Minimal viable kernel

Makefile

@@ -0,0 +1,48 @@
+TOOLPREFIX = riscv-none-elf
+
+CC = $(TOOLPREFIX)-gcc
+AS = $(TOOLPREFIX)-as
+LD = $(TOOLPREFIX)-ld
+OBJCOPY = $(TOOLPREFIX)-objcopy
+OBJDUMP = $(TOOLPREFIX)-objdump
+
+ASFLAGS = -march=rv64gc -mabi=lp64
+
+LDFLAGS = -Tlink.ld
+LDFLAGS += -m elf64lriscv
+
+CFLAGS = -Wall -Werror -O
+CFLAGS += -mcmodel=medany
+CFLAGS += -march=rv64gc -mabi=lp64
+CFLAGS += -ffreestanding -fno-common -nostdlib -mno-relax
+
+CFLAGS += -I.
+
+CFLAGS += -fno-stack-protector # Prevents code that needs libc / runtime support
+CFLAGS += -MD # Generate header dependency files (.d)
+CFLAGS += -fno-pie -no-pie # Fixed address linking
+CFLAGS += -ggdb -gdwarf-2 # GDB debug info
+CFLAGS += -fno-omit-frame-pointer # More reliable backtraces in GDB
+
+all: kernel.elf
+
+kernel.elf: entry.o start.o
+	@echo LD $@
+	@$(LD) $(LDFLAGS) -o $@ $^
+
+%.o: %.c
+	@echo CC $@
+	@$(CC) $(CFLAGS) -nostdinc -I. -c $< -o $@
+
+%.o: %.S
+	@echo AS $@
+	@$(AS) $(ASFLAGS) -o $@ $<
+
+qemu: kernel.elf
+	@echo QEMU $@
+	@qemu-system-riscv64 -machine virt -bios none -nographic -kernel kernel.elf
+
+clean:
+	rm -f *.o *.elf *.d
+
+-include *.d