[Crash-utility] Broken vtop on kernel 2.6.20?

[Guy Streeter]

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

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