kernel: set options to make external initramfs reproducible

Run cpio as well as compressors in such ways that they are generating
reproducible output.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index 5a061a5178649cda31849b0879d6a491dc024b19..af1d59c481041dd25cdf745a2501287670593339 100644 (file)
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -174,13 +174,14 @@ ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),y)
 ifneq ($(qstrip $(CONFIG_EXTERNAL_CPIO)),)
        $(CP) $(CONFIG_EXTERNAL_CPIO) $(KERNEL_BUILD_DIR)/initrd.cpio
 else
-       ( cd $(TARGET_DIR); find . | $(STAGING_DIR_HOST)/bin/cpio -o -H newc -R 0:0 > $(KERNEL_BUILD_DIR)/initrd.cpio )
+       ( cd $(TARGET_DIR); find . | LC_ALL=C sort | $(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 > $(KERNEL_BUILD_DIR)/initrd.cpio )
 endif
+       $(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(KERNEL_BUILD_DIR)/initrd.cpio)
        $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),bzip2 -9 -c < $(KERNEL_BUILD_DIR)/initrd.cpio > $(KERNEL_BUILD_DIR)/initrd.cpio.bzip2)
-       $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),gzip -f -S .gzip -9n $(KERNEL_BUILD_DIR)/initrd.cpio)
+       $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),gzip -n -f -S .gzip -9n $(KERNEL_BUILD_DIR)/initrd.cpio)
        $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA),$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(KERNEL_BUILD_DIR)/initrd.cpio $(KERNEL_BUILD_DIR)/initrd.cpio.lzma)
 # ?    $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZO),)
-       $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ),$(STAGING_DIR_HOST)/bin/xz -9 -fz --check=crc32 $(KERNEL_BUILD_DIR)/initrd.cpio)
+       $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ),$(STAGING_DIR_HOST)/bin/xz -T0 -9 -fz --check=crc32 $(KERNEL_BUILD_DIR)/initrd.cpio)
 # ?    $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4),)
        $(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD),$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(KERNEL_BUILD_DIR)/initrd.cpio.zstd $(KERNEL_BUILD_DIR)/initrd.cpio)
 endif