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Everything would be a microkernel if adding some kind of VM or interpreter is enough to get that name, no? With that logic, could we argue loadable kernel modu

Everything would be a microkernel if adding some kind of VM or interpreter is enough to get that name, no? With that logic, could we argue loadable kernel modules (perhaps with proper memory separation) are a sign of a microkernel architecture?

jacquesm 7y ago
No, a microkernel is only 'the real thing' when 'kernel modules' are simply called 'user processes'.
- tedunangst 7y ago
  Turn your linux into a microkernel with this one weird trick: run fuse!
rantwasp 7y ago
yes. the author of that deck is playing it pretty loose when it come to the definition of a microkernel. normally the microkernel means the minimum needed primitives to implement the OS and after that everything is build on top of that, not pluggable modules. For all intents and purposes the Linux kernel is a monolithic one and the eBPF capability make it more extensible / less of a pain to do certain things but definitely do not turn it into a microkernel.
- naasking 7y ago
  > normally the microkernel means the minimum needed primitives to implement the OS and after that everything is build on top of that Sure, the minimum amount of full trust code. In this case, the full trust code is the eBPF VM which enforces protection boundaries instead of the MMU as in a classic microkernel. I'm not sure a microkernel classification ought to depend on the MMU specifically, it's a general system design philosophy.
  - rantwasp 7y ago
    it’s not just the memory protection. it’s the scheduling, IPC, etc. the eBPF vm uses the capabilities of the kernel, it is not the kernel. No kernel, no nothing. also, following your train og thought I could say that containers make this a microkernel. it would be a claim that would get you laughed out of a room.
    - naasking 7y ago
      A kernel provides trusted runtime services for an operating system. A microkernel provides a minimal set of trusted runtime services for an operating system, and relies on some protection mechanism for isolating subsystems to avoid corrupting the trusted core. Preemptive scheduling is not necessarily part of it; depends whether your system requires "time" to be a protected resource. eBPF is a kernel service, just like processes, scheduling, IPC. If eBPF can isolate subsystems and supports safe collaboration of eBPF programs despite all running at ring 0, then the eBPF VM in the Linux kernel could qualify as a microkernel once you remove everything else. > also, following your train og thought I could say that containers make this a microkernel. If you could run all of the device drivers in containers such that they couldn't corrupt the kernel's data, then sure, you could run it as a microkernel because you wouldn't have anything left in the kernel except essential services like threading, IPC and containers.

jacquesm 7y ago

No, a microkernel is only 'the real thing' when 'kernel modules' are simply called 'user processes'.

tedunangst 7y ago
Turn your linux into a microkernel with this one weird trick: run fuse!

rantwasp 7y ago

yes. the author of that deck is playing it pretty loose when it come to the definition of a microkernel. normally the microkernel means the minimum needed primitives to implement the OS and after that everything is build on top of that, not pluggable modules. For all intents and purposes the Linux kernel is a monolithic one and the eBPF capability make it more extensible / less of a pain to do certain things but definitely do not turn it into a microkernel.

naasking 7y ago
> normally the microkernel means the minimum needed primitives to implement the OS and after that everything is build on top of that Sure, the minimum amount of full trust code. In this case, the full trust code is the eBPF VM which enforces protection boundaries instead of the MMU as in a classic microkernel. I'm not sure a microkernel classification ought to depend on the MMU specifically, it's a general system design philosophy.
- rantwasp 7y ago
  it’s not just the memory protection. it’s the scheduling, IPC, etc. the eBPF vm uses the capabilities of the kernel, it is not the kernel. No kernel, no nothing. also, following your train og thought I could say that containers make this a microkernel. it would be a claim that would get you laughed out of a room.
  - naasking 7y ago
    A kernel provides trusted runtime services for an operating system. A microkernel provides a minimal set of trusted runtime services for an operating system, and relies on some protection mechanism for isolating subsystems to avoid corrupting the trusted core. Preemptive scheduling is not necessarily part of it; depends whether your system requires "time" to be a protected resource. eBPF is a kernel service, just like processes, scheduling, IPC. If eBPF can isolate subsystems and supports safe collaboration of eBPF programs despite all running at ring 0, then the eBPF VM in the Linux kernel could qualify as a microkernel once you remove everything else. > also, following your train og thought I could say that containers make this a microkernel. If you could run all of the device drivers in containers such that they couldn't corrupt the kernel's data, then sure, you could run it as a microkernel because you wouldn't have anything left in the kernel except essential services like threading, IPC and containers.