[Crash-utility] Re: source line numbers and modules (on x86_64)
On Wed, Apr 30, 2008 at 8:21 PM, Dave Anderson <anderson(a)redhat.com> wrote:
Mike Snitzer wrote:
> On Wed, Apr 30, 2008 at 7:41 PM, Dave Anderson <anderson(a)redhat.com>
wrote:
>
>
> > Mike Snitzer wrote:
> >
> >
> >
> > > On Wed, Apr 30, 2008 at 6:43 PM, Dave Anderson
<anderson(a)redhat.com>
> > >
> > >
> >
>
>
>
> >
> > >
> > > > Anyway, there are no kernel patches applied to RHEL5 kernels
> > > > to make it work that I'm aware of. That being said, I
don't
> > > > have an answer as to why they don't work for modules on your
> > > > custom kernel (or why they don't work in RHEL4 kernels...).
> > > >
> > > >
> > > >
> > > >
> > > I configured my x86_64 kernel to be relocatable. Could this be the
> > > reason for modules' line number debug data being off? From:
> > > http://people.redhat.com/anderson/crash.changelog.html#4_0_4_5
> > >
> > > "Using /proc/kallsyms or a --reloc=[size] as a command line argument
> > > is similar to using a System.map file, in that it results in the loss
> > > of the use of line number debug data."
> > >
> > >
> > >
> > >
> > No, that particular issue only applies to the base kernel, and is
> > irrelevant with respect to modules.
> > (Note that the RHEL5 kernel is relocatable as well.)
> >
> >
>
> OK, yeah making the base kernel non-relocatable didn't help.
>
>
>
> > What you might confirm is whether you're getting any debuginfo data
when
> > you load the module? Are you sure that your modules are being built
with -g?
> >
> >
>
> How would I confirm that I'm getting debuginfo data when I 'mod -s
> ext3'? I'm using an spec file that is based heavily (at least
> relative to debuginfo) on the redhat kernel-2.6.spec but I'll have to
> verify that I'm building with -g...
>
> Mike
>
>
So your build procedure ends up with a kernel-debuginfo package that
contains a set of "split" <module-name>.ko.debug files?
Yes.
If you take the module filename displayed after the "mod
-s" is done,
and run it through "readelf -a", you'll see a .gnu_debuglink section.
My kernel's ext3.ko has:
[23] .gnu_debuglink PROGBITS 0000000000000000 00036558
0000000000000014 0000000000000000 0 0 4
which would appear fairly comparable to what the RHEL5 kernel's ext3.ko has:
[22] .gnu_debuglink PROGBITS 0000000000000000 00037418
0000000000000014 0000000000000000 0 0 4
That /lib/modules/<path-to>/module.ko module will have
a link to its partner in
/usr/lib/debug/lib/modules/<path-to>/module.ko.debug.
readelf -x $SECTION /lib/modules/<path-to>/ext3.ko shows that
.gnu_debuglink points to ext3.ko.debug as expected.
Given the "so far so good" nature of what you're helping me verify
here it still begs the question: so why doesn't it work on my
2.6.22.19 x86_64 kernel? ;)
Where does the line number debug data get stored in the
module.ko.debug? In my case the source comes up as
"include/linux/clocksource.h: 121" for all kernel modules' symbols.
Any further pointers would be greatly appreciated, thanks a lot for
your time already!
Mike