This is simple test and playground useful kstate subsystem development.
It contains some structure with different kind of data which migrated
across kexec to the new kernel using kstate.

Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
---
 include/linux/kstate.h |  1 +
 lib/Makefile           |  2 +
 lib/test_kstate.c      | 89 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 lib/test_kstate.c

diff --git a/include/linux/kstate.h b/include/linux/kstate.h
index 855acb339d5d7..2ddbe41a1f171 100644
--- a/include/linux/kstate.h
+++ b/include/linux/kstate.h
@@ -31,6 +31,7 @@ struct kstate_field {
 enum kstate_ids {
 	KSTATE_PAGE_ID,
 	KSTATE_RSVD_MEM_ID,
+	KSTATE_TEST_ID,
 	KSTATE_LAST_ID = -1,
 };
 
diff --git a/lib/Makefile b/lib/Makefile
index 773adf88af416..2432e47664c35 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -354,6 +354,8 @@ obj-$(CONFIG_PARMAN) += parman.o
 
 obj-y += group_cpus.o
 
+obj-$(CONFIG_KSTATE) += test_kstate.o
+
 # GCC library routines
 obj-$(CONFIG_GENERIC_LIB_ASHLDI3) += ashldi3.o
 obj-$(CONFIG_GENERIC_LIB_ASHRDI3) += ashrdi3.o
diff --git a/lib/test_kstate.c b/lib/test_kstate.c
new file mode 100644
index 0000000000000..e95e3110f8949
--- /dev/null
+++ b/lib/test_kstate.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/io.h>
+#include <linux/kstate.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+
+unsigned long ulong_val;
+struct kstate_test_data {
+	int i;
+	unsigned long *p_ulong;
+	char s[10];
+	struct page *page;
+};
+
+struct kstate_description test_state = {
+	.name = "test",
+	.version_id = 1,
+	.id = KSTATE_TEST_ID,
+	.state_list = LIST_HEAD_INIT(test_state.state_list),
+	.fields = (const struct kstate_field[]) {
+		KSTATE_SIMPLE(i, struct kstate_test_data),
+		KSTATE_SIMPLE(s, struct kstate_test_data),
+		KSTATE_POINTER(p_ulong, struct kstate_test_data),
+		{
+			.name = "page",
+			.flags = KS_CUSTOM,
+			.offset = offsetof(struct kstate_test_data, page),
+			.save = kstate_page_save,
+		},
+		KSTATE_SIMPLE(page, struct kstate_test_data),
+		KSTATE_END_OF_LIST()
+	},
+};
+
+static struct kstate_test_data test_data;
+
+static int init_test_data(void)
+{
+	struct page *page;
+	int i;
+
+	test_data.i = 10;
+	ulong_val = 20;
+	memcpy(test_data.s, "abcdefghk", sizeof(test_data.s));
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	for (i = 0; i < PAGE_SIZE/4; i += 4)
+		*((u32 *)page_address(page) + i) = 0xdeadbeef;
+	test_data.page = page;
+	return 0;
+}
+
+static void validate_test_data(void)
+{
+	int i;
+
+	WARN_ON(test_data.i != 10);
+	WARN_ON(*test_data.p_ulong != 20);
+	WARN_ON(strcmp(test_data.s, "abcdefghk") != 0);
+
+	for (i = 0; i < PAGE_SIZE/4; i += 4) {
+		u32 val = *((u32 *)page_address(test_data.page) + i);
+
+		WARN_ON(val != 0xdeadbeef);
+	}
+}
+
+static int __init test_kstate_init(void)
+{
+	int ret = 0;
+
+	test_data.p_ulong = &ulong_val;
+
+	if (!is_migrate_kernel()) {
+		ret = init_test_data();
+		if (ret)
+			goto out;
+	}
+
+	kstate_register(&test_state, &test_data);
+
+	validate_test_data();
+
+out:
+	return ret;
+}
+__initcall(test_kstate_init);
-- 
2.45.2