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

[Dave Anderson]

Ken'ichi Ohmichi wrote:
> 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:

The patch looks good.  My dom0/i386 test kernel/dumpfiles all
backtrace OK because they are either early xen kernels that don't
have IRQ stacks, or later ones that by dumb luck don't have the
hardirq_ctx or softirq_ctx tasks set to the task being backtraced.

Thanks for catching this -- queued for the next release.

Dave

> 
>   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);
> _
> 
> 
> --
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