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

[Toshikazu Nakayama]

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
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