RE: userspace probe breakage with gcc 4.8 due to inablility to locate semaphore variable

[Mayuresh Kulkarni <mkulkarni at kcg dot com>]

Here is a program that fails for me. (With details about building, machine etc).  To elaborate from my last email, it is seemingly the attempt to access a local variable in the probe that fails. Does the following work for you?

Many thanks,
Mayuresh


#include <sdt.h>
#include <unistd.h>

void foo()
{
    volatile int f = 100;
    STAP_PROBE(Prod,foo);
}


int main()
{
    while(true)
    {
        sleep(1);
        foo();
    }
}

################################################
1) Building:
################################################
$ g++ --version | head -1 #gcc used by build
g++ (GCC) 4.8.2

$ /usr/bin/g++ --version | head -1   #native gcc
g++ (GCC) 4.4.6 20110731 (Red Hat 4.4.6-3)

$ rpm -qa | grep elfutils
elfutils-devel-0.152-1.el6.x86_64
elfutils-libs-0.152-1.el6.x86_64
elfutils-libelf-devel-0.152-1.el6.x86_64
elfutils-libelf-0.152-1.el6.x86_64
elfutils-0.152-1.el6.x86_64

$ uname -r
2.6.32-220.7.1.el6.x86_64

systemtap is not installed on build box. Only sdt.h and std-config.h from stap 1.6 (attached) are available on build box

$ g++ -O3 -g foo.cpp   -o /tmp/foo  //May need a -I to point to sdt.h

If I build with g++ -O3 -g -gdwarf-2, the probe works fine

#####################################################
2) Executing and probing on different box with same kernel and native gcc 4.6 (gcc 4.8 not installed on runtime box)
######################################################
$  /tmp/foo&
[1] 8213
$ sudo stap -g -e 'probe process("/tmp/foo").provider("Prod").mark("foo") { printf("f : %d\n",$f); }' -x 8213
semantic error: no match while resolving probe point process("/tmp/foo").provider("Prod").mark("foo")
Pass 2: analysis failed.  Try again with another '--vp 01' option.

$  gcc --version | head -1
gcc (GCC) 4.4.6 20110731 (Red Hat 4.4.6-3)

$ stap --version
Systemtap translator/driver (version 1.6/0.152 non-git sources)
Copyright (C) 2005-2011 Red Hat, Inc. and others
This is free software; see the source for copying conditions.
enabled features: AVAHI LIBRPM LIBSQLITE3 NSS BOOST_SHARED_PTR TR1_UNORDERED_MAP NLS

$ rpm -qa | grep systemtap
systemtap-runtime-1.6-5.el6_2.x86_64
systemtap-initscript-1.6-5.el6_2.x86_64
systemtap-1.6-5.el6_2.x86_64

$ rpm -qa | grep elfutils
elfutils-libelf-0.152-1.el6.x86_64
elfutils-libs-0.152-1.el6.x86_64
elfutils-0.152-1.el6.x86_64

$ uname -r
2.6.32-220.7.1.el6.x86_64









-----Original Message-----
From: Frank Ch. Eigler [mailto:fche@redhat.com]
Sent: Monday, April 20, 2015 3:07 PM
To: Mayuresh Kulkarni
Cc: 'systemtap@sourceware.org'
Subject: Re: userspace probe breakage with gcc 4.8 due to inablility to locate semaphore variable


mkulkarni wrote:
>
 [...]
> Meanwhile, in my setup, I have found out that the runtime box has
> native gcc 4.4 And the regression is because the build uses gcc 4.8
> (which uses dwarf4 by default)

Why do you think so?  stap works fine here on that version of gcc, and older, and newer.  Can you forward your full gcc/stap/elfutils/kernel versions, and perhaps a binary (compiled with your gcc 4.8) that was giving stap a hard time?


- FChE
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