Re: Trouble with installation of systemTap on linux-image-3.19.0-25-generic

[David Smith <dsmith at redhat dot com>]

On 09/08/2016 09:05 PM, FOPA Leon constantin wrote:
> Hi,
> 
> After successfully install systemtap3.0 (./configure; make; make install)
> on a linux-image-3.19.0.25-generic (with its debug kernel image), I try
> to test if everything gone fine. However running the following
> helo-world command neither return and error nor the expected result
> 
> sudo stap -e 'probe kernel.function("sys_open") {log("hello world")
> exit()}'
> 
> Instead, It return a warning
> 
> WARNING: probe
> kernel.function("SyS_open@/build/linux-OdodyZ/linux-3.19.0/fs/open.c:1028")
> (address 0xffffffff811f3e80) registration error (rc -84)
> 
> I Can not tell if everything is fine or not, since I was expected the
> "Hello world" message, which never appear.
> 
> What is happening here and Is there a way out from this ?

Error 84 is EILSEQ - 'Illegal byte sequence'. That's an error that the
kernel is giving systemtap when trying to put the probe at the address
systemtap calculated.

What architecture are you on? What kprobes flags do you have on in your
kernel? In my fedora kernel, I see the following:

CONFIG_KPROBES=y
CONFIG_KPROBES_ON_FTRACE=y
CONFIG_HAVE_KPROBES=y
CONFIG_HAVE_KPROBES_ON_FTRACE=y
CONFIG_KPROBE_EVENT=y
# CONFIG_KPROBES_SANITY_TEST is not set

Here's a couple more things to try. First, let's try the simplest
possible script:

# stap -e 'probe begin { log("hello world"); exit() }'

Let's try your script, but use dwarfless-kprobes:

# stap -e 'probe kprobe.function("sys_open") { log("hello world"); exit() }'

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
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