/*
   *	kernel/crash_dump.c - Memory preserving reboot related code.
   *
   *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   *	Copyright (C) IBM Corporation, 2004. All rights reserved
   */
  
  #include <linux/smp_lock.h>
  #include <linux/errno.h>
  #include <linux/proc_fs.h>
  #include <linux/bootmem.h>
  #include <linux/highmem.h>
  #include <linux/crash_dump.h>
  
  #include <asm/io.h>
  #include <asm/uaccess.h>

  /* Stores the physical address of elf header of crash image. */

  unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;

  /**
   * copy_oldmem_page - copy one page from "oldmem"
   * @pfn: page frame number to be copied
   * @buf: target memory address for the copy; this can be in kernel address
   *	space or user address space (see @userbuf)
   * @csize: number of bytes to copy
   * @offset: offset in bytes into the page (based on pfn) to begin the copy
   * @userbuf: if set, @buf is in user address space, use copy_to_user(),
   *	otherwise @buf is in kernel address space, use memcpy().
   *

   * Copy a page from "oldmem". For this page, there is no pte mapped
   * in the current kernel. We stitch up a pte, similar to kmap_atomic.
   */
  ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  				size_t csize, unsigned long offset, int userbuf)
  {
  	void *page, *vaddr;
  
  	if (!csize)
  		return 0;
  
  	page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  	if (!page)
  		return -ENOMEM;
  
  	vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
  	copy_page(page, vaddr);
  	kunmap_atomic(vaddr, KM_PTE0);
  
  	if (userbuf) {
  		if (copy_to_user(buf, (page + offset), csize)) {
  			kfree(page);
  			return -EFAULT;
  		}
  	} else {
  		memcpy(buf, (page + offset), csize);
  	}
  
  	kfree(page);
  	return csize;
  }