From 52cc9d82f1138e28dcf590fbe60c8a69635abcea Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Mon, 16 Sep 2024 18:34:09 +0200
Subject: [PATCH] kernel: rework Initramfs locking logic

Rework CompileImage/Initramfs locking logic to fix race condition on
concurrent access/compilation.

Rework each intermediate step and group them under one single execution
block. Protect this with a new lock, 'gen-initramfs' and rename the
compile initramfs to compile-initramfs lock name.

This is done to handle corner case scenario where a rootfs with the same
hash ID is generated at the same time. To handle this, we execute
everything under lock and use a specific hash ID lock to prevent
concurrent access/compilation.

Link: https://github.com/openwrt/openwrt/pull/16404
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 include/kernel-defaults.mk | 141 +++++++++++++++++++++----------------
 1 file changed, 80 insertions(+), 61 deletions(-)

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index f6997ecf9e..fc1262aad3 100644
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -48,42 +48,56 @@ endif
 ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
   ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),y)
     define Kernel/SetInitramfs/PreConfigure
-	grep -v -e CONFIG_BLK_DEV_INITRD $(2)/.config.old > $(2)/.config
-	echo 'CONFIG_BLK_DEV_INITRD=y' >> $(2)/.config
-	echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(2)/.config
-    endef
-  else
-  ifeq ($(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' >> $(2)/.config
-	echo 'CONFIG_INITRAMFS_SOURCE="$(strip $(1) $(INITRAMFS_EXTRA_FILES))"' >> $(2)/.config
+	{ \
+		grep -v -e CONFIG_BLK_DEV_INITRD $(2)/.config.old > $(2)/.config; \
+		echo 'CONFIG_BLK_DEV_INITRD=y' >> $(2)/.config; \
+		echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(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))"' >> $(2)/.config
-    endef
+    ifeq ($(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' >> $(2)/.config; \
+		echo 'CONFIG_INITRAMFS_SOURCE="$(strip $(1) $(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
   endif
-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" >> $(2)/.config
-  ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),y)
-	echo 'CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)' >> $(2)/.config
-	echo 'CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)' >> $(2)/.config
-	echo "$(if $(CONFIG_TARGET_INITRAMFS_FORCE),CONFIG_INITRAMFS_FORCE=y,# CONFIG_INITRAMFS_FORCE is not set)" >> $(2)/.config
-  else
-	echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(2)/.config
-  endif
-	echo "$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_NONE),CONFIG_INITRAMFS_COMPRESSION_NONE=y,# 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 -e "CONFIG_INITRAMFS_COMPRESSION_$(ALGO)=y\nCONFIG_RD_$(ALGO)=y" >> $(2)/.config;,\
-			echo -e "# CONFIG_INITRAMFS_COMPRESSION_$(ALGO) is not set\n# CONFIG_RD_$(ALGO) is not set" >> $(2)/.config;))
+	{ \
+		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; \
+		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),,echo "CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)" >> $(2)/.config;) \
+		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),,echo "CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)" >> $(2)/.config;) \
+		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
+			echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(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; $\) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
+				echo "CONFIG_RD_$(ALGO)=y" >> $(2)/.config; $\, \
+				echo "# CONFIG_RD_$(ALGO) is not set" >> $(2)/.config; $\) \
+		) \
+	}
   endef
 else
 endif
@@ -157,10 +171,10 @@ define Kernel/CompileImage/Default
 endef
 
 define Kernel/PrepareConfigPerRootfs
-	[ ! -d "$(1)" ] || rm -rf $(1)
-	mkdir $(1)
-
-	$(CP) $(LINUX_DIR)/.config $(1)
+	{ \
+		[ ! -d "$(1)" ] || rm -rf $(1); \
+		mkdir $(1) && $(CP) $(LINUX_DIR)/.config $(1); \
+	}
 endef
 
 ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
@@ -169,32 +183,37 @@ ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
 # For Separate Initramf with $2 declared, skip kernel compile, it has
 # already been done previously on generic image build
 define Kernel/CompileImage/Initramfs
-	$(if $(2),$(call Kernel/PrepareConfigPerRootfs,$(LINUX_DIR)$(2)))
-	$(call Kernel/Configure/Initramfs,$(if $(1),$(1),$(TARGET_DIR)),$(LINUX_DIR)$(2))
-	$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(if $(1),$(1),$(TARGET_DIR))/init
-	$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(if $(1),$(1),$(TARGET_DIR)) $(if $(1),$(1),$(TARGET_DIR))/init)
-ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),y)
-ifneq ($(call qstrip,$(CONFIG_EXTERNAL_CPIO)),)
-	$(CP) $(CONFIG_EXTERNAL_CPIO) $(KERNEL_BUILD_DIR)/initrd.cpio$(2)
-else
-	( cd $(if $(1),$(1),$(TARGET_DIR)); find . | LC_ALL=C sort | $(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 > $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio )
-endif
-	$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),$(STAGING_DIR_HOST)/bin/bzip2 -9 -c < $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio > $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.bzip2)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),$(STAGING_DIR_HOST)/bin/libdeflate-gzip -n -f -S .gzip -12 $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4),$(STAGING_DIR_HOST)/bin/lz4c -l -c1 -fz --favor-decSpeed $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA),$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.lzma)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZO),$(STAGING_DIR_HOST)/bin/lzop -9 -f $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ),$(STAGING_DIR_HOST)/bin/xz -T$(if $(filter 1,$(NPROC)),2,0) -9 -fz --check=crc32 $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD),$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.zstd $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio)
-	$(if $(2),,$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all))
-	$(call Kernel/CopyImage,-initramfs,$(2))
-else
-	+$(call locked,$(if $(2),$(CP) $(LINUX_DIR)$(2)/.config* $(LINUX_DIR) && touch $(LINUX_DIR)/.config && )\
-		rm -rf $(LINUX_DIR)/usr/initramfs_data.cpio* $(LINUX_DIR)/.config.prev && \
-		$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all) && \
-		{ $(call Kernel/CopyImage,-initramfs,$(2)) },gen-initramfs)
-endif
+	$(call locked,{ \
+		$(if $(2),$(call Kernel/PrepareConfigPerRootfs,$(LINUX_DIR)$(2));) \
+		$(call Kernel/Configure/Initramfs,$(if $(1),$(1),$(TARGET_DIR)),$(LINUX_DIR)$(2)); \
+		$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(if $(1),$(1),$(TARGET_DIR))/init; \
+		$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(if $(1),$(1),$(TARGET_DIR)) $(if $(1),$(1),$(TARGET_DIR))/init;) \
+		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
+			$(if $(call qstrip,$(CONFIG_EXTERNAL_CPIO)), \
+				$(CP) $(CONFIG_EXTERNAL_CPIO) $(KERNEL_BUILD_DIR)/initrd.cpio;,\
+				( cd $(if $(1),$(1),$(TARGET_DIR)); find . | LC_ALL=C sort | $(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 > $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio );) \
+			$(if $(SOURCE_DATE_EPOCH), \
+				touch -hcd "@$(SOURCE_DATE_EPOCH)" $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2), \
+				$(STAGING_DIR_HOST)/bin/bzip2 -9 -c < $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio > $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.bzip2;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP), \
+				$(STAGING_DIR_HOST)/bin/libdeflate-gzip -n -f -S .gzip -12 $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4), \
+				$(STAGING_DIR_HOST)/bin/lz4c -l -c1 -fz --favor-decSpeed $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA), \
+				$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.lzma;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZO), \
+				$(STAGING_DIR_HOST)/bin/lzop -9 -f $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ), \
+				$(STAGING_DIR_HOST)/bin/xz -T$(if $(filter 1,$(NPROC)),2,0) -9 -fz --check=crc32 $(KERNEL_BUILD_DIR)/initrd.cpio;) \
+			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD), \
+				$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio.zstd $(if $(2),$(LINUX_DIR)$(2),$(KERNEL_BUILD_DIR))/initrd.cpio;) \
+			$(if $(2),,$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all);),\
+			$(call locked,$(if $(2),$(CP) $(LINUX_DIR)$(2)/.config* $(LINUX_DIR) && touch $(LINUX_DIR)/.config && ) \
+				rm -rf $(LINUX_DIR)/usr/initramfs_data.cpio* $(LINUX_DIR)/.config.prev && \
+				$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all), compile-initramfs);) \
+		$(call Kernel/CopyImage,-initramfs,$(2)); \
+	}, gen-initramfs$(if $(2),-$(2)));
 endef
 else
 define Kernel/CompileImage/Initramfs
-- 
2.30.2