arch/x86/kernel/crash_dump_32.c

   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
  14 static void *kdump_buf_page;
  15
  16 /* Stores the physical address of elf header of crash image. */
  17 unsigned 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  */
  36 ssize_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
  65 static 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 }
  78 arch_initcall(kdump_buf_page_init);