root/arch/x86/kernel/crash_dump_64.c

DEFINITIONS

1. copy_oldmem_page

/*
 *      Memory preserving reboot related code.
 *
 *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *      Copyright (C) IBM Corporation, 2004. All rights reserved
 */

#include <linux/errno.h>
#include <linux/crash_dump.h>
#include <linux/uaccess.h>
#include <linux/io.h>

/**
 * 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  *vaddr;

        if (!csize)
                return 0;

        vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
        if (!vaddr)
                return -ENOMEM;

        if (userbuf) {
                if (copy_to_user(buf, vaddr + offset, csize)) {
                        iounmap(vaddr);
                        return -EFAULT;
                }
        } else
                memcpy(buf, vaddr + offset, csize);

        iounmap(vaddr);
        return csize;
}