Introduce a new selftest, luo_multi_file, to validate two key aspects of
the Live Update Orchestrator file preservation mechanism: the ability to
handle multiple files within a single session, and the correct cleanup
of unreclaimed files.

The test implements a full kexec cycle with the following flow:
1. Pre-kexec:
  - A single session is created.
  - Three distinct memfd files (A, B, and C) are created, populated with
    unique data, and preserved within this session.
  - The global LIVEUPDATE_PREPARE event is triggered, and the system
    reboots via kexec.
2. Post-kexec:
  - The preserved session is retrieved.
  - Files A and C are restored and their contents are verified to ensure
    that multiple files can be successfully restored from a single
    session.
  - File B is intentionally not restored.
  - The global LIVEUPDATE_FINISH event is triggered.
3. Verification:
  - The test is considered successful if files A and C are verified
    correctly.
  - The user is prompted to check the kernel log (dmesg) for a message
    confirming that the unreclaimed file (B) was identified and cleaned
    up by the LUO core, thus validating the cleanup path.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 tools/testing/selftests/liveupdate/Makefile   |   1 +
 .../selftests/liveupdate/luo_multi_file.c     | 119 ++++++++++++++++++
 2 files changed, 120 insertions(+)
 create mode 100644 tools/testing/selftests/liveupdate/luo_multi_file.c

diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
index 1cbc816ed5c5..f43b7d03e017 100644
--- a/tools/testing/selftests/liveupdate/Makefile
+++ b/tools/testing/selftests/liveupdate/Makefile
@@ -9,6 +9,7 @@ LDFLAGS += -static
 LUO_SHARED_SRCS := luo_test_utils.c
 LUO_SHARED_HDRS += luo_test_utils.h
 
+LUO_MANUAL_TESTS += luo_multi_file
 LUO_MANUAL_TESTS += luo_multi_kexec
 
 TEST_FILES += do_kexec.sh
diff --git a/tools/testing/selftests/liveupdate/luo_multi_file.c b/tools/testing/selftests/liveupdate/luo_multi_file.c
new file mode 100644
index 000000000000..ae38fe8aba4c
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/luo_multi_file.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#include "luo_test_utils.h"
+
+#define KEXEC_SCRIPT "./do_kexec.sh"
+
+#define SESSION_NAME "multi_file_session"
+#define TOKEN_A 101
+#define TOKEN_B 102
+#define TOKEN_C 103
+
+#define DATA_A "Alpha file data"
+#define DATA_B "Bravo file data which will be unreclaimed"
+#define DATA_C "Charlie file data"
+
+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 3 memfds (A, B, C)...\n");
+	if (create_and_preserve_memfd(session_fd, TOKEN_A, DATA_A) < 0)
+		fail_exit("Failed to preserve memfd A");
+	if (create_and_preserve_memfd(session_fd, TOKEN_B, DATA_B) < 0)
+		fail_exit("Failed to preserve memfd B");
+	if (create_and_preserve_memfd(session_fd, TOKEN_C, DATA_C) < 0)
+		fail_exit("Failed to preserve memfd C");
+	ksft_print_msg("[PRE-KEXEC] All memfds preserved.\n");
+
+	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); /* Should not be reached */
+	exit(EXIT_FAILURE);
+}
+
+static void run_post_kexec(int luo_fd)
+{
+	int session_fd, mfd_a, mfd_c;
+
+	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);
+
+	/* 1. VERIFY SUCCESS: Restore and verify memfd A. */
+	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("  Success.\n");
+
+	/* 2. VERIFY SUCCESS: Restore and verify memfd C. */
+	ksft_print_msg("[POST-KEXEC] Restoring and verifying memfd C (token %d)...\n",
+		       TOKEN_C);
+	mfd_c = restore_and_verify_memfd(session_fd, TOKEN_C, DATA_C);
+	if (mfd_c < 0)
+		fail_exit("Failed to restore or verify memfd C");
+	close(mfd_c);
+	ksft_print_msg("  Success.\n");
+
+	ksft_print_msg("[POST-KEXEC] NOT restoring memfd B (token %d) to test cleanup.\n",
+		       TOKEN_B);
+
+	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