# Compiler and assembler
CROSS=riscv64-linux-gnu
CC = 		${CROSS}-gcc
AS = 		${CROSS}-as
LD = 		${CROSS}-ld
OBJDUMP = 	${CROSS}-objdump
SIZE = 		${CROSS}-size

# Specify the target binary (call it whatever)
TARGET = bin.elf

# QEMU command and flags
# QEMU = qemu-riscv64-static
QEMU = qemu-system-riscv64
QEMU_FLAGS += --machine virt#	# Use the virt machine
QEMU_FLAGS += --nographic#		# No graphical output

# Flags for compiler and assembler
CFLAGS += -static#				# Use static linking
CFLAGS += -nostartfiles# 		# Do not use standard startup files
CFLAGS += -nostdlib#			# Do not use standard libraries
CFLAGS += -fno-builtin#			# Do not use built-in functions
CFLAGS += -fno-common#			# Do not use common sections
CFLAGS += -march=rv64i			# Use RV64I ISA, i.e., integer only
CFLAGS += -mabi=lp64			# Use LP64 ABI, i.e., 64-bit longs and pointers, 32-bit ints
CFLAGS += -Os#					# Optimize for size

LDFLAGS += -T link.ld			# Use the linker script
LDFLAGS += --no-dynamic-linker
LDFLAGS += -m elf64lriscv
LDFLAGS += -static
LDFLAGS += -nostdlib
LDFLAGS += -s

# Use GC=0 to disable garbage collection
ifneq ($(GC), 0)
	CFLAGS += -ffreestanding
	CFLAGS += -ffunction-sections -fdata-sections
	CFLAGS += -Wl,--gc-sections
endif

# Debugging flags, passed as 'make DEBUG=1 <target>'
ifeq ($(DEBUG), 1)
	CFLAGS += -g -O0
endif

# Assembly source files
AS_SRCS := $(wildcard *.s)

# Object files
OBJS := $(AS_SRCS:.s=.o)

# Default target
all: $(OBJS)
	@$(LD) $(LDFLAGS) -o $(TARGET) $(OBJS)
	@echo "LD $(OBJS)"

# Compile assembly sources
%.o: %.s
	@$(CC) $(CFLAGS) -c -o $@ $<
	@echo "CC $<"

# Run the binary in QEMU
run: all	
	@echo "To exit: Ctrl+A, X"
	@$(QEMU) $(QEMU_FLAGS) -bios $(TARGET)

# View the text section of the binary
inspect: all
	$(OBJDUMP) -d $(TARGET)

# View the disassembly
raw: all
	$(OBJDUMP) -D $(TARGET)

# View the data section
data: all
	$(OBJDUMP) -s $(TARGET) --section=.data

# Check the size of the compiled binary
size: all
	$(SIZE) $(TARGET)

# Clean up
clean:
	rm -f $(TARGET) $(OBJS)