The Design and Implementation of the Anykernel and Rump Kernels

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not include later debugging [76]. Since we reuse the kernel driver, we get the driver
functionality for free. All of the FFS code for the rump kernel implementation is
involved in calculating the image size and was available from makefs. If code for this
calculation had not been available, we most likely would have implemented it using
shell utilities. However, since determining the size involves multiple calculations
such as dealing with hard links and rounding up directory entry sizes, we concluded
that reusing working code was a better option.
The makefs implementation with a rump kernel backend is available from the othersrc
module at othersrc/usr.sbin/makefs-rump. It also uses the utility at
othersrc/usr.sbin/makefs-analyzetree. Note that the othersrc module is
separate from the src module we mentioned in Section 1.6.1, and the code must be
retrieved from the NetBSD source repository separately.
Interested readers are also invited to look at Appendix B.4, where we present another
method for makefs functionality using standard system utilities as remote clients for
rump kernel servers.
4.3 On Portability
There are two things to consider with portability. First, given that the NetBSD
kernel was ported to run on a hypercall interface, what are the practical implications
for hosting a NetBSD rump kernel on either a non-NetBSD system or a NetBSD
system of a different version. We call these systems non-native. Second, we want
to know if the concept of rump kernel construction is unique to the NetBSD kernel
codebase, or if it can be applied to other operating systems as well.