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 <[email protected]>

Quoted 7 lines · Paul Kocialkowski

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.

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

--

Hi,

Quoted 9 lines · Tom Rini

Quoted 7 lines · Paul Kocialkowski

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.

Quoted 8 lines

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

--

This commit breaks the following commit:

commit f3f431a712729a1af94d01bd1bfde17a252ff02c

Author: Chris Packham <[email protected]>
Date:   Sun May 10 21:02:09 2015 +1200

Makefile: Add U_BOOT_TZ and include in version

Define U_BOOT_TZ alongside U_BOOT_TIME and U_BOOT_DATE and use it to include the timezone in the version output.

Acked-by Simon Glass <[email protected]>

Signed-off-by Chris Packham <[email protected]>

Before this commit I have:
U-Boot 2015.07-00345-g9c57487 (Jul 31 2015 - 10:49:31 +0800)

After this commit I have:
U-Boot 2015.07-00346-gf3f431a (Jul 31 2015 - 02:50:54 +0000)

As you see: the timezone information is missing, and U-Boot's timestamp is now GMT+0 (the correct one should be GMT+8)

Is this intended behavior? Or if not, please fix it.

Regards,
Bin

When building with SOURCE_DATE_EPOCH the timezone is in UTC. When building normally the timezone is taken from the build machine's locale setting.

Fixes f3f431a71272 ("Reproducible U-Boot build support, using

SOURCE_DATE_EPOCH")

Signed-off-by Chris Packham <[email protected]>

---
Hopefully this will suit everyone. I've done a quick sanity test with sandbox and the date shown in the version output looks to be what I expect with/without SOURCE_DATE_EPOCH.

 Makefile | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Makefile +4 -4

index 394ed09..f75c730 100644
@@ -1230,10 +1230,16 @@ define filechk_version.h
 endef
 
 define filechk_timestamp.h
-       (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 "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
+       (if test -n "$${SOURCE_DATE_EPOCH}"; then \
+               SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
+               LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+               LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \

When building with SOURCE_DATE_EPOCH the timezone is in UTC. When building normally the timezone is taken from the build machine's locale setting.

Fixes f3f431a71272 ("Reproducible U-Boot build support, using

SOURCE_DATE_EPOCH")

Signed-off-by Chris Packham <[email protected]>

---
Hopefully this will suit everyone. I've done a quick sanity test with sandbox and the date shown in the version output looks to be what I expect with/without SOURCE_DATE_EPOCH.

 Makefile | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Makefile +3 -4

index 394ed09..f75c730 100644
@@ -1230,10 +1230,16 @@ define filechk_version.h
 endef
 
 define filechk_timestamp.h
-	(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 "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
+	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
+		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
+		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \

Le vendredi 31 juillet 2015 ? 22:04 +1200, Chris Packham a ?crit :

Quoted 3 lines

When building with SOURCE_DATE_EPOCH the timezone is in UTC. When building normally the timezone is taken from the build machine's locale setting.

Thanks a lot for introducing this, I thought it might disturb a few people.

Quoted 2 lines

Fixes f3f431a71272 ("Reproducible U-Boot build support, using

SOURCE_DATE_EPOCH")

It is incorrect to say that your patch fixes my commit, because my commit didn't introduce anything unexpected or faulty.

If anything, it was merged before people gave their opinion about whether UTC should be default. I was also going to introduce a patch like yours later. For the record, UTC is default for Coreboot's timestamps.

Thus, please remove that line.

Otherwise, this is:

Tested-by Paul Kocialkowski <[email protected]>

Quoted 34 lines

Signed-off-by Chris Packham <[email protected]>

---
Hopefully this will suit everyone. I've done a quick sanity test with sandbox and the date shown in the version output looks to be what I expect with/without SOURCE_DATE_EPOCH.

 Makefile | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Makefile +10 -4

index 394ed09..f75c730 100644
@@ -1230,10 +1230,16 @@ define filechk_version.h
 endef
 
 define filechk_timestamp.h
-     (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 "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
+     (if test -n "$${SOURCE_DATE_EPOCH}"; then \
+             SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
+             LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+             LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+             LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+     else \
+             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"'; \
+     fi)
 endef
 
 $(version_h): include/config/uboot.release FORCE

When building with SOURCE_DATE_EPOCH the timezone is in UTC. When building normally the timezone is taken from the build machine's locale setting.

Signed-off-by Chris Packham <[email protected]>

Tested-by Bin Meng <[email protected]>

Tested-by Paul Kocialkowski <[email protected]>

---

Changes in v2:
- Collect some tested-by tags
- Remove reference to f3f431a71272 in the commit message
- Drop Ccs that were erroneously added when submitting v1, remaining Ccs are from the original mailing list thread

 Makefile | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Makefile +10 -5

index 394ed09..f75c730 100644
@@ -1230,10 +1230,16 @@ define filechk_version.h
 endef
 
 define filechk_timestamp.h
-       (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 "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
+       (if test -n "$${SOURCE_DATE_EPOCH}"; then \
+               SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
+               LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+               LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+               LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+       else \
+               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"'; \
+       fi)
 endef
 
 $(version_h): include/config/uboot.release FORCE
--

2.5.0.rc0

The problem is that date -u implies UTC. So +0000 is right if you do want the time to be displayed in UTC (for me living at +12/+13 UTC makes my head hurt because all the dates are yesterday).

The intent of f3f431a7 was to reflect the timezone that the build machine was set to. Dropping the -u would probably be sufficient but perhaps it would be better to make whole lot conditional on SOURCE_DATE_EPOCH being set. Something like this (untested, apologies gmail web interface)

ifneq ($(SOURCE_DATE_EPOCH),)
define filechk_timestamp.h

       (SOURCE_DATE="$(SOURCE_DATE_EPOCH)"; \
       LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b
%d %C%y"'; \
       LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
       LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"' )
endef
else
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"')

endef
endif

Along with SOURCE_DATE_EPOCH SOURCE_DATE_TZ can be used to recreate a build with a specific date timestamp. This allows the verification of source supplied with a pre-compiled binary.

If SOURCE_DATE_EPOCH is supplied SOURCE_DATE_TZ can be used to specify what will appear in the output of the version command. If SOURCE_DATE_TZ is not specified UTC will be used. SOURCE_DATE_TZ on it's own will not have an affect.

Signed-off-by Chris Packham <[email protected]>

---
This is a quick proof of concept that allows some control of how the timezone is displayed.

 Makefile | 7 ++++---
 README   | 9 ++++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

Makefile +4 -3

index f75c730..5102a9c 100644
@@ -1232,9 +1232,10 @@ endef
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		SOURCE_TZ="$${SOURCE_DATE_TZ:-UTC}"; \
+		TZ="$${SOURCE_TZ}" LC_ALL=C date -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+		TZ="$${SOURCE_TZ}" LC_ALL=C date -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+		TZ="$${SOURCE_TZ}" LC_ALL=C date -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
 	else \
 		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
 		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \

README +1 -3

index 1bcb63c..d2e3e94 100644
@@ -5087,11 +5087,14 @@ 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.
+This is done using the SOURCE_DATE_EPOCH and SOURCE_DATE_TZ environment

Le samedi 01 ao?t 2015 ? 22:32 +1200, Chris Packham a ?crit :

Quoted 8 lines

Along with SOURCE_DATE_EPOCH SOURCE_DATE_TZ can be used to recreate a build with a specific date timestamp. This allows the verification of source supplied with a pre-compiled binary.

If SOURCE_DATE_EPOCH is supplied SOURCE_DATE_TZ can be used to specify what will appear in the output of the version command. If SOURCE_DATE_TZ is not specified UTC will be used. SOURCE_DATE_TZ on it's own will not have an affect.

Well, I worked with the assumption that SOURCE_DATE_EPOCH would always be provided in UTC, but I see no harm in providing SOURCE_DATE_TZ as well, provided that it falls back to UTC when not set, as is the current behaviour of tour patch.

However, I am not sure that us at Reproducible Builds will actually adopt this variable. We haven't talked about it beyond my previous email [1], it was just me quickly skimming off my thoughts and firing off quick ideas.

Along with SOURCE_DATE_EPOCH SOURCE_DATE_TZ can be used to recreate a build with a specific date timestamp. This allows the verification of source supplied with a pre-compiled binary.

If SOURCE_DATE_EPOCH is supplied SOURCE_DATE_TZ can be used to specify what will appear in the output of the version command. If SOURCE_DATE_TZ is not specified UTC will be used. SOURCE_DATE_TZ on it's own will not have an affect.

Signed-off-by Chris Packham <[email protected]>

---
This is a quick proof of concept that allows some control of how the timezone is displayed.

Quoted 9 lines · Chris Packham

Along with SOURCE_DATE_EPOCH SOURCE_DATE_TZ can be used to recreate a build with a specific date timestamp. This allows the verification of source supplied with a pre-compiled binary.

If SOURCE_DATE_EPOCH is supplied SOURCE_DATE_TZ can be used to specify what will appear in the output of the version command. If SOURCE_DATE_TZ is not specified UTC will be used. SOURCE_DATE_TZ on it's own will not have an affect.

Quoted 4 lines

Signed-off-by Chris Packham <[email protected]>

---
This is a quick proof of concept that allows some control of how the timezone is displayed.

Can you please re-submit this, and the related EPOC patches as a series together? Thanks!

This commit breaks the following commit:

commit f3f431a712729a1af94d01bd1bfde17a252ff02c

Author: Chris Packham <[email protected]>
Date:   Sun May 10 21:02:09 2015 +1200

Makefile: Add U_BOOT_TZ and include in version

Define U_BOOT_TZ alongside U_BOOT_TIME and U_BOOT_DATE and use it to include the timezone in the version output.

Acked-by Simon Glass <[email protected]>

Signed-off-by Chris Packham <[email protected]>

Before this commit I have:
U-Boot 2015.07-00345-g9c57487 (Jul 31 2015 - 10:49:31 +0800)

After this commit I have:
U-Boot 2015.07-00346-gf3f431a (Jul 31 2015 - 02:50:54 +0000)

As you see: the timezone information is missing, and U-Boot's timestamp is now GMT+0 (the correct one should be GMT+8)

Is this intended behavior? Or if not, please fix it.

Quoted 7 lines · Paul Kocialkowski

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.

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

Quoted 8 lines · Tom Rini

Quoted 7 lines · Paul Kocialkowski

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.

Quoted 6 lines

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

This commit breaks build on non GNU hosts (like OS X and persumably other *BSD hosts). Before, those hosts where supported, so for me this has to be fixed for 2015.10

We need a) some mechanism to search for the GNU date variant or b) some wrapper to provide the correct output on those host machines.

I vote for a), it is acceptable to have the GNU date available but we should error on 'no GNU date available'. Furthermore we need to have the date command exchangeable by e.g. gdate, gnudate, ... maybe with full path.

Quoted 20 lines · Andreas Bie?mann

Quoted 8 lines · Tom Rini

Quoted 7 lines · Paul Kocialkowski

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.

Quoted 6 lines

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

This commit breaks build on non GNU hosts (like OS X and persumably other *BSD hosts). Before, those hosts where supported, so for me this has to be fixed for 2015.10

Quoted 6 lines

We need a) some mechanism to search for the GNU date variant or b) some wrapper to provide the correct output on those host machines.

I vote for a), it is acceptable to have the GNU date available but we should error on 'no GNU date available'. Furthermore we need to have the date command exchangeable by e.g. gdate, gnudate, ... maybe with full path.

There was a proposed patch which only uses the GNU date extensions if SOURCE_DATE_EPOCH environment variable is set, would this sufficiently address your concerns, at least for the short term?

Message-Id: <[email protected]>
http://lists.denx.de/pipermail/u-boot/2015-August/221429.html

Quoted 28 lines · Andreas Bie?mann

Quoted 26 lines · Tom Rini

Quoted 8 lines · Paul Kocialkowski

Quoted 7 lines

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.

Quoted 6 lines

Quoted 4 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

Signed-off-by Paul Kocialkowski <[email protected]>

Applied to u-boot/master, thanks!

This commit breaks build on non GNU hosts (like OS X and persumably other *BSD hosts). Before, those hosts where supported, so for me this has to be fixed for 2015.10

We need a) some mechanism to search for the GNU date variant or b) some wrapper to provide the correct output on those host machines.

I vote for a), it is acceptable to have the GNU date available but we should error on 'no GNU date available'. Furthermore we need to have the date command exchangeable by e.g. gdate, gnudate, ... maybe with full path.

Quoted 6 lines

There was a proposed patch which only uses the GNU date extensions if SOURCE_DATE_EPOCH environment variable is set, would this sufficiently address your concerns, at least for the short term?

Message-Id: <[email protected]>
http://lists.denx.de/pipermail/u-boot/2015-August/221429.html

thanks for the pointer, normal builds work with that change.

There was a proposed patch which only uses the GNU date extensions if SOURCE_DATE_EPOCH environment variable is set, would this sufficiently address your concerns, at least for the short term?

The SOURCE_DATE_EPOCH mechanism for reproducible builds requires the GNU variant of date.

Respect this and search it, error on missing GNU date.

Signed-off-by Andreas Bie?mann <[email protected]>

Quoted 2 lines · Andreas Bie?mann

The SOURCE_DATE_EPOCH mechanism for reproducible builds requires the GNU variant of date.

Why does it require the GNU date ?

Quoted 1 line

Respect this and search it, error on missing GNU date.

Wouldn't it make more sense to fix the code to NOT depend on GNU extensions ?

Hi Marek,

Quoted 5 lines · Andreas Bie?mann

Quoted 2 lines

The SOURCE_DATE_EPOCH mechanism for reproducible builds requires the GNU variant of date.

Why does it require the GNU date ?

Cause of the -d switch. It is used in GNU date variants to set the time to print the string from. On the other hand *BSD variants use it to set the DST flag.

Quoted 4 lines

Quoted 1 line

Respect this and search it, error on missing GNU date.

Wouldn't it make more sense to fix the code to NOT depend on GNU extensions ?

That would be great, but so we need to check for the tool and use the right switches depending on that.
I think forcing the user to provide the right tool here is Ok.

The SOURCE_DATE_EPOCH mechanism for reproducible builds requires the GNU variant of date. Respect this and search it, error on missing GNU date.

Signed-off-by Andreas Bie?mann <[email protected]>

---
This commit tries to figure out if we have a GNU date variant available. It errors on missing GNU date when it is required (for SOURCE_DATE_EPOCH set). The result is:

---8<---
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make SOURCE_DATE_EPOCH="date -R" O=/tmp/picosam ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
/home/abiessmann/src/u-boot/Makefile:1303: *** "No GNU date found". Stop.
make[1]: Leaving directory '/tmp/picosam'
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
CHK include/generated/timestamp_autogenerated.h
UPD include/generated/timestamp_autogenerated.h
make[1]: Leaving directory '/tmp/picosam'
--->8---

It applies on top of http://patchwork.ozlabs.org/patch/506856/ (Makefile: Use correct timezone for U_BOOT_TZ).

 Makefile | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

Makefile +0 -0

index b9b2375..95eae64 100644

Makefile +3 -3

 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -D__CHECK_ENDIAN__ $(CF)

@@ -1281,9 +1284,9 @@ endef
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		LC_ALL=C $(GNUDATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+		LC_ALL=C $(GNUDATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+		LC_ALL=C $(GNUDATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
 	else \
 		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
 		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \

@@ -1295,6 +1298,11 @@ $(version_h): include/config/uboot.release FORCE
 	$(call filechk,version.h)

Le jeudi 27 ao?t 2015 ? 10:13 +0200, Andreas Bie?mann a ?crit :

Quoted 2 lines

The SOURCE_DATE_EPOCH mechanism for reproducible builds requires the GNU variant of date. Respect this and search it, error on missing GNU date.

Well, IMHO we shouldn't check for GNU date but for the extensions it implements. Those could be included in other date implementations. For instance, it looks like busybox's date implements the -u and -d options too.

Quoted 5 lines

Signed-off-by Andreas Bie?mann <[email protected]>

---
This commit tries to figure out if we have a GNU date variant available. It errors on missing GNU date when it is required (for SOURCE_DATE_EPOCH set). The result is:

Also, I don't think it should be up to the Makefile to figure out which date binary to use. It should be up to the user to put the right one as "date", e.g. with an alias. That is, unless the name for GNU date is something really standardized on non-GNU systems.

Quoted 7 lines

Makefile +0 -0

index b9b2375..95eae64 100644
@@ -346,6 +346,9 @@ PERL		= perl
 PYTHON		= python
 DTC		= dtc

Makefile PERL = perl · line 351

Quoted 4 lines

Makefile +3 -0

 CHECK		= sparse
+GNUDATE	       := $(foreach date,gdate date.gnu date, \
+		    $(shell _date=`which $(date)`; \
+		      $${_date} --version 2> /dev/null | $(AWK) "/GNU coreutils/ { print \"$${_date}\"; }"))

I advise running date with the needed options (-u -d) and checked the error code instead of this. And of course, the variable names shouldn't mention GNU date.

The SOURCE_DATE_EPOCH mechanism for reproducible builds require some date with -u and -d switch to print the date string of another time. In other words it requires some date that behaves like the GNU date.

Respect this and search a working date, error on no working version.

Signed-off-by Andreas Bie?mann <[email protected]>

---
This commit tries to figure out if we have a date variant available that supports the '-u' and '-d "@0"' switches. It errors on non-working variants of date.

To respect *BSD host systems search for gdate and date.gnu. Those pre- and suffixes are widespread used for the GNU variant of a tool also avialable on *BSD systems.

The result is:

---8<---
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
CHK include/generated/timestamp_autogenerated.h
UPD include/generated/timestamp_autogenerated.h
make[1]: Leaving directory '/tmp/picosam'
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam SOURCE_DATE_EPOCH="0" ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
/home/abiessmann/src/u-boot/Makefile:1304: *** "Your gdate/date.gnu/date does not support the '-u' and '-d' switches like GNU date does!". Stop. make[1]: Leaving directory '/tmp/picosam'
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2
--->8---

It applies on top of http://patchwork.ozlabs.org/patch/506856/ (Makefile: Use correct timezone for U_BOOT_TZ).

Changes in v2:
* check for '-u' and '-d "@0"' switch rather than for the GNU variant

 Makefile | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Makefile +0 -0

index b9b2375..b797e38 100644

Makefile +3 -3

 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -D__CHECK_ENDIAN__ $(CF)

@@ -1281,9 +1285,9 @@ endef
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
 	else \
 		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
 		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \

@@ -1295,6 +1299,11 @@ $(version_h): include/config/uboot.release FORCE
 	$(call filechk,version.h)

Le jeudi 27 ao?t 2015 ? 11:30 +0200, Andreas Bie?mann a ?crit :

Quoted 6 lines

Changes in v2:
* check for '-u' and '-d "@0"' switch rather than for the GNU variant

 Makefile | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Makefile PERL = perl · line 352

Quoted 12 lines

Makefile +4 -0

index b9b2375..b797e38 100644
@@ -346,6 +346,10 @@ PERL		= perl
 PYTHON		= python
 DTC		= dtc
 CHECK		= sparse
+DATE	       := $(foreach date,gdate date.gnu date, \
+		    $(shell _date=`which $(date)`; \
+		      $${_date} -u -d "@0" >/dev/null 2>&1; \
+		      test $$? -eq 0 && echo $${_date}))

First, I don't understand why you need to call date with the full path:
if which can find it, then calling the binary without its full path should do just as well, right?

Then, correct me if I'm wrong, but calling test and using && is overkill, you could simply do: $${_date} -u -d "@0" >/dev/null 2>&1 && echo $${_date}

So in the end, the whole line would look like:

DATE	       := $(foreach date,gdate date.gnu date, \
		    $($${date} -u -d "@0" >/dev/null 2>&1 \
		      && echo $${date}))

Let me know what you think (and please test it as well).

Quoted 27 lines

Makefile +8 -3

 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -D__CHECK_ENDIAN__ $(CF)

@@ -1281,9 +1285,9 @@ endef
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
 	else \
 		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
 		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \

@@ -1295,6 +1299,11 @@ $(version_h): include/config/uboot.release FORCE
 	$(call filechk,version.h)
 
 $(timestamp_h): $(srctree)/Makefile FORCE
+ifneq ($(strip $(SOURCE_DATE_EPOCH)),)
+ifeq ($(strip $(DATE)),)
+	$(error "Your gdate/date.gnu/date does not support the '-u' and '-d' switches like GNU date does!")
+endif
+endif
 	$(call filechk,timestamp.h)
 
 # ---------------------------------------------------------------------------

Quoted 9 lines

Le jeudi 27 ao?t 2015 ? 11:30 +0200, Andreas Bie?mann a ?crit :

Quoted 6 lines

Changes in v2:
* check for '-u' and '-d "@0"' switch rather than for the GNU variant

 Makefile | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Quoted 16 lines

Makefile PERL = perl · line 352

Quoted 12 lines

Makefile +4 -0

index b9b2375..b797e38 100644
@@ -346,6 +346,10 @@ PERL		= perl
 PYTHON		= python
 DTC		= dtc
 CHECK		= sparse
+DATE	       := $(foreach date,gdate date.gnu date, \
+		    $(shell _date=`which $(date)`; \
+		      $${_date} -u -d "@0" >/dev/null 2>&1; \
+		      test $$? -eq 0 && echo $${_date}))

First, I don't understand why you need to call date with the full path:
if which can find it, then calling the binary without its full path should do just as well, right?

You'r right.

Quoted 3 lines

Then, correct me if I'm wrong, but calling test and using && is overkill, you could simply do: $${_date} -u -d "@0" >/dev/null 2>&1 && echo $${_date}

Also true.

Quoted 6 lines

So in the end, the whole line would look like:

DATE	       := $(foreach date,gdate date.gnu date, \
		    $($${date} -u -d "@0" >/dev/null 2>&1 \
		      && echo $${date}))

Quoted 1 line

Let me know what you think (and please test it as well).

That should work. I wonder however why we don't include this snippet in the filechk_timestamp.h script directly. In fact the $(DATE) (a date that support -d '@0' switch) is just used there, so why clobber the Makefile with it?

---8<---
define filechk_timestamp.h

 (if test -n "$${SOURCE_DATE_EPOCH}"; then \
   date=""; \
   for _date in gdate date.gnu date; do \
   $${_date} -u -d "$${SOURCE_DATE}" >/dev/null 2>&1 && \
      date="$${_date}"; \
   done; \
   if test -n "$${date}"; then \
    SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
    LC_ALL=C $${date} -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b
%d %C%y"'; \
    LC_ALL=C $${date} -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
    LC_ALL=C $${date} -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
   else \
    return 42; \
   fi; \
  else \
   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"'; \

fi)
endef
--->8---

Quoted 28 lines

Quoted 27 lines

Makefile +8 -3

 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -D__CHECK_ENDIAN__ $(CF)

@@ -1281,9 +1285,9 @@ endef
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
+		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
 	else \
 		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
 		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \

@@ -1295,6 +1299,11 @@ $(version_h): include/config/uboot.release FORCE
 	$(call filechk,version.h)
 
 $(timestamp_h): $(srctree)/Makefile FORCE
+ifneq ($(strip $(SOURCE_DATE_EPOCH)),)
+ifeq ($(strip $(DATE)),)
+	$(error "Your gdate/date.gnu/date does not support the '-u' and '-d' switches like GNU date does!")
+endif
+endif
 	$(call filechk,timestamp.h)
 
 # ---------------------------------------------------------------------------

The SOURCE_DATE_EPOCH mechanism for reproducible builds require some date(1) with -d switch to print the relevant date and time strings of another point of time.

In other words it requires some date(1) that behaves like the GNU date(1) [1]. The BSD date(1) [2] on the other hand has the same switch but with a different meaning.

Respect this and check the date(1) abilities before usage, error on non working version. Use the well known pre- and suffixes for the GNU variant of a tool on *BSD hosts to search for a working date(1) version.

[1] http://man7.org/linux/man-pages/man1/date.1.html [2]
http://www.freebsd.org/cgi/man.cgi?query=date

Signed-off-by Andreas Bie?mann <[email protected]>

Applied to u-boot/master, thanks!

The SOURCE_DATE_EPOCH mechanism for reproducible builds require some date(1) with -d switch to print the relevant date and time strings of another point of time.

In other words it requires some date(1) that behaves like the GNU date(1) [1]. The BSD date(1) [2] on the other hand has the same switch but with a different meaning.

Respect this and check the date(1) abilities before usage, error on non working version. Use the well known pre- and suffixes for the GNU variant of a tool on *BSD hosts to search for a working date(1) version.

[1] http://man7.org/linux/man-pages/man1/date.1.html [2]
http://www.freebsd.org/cgi/man.cgi?query=date

Signed-off-by Andreas Bie?mann <[email protected]>

---
This commit tries to figure out if we have a date variant available that supports the '-u' and '-d "@0"' switches. It errors on non-working variants of date.

To respect *BSD host systems search for gdate and date.gnu. Those pre- and suffixes are widespread used for the GNU variant of a tool also avialable on *BSD systems.

The result is:

---8<---
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
CHK include/generated/timestamp_autogenerated.h
UPD include/generated/timestamp_autogenerated.h
make[1]: Leaving directory '/tmp/picosam'
abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam SOURCE_DATE_EPOCH="$(date +'%s')" ARCH=arm include/generated/timestamp_autogenerated.h make[1]: Entering directory '/tmp/picosam'
CHK include/generated/timestamp_autogenerated.h
/home/abiessmann/src/u-boot/Makefile:1311: recipe for target 'include/generated/timestamp_autogenerated.h' failed
make[1]: *** [include/generated/timestamp_autogenerated.h] Error 42
make[1]: Leaving directory '/tmp/picosam'
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2
--->8---

It applies on top of http://patchwork.ozlabs.org/patch/506856/ (Makefile: Use correct timezone for U_BOOT_TZ).

Changes in v3:
* move the check in the timestamp.h generation script
* remove RFC
* reword commit message

Changes in v2:
* check for '-u' and '-d "@0"' switch rather than for the GNU variant

 Makefile | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Makefile +8 -3

index e8ea71c..81f12b8 100644
@@ -1279,12 +1279,24 @@ define filechk_version.h
 	echo \#define LD_VERSION_STRING \"$$($(LD) --version | head -n 1)\"; )
 endef
 
+# The SOURCE_DATE_EPOCH mechanism requires a date that behaves like GNU date.
+# The BSD date on the other hand behaves different and would produce errors
+# with the misused '-d' switch.  Respect that and search a working date with
+# well known pre- and suffixes for the GNU variant of date.
 define filechk_timestamp.h
 	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
 		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
-		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
+		DATE=""; \
+		for date in gdate date.gnu date; do \
+			$${date} -u -d "$${SOURCE_DATE}" >/dev/null 2>&1 && DATE="$${date}"; \
+		done; \

Le vendredi 28 ao?t 2015 ? 10:29 +0200, Andreas Bie?mann a ?crit :

Quoted 8 lines

The SOURCE_DATE_EPOCH mechanism for reproducible builds require some date(1) with -d switch to print the relevant date and time strings of another point of time.

In other words it requires some date(1) that behaves like the GNU date(1) [1]. The BSD date(1) [2] on the other hand has the same switch but with a different meaning.

Quoted 3 lines

Respect this and check the date(1) abilities before usage, error on non working version. Use the well known pre- and suffixes for the GNU variant of a tool on *BSD hosts to search for a working date(1) version.

Looks good to me! Have you actually tried setting SOURCE_DATE_EPOCH to a fixed value, building U-Boot twice and checking that the produced file is the very same?

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.

However, some other devices might need some more tweaks, especially regarding the image generation tools.

tools/default_image.c +17 -1

index cf5c0d4..18940af 100644
@@ -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);

Signature · 1 line

1.9.1

Quoted 3 lines

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.

...

Quoted 2 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

With this patch, there is still variation based on timezone in any of the u-boot.img and u-boot-sunxi-with-spl.bin produced in the Debian packages:

https://reproducible.debian.net/rb-pkg/unstable/armhf/u-boot.html

The good news is that all the u-boot.bin targets are produced reproducibly, so here's to progress!

I think the use of "time = mktime(time_universal);" is where the problem lies:

According to the mktime manpage:

The mktime() function converts a broken-down time structure, expressed as local time, to calendar time representation.

So my interpetation is that it's taking the UTC time and converts it into local time using the configured timezone... not sure what would be a viable alternative to mktime.

Running with the TZ=UTC environment variable exported works around the problem; not sure if it would be appropriate to always run with TZ=UTC when SOURCE_DATE_EPOCH is set...

Le jeudi 24 septembre 2015 ? 09:05 -0700, Vagrant Cascadian a ?crit :

Quoted 2 lines

I think the use of "time = mktime(time_universal);" is where the problem lies:

[?]

Quoted 8 lines

According to the mktime manpage:

The mktime() function converts a broken-down time structure, expressed as local time, to calendar time representation.

So my interpetation is that it's taking the UTC time and converts it into local time using the configured timezone... not sure what would be a viable alternative to mktime.

That seems to make sense. Come to think of it, it probably was not necessary to call gmtime in the first place: if SOURCE_DATE_EPOCH is always in UTC, we should be able to stick that as-is in the time variable. At best, gmtime + mktime (assuming mktime working in UTC) would give us back the same timestamp.

What do you think? Please let me know if I'm wrong.

Quoted 1 line

What do you think? Please let me know if I'm wrong.

This patch on top of 2015.10-rc4 seems to resolve the issue for me:

Index: u-boot/tools/default_image.c
===================================================================

tools/default_image.c +0 -2

@@ -108,8 +108,6 @@ static void image_set_header(void *ptr,
 			fprintf(stderr, "%s: SOURCE_DATE_EPOCH is not valid\n",
 				__func__);
 			time = 0;
-		} else {
-			time = mktime(time_universal);
 		}
 	} else {
 		time = sbuf->st_mtime;

It still checks for the validity of SOURCE_DATE_EPOCH using gmtime, but doesn't call mktime at all, just re-uses the value set from SOURCE_DATE_EPOCH.

Quoted 3 lines · Paul Kocialkowski

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.

...

Quoted 2 lines

However, some other devices might need some more tweaks, especially regarding the image generation tools.

With this patch, there is still variation based on timezone in any of the u-boot.img and u-boot-sunxi-with-spl.bin produced in the Debian packages:

https://reproducible.debian.net/rb-pkg/unstable/armhf/u-boot.html

The good news is that all the u-boot.bin targets are produced reproducibly, so here's to progress!