[Crash-utility] Broken vtop on kernel 2.6.20?

[David Anderson]

Guy Streeter wrote:

>On Tue, 2007-05-29 at 15:45 -0400, David Anderson wrote:
>
>>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?
>>
>
>On a 2.6.21 kernel with the -rt patchset, and crash-4.0-4.1, I see some
>of this:
>
>PID: 3093   TASK: f69793b0  CPU: 0   COMMAND: "mingetty"
>ps: cannot access user stack address: bf9fdf4c
>
>PID: 3094   TASK: f7f2abf0  CPU: 0   COMMAND: "mingetty"
>ps: cannot access user stack address: bfbb2f4c
>
>on i686 but I haven't seen it on x86_64.
>
>(Dave, I have these kernels, and systems with these kernels, you can
>access if you wish)
>
>--Guy
>
Ok -- tomorrow I'll request an RHTS RHEL5 i386 machine, and may come back to
you for the -rt kernel src.rpm.

In the meantime, if anybody else out there has any insight into any 
recent changes
in this area, please post your thoughts here...

Thanks,
   Dave