Geeky PL/SQL tracer/profiler : First step

This blog post is about how to extend our capabilities to trace and profile PL/SQL code.It’s primarily motivated by few tweets from Franck Pachot and of course because it’s FUN !

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So in the first part of this series we are going to answer to this questions : Can we map those underling function to the source PL/SQL object and line number ? Can we obtain a full trace ? Of course yes otherwise there will be no blog post :p

TEST ENV : oracle 12.2.0.1/OEL6/UEK4 /PLSQL_CODE_TYPE=INTERPRETED/systemtap [Workaround for systemtap issue : Oracle Tracing [registration error (rc 0) !]

Whenever an exception is raised in our PL/SQL code or when requesting a dump of an ERROR STACK we can track the actual line executed .

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So it seem that there is a way to revert back to source code line number and PL/SQL object from the PL/SQL bytecode.Armed with the PIN TOOLS debugtrace.so i was able to identify the secret weapon and it’s named pfrln0lookup ! 

Reverse engineering this function seem quite complex so i decided to use it as it’s.

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This function when executed will return the actual line number in HEX. The two parameter that are important here are KGLHDADR of the actual pl/sql object and the bytecode offset  (Al least it seem to be).

The second step is how to extract those parameters from the code ! Few days later  :p here is a prototype (Far from being complete) of the geeky PL/SQL tracer coded as a systemtap  script:

Pl/SQL code to trace :

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Extract from the output of the geeky tracer :(Tracing exec system.profile_me; [Don’t create object in the system schema :p])

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Stay tuned more to come !

That’s it 😀

DOWNLOAD :

 

 

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