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, 181 insertions, 0 deletions

diff --git a/drivers/net/phy/national.c b/drivers/net/phy/national.c
new file mode 100644
index 000000000..7f3ff3228
--- /dev/null
+++ b/drivers/net/phy/national.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * drivers/net/phy/national.c
+ *
+ * Driver for National Semiconductor PHYs
+ *
+ * Author: Stuart Menefy <stuart.menefy@st.com>
+ * Maintainer: Giuseppe Cavallaro <peppe.cavallaro@st.com>
+ *
+ * Copyright (c) 2008 STMicroelectronics Limited
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/ethtool.h>
+#include <linux/phy.h>
+#include <linux/netdevice.h>
+
+/* DP83865 phy identifier values */
+#define DP83865_PHY_ID	0x20005c7a
+
+#define DP83865_INT_STATUS	0x14
+#define DP83865_INT_MASK	0x15
+#define DP83865_INT_CLEAR	0x17
+
+#define DP83865_INT_REMOTE_FAULT 0x0008
+#define DP83865_INT_ANE_COMPLETED 0x0010
+#define DP83865_INT_LINK_CHANGE	0xe000
+#define DP83865_INT_MASK_DEFAULT (DP83865_INT_REMOTE_FAULT | \
+				DP83865_INT_ANE_COMPLETED | \
+				DP83865_INT_LINK_CHANGE)
+
+/* Advanced proprietary configuration */
+#define NS_EXP_MEM_CTL	0x16
+#define NS_EXP_MEM_DATA	0x1d
+#define NS_EXP_MEM_ADD	0x1e
+
+#define LED_CTRL_REG 0x13
+#define AN_FALLBACK_AN 0x0001
+#define AN_FALLBACK_CRC 0x0002
+#define AN_FALLBACK_IE 0x0004
+#define ALL_FALLBACK_ON (AN_FALLBACK_AN |  AN_FALLBACK_CRC | AN_FALLBACK_IE)
+
+enum hdx_loopback {
+	hdx_loopback_on = 0,
+	hdx_loopback_off = 1,
+};
+
+static u8 ns_exp_read(struct phy_device *phydev, u16 reg)
+{
+	phy_write(phydev, NS_EXP_MEM_ADD, reg);
+	return phy_read(phydev, NS_EXP_MEM_DATA);
+}
+
+static void ns_exp_write(struct phy_device *phydev, u16 reg, u8 data)
+{
+	phy_write(phydev, NS_EXP_MEM_ADD, reg);
+	phy_write(phydev, NS_EXP_MEM_DATA, data);
+}
+
+static int ns_ack_interrupt(struct phy_device *phydev)
+{
+	int ret = phy_read(phydev, DP83865_INT_STATUS);
+	if (ret < 0)
+		return ret;
+
+	/* Clear the interrupt status bit by writing a “1”
+	 * to the corresponding bit in INT_CLEAR (2:0 are reserved)
+	 */
+	ret = phy_write(phydev, DP83865_INT_CLEAR, ret & ~0x7);
+
+	return ret;
+}
+
+static irqreturn_t ns_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, DP83865_INT_STATUS);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & DP83865_INT_MASK_DEFAULT))
+		return IRQ_NONE;
+
+	/* clear the interrupt */
+	phy_write(phydev, DP83865_INT_CLEAR, irq_status & ~0x7);
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+static int ns_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = ns_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write(phydev, DP83865_INT_MASK,
+				DP83865_INT_MASK_DEFAULT);
+	} else {
+		err = phy_write(phydev, DP83865_INT_MASK, 0);
+		if (err)
+			return err;
+
+		err = ns_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static void ns_giga_speed_fallback(struct phy_device *phydev, int mode)
+{
+	int bmcr = phy_read(phydev, MII_BMCR);
+
+	phy_write(phydev, MII_BMCR, (bmcr | BMCR_PDOWN));
+
+	/* Enable 8 bit expended memory read/write (no auto increment) */
+	phy_write(phydev, NS_EXP_MEM_CTL, 0);
+	phy_write(phydev, NS_EXP_MEM_ADD, 0x1C0);
+	phy_write(phydev, NS_EXP_MEM_DATA, 0x0008);
+	phy_write(phydev, MII_BMCR, (bmcr & ~BMCR_PDOWN));
+	phy_write(phydev, LED_CTRL_REG, mode);
+}
+
+static void ns_10_base_t_hdx_loopack(struct phy_device *phydev, int disable)
+{
+	u16 lb_dis = BIT(1);
+
+	if (disable)
+		ns_exp_write(phydev, 0x1c0,
+			     ns_exp_read(phydev, 0x1c0) | lb_dis);
+	else
+		ns_exp_write(phydev, 0x1c0,
+			     ns_exp_read(phydev, 0x1c0) & ~lb_dis);
+
+	pr_debug("10BASE-T HDX loopback %s\n",
+		 (ns_exp_read(phydev, 0x1c0) & lb_dis) ? "off" : "on");
+}
+
+static int ns_config_init(struct phy_device *phydev)
+{
+	ns_giga_speed_fallback(phydev, ALL_FALLBACK_ON);
+	/* In the latest MAC or switches design, the 10 Mbps loopback
+	 * is desired to be turned off.
+	 */
+	ns_10_base_t_hdx_loopack(phydev, hdx_loopback_off);
+	return ns_ack_interrupt(phydev);
+}
+
+static struct phy_driver dp83865_driver[] = { {
+	.phy_id = DP83865_PHY_ID,
+	.phy_id_mask = 0xfffffff0,
+	.name = "NatSemi DP83865",
+	/* PHY_GBIT_FEATURES */
+	.config_init = ns_config_init,
+	.config_intr = ns_config_intr,
+	.handle_interrupt = ns_handle_interrupt,
+} };
+
+module_phy_driver(dp83865_driver);
+
+MODULE_DESCRIPTION("NatSemi PHY driver");
+MODULE_AUTHOR("Stuart Menefy");
+MODULE_LICENSE("GPL");
+
+static const struct mdio_device_id __maybe_unused ns_tbl[] = {
+	{ DP83865_PHY_ID, 0xfffffff0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, ns_tbl);