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, 115 insertions, 0 deletions

diff --git a/tools/perf/tests/util.c b/tools/perf/tests/util.c
new file mode 100644
index 000000000..f9abd9911
--- /dev/null
+++ b/tools/perf/tests/util.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "tests.h"
+#include "util/blake2s.h"
+#include "util/debug.h"
+
+#include <linux/compiler.h>
+#include <stdlib.h>
+#include <string2.h>
+
+static int test_strreplace(char needle, const char *haystack,
+			   const char *replace, const char *expected)
+{
+	char *new = strreplace_chars(needle, haystack, replace);
+	int ret = strcmp(new, expected);
+
+	free(new);
+	return ret == 0;
+}
+
+/* Maximum data length tested by test_blake2s() */
+#define MAX_DATA_LEN 512
+
+/*
+ * Hash length tested by test_blake2s().  BLAKE2s supports variable-length
+ * hashes.  However, the only user of BLAKE2s in 'perf' uses 20-byte hashes,
+ * matching the length of the ELF build ID field.  So that's the length we test.
+ */
+#define HASH_LEN 20
+
+/* Test the implementation of the BLAKE2s hash algorithm. */
+static int test_blake2s(void)
+{
+	u8 data[MAX_DATA_LEN];
+	u8 hash[HASH_LEN];
+	u8 hash2[HASH_LEN];
+	struct blake2s_ctx main_ctx;
+	/*
+	 * This value was generated by the following Python code:
+	 *
+	 * import hashlib
+	 *
+	 * data = bytes(i % 256 for i in range(513))
+	 * h = hashlib.blake2s(digest_size=20)
+	 * for i in range(513):
+	 *     h.update(hashlib.blake2s(data=data[:i], digest_size=20).digest())
+	 * print(h.hexdigest())
+	 */
+	static const u8 expected_hash_of_hashes[20] = {
+		0xef, 0x9b, 0x13, 0x98, 0x78, 0x8e, 0x74, 0x59, 0x9c, 0xd5,
+		0x0c, 0xf0, 0x33, 0x97, 0x79, 0x3d, 0x3e, 0xd0, 0x95, 0xa6
+	};
+	size_t i;
+
+	/* Generate MAX_DATA_LEN bytes of data. */
+	for (i = 0; i < MAX_DATA_LEN; i++)
+		data[i] = i;
+
+	blake2s_init(&main_ctx, sizeof(hash));
+	for (i = 0; i <= MAX_DATA_LEN; i++) {
+		struct blake2s_ctx ctx;
+
+		/* Compute the BLAKE2s hash of 'i' data bytes. */
+		blake2s_init(&ctx, HASH_LEN);
+		blake2s_update(&ctx, data, i);
+		blake2s_final(&ctx, hash);
+
+		/* Verify that multiple updates produce the same result. */
+		blake2s_init(&ctx, HASH_LEN);
+		blake2s_update(&ctx, data, i / 2);
+		blake2s_update(&ctx, &data[i / 2], i - (i / 2));
+		blake2s_final(&ctx, hash2);
+		TEST_ASSERT_VAL("inconsistent BLAKE2s hashes",
+				memcmp(hash, hash2, HASH_LEN) == 0);
+
+		/*
+		 * Pass the hash to another BLAKE2s context, so that we
+		 * incrementally compute the hash of all the hashes.
+		 */
+		blake2s_update(&main_ctx, hash, HASH_LEN);
+	}
+
+	/* Verify the hash of all the hashes. */
+	blake2s_final(&main_ctx, hash);
+	TEST_ASSERT_VAL("wrong BLAKE2s hashes",
+			memcmp(hash, expected_hash_of_hashes, HASH_LEN) == 0);
+	return 0;
+}
+
+static int test__blake2s_case(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
+{
+	return test_blake2s();
+}
+
+static int test__strreplace(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
+{
+	TEST_ASSERT_VAL("empty string", test_strreplace(' ', "", "123", ""));
+	TEST_ASSERT_VAL("no match", test_strreplace('5', "123", "4", "123"));
+	TEST_ASSERT_VAL("replace 1", test_strreplace('3', "123", "4", "124"));
+	TEST_ASSERT_VAL("replace 2", test_strreplace('a', "abcabc", "ef", "efbcefbc"));
+	TEST_ASSERT_VAL("replace long", test_strreplace('a', "abcabc", "longlong",
+							"longlongbclonglongbc"));
+
+	return 0;
+}
+
+static struct test_case tests__util[] = {
+	TEST_CASE("String replacement", strreplace),
+	TEST_CASE("BLAKE2s hash", blake2s_case),
+	{ .name = NULL, }
+};
+
+struct test_suite suite__util = {
+	.desc = "util",
+	.test_cases = tests__util,
+};