[PATCH] erofs-utils: tests: add test for negative GNU tar mtimes

Add a regression test for negative GNU tar mtimes.

It creates a tarball with a file whose mtime is -1, checks that the
mtime field is encoded in GNU base-256 format, and verifies that the
timestamp is preserved after building and extracting the image.

Signed-off-by: Vansh Choudhary <[email protected]>
---
 tests/Makefile.am   |  3 +++
 tests/erofs/030     | 57 +++++++++++++++++++++++++++++++++++++++++++++
 tests/erofs/030.out |  2 ++
 3 files changed, 62 insertions(+)
 create mode 100755 tests/erofs/030
 create mode 100644 tests/erofs/030.out

diff --git a/tests/Makefile.am b/tests/Makefile.am
index d8ac067..28edc0d 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -126,6 +126,9 @@ TESTS += erofs/028
 # 029 - test FUSE daemon and kernel error handling on corrupted inodes
 TESTS += erofs/029
 
+# 030 - regression test for negative GNU tar mtimes
+TESTS += erofs/030
+
 # NEW TEST CASE HERE
 # TESTS += erofs/999
 
diff --git a/tests/erofs/030 b/tests/erofs/030
new file mode 100755
index 0000000..6d57225
--- /dev/null
+++ b/tests/erofs/030
@@ -0,0 +1,57 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+#
+# 030 - regression test for negative GNU tar mtimes
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$(echo $0 | awk '{print $((NF-1))"/"$NF}' FS="/")
+
+# get standard environment, filters and checks
+. "${srcdir}/common/rc"
+
+cleanup()
+{
+	cd /
+	rm -rf $tmp.*
+}
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+echo "QA output created by $seq"
+
+if [ -z "$SCRATCH_DEV" ]; then
+	SCRATCH_DEV=$tmp/erofs_$seq.img
+	rm -f $SCRATCH_DEV
+fi
+
+localdir="$tmp/$seq"
+rm -rf $localdir
+mkdir -p $localdir/src
+
+: > $localdir/src/foo
+touch -d @-1 $localdir/src/foo >> $seqres.full 2>&1 || \
+	_notrun "touch -d @-1 is not supported"
+tar --format=gnu -C $localdir/src -cf $localdir/foo.tar foo >> $seqres.full 2>&1 || \
+	_fail "failed to create tarball"
+
+mtime=$(od -An -t x1 -j 136 -N 12 $localdir/foo.tar | tr -d '[:space:]')
+[ "$mtime" = "ffffffffffffffffffffffff" ] || \
+	_notrun "tar did not encode a negative GNU mtime"
+
+rm -f $SCRATCH_DEV
+$MKFS_EROFS_PROG --tar=f $SCRATCH_DEV $localdir/foo.tar \
+	>> $seqres.full 2>&1 || _fail "failed to mkfs tarball"
+
+rm -rf $localdir/out
+mkdir -p $localdir/out
+$FSCK_EROFS_PROG --extract=$localdir/out $SCRATCH_DEV >> $seqres.full 2>&1 || \
+	_fail "failed to extract image"
+
+mtime=$(stat -c '%Y' $localdir/out/foo)
+[ "$mtime" = "-1" ] || _fail "negative GNU mtime was not preserved"
+
+echo Silence is golden
+status=0
+exit 0
diff --git a/tests/erofs/030.out b/tests/erofs/030.out
new file mode 100644
index 0000000..06a1c8f
--- /dev/null
+++ b/tests/erofs/030.out
@@ -0,0 +1,2 @@
+QA output created by 030
+Silence is golden
-- 
2.43.0