1#include <linux/highmem.h>
2#include <linux/bootmem.h>
3#include <linux/crash_dump.h>
4#include <asm/uaccess.h>
5#include <linux/slab.h>
6
7static void *kdump_buf_page;
8
9/**
10 * copy_oldmem_page - copy one page from "oldmem"
11 * @pfn: page frame number to be copied
12 * @buf: target memory address for the copy; this can be in kernel address
13 *	space or user address space (see @userbuf)
14 * @csize: number of bytes to copy
15 * @offset: offset in bytes into the page (based on pfn) to begin the copy
16 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
17 *	otherwise @buf is in kernel address space, use memcpy().
18 *
19 * Copy a page from "oldmem". For this page, there is no pte mapped
20 * in the current kernel.
21 *
22 * Calling copy_to_user() in atomic context is not desirable. Hence first
23 * copying the data to a pre-allocated kernel page and then copying to user
24 * space in non-atomic context.
25 */
26ssize_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 = kmap_atomic_pfn(pfn);
35
36	if (!userbuf) {
37		memcpy(buf, (vaddr + offset), csize);
38		kunmap_atomic(vaddr);
39	} else {
40		if (!kdump_buf_page) {
41			pr_warn("Kdump: Kdump buffer page not allocated\n");
42
43			return -EFAULT;
44		}
45		copy_page(kdump_buf_page, vaddr);
46		kunmap_atomic(vaddr);
47		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
48			return -EFAULT;
49	}
50
51	return csize;
52}
53
54static int __init kdump_buf_page_init(void)
55{
56	int ret = 0;
57
58	kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
59	if (!kdump_buf_page) {
60		pr_warn("Kdump: Failed to allocate kdump buffer page\n");
61		ret = -ENOMEM;
62	}
63
64	return ret;
65}
66arch_initcall(kdump_buf_page_init);
67