diff options
Diffstat (limited to 'sos-code-article5/README')
| -rw-r--r-- | sos-code-article5/README | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/sos-code-article5/README b/sos-code-article5/README new file mode 100644 index 0000000..efbbc89 --- /dev/null +++ b/sos-code-article5/README @@ -0,0 +1,90 @@ + + SOS: A Simple Operating System + + +This is SOS, a Simple Operating System for i386-family +processors. This is as simple as possible to show a way to program a +basic Operating System on real common hardware (PC). The code should +be easily readable and understandable thanks to frequent comments, and +references to external documentation. We chose to implement the basic +features of an OS, thus making design decisions targetting towards +simplicity of understanding, covering most of the OS classical +concepts, but not aiming at proposing yet another full-fledged +competitive OS (Linux is quite good at it). However, for those who +would like to propose some enhancements, we are open to any code +suggestions (patches only, please). And yes, there might be bugs in +the code, so please send us any bug report, and/or patches ! + +The OS comes as a set of articles (in french) to be published in the +journal "Linux Magazine France". Each month, the part of the code +related to the current article's theme is released (see VERSION file), +and the resulting OS can be successfully compiled and run, by booting +it from a floppy on a real machine (tested AMD k7, Cyrix and Intel P4 +pentiums), or through an x86 emulator (bochs or qemu). The resulting +OS is available as a multiboot compliant ELF kernel (sos.elf) and as a +floppy image (fd.img). It provides a very very very basic demo whose +aim is to understand how everything works, not to animate sprites on +the screen with 5:1 dolby sound. + +The initial technical features and lack-of-features of the OS are: + - monolithic kernel, fully interruptible, non-preemptible (big kernel + lock), target machines = i386 PC or better + - compiles on any host where the gcc/binutils toolchain (target + i586-gnu) is available. Can be tested on real i486/pentium + hardware, or on any host that can run an i486/pentium PC emulator + (bochs or qemu) + - kernel loaded by grub, or by a sample bootsector (up to article 2 + ONLY) + - clear separation of physical memory and virtual memory concepts, + even inside the kernel: no identity-mapping of the physical memory + inside the kernel (allows to move virtual mappings of kernel pages + at run-time, eg to free ISA DMA pages, and to avercome the 4G RAM + barrier) + - slab-type kernel memory allocation + - no swap, no reverse mapping + - VERY simple drivers: keyboard, x86 video memory, IDE disks + - logical devices: partitions, FAT filesystem, "hard-coded" + mountpoints only (~ MSDOS) + - no network stack + - user-level features: ELF loader (no shared libraries), processes, + user threads (kernel-level scheduling only), mmap API, basic VFS + +To understand where to look at for what, here is a brief description: + - Makefile: the (ONLY) makefile of the OS. Targets are basically + 'all' and 'clean' + - bootstrap/ directory: code to load the kernel. Both the stuff + needed for a multiboot-compliant loader (eg grub) AND a bootsector + are provided. The bootsector may only be used up to article 2. + - sos/ directory: the entry routine for the kernel (main.c), various + systemwide header files, a set of common useful C routines + ("nano-klibc"), and kernel subsystems (kernel memory management, + etc...) + - hwcore/ directory: Low-level CPU- and kernel-related routines + (interrupt/exception management, translation tables and segment + registers, ...) + - drivers/ directory: basic kernel drivers for various (non CPU) + devices (keyboard, x86 video memory, bochs 0xe9 port, ...). Used + mainly for debugging + - support/ directory: scripts and configuration files to build the + floppy images + - extra/ directory: a set of configuration files to be customized for + non-x86 host installations (yes, we primarily develop SOS on a ppc, for + the x86 target of course), or for grub-less installations. See + README file in this directory. + +The code is licensed under the terms of the GNU GPL version 2 (see +LICENSE file). + +Enjoy ! + + David Decotigny, Thomas Petazzoni, the Kos team + http://sos.enix.org/ + http://david.decotigny.free.fr/ + http://kos.enix.org/~thomas/ + http://kos.enix.org/ + + +-- +David Decotigny + +PS: Made with a Mac. |