of: address: Add kunit test for __of_address_resource_bounds()

The overflow checking has to deal with different datatypes and
edgecases. Add a new kunit testcase to make sure it works correctly.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://lore.kernel.org/r/20250129-of-address-overflow-v3-1-95d1760ed791@linutronix.de
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Author: t-8ch

drivers/of/address.c

@@ -16,6 +16,8 @@
 #include <linux/string.h>
 #include <linux/dma-direct.h> /* for bus_dma_region */
 
+#include <kunit/visibility.h>
+
 /* Uncomment me to enable of_dump_addr() debugging output */
 // #define DEBUG
 
@@ -183,7 +185,7 @@ static u64 of_bus_pci_map(__be32 *addr, const __be32 *range, int na, int ns,
 
 #endif /* CONFIG_PCI */
 
-static int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
+VISIBLE_IF_KUNIT int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
 {
 	if (overflows_type(start, r->start))
 		return -EOVERFLOW;
@@ -197,6 +199,7 @@ static int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
 
 	return 0;
 }
+EXPORT_SYMBOL_IF_KUNIT(__of_address_resource_bounds);
 
 /*
  * of_pci_range_to_resource - Create a resource from an of_pci_range

drivers/of/of_private.h

@@ -208,4 +208,8 @@ static void __maybe_unused of_dump_addr(const char *s, const __be32 *addr, int n
 static void __maybe_unused of_dump_addr(const char *s, const __be32 *addr, int na) { }
 #endif
 
+#if IS_ENABLED(CONFIG_KUNIT)
+int __of_address_resource_bounds(struct resource *r, u64 start, u64 size);
+#endif
+
 #endif /* _LINUX_OF_PRIVATE_H */

drivers/of/of_test.c

@@ -2,6 +2,7 @@
 /*
  * KUnit tests for OF APIs
  */
+#include <linux/ioport.h>
 #include <linux/module.h>
 #include <linux/of.h>
 
@@ -54,8 +55,124 @@ static struct kunit_suite of_dtb_suite = {
 	.init = of_dtb_test_init,
 };
 
+struct of_address_resource_bounds_case {
+	u64 start;
+	u64 size;
+	int ret;
+
+	u64 res_start;
+	u64 res_end;
+};
+
+static void of_address_resource_bounds_case_desc(const struct of_address_resource_bounds_case *p,
+						 char *name)
+{
+	snprintf(name, KUNIT_PARAM_DESC_SIZE, "start=0x%016llx,size=0x%016llx", p->start, p->size);
+}
+
+static const struct of_address_resource_bounds_case of_address_resource_bounds_cases[] = {
+	{
+		.start = 0,
+		.size = 0,
+		.ret = 0,
+		.res_start = 0,
+		.res_end = -1,
+	},
+	{
+		.start = 0,
+		.size = 0x1000,
+		.ret = 0,
+		.res_start = 0,
+		.res_end = 0xfff,
+	},
+	{
+		.start = 0x1000,
+		.size = 0,
+		.ret = 0,
+		.res_start = 0x1000,
+		.res_end = 0xfff,
+	},
+	{
+		.start = 0x1000,
+		.size = 0x1000,
+		.ret = 0,
+		.res_start = 0x1000,
+		.res_end = 0x1fff,
+	},
+	{
+		.start = 1,
+		.size = RESOURCE_SIZE_MAX,
+		.ret = 0,
+		.res_start = 1,
+		.res_end = RESOURCE_SIZE_MAX,
+	},
+	{
+		.start = RESOURCE_SIZE_MAX,
+		.size = 1,
+		.ret = 0,
+		.res_start = RESOURCE_SIZE_MAX,
+		.res_end = RESOURCE_SIZE_MAX,
+	},
+	{
+		.start = 2,
+		.size = RESOURCE_SIZE_MAX,
+		.ret = -EOVERFLOW,
+	},
+	{
+		.start = RESOURCE_SIZE_MAX,
+		.size = 2,
+		.ret = -EOVERFLOW,
+	},
+	{
+		.start = ULL(0x100000000),
+		.size = 1,
+		.ret = sizeof(resource_size_t) > sizeof(u32) ? 0 : -EOVERFLOW,
+		.res_start = ULL(0x100000000),
+		.res_end = ULL(0x100000000),
+	},
+	{
+		.start = 0x1000,
+		.size = 0xffffffff,
+		.ret = sizeof(resource_size_t) > sizeof(u32) ? 0 : -EOVERFLOW,
+		.res_start = 0x1000,
+		.res_end = ULL(0x100000ffe),
+	},
+};
+
+KUNIT_ARRAY_PARAM(of_address_resource_bounds,
+		  of_address_resource_bounds_cases, of_address_resource_bounds_case_desc);
+
+static void of_address_resource_bounds(struct kunit *test)
+{
+	const struct of_address_resource_bounds_case *param = test->param_value;
+	struct resource r; /* Intentionally uninitialized */
+	int ret;
+
+	if (!IS_ENABLED(CONFIG_OF_ADDRESS))
+		kunit_skip(test, "CONFIG_OF_ADDRESS not enabled\n");
+
+	ret = __of_address_resource_bounds(&r, param->start, param->size);
+	KUNIT_EXPECT_EQ(test, param->ret, ret);
+	if (ret == 0) {
+		KUNIT_EXPECT_EQ(test, (resource_size_t)param->res_start, r.start);
+		KUNIT_EXPECT_EQ(test, (resource_size_t)param->res_end, r.end);
+		KUNIT_EXPECT_EQ(test, param->size, resource_size(&r));
+	}
+}
+
+static struct kunit_case of_address_test_cases[] = {
+	KUNIT_CASE_PARAM(of_address_resource_bounds, of_address_resource_bounds_gen_params),
+	{}
+};
+
+static struct kunit_suite of_address_suite = {
+	.name = "of_address",
+	.test_cases = of_address_test_cases,
+};
+
 kunit_test_suites(
-	&of_dtb_suite,
+	&of_dtb_suite, &of_address_suite,
 );
 MODULE_DESCRIPTION("KUnit tests for OF APIs");
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
 MODULE_LICENSE("GPL");