1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * This code comes from arch/arm64/kernel/crash_dump.c
 4 * Created by: AKASHI Takahiro <takahiro.akashi@linaro.org>
 5 * Copyright (C) 2017 Linaro Limited
 6 */
 7
 8#include <linux/crash_dump.h>
 9#include <linux/io.h>
10
11/**
12 * copy_oldmem_page() - copy one page from old kernel memory
13 * @pfn: page frame number to be copied
14 * @buf: buffer where the copied page is placed
15 * @csize: number of bytes to copy
16 * @offset: offset in bytes into the page
17 * @userbuf: if set, @buf is in a user address space
18 *
19 * This function copies one page from old kernel memory into buffer pointed by
20 * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
21 * copied or negative error in case of failure.
22 */
23ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
24			 size_t csize, unsigned long offset,
25			 int userbuf)
26{
27	void *vaddr;
28
29	if (!csize)
30		return 0;
31
32	vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
33	if (!vaddr)
34		return -ENOMEM;
35
36	if (userbuf) {
37		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
38			memunmap(vaddr);
39			return -EFAULT;
40		}
41	} else
42		memcpy(buf, vaddr + offset, csize);
43
44	memunmap(vaddr);
45	return csize;
46}