[PATCH v6 20/20] tests/liveupdate: Add in-kernel liveupdate test

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

Introduce an in-kernel test module to validate the core logic of the
Live Update Orchestrator's File-Lifecycle-Bound feature. This
provides a low-level, controlled environment to test FLB registration
and callback invocation without requiring userspace interaction or
actual kexec reboots.

The test is enabled by the CONFIG_LIVEUPDATE_TEST Kconfig option.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 include/linux/liveupdate/abi/luo.h |   5 +
 kernel/liveupdate/luo_file.c       |   2 +
 kernel/liveupdate/luo_internal.h   |   6 ++
 lib/Kconfig.debug                  |  23 +++++
 lib/tests/Makefile                 |   1 +
 lib/tests/liveupdate.c             | 143 +++++++++++++++++++++++++++++
 6 files changed, 180 insertions(+)
 create mode 100644 lib/tests/liveupdate.c

diff --git a/include/linux/liveupdate/abi/luo.h b/include/linux/liveupdate/abi/luo.h
index 85596ce68c16..cdcace9b48f5 100644
--- a/include/linux/liveupdate/abi/luo.h
+++ b/include/linux/liveupdate/abi/luo.h
@@ -230,4 +230,9 @@ struct luo_flb_ser {
 	u64 count;
 } __packed;
 
+/* Kernel Live Update Test ABI */
+#ifdef CONFIG_LIVEUPDATE_TEST
+#define LIVEUPDATE_TEST_FLB_COMPATIBLE(i)	"liveupdate-test-flb-v" #i
+#endif
+
 #endif /* _LINUX_LIVEUPDATE_ABI_LUO_H */
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index df337c9c4f21..9a531096bdb5 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -834,6 +834,8 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
 	INIT_LIST_HEAD(&fh->flb_list);
 	list_add_tail(&fh->list, &luo_file_handler_list);
 
+	liveupdate_test_register(fh);
+
 	return 0;
 }
 
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index 389fb102775f..c863cb051d49 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -86,4 +86,10 @@ int __init luo_flb_setup_outgoing(void *fdt);
 int __init luo_flb_setup_incoming(void *fdt);
 void luo_flb_serialize(void);
 
+#ifdef CONFIG_LIVEUPDATE_TEST
+void liveupdate_test_register(struct liveupdate_file_handler *h);
+#else
+static inline void liveupdate_test_register(struct liveupdate_file_handler *h) { }
+#endif
+
 #endif /* _LINUX_LUO_INTERNAL_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9a087826498a..eaa2af2bd963 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2803,6 +2803,29 @@ config LINEAR_RANGES_TEST
 
 	  If unsure, say N.
 
+config LIVEUPDATE_TEST
+	bool "Live Update Kernel Test"
+	default n
+	depends on LIVEUPDATE
+	help
+	  Enable a built-in kernel test module for the Live Update
+	  Orchestrator.
+
+	  This module validates the File-Lifecycle-Bound subsystem by
+	  registering a set of mock FLB objects with any real file handlers
+	  that support live update (such as the memfd handler).
+
+	  When live update operations are performed, this test module will
+	  output messages to the kernel log (dmesg), confirming that its
+	  registration and various callback functions (preserve, retrieve,
+	  finish, etc.) are being invoked correctly.
+
+	  This is a debugging and regression testing tool for developers
+	  working on the Live Update subsystem. It should not be enabled in
+	  production kernels.
+
+	  If unsure, say N
+
 config CMDLINE_KUNIT_TEST
 	tristate "KUnit test for cmdline API" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/tests/Makefile b/lib/tests/Makefile
index f7460831cfdd..8e5c527a94ac 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
 obj-$(CONFIG_KFIFO_KUNIT_TEST) += kfifo_kunit.o
 obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o
 obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
+obj-$(CONFIG_LIVEUPDATE_TEST) += liveupdate.o
 
 CFLAGS_longest_symbol_kunit.o += $(call cc-disable-warning, missing-prototypes)
 obj-$(CONFIG_LONGEST_SYM_KUNIT_TEST) += longest_symbol_kunit.o
diff --git a/lib/tests/liveupdate.c b/lib/tests/liveupdate.c
new file mode 100644
index 000000000000..05c05b8c1c22
--- /dev/null
+++ b/lib/tests/liveupdate.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME " test: " fmt
+
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/liveupdate.h>
+#include <linux/module.h>
+#include "../../kernel/liveupdate/luo_internal.h"
+
+static const struct liveupdate_flb_ops test_flb_ops;
+#define DEFINE_TEST_FLB(i) {						\
+	.ops = &test_flb_ops,						\
+	.compatible = LIVEUPDATE_TEST_FLB_COMPATIBLE(i),		\
+}
+
+/* Number of Test FLBs to register with every file handler */
+#define TEST_NFLBS 3
+static struct liveupdate_flb test_flbs[TEST_NFLBS] = {
+	DEFINE_TEST_FLB(0),
+	DEFINE_TEST_FLB(1),
+	DEFINE_TEST_FLB(2),
+};
+
+#define TEST_FLB_MAGIC_BASE 0xFEEDF00DCAFEBEE0ULL
+
+static int test_flb_preserve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+
+	pr_info("%s: preserve was triggered\n", argp->flb->compatible);
+	argp->data = TEST_FLB_MAGIC_BASE + index;
+
+	return 0;
+}
+
+static void test_flb_unpreserve(struct liveupdate_flb_op_args *argp)
+{
+	pr_info("%s: unpreserve was triggered\n", argp->flb->compatible);
+}
+
+static int test_flb_retrieve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	u64 expected_data = TEST_FLB_MAGIC_BASE + index;
+
+	if (argp->data == expected_data) {
+		pr_info("%s: found flb data from the previous boot\n",
+			argp->flb->compatible);
+		argp->obj = (void *)argp->data;
+	} else {
+		pr_err("%s: ERROR - incorrect data handle: %llx, expected %llx\n",
+		       argp->flb->compatible, argp->data, expected_data);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void test_flb_finish(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	void *expected_obj = (void *)(TEST_FLB_MAGIC_BASE + index);
+
+	if (argp->obj == expected_obj) {
+		pr_info("%s: finish was triggered\n", argp->flb->compatible);
+	} else {
+		pr_err("%s: ERROR - finish called with invalid object\n",
+		       argp->flb->compatible);
+	}
+}
+
+static const struct liveupdate_flb_ops test_flb_ops = {
+	.preserve	= test_flb_preserve,
+	.unpreserve	= test_flb_unpreserve,
+	.retrieve	= test_flb_retrieve,
+	.finish		= test_flb_finish,
+	.owner		= THIS_MODULE,
+};
+
+static void liveupdate_test_init(void)
+{
+	static DEFINE_MUTEX(init_lock);
+	static bool initialized;
+	int i;
+
+	guard(mutex)(&init_lock);
+
+	if (initialized)
+		return;
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+		void *obj;
+		int err;
+
+		liveupdate_init_flb(flb);
+
+		err = liveupdate_flb_incoming_locked(flb, &obj);
+		if (!err) {
+			liveupdate_flb_incoming_unlock(flb, obj);
+		} else if (err != -ENODATA && err != -ENOENT) {
+			pr_err("liveupdate_flb_incoming_locked for %s failed: %pe\n",
+			       flb->compatible, ERR_PTR(err));
+		}
+	}
+	initialized = true;
+}
+
+void liveupdate_test_register(struct liveupdate_file_handler *h)
+{
+	int err, i;
+
+	liveupdate_test_init();
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+
+		err = liveupdate_register_flb(h, flb);
+		if (err)
+			pr_err("Failed to register %s %pe\n",
+			       flb->compatible, ERR_PTR(err));
+	}
+
+	err = liveupdate_register_flb(h, &test_flbs[0]);
+	if (!err || err != -EEXIST) {
+		pr_err("Failed: %s should be already registered, but got err: %pe\n",
+		       test_flbs[0].compatible, ERR_PTR(err));
+	}
+
+	pr_info("Registered %d FLBs with file handler: [%s]\n",
+		TEST_NFLBS, h->compatible);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pasha Tatashin <pasha.tatashin@soleen.com>");
+MODULE_DESCRIPTION("In-kernel test for LUO mechanism");
-- 
2.52.0.rc1.455.g30608eb744-goog