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 #include <linux/uio.h> 14 15 static inline bool is_crashed_pfn_valid(unsigned long pfn) 16 { 17 #ifndef CONFIG_X86_PAE 18 /* 19 * non-PAE kdump kernel executed from a PAE one will crop high pte 20 * bits and poke unwanted space counting again from address 0, we 21 * don't want that. pte must fit into unsigned long. In fact the 22 * test checks high 12 bits for being zero (pfn will be shifted left 23 * by PAGE_SHIFT). 24 */ 25 return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; 26 #else 27 return true; 28 #endif 29 } 30 31 ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize, 32 unsigned long offset) 33 { 34 void *vaddr; 35 36 if (!csize) 37 return 0; 38 39 if (!is_crashed_pfn_valid(pfn)) 40 return -EFAULT; 41 42 vaddr = kmap_local_pfn(pfn); 43 csize = copy_to_iter(vaddr + offset, csize, iter); 44 kunmap_local(vaddr); 45 46 return csize; 47 } 48