Re: on debugging loadable modules...

Michael K. Johnson (johnsonm@nigel.vnet.net)
Thu, 14 Mar 1996 08:29:21 -0500


"David S. Miller" writes:
>I was thinking about the problems we are seeing with debugging
>loadable modules since their text/data symbols are determined at run
>time. Maybe we should try to implement something like this:
>
[description elided]
>
>What do people think? This idea sucks doesn't it?

The idea doesn't suck, but the method has way too many points
of failure.

How about this simpler method: since insmod already has the ability
to produce a fixed-up symbol table on load, have its *default*
action be to write a file parallel to the module it loaded called
"<module-name>.symtab". Each time the module is loaded, a new
symtab file will be produced. If you can find the modules, you
can find the symtabs. A listing (probably of /lib/modules/<ver>/)
will show
bar.o
bar.symtab
foo.o
foo.symtab
etc.

Easy to use (no additional steps except for coding in modutils),
easy for ksymoops to exploit (just needs to know where to find
the modules; probably /lib/modules/<ver>/ unless it is given a
command-line argument to the contrary). There are really very
few points of failure here.

Any opinions? Did I leave out anything important?

michaelkjohnson