[Crash-utility] handling missing kdump pages in diskdump format

[Ken'ichi Ohmichi]

Hi Dave,

2007/04/03 09:40:56 -0400, Dave Anderson <anderson at redhat.com> wrote:
>> It is a good idea that "help -n" shows dump_level.
>>
>> I checked the code of diskdumputils-1.3.25, and I found the dumpfilter
>> command refers to diskdump->total_ram_blocks. In struct disk_dump_header,
>> there is no member not referred to by neither the crash utility or diskdumputils.
>> My proposal (changing total_ram_blocks for dump_level) was not good.
>>
>> I think it is enough that the member for dump_level is added into the
>> sub header of kdump (struct kdump_sub_header) only for kdump.
>> Is the change for diskdump necessary, too ?
>>
>>
>
>If this were to be restricted to kdump only, then it would be
>safe to add a field to the kdump_sub_header since it contains
>only one field.
>
>Whether it is necessary for diskdump is up to the diskdump
>maintainers to decide.  But if they want to do it, they would
>have to come up with different manner of adding it to the
>disk_dump_sub_header structure, because of the way
>that it's declared, i.e., using "long elf_regs" as a placeholder
>to describe the start of the processor-dependent register
>set.  They'd need to define a new disk_dump_sub_header
>version that alternatively would be used depending upon
>the header->version number.

We asked the diskdump developers (Indoh-san, Akiyama-san) how
to display diskdump's dump_level, and they said that changing
of file format is not necessary for displaying the dump_level.
And they gave us a good advice that the crash utility can get
diskdump's dump_level by using a symbol "dump_level" like the
following:

int get_dump_level(void)
{
        if (symbol_exists("dump_level")) {
                int dump_level;
                readmem(symbol_value("dump_level"), KVADDR, &dump_level,
                        sizeof(dump_level), "dump_level",
                        FAULT_ON_ERROR);
                return dump_level;

        }
        else
        ...

I think it is a good way because the crash utility can get diskdump's
dump_level of the existing dumpfile. I propose the following way for it.
Please let me know your opinion.

- If a symbol "dump_level" is present (diskdump), the dump_level is
  taken from a symbol "dump_level".
- Else if a dumpfile is kdump's and header_version is 1 or more, the
  dump_level taken from a new member "kdump_sub_header->dump_level".


Thanks
Ken'ichi Ohmichi