Also thought of as "minixray", this was a side-project that I worked on over the course of a few days while interning at Google many years ago. This project was a proof-of-concept, simplistic re-implementation of the XRay function profiling framework. Since then, Google has publicly released a new version of XRay, which uses the LLVM compiler toolchain for its instrumentation.
I dug this code up off of my old mac and am putting it online for posterity. I have modified it to build with clang-3.8. I tried to get it to work, and then eventually realized that I had left the code part-way through a re-implementation.
The original prototype is located in xiao/lib/xray.c, and it used what a version
of xiao/lib/stub.S that is no longer in existence, but is likely not too
different from what is there now.
I then must have decided to re-implement Xia, making it more "flexible" by letting the individual function patches be stateful. I made a small attempt to fill in what was missing.
git clone git@github.com:pgoodman/xiao.git
cd xiao
make clean all
cd test
make clean all
./tc