Complete Milestone 1 - boot to long mode and init the toolchain with Makefile and CI

Makefile

@@ -0,0 +1,46 @@
+ASM      := nasm
+CC       := gcc
+LD       := ld
+OBJCOPY  := objcopy
+QEMU     := qemu-system-x86_64
+
+BOOT_DIR   := boot
+KERNEL_DIR := kernel
+OUT_DIR    := out
+
+BOOT_BIN   := $(OUT_DIR)/bootloader.bin
+KERNEL_ELF := $(OUT_DIR)/kernel.elf
+KERNEL_BIN := $(OUT_DIR)/kernel.bin
+OS_IMG     := $(OUT_DIR)/os.img
+
+ASMFLAGS := -f bin
+CFLAGS   := -ffreestanding -nostdlib -m32 -Wall -Wextra -O2 -std=c11
+LDFLAGS  := -m elf_i386 -nostdlib -Ttext 0x1000
+
+.PHONY: all build run clean
+
+all: build
+
+build: $(OS_IMG)
+
+$(OUT_DIR):
+	mkdir -p $@
+
+$(BOOT_BIN): $(BOOT_DIR)/bootloader.asm | $(OUT_DIR)
+	$(ASM) $(ASMFLAGS) -o $@ $<
+
+$(KERNEL_ELF): $(KERNEL_DIR)/kernel.c | $(OUT_DIR)
+	$(CC) $(CFLAGS) -nostartfiles -Wl,-e,kernel_main -o $@ $<
+
+$(KERNEL_BIN): $(KERNEL_ELF) | $(OUT_DIR)
+	$(OBJCOPY) -O binary $< $@
+
+$(OS_IMG): $(BOOT_BIN) $(KERNEL_BIN) | $(OUT_DIR)
+	cat $(BOOT_BIN) $(KERNEL_BIN) > $@
+	dd if=/dev/zero bs=1024 count=1440 >> $@ 2>/dev/null || true
+
+run: $(OS_IMG)
+	$(QEMU) -fda $<
+
+clean:
+	rm -rf $(OUT_DIR)

boot/bootloader.asm

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+mov ah, 0x0e
+mov al, 65 ; starting with capital A
+int 0x10
+
+; print the alphabet while alternating caps
+.loop:
+    cmp al, 120 ; 122 is for z
+    jg .done
+
+    xor al, 32 ; the space for each capital/lowercase is 32
+    inc al
+
+    int 0x10 
+    jmp .loop
+
+
+.done:
+    jmp $ ; jump to current address forever
+
+; Boot sector padding
+times 510 - ($ - $$) db 0x0
+dw 0xaa55