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 static inline bool is_crashed_pfn_valid(unsigned long pfn)
  20 {
  21 #ifndef CONFIG_X86_PAE
  22         /*
  23          * non-PAE kdump kernel executed from a PAE one will crop high pte
  24          * bits and poke unwanted space counting again from address 0, we
  25          * don't want that. pte must fit into unsigned long. In fact the
  26          * test checks high 12 bits for being zero (pfn will be shifted left
  27          * by PAGE_SHIFT).
  28          */
  29         return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
  30 #else
  31         return true;
  32 #endif
  33 }
  34
  35 /**
  36  * copy_oldmem_page - copy one page from "oldmem"
  37  * @pfn: page frame number to be copied
  38  * @buf: target memory address for the copy; this can be in kernel address
  39  *      space or user address space (see @userbuf)
  40  * @csize: number of bytes to copy
  41  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  42  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  43  *      otherwise @buf is in kernel address space, use memcpy().
  44  *
  45  * Copy a page from "oldmem". For this page, there is no pte mapped
  46  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  47  *
  48  * Calling copy_to_user() in atomic context is not desirable. Hence first
  49  * copying the data to a pre-allocated kernel page and then copying to user
  50  * space in non-atomic context.
  51  */
  52 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  53                                size_t csize, unsigned long offset, int userbuf)
  54 {
  55         void  *vaddr;
  56
  57         if (!csize)
  58                 return 0;
  59
  60         if (!is_crashed_pfn_valid(pfn))
  61                 return -EFAULT;
  62
  63         vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
  64
  65         if (!userbuf) {
  66                 memcpy(buf, (vaddr + offset), csize);
  67                 kunmap_atomic(vaddr, KM_PTE0);
  68         } else {
  69                 if (!kdump_buf_page) {
  70                         printk(KERN_WARNING "Kdump: Kdump buffer page not"
  71                                 " allocated\n");
  72                         kunmap_atomic(vaddr, KM_PTE0);
  73                         return -EFAULT;
  74                 }
  75                 copy_page(kdump_buf_page, vaddr);
  76                 kunmap_atomic(vaddr, KM_PTE0);
  77                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  78                         return -EFAULT;
  79         }
  80
  81         return csize;
  82 }
  83
  84 static int __init kdump_buf_page_init(void)
  85 {
  86         int ret = 0;
  87
  88         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  89         if (!kdump_buf_page) {
  90                 printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  91                          " page\n");
  92                 ret = -ENOMEM;
  93         }
  94
  95         return ret;
  96 }
  97 arch_initcall(kdump_buf_page_init);