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Finished adding untested bare functionality vfs

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Finished adding untested shm syscalls.
Finished adding untested l4 send/recv helpers

Everything compiles. Now going to fix lots of bugs ;-)
This commit is contained in:
Bahadir Balban
2008-02-03 17:42:38 +00:00
parent 05e9028e90
commit cab2e8bdd3
51 changed files with 1661 additions and 227 deletions
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README
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@@ -12,7 +12,7 @@ tasks that implement memory management, a virtual filesystem layer, and these
servers currently support a small but essential subset of the POSIX API.
Codezero project is an effort to implement a modern, open source operating
system based on the latest technology in microkernel design. It targets
system based on the latest technology in microkernel and OS design. It targets
realtime, high-end embedded systems and has an emphasis on the ARM architecture.
It is quite common to see open source projects developed in a closed-doors
@@ -23,13 +23,32 @@ the Linux Kernel.
Why the name Codezero?
The project focuses on simplicity, elegance, cleanliness, which are assets
usually hard to achieve in software engineering. The philosophy is to implement
a structurally complete system with most modern and complex operating system
features while retaining simplicity in the implementation as much as possible.
Avoidance of code bloat is a short way to put it. This objective also fits well
with embedded platforms, which usually have rigorous memory and performance
requirements.
The project focuses on simplicity, elegance, cleanliness, which are important
assets in software engineering. The philosophy is to implement a structurally
complete system with most modern OS features while retaining simplicity in the
implementation as much as possible. This objective also fits well with embedded
platforms, which usually have rigorous memory and performance requirements. Also
the project is written from scratch, so the name emphasises that.
Design & Features:
Codezero microkernel: Based on L4 microkernel principles, there are only a few
system calls and the microkernel provides purely mechanism; threads and address
spaces, and the methods of inter-process communication between them. Anything
beyond these are policy and they are implemented in the userspace. Due to this
rigorously simple design the microkernel can be used to design completely
different operating systems. In terms of other features, the microkernel is
preemptive, and smp-ready. Currently only synchronous communication is
implemented, but this will change in the near future.
MM0: Implements memory management. It contains memory and page allocators. It
implements demand paging by managing page faults, physical pages and their
file/task associations.
FS0: Implements a simple, modern virtual filesystem layer. Since it abstracts
the low-level filesystem details, it is a relatively easy job to port a new
filesystem to be used under FS0.
License:
@@ -51,28 +70,32 @@ Why yet another Posix (micro) kernel?
There are many open source Posix operating systems with advanced features such
as *BSD and Linux. However these were originally not designed for embedded
systems. Unix itself and all the tools built upon weren't meant for using on
small devices. Besides, these operating systems naturally contain a lot of
historical code. Linux is well established, and targets a broad range of
platforms and uses, but consequently embedded platforms don't always get enough
emphasis. Also such well established, mature systems tend to oppose major design
overhauls, which limits innovation to a certain extent. In addition, their code
base is so big, that it gets more and more difficult to understand how the
system works. Usually %95 of the code is irrelevant to the problem, in case of
embedded systems. Codezero is written from scratch to solely target embedded
systems and as such the source code is %100 relevant. It is small and free from
legacy code. Finally monolithic kernels may have issues with dependability due
to much of the code sharing the same address space. Being a microkernel design,
Codezero aims to defeat this problem and increase dependability.
small devices. Accordingly, these operating systems contain a lot of historical
code. Linux is well established, and targets a broad range of platforms and
uses, but consequently embedded platforms don't always get enough emphasis. Also
such well established, mature systems tend to oppose major design overhauls,
which limits innovation to a certain extent. In addition, their code base is so
big, that it gets more and more difficult to understand how the system works.
Usually much of the code is irrelevant to the problem, in case of embedded
systems. Codezero is written from scratch to solely target embedded systems and
as such the source code is %100 relevant. It is small and free from legacy code.
Finally monolithic kernels may have issues with dependability due to much of the
code sharing the same address space. Being a microkernel design, Codezero aims
to defeat this problem and increase dependability.
Other than these modern kernels, there is systems software targeting embedded
devices. Most of them are proprietary, with their own users. Some of the open
source ones are structurally too simplistic, and lack modern features such as
paging. There are certainly existing well-designed embedded operating systems,
but Codezero provides an alternative that will follow the open source
development principles more closely. Finally, there are new ideas in OS
literature that would improve Unix but aren't implemented either because they
have no existing users or may break compatibility somewhat. (E.g. some are
presented in Plan 9, or ReiserFS 4). As well as practising realistic development
methodologies, Codezero project aims to keep up with the latest OS literature
and provide the opportunity to incorporate the latest ideas in OS technology.
paging. There are existing well-designed embedded OS'es, but Codezero provides
an alternative that will follow the open source development principles more
closely. This will prove useful because many embedded systems still use older
development methods and the right open source methodology would prove favorable
in the fast-paced nature of development (Linux has already proven that).
Finally, there are new ideas in OS literature that would improve Unix but aren't
implemented either because they have no existing users or may break compatibility
somewhat (e.g. some are presented in Plan 9). As well as practising realistic
development methodologies, Codezero project aims to keep up with the latest OS
literature and provide the opportunity to incorporate the latest ideas in OS
technology.