L4Re Quick Note (1)

General System Structure

Microkernel: Provides only a minimal set of mechanisms that are necessary to support applications.
Runtime Environment: Aims at providing more convenient abstractions for application development.
Applications: Run on top of the system and use services provided by the Runtime Environment.

The Fiasco.OC Microkernel

lowest-level piece of software
only program that runs in privileged processor mode
does not include complex services
services are implemented in kernel objects
tasks hold references called capabilities (in their respective “object space”, which is a kernel-protected table)
if a task owns a capability, it may grant other tasks the same (or fewer) rights
capabilities are a concept that enables flexibility

Inter Process Communication (IPC)

It is always synchronous
The basic communication mechanism
also used to resolve hardware exceptions, faults and for virtual memory management

Kernel Objects

Task comprises a memory address space, an object space, and on X86 an IO-port address space
Thread is bound to a task and executes code.
Factory is used by applications to create, control and restrict kernel objects
IPC gate is used to create a secure communication channel between different tasks
IRQ objects provide access to hardware interrupts.
Vcon Provides access to the in-kernel debugging console
Scheduler implements scheduling policy and assignment of threads to CPUs