[openwrt/openwrt] build: make find_md5 reproducible with AUTOREMOVE

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch openwrt-22.03:
https://git.openwrt.org/d419136ad5bfa0449083b1a07a9a265cea20dcd5

commit d419136ad5bfa0449083b1a07a9a265cea20dcd5
Author: Christian Marangi <ansuelsmth at gmail.com>
AuthorDate: Tue Sep 6 16:48:37 2022 +0200

    build: make find_md5 reproducible with AUTOREMOVE
    
    While experimenting with the AUTOREMOVE option in search of a way to use
    prebuilt host tools in different buildroot, it was discovered that the
    md5 generated by find_md5 in depends.mk is not reproducible.
    
    Currently the hash is generated by the path of the file in addition to
    the file mod time. Out of confusion, probably, there was an idea that
    such command was used on the package build_dir. Reality is that this
    command is run on the package files. (Makefile, patches, src)
    
    This is problematic because the package Makefile (for example) change at
    each git clone and base the hash on the Makefile mtime doesn't really
    reflect if the Makefile actually changes across a buildroot or not.
    
    A better approach is to generate an hash of each file and then generate
    an hash on the sort hash list. This way we remove the problem of git
    clone setting a wrong mtime while keeping the integrity of checking if a
    file changed for the package as any change will result in a different
    hash.
    
    Introduce a new kind of find_md5 function, find_md5_reproducible that
    apply this new logic and limit it only with AUTOREMOVE option set to
    prevent any kind of slowdown due to additional hash generation.
    
    Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
    (cherry picked from commit 53a08e37437972ba0a8fbf953a93a70a6b784ef4)
---
 include/depends.mk      | 1 +
 include/host-build.mk   | 2 +-
 include/kernel-build.mk | 2 +-
 include/package.mk      | 2 +-
 4 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/depends.mk b/include/depends.mk
index 465e4e952a..8ab80daf39 100644
--- a/include/depends.mk
+++ b/include/depends.mk
@@ -12,6 +12,7 @@
 DEP_FINDPARAMS := -x "*/.svn*" -x ".*" -x "*:*" -x "*\!*" -x "* *" -x "*\\\#*" -x "*/.*_check" -x "*/.*.swp" -x "*/.pkgdir*"
 
 find_md5=find $(wildcard $(1)) -type f $(patsubst -x,-and -not -path,$(DEP_FINDPARAMS) $(2)) -printf "%p%T@\n" | sort | $(MKHASH) md5
+find_md5_reproducible=find $(wildcard $(1)) -type f $(patsubst -x,-and -not -path,$(DEP_FINDPARAMS) $(2)) -print0 | xargs -0 $(MKHASH) md5 | sort | $(MKHASH) md5
 
 define rdep
   .PRECIOUS: $(2)
diff --git a/include/host-build.mk b/include/host-build.mk
index 7f76eb1a2f..c6f594be35 100644
--- a/include/host-build.mk
+++ b/include/host-build.mk
@@ -21,7 +21,7 @@ include $(INCLUDE_DIR)/depends.mk
 include $(INCLUDE_DIR)/quilt.mk
 
 BUILD_TYPES += host
-HOST_STAMP_PREPARED=$(HOST_BUILD_DIR)/.prepared$(if $(HOST_QUILT)$(DUMP),,$(shell $(call find_md5,${CURDIR} $(PKG_FILE_DEPENDS),))_$(call confvar,CONFIG_AUTOREMOVE $(HOST_PREPARED_DEPENDS)))
+HOST_STAMP_PREPARED=$(HOST_BUILD_DIR)/.prepared$(if $(HOST_QUILT)$(DUMP),,$(shell $(call $(if $(CONFIG_AUTOREMOVE),find_md5_reproducible,find_md5),${CURDIR} $(PKG_FILE_DEPENDS),))_$(call confvar,CONFIG_AUTOREMOVE $(HOST_PREPARED_DEPENDS)))
 HOST_STAMP_CONFIGURED:=$(HOST_BUILD_DIR)/.configured
 HOST_STAMP_BUILT:=$(HOST_BUILD_DIR)/.built
 HOST_BUILD_PREFIX?=$(if $(IS_PACKAGE_BUILD),$(STAGING_DIR_HOSTPKG),$(STAGING_DIR_HOST))
diff --git a/include/kernel-build.mk b/include/kernel-build.mk
index 80da4455bc..5dd033cda6 100644
--- a/include/kernel-build.mk
+++ b/include/kernel-build.mk
@@ -10,7 +10,7 @@ ifneq ($(DUMP),1)
 endif
 
 KERNEL_FILE_DEPENDS=$(GENERIC_BACKPORT_DIR) $(GENERIC_PATCH_DIR) $(GENERIC_HACK_DIR) $(PATCH_DIR) $(GENERIC_FILES_DIR) $(FILES_DIR)
-STAMP_PREPARED=$(LINUX_DIR)/.prepared$(if $(QUILT)$(DUMP),,_$(shell $(call find_md5,$(KERNEL_FILE_DEPENDS),)))
+STAMP_PREPARED=$(LINUX_DIR)/.prepared$(if $(QUILT)$(DUMP),,_$(shell $(call $(if $(CONFIG_AUTOREMOVE),find_md5_reproducible,find_md5),$(KERNEL_FILE_DEPENDS),)))
 STAMP_CONFIGURED:=$(LINUX_DIR)/.configured
 include $(INCLUDE_DIR)/download.mk
 include $(INCLUDE_DIR)/quilt.mk
diff --git a/include/package.mk b/include/package.mk
index 509ef61e08..4220f624ff 100644
--- a/include/package.mk
+++ b/include/package.mk
@@ -85,7 +85,7 @@ ifneq ($(PREV_STAMP_PREPARED),)
   STAMP_PREPARED:=$(PREV_STAMP_PREPARED)
   CONFIG_AUTOREBUILD:=
 else
-  STAMP_PREPARED=$(PKG_BUILD_DIR)/.prepared$(if $(QUILT)$(DUMP),,_$(shell $(call find_md5,${CURDIR} $(PKG_FILE_DEPENDS),))_$(call confvar,CONFIG_AUTOREMOVE $(PKG_PREPARED_DEPENDS)))
+  STAMP_PREPARED=$(PKG_BUILD_DIR)/.prepared$(if $(QUILT)$(DUMP),,_$(shell $(call $(if $(CONFIG_AUTOREMOVE),find_md5_reproducible,find_md5),${CURDIR} $(PKG_FILE_DEPENDS),))_$(call confvar,CONFIG_AUTOREMOVE $(PKG_PREPARED_DEPENDS)))
 endif
 STAMP_CONFIGURED=$(PKG_BUILD_DIR)/.configured$(if $(DUMP),,_$(call confvar,$(PKG_CONFIG_DEPENDS)))
 STAMP_CONFIGURED_WILDCARD=$(PKG_BUILD_DIR)/.configured_*