semantic error: libdwfl failure (dwfl_linux_kernel_report_modules): Exec format error

semantic error: libdwfl failure (dwfl_linux_kernel_report_modules): Exec format error

[Esther Horbert]

Hi!

I got the following problem after installing systemtap while trying out 
the example from the webpage 
(http://sourceware.org/systemtap/wiki/SystemtapOnUbuntu).
We installed like described here: 
http://sourceware.org/systemtap/wiki/SystemtapOnDebian only installed 
the kernel manually (make install).
Does somebody know what this Exec format error means and how to fix it?


# stap -vvv -e 'probe kernel.function("sys_open") {log("hello world") 
exit()}'
Created temporary directory "/tmp/stapPOB94Z"
Searched '/usr/share/systemtap/tapset/2.6.20-oprofile/i686/*.stp', match 
count 0
Searched '/usr/share/systemtap/tapset/2.6.20-oprofile/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/2.6.20/i686/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/2.6.20/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/2.6/i686/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/2.6/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/i686/*.stp', match count 1
Searched '/usr/share/systemtap/tapset/*.stp', match count 33
Searched '/usr/share/systemtap/tapset/LKET/2.6.20-oprofile/i686/*.stp', 
match count 0
Searched '/usr/share/systemtap/tapset/LKET/2.6.20-oprofile/*.stp', match 
count 0
Searched '/usr/share/systemtap/tapset/LKET/2.6.20/i686/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/LKET/2.6.20/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/LKET/2.6/i686/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/LKET/2.6/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/LKET/i686/*.stp', match count 0
Searched '/usr/share/systemtap/tapset/LKET/*.stp', match count 19
Pass 1: parsed user script and 53 library script(s) in 
310usr/10sys/439real ms.
semantic error: libdwfl failure (dwfl_linux_kernel_report_modules): Exec 
format error
Ensure kernel debuginfo is installed
while: resolving probe point kernel.function("sys_open")
Pass 2: analyzed script: 0 probe(s), 0 function(s), 0 global(s) in 
10usr/0sys/36real ms.
Pass 2: analysis failed.  Try again with more '-v' (verbose) options.
Running rm -rf /tmp/stapPOB94Z

# dpkg -l libdw-dev elfutils
ii  elfutils                          0.123-3                           
collection of utilities to handle ELF objects
ii  libdw-dev                         0.123-3                           
library that provides access to the DWARF debug information


# ls -l /boot/vmlinux-$(uname -r)
-rwxr-xr-x 1 root root 43252479 2008-01-30 16:21 
/boot/vmlinux-2.6.20-oprofile


# zcat /proc/config.gz 
CONFIG_KALLSYMS=y
CONFIG_PROFILING=y
CONFIG_OPROFILE=y
CONFIG_KPROBES=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_INFO=y
...

Thanks!

Re: semantic error: libdwfl failure (dwfl_linux_kernel_report_modules): Exec format error

[Frank Ch. Eigler]

Esther Horbert <horbert@lfbs.RWTH-Aachen.DE> writes:

> [...]
> We installed like described here:
> http://sourceware.org/systemtap/wiki/SystemtapOnDebian only installed
> the kernel manually (make install).
> Does somebody know what this Exec format error means and how to fix it?
> [...]

> # stap -vvv -e 'probe kernel.function("sys_open") {log("hello world")
> exit()}'

I note there is no systemtap version identification printed here.
This means that your copy of systemtap is pretty old.

> [...]
> semantic error: libdwfl failure (dwfl_linux_kernel_report_modules):
> Exec format error
> Ensure kernel debuginfo is installed
> [...]

More modern versions give a more precise error message.

Your elfutils is also rather aged.  If you rebuild with a newer
systemtap (perhaps a cvs snapshot), consider also fetching a copy
of elfutils from http://sources.redhat.com/systemtap/ftp/elfutils
and using the "--with-elfutils=" bundling method.

>[...]
> # ls -l /boot/vmlinux-$(uname -r)
> -rwxr-xr-x 1 root root 43252479 2008-01-30 16:21 /boot/vmlinux-2.6.20-oprofile

That looks big enough to have all the dwarf data we could possibly want,
so you should not have to rebuild that nor reboot (if you're already running it).

- FChE