arch/x86/kernel/crash_dump_32.c

   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 }