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, 215 insertions, 0 deletions

diff --git a/drivers/tty/tty_baudrate.c b/drivers/tty/tty_baudrate.c
new file mode 100644
index 000000000..f9b49939c
--- /dev/null
+++ b/drivers/tty/tty_baudrate.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/termios.h>
+#include <linux/tty.h>
+#include <linux/export.h>
+#include "tty.h"
+
+
+/*
+ * Routine which returns the baud rate of the tty
+ *
+ * Note that the baud_table needs to be kept in sync with the
+ * include/asm/termbits.h file.
+ */
+static const speed_t baud_table[] = {
+	0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400,
+	4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800,
+#ifdef __sparc__
+	76800, 153600, 307200, 614400, 921600, 500000, 576000,
+	1000000, 1152000, 1500000, 2000000
+#else
+	500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
+	2500000, 3000000, 3500000, 4000000
+#endif
+};
+
+static const tcflag_t baud_bits[] = {
+	B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400,
+	B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800,
+#ifdef __sparc__
+	B76800, B153600, B307200, B614400, B921600, B500000, B576000,
+	B1000000, B1152000, B1500000, B2000000
+#else
+	B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,
+	B2500000, B3000000, B3500000, B4000000
+#endif
+};
+
+static int n_baud_table = ARRAY_SIZE(baud_table);
+
+/**
+ *	tty_termios_baud_rate
+ *	@termios: termios structure
+ *
+ *	Convert termios baud rate data into a speed. This should be called
+ *	with the termios lock held if this termios is a terminal termios
+ *	structure. Device drivers can call this function but should use
+ *	->c_[io]speed directly as they are updated.
+ *
+ *	Locking: none
+ */
+
+speed_t tty_termios_baud_rate(const struct ktermios *termios)
+{
+	unsigned int cbaud;
+
+	cbaud = termios->c_cflag & CBAUD;
+
+	/* Magic token for arbitrary speed via c_ispeed/c_ospeed */
+	if (cbaud == BOTHER)
+		return termios->c_ospeed;
+
+	if (cbaud & CBAUDEX) {
+		cbaud &= ~CBAUDEX;
+		cbaud += 15;
+	}
+	return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
+}
+EXPORT_SYMBOL(tty_termios_baud_rate);
+
+/**
+ *	tty_termios_input_baud_rate
+ *	@termios: termios structure
+ *
+ *	Convert termios baud rate data into a speed. This should be called
+ *	with the termios lock held if this termios is a terminal termios
+ *	structure. Device drivers can call this function but should use
+ *	->c_[io]speed directly as they are updated.
+ *
+ *	Locking: none
+ */
+
+speed_t tty_termios_input_baud_rate(const struct ktermios *termios)
+{
+	unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
+
+	if (cbaud == B0)
+		return tty_termios_baud_rate(termios);
+
+	/* Magic token for arbitrary speed via c_ispeed */
+	if (cbaud == BOTHER)
+		return termios->c_ispeed;
+
+	if (cbaud & CBAUDEX) {
+		cbaud &= ~CBAUDEX;
+		cbaud += 15;
+	}
+	return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
+}
+EXPORT_SYMBOL(tty_termios_input_baud_rate);
+
+/**
+ *	tty_termios_encode_baud_rate
+ *	@termios: ktermios structure holding user requested state
+ *	@ibaud: input speed
+ *	@obaud: output speed
+ *
+ *	Encode the speeds set into the passed termios structure. This is
+ *	used as a library helper for drivers so that they can report back
+ *	the actual speed selected when it differs from the speed requested
+ *
+ *	For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
+ *	we need to carefully set the bits when the user does not get the
+ *	desired speed. We allow small margins and preserve as much of possible
+ *	of the input intent to keep compatibility.
+ *
+ *	Locking: Caller should hold termios lock. This is already held
+ *	when calling this function from the driver termios handler.
+ *
+ *	The ifdefs deal with platforms whose owners have yet to update them
+ *	and will all go away once this is done.
+ */
+
+void tty_termios_encode_baud_rate(struct ktermios *termios,
+				  speed_t ibaud, speed_t obaud)
+{
+	int i = 0;
+	int ifound = -1, ofound = -1;
+	int iclose = ibaud/50, oclose = obaud/50;
+	int ibinput = 0;
+
+	if (obaud == 0)			/* CD dropped */
+		ibaud = 0;		/* Clear ibaud to be sure */
+
+	termios->c_ispeed = ibaud;
+	termios->c_ospeed = obaud;
+
+	if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0)
+		ibinput = 1;	/* An input speed was specified */
+
+	/* If the user asked for a precise weird speed give a precise weird
+	 * answer. If they asked for a Bfoo speed they may have problems
+	 * digesting non-exact replies so fuzz a bit.
+	 */
+
+	if ((termios->c_cflag & CBAUD) == BOTHER) {
+		oclose = 0;
+		if (!ibinput)
+			iclose = 0;
+	}
+	if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
+		iclose = 0;
+
+	termios->c_cflag &= ~CBAUD;
+	termios->c_cflag &= ~(CBAUD << IBSHIFT);
+
+	/*
+	 *	Our goal is to find a close match to the standard baud rate
+	 *	returned. Walk the baud rate table and if we get a very close
+	 *	match then report back the speed as a POSIX Bxxxx value by
+	 *	preference
+	 */
+
+	do {
+		if (obaud - oclose <= baud_table[i] &&
+		    obaud + oclose >= baud_table[i]) {
+			termios->c_cflag |= baud_bits[i];
+			ofound = i;
+		}
+		if (ibaud - iclose <= baud_table[i] &&
+		    ibaud + iclose >= baud_table[i]) {
+			/* For the case input == output don't set IBAUD bits
+			 * if the user didn't do so.
+			 */
+			if (ofound == i && !ibinput) {
+				ifound  = i;
+			} else {
+				ifound = i;
+				termios->c_cflag |= (baud_bits[i] << IBSHIFT);
+			}
+		}
+	} while (++i < n_baud_table);
+
+	/* If we found no match then use BOTHER. */
+	if (ofound == -1)
+		termios->c_cflag |= BOTHER;
+	/* Set exact input bits only if the input and output differ or the
+	 * user already did.
+	 */
+	if (ifound == -1 && (ibaud != obaud || ibinput))
+		termios->c_cflag |= (BOTHER << IBSHIFT);
+}
+EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
+
+/**
+ *	tty_encode_baud_rate		-	set baud rate of the tty
+ *	@tty:   terminal device
+ *	@ibaud: input baud rate
+ *	@obaud: output baud rate
+ *
+ *	Update the current termios data for the tty with the new speed
+ *	settings. The caller must hold the termios_rwsem for the tty in
+ *	question.
+ */
+
+void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
+{
+	tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
+}
+EXPORT_SYMBOL_GPL(tty_encode_baud_rate);