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, 48 insertions, 0 deletions

diff --git a/drivers/soc/apple/mailbox.h b/drivers/soc/apple/mailbox.h
new file mode 100644
index 000000000..f73a8913d
--- /dev/null
+++ b/drivers/soc/apple/mailbox.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/*
+ * Apple mailbox message format
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#ifndef _APPLE_MAILBOX_H_
+#define _APPLE_MAILBOX_H_
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+/* encodes a single 96bit message sent over the single channel */
+struct apple_mbox_msg {
+	u64 msg0;
+	u32 msg1;
+};
+
+struct apple_mbox {
+	struct device *dev;
+	void __iomem *regs;
+	const struct apple_mbox_hw *hw;
+	bool active;
+
+	int irq_recv_not_empty;
+	int irq_send_empty;
+
+	spinlock_t rx_lock;
+	spinlock_t tx_lock;
+
+	struct completion tx_empty;
+
+	/** Receive callback for incoming messages */
+	void (*rx)(struct apple_mbox *mbox, struct apple_mbox_msg msg, void *cookie);
+	void *cookie;
+};
+
+struct apple_mbox *apple_mbox_get(struct device *dev, int index);
+struct apple_mbox *apple_mbox_get_byname(struct device *dev, const char *name);
+
+int apple_mbox_start(struct apple_mbox *mbox);
+void apple_mbox_stop(struct apple_mbox *mbox);
+int apple_mbox_poll(struct apple_mbox *mbox);
+int apple_mbox_send(struct apple_mbox *mbox, struct apple_mbox_msg msg,
+		    bool atomic);
+
+#endif