kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 460 insertions, 0 deletions

diff --git a/drivers/regulator/lp3971.c b/drivers/regulator/lp3971.c
new file mode 100644
index 000000000..d4dab86fe
--- /dev/null
+++ b/drivers/regulator/lp3971.c
@@ -0,0 +1,460 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Regulator driver for National Semiconductors LP3971 PMIC chip
+ *
+ *  Copyright (C) 2009 Samsung Electronics
+ *  Author: Marek Szyprowski <m.szyprowski@samsung.com>
+ *
+ * Based on wm8350.c
+ */
+
+#include <linux/bug.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/lp3971.h>
+#include <linux/slab.h>
+
+struct lp3971 {
+	struct device *dev;
+	struct mutex io_lock;
+	struct i2c_client *i2c;
+};
+
+static u8 lp3971_reg_read(struct lp3971 *lp3971, u8 reg);
+static int lp3971_set_bits(struct lp3971 *lp3971, u8 reg, u16 mask, u16 val);
+
+#define LP3971_SYS_CONTROL1_REG 0x07
+
+/* System control register 1 initial value,
+   bits 4 and 5 are EPROM programmable */
+#define SYS_CONTROL1_INIT_VAL 0x40
+#define SYS_CONTROL1_INIT_MASK 0xCF
+
+#define LP3971_BUCK_VOL_ENABLE_REG 0x10
+#define LP3971_BUCK_VOL_CHANGE_REG 0x20
+
+/*	Voltage control registers shift:
+	LP3971_BUCK1 -> 0
+	LP3971_BUCK2 -> 4
+	LP3971_BUCK3 -> 6
+*/
+#define BUCK_VOL_CHANGE_SHIFT(x) (((!!x) << 2) | (x & ~0x01))
+#define BUCK_VOL_CHANGE_FLAG_GO 0x01
+#define BUCK_VOL_CHANGE_FLAG_TARGET 0x02
+#define BUCK_VOL_CHANGE_FLAG_MASK 0x03
+
+#define LP3971_BUCK1_BASE 0x23
+#define LP3971_BUCK2_BASE 0x29
+#define LP3971_BUCK3_BASE 0x32
+
+static const int buck_base_addr[] = {
+	LP3971_BUCK1_BASE,
+	LP3971_BUCK2_BASE,
+	LP3971_BUCK3_BASE,
+};
+
+#define LP3971_BUCK_TARGET_VOL1_REG(x) (buck_base_addr[x])
+#define LP3971_BUCK_TARGET_VOL2_REG(x) (buck_base_addr[x]+1)
+
+static const unsigned int buck_voltage_map[] = {
+	      0,  800000,  850000,  900000,  950000, 1000000, 1050000, 1100000,
+	1150000, 1200000, 1250000, 1300000, 1350000, 1400000, 1450000, 1500000,
+	1550000, 1600000, 1650000, 1700000, 1800000, 1900000, 2500000, 2800000,
+	3000000, 3300000,
+};
+
+#define BUCK_TARGET_VOL_MASK 0x3f
+
+#define LP3971_BUCK_RAMP_REG(x)	(buck_base_addr[x]+2)
+
+#define LP3971_LDO_ENABLE_REG 0x12
+#define LP3971_LDO_VOL_CONTR_BASE 0x39
+
+/*	Voltage control registers:
+	LP3971_LDO1 -> LP3971_LDO_VOL_CONTR_BASE + 0
+	LP3971_LDO2 -> LP3971_LDO_VOL_CONTR_BASE + 0
+	LP3971_LDO3 -> LP3971_LDO_VOL_CONTR_BASE + 1
+	LP3971_LDO4 -> LP3971_LDO_VOL_CONTR_BASE + 1
+	LP3971_LDO5 -> LP3971_LDO_VOL_CONTR_BASE + 2
+*/
+#define LP3971_LDO_VOL_CONTR_REG(x)	(LP3971_LDO_VOL_CONTR_BASE + (x >> 1))
+
+/*	Voltage control registers shift:
+	LP3971_LDO1 -> 0, LP3971_LDO2 -> 4
+	LP3971_LDO3 -> 0, LP3971_LDO4 -> 4
+	LP3971_LDO5 -> 0
+*/
+#define LDO_VOL_CONTR_SHIFT(x) ((x & 1) << 2)
+#define LDO_VOL_CONTR_MASK 0x0f
+
+static const unsigned int ldo45_voltage_map[] = {
+	1000000, 1050000, 1100000, 1150000, 1200000, 1250000, 1300000, 1350000,
+	1400000, 1500000, 1800000, 1900000, 2500000, 2800000, 3000000, 3300000,
+};
+
+static const unsigned int ldo123_voltage_map[] = {
+	1800000, 1900000, 2000000, 2100000, 2200000, 2300000, 2400000, 2500000,
+	2600000, 2700000, 2800000, 2900000, 3000000, 3100000, 3200000, 3300000,
+};
+
+#define LDO_VOL_MIN_IDX 0x00
+#define LDO_VOL_MAX_IDX 0x0f
+
+static int lp3971_ldo_is_enabled(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int ldo = rdev_get_id(dev) - LP3971_LDO1;
+	u16 mask = 1 << (1 + ldo);
+	u16 val;
+
+	val = lp3971_reg_read(lp3971, LP3971_LDO_ENABLE_REG);
+	return (val & mask) != 0;
+}
+
+static int lp3971_ldo_enable(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int ldo = rdev_get_id(dev) - LP3971_LDO1;
+	u16 mask = 1 << (1 + ldo);
+
+	return lp3971_set_bits(lp3971, LP3971_LDO_ENABLE_REG, mask, mask);
+}
+
+static int lp3971_ldo_disable(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int ldo = rdev_get_id(dev) - LP3971_LDO1;
+	u16 mask = 1 << (1 + ldo);
+
+	return lp3971_set_bits(lp3971, LP3971_LDO_ENABLE_REG, mask, 0);
+}
+
+static int lp3971_ldo_get_voltage_sel(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int ldo = rdev_get_id(dev) - LP3971_LDO1;
+	u16 val, reg;
+
+	reg = lp3971_reg_read(lp3971, LP3971_LDO_VOL_CONTR_REG(ldo));
+	val = (reg >> LDO_VOL_CONTR_SHIFT(ldo)) & LDO_VOL_CONTR_MASK;
+
+	return val;
+}
+
+static int lp3971_ldo_set_voltage_sel(struct regulator_dev *dev,
+				      unsigned int selector)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int ldo = rdev_get_id(dev) - LP3971_LDO1;
+
+	return lp3971_set_bits(lp3971, LP3971_LDO_VOL_CONTR_REG(ldo),
+			LDO_VOL_CONTR_MASK << LDO_VOL_CONTR_SHIFT(ldo),
+			selector << LDO_VOL_CONTR_SHIFT(ldo));
+}
+
+static const struct regulator_ops lp3971_ldo_ops = {
+	.list_voltage = regulator_list_voltage_table,
+	.map_voltage = regulator_map_voltage_ascend,
+	.is_enabled = lp3971_ldo_is_enabled,
+	.enable = lp3971_ldo_enable,
+	.disable = lp3971_ldo_disable,
+	.get_voltage_sel = lp3971_ldo_get_voltage_sel,
+	.set_voltage_sel = lp3971_ldo_set_voltage_sel,
+};
+
+static int lp3971_dcdc_is_enabled(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int buck = rdev_get_id(dev) - LP3971_DCDC1;
+	u16 mask = 1 << (buck * 2);
+	u16 val;
+
+	val = lp3971_reg_read(lp3971, LP3971_BUCK_VOL_ENABLE_REG);
+	return (val & mask) != 0;
+}
+
+static int lp3971_dcdc_enable(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int buck = rdev_get_id(dev) - LP3971_DCDC1;
+	u16 mask = 1 << (buck * 2);
+
+	return lp3971_set_bits(lp3971, LP3971_BUCK_VOL_ENABLE_REG, mask, mask);
+}
+
+static int lp3971_dcdc_disable(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int buck = rdev_get_id(dev) - LP3971_DCDC1;
+	u16 mask = 1 << (buck * 2);
+
+	return lp3971_set_bits(lp3971, LP3971_BUCK_VOL_ENABLE_REG, mask, 0);
+}
+
+static int lp3971_dcdc_get_voltage_sel(struct regulator_dev *dev)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int buck = rdev_get_id(dev) - LP3971_DCDC1;
+	u16 reg;
+
+	reg = lp3971_reg_read(lp3971, LP3971_BUCK_TARGET_VOL1_REG(buck));
+	reg &= BUCK_TARGET_VOL_MASK;
+
+	return reg;
+}
+
+static int lp3971_dcdc_set_voltage_sel(struct regulator_dev *dev,
+				       unsigned int selector)
+{
+	struct lp3971 *lp3971 = rdev_get_drvdata(dev);
+	int buck = rdev_get_id(dev) - LP3971_DCDC1;
+	int ret;
+
+	ret = lp3971_set_bits(lp3971, LP3971_BUCK_TARGET_VOL1_REG(buck),
+	       BUCK_TARGET_VOL_MASK, selector);
+	if (ret)
+		return ret;
+
+	ret = lp3971_set_bits(lp3971, LP3971_BUCK_VOL_CHANGE_REG,
+	       BUCK_VOL_CHANGE_FLAG_MASK << BUCK_VOL_CHANGE_SHIFT(buck),
+	       BUCK_VOL_CHANGE_FLAG_GO << BUCK_VOL_CHANGE_SHIFT(buck));
+	if (ret)
+		return ret;
+
+	return lp3971_set_bits(lp3971, LP3971_BUCK_VOL_CHANGE_REG,
+	       BUCK_VOL_CHANGE_FLAG_MASK << BUCK_VOL_CHANGE_SHIFT(buck),
+	       0 << BUCK_VOL_CHANGE_SHIFT(buck));
+}
+
+static const struct regulator_ops lp3971_dcdc_ops = {
+	.list_voltage = regulator_list_voltage_table,
+	.map_voltage = regulator_map_voltage_ascend,
+	.is_enabled = lp3971_dcdc_is_enabled,
+	.enable = lp3971_dcdc_enable,
+	.disable = lp3971_dcdc_disable,
+	.get_voltage_sel = lp3971_dcdc_get_voltage_sel,
+	.set_voltage_sel = lp3971_dcdc_set_voltage_sel,
+};
+
+static const struct regulator_desc regulators[] = {
+	{
+		.name = "LDO1",
+		.id = LP3971_LDO1,
+		.ops = &lp3971_ldo_ops,
+		.n_voltages = ARRAY_SIZE(ldo123_voltage_map),
+		.volt_table = ldo123_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "LDO2",
+		.id = LP3971_LDO2,
+		.ops = &lp3971_ldo_ops,
+		.n_voltages = ARRAY_SIZE(ldo123_voltage_map),
+		.volt_table = ldo123_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "LDO3",
+		.id = LP3971_LDO3,
+		.ops = &lp3971_ldo_ops,
+		.n_voltages = ARRAY_SIZE(ldo123_voltage_map),
+		.volt_table = ldo123_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "LDO4",
+		.id = LP3971_LDO4,
+		.ops = &lp3971_ldo_ops,
+		.n_voltages = ARRAY_SIZE(ldo45_voltage_map),
+		.volt_table = ldo45_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "LDO5",
+		.id = LP3971_LDO5,
+		.ops = &lp3971_ldo_ops,
+		.n_voltages = ARRAY_SIZE(ldo45_voltage_map),
+		.volt_table = ldo45_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "DCDC1",
+		.id = LP3971_DCDC1,
+		.ops = &lp3971_dcdc_ops,
+		.n_voltages = ARRAY_SIZE(buck_voltage_map),
+		.volt_table = buck_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "DCDC2",
+		.id = LP3971_DCDC2,
+		.ops = &lp3971_dcdc_ops,
+		.n_voltages = ARRAY_SIZE(buck_voltage_map),
+		.volt_table = buck_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+	{
+		.name = "DCDC3",
+		.id = LP3971_DCDC3,
+		.ops = &lp3971_dcdc_ops,
+		.n_voltages = ARRAY_SIZE(buck_voltage_map),
+		.volt_table = buck_voltage_map,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+	},
+};
+
+static int lp3971_i2c_read(struct i2c_client *i2c, char reg, int count,
+	u16 *dest)
+{
+	int ret;
+
+	if (count != 1)
+		return -EIO;
+	ret = i2c_smbus_read_byte_data(i2c, reg);
+	if (ret < 0)
+		return ret;
+
+	*dest = ret;
+	return 0;
+}
+
+static int lp3971_i2c_write(struct i2c_client *i2c, char reg, int count,
+	const u16 *src)
+{
+	if (count != 1)
+		return -EIO;
+	return i2c_smbus_write_byte_data(i2c, reg, *src);
+}
+
+static u8 lp3971_reg_read(struct lp3971 *lp3971, u8 reg)
+{
+	u16 val = 0;
+
+	mutex_lock(&lp3971->io_lock);
+
+	lp3971_i2c_read(lp3971->i2c, reg, 1, &val);
+
+	dev_dbg(lp3971->dev, "reg read 0x%02x -> 0x%02x\n", (int)reg,
+		(unsigned)val&0xff);
+
+	mutex_unlock(&lp3971->io_lock);
+
+	return val & 0xff;
+}
+
+static int lp3971_set_bits(struct lp3971 *lp3971, u8 reg, u16 mask, u16 val)
+{
+	u16 tmp;
+	int ret;
+
+	mutex_lock(&lp3971->io_lock);
+
+	ret = lp3971_i2c_read(lp3971->i2c, reg, 1, &tmp);
+	if (ret == 0) {
+		tmp = (tmp & ~mask) | val;
+		ret = lp3971_i2c_write(lp3971->i2c, reg, 1, &tmp);
+		dev_dbg(lp3971->dev, "reg write 0x%02x -> 0x%02x\n", (int)reg,
+			(unsigned)val&0xff);
+	}
+	mutex_unlock(&lp3971->io_lock);
+
+	return ret;
+}
+
+static int setup_regulators(struct lp3971 *lp3971,
+				      struct lp3971_platform_data *pdata)
+{
+	int i, err;
+
+	/* Instantiate the regulators */
+	for (i = 0; i < pdata->num_regulators; i++) {
+		struct regulator_config config = { };
+		struct lp3971_regulator_subdev *reg = &pdata->regulators[i];
+		struct regulator_dev *rdev;
+
+		config.dev = lp3971->dev;
+		config.init_data = reg->initdata;
+		config.driver_data = lp3971;
+
+		rdev = devm_regulator_register(lp3971->dev,
+					       &regulators[reg->id], &config);
+		if (IS_ERR(rdev)) {
+			err = PTR_ERR(rdev);
+			dev_err(lp3971->dev, "regulator init failed: %d\n",
+				err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+static int lp3971_i2c_probe(struct i2c_client *i2c)
+{
+	struct lp3971 *lp3971;
+	struct lp3971_platform_data *pdata = dev_get_platdata(&i2c->dev);
+	int ret;
+	u16 val;
+
+	if (!pdata) {
+		dev_dbg(&i2c->dev, "No platform init data supplied\n");
+		return -ENODEV;
+	}
+
+	lp3971 = devm_kzalloc(&i2c->dev, sizeof(struct lp3971), GFP_KERNEL);
+	if (lp3971 == NULL)
+		return -ENOMEM;
+
+	lp3971->i2c = i2c;
+	lp3971->dev = &i2c->dev;
+
+	mutex_init(&lp3971->io_lock);
+
+	/* Detect LP3971 */
+	ret = lp3971_i2c_read(i2c, LP3971_SYS_CONTROL1_REG, 1, &val);
+	if (ret == 0 && (val & SYS_CONTROL1_INIT_MASK) != SYS_CONTROL1_INIT_VAL)
+		ret = -ENODEV;
+	if (ret < 0) {
+		dev_err(&i2c->dev, "failed to detect device\n");
+		return ret;
+	}
+
+	ret = setup_regulators(lp3971, pdata);
+	if (ret < 0)
+		return ret;
+
+	i2c_set_clientdata(i2c, lp3971);
+	return 0;
+}
+
+static const struct i2c_device_id lp3971_i2c_id[] = {
+	{ "lp3971" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, lp3971_i2c_id);
+
+static struct i2c_driver lp3971_i2c_driver = {
+	.driver = {
+		.name = "LP3971",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.probe = lp3971_i2c_probe,
+	.id_table = lp3971_i2c_id,
+};
+
+module_i2c_driver(lp3971_i2c_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Marek Szyprowski <m.szyprowski@samsung.com>");
+MODULE_DESCRIPTION("LP3971 PMIC driver");