LXR linux/arch/x86/kernel/crash_dump

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *      Memory preserving reboot related code.
   4 *
   5 *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   6 *      Copyright (C) IBM Corporation, 2004. All rights reserved
   7 */
   8
   9#include <linux/slab.h>
  10#include <linux/errno.h>
  11#include <linux/highmem.h>
  12#include <linux/crash_dump.h>
  13
  14#include <linux/uaccess.h>
  15
  16static void *kdump_buf_page;
  17
  18static inline bool is_crashed_pfn_valid(unsigned long pfn)
  19{
  20#ifndef CONFIG_X86_PAE
  21        /*
  22         * non-PAE kdump kernel executed from a PAE one will crop high pte
  23         * bits and poke unwanted space counting again from address 0, we
  24         * don't want that. pte must fit into unsigned long. In fact the
  25         * test checks high 12 bits for being zero (pfn will be shifted left
  26         * by PAGE_SHIFT).
  27         */
  28        return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
  29#else
  30        return true;
  31#endif
  32}
  33
  34/**
  35 * copy_oldmem_page - copy one page from "oldmem"
  36 * @pfn: page frame number to be copied
  37 * @buf: target memory address for the copy; this can be in kernel address
  38 *      space or user address space (see @userbuf)
  39 * @csize: number of bytes to copy
  40 * @offset: offset in bytes into the page (based on pfn) to begin the copy
  41 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  42 *      otherwise @buf is in kernel address space, use memcpy().
  43 *
  44 * Copy a page from "oldmem". For this page, there is no pte mapped
  45 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  46 *
  47 * Calling copy_to_user() in atomic context is not desirable. Hence first
  48 * copying the data to a pre-allocated kernel page and then copying to user
  49 * space in non-atomic context.
  50 */
  51ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  52                               size_t csize, unsigned long offset, int userbuf)
  53{
  54        void  *vaddr;
  55
  56        if (!csize)
  57                return 0;
  58
  59        if (!is_crashed_pfn_valid(pfn))
  60                return -EFAULT;
  61
  62        vaddr = kmap_atomic_pfn(pfn);
  63
  64        if (!userbuf) {
  65                memcpy(buf, (vaddr + offset), csize);
  66                kunmap_atomic(vaddr);
  67        } else {
  68                if (!kdump_buf_page) {
  69                        printk(KERN_WARNING "Kdump: Kdump buffer page not"
  70                                " allocated\n");
  71                        kunmap_atomic(vaddr);
  72                        return -EFAULT;
  73                }
  74                copy_page(kdump_buf_page, vaddr);
  75                kunmap_atomic(vaddr);
  76                if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  77                        return -EFAULT;
  78        }
  79
  80        return csize;
  81}
  82
  83static int __init kdump_buf_page_init(void)
  84{
  85        int ret = 0;
  86
  87        kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  88        if (!kdump_buf_page) {
  89                printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  90                         " page\n");
  91                ret = -ENOMEM;
  92        }
  93
  94        return ret;
  95}
  96arch_initcall(kdump_buf_page_init);
  97