Kernel and userspace separation policy

This issue covers which components may be moved to userspace, or should continue stay in the kernel.

Kernel

• CPU drivers - performance
• Memory manager - performance, and moving that to userspace is hard
• Context switch - core part of the kernel
• Capability system - the kernel needs to implement at least the bare minimum to be able to isolate processes from each other
• Scheduler - performance

Userspace currently

• cwd handling
• initfs
• fork and execv
• most drivers
• filesystem
• everything else

Possible to move to userspace

• RTC driver
• path parsing (would require openat)
• the current namespace implementation (would also require openat)
• (part of) the file descriptor table (descriptors, not descriptions) - allows optimizing lseek, fcntl, POSIX pipes, etc.
• process management, including uid/gid/(not yet implemented:) supplementary groups
• application processor startup
• file descriptor allocation (where the lowest available number must be picked)
• virtual memory range allocation