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Re: Can't set statement probe in self-built linux-4.4
- From: Chris Dunlop <chris at onthe dot net dot au>
- To: Josh Stone <jistone at redhat dot com>, David Smith <dsmith at redhat dot com>, "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: systemtap at sourceware dot org
- Date: Fri, 15 Jul 2016 09:18:53 +1000
- Subject: Re: Can't set statement probe in self-built linux-4.4
- Authentication-results: sourceware.org; auth=none
Hi Josh, Dave, Frank,
On Fri, Jul 15, 2016 at 03:29:54AM +1000, Chris Dunlop wrote:
> On Thu, Jul 14, 2016 at 10:20:56AM -0700, Josh Stone wrote:
> > On 07/14/2016 09:08 AM, Chris Dunlop wrote:
> > > On Fri, Jul 01, 2016 at 01:43:02PM +1000, Chris Dunlop wrote:
> > > Any ideas?
> >
> > $ grep DEBUG_INFO .config
> > CONFIG_DEBUG_INFO=y
> > # CONFIG_DEBUG_INFO_REDUCED is not set
> > CONFIG_DEBUG_INFO_SPLIT=y
> > CONFIG_DEBUG_INFO_DWARF4=y
> >
> > I think SPLIT is the problem. This puts all debuginfo into separate
> > .dwo objects, and then vmlinux itself only contains DW_AT_GNU_dwo_name
> > references from each CU.
> >
> > There's no dwo_name support at all in elfutils yet, thus stap doesn't
> > support it either.
> >
> > The function probe that you are getting is based only on the symbol
> > table, which is why you're not seeing any arguments either. And
> > statement probes aren't available at all without working debuginfo.
>
> OK, that sounds like it explains the problem.
>
> I'll remove the SPLIT and let you know...
Yup, that was it.
It's probably worth mentioning this on the "self built kernel" wiki page
until elfutils and therefore systemtap gain the support:
Using systemtap with self-built kernels
https://sourceware.org/systemtap/wiki/SystemTapWithSelfBuiltKernel
Thanks for your help!
Chris