From 43c1802f880471c5b69f8c622314827790aad0b8 Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mssola@mssola.com>
Date: Fri, 26 Sep 2025 23:04:36 +0200
Subject: Initial commit
MIME-Version: 1.0
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Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
---
 Makefile | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 Makefile

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..387810e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,113 @@
+##
+# By default everything is silent. If you want to change this behavior, simply
+# assign V=1 when calling make.
+
+V =
+ifeq ($(strip $(V)),)
+	E = @echo
+	Q = @
+else
+	E = @\#
+	Q =
+endif
+
+##
+# Paths.
+
+SRC            = $(wildcard src/*.S src/*.c)
+OBJ            = $(patsubst %.c,%.o,$(patsubst %.S,%.o,$(SRC)))
+EXE            = init
+ARCH           = riscv
+LINUX_SOURCE  ?=
+KERNEL         = $(LINUX_SOURCE)/arch/$(ARCH)/boot/Image
+
+##
+# Compile options. You can use CROSS_COMPILE just like on the Linux Kernel. You
+# can also determine the ISA to be used, which defaults to my VisionFive2 board.
+# I did not go too much into the rabbit hole of platform-specific flags because
+# everything is in assembly anyways and everything is statically linked. Hence
+# no `-mcpu`, no `-mtune`, no funny business.
+
+CC        = $(CROSS_COMPILE)gcc
+LD        = $(CROSS_COMPILE)gcc
+ISA      ?= rv64imafdc_zicntr_zicsr_zifencei_zihpm_zca_zcd_zba_zbb
+INCLUDES  = -Iinclude/
+ASFLAGS   = -march=$(ISA) -mabi=lp64d $(INCLUDES)
+CCFLAGS   = $(ASFLAGS) -std=gnu17
+WARNINGS  = -Werror -Wall -Wextra -Wcast-align -Wcast-qual -Winit-self \
+            -Wmissing-include-dirs -Wredundant-decls -Wshadow -Wsign-conversion \
+            -Wswitch-default -Wundef -Wunreachable-code
+CCFLAGS  += $(WARNINGS)
+LDFLAGS   = -static $(INCLUDES)
+
+##
+# Optional parameters for QEMU and gdb.
+
+QEMU_FLAGS      ?=
+GDB_EXTRA_FLAGS ?=
+
+# You can pass an optional `DEBUG` variable to manipulate the build type.
+DEBUG ?=
+ifeq ($(strip $(DEBUG)),)
+	CCFLAGS += -O3
+else
+	CCFLAGS += -g -O0 -D__DEBUG__
+endif
+
+# Image being mounted for QEMU's consumption.
+MOUNT_DEST_DIR ?= /mnt/pudc
+MOUNT_DEST_IMG ?= disk.img
+
+##
+# Targets
+
+.PHONY: all
+all: clean $(EXE)
+
+.PHONY: $(EXE)
+$(EXE): $(OBJ)
+	$(E) "	LD	" $@
+	$(Q) $(LD) $(LDFLAGS) $+ -o $(EXE)
+
+.c.o:
+	$(E) "	CC	" $(basename $@)
+	$(Q) $(CC) $(CCFLAGS) -c $< -o $@
+
+.S.o:
+	$(E) "	CC	" $(*F)
+	$(Q) $(CC) $(ASFLAGS) -c $< -o $@
+
+# Ensure that we have LINUX_SOURCE defined.
+.PHONY: qemu_env
+qemu_env:
+	$(if $(wildcard $(LINUX_SOURCE)),,$(error The 'LINUX_SOURCE' environment variable must be set to a non-empty value.))
+
+# Insert the built $(EXE) into the image to be mounted via QEMU.
+.PHONY: qemu_prepare_disk
+qemu_prepare_disk:
+	$(E) "	DISK	 $(MOUNT_DEST_IMG)"
+	$(Q) sudo mkdir -p $(MOUNT_DEST_DIR)
+	$(Q) sudo mount -o loop $(MOUNT_DEST_IMG) $(MOUNT_DEST_DIR)
+	$(Q) sudo mkdir -p $(MOUNT_DEST_DIR)/bin/ $(MOUNT_DEST_DIR)/dev/ \
+		$(MOUNT_DEST_DIR)/etc/ $(MOUNT_DEST_DIR)/proc/ $(MOUNT_DEST_DIR)/run/pudc/ \
+		$(MOUNT_DEST_DIR)/sbin/ $(MOUNT_DEST_DIR)/sys/ $(MOUNT_DEST_DIR)/tmp/
+	$(Q) sudo cp $(EXE) $(MOUNT_DEST_DIR)/sbin/$(EXE)
+	$(Q) sudo umount $(MOUNT_DEST_DIR)
+
+# Run QEMU by using the built $(KERNEL) and the $(MOUNT_DEST_IMG), which
+# contains the $(EXE) binary as '/sbin/init'.
+.PHONY: qemu
+qemu: qemu_env $(EXE) qemu_prepare_disk
+	$(E) "	QEMU	 kernel=$(KERNEL)"
+	$(Q) qemu-system-riscv64 -machine virt -smp 4 -m 8G -kernel $(KERNEL) \
+		-nographic $(QEMU_FLAGS) \
+		-drive file=$(MOUNT_DEST_IMG),format=raw,if=virtio \
+		-append "root=/dev/vda rw console=ttyS0"
+
+.PHONY: clean
+clean:
+	$(Q) rm -f $(OBJ) $(EXE)
+
+.PHONY: lint
+lint:
+	$(Q) git ls-files *.c *.h | xargs clang-format --dry-run --Werror
-- 
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