arch/s390/kernel/crash_dump.c

   1 /*
   2  * S390 kdump implementation
   3  *
   4  * Copyright IBM Corp. 2011
   5  * Author(s): Michael Holzheu <holzheu@linux.vnet.ibm.com>
   6  */
   7
   8 #include <linux/crash_dump.h>
   9 #include <asm/lowcore.h>
  10
  11 /*
  12  * Copy one page from "oldmem"
  13  *
  14  * For the kdump reserved memory this functions performs a swap operation:
  15  *  - [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE] is mapped to [0 - OLDMEM_SIZE].
  16  *  - [0 - OLDMEM_SIZE] is mapped to [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE]
  17  */
  18 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  19                          size_t csize, unsigned long offset, int userbuf)
  20 {
  21         unsigned long src;
  22         int rc;
  23
  24         if (!csize)
  25                 return 0;
  26
  27         src = (pfn << PAGE_SHIFT) + offset;
  28         if (src < OLDMEM_SIZE)
  29                 src += OLDMEM_BASE;
  30         else if (src > OLDMEM_BASE &&
  31                  src < OLDMEM_BASE + OLDMEM_SIZE)
  32                 src -= OLDMEM_BASE;
  33         if (userbuf)
  34                 rc = copy_to_user_real((void __user *) buf, (void *) src,
  35                                        csize);
  36         else
  37                 rc = memcpy_real(buf, (void *) src, csize);
  38         return rc < 0 ? rc : csize;
  39 }