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 /* Stores the physical address of elf header of crash image. */
  18 unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
  19
  20 static inline bool is_crashed_pfn_valid(unsigned long pfn)
  21 {
  22 #ifndef CONFIG_X86_PAE
  23         /*
  24          * non-PAE kdump kernel executed from a PAE one will crop high pte
  25          * bits and poke unwanted space counting again from address 0, we
  26          * don't want that. pte must fit into unsigned long. In fact the
  27          * test checks high 12 bits for being zero (pfn will be shifted left
  28          * by PAGE_SHIFT).
  29          */
  30         return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
  31 #else
  32         return true;
  33 #endif
  34 }
  35
  36 /**
  37  * copy_oldmem_page - copy one page from "oldmem"
  38  * @pfn: page frame number to be copied
  39  * @buf: target memory address for the copy; this can be in kernel address
  40  *      space or user address space (see @userbuf)
  41  * @csize: number of bytes to copy
  42  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  43  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  44  *      otherwise @buf is in kernel address space, use memcpy().
  45  *
  46  * Copy a page from "oldmem". For this page, there is no pte mapped
  47  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  48  *
  49  * Calling copy_to_user() in atomic context is not desirable. Hence first
  50  * copying the data to a pre-allocated kernel page and then copying to user
  51  * space in non-atomic context.
  52  */
  53 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  54                                size_t csize, unsigned long offset, int userbuf)
  55 {
  56         void  *vaddr;
  57
  58         if (!csize)
  59                 return 0;
  60
  61         if (!is_crashed_pfn_valid(pfn))
  62                 return -EFAULT;
  63
  64         vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
  65
  66         if (!userbuf) {
  67                 memcpy(buf, (vaddr + offset), csize);
  68                 kunmap_atomic(vaddr, KM_PTE0);
  69         } else {
  70                 if (!kdump_buf_page) {
  71                         printk(KERN_WARNING "Kdump: Kdump buffer page not"
  72                                 " allocated\n");
  73                         kunmap_atomic(vaddr, KM_PTE0);
  74                         return -EFAULT;
  75                 }
  76                 copy_page(kdump_buf_page, vaddr);
  77                 kunmap_atomic(vaddr, KM_PTE0);
  78                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  79                         return -EFAULT;
  80         }
  81
  82         return csize;
  83 }
  84
  85 static int __init kdump_buf_page_init(void)
  86 {
  87         int ret = 0;
  88
  89         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  90         if (!kdump_buf_page) {
  91                 printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
  92                          " page\n");
  93                 ret = -ENOMEM;
  94         }
  95
  96         return ret;
  97 }
  98 arch_initcall(kdump_buf_page_init);