[ptxdist] [PATCH 2/3] barebox: add option for building barebox reproducibly

["Baeuerle, Florian" <Florian.Baeuerle@allegion.com>]

Inject fake timestamps into the build via faketime to produce the exact
same binaries.

Signed-off-by: Florian Bäuerle <florian.baeuerle@allegion.com>
---
 platforms/barebox.in | 10 ++++++++++
 rules/barebox.make   | 16 +++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/platforms/barebox.in b/platforms/barebox.in
index 645366e93..5bc2f08b6 100644
--- a/platforms/barebox.in
+++ b/platforms/barebox.in
@@ -13,6 +13,7 @@ menuconfig BAREBOX
 	select HOST_OPENSSL if BAREBOX_NEEDS_HOST_OPENSSL
 	select HOST_IMX_CST if BAREBOX_NEEDS_HOST_IMX_CST
 	select HOST_LZOP if BAREBOX_NEEDS_HOST_LZOP
+	select HOST_FAKETIME if BAREBOX_REPRODUCIBLE
 	prompt "barebox                       "
 	bool
 	help
@@ -50,6 +51,15 @@ config BAREBOX_EXTRA_ENV_PATH
 	  Directories and files to add to the builtin barebox environment.
 	  Relative paths must be relative to the platformconfigdir.
 
+config BAREBOX_REPRODUCIBLE
+	prompt "build reproducibly"
+	bool
+	default n
+	help
+	  With this, fake timestamps are injected to the barebox build, so the
+	  resulting barebox images are identical when the sources haven't been
+	  changed.
+
 config BAREBOX_BAREBOXENV
 	prompt "install 'bareboxenv'"
 	bool
diff --git a/rules/barebox.make b/rules/barebox.make
index a6ec3c394..ad160b3ba 100644
--- a/rules/barebox.make
+++ b/rules/barebox.make
@@ -45,6 +45,20 @@ BAREBOX_ENV := \
 	KCONFIG_NOTIMESTAMP=1 \
 	pkg_wrapper_blacklist="$(BAREBOX_WRAPPER_BLACKLIST)"
 
+ifdef PTXCONF_BAREBOX_REPRODUCIBLE
+BAREBOX_FAKE_TIMESTAMP := \
+	$(shell echo $(BAREBOX_VERSION) | \
+		sed -E "s/([0-9]{4})\.([0-9]{1,2}).*/\1-\2-01 00:00:00/")
+BAREBOX_FAKETIME := faketime -f "$(BAREBOX_FAKE_TIMESTAMP)"
+BAREBOX_ENV := $(BAREBOX_ENV) \
+	KBUILD_BUILD_TIMESTAMP="$(BAREBOX_FAKE_TIMESTAMP)" \
+	KBUILD_BUILD_VERSION="0" \
+	KBUILD_BUILD_USER="ptxdist" \
+	KBUILD_BUILD_HOST="ptxdist"
+else
+BAREBOX_FAKETIME :=
+endif
+
 BAREBOX_MAKEVARS := \
 	V=$(PTXDIST_VERBOSE) \
 	HOSTCC=$(HOSTCC) \
@@ -113,7 +127,7 @@ ifdef PTXCONF_BAREBOX_EXTRA_ENV
 endif
 
 	@+cd $(BAREBOX_DIR) && $(BAREBOX_PATH) $(BAREBOX_ENV) \
-		$(MAKE) $(BAREBOX_MAKEVARS)
+		$(BAREBOX_FAKETIME) $(MAKE) $(BAREBOX_MAKEVARS)
 	@$(call touch)
 
 # ----------------------------------------------------------------------------
-- 
2.19.0

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