[Crash-utility] modules and data / bss initialization

[Dave Anderson]

Castor Fu wrote:

>
>
> Under linux 2.6 it seems that crash is not figuring out the locations
> of any sections of modules other than the text section.
>
> This means that things like 'sym modvar1' can find the correct location
> but 'p modvar1' does not work.
>
> I guess that there are a couple of possibilities here:
>
> 1.  if CONFIG_KALLSYMS is set, one could look through the sect_attrs
>      for each of the sections and initialize the segments.
>
> 2.  if CONFIG_KALLSYMS is not set, we would have to try to match
>        offsets of some variables from the object file with the existing offsets
>        in the kernel.
>
> Clearly [2]  is the 'better' solution because it doesn't
>       require CONFIG_KALLSYMS to be set, but it seems like more work.
>
> Has anyone done either of these yet?   If not does it seem like I've described the
> problem correctly?
>
>     Thanks,
>     castor

It's been years since that code has been tinkered with,
and since I don't debug much module code, I wasn't even
aware that there was a 2.6-only difference.  I thought that
the add-symbol-file operation would properly assign the
module's msymbols with the correct addresses for data
symbols, which it does do correctly for the text symbols.
(I think that's the issue with the "p" command, i.e., the
embedded gdb is still using the offset value from
the object file and failing...)

Anyway, you can still do a "whatis modvar1", get the data type,
and then either do a "struct" command with the address, or
come up with a cobbled-together gdb print command, right?

Dave

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