1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * crash_dump.c - 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 #include <linux/errno.h>
9 #include <linux/crash_dump.h>
10 #include <linux/io.h>
11 #include <linux/uaccess.h>
12
13 /**
14 * copy_oldmem_page - copy one page from "oldmem"
15 * @pfn: page frame number to be copied
16 * @buf: target memory address for the copy; this can be in kernel address
17 * space or user address space (see @userbuf)
18 * @csize: number of bytes to copy
19 * @offset: offset in bytes into the page (based on pfn) to begin the copy
20 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
21 * otherwise @buf is in kernel address space, use memcpy().
22 *
23 * Copy a page from "oldmem". For this page, there is no pte mapped
24 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
25 */
26 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
27 size_t csize, unsigned long offset, int userbuf)
28 {
29 void *vaddr;
30
31 if (!csize)
32 return 0;
33
34 vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
35
36 if (userbuf) {
37 if (copy_to_user(buf, (vaddr + offset), csize)) {
38 iounmap(vaddr);
39 return -EFAULT;
40 }
41 } else
42 memcpy(buf, (vaddr + offset), csize);
43
44 iounmap(vaddr);
45 return csize;
46 }