Decoding Stack from kernel OOPS message

Tue Feb 13 06:47:32 EST 2018

2018-02-13 13:03 GMT+03:00 Denis Kirjanov <kirjanov at gmail.com>:
> On 2/13/18, Matwey V. Kornilov <matwey.kornilov at gmail.com> wrote:
>> Hi all,
>>
>> I have to following message in the logs. What I know is how to convert
>> 'Code' section to assembler or how to convert function/offset to source
>> code line. Now I wonder how to use stack and register dumps. Given I
>> have all debugging symbols for binary, it should be possible to map
>> function local variables to stack and registers (for this particular
>> stack-trace). Unfortunately, I have not found convenient way how to do
>> it using gdb.
>>
>
> Nope, you can do that by disassembling the caller functions and checking how
> parameters are passed (regs or stack).

Well, It is not clear to me. First, what is the purpose to dump the
stack? Second, when I use gdb with ordinary user-space applications,
then for every execution step I can do commands to print variables or
expressions. It is obvious that gdb has mapping between variables in
the source code and memory/register locations for any specific step.
Isn't this mapping derivable from debug info?

>
> It's easier to setup a kdump on a mchine and use crash utility for that.
>
>> [ 1733s] [ 1712.306911] Unable to handle kernel paging request at
>> virtual address 00ad7000
>> [ 1733s] [ 1712.322041] pgd = e7823740
>> [ 1733s] [ 1712.322043] [00ad7000] *pgd=67cc1003, *pmd=00000000
>> [ 1733s] [ 1712.322052] Internal error: Oops: a06 [#1] PREEMPT SMP ARM
>> [ 1733s] [ 1712.334631] Modules linked in: nls_iso8859_1 nls_cp437 vfat
>> fat virtio_rng virtio_blk virtio_mmio nf_conntrack_ipv6 nf_defrag_ipv6
>> nf_conntrack xfs libcrc32c crc32_arm_ce btrfs xor xor_neon zlib_deflate
>> raid6_pq reiserfs squashfs fuse dm_snapshot dm_bufio dm_mod dax
>> binfmt_misc loop sg
>> [ 1733s] [ 1712.334698] CPU: 2 PID: 32027 Comm: rpm Not tainted
>> 4.12.14-lp150.4-lpae #1
>> [ 1733s] [ 1712.334700] Hardware name: Generic DT based system
>> [ 1733s] [ 1712.334702] task: eab30000 task.stack: e837c000
>> [ 1733s] [ 1712.334712] PC is at memcpy+0x50/0x330
>> [ 1733s] [ 1712.334715] LR is at 0x7020000
>> [ 1733s] [ 1712.334718] pc : [<c0822b30>]    lr : [<07020000>]    psr:
>> 20030013
>> [ 1733s] [ 1712.334718] sp : e837dd8c  ip : 1f020000  fp : e837ddd4
>> [ 1733s] [ 1712.334720] r10: 00ad64e4  r9 : ffedeb1c  r8 : 33020000
>> [ 1733s] [ 1712.334721] r7 : 38020000  r6 : 18020000  r5 : 45020000  r4
>> : 36020000
>> [ 1733s] [ 1712.334723] r3 : 1d020000  r2 : 00000444  r1 : ffedeb3c  r0
>> : 00ad7000
>> [ 1733s] [ 1712.334726] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA
>> ARM  Segment user
>> [ 1733s] [ 1712.334729] Control: 30c5383d  Table: 67823740  DAC: dbadc0de
>> [ 1733s] [ 1712.334731] Process rpm (pid: 32027, stack limit = 0xe837c210)
>> [ 1733s] [ 1712.334733] Stack: (0xe837dd8c to 0xe837e000)
>> [ 1733s] [ 1712.334737] dd80:                            00000001
>> 000004e4 00000000 ffffe000 00ad7000
>> [ 1733s] [ 1712.334741] dda0: 00ad7000 c0833968 e83f46b8 eb4a1e6c
>> 00001000 e837def8 00001000 e837def0
>> [ 1733s] [ 1712.334744] ddc0: 00000000 ffede000 e837dde4 e837ddd8
>> c0833b60 c0833890 e837de24 e837dde8
>> [ 1733s] [ 1712.334747] dde0: c083c4c0 c0833b4c e837de24 e837ddf8
>> ffede000 efa4cd18 e837de14 e8ebf7f4
>> [ 1733s] [ 1712.334750] de00: ea070540 efa4cd18 00000614 e8ebf700
>> e837def8 00001000 e837de94 e837de28
>> [ 1733s] [ 1712.334753] de20: c05b6620 c083c334 ea028200 b689c000
>> 014000c0 00080001 e837df18 00000000
>> [ 1733s] [ 1712.334755] de40: 00000613 00000000 00000615 ea0705a8
>> 00a16fff 00000000 00000000 00000000
>> [ 1733s] [ 1712.334758] de60: ffffe000 00000000 ea028204 00000000
>> 00001000 e837def8 ea070540 e837df80
>> [ 1733s] [ 1712.334762] de80: 00000000 e837df10 e837ded4 e837de98
>> c05b6d58 c05b640c c10a764c ea070548
>> [ 1733s] [ 1712.334765] dea0: 00020000 00000000 00020000 00000000
>> ea070540 e837df80 00ad64e4 e837df80
>> [ 1733s] [ 1712.334768] dec0: 00000000 00000000 e837dee4 e837ded8
>> c06dd35c c05b6c34 e837df4c e837dee8
>> [ 1733s] [ 1712.334771] dee0: c063c458 c06dd324 00001000 c0686f78
>> 00ad64e4 00001000 00000000 00000000
>> [ 1733s] [ 1712.334774] df00: 00001000 e837def0 00000001 e837df18
>> ea070540 00000000 00614000 00000000
>> [ 1733s] [ 1712.334777] df20: 00000000 00000000 00000000 00000000
>> ffffe000 00001000 ea070540 00ad64e4
>> [ 1733s] [ 1712.334780] df40: e837df7c e837df50 c063db2c c063c380
>> 00000000 00000000 ea070540 ea070540
>> [ 1733s] [ 1712.334783] df60: 00ad64e4 00001000 c04360e8 e837c000
>> e837dfa4 e837df80 c063f000 c063da9c
>> [ 1733s] [ 1712.334786] df80: 00614000 00000000 00614000 00000000
>> 00000001 000000b4 00000000 e837dfa8
>> [ 1733s] [ 1712.334789] dfa0: c0435f20 c063ef88 00614000 00000000
>> 00000003 00ad64e4 00001000 00000000
>> [ 1733s] [ 1712.334792] dfc0: 00614000 00000000 00000001 000000b4
>> 00000614 00001000 00614000 b6f26d78
>> [ 1733s] [ 1712.334795] dfe0: b6f2522c be9be5f8 b6edaed8 b6ccdbe8
>> 60030010 00000003 00000000 00000000
>> [ 1733s] [ 1712.334808] [<c0822b30>] (memcpy) from [<c0833968>]
>> (__copy_to_user_memcpy+0xe4/0x18c)
>> [ 1733s] [ 1712.334814] [<c0833968>] (__copy_to_user_memcpy) from
>> [<c0833b60>] (arm_copy_to_user+0x20/0x34)
>> [ 1733s] [ 1712.334819] [<c0833b60>] (arm_copy_to_user) from
>> [<c083c4c0>] (copy_page_to_iter+0x198/0x414)
>> [ 1733s] [ 1712.334826] [<c083c4c0>] (copy_page_to_iter) from
>> [<c05b6620>] (do_generic_file_read+0x220/0x828)
>> [ 1733s] [ 1712.334834] [<c05b6620>] (do_generic_file_read) from
>> [<c05b6d58>] (generic_file_read_iter+0x130/0x184)
>> [ 1733s] [ 1712.334840] [<c05b6d58>] (generic_file_read_iter) from
>> [<c06dd35c>] (ext4_file_read_iter+0x44/0x58)
>> [ 1733s] [ 1712.334849] [<c06dd35c>] (ext4_file_read_iter) from
>> [<c063c458>] (__vfs_read+0xe4/0x130)
>> [ 1733s] [ 1712.334855] [<c063c458>] (__vfs_read) from [<c063db2c>]
>> (vfs_read+0x9c/0x164)
>> [ 1733s] [ 1712.334860] [<c063db2c>] (vfs_read) from [<c063f000>]
>> (SyS_pread64+0x84/0x9c)
>> [ 1733s] [ 1712.334867] [<c063f000>] (SyS_pread64) from [<c0435f20>]
>> (ret_fast_syscall+0x0/0x34)
>> [ 1733s] [ 1712.334872] Code: f5d1f05c f5d1f07c e8b151f8 e2522020
>> (e8a051f8)
>> [ 1733s] [ 1712.334906] ---[ end trace 9514fd2a41e5765d ]---
>>
>>
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>
>
> --
> Regards / Mit besten Grüßen,
> Denis

-- 
With best regards,
Matwey V. Kornilov