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, 156 insertions, 0 deletions

diff --git a/lib/tests/cpumask_kunit.c b/lib/tests/cpumask_kunit.c
new file mode 100644
index 000000000..6b62a6bdd
--- /dev/null
+++ b/lib/tests/cpumask_kunit.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for cpumask.
+ *
+ * Author: Sander Vanheule <sander@svanheule.net>
+ */
+
+#include <kunit/test.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+
+#define MASK_MSG(m) \
+	"%s contains %sCPUs %*pbl", #m, (cpumask_weight(m) ? "" : "no "), \
+	nr_cpumask_bits, cpumask_bits(m)
+
+#define EXPECT_FOR_EACH_CPU_EQ(test, mask)			\
+	do {							\
+		const cpumask_t *m = (mask);			\
+		int mask_weight = cpumask_weight(m);		\
+		int cpu, iter = 0;				\
+		for_each_cpu(cpu, m)				\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(mask));	\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_OP_EQ(test, op, mask1, mask2)			\
+	do {									\
+		const cpumask_t *m1 = (mask1);					\
+		const cpumask_t *m2 = (mask2);					\
+		int weight;                                                     \
+		int cpu, iter = 0;						\
+		cpumask_##op(&mask_tmp, m1, m2);                                \
+		weight = cpumask_weight(&mask_tmp);				\
+		for_each_cpu_##op(cpu, mask1, mask2)				\
+			iter++;							\
+		KUNIT_EXPECT_EQ((test), weight, iter);				\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_WRAP_EQ(test, mask)			\
+	do {							\
+		const cpumask_t *m = (mask);			\
+		int mask_weight = cpumask_weight(m);		\
+		int cpu, iter = 0;				\
+		for_each_cpu_wrap(cpu, m, nr_cpu_ids / 2)	\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(mask));	\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, name)		\
+	do {							\
+		int mask_weight = num_##name##_cpus();		\
+		int cpu, iter = 0;				\
+		for_each_##name##_cpu(cpu)			\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(cpu_##name##_mask));	\
+	} while (0)
+
+static cpumask_t mask_empty;
+static cpumask_t mask_all;
+static cpumask_t mask_tmp;
+
+static void test_cpumask_weight(struct kunit *test)
+{
+	KUNIT_EXPECT_TRUE_MSG(test, cpumask_empty(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_TRUE_MSG(test, cpumask_full(&mask_all), MASK_MSG(&mask_all));
+
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_weight(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids, cpumask_weight(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids, cpumask_weight(&mask_all), MASK_MSG(&mask_all));
+}
+
+static void test_cpumask_first(struct kunit *test)
+{
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_first(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_first(cpu_possible_mask), MASK_MSG(cpu_possible_mask));
+
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_first_zero(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_first_zero(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_last(struct kunit *test)
+{
+	KUNIT_EXPECT_LE_MSG(test, nr_cpumask_bits, cpumask_last(&mask_empty),
+			    MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids - 1, cpumask_last(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_next(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_next_zero(-1, &mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_next_zero(-1, cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_next(-1, &mask_empty),
+			    MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_next(-1, cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_iterators(struct kunit *test)
+{
+	EXPECT_FOR_EACH_CPU_EQ(test, &mask_empty);
+	EXPECT_FOR_EACH_CPU_WRAP_EQ(test, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, &mask_empty, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, cpu_possible_mask, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, andnot, &mask_empty, &mask_empty);
+
+	EXPECT_FOR_EACH_CPU_EQ(test, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_WRAP_EQ(test, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, cpu_possible_mask, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, andnot, cpu_possible_mask, &mask_empty);
+}
+
+static void test_cpumask_iterators_builtin(struct kunit *test)
+{
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, possible);
+
+	/* Ensure the dynamic masks are stable while running the tests */
+	cpu_hotplug_disable();
+
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, online);
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, present);
+
+	cpu_hotplug_enable();
+}
+
+static int test_cpumask_init(struct kunit *test)
+{
+	cpumask_clear(&mask_empty);
+	cpumask_setall(&mask_all);
+
+	return 0;
+}
+
+static struct kunit_case test_cpumask_cases[] = {
+	KUNIT_CASE(test_cpumask_weight),
+	KUNIT_CASE(test_cpumask_first),
+	KUNIT_CASE(test_cpumask_last),
+	KUNIT_CASE(test_cpumask_next),
+	KUNIT_CASE(test_cpumask_iterators),
+	KUNIT_CASE(test_cpumask_iterators_builtin),
+	{}
+};
+
+static struct kunit_suite test_cpumask_suite = {
+	.name = "cpumask",
+	.init = test_cpumask_init,
+	.test_cases = test_cpumask_cases,
+};
+kunit_test_suite(test_cpumask_suite);
+
+MODULE_DESCRIPTION("KUnit tests for cpumask");
+MODULE_LICENSE("GPL");