kunit: respect KBUILD_OUTPUT env variable by default

Currently, kunit.py ignores the KBUILD_OUTPUT env variable and always
defaults to .kunit in the working directory. This behavior is inconsistent
with standard Kbuild behavior, where KBUILD_OUTPUT defines the build
artifact location.

This patch modifies kunit.py to respect KBUILD_OUTPUT if set.  A .kunit
subdirectory is created inside KBUILD_OUTPUT to avoid polluting the build
directory.

Link: https://lore.kernel.org/r/20260106-kunit-kbuild_output-v2-1-582281797343@gmail.com
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Ryota Sakamoto <sakamo.ryota@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

2 files changed, 25 insertions, 1 deletions

diff --git a/tools/testing/kunit/kunit.py b/tools/testing/kunit/kunit.py
index cd99c1956331..e3d82a038f93 100755
--- a/tools/testing/kunit/kunit.py
+++ b/tools/testing/kunit/kunit.py
@@ -323,11 +323,16 @@ def get_default_jobs() -> int:
 		return ncpu
 	raise RuntimeError("os.cpu_count() returned None")
 
+def get_default_build_dir() -> str:
+	if 'KBUILD_OUTPUT' in os.environ:
+		return os.path.join(os.environ['KBUILD_OUTPUT'], '.kunit')
+	return '.kunit'
+
 def add_common_opts(parser: argparse.ArgumentParser) -> None:
 	parser.add_argument('--build_dir',
 			    help='As in the make command, it specifies the build '
 			    'directory.',
-			    type=str, default='.kunit', metavar='DIR')
+			    type=str, default=get_default_build_dir(), metavar='DIR')
 	parser.add_argument('--make_options',
 			    help='X=Y make option, can be repeated.',
 			    action='append', metavar='X=Y')
diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
index bbba921e0eac..a55b5085310d 100755
--- a/tools/testing/kunit/kunit_tool_test.py
+++ b/tools/testing/kunit/kunit_tool_test.py
@@ -601,6 +601,7 @@ class KUnitMainTest(unittest.TestCase):
 			all_passed_log = file.readlines()
 
 		self.print_mock = mock.patch('kunit_printer.Printer.print').start()
+		mock.patch.dict(os.environ, clear=True).start()
 		self.addCleanup(mock.patch.stopall)
 
 		self.mock_linux_init = mock.patch.object(kunit_kernel, 'LinuxSourceTree').start()
@@ -723,6 +724,24 @@ class KUnitMainTest(unittest.TestCase):
 			args=None, build_dir=build_dir, filter_glob='', filter='', filter_action=None, timeout=300)
 		self.print_mock.assert_any_call(StrContains('Testing complete.'))
 
+	@mock.patch.dict(os.environ, {'KBUILD_OUTPUT': '/tmp'})
+	def test_run_builddir_from_env(self):
+		build_dir = '/tmp/.kunit'
+		kunit.main(['run'])
+		self.assertEqual(self.linux_source_mock.build_reconfig.call_count, 1)
+		self.linux_source_mock.run_kernel.assert_called_once_with(
+			args=None, build_dir=build_dir, filter_glob='', filter='', filter_action=None, timeout=300)
+		self.print_mock.assert_any_call(StrContains('Testing complete.'))
+
+	@mock.patch.dict(os.environ, {'KBUILD_OUTPUT': '/tmp'})
+	def test_run_builddir_override(self):
+		build_dir = '.kunit'
+		kunit.main(['run', '--build_dir=.kunit'])
+		self.assertEqual(self.linux_source_mock.build_reconfig.call_count, 1)
+		self.linux_source_mock.run_kernel.assert_called_once_with(
+			args=None, build_dir=build_dir, filter_glob='', filter='', filter_action=None, timeout=300)
+		self.print_mock.assert_any_call(StrContains('Testing complete.'))
+
 	def test_config_builddir(self):
 		build_dir = '.kunit'
 		kunit.main(['config', '--build_dir', build_dir])