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Re: "No match for probe point" for syscall.open with tutorial example strace-open.stp


David Smith schrieb:
Fredy Neeser wrote:
Hi,

I am trying to use systemtap (20070818 snapshot) on an IA32 Core Duo system with
Fedora Core 5 and a kernel which I built from vanilla 2.6.18 sources.



(Note that I've never used systemtap with a self-built kernel, but I'll take a stab at this anyway.)


... stuff deleted ...

the next tutorial example

[root@mythen stap_tests]# stap -vvv strace-open.stp

gives "No match for probe point" for syscall.open:

SystemTap translator/driver (version 0.6/0.128 built 2007-08-23)
Copyright (C) 2005-2007 Red Hat, Inc. and others
This is free software; see the source for copying conditions.
Created temporary directory "/tmp/stapyFwODp"
Searched '/usr/local/share/systemtap/tapset/i686/*.stp', found 1
Searched '/usr/local/share/systemtap/tapset/*.stp', found 36
Searched '/usr/local/share/systemtap/tapset/LKET/*.stp', found 19
Pass 1: parsed user script and 56 library script(s) in 320usr/10sys/356real ms.
control symbols: kts: 0x0 kte: 0x0 stext: 0x0

This is very curious. those 3 control symbols shouldn't be 0: kts is '__kprobes_text_start', kte is '__kprobes_text_end', and stext is '_stext'. Can you grep for those symbols in /proc/kallsyms and see if you find them?


If you can't find /proc/kallsyms, you need to build your kernel with CONFIG_KALLSYMS. If you can find those symbols in /proc/kallsyms, I'd bet systemtap can't find your kernel's debuginfo.

Hope this helps.

Thanks for your thoughts.  The kernel is configured with
CONFIG_KALLSYMS=y
# CONFIG_KALLSYMS_ALL is not set
CONFIG_KALLSYMS_EXTRA_PASS=y

The symbols are there:
[fn@mythen ~]$ cat /proc/kallsyms | grep __kprobes_text_start
c02edf20 T __kprobes_text_start
[fn@mythen ~]$ cat /proc/kallsyms | grep __kprobes_text_end
c02efb87 T __kprobes_text_end
[fn@mythen ~]$ cat /proc/kallsyms | grep _stext
c0100294 T _stext

Hmm ... I will also try on another machine.

Cheers,
Fredy.


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