<div dir="ltr"><div><div>For every level of translation [in terms of "human readable -> machine code translation", not someone translating a literary work from one language to another - although often some subtle details are lost here too], a little bit of the semantic meaning is lost. This means that you can almost never completely reconstruct the code in original form from the machine-code, or the C-code from the LLVM IR, or the C++ code from the output of something like cfront (the original C++ -> C translator), or the original Pascal code from a Pascal to C compiler, etc.<br><br></div>It is, at least sometimes, possible to reconstruct something that can then be "compiled" [in quotes as it's a loose term in this discussion] again from the binary file, but it's often lacking some of the original subtlety. And there are certainly cases where the original code is very hard to derive from the machine-code. I played with a "symbolic disassembler" many years back, and on "well-behaved code" it would reconstruct assembly code that could be recompiled, but it struggled with for example switch-statements that became a PC-relative jump-table, because when you modify the code, it couldn't figure out what the jumps were - just as one example.<br><br><br></div><div>I'm pretty sure it's possible to, at least as a human, write code that is nearly impossible to translate back to a higher level language. And modern compilers may not use the same types of obfuscation, but they will certainly produce code that is complex, hard to follow and not using obvious instructions for some particular purpose.<br><br>--<br></div><div>Mats<br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 17 July 2015 at 17:11, Shuai Wang <span dir="ltr"><<a href="mailto:wangshuai901@gmail.com" target="_blank">wangshuai901@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">This is not a easy task. And I believe there is <b>NO</b> (open-source) tool can fully solve this problem (statically). Correct me if I was wrong.<div><br></div><div>It would be more helpful if you can provide details about what you want to do, say, static or dynamic ? stripped binary or binary with symbolic information? </div><div>What compiler do you work on? </div><div><br></div><div>Check out papers below if you are interested.</div><div><br></div><div><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__dl.acm.org_citation.cfm-3Fid-3D2465380&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=Mfk2qtn1LTDThVkh6-oGglNfMADXfJdty4_bhmuhMHA&m=PMWV93YoHpzwPfOq-d9rjutlZ5ICwU8uIp3HLShT_D0&s=74RkRYSGnXHwJXd5DvxXdamQv0mj7_NjyBzbdCNRrYo&e=" target="_blank">http://dl.acm.org/citation.cfm?id=2465380</a><br></div><div><br></div><div><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__dl.acm.org_citation.cfm-3Fid-3D2462165&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=Mfk2qtn1LTDThVkh6-oGglNfMADXfJdty4_bhmuhMHA&m=PMWV93YoHpzwPfOq-d9rjutlZ5ICwU8uIp3HLShT_D0&s=rpl0PCuoy_iecIKs3lz3F0nGYQYw1J1cqTapvfLsceo&e=" target="_blank">http://dl.acm.org/citation.cfm?id=2462165</a><span class="HOEnZb"><font color="#888888"><br></font></span></div><span class="HOEnZb"><font color="#888888"><div><br></div><div><br></div><div><br></div><div>Shuai</div><div><br></div><div><br></div></font></span></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Fri, Jul 17, 2015 at 3:09 AM, 慕冬亮 <span dir="ltr"><<a href="mailto:mudongliangabcd@gmail.com" target="_blank">mudongliangabcd@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr">I want to transform elf binary to llvm IR, and do some instrumentation based on llvm.<div>Is there any tool which can do the transformation?</div><div>Thanks in advance.</div><div> </div><div> - mudongliang</div></div>
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