arch/i386/kernel/crash_dump.c

   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
  14 static 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  */
  33 ssize_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
  61 static 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 }
  74 arch_initcall(kdump_buf_page_init);