LXR linux/arch/i386/kernel/crash

   1/*
   2 *      kernel/crash_dump.c - 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/highmem.h>
  10#include <linux/crash_dump.h>
  11
  12#include <asm/uaccess.h>
  13
  14static void *kdump_buf_page;
  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 * Calling copy_to_user() in atomic context is not desirable. Hence first
  30 * copying the data to a pre-allocated kernel page and then copying to user
  31 * space in non-atomic context.
  32 */
  33ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  34                               size_t csize, unsigned long offset, int userbuf)
  35{
  36        void  *vaddr;
  37
  38        if (!csize)
  39                return 0;
  40
  41        vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
  42
  43        if (!userbuf) {
  44                memcpy(buf, (vaddr + offset), csize);
  45                kunmap_atomic(vaddr, KM_PTE0);
  46        } else {
  47                if (!kdump_buf_page) {
  48                        printk(KERN_WARNING "Kdump: Kdump buffer page not"
  49                                " allocated\n");
  50                        return -EFAULT;
  51                }
  52                copy_page(kdump_buf_page, vaddr);
  53                kunmap_atomic(vaddr, KM_PTE0);
  54                if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  55                        return -EFAULT;
  56        }
  57
  58        return csize;
  59}
  60
  61static int __init kdump_buf_page_init(void)
  62{
  63        int ret = 0;
  64
  65        kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  66        if (!kdump_buf_page) {
  67                printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  68                         " page\n");
  69                ret = -ENOMEM;
  70        }
  71
  72        return ret;
  73}
  74arch_initcall(kdump_buf_page_init);
  75