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llvm-assignment

Overview

This is an out-of-tree LLVM plugin example, that uses bogus conditional branch by command line argument --bogus=<BOOLEAN>.

Development Environment

Platform Support And Requirements

This project has been tested on Ubuntu 22.04.4 LTS. In order to build llvm-assignment you will need:

  • LLVM 18
  • C++ compiler that supports C++17
  • CMake 3.20 or higher

In order to run the passes, you will need:

  • clang-18 (to generate input LLVM files)
  • opt (to run the passes)

There are additional requirements for tests (these will be satisfied by installing LLVM 18):

  • lit (aka llvm-lit, LLVM tool for executing the tests)
  • FileCheck (LIT requirement, it's used to check whether tests generate the expected output)

Building & Testing

Building

You can build llvm-assignment (and all the provided pass plugins) as follows:

cd <build/dir>
cmake -DLT_LLVM_INSTALL_DIR=<installation/dir/of/llvm/18> <source/dir/llvm/assignment>
make

The LT_LLVM_INSTALL_DIR variable should be set to the root of either the installation or build directory of LLVM 18. It is used to locate the corresponding LLVMConfig.cmake script that is used to set the include and library paths.

Testing

In order to run llvm-assignment tests, you need to install llvm-lit (aka lit). It's not bundled with LLVM 18 packages, but you can install it with pip:

# Install lit - note that this installs lit globally
pip install lit

Running the tests is as simple as:

$ lit <build_dir>/test

Running

Generating Input

Before you can test it, you need to prepare an input file:

# Generate an LLVM test file
$LLVM_DIR/bin/clang -O1 -S -emit-llvm <source/dir/llvm/assignment>/inputs/input_for_obfuscator.cpp -o input_for_obfuscator.ll

Generating Output

# Watch out '>' between input and output
$LLVM_DIR/bin/opt -load-pass-plugin <BUILD_DIR>/lib/libObfuscator.{so|dylib} --bogus=<BOOLEAN> -passes=obfuscator
-S <INPUT_LLVM_FILE> > <OUTPUT_LLVM_FILE>

Without Output

$LLVM_DIR/bin/opt -load-pass-plugin <BUILD_DIR>/lib/libObfuscator.{so|dylib} --bogus=<BOOLEAN> -passes=obfuscator
-disable-output <INPUT_LLVM_FILE>

Above description is mostly copied from llvm-tutor README for convenience.