[Crash-utility] ppc: fix backtrace problem when NT_PRSTATUS was not saved

[Dave Anderson]

----- Original Message -----
> Hi Dave,
> 
> I've reworked patch about ppc "bt" problem discussed in
>  https://www.redhat.com/archives/crash-utility/2012-June/msg00029.html
> 
> A patch is now getting to work only for ppc targets,
> and notes are relocatecd in first ppc's "bt", not in
> initialization-time.
> 
> And I've tested both "bt" diskdump by makedumpfile and netdump by
> /proc/vmcore with patched kernel like
> void crash_save_cpu(struct pt_regs *regs, int cpu)
>         if ((cpu % 2))
>                 return;
> 
> I was worried about beeing able to catch all of non-contiguous NT_PRSTATUS
> notes, alternate with invalid odd notes in every process well,
> so I modified test case this time (that's no problem, everything OK).
> 
> [After initialization: notes are not relocated yet]
> crash> help -D | grep notes
>   num_prstatus_notes: 4
>            notes_buf: 107a3518
>             notes[0]: 107a3518
>             notes[1]: 107a3638
>             notes[2]: 107a3758
>             notes[3]: 107a3878
> 
> [Relocate in first bt(only once) and display correctly]
> crash> bt
> PID: 1000   TASK: eb0cf800  CPU: 4   COMMAND: "bash"
> bt: WARNING: cpu#1: not saved crash_notes
> bt: WARNING: cpu#3: not saved crash_notes
> bt: WARNING: cpu#5: not saved crash_notes
> bt: WARNING: cpu#7: not saved crash_notes
> 
> R0:  00000001   R1:  ea11be60   R2:  eb0cf800   R3:  00000063
> R4:  00000000   R5:  ffffffff   R6:  c043ba2c   R7:  00000000
> R8:  00008000   R9:  00000000   R10: 00000000   R11: ea11be70
> R12: 28242444   R13: 100b8448   R14: 100b07b8   R15: 100b0894
> R16: 00000000   R17: 00000000   R18: 00000000   R19: 1006d270
> R20: 00000000   R21: 100f02e0   R22: 00000000   R23: 00000001
> R24: c08f1ac8   R25: 00029002   R26: c08f1bac   R27: c08d0000
> R28: 00000000   R29: c09ada48   R30: 00000063   R31: ea11be60
> NIP: c0423378   MSR: 00021002   OR3: c09ada48   CTR: c0423344
> LR:  c0423d8c   XER: 00000000   CCR: 28242444   MQ:  00008000
> DAR: 00000000 DSISR: 00800000        Syscall Result: ea11be60
>  NIP [00000000c0423378] sysrq_handle_crash
>  LR  [00000000c0423d8c] __handle_sysrq
> 
>  => PC: c0423378 (sysrq_handle_crash+52) FP: ea11be60
>  #0 [ea11be60] sysrq_handle_crash at c0423378
>  #1 [ea11be70] __handle_sysrq at c0423d8c
>  #2 [ea11bea0] write_sysrq_trigger at c0423ed0
>  #3 [ea11beb0] proc_reg_write at c01a79a4
>  #4 [ea11bee0] vfs_write at c014ba44
>  #5 [ea11bf00] sys_write at c014bcd8
>  #6 [ea11bf40] ret_from_syscall at c0013834
>  syscall  [c00] exception frame:
> R0:  00000004   R1:  bfe54e00   R2:  48027f80   R3:  00000001
> R4:  4811d000   R5:  00000002   R6:  00000000   R7:  00000001
> R8:  00000000   R9:  00000000   R10: 00000000   R11: 00000200
> R12: 28242442   R13: 100b8448   R14: 100b07b8   R15: 100b0894
> R16: 00000000   R17: 00000000   R18: 00000000   R19: 1006d270
> R20: 00000000   R21: 100f02e0   R22: 1006b4d0   R23: 00000001
> R24: 100b0000   R25: 1009b474   R26: bfe54ec8   R27: 00000002
> R28: 0fefa400   R29: 4811d000   R30: 0fef9ff4   R31: 00000002
> NIP: 0fe61494   MSR: 0002f902   OR3: 00000001   CTR: 0fe06fec
> LR:  0fe07050   XER: 00000000   CCR: 28242444   MQ:  00000000
> DAR: 4811d000 DSISR: 00800000        Syscall Result: 00000000
> 
> [notes has been relocated: Counts num_prstatus_notes even if NULL]
> crash> help -D | grep notes
>   num_prstatus_notes: 8
>            notes_buf: 107a3518
>             notes[0]: 107a3518
>             notes[1]: 0
>             notes[2]: 107a3638
>             notes[3]: 0
>             notes[4]: 107a3758
>             notes[5]: 0
>             notes[6]: 107a3878
>             notes[7]: 0
> 
> Thanks,
> Toshi

OK, doing it that way looks reasonable, and safely segregated to PPC only.

Just two more suggestions -- first, please do me a favor by running
"make warn" prior to posting a patch, and fix these:

  $ make warn
  TARGET: X86_64
   CRASH: 6.0.8rc15
     GDB: 7.3.1

  cc -c -g -DX86_64  -DGDB_7_3_1  build_data.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector 
  cc -c -g -DX86_64  -DGDB_7_3_1  ppc.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector 
  cc -c -g -DX86_64  -DGDB_7_3_1  netdump.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector 
  netdump.c: In function 'get_netdump_regs_ppc':
  netdump.c:2603: warning: pointer targets in passing argument 2 of 'relocate_nt_prstatus_percpu_ppc' differ in signedness
  cc -c -g -DX86_64  -DGDB_7_3_1  diskdump.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector 
  diskdump.c:1061: warning: no previous prototype for ‘relocate_nt_prstatus_percpu_ppc’
  diskdump.c: In function 'get_diskdump_regs_ppc':
  diskdump.c:1103: warning: pointer targets in passing argument 2 of 'relocate_nt_prstatus_percpu_ppc' differ in signedness
  ...

Secondly, since your new relocate_nt_prstatus_percpu_ppc() and
verify_crash_note_in_kernel_ppc() functions are used for both
kdump ELF and compressed kdump formats, and since they are 
PPC-specific, can you just move the two functions into ppc.c?
All that should require is to #include elf.h.

Thanks,
  Dave