bdi2000 debugging

[Matej Kupljen]

Hi 

I am trying to debug a problem in a user space application
(X windows), which when the process exits, crashes the kernel.
---------------------------------------------------------------
Oops: Exception in kernel mode, sig: 4
NIP: 000003B4 XER: 00000000 LR: C002B540 SP: C3B8DD10 REGS: c3b8dc60
TRAP: 0700    Not tainted
MSR: 00081000 EE: 0 PR: 0 FP: 0 ME: 1 IR/DR: 00
TASK = c3b8c000[55] 'Xorg.strip' Last syscall: 146 
last math c36aa000 last altivec 00000000
GPR00: 00000000 C3B8DD10 C3B8C000 C3B8DD20 30105D0C 20000000 C3B8DDE0
00136DA8 
GPR08: 00136DA8 00000000 00000035 000081A4 24048424 1031688C C0200000
C3B8DDE0 
GPR16: C0200000 C3B7F3E0 00000000 0C3B80C5 00001032 03B8DD10 C002B580
00009032 
GPR24: 00000035 00000000 00000FCB C3B80C50 00136DA8 00000000 00000035
C3B80C10 
Call backtrace: 
C0200000 C002B540 C002BCE8 C0090A58 C0039B64 C0039DCC C0005A7C 
00000000 0FE20BFC 0FE29878 0FE29D1C 0FE29DE8 0FD7E354 0FD65D78 
00000000 
Oops: Exception in kernel mode, sig: 4
NIP: 000003B4 XER: 20000000 LR: 0FDF527C SP: C3BAFF40 REGS: c3baff50
TRAP: 0700    Not tainted
MSR: 00081000 EE: 0 PR: 0 FP: 0 ME: 1 IR/DR: 00
TASK = c3bae000[54] 'run_xorg.sh' Last syscall: 114 
last math c36aa000 last altivec 00000000
GPR00: 00000000 C3BAFF40 30012738 C3BAFF50 0FEF1C6C 20000000 00000000
7F7F0000 
GPR08: FFFFFFFD 00000000 1015E4CC 00000000 44000828 10094078 00000000
00000000 
GPR16: 00000000 00000000 00000005 7FFFFA20 00001032 03BAFF40 0FE49374
0000D032 
GPR24: 1009949C 00000000 00000003 00000000 7FFFFF8F 0FF0B59C 0FF09120
7FFFF8B0 
Call backtrace: 
C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 
C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 
C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 
C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 
C0005CC8 C0005CC8 C0005CC8 C0005CC8 C0005CC8 
---------------------------------------------------------------

And that goes on for every process running :-(

Something is overwriting memory in kernel space I guess.
Now, I have the BDI 2000 and I am trying to debug this, but until
now I was unsuccessful :-(

When I debug the kernel, the BDI prints this out in the telnet
interface:
- Target MBAR is 0xF0000000
- Target XLBA is 0x8000A366

I know what MBAR is, but what the XLBA is?
The problem is that while this value remains the same everything 
is fine. But sometimes it is set to 0x00000000 and then I cannot
use debugger anymore. I can make a few steps when this value 
is set to 0x0, but the "stepping" is done in completely unrelated
code. I first noticed this while stepping trough hc_found_ohci
function when the return 0 is executed. When I disabled the USB
support in my kernel I could use debugger to debug a kernel.
But is still does not work all the time, because the XLBA still 
gets set to 0!

I am using CVS version of DENX kernel version 2.4.25.

Has anybody seen this?

Maybe a tip how to debug this problem?

Best regards,
Matej