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openwrt/include/kernel-defaults.mk
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John Crispin 3a16a57c08 kernel: keep /init out of the root filesystem images 
The initramfs step copied /init into the root filesystem directory and
never removed it again. With CONFIG_TARGET_PER_DEVICE_ROOTFS the
initramfs kernel and the rootfs image of a device come from that same
directory. Nothing orders the two steps, so /init entered the squashfs
image or not, depending on which step ran first. The reproducible build
service reports this as a difference between the published image and a
rebuild.

Add /init to the initramfs from outside the root filesystem instead. A
built in initramfs gets it through a gen_init_cpio list file. A separate
cpio gets it appended to the finished archive. The mode is now fixed at
0755 and no longer follows the umask of the checkout.

The initramfs step also normalised the mtime of the root filesystem
directory. Do that in prepare_rootfs, so no step writes to the directory
after the image build can start.

Signed-off-by: John Crispin <john@phrozen.org>
2026-09-22 18:46:30 +02:00

282 lines
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Makefile
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# SPDX-License-Identifier: GPL-2.0-only
#
# Copyright (C) 2006-2020 OpenWrt.org
ifdef CONFIG_STRIP_KERNEL_EXPORTS
KERNEL_MAKEOPTS_IMAGE += \
EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"
endif
INITRAMFS_EXTRA_FILES ?= $(GENERIC_PLATFORM_DIR)/image/initramfs-base-files.txt
INITRAMFS_INIT_FILE := $(GENERIC_PLATFORM_DIR)/other-files/init
export HOST_EXTRACFLAGS=-I$(STAGING_DIR_HOST)/include
# defined in quilt.mk
Kernel/Patch:=$(Kernel/Patch/Default)
ifneq (,$(findstring .xz,$(LINUX_SOURCE)))
LINUX_CAT:=xzcat
else
LINUX_CAT:=$(STAGING_DIR_HOST)/bin/libdeflate-gzip -dc
endif
ifeq ($(strip $(CONFIG_EXTERNAL_KERNEL_TREE)),"")
ifeq ($(strip $(CONFIG_KERNEL_GIT_CLONE_URI)),"")
define Kernel/Prepare/Default
$(LINUX_CAT) $(DL_DIR)/$(LINUX_SOURCE) | $(TAR) -C $(KERNEL_BUILD_DIR) $(TAR_OPTIONS)
$(Kernel/Patch)
endef
else
define Kernel/Prepare/Default
$(LINUX_CAT) $(DL_DIR)/$(LINUX_SOURCE) | $(TAR) -C $(KERNEL_BUILD_DIR) $(TAR_OPTIONS)
endef
endif
else
define Kernel/Prepare/Default
mkdir -p $(KERNEL_BUILD_DIR)
if [ -d $(LINUX_DIR) ]; then \
rmdir $(LINUX_DIR); \
fi
ln -s $(CONFIG_EXTERNAL_KERNEL_TREE) $(LINUX_DIR)
if [ -d $(LINUX_DIR)/user_headers ]; then \
rm -rf $(LINUX_DIR)/user_headers; \
fi
endef
endif
ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
ifeq ($(strip $(CONFIG_EXTERNAL_CPIO)),"")
define Kernel/SetInitramfs/PreConfigure
{ \
grep -v -e INITRAMFS -e CONFIG_RD_ -e CONFIG_BLK_DEV_INITRD $(2)/.config.old > $(2)/.config; \
echo 'CONFIG_BLK_DEV_INITRD=y' >> $(2)/.config; \
echo 'file /init $(INITRAMFS_INIT_FILE) 0755 0 0' > $(2).init-cpio-list; \
echo 'CONFIG_INITRAMFS_SOURCE="$(strip $(1) $(2).init-cpio-list $(INITRAMFS_EXTRA_FILES))"' >> $(2)/.config; \
}
endef
else
define Kernel/SetInitramfs/PreConfigure
{ \
grep -v INITRAMFS $(2)/.config.old > $(2)/.config; \
echo 'CONFIG_INITRAMFS_SOURCE="$(call qstrip,$(CONFIG_EXTERNAL_CPIO))"' >> $(2)/.config; \
}
endef
endif
define Kernel/SetInitramfs
{ \
rm -f $(2)/.config.prev; \
mv $(2)/.config $(2)/.config.old; \
$(call Kernel/SetInitramfs/PreConfigure,$(1),$(2)); \
echo "# CONFIG_INITRAMFS_PRESERVE_MTIME is not set" >> $(2)/.config; \
echo "CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)" >> $(2)/.config; \
echo "CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)" >> $(2)/.config; \
$(if $(CONFIG_TARGET_INITRAMFS_FORCE), \
echo "CONFIG_INITRAMFS_FORCE=y" >> $(2)/.config;, \
echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(2)/.config;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_NONE), \
echo "CONFIG_INITRAMFS_COMPRESSION_NONE=y" >> $(2)/.config;, \
echo "# CONFIG_INITRAMFS_COMPRESSION_NONE is not set" >> $(2)/.config; ) \
$(foreach ALGO,GZIP BZIP2 LZMA LZO XZ LZ4 ZSTD, \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
echo "CONFIG_INITRAMFS_COMPRESSION_$(ALGO)=y" >> $(2)/.config; $\, \
echo "# CONFIG_INITRAMFS_COMPRESSION_$(ALGO) is not set" >> $(2)/.config; $\) \
) \
$(call Kernel/SetRamdiskCompression,$(2)/.config) \
}
endef
else
endif
define Kernel/SetRamdiskCompression
$(foreach ALGO,GZIP BZIP2 LZMA LZO XZ LZ4 ZSTD, \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
echo "CONFIG_RD_$(ALGO)=y" >> $(1); $\, \
echo "# CONFIG_RD_$(ALGO) is not set" >> $(1); $\) \
)
endef
# With a separate initramfs, the initramfs kernel differs from the regular
# kernel only in ramdisk support. Enable it here too, so that one kernel
# build serves both images.
define Kernel/SetNoInitramfs
mv $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.old
grep -v INITRAMFS $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config.set
echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(LINUX_DIR)/.config.set
echo '# CONFIG_INITRAMFS_FORCE is not set' >> $(LINUX_DIR)/.config.set
echo "# CONFIG_INITRAMFS_PRESERVE_MTIME is not set" >> $(LINUX_DIR)/.config.set
$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
echo 'CONFIG_BLK_DEV_INITRD=y' >> $(LINUX_DIR)/.config.set; \
$(call Kernel/SetRamdiskCompression,$(LINUX_DIR)/.config.set))
endef
define Kernel/Configure/Default
rm -f $(LINUX_DIR)/localversion
$(LINUX_CONF_CMD) > $(LINUX_DIR)/.config.target
# copy CONFIG_KERNEL_* settings over to .config.target
awk '/^(#[[:space:]]+)?CONFIG_KERNEL/{sub("CONFIG_KERNEL_","CONFIG_");print}' $(TOPDIR)/.config >> $(LINUX_DIR)/.config.target
echo "# CONFIG_KALLSYMS_EXTRA_PASS is not set" >> $(LINUX_DIR)/.config.target
echo "# CONFIG_KALLSYMS_ALL is not set" >> $(LINUX_DIR)/.config.target
echo "CONFIG_KALLSYMS_UNCOMPRESSED=y" >> $(LINUX_DIR)/.config.target
$(SCRIPT_DIR)/package-metadata.pl kconfig $(TMP_DIR)/.packageinfo $(TOPDIR)/.config $(KERNEL_PATCHVER) > $(LINUX_DIR)/.config.override
$(SCRIPT_DIR)/kconfig.pl 'm+' '+' $(LINUX_DIR)/.config.target /dev/null $(LINUX_DIR)/.config.override > $(LINUX_DIR)/.config.set
$(call Kernel/SetNoInitramfs)
rm -rf $(KERNEL_BUILD_DIR)/modules
cmp -s $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.prev || { \
cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config; \
cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.prev; \
}
$(_SINGLE) [ -d $(LINUX_DIR)/user_headers ] || $(KERNEL_MAKE) $(if $(findstring uml,$(BOARD)),ARCH=$(ARCH)) INSTALL_HDR_PATH=$(LINUX_DIR)/user_headers headers_install
grep '=[ym]' $(LINUX_DIR)/.config.set | LC_ALL=C sort | $(MKHASH) md5 > $(LINUX_DIR)/.vermagic
endef
define Kernel/Configure/Initramfs
$(call Kernel/SetInitramfs,$(1),$(2))
endef
# The image link reads symtab.h through EXTRA_LDSFLAGS. It sits above
# $(LINUX_DIR), so the scan below has to name it. A package built module
# changes it without a change in the kernel tree.
KERNEL_MAKE_DEPENDS_image := $(if $(CONFIG_STRIP_KERNEL_EXPORTS),$(KERNEL_BUILD_DIR)/symtab.h)
# $(1): stamp name, $(2): make targets and options, $(3): commands to run before kbuild
# kbuild takes about half a second even if nothing changed, and runs twice
# per build. Skip it if the command line did not change since its last
# successful run, and no file in the kernel tree or the toolchain is newer.
# The build system files at the top of the kernel tree are not inputs of
# kbuild, apart from .config.
define Kernel/Make
{ \
stamp=$(LINUX_DIR)/.kbuild_$(1); \
key="$$$$(printf '%s' '$(subst ','\'',$(KERNEL_MAKE) $(2))' | $(MKHASH) md5)"; \
[ "$$$$(cat $$$$stamp 2>/dev/null)" = "$$$$key" ] && [ -z "$$$$(find $(LINUX_DIR) $(TOOLCHAIN_DIR)/bin \
$(KERNEL_MAKE_DEPENDS_$(1)) \
\( -path '$(LINUX_DIR)/.*' ! -path '$(LINUX_DIR)/.config' \) -prune -o \
! -type d -newer $$$$stamp -print -quit)" ] || { \
rm -f $$$$stamp; \
$(3) \
$(KERNEL_MAKE) $(2) && echo "$$$$key" > $$$$stamp; \
}; \
}
endef
define Kernel/CompileModules/Default
+$(call Kernel/Make,modules,$(if $(KERNELNAME),$(KERNELNAME),all) modules, \
rm -f $(LINUX_DIR)/vmlinux $(LINUX_DIR)/System.map;)
# If .config did not change, use the previous timestamp to avoid package rebuilds
cmp -s $(LINUX_DIR)/.config $(LINUX_DIR)/.config.modules.save && \
mv $(LINUX_DIR)/.config.modules.save $(LINUX_DIR)/.config; \
$(CP) $(LINUX_DIR)/.config $(LINUX_DIR)/.config.modules.save
endef
OBJCOPY_STRIP = -R .reginfo -R .notes -R .note -R .comment -R .mdebug -R .note.gnu.build-id
# AMD64 shares the location with x86
ifeq ($(LINUX_KARCH),x86_64)
IMAGES_DIR:=../../x86/boot
endif
# $1: image suffix
# $2: Per Device Rootfs ID
define Kernel/CopyImage
cmp -s $(LINUX_DIR)$(2)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).debug$(2) || { \
$(KERNEL_CROSS)objcopy -O binary $(OBJCOPY_STRIP) -S $(LINUX_DIR)$(2)/vmlinux $(LINUX_KERNEL)$(1)$(2); \
$(KERNEL_CROSS)objcopy $(OBJCOPY_STRIP) -S $(LINUX_DIR)$(2)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).elf$(2); \
$(CP) $(LINUX_DIR)$(2)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).debug$(2); \
$(foreach k, \
$(if $(KERNEL_IMAGES),$(KERNEL_IMAGES),$(filter-out vmlinux dtbs,$(KERNELNAME))), \
$(CP) $(LINUX_DIR)$(2)/arch/$(LINUX_KARCH)/boot/$(IMAGES_DIR)/$(k) $(KERNEL_BUILD_DIR)/$(k)$(1)$(2); \
) \
}
endef
define Kernel/CompileImage/Default
rm -f $(TARGET_DIR)/init
+$(call Kernel/Make,image,$(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all))
$(call Kernel/CopyImage)
endef
define Kernel/PrepareConfigPerRootfs
{ \
[ ! -d "$(1)" ] || rm -rf $(1); \
mkdir $(1) && $(CP) -T $(LINUX_DIR) $(1); \
touch $(1)/.config; \
}
endef
ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
# $1: Per Device Rootfs ID
# $2: suffix of the compressed initrd
Kernel/CacheInitrd = $(CACHE_RUN) $(KERNEL_BUILD_DIR)/cache/initrd$(1).cpio.$(2) \
$(KERNEL_BUILD_DIR)/initrd$(1).cpio $(KERNEL_BUILD_DIR)/initrd$(1).cpio.$(2)
# $1: Per Device Rootfs ID
# The rootfs directory is shared with the image generation, so /init is
# appended to the finished archive instead of being staged in it.
define Kernel/AppendInitrdInit
rm -rf $(KERNEL_BUILD_DIR)/initrd-init$(1); \
mkdir -p $(KERNEL_BUILD_DIR)/initrd-init$(1); \
$(INSTALL_BIN) $(INITRAMFS_INIT_FILE) $(KERNEL_BUILD_DIR)/initrd-init$(1)/init; \
$(if $(SOURCE_DATE_EPOCH), \
touch -hcd "@$(SOURCE_DATE_EPOCH)" $(KERNEL_BUILD_DIR)/initrd-init$(1)/init;) \
( cd $(KERNEL_BUILD_DIR)/initrd-init$(1); echo ./init | \
$(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 \
-A -F $(KERNEL_BUILD_DIR)/initrd$(1).cpio )
endef
# $1: Custom TARGET_DIR. If omitted TARGET_DIR is used.
# $2: If defined Generate Per Rootfs Kernel Directory and use it
# For Separate Initramfs, the regular kernel is used as is, as its config
# already has the ramdisk support (see Kernel/SetNoInitramfs)
define Kernel/CompileImage/Initramfs
$(call locked,{ \
$(if $(2),$(call Kernel/PrepareConfigPerRootfs,$(LINUX_DIR)$(2));) \
$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),, \
$(call Kernel/Configure/Initramfs,$(if $(1),$(1),$(TARGET_DIR)),$(LINUX_DIR)$(2)); \
rm -rf $(LINUX_DIR)$(2)/usr/initramfs_data.cpio*;) \
$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
$(call locked,{ \
$(if $(call qstrip,$(CONFIG_EXTERNAL_CPIO)), \
$(CP) $(CONFIG_EXTERNAL_CPIO) $(KERNEL_BUILD_DIR)/initrd$(2).cpio;,\
( cd $(if $(1),$(1),$(TARGET_DIR)); find . | LC_ALL=C sort | $(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 > $(KERNEL_BUILD_DIR)/initrd$(2).cpio ); \
$(call Kernel/AppendInitrdInit,$(2));) \
$(if $(SOURCE_DATE_EPOCH), \
touch -hcd "@$(SOURCE_DATE_EPOCH)" $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2), \
$(STAGING_DIR_HOST)/bin/bzip2 -9 -c < $(KERNEL_BUILD_DIR)/initrd$(2).cpio > $(KERNEL_BUILD_DIR)/initrd$(2).cpio.bzip2;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP), \
$(call Kernel/CacheInitrd,$(2),gzip) \
$(STAGING_DIR_HOST)/bin/libdeflate-gzip -n -k -f -S .gzip -12 $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4), \
$(call Kernel/CacheInitrd,$(2),lz4) \
$(STAGING_DIR_HOST)/bin/lz4c -l -c1 -fz --favor-decSpeed $(KERNEL_BUILD_DIR)/initrd$(2).cpio $(KERNEL_BUILD_DIR)/initrd$(2).cpio.lz4;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA), \
$(call Kernel/CacheInitrd,$(2),lzma) \
$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(KERNEL_BUILD_DIR)/initrd$(2).cpio $(KERNEL_BUILD_DIR)/initrd$(2).cpio.lzma;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZO), \
$(STAGING_DIR_HOST)/bin/lzop -9 -f $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ), \
$(call Kernel/CacheInitrd,$(2),xz) \
$(STAGING_DIR_HOST)/bin/xz -T$(if $(filter 1,$(NPROC)),2,0) -9 -fzk --check=crc32 $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD), \
$(call Kernel/CacheInitrd,$(2),zstd) \
$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(KERNEL_BUILD_DIR)/initrd$(2).cpio.zstd $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
}, gen-cpio$(2));,\
$(KERNEL_MAKE) $(if $(2),-C $(LINUX_DIR)$(2)) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all);) \
$(call Kernel/CopyImage,-initramfs,$(2)); \
$(if $(2),rm -rf $(LINUX_DIR)$(2);) \
}, gen-initramfs$(2));
endef
else
define Kernel/CompileImage/Initramfs
endef
endif
define Kernel/Clean/Default
rm -f $(KERNEL_BUILD_DIR)/linux-$(LINUX_VERSION)/.configured
rm -f $(LINUX_KERNEL)
$(_SINGLE)$(MAKE) -C $(KERNEL_BUILD_DIR)/linux-$(LINUX_VERSION) clean
endef
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