sw64: add kdump support

// SPDX-License-Identifier: GPL-2.0

/*

 * arch/sw_64/kernel/crash_dump.c

 *

 * Copyright (C) 2019 JN

 * Author: He Sheng

 *

 * This code is taken from arch/x86/kernel/crash_dump_64.c

 *   Created by: Hariprasad Nellitheertha (hari@in.ibm.com)

 *   Copyright (C) IBM Corporation, 2004. All rights reserved

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#include <linux/uaccess.h>

#include <linux/io.h>

/**

 * copy_oldmem_page() - copy one page from old kernel memory

 * @pfn: page frame number to be copied

 * @buf: buffer where the copied page is placed

 * @csize: number of bytes to copy

 * @offset: offset in bytes into the page

 * @userbuf: if set, @buf is int he user address space

 *

 * This function copies one page from old kernel memory into buffer pointed by

 * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes

 * copied or negative error in case of failure.

 */

ssize_t copy_oldmem_page(unsigned long pfn, char *buf,

			 size_t csize, unsigned long offset,

			 int userbuf)

{

	void *vaddr;

	if (!csize)

		return 0;

	vaddr = ioremap(__pfn_to_phys(pfn), PAGE_SIZE);

	if (!vaddr)

		return -ENOMEM;

	if (userbuf) {

		if (copy_to_user(buf, vaddr + offset, csize)) {

			iounmap(vaddr);

			return -EFAULT;

		}

	} else {

		memcpy(buf, vaddr + offset, csize);

	}

	iounmap(vaddr);

	return csize;

}