1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * crash_dump.c - Memory preserving reboot related code. 4 * 5 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com) 6 * Copyright (C) IBM Corporation, 2004. All rights reserved 7 */ 8 #include <linux/errno.h> 9 #include <linux/crash_dump.h> 10 #include <linux/io.h> 11 #include <linux/uaccess.h> 12 13 /** 14 * copy_oldmem_page - copy one page from "oldmem" 15 * @pfn: page frame number to be copied 16 * @buf: target memory address for the copy; this can be in kernel address 17 * space or user address space (see @userbuf) 18 * @csize: number of bytes to copy 19 * @offset: offset in bytes into the page (based on pfn) to begin the copy 20 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 21 * otherwise @buf is in kernel address space, use memcpy(). 22 * 23 * Copy a page from "oldmem". For this page, there is no pte mapped 24 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 25 */ 26 ssize_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 = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE); 35 36 if (userbuf) { 37 if (copy_to_user(buf, (vaddr + offset), csize)) { 38 iounmap(vaddr); 39 return -EFAULT; 40 } 41 } else 42 memcpy(buf, (vaddr + offset), csize); 43 44 iounmap(vaddr); 45 return csize; 46 } 47