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authorPaul Kocialkowski <contact@paulk.fr>2015-07-26 18:48:15 +0200
committerTom Rini <trini@konsulko.com>2015-07-27 15:03:14 -0400
commitf3f431a712729a1af94d01bd1bfde17a252ff02c (patch)
tree8ce4a040eac05ef88909a5407cacc8b70add84ae /README
parent9c5748775228f6648a99d1e28acef92012fa031e (diff)
downloadtalos-obmc-uboot-f3f431a712729a1af94d01bd1bfde17a252ff02c.zip
talos-obmc-uboot-f3f431a712729a1af94d01bd1bfde17a252ff02c.tar.gz
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@paulk.fr>
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diff --git a/README b/README
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@@ -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:
======================
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