On Wed, 2009-09-09 at 11:57 +0530, Sachin Sant wrote:
> Steven Rostedt wrote:
> > I'm going through old email, and I found this. Do you still see this
> > error. I don't recall seeing it myself.
> >
> I can still recreate this with 31-rc9. When i enable tracing
> with function_graph i notice the following oops. This happens
> only once. Later if i try to enable/disable tracing i don't
> get this oops message. This behavior is observed only with
> function_graph. Other tracers work fine.
>
> Oops: Kernel access of bad area, sig: 11 [#1]
> SMP NR_CPUS=1024 NUMA pSeries
> Modules linked in: ipv6 fuse loop dm_mod sr_mod ehea ibmveth sg cdrom sd_mod
> crc_t10dif ibmvscsic scsi_transport_srp scsi_tgt scsi_mod
> NIP: c000000000008f30 LR: c000000000008f04 CTR: 80000000000f6d68
> REGS: c00000003e98f560 TRAP: 0300 Not tainted (2.6.31-rc9)
> MSR: 8000000000009032 <EE,ME,IR,DR> CR: 24000422 XER: 00000020
> DAR: 0000000000000008, DSISR: 0000000040000000
> TASK = c00000003e953b20[2483] 'irqbalance' THREAD: c00000003e98c000 CPU: 1
> GPR00: c000000000008f04 c00000003e98f7e0 d00000000117ed38 0000000000000000
> GPR04: 0000000000000000 0000000066000000 00000000000010bf 0000000000000000
> GPR08: 0000000000000000 800000010021bb40 00000000000000ff 800000010021bb60
> GPR12: 0000000000000002 c000000001032800 0000000000000000 ffffffffeffdff68
> GPR16: 00000fffa39fd6a0 00000fffa39e6c38 c00000003ebe9c38 fffffffffffff000
> GPR20: c00000002a6cf980 c00000003e98fdf8 c00000003e98fba8 00000fffa1740000
> GPR24: fffffffffffff000 8001000003000000 ffe0000000000000 0000000000000009
> GPR28: c00000003db40000 0000000000020000 d00000000117da78 c00000003e98f850
> NIP [c000000000008f30] .mod_return_to_handler+0x2c/0x64
> LR [c000000000008f04] .mod_return_to_handler+0x0/0x64
> Call Trace:
> [c00000003e98f7e0] [c00000002a6cf980] 0xc00000002a6cf980 (unreliable)
> [c00000003e98f850] [c000000000008f04] .mod_return_to_handler+0x0/0x64
> [c00000003e98f900] [c000000000008f04] .mod_return_to_handler+0x0/0x64
> [c00000003e98f9a0] [c000000000008f04] .mod_return_to_handler+0x0/0x64
> [c00000003e98fa30] [c000000000008ed0] .return_to_handler+0x0/0x34
> (.bad_page_fault+0xc8/0xe8)
> [c00000003e98fb30] [c000000000008ed0] .return_to_handler+0x0/0x34
> (handle_page_fault+0x3c/0x5c)
> [c00000003e98fc20] [c000000000008ed0] .return_to_handler+0x0/0x34
> (.ehea_h_query_ehea_port+0x74/0x9c [ehea])
> [c00000003e98fcd0] [c000000000008ed0] .return_to_handler+0x0/0x34
> (.ehea_get_stats+0xa0/0x1d0 [ehea])
> [c00000003e98fd80] [c000000000008ed0] .return_to_handler+0x0/0x34
> (.dev_get_stats+0x50/0xec)
> [c00000003e98fe30] [c000000000008ed0] .return_to_handler+0x0/0x34
> (.dev_seq_show+0x5c/0x140)
> Instruction dump:
> 4e800020 f881ffe0 f861ffe8 f841fff0 fbe1fff8 7c3f0b78 f821ff91 3c800000
> 60840000 788407c6 64840000 60840000 <e8440008> 48126375 60000000 7c6803a6
> ---[ end trace bb43efc994aed790 ]---
I'm looking at your back dump and this really bothers me. I did a
objdump -dr arch/powerpc/kernel/entry_64.o and this is what I have:
0000000000000968 <.mod_return_to_handler>:
968: f8 81 ff e0 std r4,-32(r1)
96c: f8 61 ff e8 std r3,-24(r1)
970: f8 41 ff f0 std r2,-16(r1)
974: fb e1 ff f8 std r31,-8(r1)
978: 7c 3f 0b 78 mr r31,r1
97c: f8 21 ff 91 stdu r1,-112(r1)
980: 3c 80 00 00 lis r4,0
982: R_PPC64_ADDR16_HIGHEST ftrace_return_to_handler
984: 60 84 00 00 ori r4,r4,0
986: R_PPC64_ADDR16_HIGHER ftrace_return_to_handler
988: 78 84 07 c6 rldicr r4,r4,32,31
98c: 64 84 00 00 oris r4,r4,0
98e: R_PPC64_ADDR16_HI ftrace_return_to_handler
990: 60 84 00 00 ori r4,r4,0
992: R_PPC64_ADDR16_LO ftrace_return_to_handler
994: e8 44 00 08 ld r2,8(r4)
998: 48 00 00 01 bl 998 <.mod_return_to_handler+0x30>
998: R_PPC64_REL24 .ftrace_return_to_handler
99c: 60 00 00 00 nop
9a0: 7c 68 03 a6 mtlr r3
The bug happened at mod_return_to_handler+0x2c which is 994 above. Your
reg dump shows r4 is 0, and worse yet, looking at the code:
4e800020 f881ffe0 f861ffe8 f841fff0 fbe1fff8 7c3f0b78 f821ff91 3c800000
60840000 788407c6 64840000 60840000 <e8440008> 48126375 60000000
7c6803a6
The 64840000 60840000 shows that the linker never resolved the address
to ftrace_return_to_handle??
Something is totally messed up here.
-- Steve
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