<div dir="ltr">Hi Andy,<br><br>In the NotifyObjectEmitted method of our derived JITEventListener class we use the begin_symbol() iterator to walk the object's symbols looking for functions and only functions marked with ExternalLinkage seem to show up. I'm not sure how I would access the Dwarf info from within there, is there a way?<br>
<br>Thanks,<br>Andrew<br>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Nov 13, 2013 at 8:23 PM, Kaylor, Andrew <span dir="ltr"><<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div link="blue" vlink="purple" lang="EN-US">
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">From NotifyObjectEmitted you should be able to get to any function that’s visible via either the ELF headers or the DWARF information. Do you have functions
that don’t show up in either of those places?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">-Andy<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a>]
<b>On Behalf Of </b>Andrew MacPherson<br>
<b>Sent:</b> Wednesday, November 13, 2013 9:23 AM<br>
<b>To:</b> Reid Kleckner<br>
<b>Cc:</b> <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a><br>
<b>Subject:</b> Re: [LLVMdev] Stack traces from JIT code<u></u><u></u></span></p><div><div class="h5">
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">We implemented a similar solution for handling crashes in production but one issue we came across with MCJIT was that the NotifyFunctionEmitted call from the old JIT was replaced with NotifyObjectEmitted. The ObjectImage used by NotifyObjectEmitted
does have a way of iterating symbols but non-external functions used in the module didn't seem to appear in this list so we were left with some gaps in our symbol handling coverage when execution involved these. If there's a way around it that would be great,
otherwise something to keep in mind.<br>
<br>
Cheers,<br>
Andrew<u></u><u></u></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p>
<div>
<p class="MsoNormal">On Wed, Nov 13, 2013 at 5:51 PM, Reid Kleckner <<a href="mailto:rnk@google.com" target="_blank">rnk@google.com</a>> wrote:<u></u><u></u></p>
<div>
<p class="MsoNormal">Writing your own JITEventListener is probably the best way to capture traces from production. Using the existing gdb/JIT interface support is probably far too heavyweight for production. If you roll your own, you can record the PC ranges
efficiently and that should be good enough to capture traces from production.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p>
<div>
<div>
<div>
<p class="MsoNormal">On Tue, Nov 12, 2013 at 2:56 PM, Priyendra Deshwal <<a href="mailto:deshwal@thoughtspot.com" target="_blank">deshwal@thoughtspot.com</a>> wrote:<u></u><u></u></p>
</div>
</div>
<blockquote style="border:none;border-left:solid #cccccc 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">[Resending this email after subscribing to the group. Got an error message the previous time around]</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Hey guys,</span><u></u><u></u></p>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">In our project we have the following workflow:<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">- Given a user request, we construct a C++ program to service the request<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">- We create a compiler invocation to compile that program into an IR module<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">- We use JIT (and optionally MCJIT) to convert the IR into executable code and run it<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Occasionally, we have a crash in the JIT code and we are looking to figure out best practices around debuggability. With the MCJIT option, we can debug in gdb so that is already
a big step forward.<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">However, that does not work for a production crash. We want to capture the stack trace from the crash and write it to stderr. Our binary has a signal handler that does stack
unwinding and symbolization upon crash. Based on my reading so far, we need to implement a JITEventListener which would keep track of the dynamically generated symbol addresses and use the resulting maps for symbolization.<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Will that work? Is there a simpler way?<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""><u></u> <u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Thanks,<u></u><u></u></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">-- Priyendra<u></u><u></u></span></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt">_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:LLVMdev@cs.uiuc.edu" target="_blank">LLVMdev@cs.uiuc.edu</a>
<a href="http://llvm.cs.uiuc.edu" target="_blank">http://llvm.cs.uiuc.edu</a><br>
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a><u></u><u></u></p>
</blockquote>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:LLVMdev@cs.uiuc.edu" target="_blank">LLVMdev@cs.uiuc.edu</a> <a href="http://llvm.cs.uiuc.edu" target="_blank">
http://llvm.cs.uiuc.edu</a><br>
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a><u></u><u></u></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div></div></div>
</div>
</blockquote></div><br></div>