registration error (rc -22)

[Jim Keniston]

On Thu, 2008-09-18 at 21:47 +0530, Ananth N Mavinakayanahalli wrote:
> On Thu, Sep 18, 2008 at 10:57:08AM -0500, Paul Larson wrote:
> > I've run into a problem using systemtap with recent kernels.  In this case, 
> > I had a simple probe looking at a kernel module.  It worked fine in RHEL5.2 
> > stock kernel.  I updated to 2.6.27-rc6, and also updated to the latest git 
> > pull of systemtap.  Here's a simple test probe I'm running:
> > probe module("cxgb3").function("*") {
> >  print("got here\n")
> > }
> >
> > The module used doesn't seem to matter, I've tried several with the same 
> > result.  Here's the error I get:
> >
> > ERROR: probe 
> > module("cxgb3").function("get_regs@drivers/net/cxgb3/cxgb3_main.c:1366") 
> > registration error (rc -22)
> 
> That is -EINVAL which in all probablity is from register_kprobe(). There
> are a few cases where this can happen (probe insertion address not in
> the kernel text area, etc).
> 
> However, on certain architectures (eg., powerpc) we refuse to insert kprobes
> on certain instructions due to scary single-stepping issues.
> 
> Does dmesg give you more hints about the problem? Can you disassemble to
> find out what insruction is it that threw up the error?
> 
> Ananth

I'm seeing it, too.  I don't see any helpful kprobes messages.
Typically, -EINVAL means a bad address.  I wonder if something has
happened to stap's address calculations for module symbols.

Jim