[Crash-utility] Broken vtop on kernel 2.6.20?

Alex Sidorenko asid at hp.com
Tue May 29 19:20:47 UTC 2007


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

-- 
------------------------------------------------------------------
Alexandre Sidorenko             email: alexs at hplinux.canada.hp.com
Global Solutions Engineering:   Unix Networking
Hewlett-Packard (Canada)
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