Build all the deps in deps. Shortcut the busybox by downloading it in…

…stead. Add logic to build to a zip instead of some hdd image. Parameterize the Makefile better. Start adding some docs in the Makefile.

Makefile

@@ -1,21 +1,36 @@
-CC = i386-linux-musl-gcc
-CFLAGS = -m32 -static -Os -Wall -Wextra
-NASM = nasm
-STRIP = i386-linux-musl-strip
+CPU ?= i686
+ARCH ?= $(CPU)-linux-musl
+CC = $(ARCH)-gcc
+CFLAGS ?= -m32 -static -Os -Wall -Wextra
+NASM ?= nasm
+STRIP ?= $(ARCH)-strip
+CORES ?= $(shell nproc)
+LINUX ?= 5.8.9
+BUSYBOX ?= 1.35.0
+DOSLINUX = 0.0.2
 
-HDD_BASE = hdd.base.img
-LINUX_BZIMAGE = linux-5.8.9/arch/x86/boot/bzImage
-BUSYBOX_BIN = busybox-1.32.0/busybox_unstripped
+HDD_BASE ?= hdd.base.img
+LINUX_BZIMAGE = deps/linux-$(LINUX)/arch/x86/boot/bzImage
+BUSYBOX_BIN = deps/busybox
+
+LINUX_URL = https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-$(LINUX).tar.gz
+BUSYBOX_URL = https://www.busybox.net/downloads/binaries/$(BUSYBOX)-i686-linux-musl/busybox
 
 .PHONY: all
 all: hdd.img
 
 .PHONY: clean
 clean:
-	rm -f hdd.img doslinux.com init/init init/*.o
+	rm -rfv hdd.img doslinux.com init/init init/*.o deps/* DSL.ZIP DOSLINUX/BZIMAGE DOSLINUX/INIT DOSLINUX/BUSYBOX DOSLINUX/DSL.COM DOSLINUX/ROOTFS/DOSLINUX.VER
+
+ultraclean: clean
+	sudo rm -v /usr/local/bin/$(ARCH)-*
+
+$(HDD_BASE):
+	dd if=/dev/zero of=$@ bs=1M count=500 status=progress
 
-hdd.img: $(HDD_BASE) doslinux.com init/init $(LINUX_IMAGE) $(BUSYBOX_BIN)
-	cp $(HDD_BASE) hdd.img
+hdd.img: $(HDD_BASE) doslinux.com init/init $(LINUX_BZIMAGE) $(BUSYBOX_BIN)
+	cp -v $(HDD_BASE) hdd.img
 	MTOOLSRC=mtoolsrc mmd C:/doslinux
 	MTOOLSRC=mtoolsrc mcopy doslinux.com C:/doslinux/dsl.com
 	MTOOLSRC=mtoolsrc mcopy init/init C:/doslinux/init
@@ -29,5 +44,95 @@ doslinux.com: doslinux.asm
 init/init: init/init.o init/vm86.o init/panic.o init/kbd.o init/term.o
 	$(CC) $(CFLAGS) -o $@ $^
 
-init/%.o: init/%.c init/*.h
+init/%.o: init/%.c init/*.h /usr/local/bin/$(CC)
 	$(CC) $(CFLAGS) -o $@ -c $<
+
+deps/musl-cross-make/Makefile:
+	cd deps && \
+	git clone --depth=1 https://github.com/richfelker/musl-cross-make.git
+
+musl-cross-make-config-doslinux: Makefile
+	echo "TARGET = $(ARCH)" > $@
+	echo "OUTPUT = /usr/local" >> $@
+# FIXME: This doesn't work the way musl-cross-make docs say it should
+#	echo "COMMON_CONFIG += CC=\"$(ARCH)-linux-musl-gcc -static --static\"" >> $@
+#	echo "COMMON_CONFIG += CXX=\"$(ARCH)-linux-musl-g++ -static --static\"" >> $@
+	echo "COMMON_CONFIG += CFLAGS=\"-g0 -Os -static --static\"" >> $@
+	echo "COMMON_CONFIG += CXXFLAGS=\"-g0 -Os -static --static\"" >> $@
+	echo "COMMON_CONFIG += LDFLAGS=\"-s\"" >> $@
+
+deps/musl-cross-make/config.mak: musl-cross-make-config-doslinux deps/musl-cross-make/Makefile
+	cp -v musl-cross-make-config-doslinux $@
+
+deps/musl-cross-make/build/local/$(ARCH)/obj_gcc/gcc/xgcc: deps/musl-cross-make/config.mak
+	cd deps/musl-cross-make && \
+	make -j$(CORES)
+
+/usr/local/bin/$(CC): deps/musl-cross-make/build/local/$(ARCH)/obj_gcc/gcc/xgcc
+	cd deps/musl-cross-make && \
+	sudo make -j$(CORES) install
+
+deps/linux-$(LINUX).tar.gz:
+	cd deps && \
+	wget $(LINUX_URL)
+
+deps/linux-$(LINUX)/Makefile: deps/linux-$(LINUX).tar.gz
+	tar zxvf $< -C deps/
+	touch deps/linux-$(LINUX)/Makefile
+
+deps/linux-$(LINUX)/.config: deps/linux-$(LINUX)/Makefile linux-config-doslinux
+	cp -v linux-config-doslinux $@
+
+$(LINUX_BZIMAGE): deps/linux-$(LINUX)/.config
+	cd deps/linux-$(LINUX) && \
+	make -j$(CORES)
+
+$(BUSYBOX_BIN):
+	cd deps && \
+	wget $(BUSYBOX_URL)
+
+.PHONY: zipball
+zipball: DSL.ZIP
+
+DOSLINUX/ROOTFS/doslinux.ver: doslinux.ver
+	cp -v $< $@
+DOSLINUX/DSL.COM: doslinux.com
+	cp -v $< $@
+DOSLINUX/INIT: init/init
+	cp -v $< $@
+DOSLINUX/BZIMAGE: $(LINUX_BZIMAGE)
+	cp -v $< $@
+DOSLINUX/BUSYBOX: $(BUSYBOX_BIN)
+	cp -v $< $@
+
+DSL.ZIP: DOSLINUX/ROOTFS/doslinux.ver DOSLINUX/BZIMAGE DOSLINUX/INIT DOSLINUX/BUSYBOX DOSLINUX/DSL.COM
+	zip -9vvr DSL.ZIP DOSLINUX/
+
+######################################################################
+
+.PHONY: showconfig
+showconfig: ## Shows the configuration variables for this Makefile and their current values
+showconfig: p-DOSLINUX p-CORES p-CPU p-ARCH p-CC p-NASM p-STRIP p-LINUX p-LINUX_BZIMAGE p-LINUX_URL p-BUSYBOX p-BUSYBOX_BIN p-BUSYBOX_URL p-HDD_BASE
+
+.PHONY: gstat
+gstat:
+	git status
+
+.PHONY: gpush
+gpush:
+	git commit
+	git push
+
+define newline # a literal \n
+
+
+endef
+# Makefile debugging trick:
+# call print-VARIABLE to see the runtime value of any variable
+# (hardened a bit against some special characters appearing in the output)
+p-%:
+	@echo '$*=$(subst ','\'',$(subst $(newline),\n,$($*)))'
+.PHONY: p-*
+
+help: ## This help target
+	@awk '/^[a-zA-Z0-9\-_+. ]*: ##/ { print; }' $(MAKEFILE_LIST)