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
12#include <asm/page.h>
13#include <asm/uaccess.h>
14
15/**
16 * copy_oldmem_page - copy one page from "oldmem"
17 * @pfn: page frame number to be copied
18 * @buf: target memory address for the copy; this can be in kernel address
19 *	space or user address space (see @userbuf)
20 * @csize: number of bytes to copy
21 * @offset: offset in bytes into the page (based on pfn) to begin the copy
22 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
23 *	otherwise @buf is in kernel address space, use memcpy().
24 *
25 * Copy a page from "oldmem". For this page, there is no pte mapped
26 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
27 *
28 * Calling copy_to_user() in atomic context is not desirable. Hence first
29 * copying the data to a pre-allocated kernel page and then copying to user
30 * space in non-atomic context.
31 */
32ssize_t
33copy_oldmem_page(unsigned long pfn, char *buf,
34		size_t csize, unsigned long offset, int userbuf)
35{
36	void  *vaddr;
37
38	if (!csize)
39		return 0;
40	vaddr = __va(pfn<<PAGE_SHIFT);
41	if (userbuf) {
42		if (copy_to_user(buf, (vaddr + offset), csize)) {
43			return -EFAULT;
44		}
45	} else
46		memcpy(buf, (vaddr + offset), csize);
47	return csize;
48}
49