1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * 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 9 #include <linux/slab.h> 10 #include <linux/errno.h> 11 #include <linux/highmem.h> 12 #include <linux/crash_dump.h> 13 14 #include <linux/uaccess.h> 15 16 static inline bool is_crashed_pfn_valid(unsigned long pfn) 17 { 18 #ifndef CONFIG_X86_PAE 19 /* 20 * non-PAE kdump kernel executed from a PAE one will crop high pte 21 * bits and poke unwanted space counting again from address 0, we 22 * don't want that. pte must fit into unsigned long. In fact the 23 * test checks high 12 bits for being zero (pfn will be shifted left 24 * by PAGE_SHIFT). 25 */ 26 return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; 27 #else 28 return true; 29 #endif 30 } 31 32 /** 33 * copy_oldmem_page - copy one page from "oldmem" 34 * @pfn: page frame number to be copied 35 * @buf: target memory address for the copy; this can be in kernel address 36 * space or user address space (see @userbuf) 37 * @csize: number of bytes to copy 38 * @offset: offset in bytes into the page (based on pfn) to begin the copy 39 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 40 * otherwise @buf is in kernel address space, use memcpy(). 41 * 42 * Copy a page from "oldmem". For this page, there might be no pte mapped 43 * in the current kernel. 44 */ 45 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize, 46 unsigned long offset, int userbuf) 47 { 48 void *vaddr; 49 50 if (!csize) 51 return 0; 52 53 if (!is_crashed_pfn_valid(pfn)) 54 return -EFAULT; 55 56 vaddr = kmap_local_pfn(pfn); 57 58 if (!userbuf) { 59 memcpy(buf, vaddr + offset, csize); 60 } else { 61 if (copy_to_user(buf, vaddr + offset, csize)) 62 csize = -EFAULT; 63 } 64 65 kunmap_local(vaddr); 66 67 return csize; 68 } 69