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, 529 insertions, 0 deletions

diff --git a/drivers/regulator/max8660.c b/drivers/regulator/max8660.c
new file mode 100644
index 000000000..ede17099b
--- /dev/null
+++ b/drivers/regulator/max8660.c
@@ -0,0 +1,529 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * max8660.c  --  Voltage regulation for the Maxim 8660/8661
+ *
+ * based on max1586.c and wm8400-regulator.c
+ *
+ * Copyright (C) 2009 Wolfram Sang, Pengutronix e.K.
+ *
+ * Some info:
+ *
+ * Datasheet: http://datasheets.maxim-ic.com/en/ds/MAX8660-MAX8661.pdf
+ *
+ * This chip is a bit nasty because it is a write-only device. Thus, the driver
+ * uses shadow registers to keep track of its values. The main problem appears
+ * to be the initialization: When Linux boots up, we cannot know if the chip is
+ * in the default state or not, so we would have to pass such information in
+ * platform_data. As this adds a bit of complexity to the driver, this is left
+ * out for now until it is really needed.
+ *
+ * [A|S|M]DTV1 registers are currently not used, but [A|S|M]DTV2.
+ *
+ * If the driver is feature complete, it might be worth to check if one set of
+ * functions for V3-V7 is sufficient. For maximum flexibility during
+ * development, they are separated for now.
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/slab.h>
+#include <linux/regulator/max8660.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regulator/of_regulator.h>
+
+#define MAX8660_DCDC_MIN_UV	 725000
+#define MAX8660_DCDC_MAX_UV	1800000
+#define MAX8660_DCDC_STEP	  25000
+#define MAX8660_DCDC_MAX_SEL	0x2b
+
+#define MAX8660_LDO5_MIN_UV	1700000
+#define MAX8660_LDO5_MAX_UV	2000000
+#define MAX8660_LDO5_STEP	  25000
+#define MAX8660_LDO5_MAX_SEL	0x0c
+
+#define MAX8660_LDO67_MIN_UV	1800000
+#define MAX8660_LDO67_MAX_UV	3300000
+#define MAX8660_LDO67_STEP	 100000
+#define MAX8660_LDO67_MAX_SEL	0x0f
+
+enum {
+	MAX8660_OVER1,
+	MAX8660_OVER2,
+	MAX8660_VCC1,
+	MAX8660_ADTV1,
+	MAX8660_ADTV2,
+	MAX8660_SDTV1,
+	MAX8660_SDTV2,
+	MAX8660_MDTV1,
+	MAX8660_MDTV2,
+	MAX8660_L12VCR,
+	MAX8660_FPWM,
+	MAX8660_N_REGS,	/* not a real register */
+};
+
+struct max8660 {
+	struct i2c_client *client;
+	u8 shadow_regs[MAX8660_N_REGS];		/* as chip is write only */
+};
+
+static int max8660_write(struct max8660 *max8660, u8 reg, u8 mask, u8 val)
+{
+	static const u8 max8660_addresses[MAX8660_N_REGS] = {
+	 0x10, 0x12, 0x20, 0x23, 0x24, 0x29, 0x2a, 0x32, 0x33, 0x39, 0x80
+	};
+
+	int ret;
+	u8 reg_val = (max8660->shadow_regs[reg] & mask) | val;
+
+	dev_vdbg(&max8660->client->dev, "Writing reg %02x with %02x\n",
+			max8660_addresses[reg], reg_val);
+
+	ret = i2c_smbus_write_byte_data(max8660->client,
+			max8660_addresses[reg], reg_val);
+	if (ret == 0)
+		max8660->shadow_regs[reg] = reg_val;
+
+	return ret;
+}
+
+
+/*
+ * DCDC functions
+ */
+
+static int max8660_dcdc_is_enabled(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 val = max8660->shadow_regs[MAX8660_OVER1];
+	u8 mask = (rdev_get_id(rdev) == MAX8660_V3) ? 1 : 4;
+
+	return !!(val & mask);
+}
+
+static int max8660_dcdc_enable(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 bit = (rdev_get_id(rdev) == MAX8660_V3) ? 1 : 4;
+
+	return max8660_write(max8660, MAX8660_OVER1, 0xff, bit);
+}
+
+static int max8660_dcdc_disable(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 mask = (rdev_get_id(rdev) == MAX8660_V3) ? ~1 : ~4;
+
+	return max8660_write(max8660, MAX8660_OVER1, mask, 0);
+}
+
+static int max8660_dcdc_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 reg = (rdev_get_id(rdev) == MAX8660_V3) ? MAX8660_ADTV2 : MAX8660_SDTV2;
+	u8 selector = max8660->shadow_regs[reg];
+
+	return selector;
+}
+
+static int max8660_dcdc_set_voltage_sel(struct regulator_dev *rdev,
+					unsigned int selector)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 reg, bits;
+	int ret;
+
+	reg = (rdev_get_id(rdev) == MAX8660_V3) ? MAX8660_ADTV2 : MAX8660_SDTV2;
+	ret = max8660_write(max8660, reg, 0, selector);
+	if (ret)
+		return ret;
+
+	/* Select target voltage register and activate regulation */
+	bits = (rdev_get_id(rdev) == MAX8660_V3) ? 0x03 : 0x30;
+	return max8660_write(max8660, MAX8660_VCC1, 0xff, bits);
+}
+
+static struct regulator_ops max8660_dcdc_ops = {
+	.is_enabled = max8660_dcdc_is_enabled,
+	.list_voltage = regulator_list_voltage_linear,
+	.map_voltage = regulator_map_voltage_linear,
+	.set_voltage_sel = max8660_dcdc_set_voltage_sel,
+	.get_voltage_sel = max8660_dcdc_get_voltage_sel,
+};
+
+
+/*
+ * LDO5 functions
+ */
+
+static int max8660_ldo5_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+
+	u8 selector = max8660->shadow_regs[MAX8660_MDTV2];
+	return selector;
+}
+
+static int max8660_ldo5_set_voltage_sel(struct regulator_dev *rdev,
+					unsigned int selector)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	int ret;
+
+	ret = max8660_write(max8660, MAX8660_MDTV2, 0, selector);
+	if (ret)
+		return ret;
+
+	/* Select target voltage register and activate regulation */
+	return max8660_write(max8660, MAX8660_VCC1, 0xff, 0xc0);
+}
+
+static const struct regulator_ops max8660_ldo5_ops = {
+	.list_voltage = regulator_list_voltage_linear,
+	.map_voltage = regulator_map_voltage_linear,
+	.set_voltage_sel = max8660_ldo5_set_voltage_sel,
+	.get_voltage_sel = max8660_ldo5_get_voltage_sel,
+};
+
+
+/*
+ * LDO67 functions
+ */
+
+static int max8660_ldo67_is_enabled(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 val = max8660->shadow_regs[MAX8660_OVER2];
+	u8 mask = (rdev_get_id(rdev) == MAX8660_V6) ? 2 : 4;
+
+	return !!(val & mask);
+}
+
+static int max8660_ldo67_enable(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 bit = (rdev_get_id(rdev) == MAX8660_V6) ? 2 : 4;
+
+	return max8660_write(max8660, MAX8660_OVER2, 0xff, bit);
+}
+
+static int max8660_ldo67_disable(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 mask = (rdev_get_id(rdev) == MAX8660_V6) ? ~2 : ~4;
+
+	return max8660_write(max8660, MAX8660_OVER2, mask, 0);
+}
+
+static int max8660_ldo67_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+	u8 shift = (rdev_get_id(rdev) == MAX8660_V6) ? 0 : 4;
+	u8 selector = (max8660->shadow_regs[MAX8660_L12VCR] >> shift) & 0xf;
+
+	return selector;
+}
+
+static int max8660_ldo67_set_voltage_sel(struct regulator_dev *rdev,
+					 unsigned int selector)
+{
+	struct max8660 *max8660 = rdev_get_drvdata(rdev);
+
+	if (rdev_get_id(rdev) == MAX8660_V6)
+		return max8660_write(max8660, MAX8660_L12VCR, 0xf0, selector);
+	else
+		return max8660_write(max8660, MAX8660_L12VCR, 0x0f,
+				     selector << 4);
+}
+
+static const struct regulator_ops max8660_ldo67_ops = {
+	.is_enabled = max8660_ldo67_is_enabled,
+	.enable = max8660_ldo67_enable,
+	.disable = max8660_ldo67_disable,
+	.list_voltage = regulator_list_voltage_linear,
+	.map_voltage = regulator_map_voltage_linear,
+	.get_voltage_sel = max8660_ldo67_get_voltage_sel,
+	.set_voltage_sel = max8660_ldo67_set_voltage_sel,
+};
+
+static const struct regulator_desc max8660_reg[] = {
+	{
+		.name = "V3(DCDC)",
+		.id = MAX8660_V3,
+		.ops = &max8660_dcdc_ops,
+		.type = REGULATOR_VOLTAGE,
+		.n_voltages = MAX8660_DCDC_MAX_SEL + 1,
+		.owner = THIS_MODULE,
+		.min_uV = MAX8660_DCDC_MIN_UV,
+		.uV_step = MAX8660_DCDC_STEP,
+	},
+	{
+		.name = "V4(DCDC)",
+		.id = MAX8660_V4,
+		.ops = &max8660_dcdc_ops,
+		.type = REGULATOR_VOLTAGE,
+		.n_voltages = MAX8660_DCDC_MAX_SEL + 1,
+		.owner = THIS_MODULE,
+		.min_uV = MAX8660_DCDC_MIN_UV,
+		.uV_step = MAX8660_DCDC_STEP,
+	},
+	{
+		.name = "V5(LDO)",
+		.id = MAX8660_V5,
+		.ops = &max8660_ldo5_ops,
+		.type = REGULATOR_VOLTAGE,
+		.n_voltages = MAX8660_LDO5_MAX_SEL + 1,
+		.owner = THIS_MODULE,
+		.min_uV = MAX8660_LDO5_MIN_UV,
+		.uV_step = MAX8660_LDO5_STEP,
+	},
+	{
+		.name = "V6(LDO)",
+		.id = MAX8660_V6,
+		.ops = &max8660_ldo67_ops,
+		.type = REGULATOR_VOLTAGE,
+		.n_voltages = MAX8660_LDO67_MAX_SEL + 1,
+		.owner = THIS_MODULE,
+		.min_uV = MAX8660_LDO67_MIN_UV,
+		.uV_step = MAX8660_LDO67_STEP,
+	},
+	{
+		.name = "V7(LDO)",
+		.id = MAX8660_V7,
+		.ops = &max8660_ldo67_ops,
+		.type = REGULATOR_VOLTAGE,
+		.n_voltages = MAX8660_LDO67_MAX_SEL + 1,
+		.owner = THIS_MODULE,
+		.min_uV = MAX8660_LDO67_MIN_UV,
+		.uV_step = MAX8660_LDO67_STEP,
+	},
+};
+
+enum {
+	MAX8660 = 0,
+	MAX8661 = 1,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id max8660_dt_ids[] = {
+	{ .compatible = "maxim,max8660", .data = (void *) MAX8660 },
+	{ .compatible = "maxim,max8661", .data = (void *) MAX8661 },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max8660_dt_ids);
+
+static int max8660_pdata_from_dt(struct device *dev,
+				 struct device_node **of_node,
+				 struct max8660_platform_data *pdata)
+{
+	int matched, i;
+	struct device_node *np;
+	struct max8660_subdev_data *sub;
+	struct of_regulator_match rmatch[ARRAY_SIZE(max8660_reg)] = { };
+
+	np = of_get_child_by_name(dev->of_node, "regulators");
+	if (!np) {
+		dev_err(dev, "missing 'regulators' subnode in DT\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(rmatch); i++)
+		rmatch[i].name = max8660_reg[i].name;
+
+	matched = of_regulator_match(dev, np, rmatch, ARRAY_SIZE(rmatch));
+	of_node_put(np);
+	if (matched <= 0)
+		return matched;
+
+	pdata->subdevs = devm_kcalloc(dev,
+				      matched,
+				      sizeof(struct max8660_subdev_data),
+				      GFP_KERNEL);
+	if (!pdata->subdevs)
+		return -ENOMEM;
+
+	pdata->num_subdevs = matched;
+	sub = pdata->subdevs;
+
+	for (i = 0; i < matched; i++) {
+		sub->id = i;
+		sub->name = rmatch[i].name;
+		sub->platform_data = rmatch[i].init_data;
+		of_node[i] = rmatch[i].of_node;
+		sub++;
+	}
+
+	return 0;
+}
+#else
+static inline int max8660_pdata_from_dt(struct device *dev,
+					struct device_node **of_node,
+					struct max8660_platform_data *pdata)
+{
+	return 0;
+}
+#endif
+
+static int max8660_probe(struct i2c_client *client)
+{
+	const struct i2c_device_id *i2c_id = i2c_client_get_device_id(client);
+	struct device *dev = &client->dev;
+	struct max8660_platform_data pdata_of, *pdata = dev_get_platdata(dev);
+	struct regulator_config config = { };
+	struct max8660 *max8660;
+	int boot_on, i, id, ret = -EINVAL;
+	struct device_node *of_node[MAX8660_V_END];
+	unsigned long type;
+
+	if (dev->of_node && !pdata) {
+		const struct of_device_id *id;
+
+		id = of_match_device(of_match_ptr(max8660_dt_ids), dev);
+		if (!id)
+			return -ENODEV;
+
+		ret = max8660_pdata_from_dt(dev, of_node, &pdata_of);
+		if (ret < 0)
+			return ret;
+
+		pdata = &pdata_of;
+		type = (unsigned long) id->data;
+	} else {
+		type = i2c_id->driver_data;
+		memset(of_node, 0, sizeof(of_node));
+	}
+
+	if (pdata->num_subdevs > MAX8660_V_END) {
+		dev_err(dev, "Too many regulators found!\n");
+		return -EINVAL;
+	}
+
+	max8660 = devm_kzalloc(dev, sizeof(struct max8660), GFP_KERNEL);
+	if (!max8660)
+		return -ENOMEM;
+
+	max8660->client = client;
+
+	if (pdata->en34_is_high) {
+		/* Simulate always on */
+		max8660->shadow_regs[MAX8660_OVER1] = 5;
+	} else {
+		/* Otherwise devices can be toggled via software */
+		max8660_dcdc_ops.enable = max8660_dcdc_enable;
+		max8660_dcdc_ops.disable = max8660_dcdc_disable;
+	}
+
+	/*
+	 * First, set up shadow registers to prevent glitches. As some
+	 * registers are shared between regulators, everything must be properly
+	 * set up for all regulators in advance.
+	 */
+	max8660->shadow_regs[MAX8660_ADTV1] =
+		max8660->shadow_regs[MAX8660_ADTV2] =
+		max8660->shadow_regs[MAX8660_SDTV1] =
+		max8660->shadow_regs[MAX8660_SDTV2] = 0x1b;
+	max8660->shadow_regs[MAX8660_MDTV1] =
+		max8660->shadow_regs[MAX8660_MDTV2] = 0x04;
+
+	for (i = 0; i < pdata->num_subdevs; i++) {
+
+		if (!pdata->subdevs[i].platform_data)
+			boot_on = false;
+		else
+			boot_on = pdata->subdevs[i].platform_data->constraints.boot_on;
+
+		switch (pdata->subdevs[i].id) {
+		case MAX8660_V3:
+			if (boot_on)
+				max8660->shadow_regs[MAX8660_OVER1] |= 1;
+			break;
+
+		case MAX8660_V4:
+			if (boot_on)
+				max8660->shadow_regs[MAX8660_OVER1] |= 4;
+			break;
+
+		case MAX8660_V5:
+			break;
+
+		case MAX8660_V6:
+			if (boot_on)
+				max8660->shadow_regs[MAX8660_OVER2] |= 2;
+			break;
+
+		case MAX8660_V7:
+			if (type == MAX8661) {
+				dev_err(dev, "Regulator not on this chip!\n");
+				return -EINVAL;
+			}
+
+			if (boot_on)
+				max8660->shadow_regs[MAX8660_OVER2] |= 4;
+			break;
+
+		default:
+			dev_err(dev, "invalid regulator %s\n",
+				 pdata->subdevs[i].name);
+			return ret;
+		}
+	}
+
+	/* Finally register devices */
+	for (i = 0; i < pdata->num_subdevs; i++) {
+		struct regulator_dev *rdev;
+
+		id = pdata->subdevs[i].id;
+
+		config.dev = dev;
+		config.init_data = pdata->subdevs[i].platform_data;
+		config.of_node = of_node[i];
+		config.driver_data = max8660;
+
+		rdev = devm_regulator_register(&client->dev,
+						  &max8660_reg[id], &config);
+		if (IS_ERR(rdev)) {
+			dev_err(&client->dev, "failed to register %s\n",
+				max8660_reg[id].name);
+			return PTR_ERR(rdev);
+		}
+	}
+
+	i2c_set_clientdata(client, max8660);
+	return 0;
+}
+
+static const struct i2c_device_id max8660_id[] = {
+	{ .name = "max8660", .driver_data = MAX8660 },
+	{ .name = "max8661", .driver_data = MAX8661 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max8660_id);
+
+static struct i2c_driver max8660_driver = {
+	.probe = max8660_probe,
+	.driver		= {
+		.name	= "max8660",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.id_table	= max8660_id,
+};
+
+static int __init max8660_init(void)
+{
+	return i2c_add_driver(&max8660_driver);
+}
+subsys_initcall(max8660_init);
+
+static void __exit max8660_exit(void)
+{
+	i2c_del_driver(&max8660_driver);
+}
+module_exit(max8660_exit);
+
+/* Module information */
+MODULE_DESCRIPTION("MAXIM 8660/8661 voltage regulator driver");
+MODULE_AUTHOR("Wolfram Sang");
+MODULE_LICENSE("GPL v2");