Re: [Crash-utility] question about phys_base
----- Original Message -----
At 02/28/2012 04:52 PM, HATAYAMA Daisuke Wrote:
>>> In general, such characteristic should not be used. You
should prepare
>>> a solid interface. Even if using them, it should be limited to as
>>> workaround to avoid some issue.
>>>
>>> Why not use qemu's CPU state? Include it as note information with good
>>> name, and we can use it to distinguish which. Like:
>>>
>>> $ readelf -n vmcore
>>>
>>> Notes at offset 0x000001c8 with length 0x00000838:
>>> Owner Data size Description
>>> CORE 0x00000150 NT_PRSTATUS (prstatus structure)
>>> CORE 0x00000150 NT_PRSTATUS (prstatus structure)
>>> QEMU 0x00000557 Unknown note type: (0x00000000)
>>>
>>> Or QEMUCPUState is better?
>>
>> Good idea. I will try it, and hope gdb can also work.
>>
>
> Tools basically ignore unknown notes. Looking into gdb, it appears to
> ignore unknown information.
>
> static bfd_boolean
> elfcore_grok_note (bfd *abfd, Elf_Internal_Note *note)
> {
> const struct elf_backend_data *bed = get_elf_backend_data (abfd);
>
> switch (note->type)
> {
> default:
> return TRUE;
> <cut>
>
> You might need to add new command to output contents of new note if
> it's necessary.
My goal is:
1. gdb uses NT_PRSTATUS, and can work well
2. crash uses unknown notes, and can get phys_base from it.
Another question:
What is QEMUCPUState? I donot find its definition?
It's just the note's name character string. Either "QEMU",
"QEMUCPUState",
or whatever unique character string you prefer would suffice.
What note->type shoule be for "QEMU"? If we choose an
unused value, the
value may be used in the future.
Why not do the same thing as the "VMCOREINFO" note, and leave it
as an "illegal/unknown" type of 0::
$ cat /usr/include/elf.h
... [ cut ] ...
/* Legal values for note segment descriptor types for core files. */
#define NT_PRSTATUS 1 /* Contains copy of prstatus struct */
#define NT_FPREGSET 2 /* Contains copy of fpregset struct */
#define NT_PRPSINFO 3 /* Contains copy of prpsinfo struct */
...
$
$ readelf -a vmcore
... [ cut ] ...
Notes at offset 0x00000190 with length 0x00000f1c:
Owner Data size Description
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
VMCOREINFO 0x000003e4 Unknown note type: (0x00000000)
$
Dave