1/*
2 *	kernel/crash_dump.c - Memory preserving reboot related code.
3 *
4 *	Created by: Simon Horman <horms@verge.net.au>
5 *	Original code moved from kernel/crash.c
6 *	Original code comment copied from the i386 version of this file
7 */
8
9#include <linux/errno.h>
10#include <linux/types.h>
11#include <linux/crash_dump.h>
12
13#include <asm/page.h>
14#include <asm/uaccess.h>
15
16/**
17 * copy_oldmem_page - copy one page from "oldmem"
18 * @pfn: page frame number to be copied
19 * @buf: target memory address for the copy; this can be in kernel address
20 *	space or user address space (see @userbuf)
21 * @csize: number of bytes to copy
22 * @offset: offset in bytes into the page (based on pfn) to begin the copy
23 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
24 *	otherwise @buf is in kernel address space, use memcpy().
25 *
26 * Copy a page from "oldmem". For this page, there is no pte mapped
27 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
28 *
29 * Calling copy_to_user() in atomic context is not desirable. Hence first
30 * copying the data to a pre-allocated kernel page and then copying to user
31 * space in non-atomic context.
32 */
33ssize_t
34copy_oldmem_page(unsigned long pfn, char *buf,
35		size_t csize, unsigned long offset, int userbuf)
36{
37	void  *vaddr;
38
39	if (!csize)
40		return 0;
41	vaddr = __va(pfn<<PAGE_SHIFT);
42	if (userbuf) {
43		if (copy_to_user(buf, (vaddr + offset), csize)) {
44			return -EFAULT;
45		}
46	} else
47		memcpy(buf, (vaddr + offset), csize);
48	return csize;
49}
50
51