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, 565 insertions, 0 deletions

diff --git a/drivers/mfd/da903x.c b/drivers/mfd/da903x.c
new file mode 100644
index 000000000..e86b39de3
--- /dev/null
+++ b/drivers/mfd/da903x.c
@@ -0,0 +1,565 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Base driver for Dialog Semiconductor DA9030/DA9034
+ *
+ * Copyright (C) 2008 Compulab, Ltd.
+ *	Mike Rapoport <mike@compulab.co.il>
+ *
+ * Copyright (C) 2006-2008 Marvell International Ltd.
+ *	Eric Miao <eric.miao@marvell.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/mfd/da903x.h>
+#include <linux/slab.h>
+
+#define DA9030_CHIP_ID		0x00
+#define DA9030_EVENT_A		0x01
+#define DA9030_EVENT_B		0x02
+#define DA9030_EVENT_C		0x03
+#define DA9030_STATUS		0x04
+#define DA9030_IRQ_MASK_A	0x05
+#define DA9030_IRQ_MASK_B	0x06
+#define DA9030_IRQ_MASK_C	0x07
+#define DA9030_SYS_CTRL_A	0x08
+#define DA9030_SYS_CTRL_B	0x09
+#define DA9030_FAULT_LOG	0x0a
+
+#define DA9034_CHIP_ID		0x00
+#define DA9034_EVENT_A		0x01
+#define DA9034_EVENT_B		0x02
+#define DA9034_EVENT_C		0x03
+#define DA9034_EVENT_D		0x04
+#define DA9034_STATUS_A		0x05
+#define DA9034_STATUS_B		0x06
+#define DA9034_IRQ_MASK_A	0x07
+#define DA9034_IRQ_MASK_B	0x08
+#define DA9034_IRQ_MASK_C	0x09
+#define DA9034_IRQ_MASK_D	0x0a
+#define DA9034_SYS_CTRL_A	0x0b
+#define DA9034_SYS_CTRL_B	0x0c
+#define DA9034_FAULT_LOG	0x0d
+
+struct da903x_chip;
+
+struct da903x_chip_ops {
+	int	(*init_chip)(struct da903x_chip *);
+	int	(*unmask_events)(struct da903x_chip *, unsigned int events);
+	int	(*mask_events)(struct da903x_chip *, unsigned int events);
+	int	(*read_events)(struct da903x_chip *, unsigned int *events);
+	int	(*read_status)(struct da903x_chip *, unsigned int *status);
+};
+
+struct da903x_chip {
+	struct i2c_client	*client;
+	struct device		*dev;
+	const struct da903x_chip_ops *ops;
+
+	int			type;
+	uint32_t		events_mask;
+
+	struct mutex		lock;
+	struct work_struct	irq_work;
+
+	struct blocking_notifier_head notifier_list;
+};
+
+static inline int __da903x_read(struct i2c_client *client,
+				int reg, uint8_t *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(client, reg);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed reading at 0x%02x\n", reg);
+		return ret;
+	}
+
+	*val = (uint8_t)ret;
+	return 0;
+}
+
+static inline int __da903x_reads(struct i2c_client *client, int reg,
+				 int len, uint8_t *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_i2c_block_data(client, reg, len, val);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed reading from 0x%02x\n", reg);
+		return ret;
+	}
+	return 0;
+}
+
+static inline int __da903x_write(struct i2c_client *client,
+				 int reg, uint8_t val)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, reg, val);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed writing 0x%02x to 0x%02x\n",
+				val, reg);
+		return ret;
+	}
+	return 0;
+}
+
+static inline int __da903x_writes(struct i2c_client *client, int reg,
+				  int len, uint8_t *val)
+{
+	int ret;
+
+	ret = i2c_smbus_write_i2c_block_data(client, reg, len, val);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed writings to 0x%02x\n", reg);
+		return ret;
+	}
+	return 0;
+}
+
+int da903x_register_notifier(struct device *dev, struct notifier_block *nb,
+				unsigned int events)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+
+	chip->ops->unmask_events(chip, events);
+	return blocking_notifier_chain_register(&chip->notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(da903x_register_notifier);
+
+int da903x_unregister_notifier(struct device *dev, struct notifier_block *nb,
+				unsigned int events)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+
+	chip->ops->mask_events(chip, events);
+	return blocking_notifier_chain_unregister(&chip->notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(da903x_unregister_notifier);
+
+int da903x_write(struct device *dev, int reg, uint8_t val)
+{
+	return __da903x_write(to_i2c_client(dev), reg, val);
+}
+EXPORT_SYMBOL_GPL(da903x_write);
+
+int da903x_writes(struct device *dev, int reg, int len, uint8_t *val)
+{
+	return __da903x_writes(to_i2c_client(dev), reg, len, val);
+}
+EXPORT_SYMBOL_GPL(da903x_writes);
+
+int da903x_read(struct device *dev, int reg, uint8_t *val)
+{
+	return __da903x_read(to_i2c_client(dev), reg, val);
+}
+EXPORT_SYMBOL_GPL(da903x_read);
+
+int da903x_reads(struct device *dev, int reg, int len, uint8_t *val)
+{
+	return __da903x_reads(to_i2c_client(dev), reg, len, val);
+}
+EXPORT_SYMBOL_GPL(da903x_reads);
+
+int da903x_set_bits(struct device *dev, int reg, uint8_t bit_mask)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+	uint8_t reg_val;
+	int ret = 0;
+
+	mutex_lock(&chip->lock);
+
+	ret = __da903x_read(chip->client, reg, &reg_val);
+	if (ret)
+		goto out;
+
+	if ((reg_val & bit_mask) != bit_mask) {
+		reg_val |= bit_mask;
+		ret = __da903x_write(chip->client, reg, reg_val);
+	}
+out:
+	mutex_unlock(&chip->lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(da903x_set_bits);
+
+int da903x_clr_bits(struct device *dev, int reg, uint8_t bit_mask)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+	uint8_t reg_val;
+	int ret = 0;
+
+	mutex_lock(&chip->lock);
+
+	ret = __da903x_read(chip->client, reg, &reg_val);
+	if (ret)
+		goto out;
+
+	if (reg_val & bit_mask) {
+		reg_val &= ~bit_mask;
+		ret = __da903x_write(chip->client, reg, reg_val);
+	}
+out:
+	mutex_unlock(&chip->lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(da903x_clr_bits);
+
+int da903x_update(struct device *dev, int reg, uint8_t val, uint8_t mask)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+	uint8_t reg_val;
+	int ret = 0;
+
+	mutex_lock(&chip->lock);
+
+	ret = __da903x_read(chip->client, reg, &reg_val);
+	if (ret)
+		goto out;
+
+	if ((reg_val & mask) != val) {
+		reg_val = (reg_val & ~mask) | val;
+		ret = __da903x_write(chip->client, reg, reg_val);
+	}
+out:
+	mutex_unlock(&chip->lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(da903x_update);
+
+int da903x_query_status(struct device *dev, unsigned int sbits)
+{
+	struct da903x_chip *chip = dev_get_drvdata(dev);
+	unsigned int status = 0;
+
+	chip->ops->read_status(chip, &status);
+	return ((status & sbits) == sbits);
+}
+EXPORT_SYMBOL(da903x_query_status);
+
+static int da9030_init_chip(struct da903x_chip *chip)
+{
+	uint8_t chip_id;
+	int err;
+
+	err = __da903x_read(chip->client, DA9030_CHIP_ID, &chip_id);
+	if (err)
+		return err;
+
+	err = __da903x_write(chip->client, DA9030_SYS_CTRL_A, 0xE8);
+	if (err)
+		return err;
+
+	dev_info(chip->dev, "DA9030 (CHIP ID: 0x%02x) detected\n", chip_id);
+	return 0;
+}
+
+static int da9030_unmask_events(struct da903x_chip *chip, unsigned int events)
+{
+	uint8_t v[3];
+
+	chip->events_mask &= ~events;
+
+	v[0] = (chip->events_mask & 0xff);
+	v[1] = (chip->events_mask >> 8) & 0xff;
+	v[2] = (chip->events_mask >> 16) & 0xff;
+
+	return __da903x_writes(chip->client, DA9030_IRQ_MASK_A, 3, v);
+}
+
+static int da9030_mask_events(struct da903x_chip *chip, unsigned int events)
+{
+	uint8_t v[3];
+
+	chip->events_mask |= events;
+
+	v[0] = (chip->events_mask & 0xff);
+	v[1] = (chip->events_mask >> 8) & 0xff;
+	v[2] = (chip->events_mask >> 16) & 0xff;
+
+	return __da903x_writes(chip->client, DA9030_IRQ_MASK_A, 3, v);
+}
+
+static int da9030_read_events(struct da903x_chip *chip, unsigned int *events)
+{
+	uint8_t v[3] = {0, 0, 0};
+	int ret;
+
+	ret = __da903x_reads(chip->client, DA9030_EVENT_A, 3, v);
+	if (ret < 0)
+		return ret;
+
+	*events = (v[2] << 16) | (v[1] << 8) | v[0];
+	return 0;
+}
+
+static int da9030_read_status(struct da903x_chip *chip, unsigned int *status)
+{
+	return __da903x_read(chip->client, DA9030_STATUS, (uint8_t *)status);
+}
+
+static int da9034_init_chip(struct da903x_chip *chip)
+{
+	uint8_t chip_id;
+	int err;
+
+	err = __da903x_read(chip->client, DA9034_CHIP_ID, &chip_id);
+	if (err)
+		return err;
+
+	err = __da903x_write(chip->client, DA9034_SYS_CTRL_A, 0xE8);
+	if (err)
+		return err;
+
+	/* avoid SRAM power off during sleep*/
+	__da903x_write(chip->client, 0x10, 0x07);
+	__da903x_write(chip->client, 0x11, 0xff);
+	__da903x_write(chip->client, 0x12, 0xff);
+
+	/* Enable the ONKEY power down functionality */
+	__da903x_write(chip->client, DA9034_SYS_CTRL_B, 0x20);
+	__da903x_write(chip->client, DA9034_SYS_CTRL_A, 0x60);
+
+	/* workaround to make LEDs work */
+	__da903x_write(chip->client, 0x90, 0x01);
+	__da903x_write(chip->client, 0xB0, 0x08);
+
+	/* make ADTV1 and SDTV1 effective */
+	__da903x_write(chip->client, 0x20, 0x00);
+
+	dev_info(chip->dev, "DA9034 (CHIP ID: 0x%02x) detected\n", chip_id);
+	return 0;
+}
+
+static int da9034_unmask_events(struct da903x_chip *chip, unsigned int events)
+{
+	uint8_t v[4];
+
+	chip->events_mask &= ~events;
+
+	v[0] = (chip->events_mask & 0xff);
+	v[1] = (chip->events_mask >> 8) & 0xff;
+	v[2] = (chip->events_mask >> 16) & 0xff;
+	v[3] = (chip->events_mask >> 24) & 0xff;
+
+	return __da903x_writes(chip->client, DA9034_IRQ_MASK_A, 4, v);
+}
+
+static int da9034_mask_events(struct da903x_chip *chip, unsigned int events)
+{
+	uint8_t v[4];
+
+	chip->events_mask |= events;
+
+	v[0] = (chip->events_mask & 0xff);
+	v[1] = (chip->events_mask >> 8) & 0xff;
+	v[2] = (chip->events_mask >> 16) & 0xff;
+	v[3] = (chip->events_mask >> 24) & 0xff;
+
+	return __da903x_writes(chip->client, DA9034_IRQ_MASK_A, 4, v);
+}
+
+static int da9034_read_events(struct da903x_chip *chip, unsigned int *events)
+{
+	uint8_t v[4] = {0, 0, 0, 0};
+	int ret;
+
+	ret = __da903x_reads(chip->client, DA9034_EVENT_A, 4, v);
+	if (ret < 0)
+		return ret;
+
+	*events = (v[3] << 24) | (v[2] << 16) | (v[1] << 8) | v[0];
+	return 0;
+}
+
+static int da9034_read_status(struct da903x_chip *chip, unsigned int *status)
+{
+	uint8_t v[2] = {0, 0};
+	int ret = 0;
+
+	ret = __da903x_reads(chip->client, DA9034_STATUS_A, 2, v);
+	if (ret)
+		return ret;
+
+	*status = (v[1] << 8) | v[0];
+	return 0;
+}
+
+static void da903x_irq_work(struct work_struct *work)
+{
+	struct da903x_chip *chip =
+		container_of(work, struct da903x_chip, irq_work);
+	unsigned int events = 0;
+
+	while (1) {
+		if (chip->ops->read_events(chip, &events))
+			break;
+
+		events &= ~chip->events_mask;
+		if (events == 0)
+			break;
+
+		blocking_notifier_call_chain(
+				&chip->notifier_list, events, NULL);
+	}
+	enable_irq(chip->client->irq);
+}
+
+static irqreturn_t da903x_irq_handler(int irq, void *data)
+{
+	struct da903x_chip *chip = data;
+
+	disable_irq_nosync(irq);
+	(void)schedule_work(&chip->irq_work);
+
+	return IRQ_HANDLED;
+}
+
+static const struct da903x_chip_ops da903x_ops[] = {
+	[0] = {
+		.init_chip	= da9030_init_chip,
+		.unmask_events	= da9030_unmask_events,
+		.mask_events	= da9030_mask_events,
+		.read_events	= da9030_read_events,
+		.read_status	= da9030_read_status,
+	},
+	[1] = {
+		.init_chip	= da9034_init_chip,
+		.unmask_events	= da9034_unmask_events,
+		.mask_events	= da9034_mask_events,
+		.read_events	= da9034_read_events,
+		.read_status	= da9034_read_status,
+	}
+};
+
+static const struct i2c_device_id da903x_id_table[] = {
+	{ "da9030", 0 },
+	{ "da9034", 1 },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, da903x_id_table);
+
+static int __remove_subdev(struct device *dev, void *unused)
+{
+	platform_device_unregister(to_platform_device(dev));
+	return 0;
+}
+
+static int da903x_remove_subdevs(struct da903x_chip *chip)
+{
+	return device_for_each_child(chip->dev, NULL, __remove_subdev);
+}
+
+static int da903x_add_subdevs(struct da903x_chip *chip,
+					struct da903x_platform_data *pdata)
+{
+	struct da903x_subdev_info *subdev;
+	struct platform_device *pdev;
+	int i, ret = 0;
+
+	for (i = 0; i < pdata->num_subdevs; i++) {
+		subdev = &pdata->subdevs[i];
+
+		pdev = platform_device_alloc(subdev->name, subdev->id);
+		if (!pdev) {
+			ret = -ENOMEM;
+			goto failed;
+		}
+
+		pdev->dev.parent = chip->dev;
+		pdev->dev.platform_data = subdev->platform_data;
+
+		ret = platform_device_add(pdev);
+		if (ret) {
+			platform_device_put(pdev);
+			goto failed;
+		}
+	}
+	return 0;
+
+failed:
+	da903x_remove_subdevs(chip);
+	return ret;
+}
+
+static int da903x_probe(struct i2c_client *client)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(client);
+	struct da903x_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct da903x_chip *chip;
+	unsigned int tmp;
+	int ret;
+
+	chip = devm_kzalloc(&client->dev, sizeof(struct da903x_chip),
+				GFP_KERNEL);
+	if (chip == NULL)
+		return -ENOMEM;
+
+	chip->client = client;
+	chip->dev = &client->dev;
+	chip->ops = &da903x_ops[id->driver_data];
+
+	mutex_init(&chip->lock);
+	INIT_WORK(&chip->irq_work, da903x_irq_work);
+	BLOCKING_INIT_NOTIFIER_HEAD(&chip->notifier_list);
+
+	i2c_set_clientdata(client, chip);
+
+	ret = chip->ops->init_chip(chip);
+	if (ret)
+		return ret;
+
+	/* mask and clear all IRQs */
+	chip->events_mask = 0xffffffff;
+	chip->ops->mask_events(chip, chip->events_mask);
+	chip->ops->read_events(chip, &tmp);
+
+	ret = devm_request_irq(&client->dev, client->irq, da903x_irq_handler,
+			IRQF_TRIGGER_FALLING,
+			"da903x", chip);
+	if (ret) {
+		dev_err(&client->dev, "failed to request irq %d\n",
+				client->irq);
+		return ret;
+	}
+
+	return da903x_add_subdevs(chip, pdata);
+}
+
+static void da903x_remove(struct i2c_client *client)
+{
+	struct da903x_chip *chip = i2c_get_clientdata(client);
+
+	da903x_remove_subdevs(chip);
+}
+
+static struct i2c_driver da903x_driver = {
+	.driver	= {
+		.name	= "da903x",
+	},
+	.probe		= da903x_probe,
+	.remove		= da903x_remove,
+	.id_table	= da903x_id_table,
+};
+
+static int __init da903x_init(void)
+{
+	return i2c_add_driver(&da903x_driver);
+}
+subsys_initcall(da903x_init);
+
+static void __exit da903x_exit(void)
+{
+	i2c_del_driver(&da903x_driver);
+}
+module_exit(da903x_exit);
+
+MODULE_DESCRIPTION("PMIC Driver for Dialog Semiconductor DA9034");
+MODULE_AUTHOR("Eric Miao <eric.miao@marvell.com>");
+MODULE_AUTHOR("Mike Rapoport <mike@compulab.co.il>");