14 Jun 2012
So it's time to start.
I have previously set up a cross compiler environment on my Mac mini, and am now developing on it connected via ssh.
First point today was making a directory structure and creating a git repository. The directory structure starts off as follows
os5/
|-- build/
|-- include/
`-- kernel/
`-- include/
A difference from previous times is that the include directory is outside the kernel directory. That's because last time I realized I had a lot of include files that were used both in the kernel and many other parts. I'll probably move it into some library directory later. Know what? Let's move it into a library directory right now...
os5/
|-- build/
|-- kernel/
| `-- include/
`-- library/
`-- include/
The build/ directory contains some scripts needed for building and testing the os as well as a floppy image preinstalled with the GRUB bootloader.
Next, basic Makefiles were added to os5/ and kernel/. The standard procedure of the main makefile is to run the makefile in kernel/, copy the kernel image into the floppy and then run bochs-term.
BUILDDIR := $(PWD) PATH := /usr/local/cross/bin:$(PATH) DIRS := kernel TARGET := i386-elf AS := nasm CC := i386-elf-gcc LD := i386-elf-ld ASFLAGS := -f elf CCFLAGS := -nostdlib -nostdinc -fno-builtin -fno-exceptions -m32 CCFLAGS += -fomit-frame-pointer -fno-asynchronous-unwind-tables CCFLAGS += -fno-unwind-tables -I$(BUILDDIR)/library/include LDFLAGS := -T $(BUILDDIR)/library/include/Link.ld export BUILDDIR AS CC LD ASFLAGS CCFLAGS LDFLAGS .SILENT: .PHONY: $(DIRS) floppy emul .default: all floppy emul l: all floppy emul all: $(DIRS) $(DIRS): force @echo " MAKE " $@ @cd $@; $(MAKE) $(MFLAGS) clean: @for DIR in $(DIRS); do echo " CLEAN " $$DIR; cd $(BUILDDIR)/$$DIR; make clean; done; floppy: force @echo " UPDATING IMAGE" @build/update_image.sh emul: force @echo " STARTING EMULATOR" @build/emul.sh force: true
The makefile in the kernel/ directory is pretty much straight forward.
TARGET := kernel SUBDIR := kernel SOURCES := kinit.o boot.o SOURCES += $(patsubst %.s,%.o,$(shell find . -name "*.s" | grep -v boot.s)) SOURCES += $(patsubst %.c,%.0,$(shell find . -name "*.c" | grep -v kinit.c)) CCFLAGS += -Iinclude LDFLAGS := -T $(BUILDDIR)/$(SUBDIR)/include/Link.ld .SUFFICES: .o .s .c all: $(TARGET) $(TARGET): $(SOURCES) @echo " ln " $(TARGET) @$(LD) $(LDFLAGS) -o $(TARGET) $(SOURCES) .c.o: @echo " gcc " $< @$(CC) $(CFLAGS) -c $< -o $@ .s.o: @echo " nasm " $< @$(AS) $(ASFLAGS) $< -o $@ clean: -@rm $(SOURCES) 2>/dev/null -@rm $(TARGET) 2>/dev/null