[lttng-dev] SIGSEGV __event_probe, C++ application (static linking)

[Mathieu Desnoyers]

----- On Jul 13, 2015, at 4:37 PM, Dilong Zheng <Dilong.Zheng at mitel.com> wrote: 

> Hi,

> I have instrumented a C++ application with user space tracepoints. When I run
> the application and do a: "lttng list -u" command, I am able to see all my
> available tracepoints for the application. However when I enable those user
> space tracepoints and then start the trace, a core gets dumped and examining
> the core file in gdb I see the following error:

> Program terminated with signal SIGSEGV, Segmentation fault.
> #0 0x00000000 in ?? ()

> ...

> (gdb) bt
> #0 0x00000000 in ?? ()
> #1 0x08dd1088 in __event_probe__mike___sem_wait_entry (__tp_data=0xef92d818)
> at /localhome/zhengd/override_mcd/System/SS_Inc/./sem_wrapper.h:67
> #2 0x08dd44d9 in __tracepoint_cb_mike___sem_wait_entry () at
> /localhome/zhengd/override_mc /System/SS_Inc/sem_wrapper.h:67
> #3 __wrap_sem_wait (sem=0xf43014c8) at
> /localhome/zhengd/override_mcd/System/System_Services/SysServices_Linux/SystemLinux.cpp:1877

> Contextual Information: I would like to trace all calls to sem_wait() in my
> application. I am simply using a wrapper sem_wait function where I can place
> tracepoint() calls. Here's what the sem_wait wrapper looks like:

> extern "C" int __real_sem_wait(sem_t*);

> extern "C" int __wrap_sem_wait(sem_t* sem)

> {

> tracepoint(mike, sem_wait_entry);

> int ret = __real_sem_wait(sem);

> tracepoint(mike, sem_wait_exit, ret);

> return ret;

> }

> Here is the TRACEPOINT_EVENT macro found in my tracepoint provider header file
> (which was generated using lttng-gen-tp command line utility):

> TRACEPOINT_EVENT(mike,

> sem_wait_entry,

> TP_ARGS(),

> TP_FIELDS()

> )

> And I am statically linking by using an existing CPP file (file with the
> __wrap_sem_wait() function) to create probes. I would just like to know any
> possible reasons why this error may be happening given the above mentioned
> circumstances and what I may be able to try in order to fix this.

Which UST version do you use ? Make sure you upgrade to latest, 
since we have fixed a similar segfault issue with probes compiled in 
C++ not so long ago. 

Thanks, 

Mathieu 

> Thanks,

> Dilong

> _______________________________________________
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> lttng-dev at lists.lttng.org
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-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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