[RFC PATCH v3 4/4] liveupdate: Add KUnit test for the feature header helpers

[Tarun Sahu <tarunsahu@google.com>]

Add a KUnit test suite in lib/tests/liveupdate_feature_kunit.c covering
the Live Update feature header declared in include/linux/kho/abi/luo.h.

The suite contains two focused test cases:
- luo_ser_hdr_set_get_test: verifies DECLARE_LUO_SER_WRAP structure
  sizing, header initialization, payload pointer resolution, and 2-bit
  feature flag setting and retrieval across flags entry boundaries,
  including out-of-range queries.
- luo_ser_hdr_truth_table_test: verifies luo_ser_hdr_validate against
  all rows of the feature state truth table (absent, optional,
  required, and reserved 0b10 encodings), as well as empty supported
  tables.

Signed-off-by: Tarun Sahu <tarunsahu@google.com>
---
 MAINTAINERS                          |   1 +
 lib/Kconfig.debug                    |  16 ++++
 lib/tests/Makefile                   |   1 +
 lib/tests/liveupdate_feature_kunit.c | 118 +++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 lib/tests/liveupdate_feature_kunit.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5d1b58271989..dad09961c275 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15191,6 +15191,7 @@ F:	include/linux/liveupdate.h
 F:	include/uapi/linux/liveupdate.h
 F:	kernel/liveupdate/
 F:	lib/tests/liveupdate.c
+F:	lib/tests/liveupdate_feature_kunit.c
 F:	mm/memfd_luo.c
 F:	tools/testing/selftests/liveupdate/
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 134b15a44625..d8208f3f4515 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2906,6 +2906,22 @@ config LIVEUPDATE_TEST
 
 	  If unsure, say N
 
+config LIVEUPDATE_FEATURE_KUNIT_TEST
+	tristate "KUnit test for the Live Update feature header helpers" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This option enables the KUnit test suite for the Live Update
+	  Orchestrator feature header helpers defined in
+	  include/linux/kho/abi/luo.h. It checks the feature flag encoding,
+	  the flags array sizing, the source/target kernel validation
+	  truth table, header initialization and the payload size checks.
+
+	  The helpers are self-contained, so the test does not depend on
+	  CONFIG_LIVEUPDATE and can also run under UML.
+
+	  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 3cac3b63a752..2f1f1f765617 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -33,6 +33,7 @@ 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
+obj-$(CONFIG_LIVEUPDATE_FEATURE_KUNIT_TEST) += liveupdate_feature_kunit.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_feature_kunit.c b/lib/tests/liveupdate_feature_kunit.c
new file mode 100644
index 000000000000..fc9d2de263d9
--- /dev/null
+++ b/lib/tests/liveupdate_feature_kunit.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for the Live Update Orchestrator feature header helpers
+ * in include/linux/kho/abi/luo.h.
+ *
+ * Copyright (c) 2026, Google LLC.
+ * Tarun Sahu <tarunsahu@google.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/kho/abi/luo.h>
+#include <linux/module.h>
+
+struct luo_test_multi_ser {
+	u64 val;
+};
+
+static_assert(sizeof(struct luo_test_multi_ser) == 8);
+DECLARE_LUO_SER_WRAP(luo_test_multi_ser, 32, 35);
+
+struct luo_test_one_ser {
+	u64 val;
+};
+
+static_assert(sizeof(struct luo_test_one_ser) == 8);
+DECLARE_LUO_SER_WRAP(luo_test_one_ser, 24, 1);
+
+struct luo_test_zero_ser {
+	u64 val;
+};
+
+static_assert(sizeof(struct luo_test_zero_ser) == 8);
+DECLARE_LUO_SER_WRAP(luo_test_zero_ser, 16, 0);
+
+static void luo_ser_hdr_set_get_test(struct kunit *test)
+{
+	struct luo_test_multi_ser_wrap out;
+	struct luo_test_zero_ser_wrap zero;
+
+	memset(&out, 0, sizeof(out));
+	luo_test_multi_ser_wrap_init(&out);
+
+	KUNIT_EXPECT_EQ(test, out.hdr.size, 32U);
+	KUNIT_EXPECT_EQ(test, out.hdr.nr_features, 35U);
+	KUNIT_EXPECT_EQ(test, LUO_SER_NR_FLAGS(out.hdr.nr_features), 2U);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_size(&out.hdr), 24UL);
+	KUNIT_EXPECT_PTR_EQ(test, luo_ser_payload(&out.hdr), (void *)&out.ser);
+
+	/* 0, 31 in flags[0]; 32, 34 in flags[1] */
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_REQUIRED);
+	luo_ser_set_feat(&out.hdr, 31, LUO_FEAT_OPTIONAL);
+	luo_ser_set_feat(&out.hdr, 32, LUO_FEAT_REQUIRED);
+	luo_ser_set_feat(&out.hdr, 34, LUO_FEAT_OPTIONAL);
+
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 0), (int)LUO_FEAT_REQUIRED);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 1), (int)LUO_FEAT_ABSENT);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 31), (int)LUO_FEAT_OPTIONAL);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 32), (int)LUO_FEAT_REQUIRED);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 33), (int)LUO_FEAT_ABSENT);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 34), (int)LUO_FEAT_OPTIONAL);
+
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 35), (int)LUO_FEAT_ABSENT);
+	KUNIT_EXPECT_EQ(test, (int)luo_ser_get_feat(&out.hdr, 100), (int)LUO_FEAT_ABSENT);
+
+	memset(&zero, 0, sizeof(zero));
+	luo_test_zero_ser_wrap_init(&zero);
+	KUNIT_EXPECT_EQ(test, sizeof(struct luo_ser_hdr), 8UL);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_size(&zero.hdr), 8UL);
+	KUNIT_EXPECT_PTR_EQ(test, luo_ser_payload(&zero.hdr), (void *)&zero.ser);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&zero.hdr, NULL, 0), 0);
+}
+
+static void luo_ser_hdr_truth_table_test(struct kunit *test)
+{
+	struct luo_test_one_ser_wrap out;
+	bool supp_yes[1] = { true };
+	bool supp_no[1] = { false };
+
+	memset(&out, 0, sizeof(out));
+	luo_test_one_ser_wrap_init(&out);
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_ABSENT);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_no, 1), 0);
+
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_OPTIONAL);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_no, 1), 0);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_yes, 1), 0);
+
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_REQUIRED);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_no, 1),
+			-EOPNOTSUPP);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_yes, 1), 0);
+
+	out.flags[0] = (u64)LUO_FEAT_RESERVED;
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_no, 1), 0);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, supp_yes, 1), 0);
+
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_REQUIRED);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, NULL, 0),
+			-EOPNOTSUPP);
+	luo_ser_set_feat(&out.hdr, 0, LUO_FEAT_OPTIONAL);
+	KUNIT_EXPECT_EQ(test, luo_ser_hdr_validate(&out.hdr, NULL, 0), 0);
+}
+
+static struct kunit_case luo_feature_test_cases[] = {
+	KUNIT_CASE(luo_ser_hdr_set_get_test),
+	KUNIT_CASE(luo_ser_hdr_truth_table_test),
+	{}
+};
+
+static struct kunit_suite luo_feature_test_suite = {
+	.name = "liveupdate_feature",
+	.test_cases = luo_feature_test_cases,
+};
+
+kunit_test_suite(luo_feature_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the Live Update feature header helpers");
+MODULE_LICENSE("GPL");
-- 
2.56.0.307.g5fe7bd680c-goog