[PATCH v4 29/30] selftests/liveupdate: Add test for unreclaimed resource cleanup

[Pasha Tatashin <pasha.tatashin@soleen.com>]

Introduce a new selftest, luo_unreclaimed, to specifically validate that
the LUO framework correctly identifies and cleans up preserved
resources that are not restored by userspace after a kexec reboot.

Ensuring proper cleanup of unreclaimed (or "abandoned") resources is
critical for preventing resource leaks in the kernel. This test provides
a focused scenario to verify this cleanup path, which is a key aspect of
the LUO's robustness.

The test performs a full kexec cycle with the following simple flow:

1. Pre-kexec:
  - A single session is created.
  - Two memfd files are preserved: File A (which will be restored) and
    File B (which will be abandoned).
  - The global LIVEUPDATE_PREPARE event is triggered, and the system
    reboots.
2. Post-kexec:
  - The preserved session is retrieved.
  - Only File A is restored and its contents are verified to confirm the
    basic preservation mechanism is working.
  - File B is intentionally not restored.
  - The global LIVEUPDATE_FINISH event is triggered.
3. Verification:
  - The test passes if File A is verified successfully.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 tools/testing/selftests/liveupdate/Makefile   |   1 +
 .../selftests/liveupdate/luo_unreclaimed.c    | 107 ++++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 tools/testing/selftests/liveupdate/luo_unreclaimed.c

diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
index 72892942dd61..ffce73233149 100644
--- a/tools/testing/selftests/liveupdate/Makefile
+++ b/tools/testing/selftests/liveupdate/Makefile
@@ -12,6 +12,7 @@ LUO_SHARED_HDRS += luo_test_utils.h
 LUO_MANUAL_TESTS += luo_multi_file
 LUO_MANUAL_TESTS += luo_multi_kexec
 LUO_MANUAL_TESTS += luo_multi_session
+LUO_MANUAL_TESTS += luo_unreclaimed
 
 TEST_FILES += do_kexec.sh
 
diff --git a/tools/testing/selftests/liveupdate/luo_unreclaimed.c b/tools/testing/selftests/liveupdate/luo_unreclaimed.c
new file mode 100644
index 000000000000..c3921b21b97b
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/luo_unreclaimed.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#include "luo_test_utils.h"
+#include "../kselftest.h"
+
+#define KEXEC_SCRIPT "./do_kexec.sh"
+
+#define SESSION_NAME "unreclaimed_session"
+#define TOKEN_A 100
+#define TOKEN_B 200
+#define DATA_A "This is file A, the one we retrieve."
+#define DATA_B "This is file B, the one we abandon."
+
+static void run_pre_kexec(int luo_fd)
+{
+	int session_fd;
+
+	ksft_print_msg("[PRE-KEXEC] Starting workload...\n");
+
+	session_fd = luo_create_session(luo_fd, SESSION_NAME);
+	if (session_fd < 0)
+		fail_exit("Failed to create session '%s'", SESSION_NAME);
+
+	ksft_print_msg("[PRE-KEXEC] Preserving memfd A (to be restored).\n");
+	if (create_and_preserve_memfd(session_fd, TOKEN_A, DATA_A) < 0)
+		fail_exit("Failed to preserve memfd A");
+
+	ksft_print_msg("[PRE-KEXEC] Preserving memfd B (to be abandoned).\n");
+	if (create_and_preserve_memfd(session_fd, TOKEN_B, DATA_B) < 0)
+		fail_exit("Failed to preserve memfd B");
+
+	if (luo_set_global_event(luo_fd, LIVEUPDATE_PREPARE) < 0)
+		fail_exit("Failed to set global PREPARE event");
+
+	ksft_print_msg("[PRE-KEXEC] System is ready. Executing kexec...\n");
+	if (system(KEXEC_SCRIPT) != 0)
+		fail_exit("kexec script failed");
+
+	sleep(10);
+	exit(EXIT_FAILURE);
+}
+
+static void run_post_kexec(int luo_fd)
+{
+	int session_fd, mfd_a;
+
+	ksft_print_msg("[POST-KEXEC] Starting workload...\n");
+
+	session_fd = luo_retrieve_session(luo_fd, SESSION_NAME);
+	if (session_fd < 0)
+		fail_exit("Failed to retrieve session '%s'", SESSION_NAME);
+
+	ksft_print_msg("[POST-KEXEC] Restoring and verifying memfd A (token %d)...\n",
+		       TOKEN_A);
+	mfd_a = restore_and_verify_memfd(session_fd, TOKEN_A, DATA_A);
+	if (mfd_a < 0)
+		fail_exit("Failed to restore or verify memfd A");
+	close(mfd_a);
+	ksft_print_msg("  Data verification PASSED for memfd A.\n");
+
+	ksft_print_msg("[POST-KEXEC] NOT restoring memfd B (token %d) to test cleanup.\n",
+		       TOKEN_B);
+
+	ksft_print_msg("[POST-KEXEC] Driving global state to FINISH...\n");
+	if (luo_set_global_event(luo_fd, LIVEUPDATE_FINISH) < 0)
+		fail_exit("Failed to set global FINISH event");
+
+	close(session_fd);
+
+	ksft_print_msg("\n--- TEST PASSED ---\n");
+	ksft_print_msg("Check dmesg for cleanup log of token %d in session '%s'.\n",
+		       TOKEN_B, SESSION_NAME);
+}
+
+int main(int argc, char *argv[])
+{
+	enum liveupdate_state state;
+	int luo_fd;
+
+	luo_fd = luo_open_device();
+	if (luo_fd < 0) {
+		ksft_exit_skip("Failed to open %s. Is the luo module loaded?\n",
+			       LUO_DEVICE);
+	}
+
+	if (luo_get_global_state(luo_fd, &state) < 0)
+		fail_exit("Failed to get LUO state");
+
+	switch (state) {
+	case LIVEUPDATE_STATE_NORMAL:
+		run_pre_kexec(luo_fd);
+		break;
+	case LIVEUPDATE_STATE_UPDATED:
+		run_post_kexec(luo_fd);
+		break;
+	default:
+		fail_exit("Test started in an unexpected state: %d", state);
+	}
+
+	close(luo_fd);
+	ksft_exit_pass();
+}
-- 
2.51.0.536.g15c5d4f767-goog