do_package/sstate/sstatesig: Change timestamp clamping to hash output only

The code was changing the timestamps of the files in the do_package output,
particularly the files added for debug sources. This was to do two things:

a) make do_package sstate more reproducible
b) ensure better hash equivalence matching

Unfortuately the debug source files are hardlinks into the source tree for
efficiency so touching these, touches a lot of files in ${B} and ${S}. This
causes unpredictable effects if compile is run again for example, or could
cause compiling in the install task.

The hash equivalence matching is of key importance but we can mimic that
using clamping of the file timestamps in the depsig output used to generate
the hashes.

This patch drops the global timestamp clamping, instead allowing the files
to retain their creation timestamps into sstate. This makes do_package sstate
slightly less reproducibile. We could clamp the sstate timestamps but that
would lead to two different sets of timestamps depending on whether the
data came from sstate or not. I'd prefer to have consistent code behaviour,
rather than differing behavhour depending on whether data came from sstate
or not.

If we wanted to have reproducibiliy and fix the "corruption" of S/B and have
consistent codepaths, the only other option would be two copies of the
sources, which could end up huge and seems the least desireable option.

This patch therefore drops the timestamp clamping in the sstate files
and tweaks the depsig data generation to clamp the timestamps for do_package
instead since this seems the best compromise.

I validated that rpm/deb/ipk files still generate correctly as before.

(From OE-Core rev: 9df0bf5775ec96773e77c489ba6a443037d65ab6)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 475759fdab7200488b2a568b2ba1aa31a456d113)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/meta/lib/oe/sstatesig.py b/meta/lib/oe/sstatesig.py
index a46e5502ab..d818fce8f1 100644
--- a/meta/lib/oe/sstatesig.py
+++ b/meta/lib/oe/sstatesig.py
@@ -524,6 +524,7 @@ def OEOuthashBasic(path, sigfile, task, d):
     if task == "package":
         include_timestamps = True
         include_root = False
+        source_date_epoch = float(d.getVar("SOURCE_DATE_EPOCH"))
     hash_version = d.getVar('HASHEQUIV_HASH_VERSION')
     extra_sigdata = d.getVar("HASHEQUIV_EXTRA_SIGDATA")
 
@@ -615,7 +616,11 @@ def OEOuthashBasic(path, sigfile, task, d):
                         raise Exception(msg).with_traceback(e.__traceback__)
 
                 if include_timestamps:
-                    update_hash(" %10d" % s.st_mtime)
+                    # Need to clamp to SOURCE_DATE_EPOCH
+                    if s.st_mtime > source_date_epoch:
+                        update_hash(" %10d" % source_date_epoch)
+                    else:
+                        update_hash(" %10d" % s.st_mtime)
 
                 update_hash(" ")
                 if stat.S_ISBLK(s.st_mode) or stat.S_ISCHR(s.st_mode):