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, 250 insertions, 0 deletions

diff --git a/drivers/mfd/stw481x.c b/drivers/mfd/stw481x.c
new file mode 100644
index 000000000..5ed64d53c
--- /dev/null
+++ b/drivers/mfd/stw481x.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Core driver for STw4810/STw4811
+ *
+ * Copyright (C) 2013 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/stw481x.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+
+/*
+ * This driver can only access the non-USB portions of STw4811, the register
+ * range 0x00-0x10 dealing with USB is bound to the two special I2C pins used
+ * for USB control.
+ */
+
+/* Registers inside the power control address space */
+#define STW_PC_VCORE_SEL	0x05U
+#define STW_PC_VAUX_SEL		0x06U
+#define STW_PC_VPLL_SEL		0x07U
+
+/**
+ * stw481x_get_pctl_reg() - get a power control register
+ * @stw481x: handle to the stw481x chip
+ * @reg: power control register to fetch
+ *
+ * The power control registers is a set of one-time-programmable registers
+ * in its own register space, accessed by writing addess bits to these
+ * two registers: bits 7,6,5 of PCTL_REG_LO corresponds to the 3 LSBs of
+ * the address and bits 8,9 of PCTL_REG_HI corresponds to the 2 MSBs of
+ * the address, forming an address space of 5 bits, i.e. 32 registers
+ * 0x00 ... 0x1f can be obtained.
+ */
+static int stw481x_get_pctl_reg(struct stw481x *stw481x, u8 reg)
+{
+	u8 msb = (reg >> 3) & 0x03;
+	u8 lsb = (reg << 5) & 0xe0;
+	unsigned int val;
+	u8 vrfy;
+	int ret;
+
+	ret = regmap_write(stw481x->map, STW_PCTL_REG_HI, msb);
+	if (ret)
+		return ret;
+	ret = regmap_write(stw481x->map, STW_PCTL_REG_LO, lsb);
+	if (ret)
+		return ret;
+	ret = regmap_read(stw481x->map, STW_PCTL_REG_HI, &val);
+	if (ret)
+		return ret;
+	vrfy = (val & 0x03) << 3;
+	ret = regmap_read(stw481x->map, STW_PCTL_REG_LO, &val);
+	if (ret)
+		return ret;
+	vrfy |= ((val >> 5) & 0x07);
+	if (vrfy != reg)
+		return -EIO;
+	return (val >> 1) & 0x0f;
+}
+
+static int stw481x_startup(struct stw481x *stw481x)
+{
+	/* Voltages multiplied by 100 */
+	static const u8 vcore_val[] = {
+		100, 105, 110, 115, 120, 122, 124, 126, 128,
+		130, 132, 134, 136, 138, 140, 145
+	};
+	static const u8 vpll_val[] = { 105, 120, 130, 180 };
+	static const u8 vaux_val[] = { 15, 18, 25, 28 };
+	u8 vcore;
+	u8 vcore_slp;
+	u8 vpll;
+	u8 vaux;
+	bool vaux_en;
+	bool it_warn;
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(stw481x->map, STW_CONF1, &val);
+	if (ret)
+		return ret;
+	vaux_en = !!(val & STW_CONF1_PDN_VAUX);
+	it_warn = !!(val & STW_CONF1_IT_WARN);
+
+	dev_info(&stw481x->client->dev, "voltages %s\n",
+		(val & STW_CONF1_V_MONITORING) ? "OK" : "LOW");
+	dev_info(&stw481x->client->dev, "MMC level shifter %s\n",
+		(val & STW_CONF1_MMC_LS_STATUS) ? "high impedance" : "ON");
+	dev_info(&stw481x->client->dev, "VMMC: %s\n",
+		(val & STW_CONF1_PDN_VMMC) ? "ON" : "disabled");
+
+	dev_info(&stw481x->client->dev, "STw481x power control registers:\n");
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VCORE_SEL);
+	if (ret < 0)
+		return ret;
+	vcore = ret & 0x0f;
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VAUX_SEL);
+	if (ret < 0)
+		return ret;
+	vaux = (ret >> 2) & 3;
+	vpll = (ret >> 4) & 1; /* Save bit 4 */
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VPLL_SEL);
+	if (ret < 0)
+		return ret;
+	vpll |= (ret >> 1) & 2;
+
+	dev_info(&stw481x->client->dev, "VCORE: %u.%uV %s\n",
+		vcore_val[vcore] / 100, vcore_val[vcore] % 100,
+		(ret & 4) ? "ON" : "OFF");
+
+	dev_info(&stw481x->client->dev, "VPLL:  %u.%uV %s\n",
+		vpll_val[vpll] / 100, vpll_val[vpll] % 100,
+		(ret & 0x10) ? "ON" : "OFF");
+
+	dev_info(&stw481x->client->dev, "VAUX:  %u.%uV %s\n",
+		vaux_val[vaux] / 10, vaux_val[vaux] % 10,
+		vaux_en ? "ON" : "OFF");
+
+	ret = regmap_read(stw481x->map, STW_CONF2, &val);
+	if (ret)
+		return ret;
+
+	dev_info(&stw481x->client->dev, "TWARN: %s threshold, %s\n",
+		it_warn ? "below" : "above",
+		(val & STW_CONF2_MASK_TWARN) ?
+		 "enabled" : "mask through VDDOK");
+	dev_info(&stw481x->client->dev, "VMMC: %s\n",
+		(val & STW_CONF2_VMMC_EXT) ? "internal" : "external");
+	dev_info(&stw481x->client->dev, "IT WAKE UP: %s\n",
+		(val & STW_CONF2_MASK_IT_WAKE_UP) ? "enabled" : "masked");
+	dev_info(&stw481x->client->dev, "GPO1: %s\n",
+		(val & STW_CONF2_GPO1) ? "low" : "high impedance");
+	dev_info(&stw481x->client->dev, "GPO2: %s\n",
+		(val & STW_CONF2_GPO2) ? "low" : "high impedance");
+
+	ret = regmap_read(stw481x->map, STW_VCORE_SLEEP, &val);
+	if (ret)
+		return ret;
+	vcore_slp = val & 0x0f;
+	dev_info(&stw481x->client->dev, "VCORE SLEEP: %u.%uV\n",
+		vcore_val[vcore_slp] / 100, vcore_val[vcore_slp] % 100);
+
+	return 0;
+}
+
+/*
+ * MFD cells - we have one cell which is selected operation
+ * mode, and we always have a GPIO cell.
+ */
+static struct mfd_cell stw481x_cells[] = {
+	{
+		.of_compatible = "st,stw481x-vmmc",
+		.name = "stw481x-vmmc-regulator",
+		.id = -1,
+	},
+};
+
+static const struct regmap_config stw481x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int stw481x_probe(struct i2c_client *client)
+{
+	struct stw481x			*stw481x;
+	int ret;
+	int i;
+
+	stw481x = devm_kzalloc(&client->dev, sizeof(*stw481x), GFP_KERNEL);
+	if (!stw481x)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, stw481x);
+	stw481x->client = client;
+	stw481x->map = devm_regmap_init_i2c(client, &stw481x_regmap_config);
+	if (IS_ERR(stw481x->map)) {
+		ret = PTR_ERR(stw481x->map);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = stw481x_startup(stw481x);
+	if (ret) {
+		dev_err(&client->dev, "chip initialization failed\n");
+		return ret;
+	}
+
+	/* Set up and register the platform devices. */
+	for (i = 0; i < ARRAY_SIZE(stw481x_cells); i++) {
+		/* One state holder for all drivers, this is simple */
+		stw481x_cells[i].platform_data = stw481x;
+		stw481x_cells[i].pdata_size = sizeof(*stw481x);
+	}
+
+	ret = devm_mfd_add_devices(&client->dev, 0, stw481x_cells,
+				   ARRAY_SIZE(stw481x_cells), NULL, 0, NULL);
+	if (ret)
+		return ret;
+
+	dev_info(&client->dev, "initialized STw481x device\n");
+
+	return ret;
+}
+
+/*
+ * This ID table is completely unused, as this is a pure
+ * device-tree probed driver, but it has to be here due to
+ * the structure of the I2C core.
+ */
+static const struct i2c_device_id stw481x_id[] = {
+	{ "stw481x" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, stw481x_id);
+
+static const struct of_device_id stw481x_match[] = {
+	{ .compatible = "st,stw4810", },
+	{ .compatible = "st,stw4811", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, stw481x_match);
+
+static struct i2c_driver stw481x_driver = {
+	.driver = {
+		.name	= "stw481x",
+		.of_match_table = stw481x_match,
+	},
+	.probe		= stw481x_probe,
+	.id_table	= stw481x_id,
+};
+
+module_i2c_driver(stw481x_driver);
+
+MODULE_AUTHOR("Linus Walleij");
+MODULE_DESCRIPTION("STw481x PMIC driver");
+MODULE_LICENSE("GPL v2");