Kernel Debugging: Difference between revisions

Suppose you want to develop your VFS interface implementation. Your already created the interface for block devices (doesn't matter if you already implemented it in your kernel). In this case, you can implement your block device interface as a set of wrappers that [http://en.wikipedia.org/wiki/Adapter_pattern adapts] your interface to POSIX calls. You will then implement your VFS interface (i.e., the code that will manage the filesystem drivers in your kernel) on top of those wrappers. You will then test&debug your implementation all in the hosted environment, and when it is mature, you link it into your real kernel instead of into your hosted implementations. You will finally test your newly introduced code, now in the freestanding environmentm to ensure it works there as well.

Now, the PorsPros. First of all, you can use your favourite debugger. You can also use unit testing, for example, which is far better than testing software by hand, if you use the right method.

There are some Cons on this approach. For example, you are far from your target environment when you code like this. This is further agravated by the fact that so-called ''freestanding'' environments are dramatically more sensible to undefined behaviour, specially unitilialized variables. You can workarround this limitation by asking the compiler to perform aggressive optimization while testing hosted, which make software more sensible to undefined behaviour, too. However, as the best debug environment is the final target environment, you will still want to test your code when you introduce in into your real kernel.