[Crash-utility] [PATCH] bt for i386 xen-dom0

[Ken'ichi Ohmichi]

Hi,

I found the problem that the subcommand "bt" cannot display the stack
of "bash" process on i386 xen-dom0 like the following:

  crash> bt
  PID: 3954   TASK: e502aaa0  CPU: 0   COMMAND: "bash"
  crash>


This problem happens if running "bt" for "swapper" process too:

  crash> bt
  PID: 0      TASK: c7ca5550  CPU: 1   COMMAND: "swapper"
  crash>


The cause is that bt->stackbase is overwritten in get_netdump_regs_x86()
even if the symbol "crash_kexec" is found. This patch fixes the overwritten
problem, and the result is the following:

  crash> bt
  PID: 3954   TASK: e502aaa0  CPU: 0   COMMAND: "bash"
   #0 [eb30ef34] crash_kexec at c043852a
   #1 [eb30ef78] write_sysrq_trigger at c0498b75
   #2 [eb30ef84] vfs_write at c0467a6d
   #3 [eb30ef9c] sys_write at c046805c
   #4 [eb30efb8] system_call at c0405348
      EAX: ffffffda  EBX: 00000001  ECX: b7c5d000  EDX: 00000002
      DS:  007b      ESI: 00000002  ES:  007b      EDI: b7c5d000
      SS:  007b      ESP: bfdb5eb8  EBP: bfdb5ed8
      CS:  0073      EIP: 00295402  ERR: 00000004  EFLAGS: 00000246
  crash>

  crash> bt
  PID: 0      TASK: c7ca5550  CPU: 1   COMMAND: "swapper"
   #0 [c10fdfac] xen_idle at c040321a
   #1 [c10fdfac] cpu_idle at c0403334
  crash>


Thanks
Ken'ichi Ohmichi 

Signed-off-by: Ken'ichi Ohmichi <oomichi at mxs.nes.nec.co.jp>
---
diff -rpuN crash-4.0-4.13.org/netdump.c crash-4.0-4.13/netdump.c
--- crash-4.0-4.13.org/netdump.c	2008-01-15 19:24:09.000000000 +0900
+++ crash-4.0-4.13/netdump.c	2008-01-15 19:31:52.000000000 +0900
@@ -2039,6 +2039,12 @@ next_sysrq:
 		return;
 	}
 
+	if (halt_eip && halt_esp) {
+        	*eip = halt_eip;
+        	*esp = halt_esp;
+		return;
+	}
+
 	if (panic)
 		return;
 
@@ -2064,12 +2070,6 @@ next_sysrq:
                 goto retry;
         }
 
-	if (halt_eip && halt_esp) {
-        	*eip = halt_eip;
-        	*esp = halt_esp;
-		return;
-	}
-
 	if (CRASHDEBUG(1))
 		error(INFO, 
     "get_netdump_regs_x86: cannot find anything useful (task: %lx)\n", bt->task);
_