We present Extractor and Viewer, two tools from the Kayrebt toolset. The former is a plugin for the Gnu Compiler Collection (GCC) which builds pseudo-UML2 activity diagrams from C source code. It is specifically designed to handle the Linux kernel, a large and complex codebase. Use cases for this tool are numerous. The diagrams extracted from the C source code can be used to get a better insight of the control or data flow inside a program, or to evaluate the complexity of a function at a glance. Kayrebt::Viewer is a GUI designed for visualizing and navigating between the diagrams to explore source code.