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Re: results in a kernel string copy fault

Michael Obster wrote:

perhaps someone can give me a hint. First of all I tried also the snapshot 20070113 which did a complete system hang up. Using now the old 20061223 snapshot.

When I'm trying to use a
probe {
if (execname() != "staprun")
printf("%s: %s (%s) = ", execname(), name, argstr)
this results in a
ERROR: kernel string copy fault at 0x000081a4 near identifier '$filp' at /opt/systemtap/share/systemtap/tapset/nfs_proc.stp:1223:27
when the insmod is executed.

As I have seen, there is a change in this file (snapshot 20070113). But using the new snapshots hangs my system. Because I have no console, I don't see whether the kernel gives me an Oops.

The kernel we are using here is not a standard kernel. It is a special patched MontaVista Linux kernel with some additional patches for perfctr. The version is 2.6.10 with a backport patch from 2.6.13 for the kprobes interface compiled with gcc 3.4.3.

So I would be pleased for any hint!


I'm unsure of how to help you. I tried your script using CVS systemtap on RHEL4 x86_64 (2.6.9-42.0.3.EL) and beta RHEL5 x86 (2.6.18-1.2747.el5) and it worked on both (especially after adding a '\n' to the printf statement).

The only reference to '$filp' in probe is the following:

filename = __file_filename($filp)

The __file_filename function is defined in tapset/vfs.stp, and it looks reasonable to me.

I might start debugging this by creating your own copy of without the $filp reference and see if that works for you. If that works, I'd try looking at each pointer __file_filename has to dereference (file->f_dentry-> and see if they make sense.

David Smith
Red Hat
256.217.0141 (direct)
256.837.0057 (fax)

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