arch/x86/kernel/crash_dump_64.c

   1 /*
   2  *      Memory preserving reboot related code.
   3  *
   4  *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   5  *      Copyright (C) IBM Corporation, 2004. All rights reserved
   6  */
   7
   8 #include <linux/errno.h>
   9 #include <linux/crash_dump.h>
  10 #include <linux/uaccess.h>
  11 #include <linux/io.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_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
  35         if (!vaddr)
  36                 return -ENOMEM;
  37
  38         if (userbuf) {
  39                 if (copy_to_user(buf, vaddr + offset, csize)) {
  40                         iounmap(vaddr);
  41                         return -EFAULT;
  42                 }
  43         } else
  44                 memcpy(buf, vaddr + offset, csize);
  45
  46         set_iounmap_nonlazy();
  47         iounmap(vaddr);
  48         return csize;
  49 }