Implementing a GDB Stub in Lightweight Kitten OS

Because of the increasing complexity of the applications running in Kitten, a lightweight HPC OS targeted for compute nodes of massively-parallel, distributed-memory supercomputers, and the complex hardware that Kitten is running on, bugs are becoming more difficult to find. As a result, the need for Kitten to support user-level application debugging becomes more critical. Unfortunately, Kitten currently has no support for user-level application debugging. To solve this problem, we implemented a GDB stub as a kernel module for Kitten without changing the internal architecture of Kitten and Palacios, a high performance embeddable VMM for Kitten, yet with minimal modification to Kitten and Palacios codebases. The GDB stub has only 590 lines of changes to Kitten and 238 lines of changes to Palacios in total. Along with the GDB stub and Palacios, we are now able to debug a userlevel application running in Kitten from a GDB client running in a Palacios Linux Guest. This paper presents our design and implementation of the GDB stub in Kitten.