Benu
====

Operating System Increments for Education and Research
(_Built for _education, _not (normal) _usage)

Simple operating system for demonstration only (academic).
Build through several steps, each bringing something new.
System is "work in progress", improved/extended (almost) every year.
Benu goal is to teach you OS, and to inspire you to create your own OS!

Name "Benu", besides acronym, represents an Egyptian bird ...

Tools required for building:
* for i386 - GNU gcc, GNU ld (GNU Binutils)

* for ARM - package for Ubuntu: gcc-arm-none-eabi
          - if using Sourcery CodeBench Lite Edition for ARM EABI:
            add -lm to LDFLAGS (Chapter_*/*/arch/arm/config.ini)

Tested in QEMU ('qemu-system' package on ubuntu)


Version history (by academic year):
===================================
* 2014/2015: https://github.com/l30nard0/benu tag v0.5
  - "cosmetic" changes, upgrades & fixes

* 2013/2014: https://github.com/l30nard0/benu tag v0.4
  - added support for ARM platform
  - tested only with Versatile PB926EJS on QEMU
  - upgrades & fixes

* 2012/2013: https://github.com/l30nard0/benu tag v0.1
  - POSIX interface (signals, timers, threads, ...)

* 2011/2012: http://sourceforge.net/projects/oszur12/
  - small upgrades ...
  - mirror on https://github.com/l30nard0/os4ec/

* 2010/2011: http://sourceforge.net/projects/oszur11/
  - code in English, switched to git repository
  - rewritten (different increment structure)
  - removed paging support (implementation not simple enough)

* 2009/2010: http://code.google.com/p/oszur2010/
  - supported only i386 platform
  - code in Croatian, svn repository


Full description (in Croatian) available in textbook at:
	http://www.fer.unizg.hr/en/course/osfec
	http://www.fer.unizg.hr/predmet/oszur


IMPORTANT!
==========
If running created system (built from Benu) in emulator other than QEMU, set
standard input and output to vga_text mode -- in i386/config.ini set:
K_INITIAL_STDOUT = vga_text_dev
K_STDOUT = VGA_TXT
U_STDIN = i8042
U_STDOUT = VGA_TXT
U_STDERR = VGA_TXT
(uncomment this lines, comment other with *=COM1)
(Buggy serial port implementation; works on QEMU but not with other emulators)


Please report any bugs (and other problems) on site (github) or via email.
Contact address: leonardo@zemris.fer.hr


DISCLAIMER
==========
Presented system has (probably) *many* bugs! (What is an OS without bugs? :) )
Many concepts might not be adequate or good as might be (as are in some
"real systems").
*Please* do not use it for any other purpose other than experimentation or
education. It’s not tested near enough to be used for anything more.


Using "Sourcery CodeBench Lite Edition for ARM EABI"
=====================================================
Some changes in arch/*/config.ini are required.
In arch/arm/config.ini, change part from:

# Compiling and linking: common parameters

to:

LDFLAGS += -L$(LIB1)

with:

# Compiling and linking: common parameters
#------------------------------------------------------------------------------
LINK = arm-none-eabi-ld
LDSCRIPT = $(BUILDDIR)/ARCH/boot/ldscript.ld
LDFLAGS = -marmelf -lgcc -lm
#------------------------------------------------------------------------------
# set paths to libraries when using Sourcery_CodeBench_Lite_for_ARM_EABI
# e.g. if tools are in /opt/Sourcery_CodeBench_Lite_for_ARM_EABI/:
# LIB1 := /opt/Sourcery_CodeBench_Lite_for_ARM_EABI/lib/gcc/arm-none-eabi/4.7.3/
# LIB2 := /opt/Sourcery_CodeBench_Lite_for_ARM_EABI/arm-none-eabi/lib
LIB1 :=
LIB2 :=
ifeq ($(strip $(LIB1)),)
# try to find paths manually with this simple guesses
TOOLPATH := $(shell command -v arm-none-eabi-gcc;)
ifeq ($(strip $(TOOLPATH)),)
$(error "Can't find: arm-none-eabi-gcc")
endif
DIR := $(shell dirname "$(shell dirname "$(TOOLPATH)")")
LIB1 := $(DIR)/arm-none-eabi/lib
LIB2 := $(DIR)/lib/gcc/arm-none-eabi/
LIB2 := $(LIB2)$(shell ls "$(LIB2)")
endif
LDFLAGS += -L$(LIB1) -L$(LIB2)