[PATCH 3/4] Common make rules for building erofs images

4 Sep 2025

Instead of duplicating the logic in three different places, write common
code for all three makefiles to use instead.  This will make future
changes much easier.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
---
 host/rootfs/Makefile    | 51 ++++---------------------------------------------
 host/rootfs/default.nix |  1 +
 img/app/Makefile        | 42 ++++------------------------------------
 img/app/default.nix     |  1 +
 lib/erofs.mk            | 51 +++++++++++++++++++++++++++++++++++++++++++++++++
 vm/sys/net/Makefile     | 35 +++------------------------------
 vm/sys/net/default.nix  |  1 +
 7 files changed, 65 insertions(+), 117 deletions(-)

diff --git a/host/rootfs/Makefile b/host/rootfs/Makefile
index 3560707d21bcf53e4f3ad5e916d21e8be56cc3a1..dce8315fe5be19d2569d6c9a429276e4abd696ad 100644
--- a/host/rootfs/Makefile
+++ b/host/rootfs/Makefile
@@ -4,11 +4,10 @@
 .POSIX:
 
 include ../../lib/common.mk
+include ../../lib/erofs.mk
 include file-list.mk
 
-dest = build/rootfs.erofs
-
-DIRS = \
+override DIRS ::= \
 	dev \
 	etc/s6-linux-init/env \
 	etc/s6-linux-init/run-image/configs \
@@ -42,46 +41,9 @@ DIRS = \
 	proc \
 	sys
 
-FIFOS = etc/s6-linux-init/run-image/service/s6-svscan-log/fifo
-
-BUILD_FILES = build/etc/s6-rc
-
-$(dest): ../../scripts/make-erofs.sh $(PACKAGES_FILE) $(addprefix image/,$(FILES)) $(BUILD_FILES) build/empty build/fifo file-list.mk
-	( \
-	    cat $(PACKAGES_FILE) ;\
-	    for file in $(FILES) $(LINKS); do printf 'image/%s\n%s\n' $$file $$file; done ;\
-	    for file in $(BUILD_FILES); do printf '%s\n%s\n' $$file $${file#build/}; done ;\
-	    printf 'build/empty\n%s\n' $(DIRS) ;\
-	    printf 'build/fifo\n%s\n' $(FIFOS) ;\
-	) | ../../scripts/make-erofs.sh $@
-
-build/fifo:
-	mkdir -p build
-	mkfifo -m 0600 $@
-
-build/empty:
-	mkdir -p $@
+override FIFOS ::= etc/s6-linux-init/run-image/service/s6-svscan-log/fifo
 
-# s6-rc-compile's input is a directory, but that doesn't play nice
-# with Make, because it won't know to update if some file in the
-# directory is changed, or a file is created or removed in a
-# subdirectory.  Using the whole source directory could also end up
-# including files that aren't intended to be part of the input, like
-# temporary editor files or .license files.  So for all these reasons,
-# only explicitly listed files are made available to s6-rc-compile.
-build/etc/s6-rc: $(addprefix image/,$(S6_RC_FILES)) file-list.mk
-	mkdir -p $$(dirname $@)
-	rm -rf $@
-
-	dir=$$(mktemp -d) && \
-	    tar -C image -c $(S6_RC_FILES) | tar -C $$dir -x --strip-components 2 && \
-	    s6-rc-compile $@ $$dir; \
-	    exit=$$?; rm -r $$dir; exit $$exit
-
-clean:
-	-chmod -Rf +w build
-	rm -rf build
-.PHONY: clean
+all: $(dest)
 
 # veritysetup format produces two files, but Make only (portably)
 # supports one output per rule, so we combine the two outputs then
@@ -111,11 +73,6 @@ debug:
 	    $(VMLINUX)
 .PHONY: debug
 
-update-file-list:
-	../../scripts/genfiles.awk image > file-list.mk
-
-.PHONY: update-file-list
-
 run: build/live.img $(EXT_FS) build/rootfs.verity.roothash
 	@set -x && \
 	ext="$$(mktemp build/spectrum-rootfs-extfs.XXXXXXXXXX.img)" && \
diff --git a/host/rootfs/default.nix b/host/rootfs/default.nix
index 998220d7b6ed322f64ee52c704e71ec9b4643f59..561bf660829dcd5f5e2ee841662727b262d43ed3 100644
--- a/host/rootfs/default.nix
+++ b/host/rootfs/default.nix
@@ -178,6 +178,7 @@ stdenvNoCC.mkDerivation {
     fileset = fileset.intersection src (fileset.unions [
       ./.
       ../../lib/common.mk
+      ../../lib/erofs.mk
       ../../scripts/make-erofs.sh
     ]);
   };
diff --git a/img/app/Makefile b/img/app/Makefile
index 5bb1a6a2f9acd13aba95abb0e918a7f21943b230..0c3a8311973f5f82eb2af6ea3ba43f67d36dec2e 100644
--- a/img/app/Makefile
+++ b/img/app/Makefile
@@ -5,6 +5,7 @@
 .POSIX:
 
 include ../../lib/common.mk
+include ../../lib/erofs.mk
 include file-list.mk
 
 prefix = build/host
@@ -18,7 +19,6 @@ HOST_BUILD_FILES = \
 	$(imgdir)/appvm/vmlinux
 
 all: $(HOST_BUILD_FILES)
-.PHONY: all
 
 $(imgdir)/appvm/vmlinux: $(KERNEL)
 	mkdir -p $$(dirname $@)
@@ -30,38 +30,13 @@ $(imgdir)/appvm/blk/root.img: ../../scripts/make-gpt.sh ../../scripts/sfdisk-fie
 	    build/rootfs.erofs:root:5460386f-2203-4911-8694-91400125c604:root
 	mv $@.tmp $@
 
-VM_DIRS = dev run proc sys tmp \
+DIRS = dev run proc sys tmp \
 	etc/s6-linux-init/run-image/service \
 	etc/s6-linux-init/run-image/user \
 	etc/s6-linux-init/run-image/wait
-VM_FIFOS = etc/s6-linux-init/run-image/service/s6-linux-init-shutdownd/fifo
+FIFOS = etc/s6-linux-init/run-image/service/s6-linux-init-shutdownd/fifo
 
-VM_BUILD_FILES = build/etc/s6-rc
-
-build/fifo:
-	mkdir -p build
-	mkfifo -m 0600 $@
-
-build/empty:
-	mkdir -p $@
-
-build/rootfs.erofs: ../../scripts/make-erofs.sh $(PACKAGES_FILE) $(addprefix image/,$(FILES)) $(VM_BUILD_FILES) build/empty build/fifo file-list.mk
-	( \
-	    cat $(PACKAGES_FILE) ;\
-	    for file in $(FILES) $(LINKS); do printf 'image/%s\n%s\n' $$file $$file; done ;\
-	    for file in $(VM_BUILD_FILES); do printf '%s\n%s\n' $$file $${file#build/}; done ;\
-	    printf 'build/empty\n%s\n' $(VM_DIRS) ;\
-	    printf 'build/fifo\n%s\n' $(VM_FIFOS) ;\
-	) | ../../scripts/make-erofs.sh $@
-
-build/etc/s6-rc: $(addprefix image/,$(S6_RC_FILES)) file-list.mk
-	mkdir -p $$(dirname $@)
-	rm -rf $@
-
-	dir=$$(mktemp -d) && \
-	    tar -C image -c $(S6_RC_FILES) | tar -C $$dir -x --strip-components 2 && \
-	    s6-rc-compile $@ $$dir; \
-	    exit=$$?; rm -r $$dir; exit $$exit
+BUILD_FILES =
 
 debug:
 	$(GDB) -q \
@@ -138,14 +113,5 @@ run-crosvm: $(imgdir)/appvm/blk/root.img start-vhost-user-gpu start-virtiofsd
 	    $(KERNEL)
 .PHONY: run-crosvm
 
-update-file-list:
-	../../scripts/genfiles.awk image > file-list.mk
-
-.PHONY: update-file-list
-
 run: run-$(VMM)
 .PHONY: run
-
-clean:
-	rm -rf build
-.PHONY: clean
diff --git a/img/app/default.nix b/img/app/default.nix
index d3eed1f0accdc8968d1ba5bdec74ab597789082f..cf10e712ab84a9e85cb1373024be5f64deef0370 100644
--- a/img/app/default.nix
+++ b/img/app/default.nix
@@ -107,6 +107,7 @@ stdenvNoCC.mkDerivation {
     fileset = lib.fileset.intersection src (lib.fileset.unions [
       ./.
       ../../lib/common.mk
+      ../../lib/erofs.mk
       ../../scripts/make-erofs.sh
       ../../scripts/make-gpt.sh
       ../../scripts/sfdisk-field.awk
diff --git a/lib/erofs.mk b/lib/erofs.mk
new file mode 100644
index 0000000000000000000000000000000000000000..b3fc112f5e793725977cd8c4b2e71d6ed8d888c4
--- /dev/null
+++ b/lib/erofs.mk
@@ -0,0 +1,51 @@
+override basedir ::= $(dir $(lastword $(MAKEFILE_LIST)))/..
+
+override BUILD_FILES ::= $(BUILD_FILES) build/etc/s6-rc
+# No override here so that it can be overridden in host/rootfs/default.nix.
+dest ::= build/rootfs.erofs
+
+all:
+.PHONY: all
+$(dest): $(basedir)/scripts/make-erofs.sh $(PACKAGES_FILE) $(addprefix image/,$(FILES)) $(BUILD_FILES) build/empty build/fifo file-list.mk
+	set -euo pipefail; ( \
+	    cat $(PACKAGES_FILE) ;\
+	    for file in $(FILES) $(LINKS); do printf 'image/%s\n%s\n' "$$file" "$$file"; done ;\
+	    for file in $(BUILD_FILES); do printf '%s\n%s\n' "$$file" "$${file#build/}"; done ;\
+	    $(and $(DIRS),printf 'build/empty\n%s\n' $(DIRS);)\
+	    $(and $(FIFOS),printf 'build/fifo\n%s\n' $(FIFOS);)\
+	) | $(basedir)/scripts/make-erofs.sh $@
+
+clean:
+	-chmod -Rf +w build
+	rm -rf build
+.PHONY: clean
+
+build/fifo:
+	mkdir -p build
+	mkfifo -m 0600 $@
+
+build/empty:
+	mkdir -p $@
+
+update-file-list:
+	$(basedir)/scripts/genfiles.awk image > file-list.mk
+
+.PHONY: update-file-list
+.PHONY:
+	$(error cannot make .PHONY!)
+
+# s6-rc-compile's input is a directory, but that doesn't play nice
+# with Make, because it won't know to update if some file in the
+# directory is changed, or a file is created or removed in a
+# subdirectory.  Using the whole source directory could also end up
+# including files that aren't intended to be part of the input, like
+# temporary editor files or .license files.  So for all these reasons,
+# only explicitly listed files are made available to s6-rc-compile.
+build/etc/s6-rc: $(addprefix image/,$(S6_RC_FILES)) file-list.mk
+	mkdir -p build/etc
+	rm -rf $@
+	set -euo pipefail; \
+	dir=$$(mktemp -d); \
+	{ tar -C image -c $(S6_RC_FILES) | tar -C "$$dir" -x --strip-components 2;}; \
+	s6-rc-compile $@ $$dir; \
+	exit=$$?; rm -r $$dir; exit $$exit
diff --git a/vm/sys/net/Makefile b/vm/sys/net/Makefile
index e731bcea7fc61f9b2019689e52a600f3741dd55f..3f8493b9bf2364f7b2d01b7f114dba72126965cc 100644
--- a/vm/sys/net/Makefile
+++ b/vm/sys/net/Makefile
@@ -4,6 +4,7 @@
 .POSIX:
 
 include ../../../lib/common.mk
+include ../../../lib/erofs.mk
 include file-list.mk
 
 prefix = build/host
@@ -11,13 +12,14 @@ libdir = $(prefix)/lib
 vmdir = $(libdir)/spectrum/vm
 
 VMM = cloud-hypervisor
+override DIRS ::=
+override FIFOS ::=
 
 HOST_BUILD_FILES = \
 	$(vmdir)/netvm/blk/root.img \
 	$(vmdir)/netvm/vmlinux
 
 all: $(HOST_BUILD_FILES)
-.PHONY: all
 
 $(vmdir)/netvm/vmlinux: $(KERNEL)
 	mkdir -p $$(dirname $@)
@@ -29,28 +31,6 @@ $(vmdir)/netvm/blk/root.img: ../../../scripts/make-gpt.sh ../../../scripts/sfdis
 	    build/rootfs.erofs:root:ea21da27-0391-48da-9235-9d2ab2ca7844:root
 	mv $@.tmp $@
 
-VM_BUILD_FILES = build/etc/s6-rc
-
-build/empty:
-	mkdir -p $@
-
-build/rootfs.erofs: ../../../scripts/make-erofs.sh $(PACKAGES_FILE) $(addprefix image/,$(FILES)) $(VM_BUILD_FILES) build/empty file-list.mk
-	( \
-	    cat $(PACKAGES_FILE) ;\
-	    for file in $(FILES) $(LINKS); do printf 'image/%s\n%s\n' $$file $$file; done ;\
-	    for file in $(VM_BUILD_FILES); do printf '%s\n%s\n' $$file $${file#build/}; done ;\
-	    printf 'build/empty\n%s\n' $(VM_DIRS) ;\
-	) | ../../../scripts/make-erofs.sh $@
-
-build/etc/s6-rc: $(addprefix image/,$(S6_RC_FILES)) file-list.mk
-	mkdir -p $$(dirname $@)
-	rm -rf $@
-
-	dir=$$(mktemp -d) && \
-	    tar -C image -c $(S6_RC_FILES) | tar -C $$dir -x --strip-components 2 && \
-	    s6-rc-compile $@ $$dir; \
-	    exit=$$?; rm -r $$dir; exit $$exit
-
 debug:
 	$(GDB) -q \
 	    -ex 'set substitute-path .. $(LINUX_SRC)' \
@@ -102,14 +82,5 @@ run-crosvm: $(vmdir)/netvm/blk/root.img
 	    $(KERNEL)
 .PHONY: run-crosvm
 
-update-file-list:
-	../../scripts/genfiles.awk image > file-list.mk
-
-.PHONY: update-file-list
-
 run: run-$(VMM)
 .PHONY: run
-
-clean:
-	rm -rf build
-.PHONY: clean
diff --git a/vm/sys/net/default.nix b/vm/sys/net/default.nix
index b5873ebe1e80dd88c1ba997f7ebd3ee7369bb40f..7b03264bd30fe2e9157730e5338cd2501b255f7e 100644
--- a/vm/sys/net/default.nix
+++ b/vm/sys/net/default.nix
@@ -104,6 +104,7 @@ stdenvNoCC.mkDerivation {
     fileset = lib.fileset.intersection src (lib.fileset.unions [
       ./.
       ../../../lib/common.mk
+      ../../../lib/erofs.mk
       ../../../scripts/make-erofs.sh
       ../../../scripts/make-gpt.sh
       ../../../scripts/sfdisk-field.awk

-- 
2.51.0

    