ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 205 insertions, 0 deletions

diff --git a/lib/tests/bitops_kunit.c b/lib/tests/bitops_kunit.c
new file mode 100644
index 000000000..7fd9d697f
--- /dev/null
+++ b/lib/tests/bitops_kunit.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Copyright (C) 2026 Ryota Sakamoto <sakamo.ryota@gmail.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <kunit/test.h>
+
+/* use an enum because that's the most common BITMAP usage */
+enum bitops_fun {
+	BITOPS_4 = 4,
+	BITOPS_7 = 7,
+	BITOPS_11 = 11,
+	BITOPS_31 = 31,
+	BITOPS_88 = 88,
+	BITOPS_LENGTH = 256
+};
+
+struct bitops_test_case {
+	const char *str;
+	const long nr;
+};
+
+static struct bitops_test_case bitops_cases[] = {
+	{
+		.str = "BITOPS_4",
+		.nr = BITOPS_4,
+	},
+	{
+		.str = "BITOPS_7",
+		.nr = BITOPS_7,
+	},
+	{
+		.str = "BITOPS_11",
+		.nr = BITOPS_11,
+	},
+	{
+		.str = "BITOPS_31",
+		.nr = BITOPS_31,
+	},
+	{
+		.str = "BITOPS_88",
+		.nr = BITOPS_88,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(bitops, bitops_cases, str);
+
+static void test_set_bit_clear_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	set_bit(params->nr, bitmap);
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	clear_bit(params->nr, bitmap);
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_change_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	change_bit(params->nr, bitmap);
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	change_bit(params->nr, bitmap);
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_test_and_set_bit_test_and_clear_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	KUNIT_EXPECT_FALSE(test, test_and_set_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_set_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_clear_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_FALSE(test, test_and_clear_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_test_and_change_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	KUNIT_EXPECT_FALSE(test, test_and_change_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_change_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+struct order_test_case {
+	const char *str;
+	const unsigned int count;
+	const int expected;
+};
+
+static struct order_test_case order_test_cases[] = {
+	{"0x00000003", 0x00000003,  2},
+	{"0x00000004", 0x00000004,  2},
+	{"0x00001fff", 0x00001fff, 13},
+	{"0x00002000", 0x00002000, 13},
+	{"0x50000000", 0x50000000, 31},
+	{"0x80000000", 0x80000000, 31},
+	{"0x80003000", 0x80003000, 32},
+};
+
+KUNIT_ARRAY_PARAM_DESC(order, order_test_cases, str);
+
+static void test_get_count_order(struct kunit *test)
+{
+	const struct order_test_case *params = test->param_value;
+
+	KUNIT_EXPECT_EQ(test, get_count_order(params->count), params->expected);
+	KUNIT_EXPECT_EQ(test, get_count_order_long(params->count), params->expected);
+}
+
+#ifdef CONFIG_64BIT
+struct order_long_test_case {
+	const char *str;
+	const unsigned long count;
+	const int expected;
+};
+
+static struct order_long_test_case order_long_test_cases[] = {
+	{"0x0000000300000000", 0x0000000300000000, 34},
+	{"0x0000000400000000", 0x0000000400000000, 34},
+	{"0x00001fff00000000", 0x00001fff00000000, 45},
+	{"0x0000200000000000", 0x0000200000000000, 45},
+	{"0x5000000000000000", 0x5000000000000000, 63},
+	{"0x8000000000000000", 0x8000000000000000, 63},
+	{"0x8000300000000000", 0x8000300000000000, 64},
+};
+
+KUNIT_ARRAY_PARAM_DESC(order_long, order_long_test_cases, str);
+
+static void test_get_count_order_long(struct kunit *test)
+{
+	const struct order_long_test_case *params = test->param_value;
+
+	KUNIT_EXPECT_EQ(test, get_count_order_long(params->count), params->expected);
+}
+#endif
+
+static struct kunit_case bitops_test_cases[] = {
+	KUNIT_CASE_PARAM(test_set_bit_clear_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_change_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_test_and_set_bit_test_and_clear_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_test_and_change_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_get_count_order, order_gen_params),
+#ifdef CONFIG_64BIT
+	KUNIT_CASE_PARAM(test_get_count_order_long, order_long_gen_params),
+#endif
+	{},
+};
+
+static struct kunit_suite bitops_test_suite = {
+	.name = "bitops",
+	.test_cases = bitops_test_cases,
+};
+
+kunit_test_suite(bitops_test_suite);
+
+MODULE_AUTHOR("Jesse Brandeburg <jesse.brandeburg@intel.com>");
+MODULE_AUTHOR("Wei Yang <richard.weiyang@gmail.com>");
+MODULE_AUTHOR("Ryota Sakamoto <sakamo.ryota@gmail.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Bit testing module");