arch/powerpc/kernel/crash_dump.c

   1 /*
   2  * Routines for doing kexec-based kdump.
   3  *
   4  * Copyright (C) 2005, IBM Corp.
   5  *
   6  * Created by: Michael Ellerman
   7  *
   8  * This source code is licensed under the GNU General Public License,
   9  * Version 2.  See the file COPYING for more details.
  10  */
  11
  12 #undef DEBUG
  13
  14 #include <asm/kdump.h>
  15 #include <asm/lmb.h>
  16 #include <asm/firmware.h>
  17
  18 #ifdef DEBUG
  19 #include <asm/udbg.h>
  20 #define DBG(fmt...) udbg_printf(fmt)
  21 #else
  22 #define DBG(fmt...)
  23 #endif
  24
  25 static void __init create_trampoline(unsigned long addr)
  26 {
  27         /* The maximum range of a single instruction branch, is the current
  28          * instruction's address + (32 MB - 4) bytes. For the trampoline we
  29          * need to branch to current address + 32 MB. So we insert a nop at
  30          * the trampoline address, then the next instruction (+ 4 bytes)
  31          * does a branch to (32 MB - 4). The net effect is that when we
  32          * branch to "addr" we jump to ("addr" + 32 MB). Although it requires
  33          * two instructions it doesn't require any registers.
  34          */
  35         create_instruction(addr, 0x60000000); /* nop */
  36         create_branch(addr + 4, addr + PHYSICAL_START, 0);
  37 }
  38
  39 void __init kdump_setup(void)
  40 {
  41         unsigned long i;
  42
  43         DBG(" -> kdump_setup()\n");
  44
  45         for (i = KDUMP_TRAMPOLINE_START; i < KDUMP_TRAMPOLINE_END; i += 8) {
  46                 create_trampoline(i);
  47         }
  48
  49         create_trampoline(__pa(system_reset_fwnmi) - PHYSICAL_START);
  50         create_trampoline(__pa(machine_check_fwnmi) - PHYSICAL_START);
  51
  52         DBG(" <- kdump_setup()\n");
  53 }