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, 49 insertions, 0 deletions

diff --git a/drivers/mfd/ocelot.h b/drivers/mfd/ocelot.h
new file mode 100644
index 000000000..b8bc2f148
--- /dev/null
+++ b/drivers/mfd/ocelot.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/* Copyright 2021, 2022 Innovative Advantage Inc. */
+
+#ifndef _MFD_OCELOT_H
+#define _MFD_OCELOT_H
+
+#include <linux/kconfig.h>
+
+struct device;
+struct regmap;
+struct resource;
+
+/**
+ * struct ocelot_ddata - Private data for an external Ocelot chip
+ * @gcb_regmap:		General Configuration Block regmap. Used for
+ *			operations like chip reset.
+ * @cpuorg_regmap:	CPU Device Origin Block regmap. Used for operations
+ *			like SPI bus configuration.
+ * @spi_padding_bytes:	Number of padding bytes that must be thrown out before
+ *			read data gets returned. This is calculated during
+ *			initialization based on bus speed.
+ * @dummy_buf:		Zero-filled buffer of spi_padding_bytes size. The dummy
+ *			bytes that will be sent out between the address and
+ *			data of a SPI read operation.
+ */
+struct ocelot_ddata {
+	struct regmap *gcb_regmap;
+	struct regmap *cpuorg_regmap;
+	int spi_padding_bytes;
+	void *dummy_buf;
+};
+
+int ocelot_chip_reset(struct device *dev);
+int ocelot_core_init(struct device *dev);
+
+/* SPI-specific routines that won't be necessary for other interfaces */
+struct regmap *ocelot_spi_init_regmap(struct device *dev,
+				      const struct resource *res);
+
+#define OCELOT_SPI_BYTE_ORDER_LE 0x00000000
+#define OCELOT_SPI_BYTE_ORDER_BE 0x81818181
+
+#ifdef __LITTLE_ENDIAN
+#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_LE
+#else
+#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_BE
+#endif
+
+#endif