[OpenWrt-Devel] [PATCH 06/13] tools/mkimage: backport SOURCE_DATE_EPOCH for reproducible builds

[Alexander Couzens]

From: bryan newbold <bnewbold at robocracy.org>

This pulls in Paul Kocialkowski's SOURCE_DATE_EPOCH support patch for u-boot,
which landed upstream circa July 2015. Note that this "host" u-boot repo is
only used to compile the 'mkimage' utility, and isn't used to actually compile
a bootloader for any target.

This patch could be removed if/when the host u-boot package is updated to a
contemporary version (but there doesn't seem to be any motivation/need to do
so).

Signed-off-by: bryan newbold <bnewbold at robocracy.org>
---
 .../090-reproducible-SOURCE_DATE_EPOCH.patch       | 102 +++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 tools/mkimage/patches/090-reproducible-SOURCE_DATE_EPOCH.patch

diff --git a/tools/mkimage/patches/090-reproducible-SOURCE_DATE_EPOCH.patch b/tools/mkimage/patches/090-reproducible-SOURCE_DATE_EPOCH.patch
new file mode 100644
index 0000000..f9c6360
--- /dev/null
+++ b/tools/mkimage/patches/090-reproducible-SOURCE_DATE_EPOCH.patch
@@ -0,0 +1,102 @@
+From f3f431a712729a1af94d01bd1bfde17a252ff02c Mon Sep 17 00:00:00 2001
+From: Paul Kocialkowski <contact at paulk.fr>
+Date: Sun, 26 Jul 2015 18:48:15 +0200
+Subject: [PATCH] Reproducible U-Boot build support, using SOURCE_DATE_EPOCH
+
+In order to achieve reproducible builds in U-Boot, timestamps that are defined
+at build-time have to be somewhat eliminated. The SOURCE_DATE_EPOCH environment
+variable allows setting a fixed value for those timestamps.
+
+Simply by setting SOURCE_DATE_EPOCH to a fixed value, a number of targets can be
+built reproducibly. This is the case for e.g. sunxi devices.
+
+However, some other devices might need some more tweaks, especially regarding
+the image generation tools.
+
+Signed-off-by: Paul Kocialkowski <contact at paulk.fr>
+---
+ Makefile              |  7 ++++---
+ README                | 12 ++++++++++++
+ tools/default_image.c | 21 ++++++++++++++++++++-
+ 3 files changed, 36 insertions(+), 4 deletions(-)
+
+diff --git a/Makefile b/Makefile
+index 5e33043..394ed09 100644
+--- a/Makefile
++++ b/Makefile
+@@ -1110,8 +1110,9 @@ define filechk_version.h
+ endef
+ 
+ define filechk_timestamp.h
+-	(LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
+-	LC_ALL=C date +'#define U_BOOT_TIME "%T"')
++	(SOURCE_DATE="$${SOURCE_DATE_EPOCH:+@$$SOURCE_DATE_EPOCH}"; \
++	LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
++	LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_TIME "%T"')
+ endef
+ 
+ $(version_h): include/config/uboot.release FORCE
+diff --git a/README b/README
+index 4e0ff9f..1bcb63c 100644
+--- a/README
++++ b/README
+@@ -5081,6 +5081,18 @@ This firmware often needs to be loaded during U-Boot booting.
+ - CONFIG_SYS_MEM_TOP_HIDE_MIN
+ 	Define minimum DDR size to be hided from top of the DDR memory
+ 
++Reproducible builds
++-------------------
++
++In order to achieve reproducible builds, timestamps used in the U-Boot build
++process have to be set to a fixed value.
++
++This is done using the SOURCE_DATE_EPOCH environment variable.
++SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
++option for U-Boot or an environment variable in U-Boot.
++
++SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
++
+ Building the Software:
+ ======================
+ 
+diff --git a/tools/default_image.c b/tools/default_image.c
+index cf5c0d4..18940af 100644
+--- a/tools/default_image.c
++++ b/tools/default_image.c
+@@ -88,6 +88,9 @@ static void image_set_header(void *ptr, struct stat *sbuf, int ifd,
+ 				struct image_tool_params *params)
+ {
+ 	uint32_t checksum;
++	char *source_date_epoch;
++	struct tm *time_universal;
++	time_t time;
+ 
+ 	image_header_t * hdr = (image_header_t *)ptr;
+ 
+@@ -100,9 +103,25 @@ static void image_set_header(void *ptr, struct stat *sbuf, int ifd,
+ 				sizeof(image_header_t)),
+ 			sbuf->st_size - sizeof(image_header_t));
+ 
++	source_date_epoch = getenv("SOURCE_DATE_EPOCH");
++	if (source_date_epoch != NULL) {
++		time = (time_t) strtol(source_date_epoch, NULL, 10);
++
++		time_universal = gmtime(&time);
++		if (time_universal == NULL) {
++			fprintf(stderr, "%s: SOURCE_DATE_EPOCH is not valid\n",
++				__func__);
++			time = 0;
++		} else {
++			time = mktime(time_universal);
++		}
++	} else {
++		time = sbuf->st_mtime;
++	}
++
+ 	/* Build new header */
+ 	image_set_magic(hdr, params->magic);
+-	image_set_time(hdr, sbuf->st_mtime);
++	image_set_time(hdr, time);
+ 	image_set_size(hdr, sbuf->st_size - sizeof(image_header_t));
+ 	image_set_load(hdr, params->addr);
+ 	image_set_ep(hdr, params->ep);
-- 
2.7.0
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