Makefile

#it's called GNUmakefile as only GNU make will process it

# Nuke built-in rules and variables.
override MAKEFLAGS += -rR
 
# This is the name that our final kernel executable will have.
# Change as needed.
override KERNEL := myos
 
# Convenience macro to reliably declare user overridable variables.
define DEFAULT_VAR =
    ifeq ($(origin $1),default)
        override $(1) := $(2)
    endif
    ifeq ($(origin $1),undefined)
        override $(1) := $(2)
    endif
endef
 
# It is suggested to use a custom built cross toolchain to build a kernel.
# We are using the standard "cc" here, it may work by using
# the host system's toolchain, but this is not guaranteed.
override DEFAULT_CC := $(ENV_GCC)
$(eval $(call DEFAULT_VAR,CC,$(DEFAULT_CC)))
 
# Same thing for "ld" (the linker).
override DEFAULT_LD := $(ENV_LD)
$(eval $(call DEFAULT_VAR,LD,$(DEFAULT_LD)))
 
# User controllable C flags.
override DEFAULT_CFLAGS := -g -O2 -pipe
$(eval $(call DEFAULT_VAR,CFLAGS,$(DEFAULT_CFLAGS)))
 
# User controllable C preprocessor flags. We set none by default.
override DEFAULT_CPPFLAGS :=
$(eval $(call DEFAULT_VAR,CPPFLAGS,$(DEFAULT_CPPFLAGS)))
 
# User controllable nasm flags.
override DEFAULT_NASMFLAGS := -F dwarf -g
$(eval $(call DEFAULT_VAR,NASMFLAGS,$(DEFAULT_NASMFLAGS)))
 
# User controllable linker flags. We set none by default.
override DEFAULT_LDFLAGS :=
$(eval $(call DEFAULT_VAR,LDFLAGS,$(DEFAULT_LDFLAGS)))
 
# Internal C flags that should not be changed by the user.
override CFLAGS += \
    -Isrc \
    -Wall \
    -Wextra \
    -std=gnu11 \
    -ffreestanding \
    -fno-stack-protector \
    -fno-stack-check \
    -fno-lto \
    -fPIE \
    -m64 \
    -march=x86-64 \
    -mno-80387 \
    -mno-mmx \
    -mno-sse \
    -mno-sse2 \
    -mno-red-zone \
 
# Internal C preprocessor flags that should not be changed by the user.
override CPPFLAGS := \
    -I src \
    $(CPPFLAGS) \
    -MMD \
    -MP
 
# Internal linker flags that should not be changed by the user.
override LDFLAGS += \
    -m elf_x86_64 \
    -nostdlib \
    -static \
    -z text \
    --no-dynamic-linker \
    -z max-page-size=0x1000 \
    -T linker.ld
 
# Internal nasm flags that should not be changed by the user.
override NASMFLAGS += \
    -Wall \
    -f elf64
 
# Use "find" to glob all *.c, *.S, and *.asm files in the tree and obtain the
# object and header dependency file names.
override CFILES := $(shell cd src && find -L * -type f -name '*.c')
override ASFILES := $(shell cd src && find -L * -type f -name '*.S')
override NASMFILES := $(shell cd src && find -L * -type f -name '*.asm')
override OBJ := $(addprefix build/obj/,$(CFILES:.c=.c.o) $(ASFILES:.S=.S.o) $(NASMFILES:.asm=.asm.o))
override HEADER_DEPS := $(addprefix build/obj/,$(CFILES:.c=.c.d) $(ASFILES:.S=.S.d))
 
# Default target.
.PHONY: all
all: clean init build/bin/$(KERNEL) build/image.iso

build/image.iso: build/bin/$(KERNEL)
	mkdir -p build/iso_root/boot
	cp -v build/bin/myos build/iso_root/boot/
	mkdir -p build/iso_root/boot/limine
	cp -v limine.cfg limine/limine-bios.sys limine/limine-bios-cd.bin \
		limine/limine-uefi-cd.bin build/iso_root/boot/limine/
	
	mkdir -p build/iso_root/EFI/BOOT
	cp -v limine/BOOTX64.EFI build/iso_root/EFI/BOOT/
	cp -v limine/BOOTIA32.EFI build/iso_root/EFI/BOOT/
	
	xorriso -as mkisofs -b boot/limine/limine-bios-cd.bin \
			-no-emul-boot -boot-load-size 4 -boot-info-table \
			--efi-boot boot/limine/limine-uefi-cd.bin \
			-efi-boot-part --efi-boot-image --protective-msdos-label \
			build/iso_root -o build/image.iso
	
	./limine/limine bios-install build/image.iso

init:
	mkdir -p build

# Link rules for the final kernel executable.
build/bin/$(KERNEL): Makefile linker.ld $(OBJ)
	mkdir -p "$$(dirname $@)"
	$(ENV_LD) $(OBJ) $(LDFLAGS) -o $@
 
# Include header dependencies.
-include $(HEADER_DEPS)
 
# Compilation rules for *.c files.
build/obj/%.c.o: src/%.c Makefile
	mkdir -p "$$(dirname $@)"
	$(ENV_CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
 
# Compilation rules for *.S files.
build/obj/%.S.o: src/%.S Makefile
	mkdir -p "$$(dirname $@)"
	$(ENV_CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
 
# Compilation rules for *.asm (nasm) files.
build/obj/%.asm.o: src/%.asm Makefile
	mkdir -p "$$(dirname $@)"
	nasm $(NASMFLAGS) $< -o $@
 
# Remove object files and the final executable.
.PHONY: clean
clean:
	rm -rf build

#! git clone https://github.com/limine-bootloader/limine.git --branch=v7.x-binary --depth=1
#! make -C limine