[lttng-dev] LD_PRELOAD applications using lttng-ust-pthread

Genevieve Bastien gbastien+lttng at versatic.net
Tue Jan 9 15:34:18 UTC 2018

Hi Majid,

See the documentation here:
http://lttng.org/docs/v2.10/#doc-using-lttng-ust-with-daemons and
http://lttng.org/docs/v2.10/#doc-liblttng-ust-fd. Firefox requires at
least one of those extra libraries to be preloaded, the one for fork I

I recall trying to trace firefox with lttng-cyg-profile without much
success. Without the liblttng-ust-fork.so preloaded, my tabs had
segfaults. But when I tried with both libraries, it seemed there was a
conflict between cyg-profile and the other preloaded libraries, I don't
remember exactly what happened. Maybe you won't have this problem with

I hope this helps,


On 2018-01-08 10:35 PM, Majid Rezazadeh wrote:
> Hi all
> I am using lttng-ust-libc-wrapper for instrumenting some calls to libc
> for some applications like Firefox and Chrome, but I receive
> "Segmentation fault (core dumped)". I compile lttng-ust-pthread.c (gcc
> -fPIC -shared  -o test.so lttng-ust-pthread.c -ldl) and then I use
> "LD_PRELOAD=test.so firefox" but I receive segmentation fault (I have
> exported LD_LIBRARY_PATH to the absolute path of test.so file). I
> found out that when I replace tracepoints with printf in
> lttng_ust_pthread.c, I receive no error. It seems that hooking
> tracepoints in this wrapper makes some problems. Do you have any idea
> in this regard?
> Thanks
> Majid
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> lttng-dev at lists.lttng.org
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