From 8a94ea4fbd7ef283af35ec5aa472a819f5a2a337 Mon Sep 17 00:00:00 2001
From: Bill Richardson <wfrichar@chromium.org>
Date: Tue, 24 Feb 2015 08:55:01 -0800
Subject: [PATCH] Add USE_GIT_DATE=1 to make args to build repeatable images

Up until now, every image includes the time of compilation in the
build information. This makes it impossible to verify that a
particular image came from a particular source code snapshot.

With this change, specifying USE_GIT_DATE=1 to the make command
will use the author date of HEAD as the timestamp. That means
that successive builds from the same source will produce
bitwise-identical output (assuming the same toolchain, of
course).

BUG=none
BRANCH=none
TEST=manual

Do this twice:

  \rm -rf build
  make BOARD=cr50 USE_GIT_DATE=1
  md5sum build/cr50/ec.bin

The md5sum should be the same for both runs.

Change-Id: If64307101a453cb13c62fa003f1bf432f4998273
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/252751
Reviewed-by: Randall Spangler <rspangler@chromium.org>
---
 Makefile.rules     | 2 +-
 util/getversion.sh | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Makefile.rules b/Makefile.rules
index 204988036e..80ac99d9b3 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -53,7 +53,7 @@ cmd_c_to_build = $(BUILDCC) $(BUILD_CFLAGS) \
 cmd_c_to_host = $(HOSTCC) $(HOST_CFLAGS) -MMD -MF $@.d  -o $@ \
 	         $(sort $(foreach c,$($(*F)-objs),util/$(c:%.o=%.c)) $*.c)
 cmd_host_test = ./util/run_host_test $* $(silent)
-cmd_date = ./util/getdate.sh > $@
+cmd_date = $(if $(USE_GIT_DATE),cat /dev/null,./util/getdate.sh) > $@
 cmd_version = ./util/getversion.sh > $@
 cmd_mv_from_tmp = mv $(out)/$*.bin.tmp $(out)/$*.bin
 cmd_extractrw-y = dd if=$(out)/$(PROJECT).bin.tmp of=$(out)/$(PROJECT).RW.bin \
diff --git a/util/getversion.sh b/util/getversion.sh
index c1da044690..798bb51448 100755
--- a/util/getversion.sh
+++ b/util/getversion.sh
@@ -31,6 +31,8 @@ fi
 
 ver="${BOARD}_${vbase}"
 
+gitdate=$(git log -1 --format='%ai' HEAD | cut -d ' ' -f '1 2')
+
 echo "/* This file is generated by util/getversion.sh */"
 
 echo "/* Version string for use by common/version.c */"
@@ -47,3 +49,8 @@ echo "/* Sub-fields for use in Makefile.rules and to form build info string"
 echo " * in common/version.c. */"
 echo "#define VERSION \"${ver}\""
 echo "#define BUILDER \"${USER}@`hostname`\""
+
+echo "/* Author date of last commit, in case compile-time is not used. */"
+echo "#ifndef DATE"
+echo "#define DATE \"${gitdate}\""
+echo "#endif"