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 /* Stores the physical address of elf header of crash image. */
  14 unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
  15
  16 /**
  17  * copy_oldmem_page - copy one page from "oldmem"
  18  * @pfn: page frame number to be copied
  19  * @buf: target memory address for the copy; this can be in kernel address
  20  *      space or user address space (see @userbuf)
  21  * @csize: number of bytes to copy
  22  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  23  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  24  *      otherwise @buf is in kernel address space, use memcpy().
  25  *
  26  * Copy a page from "oldmem". For this page, there is no pte mapped
  27  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  28  */
  29 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  30                 size_t csize, unsigned long offset, int userbuf)
  31 {
  32         void  *vaddr;
  33
  34         if (!csize)
  35                 return 0;
  36
  37         vaddr = ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
  38         if (!vaddr)
  39                 return -ENOMEM;
  40
  41         if (userbuf) {
  42                 if (copy_to_user(buf, vaddr + offset, csize)) {
  43                         iounmap(vaddr);
  44                         return -EFAULT;
  45                 }
  46         } else
  47                 memcpy(buf, vaddr + offset, csize);
  48
  49         set_iounmap_nonlazy();
  50         iounmap(vaddr);
  51         return csize;
  52 }