[Crash-utility] Broken vtop on kernel 2.6.20?

[David Anderson]

Alex Sidorenko wrote:

>Hi Dave,
>
>when I try to use 'vtop' for process pages on 2.6.20 kernel (Ubuntu/Feisty) on 
>x86 architecture, I get error messages about page table. The easiest way to 
>reproduce is to run 'ps -a' on a live kernel:
>
>
>PID: 0      TASK: c03a2440  CPU: 0   COMMAND: "swapper"
>ps: no user stack
>
>PID: 0      TASK: df838560  CPU: 1   COMMAND: "swapper"
>ps: no user stack
>
>PID: 1      TASK: df838a90  CPU: 1   COMMAND: "init"
>ps: read error: physical address: 7f2f0000  type: "page table"
>
>
>Running crash with -d8:
>
>PID: 1      TASK: df838a90  CPU: 1   COMMAND: "init"
><readmem: df838a90, KVADDR, "fill_task_struct", 1328, (ROE|Q), 8d2eac0>
><readmem: dfb71e40, KVADDR, "fill_mm_struct", 432, (ROE|Q), 8d8bf80>
>  GETBUF(128 -> 1)
>  FREEBUF(1)
>  GETBUF(128 -> 1)
>  FREEBUF(1)
>  GETBUF(128 -> 1)
>  FREEBUF(1)
>  GETBUF(128 -> 1)
>  FREEBUF(1)
>arg_start: bf991ecf arg_end: bf991ee1 (18)
>env_start: bf991ee1 env_end: bf991ff1 (272)
>  GETBUF(291 -> 1)
><readmem: dfb6f000, KVADDR, "pgd page", 4096, (FOE), 843cf90>
><readmem: dfb6f000, KVADDR, "pmd page", 4096, (FOE), 843cf90>
><readmem: 7f2f0000, PHYSADDR, "page table", 4096, (FOE), 843efa0>
>ps: read error: physical address: 7f2f0000  type: "page table"
>
>The same crash-4.0-4.1 works fine on live 2.6.15 kernel. Did the page table 
>layout change between 2.6.15 and 2.6.20 ?
>
>Regards,
>Alex
>
I don't know.  I don't have an x86 2.6.20 live system or dumpfile 
readily available,
so I'll need some help from the "outside world" here...

Anybody else know anything about this?

Dave