Re: [PATCH 0/6] PowerPc 8xx TLB/MMU fixes

Rex Feany [off-list ref] wrote on 06/10/2009 00:42:18:

Thus spake Joakim Tjernlund (joakim.tjernlund@transmode.se):

quoted

quoted

I got this oops:

Unable to handle kernel paging request for data at address 0x00000000
Faulting instruction address: 0xc000e110
Oops: Kernel access of bad area, sig: 11 [#1]
MRV NM2
NIP: c000e110 LR: c000d520 CTR: 1006bf40
REGS: c2203dd0 TRAP: 0300   Not tainted  (2.6.32-rc3-00014-gcea49b0-dirty)
MSR: 00009032 <EE,ME,IR,DR>  CR: 44022422  XER: 20000000
DAR: 00000000, DSISR: c0000000
TASK = c21c18c0[69] 'rc.sysinit' THREAD: c2202000
GPR00: 00000401 c2203e80 c21c18c0 c2203f50 00000000 4000d032 00000000 00000000
GPR08: 10093eb4 00000000 00009032 c000d514 021c1ad0 10095c50 03ffb000 10006500
GPR16: 10006508 00000000 00000000 00000000 100a2fc8 021c4238 00000000 00000400
GPR24: c21a2700 00000002 40000000 00000000 00000000 c2203f50 00000000 00000011
NIP [c000e110] do_page_fault+0x44/0x5fc
LR [c000d520] handle_page_fault+0xc/0x80
Call Trace:
[c2203e80] [c000e58c] do_page_fault+0x4c0/0x5fc (unreliable)
[c2203f40] [c000d520] handle_page_fault+0xc/0x80
Instruction dump:
800300a0 7cba2b78 54170036 2f970400 7c9c2378 830200e0 54b6018c 40be000c
74ba4820 3ac00000 813d0080 3bc00000 <80a90000> 54a036be 2f80001f 40be0100
---[ end trace 99a4d88f7e2f1b60 ]---

this happens in do_page_fault becaose regs->nip is null, so

regs or regs->nip is NULL? Either one does not make sense
In any case it might be a secondary problem as DAR is NULL already when you
enter the page fault.

I assumed it was NIP because ... I'm not sure why. TRAP() above
dereferences regs, and that didn't fail, but I didn't see that until
now.

Yes, it is a bit strange though that the kernel isn't allowed to read from
NULL. Is that expected?

 Jocke