lib/memcpy_kunit.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test cases for memcpy(), memmove(), and memset().
  */
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <kunit/test.h>
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/overflow.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>

 struct some_bytes {
 	union {
 		u8 data[32];
 		struct {
 			u32 one;
 			u16 two;
 			u8  three;
 			/* 1 byte hole */
 			u32 four[4];
 		};
 	};
 };

 #define check(instance, v) do {	\
 	BUILD_BUG_ON(sizeof(instance.data) != 32);	\
 	for (size_t i = 0; i < sizeof(instance.data); i++) {	\
 		KUNIT_ASSERT_EQ_MSG(test, instance.data[i], v, \
 			"line %d: '%s' not initialized to 0x%02x @ %zu (saw 0x%02x)\n", \
 			__LINE__, #instance, v, i, instance.data[i]);	\
 	}	\
 } while (0)

 #define compare(name, one, two) do { \
 	BUILD_BUG_ON(sizeof(one) != sizeof(two)); \
 	for (size_t i = 0; i < sizeof(one); i++) {	\
 		KUNIT_EXPECT_EQ_MSG(test, one.data[i], two.data[i], \
 			"line %d: %s.data[%zu] (0x%02x) != %s.data[%zu] (0x%02x)\n", \
 			__LINE__, #one, i, one.data[i], #two, i, two.data[i]); \
 	}	\
 	kunit_info(test, "ok: " TEST_OP "() " name "\n");	\
 } while (0)

 static void memcpy_test(struct kunit *test)
 {
 #define TEST_OP "memcpy"
 	struct some_bytes control = {
 		.data = { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			},
 	};
 	struct some_bytes zero = { };
 	struct some_bytes middle = {
 		.data = { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0x00,
 			  0x00, 0x00, 0x00, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			},
 	};
 	struct some_bytes three = {
 		.data = { 0x00, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x00, 0x00, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			  0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
 			},
 	};
 	struct some_bytes dest = { };
 	int count;
 	u8 *ptr;

 	/* Verify static initializers. */
 	check(control, 0x20);
 	check(zero, 0);
 	compare("static initializers", dest, zero);

 	/* Verify assignment. */
 	dest = control;
 	compare("direct assignment", dest, control);

 	/* Verify complete overwrite. */
 	memcpy(dest.data, zero.data, sizeof(dest.data));
 	compare("complete overwrite", dest, zero);

 	/* Verify middle overwrite. */
 	dest = control;
 	memcpy(dest.data + 12, zero.data, 7);
 	compare("middle overwrite", dest, middle);

 	/* Verify argument side-effects aren't repeated. */
 	dest = control;
 	ptr = dest.data;
 	count = 1;
 	memcpy(ptr++, zero.data, count++);
 	ptr += 8;
 	memcpy(ptr++, zero.data, count++);
 	compare("argument side-effects", dest, three);
 #undef TEST_OP
 }

 static unsigned char larger_array [2048];

 static void memmove_test(struct kunit *test)
 {
 #define TEST_OP "memmove"
 	struct some_bytes control = {
 		.data = { 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			},
 	};
 	struct some_bytes zero = { };
 	struct some_bytes middle = {
 		.data = { 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x00, 0x00, 0x00, 0x00,
 			  0x00, 0x00, 0x00, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			},
 	};
 	struct some_bytes five = {
 		.data = { 0x00, 0x00, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x00, 0x00, 0x00, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			},
 	};
 	struct some_bytes overlap = {
 		.data = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
 			  0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			},
 	};
 	struct some_bytes overlap_expected = {
 		.data = { 0x00, 0x01, 0x00, 0x01, 0x02, 0x03, 0x04, 0x07,
 			  0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			  0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
 			},
 	};
 	struct some_bytes dest = { };
 	int count;
 	u8 *ptr;

 	/* Verify static initializers. */
 	check(control, 0x99);
 	check(zero, 0);
 	compare("static initializers", zero, dest);

 	/* Verify assignment. */
 	dest = control;
 	compare("direct assignment", dest, control);

 	/* Verify complete overwrite. */
 	memmove(dest.data, zero.data, sizeof(dest.data));
 	compare("complete overwrite", dest, zero);

 	/* Verify middle overwrite. */
 	dest = control;
 	memmove(dest.data + 12, zero.data, 7);
 	compare("middle overwrite", dest, middle);

 	/* Verify argument side-effects aren't repeated. */
 	dest = control;
 	ptr = dest.data;
 	count = 2;
 	memmove(ptr++, zero.data, count++);
 	ptr += 9;
 	memmove(ptr++, zero.data, count++);
 	compare("argument side-effects", dest, five);

 	/* Verify overlapping overwrite is correct. */
 	ptr = &overlap.data[2];
 	memmove(ptr, overlap.data, 5);
 	compare("overlapping write", overlap, overlap_expected);

 	/* Verify larger overlapping moves. */
 	larger_array[256] = 0xAAu;
 	/*
 	 * Test a backwards overlapping memmove first. 256 and 1024 are
 	 * important for i386 to use rep movsl.
 	 */
 	memmove(larger_array, larger_array + 256, 1024);
 	KUNIT_ASSERT_EQ(test, larger_array[0], 0xAAu);
 	KUNIT_ASSERT_EQ(test, larger_array[256], 0x00);
 	KUNIT_ASSERT_NULL(test,
 		memchr(larger_array + 1, 0xaa, ARRAY_SIZE(larger_array) - 1));
 	/* Test a forwards overlapping memmove. */
 	larger_array[0] = 0xBBu;
 	memmove(larger_array + 256, larger_array, 1024);
 	KUNIT_ASSERT_EQ(test, larger_array[0], 0xBBu);
 	KUNIT_ASSERT_EQ(test, larger_array[256], 0xBBu);
 	KUNIT_ASSERT_NULL(test, memchr(larger_array + 1, 0xBBu, 256 - 1));
 	KUNIT_ASSERT_NULL(test,
 		memchr(larger_array + 257, 0xBBu, ARRAY_SIZE(larger_array) - 257));
 #undef TEST_OP
 }

 static void memset_test(struct kunit *test)
 {
 #define TEST_OP "memset"
 	struct some_bytes control = {
 		.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			},
 	};
 	struct some_bytes complete = {
 		.data = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 			  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 			  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 			  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 			},
 	};
 	struct some_bytes middle = {
 		.data = { 0x30, 0x30, 0x30, 0x30, 0x31, 0x31, 0x31, 0x31,
 			  0x31, 0x31, 0x31, 0x31, 0x31, 0x31, 0x31, 0x31,
 			  0x31, 0x31, 0x31, 0x31, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			},
 	};
 	struct some_bytes three = {
 		.data = { 0x60, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x61, 0x61, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			},
 	};
 	struct some_bytes after = {
 		.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x72,
 			  0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
 			  0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
 			  0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
 			},
 	};
 	struct some_bytes startat = {
 		.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
 			  0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
 			  0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
 			  0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
 			},
 	};
 	struct some_bytes dest = { };
 	int count, value;
 	u8 *ptr;

 	/* Verify static initializers. */
 	check(control, 0x30);
 	check(dest, 0);

 	/* Verify assignment. */
 	dest = control;
 	compare("direct assignment", dest, control);

 	/* Verify complete overwrite. */
 	memset(dest.data, 0xff, sizeof(dest.data));
 	compare("complete overwrite", dest, complete);

 	/* Verify middle overwrite. */
 	dest = control;
 	memset(dest.data + 4, 0x31, 16);
 	compare("middle overwrite", dest, middle);

 	/* Verify argument side-effects aren't repeated. */
 	dest = control;
 	ptr = dest.data;
 	value = 0x60;
 	count = 1;
 	memset(ptr++, value++, count++);
 	ptr += 8;
 	memset(ptr++, value++, count++);
 	compare("argument side-effects", dest, three);

 	/* Verify memset_after() */
 	dest = control;
 	memset_after(&dest, 0x72, three);
 	compare("memset_after()", dest, after);

 	/* Verify memset_startat() */
 	dest = control;
 	memset_startat(&dest, 0x79, four);
 	compare("memset_startat()", dest, startat);
 #undef TEST_OP
 }

 static u8 large_src[1024];
 static u8 large_dst[2048];
 static const u8 large_zero[2048];

 static void set_random_nonzero(struct kunit *test, u8 *byte)
 {
 	int failed_rng = 0;

 	while (*byte == 0) {
 		get_random_bytes(byte, 1);
 		KUNIT_ASSERT_LT_MSG(test, failed_rng++, 100,
 				    "Is the RNG broken?");
 	}
 }

 static void init_large(struct kunit *test)
 {
 	/* Get many bit patterns. */
 	get_random_bytes(large_src, ARRAY_SIZE(large_src));

 	/* Make sure we have non-zero edges. */
 	set_random_nonzero(test, &large_src[0]);
 	set_random_nonzero(test, &large_src[ARRAY_SIZE(large_src) - 1]);

 	/* Explicitly zero the entire destination. */
 	memset(large_dst, 0, ARRAY_SIZE(large_dst));
 }

 /*
  * Instead of an indirect function call for "copy" or a giant macro,
  * use a bool to pick memcpy or memmove.
  */
 static void copy_large_test(struct kunit *test, bool use_memmove)
 {
 	init_large(test);

 	/* Copy a growing number of non-overlapping bytes ... */
 	for (int bytes = 1; bytes <= ARRAY_SIZE(large_src); bytes++) {
 		/* Over a shifting destination window ... */
 		for (int offset = 0; offset < ARRAY_SIZE(large_src); offset++) {
 			int right_zero_pos = offset + bytes;
 			int right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

 			/* Copy! */
 			if (use_memmove)
 				memmove(large_dst + offset, large_src, bytes);
 			else
 				memcpy(large_dst + offset, large_src, bytes);

 			/* Did we touch anything before the copy area? */
 			KUNIT_ASSERT_EQ_MSG(test,
 				memcmp(large_dst, large_zero, offset), 0,
 				"with size %d at offset %d", bytes, offset);
 			/* Did we touch anything after the copy area? */
 			KUNIT_ASSERT_EQ_MSG(test,
 				memcmp(&large_dst[right_zero_pos], large_zero, right_zero_size), 0,
 				"with size %d at offset %d", bytes, offset);

 			/* Are we byte-for-byte exact across the copy? */
 			KUNIT_ASSERT_EQ_MSG(test,
 				memcmp(large_dst + offset, large_src, bytes), 0,
 				"with size %d at offset %d", bytes, offset);

 			/* Zero out what we copied for the next cycle. */
 			memset(large_dst + offset, 0, bytes);
 		}
 		/* Avoid stall warnings if this loop gets slow. */
 		cond_resched();
 	}
 }

 static void memcpy_large_test(struct kunit *test)
 {
 	copy_large_test(test, false);
 }

 static void memmove_large_test(struct kunit *test)
 {
 	copy_large_test(test, true);
 }

 /*
  * On the assumption that boundary conditions are going to be the most
  * sensitive, instead of taking a full step (inc) each iteration,
  * take single index steps for at least the first "inc"-many indexes
  * from the "start" and at least the last "inc"-many indexes before
  * the "end". When in the middle, take full "inc"-wide steps. For
  * example, calling next_step(idx, 1, 15, 3) with idx starting at 0
  * would see the following pattern: 1 2 3 4 7 10 11 12 13 14 15.
  */
 static int next_step(int idx, int start, int end, int inc)
 {
 	start += inc;
 	end -= inc;

 	if (idx < start || idx + inc > end)
 		inc = 1;
 	return idx + inc;
 }

 static void inner_loop(struct kunit *test, int bytes, int d_off, int s_off)
 {
 	int left_zero_pos, left_zero_size;
 	int right_zero_pos, right_zero_size;
 	int src_pos, src_orig_pos, src_size;
 	int pos;

 	/* Place the source in the destination buffer. */
 	memcpy(&large_dst[s_off], large_src, bytes);

 	/* Copy to destination offset. */
 	memmove(&large_dst[d_off], &large_dst[s_off], bytes);

 	/* Make sure destination entirely matches. */
 	KUNIT_ASSERT_EQ_MSG(test, memcmp(&large_dst[d_off], large_src, bytes), 0,
 		"with size %d at src offset %d and dest offset %d",
 		bytes, s_off, d_off);

 	/* Calculate the expected zero spans. */
 	if (s_off < d_off) {
 		left_zero_pos = 0;
 		left_zero_size = s_off;

 		right_zero_pos = d_off + bytes;
 		right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

 		src_pos = s_off;
 		src_orig_pos = 0;
 		src_size = d_off - s_off;
 	} else {
 		left_zero_pos = 0;
 		left_zero_size = d_off;

 		right_zero_pos = s_off + bytes;
 		right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

 		src_pos = d_off + bytes;
 		src_orig_pos = src_pos - s_off;
 		src_size = right_zero_pos - src_pos;
 	}

 	/* Check non-overlapping source is unchanged.*/
 	KUNIT_ASSERT_EQ_MSG(test,
 		memcmp(&large_dst[src_pos], &large_src[src_orig_pos], src_size), 0,
 		"with size %d at src offset %d and dest offset %d",
 		bytes, s_off, d_off);

 	/* Check leading buffer contents are zero. */
 	KUNIT_ASSERT_EQ_MSG(test,
 		memcmp(&large_dst[left_zero_pos], large_zero, left_zero_size), 0,
 		"with size %d at src offset %d and dest offset %d",
 		bytes, s_off, d_off);
 	/* Check trailing buffer contents are zero. */
 	KUNIT_ASSERT_EQ_MSG(test,
 		memcmp(&large_dst[right_zero_pos], large_zero, right_zero_size), 0,
 		"with size %d at src offset %d and dest offset %d",
 		bytes, s_off, d_off);

 	/* Zero out everything not already zeroed.*/
 	pos = left_zero_pos + left_zero_size;
 	memset(&large_dst[pos], 0, right_zero_pos - pos);
 }

 static void memmove_overlap_test(struct kunit *test)
 {
 	/*
 	 * Running all possible offset and overlap combinations takes a
 	 * very long time. Instead, only check up to 128 bytes offset
 	 * into the destination buffer (which should result in crossing
 	 * cachelines), with a step size of 1 through 7 to try to skip some
 	 * redundancy.
 	 */
 	static const int offset_max = 128; /* less than ARRAY_SIZE(large_src); */
 	static const int bytes_step = 7;
 	static const int window_step = 7;

 	static const int bytes_start = 1;
 	static const int bytes_end = ARRAY_SIZE(large_src) + 1;

 	init_large(test);

 	/* Copy a growing number of overlapping bytes ... */
 	for (int bytes = bytes_start; bytes < bytes_end;
 	     bytes = next_step(bytes, bytes_start, bytes_end, bytes_step)) {

 		/* Over a shifting destination window ... */
 		for (int d_off = 0; d_off < offset_max; d_off++) {
 			int s_start = max(d_off - bytes, 0);
 			int s_end = min_t(int, d_off + bytes, ARRAY_SIZE(large_src));

 			/* Over a shifting source window ... */
 			for (int s_off = s_start; s_off < s_end;
 			     s_off = next_step(s_off, s_start, s_end, window_step))
 				inner_loop(test, bytes, d_off, s_off);

 			/* Avoid stall warnings. */
 			cond_resched();
 		}
 	}
 }

 static struct kunit_case memcpy_test_cases[] = {
 	KUNIT_CASE(memset_test),
 	KUNIT_CASE(memcpy_test),
 	KUNIT_CASE_SLOW(memcpy_large_test),
 	KUNIT_CASE_SLOW(memmove_test),
 	KUNIT_CASE_SLOW(memmove_large_test),
 	KUNIT_CASE_SLOW(memmove_overlap_test),
 	{}
 };

 static struct kunit_suite memcpy_test_suite = {
 	.name = "memcpy",
 	.test_cases = memcpy_test_cases,
 };

 kunit_test_suite(memcpy_test_suite);

 MODULE_DESCRIPTION("test cases for memcpy(), memmove(), and memset()");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Test cases for memcpy(), memmove(), and memset().
	*/
	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <kunit/test.h>
	#include <linux/device.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/module.h>
	#include <linux/overflow.h>
	#include <linux/slab.h>
	#include <linux/types.h>
	#include <linux/vmalloc.h>

	struct some_bytes {
	union {
	u8 data[32];
	struct {
	u32 one;
	u16 two;
	u8 three;
	/* 1 byte hole */
	u32 four[4];
	};
	};
	};

	#define check(instance, v) do { \
	BUILD_BUG_ON(sizeof(instance.data) != 32); \
	for (size_t i = 0; i < sizeof(instance.data); i++) { \
	KUNIT_ASSERT_EQ_MSG(test, instance.data[i], v, \
	"line %d: '%s' not initialized to 0x%02x @ %zu (saw 0x%02x)\n", \
	__LINE__, #instance, v, i, instance.data[i]); \
	} \
	} while (0)

	#define compare(name, one, two) do { \
	BUILD_BUG_ON(sizeof(one) != sizeof(two)); \
	for (size_t i = 0; i < sizeof(one); i++) { \
	KUNIT_EXPECT_EQ_MSG(test, one.data[i], two.data[i], \
	"line %d: %s.data[%zu] (0x%02x) != %s.data[%zu] (0x%02x)\n", \
	__LINE__, #one, i, one.data[i], #two, i, two.data[i]); \
	} \
	kunit_info(test, "ok: " TEST_OP "() " name "\n"); \
	} while (0)

	static void memcpy_test(struct kunit *test)
	{
	#define TEST_OP "memcpy"
	struct some_bytes control = {
	.data = { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	},
	};
	struct some_bytes zero = { };
	struct some_bytes middle = {
	.data = { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	},
	};
	struct some_bytes three = {
	.data = { 0x00, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x00, 0x00, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
	},
	};
	struct some_bytes dest = { };
	int count;
	u8 *ptr;

	/* Verify static initializers. */
	check(control, 0x20);
	check(zero, 0);
	compare("static initializers", dest, zero);

	/* Verify assignment. */
	dest = control;
	compare("direct assignment", dest, control);

	/* Verify complete overwrite. */
	memcpy(dest.data, zero.data, sizeof(dest.data));
	compare("complete overwrite", dest, zero);

	/* Verify middle overwrite. */
	dest = control;
	memcpy(dest.data + 12, zero.data, 7);
	compare("middle overwrite", dest, middle);

	/* Verify argument side-effects aren't repeated. */
	dest = control;
	ptr = dest.data;
	count = 1;
	memcpy(ptr++, zero.data, count++);
	ptr += 8;
	memcpy(ptr++, zero.data, count++);
	compare("argument side-effects", dest, three);
	#undef TEST_OP
	}

	static unsigned char larger_array [2048];

	static void memmove_test(struct kunit *test)
	{
	#define TEST_OP "memmove"
	struct some_bytes control = {
	.data = { 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	},
	};
	struct some_bytes zero = { };
	struct some_bytes middle = {
	.data = { 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	},
	};
	struct some_bytes five = {
	.data = { 0x00, 0x00, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x00, 0x00, 0x00, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	},
	};
	struct some_bytes overlap = {
	.data = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	},
	};
	struct some_bytes overlap_expected = {
	.data = { 0x00, 0x01, 0x00, 0x01, 0x02, 0x03, 0x04, 0x07,
	0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99, 0x99,
	},
	};
	struct some_bytes dest = { };
	int count;
	u8 *ptr;

	/* Verify static initializers. */
	check(control, 0x99);
	check(zero, 0);
	compare("static initializers", zero, dest);

	/* Verify assignment. */
	dest = control;
	compare("direct assignment", dest, control);

	/* Verify complete overwrite. */
	memmove(dest.data, zero.data, sizeof(dest.data));
	compare("complete overwrite", dest, zero);

	/* Verify middle overwrite. */
	dest = control;
	memmove(dest.data + 12, zero.data, 7);
	compare("middle overwrite", dest, middle);

	/* Verify argument side-effects aren't repeated. */
	dest = control;
	ptr = dest.data;
	count = 2;
	memmove(ptr++, zero.data, count++);
	ptr += 9;
	memmove(ptr++, zero.data, count++);
	compare("argument side-effects", dest, five);

	/* Verify overlapping overwrite is correct. */
	ptr = &overlap.data[2];
	memmove(ptr, overlap.data, 5);
	compare("overlapping write", overlap, overlap_expected);

	/* Verify larger overlapping moves. */
	larger_array[256] = 0xAAu;
	/*
	* Test a backwards overlapping memmove first. 256 and 1024 are
	* important for i386 to use rep movsl.
	*/
	memmove(larger_array, larger_array + 256, 1024);
	KUNIT_ASSERT_EQ(test, larger_array[0], 0xAAu);
	KUNIT_ASSERT_EQ(test, larger_array[256], 0x00);
	KUNIT_ASSERT_NULL(test,
	memchr(larger_array + 1, 0xaa, ARRAY_SIZE(larger_array) - 1));
	/* Test a forwards overlapping memmove. */
	larger_array[0] = 0xBBu;
	memmove(larger_array + 256, larger_array, 1024);
	KUNIT_ASSERT_EQ(test, larger_array[0], 0xBBu);
	KUNIT_ASSERT_EQ(test, larger_array[256], 0xBBu);
	KUNIT_ASSERT_NULL(test, memchr(larger_array + 1, 0xBBu, 256 - 1));
	KUNIT_ASSERT_NULL(test,
	memchr(larger_array + 257, 0xBBu, ARRAY_SIZE(larger_array) - 257));
	#undef TEST_OP
	}

	static void memset_test(struct kunit *test)
	{
	#define TEST_OP "memset"
	struct some_bytes control = {
	.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	},
	};
	struct some_bytes complete = {
	.data = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	},
	};
	struct some_bytes middle = {
	.data = { 0x30, 0x30, 0x30, 0x30, 0x31, 0x31, 0x31, 0x31,
	0x31, 0x31, 0x31, 0x31, 0x31, 0x31, 0x31, 0x31,
	0x31, 0x31, 0x31, 0x31, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	},
	};
	struct some_bytes three = {
	.data = { 0x60, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x61, 0x61, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	},
	};
	struct some_bytes after = {
	.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x72,
	0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
	0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
	0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72,
	},
	};
	struct some_bytes startat = {
	.data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
	0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
	0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
	0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
	},
	};
	struct some_bytes dest = { };
	int count, value;
	u8 *ptr;

	/* Verify static initializers. */
	check(control, 0x30);
	check(dest, 0);

	/* Verify assignment. */
	dest = control;
	compare("direct assignment", dest, control);

	/* Verify complete overwrite. */
	memset(dest.data, 0xff, sizeof(dest.data));
	compare("complete overwrite", dest, complete);

	/* Verify middle overwrite. */
	dest = control;
	memset(dest.data + 4, 0x31, 16);
	compare("middle overwrite", dest, middle);

	/* Verify argument side-effects aren't repeated. */
	dest = control;
	ptr = dest.data;
	value = 0x60;
	count = 1;
	memset(ptr++, value++, count++);
	ptr += 8;
	memset(ptr++, value++, count++);
	compare("argument side-effects", dest, three);

	/* Verify memset_after() */
	dest = control;
	memset_after(&dest, 0x72, three);
	compare("memset_after()", dest, after);

	/* Verify memset_startat() */
	dest = control;
	memset_startat(&dest, 0x79, four);
	compare("memset_startat()", dest, startat);
	#undef TEST_OP
	}

	static u8 large_src[1024];
	static u8 large_dst[2048];
	static const u8 large_zero[2048];

	static void set_random_nonzero(struct kunit test, u8 byte)
	{
	int failed_rng = 0;

	while (*byte == 0) {
	get_random_bytes(byte, 1);
	KUNIT_ASSERT_LT_MSG(test, failed_rng++, 100,
	"Is the RNG broken?");
	}
	}

	static void init_large(struct kunit *test)
	{
	/* Get many bit patterns. */
	get_random_bytes(large_src, ARRAY_SIZE(large_src));

	/* Make sure we have non-zero edges. */
	set_random_nonzero(test, &large_src[0]);
	set_random_nonzero(test, &large_src[ARRAY_SIZE(large_src) - 1]);

	/* Explicitly zero the entire destination. */
	memset(large_dst, 0, ARRAY_SIZE(large_dst));
	}

	/*
	* Instead of an indirect function call for "copy" or a giant macro,
	* use a bool to pick memcpy or memmove.
	*/
	static void copy_large_test(struct kunit *test, bool use_memmove)
	{
	init_large(test);

	/* Copy a growing number of non-overlapping bytes ... */
	for (int bytes = 1; bytes <= ARRAY_SIZE(large_src); bytes++) {
	/* Over a shifting destination window ... */
	for (int offset = 0; offset < ARRAY_SIZE(large_src); offset++) {
	int right_zero_pos = offset + bytes;
	int right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

	/* Copy! */
	if (use_memmove)
	memmove(large_dst + offset, large_src, bytes);
	else
	memcpy(large_dst + offset, large_src, bytes);

	/* Did we touch anything before the copy area? */
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(large_dst, large_zero, offset), 0,
	"with size %d at offset %d", bytes, offset);
	/* Did we touch anything after the copy area? */
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(&large_dst[right_zero_pos], large_zero, right_zero_size), 0,
	"with size %d at offset %d", bytes, offset);

	/* Are we byte-for-byte exact across the copy? */
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(large_dst + offset, large_src, bytes), 0,
	"with size %d at offset %d", bytes, offset);

	/* Zero out what we copied for the next cycle. */
	memset(large_dst + offset, 0, bytes);
	}
	/* Avoid stall warnings if this loop gets slow. */
	cond_resched();
	}
	}

	static void memcpy_large_test(struct kunit *test)
	{
	copy_large_test(test, false);
	}

	static void memmove_large_test(struct kunit *test)
	{
	copy_large_test(test, true);
	}

	/*
	* On the assumption that boundary conditions are going to be the most
	* sensitive, instead of taking a full step (inc) each iteration,
	* take single index steps for at least the first "inc"-many indexes
	* from the "start" and at least the last "inc"-many indexes before
	* the "end". When in the middle, take full "inc"-wide steps. For
	* example, calling next_step(idx, 1, 15, 3) with idx starting at 0
	* would see the following pattern: 1 2 3 4 7 10 11 12 13 14 15.
	*/
	static int next_step(int idx, int start, int end, int inc)
	{
	start += inc;
	end -= inc;

	if (idx < start \|\| idx + inc > end)
	inc = 1;
	return idx + inc;
	}

	static void inner_loop(struct kunit *test, int bytes, int d_off, int s_off)
	{
	int left_zero_pos, left_zero_size;
	int right_zero_pos, right_zero_size;
	int src_pos, src_orig_pos, src_size;
	int pos;

	/* Place the source in the destination buffer. */
	memcpy(&large_dst[s_off], large_src, bytes);

	/* Copy to destination offset. */
	memmove(&large_dst[d_off], &large_dst[s_off], bytes);

	/* Make sure destination entirely matches. */
	KUNIT_ASSERT_EQ_MSG(test, memcmp(&large_dst[d_off], large_src, bytes), 0,
	"with size %d at src offset %d and dest offset %d",
	bytes, s_off, d_off);

	/* Calculate the expected zero spans. */
	if (s_off < d_off) {
	left_zero_pos = 0;
	left_zero_size = s_off;

	right_zero_pos = d_off + bytes;
	right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

	src_pos = s_off;
	src_orig_pos = 0;
	src_size = d_off - s_off;
	} else {
	left_zero_pos = 0;
	left_zero_size = d_off;

	right_zero_pos = s_off + bytes;
	right_zero_size = ARRAY_SIZE(large_dst) - right_zero_pos;

	src_pos = d_off + bytes;
	src_orig_pos = src_pos - s_off;
	src_size = right_zero_pos - src_pos;
	}

	/* Check non-overlapping source is unchanged.*/
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(&large_dst[src_pos], &large_src[src_orig_pos], src_size), 0,
	"with size %d at src offset %d and dest offset %d",
	bytes, s_off, d_off);

	/* Check leading buffer contents are zero. */
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(&large_dst[left_zero_pos], large_zero, left_zero_size), 0,
	"with size %d at src offset %d and dest offset %d",
	bytes, s_off, d_off);
	/* Check trailing buffer contents are zero. */
	KUNIT_ASSERT_EQ_MSG(test,
	memcmp(&large_dst[right_zero_pos], large_zero, right_zero_size), 0,
	"with size %d at src offset %d and dest offset %d",
	bytes, s_off, d_off);

	/* Zero out everything not already zeroed.*/
	pos = left_zero_pos + left_zero_size;
	memset(&large_dst[pos], 0, right_zero_pos - pos);
	}

	static void memmove_overlap_test(struct kunit *test)
	{
	/*
	* Running all possible offset and overlap combinations takes a
	* very long time. Instead, only check up to 128 bytes offset
	* into the destination buffer (which should result in crossing
	* cachelines), with a step size of 1 through 7 to try to skip some
	* redundancy.
	*/
	static const int offset_max = 128; /* less than ARRAY_SIZE(large_src); */
	static const int bytes_step = 7;
	static const int window_step = 7;

	static const int bytes_start = 1;
	static const int bytes_end = ARRAY_SIZE(large_src) + 1;

	init_large(test);

	/* Copy a growing number of overlapping bytes ... */
	for (int bytes = bytes_start; bytes < bytes_end;
	bytes = next_step(bytes, bytes_start, bytes_end, bytes_step)) {

	/* Over a shifting destination window ... */
	for (int d_off = 0; d_off < offset_max; d_off++) {
	int s_start = max(d_off - bytes, 0);
	int s_end = min_t(int, d_off + bytes, ARRAY_SIZE(large_src));

	/* Over a shifting source window ... */
	for (int s_off = s_start; s_off < s_end;
	s_off = next_step(s_off, s_start, s_end, window_step))
	inner_loop(test, bytes, d_off, s_off);

	/* Avoid stall warnings. */
	cond_resched();
	}
	}
	}

	static struct kunit_case memcpy_test_cases[] = {
	KUNIT_CASE(memset_test),
	KUNIT_CASE(memcpy_test),
	KUNIT_CASE_SLOW(memcpy_large_test),
	KUNIT_CASE_SLOW(memmove_test),
	KUNIT_CASE_SLOW(memmove_large_test),
	KUNIT_CASE_SLOW(memmove_overlap_test),
	{}
	};

	static struct kunit_suite memcpy_test_suite = {
	.name = "memcpy",
	.test_cases = memcpy_test_cases,
	};

	kunit_test_suite(memcpy_test_suite);

	MODULE_DESCRIPTION("test cases for memcpy(), memmove(), and memset()");
	MODULE_LICENSE("GPL");