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-rw-r--r--meta/lib/oe/reproducible.py51
1 files changed, 51 insertions, 0 deletions
diff --git a/meta/lib/oe/reproducible.py b/meta/lib/oe/reproducible.py
index a5000574cf..4fb99d963c 100644
--- a/meta/lib/oe/reproducible.py
+++ b/meta/lib/oe/reproducible.py
@@ -5,6 +5,57 @@ import os
5import subprocess 5import subprocess
6import bb 6import bb
7 7
8# For reproducible builds, this code sets the default SOURCE_DATE_EPOCH in each
9# component's build environment. The format is number of seconds since the
10# system epoch.
11#
12# Upstream components (generally) respect this environment variable,
13# using it in place of the "current" date and time.
14# See https://reproducible-builds.org/specs/source-date-epoch/
15#
16# The default value of SOURCE_DATE_EPOCH comes from the function
17# get_source_date_epoch_value which reads from the SDE_FILE, or if the file
18# is not available will use the fallback of SOURCE_DATE_EPOCH_FALLBACK.
19#
20# The SDE_FILE is normally constructed from the function
21# create_source_date_epoch_stamp which is typically added as a postfuncs to
22# the do_unpack task. If a recipe does NOT have do_unpack, it should be added
23# to a task that runs after the source is available and before the
24# do_deploy_source_date_epoch task is executed.
25#
26# If a recipe wishes to override the default behavior it should set it's own
27# SOURCE_DATE_EPOCH or override the do_deploy_source_date_epoch_stamp task
28# with recipe-specific functionality to write the appropriate
29# SOURCE_DATE_EPOCH into the SDE_FILE.
30#
31# SOURCE_DATE_EPOCH is intended to be a reproducible value. This value should
32# be reproducible for anyone who builds the same revision from the same
33# sources.
34#
35# There are 4 ways the create_source_date_epoch_stamp function determines what
36# becomes SOURCE_DATE_EPOCH:
37#
38# 1. Use the value from __source_date_epoch.txt file if this file exists.
39# This file was most likely created in the previous build by one of the
40# following methods 2,3,4.
41# Alternatively, it can be provided by a recipe via SRC_URI.
42#
43# If the file does not exist:
44#
45# 2. If there is a git checkout, use the last git commit timestamp.
46# Git does not preserve file timestamps on checkout.
47#
48# 3. Use the mtime of "known" files such as NEWS, CHANGLELOG, ...
49# This works for well-kept repositories distributed via tarball.
50#
51# 4. Use the modification time of the youngest file in the source tree, if
52# there is one.
53# This will be the newest file from the distribution tarball, if any.
54#
55# 5. Fall back to a fixed timestamp (SOURCE_DATE_EPOCH_FALLBACK).
56#
57# Once the value is determined, it is stored in the recipe's SDE_FILE.
58
8def get_source_date_epoch_from_known_files(d, sourcedir): 59def get_source_date_epoch_from_known_files(d, sourcedir):
9 source_date_epoch = None 60 source_date_epoch = None
10 newest_file = None 61 newest_file = None