Date: Fri, 29 Oct 1999 14:25:43 -0400 From: Greg Lehey <grog@lemis.com> To: Robert Watson <robert+freebsd@cyrus.watson.org>, FreeBSD Hackers <hackers@FreeBSD.ORG>, committers@mojave.worldwide.lemis.com Subject: Re: gdb and kld symbols -- how to (and handbook is outdated) Message-ID: <19991029142543.26735@mojave.worldwide.lemis.com> In-Reply-To: <Pine.BSF.3.96.991029090302.35544A-100000@fledge.watson.org>; from Robert Watson on Fri, Oct 29, 1999 at 09:05:15AM -0400 References: <Pine.BSF.3.96.991029090302.35544A-100000@fledge.watson.org>
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On Friday, 29 October 1999 at 9:05:15 -0400, Robert Watson wrote:
>
> I've mostly debugged kernel modules running as lkm's, but decided to start
> up my debugger on code in a kld a couple of days, and needless to say the
> procedure is different :-). And unfortunately, also not documented in the
> handbook online, which still talks about lkms. Any suggestions? It is
> presumably still add-symbol-file, but with a different offset?
>
> Also, it might be desirable to either extend the handbook to also talk
> about klds, or to replace it with a kld page.
This questions qualifies as "in-depth technical", so I'm moving it to
-hackers. If you're not signed up there, you should be. I'm also
copying -committers because it's probably of interest there.
The object you need is in /modules. For example, to debug the Linux
kld, you need to load the symbols from /modules/linux.ko. That's the
easy part.
The difficult part is to find the base address. I have this in
/usr/src/sys/modules/vinum/.gdbinit.vinum.paths:
define asf
set $file = linker_files.tqh_first
set $found = 0
while ($found == 0)
if (*$file->filename == 'v')
set $found = 1
else
set $file = $file->link.tqe_next
end
end
shell /usr/bin/objdump --section-headers /modules/vinum.ko | grep ' .text' | awk '{print "add-symbol-file /modules/vinum.ko \$file->address+0x" $4}' > .asf
source .asf
end
This goes through an internal kernel list and looks for a module name
which begins with 'v'; you'll need to change the first "if" statement
to something which uniquely matches your kld. The rest (modulo file
names, which I have omitted here) should stay the same. There's also
more information in vinum(4).
Greg
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