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<p class="MsoNormal">Hey Stefan,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The function looks like this:<br>
“; Function Attrs: nounwind<o:p></o:p></p>
<p class="MsoNormal">declare i32 @puts(i8* nocapture readonly) local_unnamed_addr #2”<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I wondered if I can do the external symbol resolution without using the JIT and RuntimeDyld (for now). For me it sounds like something that could be possible…<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Kind greetings<o:p></o:p></p>
<p class="MsoNormal">Björn<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Stefan Gränitz <stefan.graenitz@gmail.com> <br>
<b>Sent:</b> Dienstag, 15. Januar 2019 12:42<br>
<b>To:</b> Gaier, Bjoern <Bjoern.Gaier@horiba.com>; Mehdi AMINI <joker.eph@gmail.com><br>
<b>Cc:</b> llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] Function - replaceAllUsesWith<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Björn<br>
<br>
What does the IR code look like when you dump your module?<br>
llvm::outs() << mainModule;<br>
<br>
I guess for the external function "puts" it will have a declaration like this:<br>
declare i32 @puts(i8*)<br>
<br>
When loading your module in the JIT, RuntimeDyld will resolve it to an actual address. This lookup is done by name and it happens in a stage called external symbol resolution. You should be able to inspect how this works by setting a breakpoint here:<br>
<a href="https://github.com/llvm/llvm-project/blob/cce1c2eb0e87e84be6345c870d3334f748bdc5bb/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp#L1084">https://github.com/llvm/llvm-project/blob/cce1c2eb0e87e84be6345c870d3334f748bdc5bb/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp#L1084</a><br>
<br>
Hope it helps.<br>
Stefan<o:p></o:p></p>
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<p class="MsoNormal">Am 15.01.19 um 08:02 schrieb Gaier, Bjoern via llvm-dev:<o:p></o:p></p>
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<p class="MsoNormal">On Mon, Jan 14, 2019 at 3:21 AM Gaier, Bjoern via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="DE">Hello LLVM-World,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="DE"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">currently I play around with a „llvm::Module” and an external function defined there “puts”. Normally this function gets resolved in the JIT-Process but I wonder about two things:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<ol start="1" type="1">
<li class="gmail-m3997524881775611987msolistparagraph" style="mso-list:l0 level1 lfo3">
Can I resolve the function already in this step? I used “replaceAllUsesWith” and passed a “llvm::ConstantInt” to the function. But this didn’t worked.<o:p></o:p></li></ol>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">I'm not sure if I followed correctly, but you can't replace a function declaration with a constant int. The value for the function will be used (mostly) as an argument to the call instruction, which won't really be able to operate on an
int. It isn't clear to me what you're trying to do exactly, replace the call to puts with an indirect call to the pointer value that correspond to puts in your current process? You would need to at least cast this pointer value to the right type, and use an
indirect call.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4">Hey Mehdi,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4"> </span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="color:#4472C4">I simply try overloading “puts” with a custom address before I start the JIT process. I want to replace the call to “puts” with my own address. For a test purpose I tried this now:<br>
</span><span style="font-size:9.5pt;font-family:Consolas"> mainModue->getFunction(</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"puts"</span><span style="font-size:9.5pt;font-family:Consolas">)->replaceAllUsesWith(</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> llvm::</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">ConstantExpr</span><span style="font-size:9.5pt;font-family:Consolas">::getPointerCast(</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> llvm::</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">ConstantInt</span><span style="font-size:9.5pt;font-family:Consolas">::get(llvm::</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">IntegerType</span><span style="font-size:9.5pt;font-family:Consolas">::get(context,
64), 0xF),</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> mainModue->getFunction(</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"puts"</span><span style="font-size:9.5pt;font-family:Consolas">)->getType()</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> )</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:9.5pt;font-family:Consolas"> );</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4">This code will crash the application though. I know that 0xF is not a correct address and that there can be stuff optimized, but currently I just want to ‘see’ that “puts” was overloaded with 0xF.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4">Kind greetings</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#4472C4">Björn</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Best,<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Mehdi<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<li class="gmail-m3997524881775611987msolistparagraph" style="mso-list:l2 level1 lfo6">
<o:p></o:p></li><li class="gmail-m3997524881775611987msolistparagraph" style="mso-list:l2 level1 lfo6">
What might happen if I have two modules and use “replaceAllUsesWith” on a function of Module A, passing a function of Module B.<o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thank you for the help in advance!<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Kind greetings<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Björn<o:p></o:p></p>
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<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Takeshi Fukushima. Junichi Tajika
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<p class="MsoNormal">_______________________________________________<br>
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<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Takeshi Fukushima. Junichi Tajika
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<o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>LLVM Developers mailing list<o:p></o:p></pre>
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<pre>-- <o:p></o:p></pre>
<pre><a href="https://weliveindetail.github.io/blog/">https://weliveindetail.github.io/blog/</a><o:p></o:p></pre>
<pre><a href="https://cryptup.org/pub/stefan.graenitz@gmail.com">https://cryptup.org/pub/stefan.graenitz@gmail.com</a><o:p></o:p></pre>
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