space, use memcpy().
41 *
42 * Copy a page from "oldmem". For this page, there might be no pte mapped
43 * in the current kernel.
44 */
copy_oldmem_page(unsigned long pfn,char * buf,size_t csize,unsigned long offset,int userbuf)45 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
46 unsigned long offset, int userbuf)
47 {
48 void *vaddr;
49
50 if (!csize)
51 return 0;
52
53 if (!is_crashed_pfn_valid(pfn))
54 return -EFAULT;
55
56 vaddr = kmap_local_pfn(pfn);
57
58 if (!userbuf) {
59 memcpy(buf, vaddr + offset, csize);
60 } else {
61 if (copy_to_user(buf, vaddr + offset, csize))
62 csize = -EFAULT;
63 }
64
65 kunmap_local(vaddr);
66
67 return csize;
68 }
69