KEDR is a framework to facilitate dynamic analysis of kernel modules in Linux ("KEDR" is an acronym for "KErnel-mode Drivers in Runtime"). KEDR allows you to intercept the calls that a kernel module makes to the functions exported by other modules and by the kernel proper. The tools provided by the framework can record the arguments and return values of these functions to a trace, perform fault simulation according to user-defined scenarios, and check the kernel modules for memory leaks and some other kinds of problems. Custom data collection and analysis tools for the Linux kernel can also be built on top of KEDR framework.
x11vis is a visual and interactive tool for debugging X11 clients. Unlike other tools such as xtrace, it displays human readable IDs on all requests, no matter at which point in time the information becomes available. To help you cope with large amounts of data, it displays only the most important information by default, automatically folds sequences of boring requests, allows you to filter by packet type or client, and provides markers for navigation. Instead of assigning a number to each connection, it displays the command line with which that client was started.
ftracer is a simple user space implementation of a Linux kernel style function tracer. It allows you to trace every call in instrumented user applications. It is useful for debugging and performance analysis due to its fine grained time stamp. This allows you to do control flow oriented debugging without any special instrumentation. So if the program does something unexpected, it's easily possible to look at the function calls before that, and use that to deduce the cause of the problem. ftracer relies on gcc generating a call on top of every function call. The tracing slows every function call down (about 3x). The tracing is per thread and does not create a global bottleneck. It supports a dump function in C, directly callable by the program or on exit, and a gdb function to dump from gdb.