arch/x86/kernel/crash_dump_64.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/errno.h>
  10 #include <linux/crash_dump.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/io.h>
  13
  14 /**
  15  * copy_oldmem_page - copy one page from "oldmem"
  16  * @pfn: page frame number to be copied
  17  * @buf: target memory address for the copy; this can be in kernel address
  18  *      space or user address space (see @userbuf)
  19  * @csize: number of bytes to copy
  20  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  21  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  22  *      otherwise @buf is in kernel address space, use memcpy().
  23  *
  24  * Copy a page from "oldmem". For this page, there is no pte mapped
  25  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  26  */
  27 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  28                 size_t csize, unsigned long offset, int userbuf)
  29 {
  30         void  *vaddr;
  31
  32         if (!csize)
  33                 return 0;
  34
  35         vaddr = ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
  36         if (!vaddr)
  37                 return -ENOMEM;
  38
  39         if (userbuf) {
  40                 if (copy_to_user(buf, vaddr + offset, csize)) {
  41                         iounmap(vaddr);
  42                         return -EFAULT;
  43                 }
  44         } else
  45                 memcpy(buf, vaddr + offset, csize);
  46
  47         set_iounmap_nonlazy();
  48         iounmap(vaddr);
  49         return csize;
  50 }