LLVM Pass for iOS

Question

I am trying to create an LLVM Pass for iOS and add it to XCODE compilation by setting Other C Flags to "-Xclang -load -Xclang myPass.so". However, at the compilation I got the following error:

Code Block error: unable to load plugin 'libSkeletonPass.so': 'dlopen(libSkeletonPass.so, 9): 
	Symbol not found: __ZN4llvm24DisableABIBreakingChecksE
	Referenced from:libSkeletonPass.so
	Expected in: flat namespace
 in /libSkeletonPass.so'
Command CompileC failed with a nonzero exit code

Is there any special way for creating an LLVM Pass for iOS? Any idea how I could add the missing reference?

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Posted by

serek8

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Answer 1

The LLVM/clang compiler and Swift compiler provided with Xcode are configured not to load plug-ins for security.

Posted by

cmhanson

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Answer 2

Thanks for the reply. How else can one apply obfuscation at the compilation time?

Posted by

serek8

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Answer 3

You should be able to apply an LLVM pass directly to bitcode (or IR) using LLVM's opt tool.

Then after running it through the pass, feed the bitcode into clang for compiling/assembling/linking.

Posted by

caffeineenthusiast

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Answer 4

One option would be to obfuscate the embedded bitcode. There is the open-source obfuscator-llvm (which hasn't been updated for a long time).

Posted by

jonasdevlieghere

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Answer 5

There's a question involving the same symbol at https://developer.apple.com/forums/thread/121260. From one of the answers there:

Yeah one of the LLVM headers (api-breaking.h) had an extern int that was apparently coming from the linkage to the runtime. We replaced that with a local variable and the review process is fine now. Thanks! @cjserio

The file is abi-breaking.h rather than api-breaking.h though. You may be able to progress further by doing the same thing but you might then run into the issues Developer Tools Engineer is referring to.

Posted by

appledev38

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LLVM Pass for iOS

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