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, 155 insertions, 0 deletions

diff --git a/lib/tests/bitfield_kunit.c b/lib/tests/bitfield_kunit.c
new file mode 100644
index 000000000..5ccd86f61
--- /dev/null
+++ b/lib/tests/bitfield_kunit.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Test cases for bitfield helpers.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <kunit/test.h>
+#include <linux/bitfield.h>
+
+#define CHECK_ENC_GET_U(tp, v, field, res) do {				\
+		{							\
+			u##tp _res;					\
+									\
+			_res = u##tp##_encode_bits(v, field);		\
+			KUNIT_ASSERT_FALSE_MSG(context, _res != res,	\
+				       "u" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != " #res "\n",	\
+				       (u64)_res);			\
+			KUNIT_ASSERT_FALSE(context,			\
+				   u##tp##_get_bits(_res, field) != v);	\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET_LE(tp, v, field, res) do {			\
+		{							\
+			__le##tp _res;					\
+									\
+			_res = le##tp##_encode_bits(v, field);		\
+			KUNIT_ASSERT_FALSE_MSG(context,			\
+				       _res != cpu_to_le##tp(res),	\
+				       "le" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != 0x%llx",\
+				       (u64)le##tp##_to_cpu(_res),	\
+				       (u64)(res));			\
+			KUNIT_ASSERT_FALSE(context,			\
+				   le##tp##_get_bits(_res, field) != v);\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET_BE(tp, v, field, res) do {			\
+		{							\
+			__be##tp _res;					\
+									\
+			_res = be##tp##_encode_bits(v, field);		\
+			KUNIT_ASSERT_FALSE_MSG(context,			\
+				       _res != cpu_to_be##tp(res),	\
+				       "be" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != 0x%llx",	\
+				       (u64)be##tp##_to_cpu(_res),	\
+				       (u64)(res));			\
+			KUNIT_ASSERT_FALSE(context,			\
+				   be##tp##_get_bits(_res, field) != v);\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET(tp, v, field, res) do {				\
+		CHECK_ENC_GET_U(tp, v, field, res);			\
+		CHECK_ENC_GET_LE(tp, v, field, res);			\
+		CHECK_ENC_GET_BE(tp, v, field, res);			\
+	} while (0)
+
+static void __init test_bitfields_constants(struct kunit *context)
+{
+	/*
+	 * NOTE
+	 * This whole function compiles (or at least should, if everything
+	 * is going according to plan) to nothing after optimisation.
+	 */
+
+	CHECK_ENC_GET(16,  1, 0x000f, 0x0001);
+	CHECK_ENC_GET(16,  3, 0x00f0, 0x0030);
+	CHECK_ENC_GET(16,  5, 0x0f00, 0x0500);
+	CHECK_ENC_GET(16,  7, 0xf000, 0x7000);
+	CHECK_ENC_GET(16, 14, 0x000f, 0x000e);
+	CHECK_ENC_GET(16, 15, 0x00f0, 0x00f0);
+
+	CHECK_ENC_GET_U(8,  1, 0x0f, 0x01);
+	CHECK_ENC_GET_U(8,  3, 0xf0, 0x30);
+	CHECK_ENC_GET_U(8, 14, 0x0f, 0x0e);
+	CHECK_ENC_GET_U(8, 15, 0xf0, 0xf0);
+
+	CHECK_ENC_GET(32,  1, 0x00000f00, 0x00000100);
+	CHECK_ENC_GET(32,  3, 0x0000f000, 0x00003000);
+	CHECK_ENC_GET(32,  5, 0x000f0000, 0x00050000);
+	CHECK_ENC_GET(32,  7, 0x00f00000, 0x00700000);
+	CHECK_ENC_GET(32, 14, 0x0f000000, 0x0e000000);
+	CHECK_ENC_GET(32, 15, 0xf0000000, 0xf0000000);
+
+	CHECK_ENC_GET(64,  1, 0x00000f0000000000ull, 0x0000010000000000ull);
+	CHECK_ENC_GET(64,  3, 0x0000f00000000000ull, 0x0000300000000000ull);
+	CHECK_ENC_GET(64,  5, 0x000f000000000000ull, 0x0005000000000000ull);
+	CHECK_ENC_GET(64,  7, 0x00f0000000000000ull, 0x0070000000000000ull);
+	CHECK_ENC_GET(64, 14, 0x0f00000000000000ull, 0x0e00000000000000ull);
+	CHECK_ENC_GET(64, 15, 0xf000000000000000ull, 0xf000000000000000ull);
+}
+
+#define CHECK(tp, mask) do {						\
+		u64 v;							\
+									\
+		for (v = 0; v < 1 << hweight32(mask); v++)		\
+			KUNIT_ASSERT_FALSE(context,			\
+				tp##_encode_bits(v, mask) != v << __ffs64(mask));\
+	} while (0)
+
+static void __init test_bitfields_variables(struct kunit *context)
+{
+	CHECK(u8, 0x0f);
+	CHECK(u8, 0xf0);
+	CHECK(u8, 0x38);
+
+	CHECK(u16, 0x0038);
+	CHECK(u16, 0x0380);
+	CHECK(u16, 0x3800);
+	CHECK(u16, 0x8000);
+
+	CHECK(u32, 0x80000000);
+	CHECK(u32, 0x7f000000);
+	CHECK(u32, 0x07e00000);
+	CHECK(u32, 0x00018000);
+
+	CHECK(u64, 0x8000000000000000ull);
+	CHECK(u64, 0x7f00000000000000ull);
+	CHECK(u64, 0x0001800000000000ull);
+	CHECK(u64, 0x0000000080000000ull);
+	CHECK(u64, 0x000000007f000000ull);
+	CHECK(u64, 0x0000000018000000ull);
+	CHECK(u64, 0x0000001f8000000ull);
+}
+
+#ifdef TEST_BITFIELD_COMPILE
+static void __init test_bitfields_compile(struct kunit *context)
+{
+	/* these should fail compilation */
+	CHECK_ENC_GET(16, 16, 0x0f00, 0x1000);
+	u32_encode_bits(7, 0x06000000);
+
+	/* this should at least give a warning */
+	u16_encode_bits(0, 0x60000);
+}
+#endif
+
+static struct kunit_case __refdata bitfields_test_cases[] = {
+	KUNIT_CASE(test_bitfields_constants),
+	KUNIT_CASE(test_bitfields_variables),
+	{}
+};
+
+static struct kunit_suite bitfields_test_suite = {
+	.name = "bitfields",
+	.test_cases = bitfields_test_cases,
+};
+
+kunit_test_suites(&bitfields_test_suite);
+
+MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
+MODULE_DESCRIPTION("Test cases for bitfield helpers");
+MODULE_LICENSE("GPL");