[Crash-utility] [Patch] linux-2.6.22 on i386

[Ken'ichi Ohmichi]

Hi Dave,

I found the problem that the crash utility fails during the initialization.
This problem happened on i386 linux-2.6.22 like the following:

  $ crash vmlinux vmcore
  
  crash 4.0-4.4
  Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007  Red Hat, Inc.
  Copyright (C) 2004, 2005, 2006  IBM Corporation
  Copyright (C) 1999-2006  Hewlett-Packard Co
  Copyright (C) 2005, 2006  Fujitsu Limited
  Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
  Copyright (C) 2005  NEC Corporation
  Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
  Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.
  This program is free software, covered by the GNU General Public License,
  and you are welcome to change it and/or distribute copies of it under
  certain conditions.  Enter "help copying" to see the conditions.
  This program has absolutely no warranty.  Enter "help warranty" for details.
  
  GNU gdb 6.1
  Copyright 2004 Free Software Foundation, Inc.
  GDB is free software, covered by the GNU General Public License, and you are
  welcome to change it and/or distribute copies of it under certain conditions.
  Type "show copying" to see the conditions.
  There is absolutely no warranty for GDB.  Type "show warranty" for details.
  This GDB was configured as "i686-pc-linux-gnu"...
  
  crash: invalid size request: 0  type: "__per_cpu_offset"
  $ 

The cause is that the array number of the symbol "__per_cpu_offset"
cannot be taken. In linux-2.6.21, i386's "__per_cpu_offset" is defined
in include/asm-generic/percpu.h like the following:

  extern unsigned long __per_cpu_offset[NR_CPUS];

But in linux-2.6.22, it is defined in include/asm-i386/percpu.h like
the following, and the array number is not described in the debugging
information.

  extern unsigned long __per_cpu_offset[];


Here is the patch for solving the problem. If the array number is not
taken, the crash utility assumes that it is  the defined value NR_CPUS.
Or, should get_array_length() be fixed to get the array number from
init/main.c ?


Thanks
Ken'ichi Ohmichi

--- crash-4.0-4.4.org/kernel.c	2007-07-21 04:19:23.000000000 +0900
+++ crash-4.0-4.4/kernel.c	2007-07-24 19:51:55.000000000 +0900
@@ -170,7 +170,7 @@ kernel_init()
 		else
 			i = get_array_length("__per_cpu_offset", NULL, 0);
 		get_symbol_data("__per_cpu_offset",
-			sizeof(long)*(i <= NR_CPUS ? i : NR_CPUS),
+			sizeof(long)*((i && (i <= NR_CPUS)) ? i : NR_CPUS),
 			&kt->__per_cpu_offset[0]);
                 kt->flags |= PER_CPU_OFF;
 	}
_