root/arch/x86/kernel/crash_dump_32.c

DEFINITIONS

1. copy_oldmem_page
2. kdump_buf_page_init

/*
 *      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/highmem.h>
#include <linux/crash_dump.h>

#include <asm/uaccess.h>

static void *kdump_buf_page;

/**
 * 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.
 *
 * Calling copy_to_user() in atomic context is not desirable. Hence first
 * copying the data to a pre-allocated kernel page and then copying to user
 * space in non-atomic context.
 */
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 = kmap_atomic_pfn(pfn, KM_PTE0);

        if (!userbuf) {
                memcpy(buf, (vaddr + offset), csize);
                kunmap_atomic(vaddr, KM_PTE0);
        } else {
                if (!kdump_buf_page) {
                        printk(KERN_WARNING "Kdump: Kdump buffer page not"
                                " allocated\n");
                        kunmap_atomic(vaddr, KM_PTE0);
                        return -EFAULT;
                }
                copy_page(kdump_buf_page, vaddr);
                kunmap_atomic(vaddr, KM_PTE0);
                if (copy_to_user(buf, (kdump_buf_page + offset), csize))
                        return -EFAULT;
        }

        return csize;
}

static int __init kdump_buf_page_init(void)
{
        int ret = 0;

        kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!kdump_buf_page) {
                printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
                         " page\n");
                ret = -ENOMEM;
        }

        return ret;
}
arch_initcall(kdump_buf_page_init);