Re: debug 3th part module which oops the system

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On Wed, Jul 03, 2013 at 09:04:50AM -0400, Dave Anderson wrote:
> 
> 
> ----- Original Message -----
> > Hey there,
> > 
> > I'm trying to analyse the vmcore come from an oops caused by a module. The
> > module
> > comes from here:
> > 
> >     http://www.linuxforu.com/2011/01/understanding-a-kernel-oops
> > 
> > This web page wants to teach how to analyse kernel oops. It provided a
> > module named 'oops', which triggers a NULL pointer dereference in its
> > init function.
> > 
> > The problem is I cannot figure out how to use crash to analyse vmcore:
> > 
> > GNU gdb (GDB) 7.0
> > Copyright (C) 2009 Free Software Foundation, Inc.
> > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> > and "show warranty" for details.
> > This GDB was configured as "powerpc64-unknown-linux-gnu"...
> > 
> >       KERNEL: /usr/lib/debug/lib/modules/2.6.18-348.el5/vmlinux
> >     DUMPFILE: /var/crash/127.0.0.1-2013-07-01-04:43/vmcore
> >         CPUS: 20
> >         DATE: Mon Jul  1 04:38:49 2013
> >       UPTIME: 00:33:44
> > LOAD AVERAGE: 0.22, 0.18, 0.07
> >        TASKS: 482
> >     NODENAME: lawlp3.upt.austin.ibm.com
> >      RELEASE: 2.6.18-348.el5
> >      VERSION: #1 SMP Wed Nov 28 21:23:52 EST 2012
> >      MACHINE: ppc64  (3550 Mhz)
> >       MEMORY: 3.2 GB
> >        PANIC: "Oops: Kernel access of bad area, sig: 11 [#1]" (check log for
> >        details)
> >          PID: 5402
> >      COMMAND: "insmod"
> >         TASK: c0000000cfa35150  [THREAD_INFO: c0000000ce5d0000]
> >          CPU: 15
> >        STATE: TASK_RUNNING (PANIC)
> > 
> > crash> log
> > ... ....
> > oops: module license 'unspecified' taints kernel.
> > oops from the module
> > Unable to handle kernel paging request for data at address 0x00000000
> > Faulting instruction address: 0xd000000001460060
> > Oops: Kernel access of bad area, sig: 11 [#1]
> > SMP NR_CPUS=128 NUMA
> > Modules linked in: oops(PU) nfsd exportfs auth_rpcgss autofs4 hidp nfs
> > nfs_acl rfcomm l2cap bluetooth lockd sunrpc ip6t_REJECT xt_tcpudp
> > ip6table_filter ip6_tables x_tables be2iscsi ib_iser rdma_cm ib_addr ib_cm
> > ib_sa ib_mad iw_cm iscsi_tcp bnx2i cnic ipv6 xfrm_nalgo crypto_api uio
> > cxgb3i libcxgbi libiscsi_tcp libiscsi2 scsi_transport_iscsi2
> > scsi_transport_iscsi dm_multipath scsi_dh snd_powermac snd_seq_dummy
> > snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss
> > snd_mixer_oss snd_pcm snd_page_alloc snd_timer snd soundcore i2c_core
> > parport_pc lp parport sg iw_cxgb3 ib_core cxgb3 ibmveth 8021q dm_raid45
> > dm_message dm_region_hash dm_mem_cache dm_snapshot dm_zero dm_mirror dm_log
> > dm_mod lpfc ibmvfc scsi_transport_fc ibmvscsic sd_mod scsi_mod ext3 jbd
> > uhci_hcd ohci_hcd ehci_hcd
> > NIP: D000000001460060 LR: D000000001460050 CTR: 0000000000000004
> > REGS: c0000000ce5d39b0 TRAP: 0300   Tainted: P     ----  (2.6.18-348.el5)
> > MSR: 8000000000009032 <EE,ME,IR,DR>  CR: 24022482  XER: 00000006
> > DAR: 0000000000000000, DSISR: 0000000042000000
> > TASK = c0000000cfa35150[5402] 'insmod' THREAD: c0000000ce5d0000 CPU: 15
> > GPR00: D000000001460050 C0000000CE5D3C30 D00000000146C930 0000000000000000
> > GPR04: 8000000000001032 0000000000000000 0000000000000000 0000000000000000
> > GPR08: 0000000000000000 0000000000000000 C0000000015FBB68 0000000000000000
> > GPR12: 0000000000000000 C000000000570B80 0000000000000000 D0000000012B1850
> > GPR16: D0000000012B1810 D0000000014601B0 0000000000000000 0000000000000000
> > GPR20: 0000000000000028 D0000000012B0CE9 C0000000005A12E8 0000000000000029
> > GPR24: D0000000012A0000 000000000000002A C0000000CD6F5A80 C0000000CD6F5AB0
> > GPR28: C0000000005A18C8 D000000001460680 D00000000146C900 D000000001460680
> > NIP [D000000001460060] .my_oops_init+0x2c/0xd4 [oops]
> > LR [D000000001460050] .my_oops_init+0x1c/0xd4 [oops]
> > Call Trace:
> > [C0000000CE5D3C30] [C000000000098944] .sys_init_module+0x1a88/0x1d18
> > (unreliable)
> > [C0000000CE5D3E30] [C0000000000086A4] syscall_exit+0x0/0x40
> > Instruction dump:
> > 4e800020 7c0802a6 fbc1fff0 ebc28000 f8010010 f821ff81 e87e8008 4800002d
> > e8410028 39200000 38210080 38600000 <91290000> e8010010 ebc1fff0 7c0803a6
> >  <0>Sending IPI to other cpus...
> > crash> whatis my_oops_init
> > whatis: gdb request failed: whatis my_oops_init
> > crash> mod -s oops
> >      MODULE       NAME                     SIZE  OBJECT FILE
> > d000000001460680  oops                    18752  /lib/modules/2.6.18-348.el5/kernel/oops.ko
> > crash> whatis my_oops_init
> > int my_oops_init(void);
> > crash> dis -l .my_oops_init
> > <nothing outputed>
> > crash> sym -m oops
> > d000000001460000 MODULE START: oops
> > d000000001460000 (t) .my_oops_exit
> > d000000001460000 (t) .cleanup_module
> > d000000001460034 (t) .my_oops_init
> > d000000001460034 (t) .init_module
> > d000000001460130 (r) ____versions
> > d000000001460130 (r) __versions
> > d000000001460680 (D) __this_module
> > d000000001464910 (D) cleanup_module
> > d000000001464910 (d) my_oops_exit
> > d000000001464920 (D) init_module
> > d000000001464920 (d) my_oops_init
> > d000000001464940 MODULE END: oops
> > crash> bt
> > PID: 5402   TASK: c0000000cfa35150  CPU: 15  COMMAND: "insmod"
> > 
> >  R0:  d000000001460050    R1:  c0000000ce5d3c30    R2:  d00000000146c930
> >  R3:  0000000000000000    R4:  8000000000001032    R5:  0000000000000000
> >  R6:  0000000000000000    R7:  0000000000000000    R8:  0000000000000000
> >  R9:  0000000000000000    R10: c0000000015fbb68    R11: 0000000000000000
> >  R12: 0000000000000000    R13: c000000000570b80    R14: 0000000000000000
> >  R15: d0000000012b1850    R16: d0000000012b1810    R17: d0000000014601b0
> >  R18: 0000000000000000    R19: 0000000000000000    R20: 0000000000000028
> >  R21: d0000000012b0ce9    R22: c0000000005a12e8    R23: 0000000000000029
> >  R24: d0000000012a0000    R25: 000000000000002a    R26: c0000000cd6f5a80
> >  R27: c0000000cd6f5ab0    R28: c0000000005a18c8    R29: d000000001460680
> >  R30: d00000000146c900    R31: d000000001460680
> >  NIP: d000000001460060    MSR: 8000000000009032    OR3: c0000000005a13c0
> >  CTR: 0000000000000004    LR:  d000000001460050    XER: 0000000000000006
> >  CCR: 0000000024022482    MQ:  c0000000cd6f5ab0    DAR: 0000000000000000
> >  DSISR: 0000000042000000     Syscall Result: 0000000000000000
> >  NIP [d000000001460060] .init_module
> >  LR  [d000000001460050] .init_module
> > 
> >  #0 [c0000000ce5d3c30] .sys_init_module at c000000000098944
> >  #1 [c0000000ce5d3e30] syscall_exit at c0000000000086a4
> >  syscall  [c00] exception frame:
> >  R0:  0000000000000080    R1:  00000000ff91fb60    R2:  000000000fff8eb0
> >  R3:  0000000010020028    R4:  000000000001caf8    R5:  0000000010020018
> >  R6:  000000000000002d    R7:  fffffffffeff0000    R8:  000000000002ffe0
> >  R9:  0000000000000000    R10: 0000000000000000    R11: 0000000000000000
> >  R12: 0000000000000000    R13: 000000001001959c    R14: 0000000000000000
> >  R15: 0000000000000000    R16: 0000000000000000    R17: 0000000000000000
> >  R18: 0000000000000000    R19: 0000000000000000    R20: 0000000000000000
> >  R21: 0000000000000000    R22: 0000000000000000    R23: 0000000000000000
> >  R24: 000000000ffbf280    R25: 00000000ff91fdf0    R26: 0000000010020018
> >  R27: 00000000ff91ff05    R28: 0000000000020000    R29: 000000000001caf8
> >  R30: 0000000010020028    R31: 0000000000000003
> >  NIP: 000000000ff0496c    MSR: 000000000000d032    OR3: 0000000010020028
> >  CTR: 000000000ff04964    LR:  0000000010000bf8    XER: 0000000000000000
> >  CCR: 0000000044000484    MQ:  0000000002756c28    DAR: 000000001004002c
> >  DSISR: 0000000042000000     Syscall Result: 0000000000000000
> > 
> > crash>
> > 
> > as you can see, the 'bt' command says the problem is at '.init_module',
> > but in fact it should come from '.my_oops_init'. But 'dis -l
> > .my_oops_init' shows nothing. I cannot use crash to figure out which line
> > of source code caused the oops. But using gdb as being stated in the web page
> > I
> > can find the code line easily.
> > 
> > Please help. Thanks.
> 
> I'm not well-versed in ppc64, but the issue seems to be related
> to the fact that .my_oops_init and .init_module are both being
> assigned the same virtual address:
> 
> d000000001460034 (t) .my_oops_init
> d000000001460034 (t) .init_module
> 
> If you do an "nm -Bn" on the oops.ko file, do they show the same
> offset value?

Thanks, Dave. Looks like they have the same offset, both are zero:

$ nm -Bn oops.ko
                 U .printk
0000000000000000 T .cleanup_module
0000000000000000 T .init_module
0000000000000000 t .my_oops_exit
0000000000000000 t .my_oops_init
0000000000000000 r ____versions
0000000000000000 r __mod_srcversion29
0000000000000000 D __this_module
0000000000000000 D cleanup_module
0000000000000000 d my_oops_exit
0000000000000010 D init_module
0000000000000010 d my_oops_init
0000000000000028 r __module_depends
0000000000000038 r __mod_vermagic5

But why gdb isn't affected by the same offset?

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