# CmpLog instrumentation

The CmpLog instrumentation enables logging of comparison operands in a
shared memory.

These values can be used by various mutators built on top of it.
At the moment we support the RedQueen mutator (input-2-state instructions only), 
for details see [the RedQueen paper](https://www.syssec.ruhr-uni-bochum.de/media/emma/veroeffentlichungen/2018/12/17/NDSS19-Redqueen.pdf).

## Build

To use CmpLog, you have to build two versions of the instrumented target
program.

The first version is built using the regular AFL++ instrumentation.

The second one, the CmpLog binary, is built with setting AFL_LLVM_CMPLOG during the compilation.

For example:

```
./configure --cc=~/path/to/afl-clang-fast
make
cp ./program ./program.afl
make clean
export AFL_LLVM_CMPLOG=1
./configure --cc=~/path/to/afl-clang-fast
make
cp ./program ./program.cmplog
unset AFL_LLVM_CMPLOG
```

## Use

AFL++ has the new `-c` option that needs to be used to specify the CmpLog binary (the second
build).

For example:

```
afl-fuzz -i input -o output -c ./program.cmplog -m none -- ./program.afl @@
```

Be sure to use `-m none` because CmpLog can map a lot of pages.
