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, 422 insertions, 0 deletions

diff --git a/drivers/mfd/tps65217.c b/drivers/mfd/tps65217.c
new file mode 100644
index 000000000..c240fac0e
--- /dev/null
+++ b/drivers/mfd/tps65217.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * tps65217.c
+ *
+ * TPS65217 chip family multi-function driver
+ *
+ * Copyright (C) 2011 Texas Instruments Incorporated - https://www.ti.com/
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <linux/mfd/core.h>
+#include <linux/mfd/tps65217.h>
+
+static const struct resource charger_resources[] = {
+	DEFINE_RES_IRQ_NAMED(TPS65217_IRQ_AC, "AC"),
+	DEFINE_RES_IRQ_NAMED(TPS65217_IRQ_USB, "USB"),
+};
+
+static const struct resource pb_resources[] = {
+	DEFINE_RES_IRQ_NAMED(TPS65217_IRQ_PB, "PB"),
+};
+
+static void tps65217_irq_lock(struct irq_data *data)
+{
+	struct tps65217 *tps = irq_data_get_irq_chip_data(data);
+
+	mutex_lock(&tps->irq_lock);
+}
+
+static void tps65217_irq_sync_unlock(struct irq_data *data)
+{
+	struct tps65217 *tps = irq_data_get_irq_chip_data(data);
+	int ret;
+
+	ret = tps65217_set_bits(tps, TPS65217_REG_INT, TPS65217_INT_MASK,
+				tps->irq_mask, TPS65217_PROTECT_NONE);
+	if (ret != 0)
+		dev_err(tps->dev, "Failed to sync IRQ masks\n");
+
+	mutex_unlock(&tps->irq_lock);
+}
+
+static void tps65217_irq_enable(struct irq_data *data)
+{
+	struct tps65217 *tps = irq_data_get_irq_chip_data(data);
+	u8 mask = BIT(data->hwirq) << TPS65217_INT_SHIFT;
+
+	tps->irq_mask &= ~mask;
+}
+
+static void tps65217_irq_disable(struct irq_data *data)
+{
+	struct tps65217 *tps = irq_data_get_irq_chip_data(data);
+	u8 mask = BIT(data->hwirq) << TPS65217_INT_SHIFT;
+
+	tps->irq_mask |= mask;
+}
+
+static struct irq_chip tps65217_irq_chip = {
+	.name			= "tps65217",
+	.irq_bus_lock		= tps65217_irq_lock,
+	.irq_bus_sync_unlock	= tps65217_irq_sync_unlock,
+	.irq_enable		= tps65217_irq_enable,
+	.irq_disable		= tps65217_irq_disable,
+};
+
+static struct mfd_cell tps65217s[] = {
+	{
+		.name = "tps65217-pmic",
+		.of_compatible = "ti,tps65217-pmic",
+	},
+	{
+		.name = "tps65217-bl",
+		.of_compatible = "ti,tps65217-bl",
+	},
+	{
+		.name = "tps65217-charger",
+		.num_resources = ARRAY_SIZE(charger_resources),
+		.resources = charger_resources,
+		.of_compatible = "ti,tps65217-charger",
+	},
+	{
+		.name = "tps65217-pwrbutton",
+		.num_resources = ARRAY_SIZE(pb_resources),
+		.resources = pb_resources,
+		.of_compatible = "ti,tps65217-pwrbutton",
+	},
+};
+
+static irqreturn_t tps65217_irq_thread(int irq, void *data)
+{
+	struct tps65217 *tps = data;
+	unsigned int status;
+	bool handled = false;
+	int i;
+	int ret;
+
+	ret = tps65217_reg_read(tps, TPS65217_REG_INT, &status);
+	if (ret < 0) {
+		dev_err(tps->dev, "Failed to read IRQ status: %d\n",
+			ret);
+		return IRQ_NONE;
+	}
+
+	for (i = 0; i < TPS65217_NUM_IRQ; i++) {
+		if (status & BIT(i)) {
+			handle_nested_irq(irq_find_mapping(tps->irq_domain, i));
+			handled = true;
+		}
+	}
+
+	if (handled)
+		return IRQ_HANDLED;
+
+	return IRQ_NONE;
+}
+
+static int tps65217_irq_map(struct irq_domain *h, unsigned int virq,
+			irq_hw_number_t hw)
+{
+	struct tps65217 *tps = h->host_data;
+
+	irq_set_chip_data(virq, tps);
+	irq_set_chip_and_handler(virq, &tps65217_irq_chip, handle_edge_irq);
+	irq_set_nested_thread(virq, 1);
+	irq_set_parent(virq, tps->irq);
+	irq_set_noprobe(virq);
+
+	return 0;
+}
+
+static const struct irq_domain_ops tps65217_irq_domain_ops = {
+	.map = tps65217_irq_map,
+};
+
+static int tps65217_irq_init(struct tps65217 *tps, int irq)
+{
+	int ret;
+
+	mutex_init(&tps->irq_lock);
+	tps->irq = irq;
+
+	/* Mask all interrupt sources */
+	tps->irq_mask = TPS65217_INT_MASK;
+	tps65217_set_bits(tps, TPS65217_REG_INT, TPS65217_INT_MASK,
+			  TPS65217_INT_MASK, TPS65217_PROTECT_NONE);
+
+	tps->irq_domain = irq_domain_create_linear(dev_fwnode(tps->dev), TPS65217_NUM_IRQ,
+						   &tps65217_irq_domain_ops, tps);
+	if (!tps->irq_domain) {
+		dev_err(tps->dev, "Could not create IRQ domain\n");
+		return -ENOMEM;
+	}
+
+	ret = devm_request_threaded_irq(tps->dev, irq, NULL,
+					tps65217_irq_thread, IRQF_ONESHOT,
+					"tps65217-irq", tps);
+	if (ret) {
+		dev_err(tps->dev, "Failed to request IRQ %d: %d\n",
+			irq, ret);
+		return ret;
+	}
+
+	enable_irq_wake(irq);
+
+	return 0;
+}
+
+/**
+ * tps65217_reg_read: Read a single tps65217 register.
+ *
+ * @tps: Device to read from.
+ * @reg: Register to read.
+ * @val: Contians the value
+ */
+int tps65217_reg_read(struct tps65217 *tps, unsigned int reg,
+			unsigned int *val)
+{
+	return regmap_read(tps->regmap, reg, val);
+}
+EXPORT_SYMBOL_GPL(tps65217_reg_read);
+
+/**
+ * tps65217_reg_write: Write a single tps65217 register.
+ *
+ * @tps: Device to write to.
+ * @reg: Register to write to.
+ * @val: Value to write.
+ * @level: Password protected level
+ */
+int tps65217_reg_write(struct tps65217 *tps, unsigned int reg,
+			unsigned int val, unsigned int level)
+{
+	int ret;
+	unsigned int xor_reg_val;
+
+	switch (level) {
+	case TPS65217_PROTECT_NONE:
+		return regmap_write(tps->regmap, reg, val);
+	case TPS65217_PROTECT_L1:
+		xor_reg_val = reg ^ TPS65217_PASSWORD_REGS_UNLOCK;
+		ret = regmap_write(tps->regmap, TPS65217_REG_PASSWORD,
+							xor_reg_val);
+		if (ret < 0)
+			return ret;
+
+		return regmap_write(tps->regmap, reg, val);
+	case TPS65217_PROTECT_L2:
+		xor_reg_val = reg ^ TPS65217_PASSWORD_REGS_UNLOCK;
+		ret = regmap_write(tps->regmap, TPS65217_REG_PASSWORD,
+							xor_reg_val);
+		if (ret < 0)
+			return ret;
+		ret = regmap_write(tps->regmap, reg, val);
+		if (ret < 0)
+			return ret;
+		ret = regmap_write(tps->regmap, TPS65217_REG_PASSWORD,
+							xor_reg_val);
+		if (ret < 0)
+			return ret;
+		return regmap_write(tps->regmap, reg, val);
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL_GPL(tps65217_reg_write);
+
+/**
+ * tps65217_update_bits: Modify bits w.r.t mask, val and level.
+ *
+ * @tps: Device to write to.
+ * @reg: Register to read-write to.
+ * @mask: Mask.
+ * @val: Value to write.
+ * @level: Password protected level
+ */
+static int tps65217_update_bits(struct tps65217 *tps, unsigned int reg,
+		unsigned int mask, unsigned int val, unsigned int level)
+{
+	int ret;
+	unsigned int data;
+
+	ret = tps65217_reg_read(tps, reg, &data);
+	if (ret) {
+		dev_err(tps->dev, "Read from reg 0x%x failed\n", reg);
+		return ret;
+	}
+
+	data &= ~mask;
+	data |= val & mask;
+
+	ret = tps65217_reg_write(tps, reg, data, level);
+	if (ret)
+		dev_err(tps->dev, "Write for reg 0x%x failed\n", reg);
+
+	return ret;
+}
+
+int tps65217_set_bits(struct tps65217 *tps, unsigned int reg,
+		unsigned int mask, unsigned int val, unsigned int level)
+{
+	return tps65217_update_bits(tps, reg, mask, val, level);
+}
+EXPORT_SYMBOL_GPL(tps65217_set_bits);
+
+int tps65217_clear_bits(struct tps65217 *tps, unsigned int reg,
+		unsigned int mask, unsigned int level)
+{
+	return tps65217_update_bits(tps, reg, mask, 0, level);
+}
+EXPORT_SYMBOL_GPL(tps65217_clear_bits);
+
+static bool tps65217_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case TPS65217_REG_INT:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config tps65217_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = TPS65217_REG_MAX,
+	.volatile_reg = tps65217_volatile_reg,
+};
+
+static const struct of_device_id tps65217_of_match[] = {
+	{ .compatible = "ti,tps65217"},
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, tps65217_of_match);
+
+static int tps65217_probe(struct i2c_client *client)
+{
+	struct tps65217 *tps;
+	unsigned int version;
+	bool status_off = false;
+	int ret;
+
+	status_off = of_property_read_bool(client->dev.of_node,
+					   "ti,pmic-shutdown-controller");
+
+	tps = devm_kzalloc(&client->dev, sizeof(*tps), GFP_KERNEL);
+	if (!tps)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, tps);
+	tps->dev = &client->dev;
+
+	tps->regmap = devm_regmap_init_i2c(client, &tps65217_regmap_config);
+	if (IS_ERR(tps->regmap)) {
+		ret = PTR_ERR(tps->regmap);
+		dev_err(tps->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	if (client->irq) {
+		tps65217_irq_init(tps, client->irq);
+	} else {
+		int i;
+
+		/* Don't tell children about IRQ resources which won't fire */
+		for (i = 0; i < ARRAY_SIZE(tps65217s); i++)
+			tps65217s[i].num_resources = 0;
+	}
+
+	ret = devm_mfd_add_devices(tps->dev, -1, tps65217s,
+				   ARRAY_SIZE(tps65217s), NULL, 0,
+				   tps->irq_domain);
+	if (ret < 0) {
+		dev_err(tps->dev, "mfd_add_devices failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = tps65217_reg_read(tps, TPS65217_REG_CHIPID, &version);
+	if (ret < 0) {
+		dev_err(tps->dev, "Failed to read revision register: %d\n",
+			ret);
+		return ret;
+	}
+
+	/* Set the PMIC to shutdown on PWR_EN toggle */
+	if (status_off) {
+		ret = tps65217_set_bits(tps, TPS65217_REG_STATUS,
+				TPS65217_STATUS_OFF, TPS65217_STATUS_OFF,
+				TPS65217_PROTECT_NONE);
+		if (ret)
+			dev_warn(tps->dev, "unable to set the status OFF\n");
+	}
+
+	dev_info(tps->dev, "TPS65217 ID %#x version 1.%d\n",
+			(version & TPS65217_CHIPID_CHIP_MASK) >> 4,
+			version & TPS65217_CHIPID_REV_MASK);
+
+	return 0;
+}
+
+static void tps65217_remove(struct i2c_client *client)
+{
+	struct tps65217 *tps = i2c_get_clientdata(client);
+	unsigned int virq;
+	int i;
+
+	for (i = 0; i < TPS65217_NUM_IRQ; i++) {
+		virq = irq_find_mapping(tps->irq_domain, i);
+		if (virq)
+			irq_dispose_mapping(virq);
+	}
+
+	irq_domain_remove(tps->irq_domain);
+	tps->irq_domain = NULL;
+}
+
+static const struct i2c_device_id tps65217_id_table[] = {
+	{"tps65217", TPS65217},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, tps65217_id_table);
+
+static struct i2c_driver tps65217_driver = {
+	.driver		= {
+		.name	= "tps65217",
+		.of_match_table = tps65217_of_match,
+	},
+	.id_table	= tps65217_id_table,
+	.probe		= tps65217_probe,
+	.remove		= tps65217_remove,
+};
+
+static int __init tps65217_init(void)
+{
+	return i2c_add_driver(&tps65217_driver);
+}
+subsys_initcall(tps65217_init);
+
+static void __exit tps65217_exit(void)
+{
+	i2c_del_driver(&tps65217_driver);
+}
+module_exit(tps65217_exit);
+
+MODULE_AUTHOR("AnilKumar Ch <anilkumar@ti.com>");
+MODULE_DESCRIPTION("TPS65217 chip family multi-function driver");
+MODULE_LICENSE("GPL v2");