From d78dec3e19e3f2ab0f14ba6819357d50156b30b8 Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Mon, 16 Sep 2024 18:38:16 +0200
Subject: [PATCH] kernel: copy kernel build dir on Per-Device Initramfs
 compilation

To speedup compilation of Per-Device Initramfs, copy the kernel build
directory for each rootfs ID.

This permits concurrent execution of kernel build without conflicting
with each other at the expense of additional disk space usage.

To limit disk space usage, the copied kernel directory is deleted after
the Per-Device Initramfs image is generated and saved.

Link: https://github.com/openwrt/openwrt/pull/16404
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 include/kernel-defaults.mk | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index fc1262aad3..e9e36d72b6 100644
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -153,13 +153,13 @@ endif
 # $1: image suffix
 # $2: Per Device Rootfs ID
 define Kernel/CopyImage
-	cmp -s $(LINUX_DIR)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).debug$(2) || { \
-		$(KERNEL_CROSS)objcopy -O binary $(OBJCOPY_STRIP) -S $(LINUX_DIR)/vmlinux $(LINUX_KERNEL)$(1)$(2); \
-		$(KERNEL_CROSS)objcopy $(OBJCOPY_STRIP) -S $(LINUX_DIR)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).elf$(2); \
-		$(CP) $(LINUX_DIR)/vmlinux $(KERNEL_BUILD_DIR)/vmlinux$(1).debug$(2); \
+	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) $(LINUX_DIR)/arch/$(LINUX_KARCH)/boot/$(IMAGES_DIR)/$(k) $(KERNEL_BUILD_DIR)/$(k)$(1)$(2); \
+			$(CP) $(LINUX_DIR)$(2)/arch/$(LINUX_KARCH)/boot/$(IMAGES_DIR)/$(k) $(KERNEL_BUILD_DIR)/$(k)$(1)$(2); \
 		) \
 	}
 endef
@@ -173,7 +173,9 @@ endef
 define Kernel/PrepareConfigPerRootfs
 	{ \
 		[ ! -d "$(1)" ] || rm -rf $(1); \
-		mkdir $(1) && $(CP) $(LINUX_DIR)/.config $(1); \
+		mkdir $(1) && $(CP) -T $(LINUX_DIR) $(1); \
+		touch $(1)/.config; \
+		rm -rf $(1)/usr/initramfs_data.cpio*; \
 	}
 endef
 
@@ -209,10 +211,9 @@ define Kernel/CompileImage/Initramfs
 			$(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);) \
+			$(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$(if $(2),-$(2)));
 endef
 else
-- 
2.30.2