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Reproducible U-Boot build support, using SOURCE_DATE_EPOCH

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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@paulk.fr>
This commit is contained in:
Paul Kocialkowski 2015-07-26 18:48:15 +02:00 committed by Tom Rini
parent 9c57487752
commit f3f431a712
3 changed files with 36 additions and 4 deletions
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7
Makefile
View File

@ -1230,9 +1230,10 @@ 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"'; \
LC_ALL=C date +'#define U_BOOT_TZ "%z"')
(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"'; \
LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
endef
$(version_h): include/config/uboot.release FORCE

12
README
View File

@ -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:
======================

21
tools/default_image.c
View File

@ -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;
@ -96,9 +99,25 @@ 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, IH_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);