Debugging an Operating System

Question

I was going through some general stuff about operating systems and struck on a question. How will a developer debug when developing an operating system i.e. debug the OS itself?

Answer 1

Debugging an operating system is not for the faint of heart. Because the kernel is being debugged, your options would be quite limited. Copious amount of printf statements is one trick, and furthermore, it depends on really what 'operating system' is being debugged, we could be talking about

• Filesystem
• Drivers
• Memory management
• Raw Disk input/output
• Screen input/output
• Kernel

Again, it is a widely varying exercise as in the above, they all interact with one another. Even more complicated is the fact, supposing you were to debug the kernel, how would you do it if the runtime environment is not properly set (by that, I am talking about the kernel's responsibility for loading binary executables).

Some kernels may (not all of them have them) incorporate a simple debug monitor, in fact, if I rightly recall, in the book titled 'Developing your own 32bit Operating System' by Richard A Burgess, Sams publishing, he incorporated a debug monitor which displays various states of the CPU, registers and so on.

Again, take into account of the fact that the binary executables require a certain loading mechanism, for example a gdb equivalent, if the environment for loading binaries are not set up, then your options are quite limited.

By using copious amount of printf statements to display errors, logs etc to a separate terminal or to a file is the best line of debugging, it does sound a nightmare but it would be worth the effort to do so.

Hope this helps, Best regards, Tom.