backtrace subcommand of crash command fails.

Issue

• Backtrace subcommand of crash command, bt -a, fails with the message "bt:cannot resolve stack trace".

• The problem occurs with vmcore gathered when oops occurs.

  crash> bt -a
  PID: 1598   TASK: ecf01030  CPU: 0   COMMAND: "insmod"
  bt: cannot resolve stack trace:
   #0 [ec4b1e54] crash_kexec at c0492512
   #1 [ec4b1ea8] oops_end at c080c052
   #2 [ec4b1ebc] no_context at c042e15d
   #3 [ec4b1ee0] bad_area at c042e3e6
   #4 [ec4b1ef4] do_page_fault at c080d6eb
   #5 [ec4b1f24] error_code (via page_fault) at c080b459
      EAX: 00000000  EBX: 00000000  ECX: c09df3ec  EDX: 00000000  EBP: f7e36000
      DS:  007b      ESI: f7e33060  ES:  007b      EDI: bfe2f838  GS:  00e0
      CS:  0060      EIP: f7e36011  ERR: ffffffff  EFLAGS: 00010246
   #6 [ec4b1f58] (null) at f7e36011
  bt: text symbols on stack:
      [ec4b1ea8] oops_end at c080c057
      [ec4b1ebc] no_context at c042e162
      [ec4b1ee0] bad_area at c042e3eb
      [ec4b1ef4] do_page_fault at c080d6f0
      [ec4b1f1c] do_page_fault at c080d300
      [ec4b1f24] error_code at c080b45b
      [ec4b1f68] do_one_initcall at c040303f
      [ec4b1f90] sys_init_module at c04898d4
      [ec4b1fb0] sysenter_do_call at c040985b
  bt: possible exception frames:
    KERNEL-MODE EXCEPTION FRAME AT ec4b1e54:
      EAX: 00000000  EBX: 00000000  ECX: c09df3ec  EDX: 00000000  EBP: f7e36000
      DS:  007b      ESI: f7e33060  ES:  007b      EDI: bfe2f838  GS:  00e0
      CS:  0060      EIP: f7e36011  ERR: ffffffff  EFLAGS: 00010246
    KERNEL-MODE EXCEPTION FRAME AT ec4b1f28:
      EAX: 00000000  EBX: 00000000  ECX: c09df3ec  EDX: 00000000  EBP: f7e36000
      DS:  007b      ESI: f7e33060  ES:  007b      EDI: bfe2f838  GS:  00e0
      CS:  0060      EIP: f7e36011  ERR: ffffffff  EFLAGS: 00010246
    USER-MODE EXCEPTION FRAME AT ec4b1fb4:
      EAX: 00000080  EBX: b7867008  ECX: 00023154  EDX: 09a88008
      DS:  007b      ESI: ffffffff  ES:  007b      EDI: bfe2f838
      SS:  007b      ESP: bfe2f7e0  EBP: bfe2f858  GS:  0033
      CS:  0073      EIP: 00bbd424  ERR: 00000080  EFLAGS: 00000282
  crash>
  

• Step to Reproduce:

1) Set up kdump.

2) Uncompress attached test.tar.gz.

3) Execute set.sh in the uncompressed "test" directory to build a kernel module, crash.ko which causes an oops.

4) Execute insmod crash.ko