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published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

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The C programming language offers a high degree of control and freedom to programmers. This makes it a powerful tool, but it also gives the language a steep learning curve. One difficulty that many new C programmers face is in figuring out how to analyze and debug their code, as well as the output. There exists a variety of tools that can be used to assist in debugging. They can offer aid by identifying certain types of errors and by providing meaningful output that helps the user understand and correct those errors. The following seven debugging tools have been tested and analyzed in order to ascertain when and how each one of them might be most useful: Valgrind, GCC Address Sanitizer, Clang Address Sanitizer, Mtrace, Memwatch, Electric Fence, and Dmalloc. They have been tested using anonymous code submitted by actual students for C programming labs in order to see how many errors, and of which sort, each tool catches. The results of these tests, as well as their implications, are presented here.

Digitized by Kansas Correctional Industries

Using debuggers is a common mean for identifying and analyzing malware (such as viruses, worms, spyware, rootkits, etc.). However, debuggers can be detected by malware via observing of the behavior of operating system, changes in code (such as breakpoint instructions) and non-standard behavior of the CPU, making the analysis of the malware can be hard and tedious. In this thesis we are implementing a basic debugger based on the QEMU emulator that hides its presence from the debugged application. This is accomplished by using the QEMU as virtual machine and adding context awareness to the already existing primitive debugger. The context awareness is implemented using an embedded Python scripting engine. Such setup gives us a flexible way of implementing support for various operating systems. In this thesis, we have developed two examples. One example is for the RTEMS operating system, which serves as easy to understand reference implementation. Second example is for the Linux operating system, to show the abilities of the undetectable debugger in a more real scenario.

Software bugs are violated specifications. Debugging is the process that culminates in repairing a program so that it satisfies its specification. An important part of debugging is localization, whereby the smallest region of the program that manifests the bug is found. The Debugging Assistant (DEBUSSI) localizes bugs by reasoning about logical dependencies. DEBUSSI manipulates the assumptions that underlie a bug manifestation, eventually localizing the bug to one particular assumption. At the same time, DEBUSSI acquires specification information, thereby extending its understanding of the buggy program. The techniques used for debugging fully implemented code are also appropriate for validating partial designs.

Unterlagen zu einem Vortrag im Rahmen des AFS-Workshops 2002 an der ETH Zürich. Gegenstand der Vortrags sind Tools zum Debugging und zur Analyse des Verhaltens von AFS-Servern und -Clients. Die meisten dieser Tools sind im Source-Baum von OpenAFS enthalten, jedoch kaum dokumentiert.