ffs_kunit.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * KUnit tests for ffs()-family functions
  4 */
  5#include <kunit/test.h>
  6#include <linux/bitops.h>
  7
  8/*
  9 * Test data structures
 10 */
 11struct ffs_test_case {
 12	unsigned long input;
 13	int expected_ffs;	/* ffs() result (1-based) */
 14	int expected_fls;	/* fls() result (1-based) */
 15	const char *description;
 16};
 17
 18struct ffs64_test_case {
 19	u64 input;
 20	int expected_fls64;		    /* fls64() result (1-based) */
 21	unsigned int expected_ffs64_0based; /* __ffs64() result (0-based) */
 22	const char *description;
 23};
 24
 25/*
 26 * Basic edge cases - core functionality validation
 27 */
 28static const struct ffs_test_case basic_test_cases[] = {
 29	/* Zero case - special handling */
 30	{0x00000000, 0, 0, "zero value"},
 31
 32	/* Single bit patterns - powers of 2 */
 33	{0x00000001, 1, 1, "bit 0 set"},
 34	{0x00000002, 2, 2, "bit 1 set"},
 35	{0x00000004, 3, 3, "bit 2 set"},
 36	{0x00000008, 4, 4, "bit 3 set"},
 37	{0x00000010, 5, 5, "bit 4 set"},
 38	{0x00000020, 6, 6, "bit 5 set"},
 39	{0x00000040, 7, 7, "bit 6 set"},
 40	{0x00000080, 8, 8, "bit 7 set"},
 41	{0x00000100, 9, 9, "bit 8 set"},
 42	{0x00008000, 16, 16, "bit 15 set"},
 43	{0x00010000, 17, 17, "bit 16 set"},
 44	{0x40000000, 31, 31, "bit 30 set"},
 45	{0x80000000, 32, 32, "bit 31 set (sign bit)"},
 46
 47	/* Maximum values */
 48	{0xFFFFFFFF, 1, 32, "all bits set"},
 49
 50	/* Multiple bit patterns */
 51	{0x00000003, 1, 2, "bits 0-1 set"},
 52	{0x00000007, 1, 3, "bits 0-2 set"},
 53	{0x0000000F, 1, 4, "bits 0-3 set"},
 54	{0x000000FF, 1, 8, "bits 0-7 set"},
 55	{0x0000FFFF, 1, 16, "bits 0-15 set"},
 56	{0x7FFFFFFF, 1, 31, "bits 0-30 set"},
 57
 58	/* Sparse patterns */
 59	{0x00000101, 1, 9, "bits 0,8 set"},
 60	{0x00001001, 1, 13, "bits 0,12 set"},
 61	{0x80000001, 1, 32, "bits 0,31 set"},
 62	{0x40000002, 2, 31, "bits 1,30 set"},
 63};
 64
 65/*
 66 * 64-bit test cases
 67 */
 68static const struct ffs64_test_case ffs64_test_cases[] = {
 69	/* Zero case */
 70	{0x0000000000000000ULL, 0, 0, "zero value"},
 71
 72	/* Single bit patterns */
 73	{0x0000000000000001ULL, 1, 0, "bit 0 set"},
 74	{0x0000000000000002ULL, 2, 1, "bit 1 set"},
 75	{0x0000000000000004ULL, 3, 2, "bit 2 set"},
 76	{0x0000000000000008ULL, 4, 3, "bit 3 set"},
 77	{0x0000000000008000ULL, 16, 15, "bit 15 set"},
 78	{0x0000000000010000ULL, 17, 16, "bit 16 set"},
 79	{0x0000000080000000ULL, 32, 31, "bit 31 set"},
 80	{0x0000000100000000ULL, 33, 32, "bit 32 set"},
 81	{0x0000000200000000ULL, 34, 33, "bit 33 set"},
 82	{0x4000000000000000ULL, 63, 62, "bit 62 set"},
 83	{0x8000000000000000ULL, 64, 63, "bit 63 set (sign bit)"},
 84
 85	/* Maximum values */
 86	{0xFFFFFFFFFFFFFFFFULL, 64, 0, "all bits set"},
 87
 88	/* Cross 32-bit boundary patterns */
 89	{0x00000000FFFFFFFFULL, 32, 0, "lower 32 bits set"},
 90	{0xFFFFFFFF00000000ULL, 64, 32, "upper 32 bits set"},
 91	{0x8000000000000001ULL, 64, 0, "bits 0,63 set"},
 92	{0x4000000000000002ULL, 63, 1, "bits 1,62 set"},
 93
 94	/* Mixed patterns */
 95	{0x00000001FFFFFFFFULL, 33, 0, "bit 32 + lower 32 bits"},
 96	{0xFFFFFFFF80000000ULL, 64, 31, "upper 32 bits + bit 31"},
 97};
 98
 99/*
100 * Helper function to validate ffs results with detailed error messages
101 */
102static void validate_ffs_result(struct kunit *test, unsigned long input,
103				int actual, int expected, const char *func_name,
104				const char *description)
105{
106	KUNIT_EXPECT_EQ_MSG(test, actual, expected,
107			    "%s(0x%08lx) [%s]: expected %d, got %d",
108			    func_name, input, description, expected, actual);
109}
110
111/*
112 * Helper function to validate 64-bit ffs results
113 */
114static void validate_ffs64_result(struct kunit *test, u64 input,
115				  int actual, int expected, const char *func_name,
116				  const char *description)
117{
118	KUNIT_EXPECT_EQ_MSG(test, actual, expected,
119			    "%s(0x%016llx) [%s]: expected %d, got %d",
120			    func_name, input, description, expected, actual);
121}
122
123/*
124 * Helper function to validate mathematical relationships between functions
125 */
126static void validate_ffs_relationships(struct kunit *test, unsigned long input)
127{
128	int ffs_result;
129	int fls_result;
130	unsigned int ffs_0based;
131	unsigned int fls_0based;
132
133	if (input == 0) {
134		/* Special case: zero input */
135		KUNIT_EXPECT_EQ(test, ffs(input), 0);
136		KUNIT_EXPECT_EQ(test, fls(input), 0);
137		/* __ffs and __fls are undefined for 0, but often return specific values */
138		return;
139	}
140
141	ffs_result = ffs(input);
142	fls_result = fls(input);
143	ffs_0based = __ffs(input);
144	fls_0based = __fls(input);
145
146	/* Relationship: ffs(x) == __ffs(x) + 1 for x != 0 */
147	KUNIT_EXPECT_EQ_MSG(test, ffs_result, ffs_0based + 1,
148			    "ffs(0x%08lx) != __ffs(0x%08lx) + 1: %d != %u + 1",
149			    input, input, ffs_result, ffs_0based);
150
151	/* Relationship: fls(x) == __fls(x) + 1 for x != 0 */
152	KUNIT_EXPECT_EQ_MSG(test, fls_result, fls_0based + 1,
153			    "fls(0x%08lx) != __fls(0x%08lx) + 1: %d != %u + 1",
154			    input, input, fls_result, fls_0based);
155
156	/* Range validation */
157	KUNIT_EXPECT_GE(test, ffs_result, 1);
158	KUNIT_EXPECT_LE(test, ffs_result, BITS_PER_LONG);
159	KUNIT_EXPECT_GE(test, fls_result, 1);
160	KUNIT_EXPECT_LE(test, fls_result, BITS_PER_LONG);
161}
162
163/*
164 * Helper function to validate 64-bit relationships
165 */
166static void validate_ffs64_relationships(struct kunit *test, u64 input)
167{
168	int fls64_result;
169	unsigned int ffs64_0based;
170
171	if (input == 0) {
172		KUNIT_EXPECT_EQ(test, fls64(input), 0);
173		return;
174	}
175
176	fls64_result = fls64(input);
177	ffs64_0based = __ffs64(input);
178
179	/* Range validation */
180	KUNIT_EXPECT_GE(test, fls64_result, 1);
181	KUNIT_EXPECT_LE(test, fls64_result, 64);
182	KUNIT_EXPECT_LT(test, ffs64_0based, 64);
183
184	/*
185	 * Relationships with 32-bit functions should hold for small values
186	 * on all architectures.
187	 */
188	if (input <= 0xFFFFFFFFULL) {
189		unsigned long input_32 = (unsigned long)input;
190		KUNIT_EXPECT_EQ_MSG(test, fls64(input), fls(input_32),
191				    "fls64(0x%llx) != fls(0x%lx): %d != %d",
192				    input, input_32, fls64(input), fls(input_32));
193
194		if (input != 0) {
195			KUNIT_EXPECT_EQ_MSG(test, __ffs64(input), __ffs(input_32),
196					    "__ffs64(0x%llx) != __ffs(0x%lx): %lu != %lu",
197					    input, input_32,
198					    (unsigned long)__ffs64(input),
199					    (unsigned long)__ffs(input_32));
200		}
201	}
202}
203
204/*
205 * Test basic correctness of all ffs-family functions
206 */
207static void ffs_basic_correctness_test(struct kunit *test)
208{
209	int i;
210
211	for (i = 0; i < ARRAY_SIZE(basic_test_cases); i++) {
212		const struct ffs_test_case *tc = &basic_test_cases[i];
213
214		/* Test ffs() */
215		validate_ffs_result(test, tc->input, ffs(tc->input),
216				    tc->expected_ffs, "ffs", tc->description);
217
218		/* Test fls() */
219		validate_ffs_result(test, tc->input, fls(tc->input),
220				    tc->expected_fls, "fls", tc->description);
221
222		/* Test __ffs() - skip zero case as it's undefined */
223		if (tc->input != 0) {
224			/* Calculate expected __ffs() result: __ffs(x) == ffs(x) - 1 */
225			unsigned int expected_ffs_0based = tc->expected_ffs - 1;
226			validate_ffs_result(test, tc->input, __ffs(tc->input),
227					    expected_ffs_0based, "__ffs", tc->description);
228		}
229
230		/* Test __fls() - skip zero case as it's undefined */
231		if (tc->input != 0) {
232			/* Calculate expected __fls() result: __fls(x) == fls(x) - 1 */
233			unsigned int expected_fls_0based = tc->expected_fls - 1;
234			validate_ffs_result(test, tc->input, __fls(tc->input),
235					    expected_fls_0based, "__fls", tc->description);
236		}
237	}
238}
239
240/*
241 * Test 64-bit function correctness
242 */
243static void ffs64_correctness_test(struct kunit *test)
244{
245	int i;
246
247	for (i = 0; i < ARRAY_SIZE(ffs64_test_cases); i++) {
248		const struct ffs64_test_case *tc = &ffs64_test_cases[i];
249
250		/* Test fls64() */
251		validate_ffs64_result(test, tc->input, fls64(tc->input),
252				      tc->expected_fls64, "fls64", tc->description);
253
254		/* Test __ffs64() - skip zero case as it's undefined */
255		if (tc->input != 0) {
256			validate_ffs64_result(test, tc->input, __ffs64(tc->input),
257					      tc->expected_ffs64_0based, "__ffs64",
258					      tc->description);
259		}
260	}
261}
262
263/*
264 * Test mathematical relationships between functions
265 */
266static void ffs_mathematical_relationships_test(struct kunit *test)
267{
268	int i;
269
270	/* Test basic cases */
271	for (i = 0; i < ARRAY_SIZE(basic_test_cases); i++) {
272		validate_ffs_relationships(test, basic_test_cases[i].input);
273	}
274
275	/* Test 64-bit cases */
276	for (i = 0; i < ARRAY_SIZE(ffs64_test_cases); i++) {
277		validate_ffs64_relationships(test, ffs64_test_cases[i].input);
278	}
279}
280
281/*
282 * Test edge cases and boundary conditions
283 */
284static void ffs_edge_cases_test(struct kunit *test)
285{
286	unsigned long test_patterns[] = {
287		/* Powers of 2 */
288		1UL, 2UL, 4UL, 8UL, 16UL, 32UL, 64UL, 128UL,
289		256UL, 512UL, 1024UL, 2048UL, 4096UL, 8192UL,
290
291		/* Powers of 2 minus 1 */
292		1UL, 3UL, 7UL, 15UL, 31UL, 63UL, 127UL, 255UL,
293		511UL, 1023UL, 2047UL, 4095UL, 8191UL,
294
295		/* Boundary values */
296		0x7FFFFFFFUL,	/* Maximum positive 32-bit */
297		0x80000000UL,	/* Minimum negative 32-bit */
298		0xFFFFFFFFUL,	/* Maximum 32-bit unsigned */
299	};
300	int i;
301
302	for (i = 0; i < ARRAY_SIZE(test_patterns); i++) {
303		validate_ffs_relationships(test, test_patterns[i]);
304	}
305}
306
307/*
308 * Test 64-bit edge cases
309 */
310static void ffs64_edge_cases_test(struct kunit *test)
311{
312	u64 test_patterns_64[] = {
313		/* 64-bit powers of 2 */
314		0x0000000100000000ULL,	/* 2^32 */
315		0x0000000200000000ULL,	/* 2^33 */
316		0x0000000400000000ULL,	/* 2^34 */
317		0x0000001000000000ULL,	/* 2^36 */
318		0x0000010000000000ULL,	/* 2^40 */
319		0x0001000000000000ULL,	/* 2^48 */
320		0x0100000000000000ULL,	/* 2^56 */
321		0x4000000000000000ULL,	/* 2^62 */
322		0x8000000000000000ULL,	/* 2^63 */
323
324		/* Cross-boundary patterns */
325		0x00000000FFFFFFFFULL,	/* Lower 32 bits */
326		0xFFFFFFFF00000000ULL,	/* Upper 32 bits */
327		0x7FFFFFFFFFFFFFFFULL,	/* Maximum positive 64-bit */
328		0xFFFFFFFFFFFFFFFFULL,	/* Maximum 64-bit unsigned */
329	};
330	int i;
331
332	for (i = 0; i < ARRAY_SIZE(test_patterns_64); i++) {
333		validate_ffs64_relationships(test, test_patterns_64[i]);
334	}
335}
336
337/*
338 * ffz() test data - Find First Zero bit test cases
339 */
340struct ffz_test_case {
341	unsigned long input;
342	unsigned long expected_ffz;
343	const char *description;
344};
345
346static const struct ffz_test_case ffz_test_cases[] = {
347	/* Zero bits in specific positions */
348	{0xFFFFFFFE, 0, "bit 0 is zero"},      /* ...11111110 */
349	{0xFFFFFFFD, 1, "bit 1 is zero"},      /* ...11111101 */
350	{0xFFFFFFFB, 2, "bit 2 is zero"},      /* ...11111011 */
351	{0xFFFFFFF7, 3, "bit 3 is zero"},      /* ...11110111 */
352	{0xFFFFFFEF, 4, "bit 4 is zero"},      /* ...11101111 */
353	{0xFFFFFFDF, 5, "bit 5 is zero"},      /* ...11011111 */
354	{0xFFFFFFBF, 6, "bit 6 is zero"},      /* ...10111111 */
355	{0xFFFFFF7F, 7, "bit 7 is zero"},      /* ...01111111 */
356	{0xFFFFFEFF, 8, "bit 8 is zero"},      /* Gap in bit 8 */
357	{0xFFFF7FFF, 15, "bit 15 is zero"},    /* Gap in bit 15 */
358	{0xFFFEFFFF, 16, "bit 16 is zero"},    /* Gap in bit 16 */
359	{0xBFFFFFFF, 30, "bit 30 is zero"},    /* Gap in bit 30 */
360	{0x7FFFFFFF, 31, "bit 31 is zero"},    /* 01111111... */
361
362	/* Multiple zero patterns */
363	{0xFFFFFFFC, 0, "bits 0-1 are zero"},  /* ...11111100 */
364	{0xFFFFFFF8, 0, "bits 0-2 are zero"},  /* ...11111000 */
365	{0xFFFFFFF0, 0, "bits 0-3 are zero"},  /* ...11110000 */
366	{0xFFFFFF00, 0, "bits 0-7 are zero"},  /* ...00000000 */
367	{0xFFFF0000, 0, "bits 0-15 are zero"}, /* Lower 16 bits zero */
368
369	/* All zeros (special case) */
370	{0x00000000, 0, "all bits zero"},
371
372	/* Complex patterns */
373	{0xFFFDFFFF, 17, "bit 17 is zero"},    /* Gap in bit 17 */
374	{0xFFF7FFFF, 19, "bit 19 is zero"},    /* Gap in bit 19 */
375	{0xF7FFFFFF, 27, "bit 27 is zero"},    /* Gap in bit 27 */
376	{0xDFFFFFFF, 29, "bit 29 is zero"},    /* Gap in bit 29 */
377};
378
379/*
380 * Test basic correctness of ffz() function
381 */
382static void ffz_basic_correctness_test(struct kunit *test)
383{
384	int i;
385
386	for (i = 0; i < ARRAY_SIZE(ffz_test_cases); i++) {
387		const struct ffz_test_case *tc = &ffz_test_cases[i];
388		unsigned long result = ffz(tc->input);
389
390		KUNIT_EXPECT_EQ_MSG(test, result, tc->expected_ffz,
391				    "ffz(0x%08lx) [%s]: expected %lu, got %lu",
392				    tc->input, tc->description, tc->expected_ffz, result);
393	}
394}
395
396/*
397 * Test mathematical relationships between ffz() and other functions
398 */
399static void validate_ffz_relationships(struct kunit *test, unsigned long input)
400{
401	unsigned long ffz_result;
402
403	if (input == 0) {
404		/* ffz(0) should return 0 (first zero bit is at position 0) */
405		KUNIT_EXPECT_EQ(test, ffz(input), 0);
406		return;
407	}
408
409	if (input == ~0UL) {
410		/* ffz(~0) is undefined (no zero bits) - just verify it doesn't crash */
411		ffz_result = ffz(input);
412		/* Implementation-defined behavior, just ensure it completes */
413		return;
414	}
415
416	ffz_result = ffz(input);
417
418	/* Range validation - result should be within valid bit range */
419	KUNIT_EXPECT_LT(test, ffz_result, BITS_PER_LONG);
420
421	/* Verify the bit at ffz_result position is actually zero */
422	KUNIT_EXPECT_EQ_MSG(test, (input >> ffz_result) & 1, 0,
423			    "ffz(0x%08lx) = %lu, but bit %lu is not zero",
424			    input, ffz_result, ffz_result);
425
426	/* Core relationship: if we set the ffz bit, ffz should find a different bit */
427	if (ffz_result < BITS_PER_LONG - 1) {
428		unsigned long modified = input | (1UL << ffz_result);
429		if (modified != ~0UL) { /* Skip if all bits would be set */
430			unsigned long new_ffz = ffz(modified);
431			KUNIT_EXPECT_NE_MSG(test, new_ffz, ffz_result,
432					    "ffz(0x%08lx) = %lu, but setting that bit doesn't change ffz result",
433					    input, ffz_result);
434		}
435	}
436}
437
438static void ffz_mathematical_relationships_test(struct kunit *test)
439{
440	unsigned long test_patterns[] = {
441		/* Powers of 2 with one bit clear */
442		0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFB, 0xFFFFFFF7,
443		0xFFFFFFEF, 0xFFFFFFDF, 0xFFFFFFBF, 0xFFFFFF7F,
444
445		/* Multiple patterns */
446		0xFFFFFF00, 0xFFFFF000, 0xFFFF0000, 0xFFF00000,
447		0x7FFFFFFF, 0x3FFFFFFF, 0x1FFFFFFF, 0x0FFFFFFF,
448
449		/* Complex bit patterns */
450		0xAAAAAAAA, 0x55555555, 0xCCCCCCCC, 0x33333333,
451		0xF0F0F0F0, 0x0F0F0F0F, 0xFF00FF00, 0x00FF00FF,
452	};
453	int i;
454
455	/* Test basic test cases */
456	for (i = 0; i < ARRAY_SIZE(ffz_test_cases); i++) {
457		validate_ffz_relationships(test, ffz_test_cases[i].input);
458	}
459
460	/* Test additional patterns */
461	for (i = 0; i < ARRAY_SIZE(test_patterns); i++) {
462		validate_ffz_relationships(test, test_patterns[i]);
463	}
464}
465
466/*
467 * Test edge cases and boundary conditions for ffz()
468 */
469static void ffz_edge_cases_test(struct kunit *test)
470{
471	unsigned long edge_patterns[] = {
472		/* Boundary values */
473		0x00000000,  /* All zeros */
474		0x80000000,  /* Only MSB set */
475		0x00000001,  /* Only LSB set */
476		0x7FFFFFFF,  /* MSB clear */
477		0xFFFFFFFE,  /* LSB clear */
478
479		/* Powers of 2 complement patterns (one zero bit each) */
480		~(1UL << 0),  ~(1UL << 1),  ~(1UL << 2),  ~(1UL << 3),
481		~(1UL << 4),  ~(1UL << 8),  ~(1UL << 16), ~(1UL << 31),
482
483		/* Walking zero patterns */
484		0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFB, 0xFFFFFFF7,
485		0xFFFFFFEF, 0xFFFFFFDF, 0xFFFFFFBF, 0xFFFFFF7F,
486		0xFFFFFEFF, 0xFFFFFDFF, 0xFFFFFBFF, 0xFFFFF7FF,
487
488		/* Multiple zeros */
489		0xFFFFFF00, 0xFFFFF000, 0xFFFF0000, 0xFFF00000,
490		0xFF000000, 0xF0000000, 0x00000000,
491	};
492	int i;
493
494	for (i = 0; i < ARRAY_SIZE(edge_patterns); i++) {
495		validate_ffz_relationships(test, edge_patterns[i]);
496	}
497}
498
499/*
500 * To have useful build error output, split the tests into separate
501 * functions so it's clear which are missing __attribute_const__.
502 */
503#define CREATE_WRAPPER(func)						\
504static noinline bool build_test_##func(void)				\
505{									\
506	int init_##func = 32;						\
507	int result_##func = func(6);					\
508									\
509	/* Does the static initializer vanish after calling func? */	\
510	BUILD_BUG_ON(init_##func < 32);					\
511									\
512	/* "Consume" the results so optimizer doesn't drop them. */	\
513	barrier_data(&init_##func);					\
514	barrier_data(&result_##func);					\
515									\
516	return true;							\
517}
518CREATE_WRAPPER(ffs)
519CREATE_WRAPPER(fls)
520CREATE_WRAPPER(__ffs)
521CREATE_WRAPPER(__fls)
522CREATE_WRAPPER(ffz)
523#undef CREATE_WRAPPER
524
525/*
526 * Make sure that __attribute_const__ has be applied to all the
527 * functions. This is a regression test for:
528 * https://github.com/KSPP/linux/issues/364
529 */
530static void ffs_attribute_const_test(struct kunit *test)
531{
532	KUNIT_EXPECT_TRUE(test, build_test_ffs());
533	KUNIT_EXPECT_TRUE(test, build_test_fls());
534	KUNIT_EXPECT_TRUE(test, build_test___ffs());
535	KUNIT_EXPECT_TRUE(test, build_test___fls());
536	KUNIT_EXPECT_TRUE(test, build_test_ffz());
537}
538
539/*
540 * KUnit test case definitions
541 */
542static struct kunit_case ffs_test_cases[] = {
543	KUNIT_CASE(ffs_basic_correctness_test),
544	KUNIT_CASE(ffs64_correctness_test),
545	KUNIT_CASE(ffs_mathematical_relationships_test),
546	KUNIT_CASE(ffs_edge_cases_test),
547	KUNIT_CASE(ffs64_edge_cases_test),
548	KUNIT_CASE(ffz_basic_correctness_test),
549	KUNIT_CASE(ffz_mathematical_relationships_test),
550	KUNIT_CASE(ffz_edge_cases_test),
551	KUNIT_CASE(ffs_attribute_const_test),
552	{}
553};
554
555/*
556 * KUnit test suite definition
557 */
558static struct kunit_suite ffs_test_suite = {
559	.name = "ffs",
560	.test_cases = ffs_test_cases,
561};
562
563kunit_test_suites(&ffs_test_suite);
564
565MODULE_DESCRIPTION("KUnit tests for ffs()-family functions");
566MODULE_LICENSE("GPL");