CPIO root filesystem is now deterministic

Makefile

@@ -42,7 +42,6 @@ run: default
 	qemu-system-x86_64 \
 		-m 512M \
 		-nographic \
-		-initrd $(OUT_DIR)/rootfs.cpio \
 		-kernel $(OUT_DIR)/bzImage
 
 # Run ncurses busybox config menu and save output
@@ -57,7 +56,6 @@ linux-config:
 	rm $(CONFIG_DIR)/linux.config
 	make $(CONFIG_DIR)/linux.config
 
-
 $(CONFIG_DIR)/busybox.config:
 	$(toolchain) " \
 		cd /cache/busybox-$(BUSYBOX_VERSION) && \
@@ -72,32 +70,6 @@ $(CONFIG_DIR)/linux.config:
 		cp .config /config/linux.config; \
 	"
 
-$(OUT_DIR)/rootfs.cpio: $(OUT_DIR)/busybox
-	mkdir -p $(CACHE_DIR)/rootfs/bin
-ifdef DEBUG
-	cp $(OUT_DIR)/busybox $(CACHE_DIR)/rootfs/bin;
-	cp $(SCRIPTS_DIR)/busybox_init $(CACHE_DIR)/rootfs/init;
-	chmod +x $(CACHE_DIR)/rootfs/init;
-endif
-	$(toolchain) " \
-		cd /cache/rootfs \
-		&& find . \
-		| cpio -o -H newc \
-		| gzip -f - > /out/rootfs.cpio \
-	"
-
-# Currently broken determinism attempt
-#    $(toolchain) " \
-#    	cd /cache/rootfs \
-#    	&& mkdir -p dev \
-#    	&& fakeroot mknod -m 0622 dev/console c 5 1 \
-#    	&& find . -mindepth 1 -execdir touch -hcd "@0" "{}" + \
-#    	&& find . -mindepth 1 -printf '%P\0' \
-#    	| sort -z \
-#    	| LANG=C bsdtar --uid 0 --gid 0 --null -cnf - -T - \
-#    	| LANG=C bsdtar --null -cf - --format=newc @- \
-#    " > $@
-
 $(OUT_DIR)/busybox: \
 	$(CACHE_DIR)/busybox-$(BUSYBOX_VERSION) \
 	$(CACHE_DIR)/busybox-$(BUSYBOX_VERSION).tar.bz2 \
@@ -109,6 +81,27 @@ $(OUT_DIR)/busybox: \
 		cp busybox /out/; \
 	"
 
+$(CACHE_DIR)/linux-$(LINUX_VERSION)/usr/gen_init_cpio: \
+	$(CACHE_DIR)/linux-$(LINUX_VERSION)
+	$(toolchain) " \
+		cd /cache/linux-$(LINUX_VERSION) && \
+		gcc usr/gen_init_cpio.c -o usr/gen_init_cpio \
+	"
+
+$(OUT_DIR)/rootfs.cpio: \
+	$(OUT_DIR)/busybox \
+	$(CACHE_DIR)/linux-$(LINUX_VERSION)/usr/gen_init_cpio
+	mkdir -p $(CACHE_DIR)/rootfs/bin
+	cp $(SCRIPTS_DIR)/busybox_init $(CACHE_DIR)/rootfs/init
+	cp $(OUT_DIR)/busybox $(CACHE_DIR)/rootfs/bin/
+	$(toolchain) " \
+		cd /cache/rootfs \
+		&& find . -mindepth 1 -execdir touch -hcd "@0" "{}" + \
+		&& find . -mindepth 1 -printf '%P\0' \
+		&& cd /cache/linux-$(LINUX_VERSION) \
+		&& usr/gen_initramfs.sh -o /out/rootfs.cpio /config/rootfs.list; \
+	"
+
 $(OUT_DIR)/bzImage: \
 	$(OUT_DIR)/rootfs.cpio \
 	$(CACHE_DIR)/linux-$(LINUX_VERSION) \
@@ -121,4 +114,3 @@ $(OUT_DIR)/bzImage: \
 		make -j$(CPUS) ARCH=$(ARCH) bzImage && \
 		cp arch/x86_64/boot/bzImage /out/; \
 	"
-

config.env

@@ -1,6 +1,12 @@
 export BUSYBOX_VERSION = 1.33.2
 export LINUX_VERSION = 5.18.5
 
+export SOURCE_DATE_EPOCH = 0
+export KBUILD_BUILD_TIMESTAMP = "1970-01-01 00:00:00 UTC"
+export KCONFIG_NOTIMESTAMP = 1
+export KBUILD_BUILD_USER = root
+export KBUILD_BUILD_HOST = QuorumOS
+
 export BUSYBOX_SERVER = https://busybox.net/downloads/
 export LINUX_SERVER = https://cdn.kernel.org/pub/linux/kernel/v5.x/
 
@@ -9,3 +15,4 @@ export LINUX_KEY = 647F28654894E3BD457199BE38DBBDC86092693E
 export LINUX_KEYS_REPO = https://git.kernel.org/pub/scm/docs/kernel/pgpkeys.git
 
 export DEBIAN_HASH = 3f1d6c17773a45c97bd8f158d665c9709d7b29ed7917ac934086ad96f92e4510
+

make/toolchain.mk

@@ -1,6 +1,6 @@
 .PHONY: toolchain-shell
 build-shell: toolchain
-	$(toolchain)
+	$(toolchain) bash
 
 .PHONY: toolchain
 toolchain:
@@ -12,13 +12,19 @@ toolchain:
 
 toolchain := \
 	docker run \
-		--interactive \
 		--rm \
+		--interactive \
 		--user=$(shell id -u):$(shell id -g) \
 		-v $(PWD)/$(CONFIG_DIR):/config \
 		-v $(PWD)/$(KEY_DIR):/keys \
 		-v $(PWD)/$(CACHE_DIR):/cache \
 		-v $(PWD)/$(OUT_DIR):/out \
+		-v $(PWD)/$(SCRIPTS_DIR):/scripts \
 		-e GNUPGHOME=/cache/.gnupg \
+		-e KBUILD_BUILD_USER=$(KBUILD_BUILD_USER) \
+		-e KBUILD_BUILD_HOST=$(KBUILD_BUILD_HOST) \
+		-e KBUILD_BUILD_TIMESTAMP=$(KBUILD_BUILD_TIMESTAMP) \
+		-e KCONFIG_NOTIMESTAMP=$(KCONFIG_NOTIMESTAMP) \
+		-e SOURCE_DATE_EPOCH=$(SOURCE_DATE_EPOCH) \
 		-t local/$(NAME)-build \
 		bash -c

scripts/busybox_init

@@ -3,9 +3,7 @@
 busybox mount -t devtmpfs none /dev
 busybox mkdir -p /dev/pts
 busybox mount -t devpts none /dev/pts
-busybox mkdir /sys
 busybox mount -t sysfs none /sys
-busybox mkdir -p /usr/bin /sbin /usr/sbin /sbin /proc /etc
 busybox mount -t proc none /proc
 
 /bin/busybox --install

targets/local/linux.config

@@ -203,7 +203,11 @@ CONFIG_NET_NS=y
 # CONFIG_SYSFS_DEPRECATED is not set
 CONFIG_RELAY=y
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_INITRAMFS_SOURCE=""
+CONFIG_INITRAMFS_SOURCE="/out/rootfs.cpio"
+CONFIG_INITRAMFS_ROOT_UID=0
+CONFIG_INITRAMFS_ROOT_GID=0
+CONFIG_INITRAMFS_COMPRESSION_GZIP=y
+
 CONFIG_RD_GZIP=y
 CONFIG_RD_BZIP2=y
 CONFIG_RD_LZMA=y

targets/local/rootfs.list

@@ -0,0 +1,12 @@
+dir  /dev                                               0755 0 0
+nod  /dev/console                                       0600 0 0 c 5 1
+dir  /sys                                               0755 0 0
+dir  /usr                                               0755 0 0
+dir  /etc                                               0755 0 0
+dir  /proc                                              0755 0 0
+dir  /bin                                               0755 0 0
+dir  /sbin                                              0755 0 0
+dir  /usr/bin                                           0755 0 0
+dir  /usr/sbin                                          0755 0 0
+file /init         /cache/rootfs/init                   0755 0 0
+file /bin/busybox  /cache/rootfs/bin/busybox            0755 0 0