[lttng-dev] get function names with lttng-ust-cyg-profile

[Matthew Khouzam]

Hi,

You have the pointers that are traced. Babeltrace is doing exactly what it should as far as I know.

You could use the command 'nm' to get your symbols and look them up. I am sure Babeltrace can do this from a python level. You could also use a GUI based trace viewer to get the information.

Hope that helps.
Matthew
________________________________
From: lttng-dev <lttng-dev-bounces at lists.lttng.org> on behalf of Liu, Changcheng via lttng-dev <lttng-dev at lists.lttng.org>
Sent: Tuesday, June 23, 2020 10:37 AM
To: lttng-dev at lists.lttng.org <lttng-dev at lists.lttng.org>
Cc: changcheng.liu at intel.com <changcheng.liu at intel.com>
Subject: [lttng-dev] get function names with lttng-ust-cyg-profile

Hi all,
   I'm trying to use lttng-ust-cyg-profile to trace program.
   Does anyone know how to get function names and offset through lttng-ust-cyg-profile?

   In below example, the babeltrace could only get the function entry/exit value.
   1. Source program: instrument.c
         1 #include <stdio.h>
         2
         3 int add3(int val) {
         4         return val + 3;
         5 }
         6
         7 int main(int argc, char **argv) {
         8     int x = 4;
         9
        10     puts("Press Enter to continue...");
        11     getchar();
        12
        13     x = add3(x);
        14
        15     return 0;
        16 }

   2. build source code:
        $ gcc -g -finstrument-functions instrument.c -o instrument

   3. run program:
       $ LD_PRELOAD=/usr/lib/x86_64-linux-gnu/liblttng-ust-cyg-profile.so ./instrument

   4. start trace process:
       trace at trace:~/cc$ sudo lttng create instrument
       Session instrument created.
       Traces will be output to /root/lttng-traces/instrument-20200623-222917

       trace at trace:~/cc$ sudo lttng enable-channel user_func_trace --userspace
       UST channel user_func_trace enabled for session instrument

       trace at trace:~/cc$ sudo lttng enable-event --userspace lttng_ust_cyg_profile:func_entry --channel user_func_trace
       UST event lttng_ust_cyg_profile:func_entry created in channel user_func_trace
       trace at trace:~/cc$ sudo lttng enable-event --userspace lttng_ust_cyg_profile:func_exit --channel user_func_trace
       UST event lttng_ust_cyg_profile:func_exit created in channel user_func_trace

       trace at trace:~/cc$ sudo lttng start
       Tracing started for session instrument

       trace at trace:~/cc$ sudo lttng destroy
       Destroying session instrument..
       Session instrument destroyed

       trace at trace:~/cc$ sudo babeltrace /root/lttng-traces/instrument-20200623-222917
       [22:29:55.388607059] (+?.?????????) trace lttng_ust_cyg_profile:func_entry: { cpu_id = 2 }, { addr = 0x5625C88B01A9, call_site = 0x5625C88B0237 }
       [22:29:55.388612293] (+0.000005234) trace lttng_ust_cyg_profile:func_exit: { cpu_id = 2 }, { addr = 0x5625C88B01A9, call_site = 0x5625C88B0237 }
       [22:29:55.388613215] (+0.000000922) trace lttng_ust_cyg_profile:func_exit: { cpu_id = 2 }, { addr = 0x5625C88B01EE, call_site = 0x7FE40BD5C0B3 }

B.R.
Changcheng
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