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# Automatically generate lists of sources using wildcards.
VPATH=./boot:./kernel:./drivers
C_SOURCES = $( wildcard kernel/*.c drivers/*.c )
HEADERS = $( wildcard kernel/*.h drivers/*.h )
# TODO : Make sources dep on all header files.


# Convert the *. c filenames to *. o to give a list of object files to build
OBJ = ${C_SOURCES:.c =.o}

# Defaul build target
all: os-image


# Run bochs to simulate booting of our code.
run: all
	bochs

# This is the actual disk image that the computer loads
# which is the combination of our compiled bootsector and kernel
os-image : boot/boot_sect_c.bin kernel.bin
	cat $^ > os-image

# This builds the binary of our kernel from two object files :
# - the kernel_entry , which jumps to main () in our kernel
# - the compiled C kernel
kernel.bin : kernel/kernel_entry.o ${OBJ}
	ld -o $@ -Ttext 0x1000 $^ --oformat binary

# Generic rule for compiling C code to an object file
# For simplicity , we C files depend on all header files .
%.o : %.c ${HEADERS}
	gcc -ffreestanding -c $< -o $@

# Assemble the kernel_entry.
%.o : %.asm
	nasm $< -f elf -o $@
%.bin : %.asm
	nasm $< -f bin -I 'boot/' -o $@
clean:
	rm -fr *.bin *.dis *.o os-image
	rm -fr kernel/*.o boot/*.bin drivers/*.o

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make run

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nasm boot/boot_sect_c.asm -f bin -I 'boot/' -o boot/boot_sect_c.bin
nasm kernel/kernel_entry.asm -f elf -o kernel/kernel_entry.o
ld -o kernel.bin -Ttext 0x1000 kernel/kernel_entry.o --oformat binary
ld: warning: cannot find entry symbol _start; defaulting to 0000000000001000
[color=#FF0000]kernel/kernel_entry.o:(.text+0x1): undefined reference to `main'
make: *** [kernel.bin] Error 1[/color]