LXR linux/arch/x86/kernel/crash_dump

   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/highmem.h>
  10#include <linux/crash_dump.h>
  11
  12#include <asm/uaccess.h>
  13
  14static void *kdump_buf_page;
  15
  16/* Stores the physical address of elf header of crash image. */
  17unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
  18
  19/**
  20 * copy_oldmem_page - copy one page from "oldmem"
  21 * @pfn: page frame number to be copied
  22 * @buf: target memory address for the copy; this can be in kernel address
  23 *      space or user address space (see @userbuf)
  24 * @csize: number of bytes to copy
  25 * @offset: offset in bytes into the page (based on pfn) to begin the copy
  26 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  27 *      otherwise @buf is in kernel address space, use memcpy().
  28 *
  29 * Copy a page from "oldmem". For this page, there is no pte mapped
  30 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  31 *
  32 * Calling copy_to_user() in atomic context is not desirable. Hence first
  33 * copying the data to a pre-allocated kernel page and then copying to user
  34 * space in non-atomic context.
  35 */
  36ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  37                               size_t csize, unsigned long offset, int userbuf)
  38{
  39        void  *vaddr;
  40
  41        if (!csize)
  42                return 0;
  43
  44        vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
  45
  46        if (!userbuf) {
  47                memcpy(buf, (vaddr + offset), csize);
  48                kunmap_atomic(vaddr, KM_PTE0);
  49        } else {
  50                if (!kdump_buf_page) {
  51                        printk(KERN_WARNING "Kdump: Kdump buffer page not"
  52                                " allocated\n");
  53                        kunmap_atomic(vaddr, KM_PTE0);
  54                        return -EFAULT;
  55                }
  56                copy_page(kdump_buf_page, vaddr);
  57                kunmap_atomic(vaddr, KM_PTE0);
  58                if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  59                        return -EFAULT;
  60        }
  61
  62        return csize;
  63}
  64
  65static int __init kdump_buf_page_init(void)
  66{
  67        int ret = 0;
  68
  69        kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  70        if (!kdump_buf_page) {
  71                printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  72                         " page\n");
  73                ret = -ENOMEM;
  74        }
  75
  76        return ret;
  77}
  78arch_initcall(kdump_buf_page_init);
  79