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/slab.h>
   9#include <linux/errno.h>
  10#include <linux/highmem.h>
  11#include <linux/crash_dump.h>
  12
  13#include <linux/uaccess.h>
  14
  15static void *kdump_buf_page;
  16
  17static inline bool is_crashed_pfn_valid(unsigned long pfn)
  18{
  19#ifndef CONFIG_X86_PAE
  20        /*
  21         * non-PAE kdump kernel executed from a PAE one will crop high pte
  22         * bits and poke unwanted space counting again from address 0, we
  23         * don't want that. pte must fit into unsigned long. In fact the
  24         * test checks high 12 bits for being zero (pfn will be shifted left
  25         * by PAGE_SHIFT).
  26         */
  27        return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
  28#else
  29        return true;
  30#endif
  31}
  32
  33/**
  34 * copy_oldmem_page - copy one page from "oldmem"
  35 * @pfn: page frame number to be copied
  36 * @buf: target memory address for the copy; this can be in kernel address
  37 *      space or user address space (see @userbuf)
  38 * @csize: number of bytes to copy
  39 * @offset: offset in bytes into the page (based on pfn) to begin the copy
  40 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  41 *      otherwise @buf is in kernel address space, use memcpy().
  42 *
  43 * Copy a page from "oldmem". For this page, there is no pte mapped
  44 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  45 *
  46 * Calling copy_to_user() in atomic context is not desirable. Hence first
  47 * copying the data to a pre-allocated kernel page and then copying to user
  48 * space in non-atomic context.
  49 */
  50ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  51                               size_t csize, unsigned long offset, int userbuf)
  52{
  53        void  *vaddr;
  54
  55        if (!csize)
  56                return 0;
  57
  58        if (!is_crashed_pfn_valid(pfn))
  59                return -EFAULT;
  60
  61        vaddr = kmap_atomic_pfn(pfn);
  62
  63        if (!userbuf) {
  64                memcpy(buf, (vaddr + offset), csize);
  65                kunmap_atomic(vaddr);
  66        } else {
  67                if (!kdump_buf_page) {
  68                        printk(KERN_WARNING "Kdump: Kdump buffer page not"
  69                                " allocated\n");
  70                        kunmap_atomic(vaddr);
  71                        return -EFAULT;
  72                }
  73                copy_page(kdump_buf_page, vaddr);
  74                kunmap_atomic(vaddr);
  75                if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  76                        return -EFAULT;
  77        }
  78
  79        return csize;
  80}
  81
  82static int __init kdump_buf_page_init(void)
  83{
  84        int ret = 0;
  85
  86        kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  87        if (!kdump_buf_page) {
  88                printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  89                         " page\n");
  90                ret = -ENOMEM;
  91        }
  92
  93        return ret;
  94}
  95arch_initcall(kdump_buf_page_init);
  96