a-darwish / Cuteos
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- What?
Cute! is a 64-bit SMP-safe POSIX-compatible kernel for the PC architecture.
It's 'cute' in the sense of having the source code as simple and fun to work with as possible, hopefully without sacrificing performance.
Throughout this project, a huge number of questions were (and are) asked to the great people at #osdev. Special thanks to:
- Brendan Trotter (bcos), <[email protected]>, the BCOS project
- Travis Geiselbrecht (geist), http://tkgeisel.com
- Navigation:
To begin your way throughout the kernel source, I'd recommend checking the freestanding isolated parts first. Begin with the `lib/' folder, which includes optimized C string methods, type-generic linked-lists, spinlocks, a printf() implementation, etc.
Most of the kernel heavily-used idioms are included in 'kernel.h'; it'll be handy to have it open while checking the rest of the source.
This kernel source is tracked by 'git' from day 0: if you'd like to know how to write a bootloader and a kernel from scratch, the git history (with its carefully written commit logs) should be very valuable.
By now, you can go anywhere. ALWAYS check a module's header file BEFORE checking its code. Due to compilers inefficiencies [1] and C parsing semantics, a lot of details are put in *.h. Comments in the *.c files also assume reading such headers FIRST, unless otherwise stated.
[1] To be fixed by GCC-4.5 `link-time optimization': constant folding, code inlining, and further analysis across separate object modules.
README - this file.
boot/ - early bootstrap code: a 512-Kbyte bootloader, assembly for jumping to C, code to jump to 'real-mode' and return back, the SMP trampoline, etc.
lib/ - library: as stated above, freestanding components like C string methods, linked-lists (for stacks and queues), spinlocks, a printf(), etc
mm/ - memory management: dynamic memory allocation and virtual memory.
dev/ - device drivers: interrupt controllers, timers, keyboard, inter-processor interrupts (local APICs), etc
kern/ - the rest: context switching, thread scheduling, BIOS table parsers, IRQ handling, system-wide panic(), etc.
tools/ - userspace tools: Python-2.6+/3.0+ programs that generate gnuplot scripts out of the kernel scheduling statistics.
- Influences?
One of the MAJOR goals of this project is examining the current literature of Operating Systems in the process:
- The page allocator is influenced by SVR2 buffer-cache lists,
with tweaks for zoning and PC's sparse physical memory.
- Dynamic memory allocation uses the McKusick-Karels algorithm
originally found in 4.3-BSD.
- Overall kernel coding style and APIs are heavily influenced by
Linux-2.6. I used that style in the past, and I love it.
- The scheduler MLFQ parameters are taken from Solaris, with
influences from the FreeBSD ULE (2.0) scheduler.
- Books?
Beside the datasheets, specifications, and research papers saved in our `references' git repository [**], below books proved to be tremendously helpful:
- M. Bach: `The Design of the UNIX Operating System', 1986
That book is __perfect__ for understanding the basics.
- M.K. McKusick and G.V. Neville-Neil: `The Design and
Implementation of the FreeBSD Operating System', 2004
- J. Mauro and R. McDougall: `Solaris Internals, Core Kernel
Components', first edition, 2000
- U. Vahalia: `Unix Internals, The New Frontiers', 1996
[**] http://gitorious.org/cute-os/references
--Ahmed S. Darwish <[email protected]>