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<div class="moz-cite-prefix">On 3/18/16 6:42 AM, Zhiyu Xie via
llvm-dev wrote:<br>
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<div><span>Hi all,</span></div>
<div><span> I am trying to instrument a program to insert a
function call</span> after SP-Update instructions. SP-Update
instructions are those modify the esp register such as mov
esp, eax ; xchg eax, esp ; add esp, [eax+0x20] and so on. It
seems that I should dig into the back end. But which
representation of instructions should I focus on? MachineInstr
or MCInst or other class?</div>
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<br>
You should write a MachineFunctionPass and operate and the
MachineInstr level. Your pass will need to be integrated into the
LLVM code generator for your target.<br>
<br>
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<div> <span>Where is the definitions of all opcodes and
registers? <br>
</span></div>
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<br>
For MachineInstr's, registers are just numbers, and there are
constants (e.g., Reg::RAX, IIRC) that represent the various
registers.<br>
<br>
You can look at the control-flow integrity pass for a dated (but I
think still useful) example of how to write a MachineFunctionPass.
It is at
<a class="moz-txt-link-freetext" href="https://github.com/jtcriswell/SVA/blob/master/llvm/lib/Target/X86/X86CFIOptPass.cpp">https://github.com/jtcriswell/SVA/blob/master/llvm/lib/Target/X86/X86CFIOptPass.cpp</a>.<br>
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<div>In which part of the back end should I inspect the
instructions? And How to insert a function call? May I use
MachineInstrBuilder::BuildMI ?</div>
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<br>
BuildMI is what you want.<br>
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<div> I am so sorry to ask so many questions because I am a
newbie to LLVM. I would appreciate it if any one coulld help
me.</div>
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<br>
If you have not done so already, you should read the document on
"How to Write an LLVM Pass" and the document on the code generator
(the one that briefly explains MachineInstr's). You should also
make use of the doxygen documentation.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
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<pre class="moz-signature" cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a class="moz-txt-link-freetext" href="http://www.cs.rochester.edu/u/criswell">http://www.cs.rochester.edu/u/criswell</a></pre>
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