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/slab.h>
   9 #include <linux/errno.h>
  10 #include <linux/highmem.h>
  11 #include <linux/crash_dump.h>
  12
  13 #include <asm/uaccess.h>
  14
  15 static void *kdump_buf_page;
  16
  17 static 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  */
  50 ssize_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, KM_PTE0);
  66         } else {
  67                 if (!kdump_buf_page) {
  68                         printk(KERN_WARNING "Kdump: Kdump buffer page not"
  69                                 " allocated\n");
  70                         kunmap_atomic(vaddr, KM_PTE0);
  71                         return -EFAULT;
  72                 }
  73                 copy_page(kdump_buf_page, vaddr);
  74                 kunmap_atomic(vaddr, KM_PTE0);
  75                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  76                         return -EFAULT;
  77         }
  78
  79         return csize;
  80 }
  81
  82 static 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 }
  95 arch_initcall(kdump_buf_page_init);