kernfs is a virtual file system that reports information about the running system, and in some cases allows adjusting this information. procfs is a virtual file system that provides information about currently running processes. Both of these file systems work by exposing virtual files containing textual data.

The current implementations of these file systems are redundant and both are non-extensible. For example, kernfs is a hardcoded table that always exposes the same set of files; there is no way to add or remove entries on the fly, and even adding new static entries is a nuisance. procfs is similarly limited; there is no way to add additional per-process data on the fly. Furthermore, the current code is not modular, not well designed, and has been a source of security bugs in the past.

We would like to have a new implementation for both of these file systems that rectifies these problems and others, as outlined below:

It is possible that using tmpfs as a backend for kernfs and procfs, or sharing some code with tmpfs, would simplify the implementation. It also might not. Consider this possibility, and assess the tradeoffs; do not treat it as a requirement.

Alternatively, investigate FreeBSD's pseudofs and see if this could be a useful platform for this project and base for all the file systems mentioned above.

When working on this project, it is very important to write a complete regression test suite for procfs and kernfs beforehand to ensure that the rewrites do not create incompatibilities.

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