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, 171 insertions, 0 deletions

diff --git a/drivers/net/phy/ncn26000.c b/drivers/net/phy/ncn26000.c
new file mode 100644
index 000000000..cabdd83c6
--- /dev/null
+++ b/drivers/net/phy/ncn26000.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+/*
+ *  Driver for the onsemi 10BASE-T1S NCN26000 PHYs family.
+ *
+ * Copyright 2022 onsemi
+ */
+#include <linux/kernel.h>
+#include <linux/bitfield.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/phy.h>
+
+#include "mdio-open-alliance.h"
+
+#define PHY_ID_NCN26000			0x180FF5A1
+
+#define NCN26000_REG_IRQ_CTL            16
+#define NCN26000_REG_IRQ_STATUS         17
+
+// the NCN26000 maps link_ctrl to BMCR_ANENABLE
+#define NCN26000_BCMR_LINK_CTRL_BIT	BMCR_ANENABLE
+
+// the NCN26000 maps link_status to BMSR_ANEGCOMPLETE
+#define NCN26000_BMSR_LINK_STATUS_BIT	BMSR_ANEGCOMPLETE
+
+#define NCN26000_IRQ_LINKST_BIT		BIT(0)
+#define NCN26000_IRQ_PLCAST_BIT		BIT(1)
+#define NCN26000_IRQ_LJABBER_BIT	BIT(2)
+#define NCN26000_IRQ_RJABBER_BIT	BIT(3)
+#define NCN26000_IRQ_PLCAREC_BIT	BIT(4)
+#define NCN26000_IRQ_PHYSCOL_BIT	BIT(5)
+#define NCN26000_IRQ_RESET_BIT		BIT(15)
+
+#define TO_TMR_DEFAULT			32
+
+static int ncn26000_config_init(struct phy_device *phydev)
+{
+	/* HW bug workaround: the default value of the PLCA TO_TIMER should be
+	 * 32, where the current version of NCN26000 reports 24. This will be
+	 * fixed in future PHY versions. For the time being, we force the
+	 * correct default here.
+	 */
+	return phy_write_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_PLCA_TOTMR,
+			     TO_TMR_DEFAULT);
+}
+
+static int ncn26000_config_aneg(struct phy_device *phydev)
+{
+	/* Note: the NCN26000 supports only P2MP link mode. Therefore, AN is not
+	 * supported. However, this function is invoked by phylib to enable the
+	 * PHY, regardless of the AN support.
+	 */
+	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
+	phydev->mdix = ETH_TP_MDI;
+
+	// bring up the link
+	return phy_write(phydev, MII_BMCR, NCN26000_BCMR_LINK_CTRL_BIT);
+}
+
+static int ncn26000_read_status(struct phy_device *phydev)
+{
+	/* The NCN26000 reports NCN26000_LINK_STATUS_BIT if the link status of
+	 * the PHY is up. It further reports the logical AND of the link status
+	 * and the PLCA status in the BMSR_LSTATUS bit.
+	 */
+	int ret;
+
+	/* The link state is latched low so that momentary link
+	 * drops can be detected. Do not double-read the status
+	 * in polling mode to detect such short link drops except
+	 * the link was already down.
+	 */
+	if (!phy_polling_mode(phydev) || !phydev->link) {
+		ret = phy_read(phydev, MII_BMSR);
+		if (ret < 0)
+			return ret;
+		else if (ret & NCN26000_BMSR_LINK_STATUS_BIT)
+			goto upd_link;
+	}
+
+	ret = phy_read(phydev, MII_BMSR);
+	if (ret < 0)
+		return ret;
+
+upd_link:
+	// update link status
+	if (ret & NCN26000_BMSR_LINK_STATUS_BIT) {
+		phydev->link = 1;
+		phydev->pause = 0;
+		phydev->duplex = DUPLEX_HALF;
+		phydev->speed = SPEED_10;
+	} else {
+		phydev->link = 0;
+		phydev->duplex = DUPLEX_UNKNOWN;
+		phydev->speed = SPEED_UNKNOWN;
+	}
+
+	return 0;
+}
+
+static irqreturn_t ncn26000_handle_interrupt(struct phy_device *phydev)
+{
+	int ret;
+
+	// read and aknowledge the IRQ status register
+	ret = phy_read(phydev, NCN26000_REG_IRQ_STATUS);
+
+	// check only link status changes
+	if (ret < 0 || (ret & NCN26000_REG_IRQ_STATUS) == 0)
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+	return IRQ_HANDLED;
+}
+
+static int ncn26000_config_intr(struct phy_device *phydev)
+{
+	int ret;
+	u16 irqe;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		// acknowledge IRQs
+		ret = phy_read(phydev, NCN26000_REG_IRQ_STATUS);
+		if (ret < 0)
+			return ret;
+
+		// get link status notifications
+		irqe = NCN26000_IRQ_LINKST_BIT;
+	} else {
+		// disable all IRQs
+		irqe = 0;
+	}
+
+	ret = phy_write(phydev, NCN26000_REG_IRQ_CTL, irqe);
+	if (ret != 0)
+		return ret;
+
+	return 0;
+}
+
+static struct phy_driver ncn26000_driver[] = {
+	{
+		PHY_ID_MATCH_MODEL(PHY_ID_NCN26000),
+		.name			= "NCN26000",
+		.features		= PHY_BASIC_T1S_P2MP_FEATURES,
+		.config_init            = ncn26000_config_init,
+		.config_intr            = ncn26000_config_intr,
+		.config_aneg		= ncn26000_config_aneg,
+		.read_status		= ncn26000_read_status,
+		.handle_interrupt       = ncn26000_handle_interrupt,
+		.get_plca_cfg		= genphy_c45_plca_get_cfg,
+		.set_plca_cfg		= genphy_c45_plca_set_cfg,
+		.get_plca_status	= genphy_c45_plca_get_status,
+		.soft_reset             = genphy_soft_reset,
+	},
+};
+
+module_phy_driver(ncn26000_driver);
+
+static const struct mdio_device_id __maybe_unused ncn26000_tbl[] = {
+	{ PHY_ID_MATCH_MODEL(PHY_ID_NCN26000) },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, ncn26000_tbl);
+
+MODULE_AUTHOR("Piergiorgio Beruto");
+MODULE_DESCRIPTION("onsemi 10BASE-T1S PHY driver");
+MODULE_LICENSE("Dual BSD/GPL");