Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 566 insertions, 0 deletions

diff --git a/lib/tests/ffs_kunit.c b/lib/tests/ffs_kunit.c
new file mode 100644
index 000000000..9a329cdc0
--- /dev/null
+++ b/lib/tests/ffs_kunit.c
@@ -0,0 +1,566 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for ffs()-family functions
+ */
+#include <kunit/test.h>
+#include <linux/bitops.h>
+
+/*
+ * Test data structures
+ */
+struct ffs_test_case {
+	unsigned long input;
+	int expected_ffs;	/* ffs() result (1-based) */
+	int expected_fls;	/* fls() result (1-based) */
+	const char *description;
+};
+
+struct ffs64_test_case {
+	u64 input;
+	int expected_fls64;		    /* fls64() result (1-based) */
+	unsigned int expected_ffs64_0based; /* __ffs64() result (0-based) */
+	const char *description;
+};
+
+/*
+ * Basic edge cases - core functionality validation
+ */
+static const struct ffs_test_case basic_test_cases[] = {
+	/* Zero case - special handling */
+	{0x00000000, 0, 0, "zero value"},
+
+	/* Single bit patterns - powers of 2 */
+	{0x00000001, 1, 1, "bit 0 set"},
+	{0x00000002, 2, 2, "bit 1 set"},
+	{0x00000004, 3, 3, "bit 2 set"},
+	{0x00000008, 4, 4, "bit 3 set"},
+	{0x00000010, 5, 5, "bit 4 set"},
+	{0x00000020, 6, 6, "bit 5 set"},
+	{0x00000040, 7, 7, "bit 6 set"},
+	{0x00000080, 8, 8, "bit 7 set"},
+	{0x00000100, 9, 9, "bit 8 set"},
+	{0x00008000, 16, 16, "bit 15 set"},
+	{0x00010000, 17, 17, "bit 16 set"},
+	{0x40000000, 31, 31, "bit 30 set"},
+	{0x80000000, 32, 32, "bit 31 set (sign bit)"},
+
+	/* Maximum values */
+	{0xFFFFFFFF, 1, 32, "all bits set"},
+
+	/* Multiple bit patterns */
+	{0x00000003, 1, 2, "bits 0-1 set"},
+	{0x00000007, 1, 3, "bits 0-2 set"},
+	{0x0000000F, 1, 4, "bits 0-3 set"},
+	{0x000000FF, 1, 8, "bits 0-7 set"},
+	{0x0000FFFF, 1, 16, "bits 0-15 set"},
+	{0x7FFFFFFF, 1, 31, "bits 0-30 set"},
+
+	/* Sparse patterns */
+	{0x00000101, 1, 9, "bits 0,8 set"},
+	{0x00001001, 1, 13, "bits 0,12 set"},
+	{0x80000001, 1, 32, "bits 0,31 set"},
+	{0x40000002, 2, 31, "bits 1,30 set"},
+};
+
+/*
+ * 64-bit test cases
+ */
+static const struct ffs64_test_case ffs64_test_cases[] = {
+	/* Zero case */
+	{0x0000000000000000ULL, 0, 0, "zero value"},
+
+	/* Single bit patterns */
+	{0x0000000000000001ULL, 1, 0, "bit 0 set"},
+	{0x0000000000000002ULL, 2, 1, "bit 1 set"},
+	{0x0000000000000004ULL, 3, 2, "bit 2 set"},
+	{0x0000000000000008ULL, 4, 3, "bit 3 set"},
+	{0x0000000000008000ULL, 16, 15, "bit 15 set"},
+	{0x0000000000010000ULL, 17, 16, "bit 16 set"},
+	{0x0000000080000000ULL, 32, 31, "bit 31 set"},
+	{0x0000000100000000ULL, 33, 32, "bit 32 set"},
+	{0x0000000200000000ULL, 34, 33, "bit 33 set"},
+	{0x4000000000000000ULL, 63, 62, "bit 62 set"},
+	{0x8000000000000000ULL, 64, 63, "bit 63 set (sign bit)"},
+
+	/* Maximum values */
+	{0xFFFFFFFFFFFFFFFFULL, 64, 0, "all bits set"},
+
+	/* Cross 32-bit boundary patterns */
+	{0x00000000FFFFFFFFULL, 32, 0, "lower 32 bits set"},
+	{0xFFFFFFFF00000000ULL, 64, 32, "upper 32 bits set"},
+	{0x8000000000000001ULL, 64, 0, "bits 0,63 set"},
+	{0x4000000000000002ULL, 63, 1, "bits 1,62 set"},
+
+	/* Mixed patterns */
+	{0x00000001FFFFFFFFULL, 33, 0, "bit 32 + lower 32 bits"},
+	{0xFFFFFFFF80000000ULL, 64, 31, "upper 32 bits + bit 31"},
+};
+
+/*
+ * Helper function to validate ffs results with detailed error messages
+ */
+static void validate_ffs_result(struct kunit *test, unsigned long input,
+				int actual, int expected, const char *func_name,
+				const char *description)
+{
+	KUNIT_EXPECT_EQ_MSG(test, actual, expected,
+			    "%s(0x%08lx) [%s]: expected %d, got %d",
+			    func_name, input, description, expected, actual);
+}
+
+/*
+ * Helper function to validate 64-bit ffs results
+ */
+static void validate_ffs64_result(struct kunit *test, u64 input,
+				  int actual, int expected, const char *func_name,
+				  const char *description)
+{
+	KUNIT_EXPECT_EQ_MSG(test, actual, expected,
+			    "%s(0x%016llx) [%s]: expected %d, got %d",
+			    func_name, input, description, expected, actual);
+}
+
+/*
+ * Helper function to validate mathematical relationships between functions
+ */
+static void validate_ffs_relationships(struct kunit *test, unsigned long input)
+{
+	int ffs_result;
+	int fls_result;
+	unsigned int ffs_0based;
+	unsigned int fls_0based;
+
+	if (input == 0) {
+		/* Special case: zero input */
+		KUNIT_EXPECT_EQ(test, ffs(input), 0);
+		KUNIT_EXPECT_EQ(test, fls(input), 0);
+		/* __ffs and __fls are undefined for 0, but often return specific values */
+		return;
+	}
+
+	ffs_result = ffs(input);
+	fls_result = fls(input);
+	ffs_0based = __ffs(input);
+	fls_0based = __fls(input);
+
+	/* Relationship: ffs(x) == __ffs(x) + 1 for x != 0 */
+	KUNIT_EXPECT_EQ_MSG(test, ffs_result, ffs_0based + 1,
+			    "ffs(0x%08lx) != __ffs(0x%08lx) + 1: %d != %u + 1",
+			    input, input, ffs_result, ffs_0based);
+
+	/* Relationship: fls(x) == __fls(x) + 1 for x != 0 */
+	KUNIT_EXPECT_EQ_MSG(test, fls_result, fls_0based + 1,
+			    "fls(0x%08lx) != __fls(0x%08lx) + 1: %d != %u + 1",
+			    input, input, fls_result, fls_0based);
+
+	/* Range validation */
+	KUNIT_EXPECT_GE(test, ffs_result, 1);
+	KUNIT_EXPECT_LE(test, ffs_result, BITS_PER_LONG);
+	KUNIT_EXPECT_GE(test, fls_result, 1);
+	KUNIT_EXPECT_LE(test, fls_result, BITS_PER_LONG);
+}
+
+/*
+ * Helper function to validate 64-bit relationships
+ */
+static void validate_ffs64_relationships(struct kunit *test, u64 input)
+{
+	int fls64_result;
+	unsigned int ffs64_0based;
+
+	if (input == 0) {
+		KUNIT_EXPECT_EQ(test, fls64(input), 0);
+		return;
+	}
+
+	fls64_result = fls64(input);
+	ffs64_0based = __ffs64(input);
+
+	/* Range validation */
+	KUNIT_EXPECT_GE(test, fls64_result, 1);
+	KUNIT_EXPECT_LE(test, fls64_result, 64);
+	KUNIT_EXPECT_LT(test, ffs64_0based, 64);
+
+	/*
+	 * Relationships with 32-bit functions should hold for small values
+	 * on all architectures.
+	 */
+	if (input <= 0xFFFFFFFFULL) {
+		unsigned long input_32 = (unsigned long)input;
+		KUNIT_EXPECT_EQ_MSG(test, fls64(input), fls(input_32),
+				    "fls64(0x%llx) != fls(0x%lx): %d != %d",
+				    input, input_32, fls64(input), fls(input_32));
+
+		if (input != 0) {
+			KUNIT_EXPECT_EQ_MSG(test, __ffs64(input), __ffs(input_32),
+					    "__ffs64(0x%llx) != __ffs(0x%lx): %lu != %lu",
+					    input, input_32,
+					    (unsigned long)__ffs64(input),
+					    (unsigned long)__ffs(input_32));
+		}
+	}
+}
+
+/*
+ * Test basic correctness of all ffs-family functions
+ */
+static void ffs_basic_correctness_test(struct kunit *test)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(basic_test_cases); i++) {
+		const struct ffs_test_case *tc = &basic_test_cases[i];
+
+		/* Test ffs() */
+		validate_ffs_result(test, tc->input, ffs(tc->input),
+				    tc->expected_ffs, "ffs", tc->description);
+
+		/* Test fls() */
+		validate_ffs_result(test, tc->input, fls(tc->input),
+				    tc->expected_fls, "fls", tc->description);
+
+		/* Test __ffs() - skip zero case as it's undefined */
+		if (tc->input != 0) {
+			/* Calculate expected __ffs() result: __ffs(x) == ffs(x) - 1 */
+			unsigned int expected_ffs_0based = tc->expected_ffs - 1;
+			validate_ffs_result(test, tc->input, __ffs(tc->input),
+					    expected_ffs_0based, "__ffs", tc->description);
+		}
+
+		/* Test __fls() - skip zero case as it's undefined */
+		if (tc->input != 0) {
+			/* Calculate expected __fls() result: __fls(x) == fls(x) - 1 */
+			unsigned int expected_fls_0based = tc->expected_fls - 1;
+			validate_ffs_result(test, tc->input, __fls(tc->input),
+					    expected_fls_0based, "__fls", tc->description);
+		}
+	}
+}
+
+/*
+ * Test 64-bit function correctness
+ */
+static void ffs64_correctness_test(struct kunit *test)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ffs64_test_cases); i++) {
+		const struct ffs64_test_case *tc = &ffs64_test_cases[i];
+
+		/* Test fls64() */
+		validate_ffs64_result(test, tc->input, fls64(tc->input),
+				      tc->expected_fls64, "fls64", tc->description);
+
+		/* Test __ffs64() - skip zero case as it's undefined */
+		if (tc->input != 0) {
+			validate_ffs64_result(test, tc->input, __ffs64(tc->input),
+					      tc->expected_ffs64_0based, "__ffs64",
+					      tc->description);
+		}
+	}
+}
+
+/*
+ * Test mathematical relationships between functions
+ */
+static void ffs_mathematical_relationships_test(struct kunit *test)
+{
+	int i;
+
+	/* Test basic cases */
+	for (i = 0; i < ARRAY_SIZE(basic_test_cases); i++) {
+		validate_ffs_relationships(test, basic_test_cases[i].input);
+	}
+
+	/* Test 64-bit cases */
+	for (i = 0; i < ARRAY_SIZE(ffs64_test_cases); i++) {
+		validate_ffs64_relationships(test, ffs64_test_cases[i].input);
+	}
+}
+
+/*
+ * Test edge cases and boundary conditions
+ */
+static void ffs_edge_cases_test(struct kunit *test)
+{
+	unsigned long test_patterns[] = {
+		/* Powers of 2 */
+		1UL, 2UL, 4UL, 8UL, 16UL, 32UL, 64UL, 128UL,
+		256UL, 512UL, 1024UL, 2048UL, 4096UL, 8192UL,
+
+		/* Powers of 2 minus 1 */
+		1UL, 3UL, 7UL, 15UL, 31UL, 63UL, 127UL, 255UL,
+		511UL, 1023UL, 2047UL, 4095UL, 8191UL,
+
+		/* Boundary values */
+		0x7FFFFFFFUL,	/* Maximum positive 32-bit */
+		0x80000000UL,	/* Minimum negative 32-bit */
+		0xFFFFFFFFUL,	/* Maximum 32-bit unsigned */
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_patterns); i++) {
+		validate_ffs_relationships(test, test_patterns[i]);
+	}
+}
+
+/*
+ * Test 64-bit edge cases
+ */
+static void ffs64_edge_cases_test(struct kunit *test)
+{
+	u64 test_patterns_64[] = {
+		/* 64-bit powers of 2 */
+		0x0000000100000000ULL,	/* 2^32 */
+		0x0000000200000000ULL,	/* 2^33 */
+		0x0000000400000000ULL,	/* 2^34 */
+		0x0000001000000000ULL,	/* 2^36 */
+		0x0000010000000000ULL,	/* 2^40 */
+		0x0001000000000000ULL,	/* 2^48 */
+		0x0100000000000000ULL,	/* 2^56 */
+		0x4000000000000000ULL,	/* 2^62 */
+		0x8000000000000000ULL,	/* 2^63 */
+
+		/* Cross-boundary patterns */
+		0x00000000FFFFFFFFULL,	/* Lower 32 bits */
+		0xFFFFFFFF00000000ULL,	/* Upper 32 bits */
+		0x7FFFFFFFFFFFFFFFULL,	/* Maximum positive 64-bit */
+		0xFFFFFFFFFFFFFFFFULL,	/* Maximum 64-bit unsigned */
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_patterns_64); i++) {
+		validate_ffs64_relationships(test, test_patterns_64[i]);
+	}
+}
+
+/*
+ * ffz() test data - Find First Zero bit test cases
+ */
+struct ffz_test_case {
+	unsigned long input;
+	unsigned long expected_ffz;
+	const char *description;
+};
+
+static const struct ffz_test_case ffz_test_cases[] = {
+	/* Zero bits in specific positions */
+	{0xFFFFFFFE, 0, "bit 0 is zero"},      /* ...11111110 */
+	{0xFFFFFFFD, 1, "bit 1 is zero"},      /* ...11111101 */
+	{0xFFFFFFFB, 2, "bit 2 is zero"},      /* ...11111011 */
+	{0xFFFFFFF7, 3, "bit 3 is zero"},      /* ...11110111 */
+	{0xFFFFFFEF, 4, "bit 4 is zero"},      /* ...11101111 */
+	{0xFFFFFFDF, 5, "bit 5 is zero"},      /* ...11011111 */
+	{0xFFFFFFBF, 6, "bit 6 is zero"},      /* ...10111111 */
+	{0xFFFFFF7F, 7, "bit 7 is zero"},      /* ...01111111 */
+	{0xFFFFFEFF, 8, "bit 8 is zero"},      /* Gap in bit 8 */
+	{0xFFFF7FFF, 15, "bit 15 is zero"},    /* Gap in bit 15 */
+	{0xFFFEFFFF, 16, "bit 16 is zero"},    /* Gap in bit 16 */
+	{0xBFFFFFFF, 30, "bit 30 is zero"},    /* Gap in bit 30 */
+	{0x7FFFFFFF, 31, "bit 31 is zero"},    /* 01111111... */
+
+	/* Multiple zero patterns */
+	{0xFFFFFFFC, 0, "bits 0-1 are zero"},  /* ...11111100 */
+	{0xFFFFFFF8, 0, "bits 0-2 are zero"},  /* ...11111000 */
+	{0xFFFFFFF0, 0, "bits 0-3 are zero"},  /* ...11110000 */
+	{0xFFFFFF00, 0, "bits 0-7 are zero"},  /* ...00000000 */
+	{0xFFFF0000, 0, "bits 0-15 are zero"}, /* Lower 16 bits zero */
+
+	/* All zeros (special case) */
+	{0x00000000, 0, "all bits zero"},
+
+	/* Complex patterns */
+	{0xFFFDFFFF, 17, "bit 17 is zero"},    /* Gap in bit 17 */
+	{0xFFF7FFFF, 19, "bit 19 is zero"},    /* Gap in bit 19 */
+	{0xF7FFFFFF, 27, "bit 27 is zero"},    /* Gap in bit 27 */
+	{0xDFFFFFFF, 29, "bit 29 is zero"},    /* Gap in bit 29 */
+};
+
+/*
+ * Test basic correctness of ffz() function
+ */
+static void ffz_basic_correctness_test(struct kunit *test)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ffz_test_cases); i++) {
+		const struct ffz_test_case *tc = &ffz_test_cases[i];
+		unsigned long result = ffz(tc->input);
+
+		KUNIT_EXPECT_EQ_MSG(test, result, tc->expected_ffz,
+				    "ffz(0x%08lx) [%s]: expected %lu, got %lu",
+				    tc->input, tc->description, tc->expected_ffz, result);
+	}
+}
+
+/*
+ * Test mathematical relationships between ffz() and other functions
+ */
+static void validate_ffz_relationships(struct kunit *test, unsigned long input)
+{
+	unsigned long ffz_result;
+
+	if (input == 0) {
+		/* ffz(0) should return 0 (first zero bit is at position 0) */
+		KUNIT_EXPECT_EQ(test, ffz(input), 0);
+		return;
+	}
+
+	if (input == ~0UL) {
+		/* ffz(~0) is undefined (no zero bits) - just verify it doesn't crash */
+		ffz_result = ffz(input);
+		/* Implementation-defined behavior, just ensure it completes */
+		return;
+	}
+
+	ffz_result = ffz(input);
+
+	/* Range validation - result should be within valid bit range */
+	KUNIT_EXPECT_LT(test, ffz_result, BITS_PER_LONG);
+
+	/* Verify the bit at ffz_result position is actually zero */
+	KUNIT_EXPECT_EQ_MSG(test, (input >> ffz_result) & 1, 0,
+			    "ffz(0x%08lx) = %lu, but bit %lu is not zero",
+			    input, ffz_result, ffz_result);
+
+	/* Core relationship: if we set the ffz bit, ffz should find a different bit */
+	if (ffz_result < BITS_PER_LONG - 1) {
+		unsigned long modified = input | (1UL << ffz_result);
+		if (modified != ~0UL) { /* Skip if all bits would be set */
+			unsigned long new_ffz = ffz(modified);
+			KUNIT_EXPECT_NE_MSG(test, new_ffz, ffz_result,
+					    "ffz(0x%08lx) = %lu, but setting that bit doesn't change ffz result",
+					    input, ffz_result);
+		}
+	}
+}
+
+static void ffz_mathematical_relationships_test(struct kunit *test)
+{
+	unsigned long test_patterns[] = {
+		/* Powers of 2 with one bit clear */
+		0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFB, 0xFFFFFFF7,
+		0xFFFFFFEF, 0xFFFFFFDF, 0xFFFFFFBF, 0xFFFFFF7F,
+
+		/* Multiple patterns */
+		0xFFFFFF00, 0xFFFFF000, 0xFFFF0000, 0xFFF00000,
+		0x7FFFFFFF, 0x3FFFFFFF, 0x1FFFFFFF, 0x0FFFFFFF,
+
+		/* Complex bit patterns */
+		0xAAAAAAAA, 0x55555555, 0xCCCCCCCC, 0x33333333,
+		0xF0F0F0F0, 0x0F0F0F0F, 0xFF00FF00, 0x00FF00FF,
+	};
+	int i;
+
+	/* Test basic test cases */
+	for (i = 0; i < ARRAY_SIZE(ffz_test_cases); i++) {
+		validate_ffz_relationships(test, ffz_test_cases[i].input);
+	}
+
+	/* Test additional patterns */
+	for (i = 0; i < ARRAY_SIZE(test_patterns); i++) {
+		validate_ffz_relationships(test, test_patterns[i]);
+	}
+}
+
+/*
+ * Test edge cases and boundary conditions for ffz()
+ */
+static void ffz_edge_cases_test(struct kunit *test)
+{
+	unsigned long edge_patterns[] = {
+		/* Boundary values */
+		0x00000000,  /* All zeros */
+		0x80000000,  /* Only MSB set */
+		0x00000001,  /* Only LSB set */
+		0x7FFFFFFF,  /* MSB clear */
+		0xFFFFFFFE,  /* LSB clear */
+
+		/* Powers of 2 complement patterns (one zero bit each) */
+		~(1UL << 0),  ~(1UL << 1),  ~(1UL << 2),  ~(1UL << 3),
+		~(1UL << 4),  ~(1UL << 8),  ~(1UL << 16), ~(1UL << 31),
+
+		/* Walking zero patterns */
+		0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFB, 0xFFFFFFF7,
+		0xFFFFFFEF, 0xFFFFFFDF, 0xFFFFFFBF, 0xFFFFFF7F,
+		0xFFFFFEFF, 0xFFFFFDFF, 0xFFFFFBFF, 0xFFFFF7FF,
+
+		/* Multiple zeros */
+		0xFFFFFF00, 0xFFFFF000, 0xFFFF0000, 0xFFF00000,
+		0xFF000000, 0xF0000000, 0x00000000,
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(edge_patterns); i++) {
+		validate_ffz_relationships(test, edge_patterns[i]);
+	}
+}
+
+/*
+ * To have useful build error output, split the tests into separate
+ * functions so it's clear which are missing __attribute_const__.
+ */
+#define CREATE_WRAPPER(func)						\
+static noinline bool build_test_##func(void)				\
+{									\
+	int init_##func = 32;						\
+	int result_##func = func(6);					\
+									\
+	/* Does the static initializer vanish after calling func? */	\
+	BUILD_BUG_ON(init_##func < 32);					\
+									\
+	/* "Consume" the results so optimizer doesn't drop them. */	\
+	barrier_data(&init_##func);					\
+	barrier_data(&result_##func);					\
+									\
+	return true;							\
+}
+CREATE_WRAPPER(ffs)
+CREATE_WRAPPER(fls)
+CREATE_WRAPPER(__ffs)
+CREATE_WRAPPER(__fls)
+CREATE_WRAPPER(ffz)
+#undef CREATE_WRAPPER
+
+/*
+ * Make sure that __attribute_const__ has be applied to all the
+ * functions. This is a regression test for:
+ * https://github.com/KSPP/linux/issues/364
+ */
+static void ffs_attribute_const_test(struct kunit *test)
+{
+	KUNIT_EXPECT_TRUE(test, build_test_ffs());
+	KUNIT_EXPECT_TRUE(test, build_test_fls());
+	KUNIT_EXPECT_TRUE(test, build_test___ffs());
+	KUNIT_EXPECT_TRUE(test, build_test___fls());
+	KUNIT_EXPECT_TRUE(test, build_test_ffz());
+}
+
+/*
+ * KUnit test case definitions
+ */
+static struct kunit_case ffs_test_cases[] = {
+	KUNIT_CASE(ffs_basic_correctness_test),
+	KUNIT_CASE(ffs64_correctness_test),
+	KUNIT_CASE(ffs_mathematical_relationships_test),
+	KUNIT_CASE(ffs_edge_cases_test),
+	KUNIT_CASE(ffs64_edge_cases_test),
+	KUNIT_CASE(ffz_basic_correctness_test),
+	KUNIT_CASE(ffz_mathematical_relationships_test),
+	KUNIT_CASE(ffz_edge_cases_test),
+	KUNIT_CASE(ffs_attribute_const_test),
+	{}
+};
+
+/*
+ * KUnit test suite definition
+ */
+static struct kunit_suite ffs_test_suite = {
+	.name = "ffs",
+	.test_cases = ffs_test_cases,
+};
+
+kunit_test_suites(&ffs_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for ffs()-family functions");
+MODULE_LICENSE("GPL");