Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

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");