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, 279 insertions, 0 deletions

diff --git a/drivers/mfd/qcom-pm8008.c b/drivers/mfd/qcom-pm8008.c
new file mode 100644
index 000000000..60204cc9a
--- /dev/null
+++ b/drivers/mfd/qcom-pm8008.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/bitops.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define I2C_INTR_STATUS_BASE		0x0550
+#define INT_RT_STS_OFFSET		0x10
+#define INT_SET_TYPE_OFFSET		0x11
+#define INT_POL_HIGH_OFFSET		0x12
+#define INT_POL_LOW_OFFSET		0x13
+#define INT_LATCHED_CLR_OFFSET		0x14
+#define INT_EN_SET_OFFSET		0x15
+#define INT_EN_CLR_OFFSET		0x16
+#define INT_LATCHED_STS_OFFSET		0x18
+
+enum {
+	PM8008_MISC,
+	PM8008_TEMP_ALARM,
+	PM8008_GPIO1,
+	PM8008_GPIO2,
+	PM8008_NUM_PERIPHS,
+};
+
+#define PM8008_PERIPH_0_BASE	0x900
+#define PM8008_PERIPH_1_BASE	0x2400
+#define PM8008_PERIPH_2_BASE	0xc000
+#define PM8008_PERIPH_3_BASE	0xc100
+
+#define PM8008_TEMP_ALARM_ADDR	PM8008_PERIPH_1_BASE
+#define PM8008_GPIO1_ADDR	PM8008_PERIPH_2_BASE
+#define PM8008_GPIO2_ADDR	PM8008_PERIPH_3_BASE
+
+/* PM8008 IRQ numbers */
+#define PM8008_IRQ_MISC_UVLO	0
+#define PM8008_IRQ_MISC_OVLO	1
+#define PM8008_IRQ_MISC_OTST2	2
+#define PM8008_IRQ_MISC_OTST3	3
+#define PM8008_IRQ_MISC_LDO_OCP	4
+#define PM8008_IRQ_TEMP_ALARM	5
+#define PM8008_IRQ_GPIO1	6
+#define PM8008_IRQ_GPIO2	7
+
+enum {
+	SET_TYPE_INDEX,
+	POLARITY_HI_INDEX,
+	POLARITY_LO_INDEX,
+};
+
+static const unsigned int pm8008_config_regs[] = {
+	INT_SET_TYPE_OFFSET,
+	INT_POL_HIGH_OFFSET,
+	INT_POL_LOW_OFFSET,
+};
+
+#define _IRQ(_irq, _off, _mask, _types)			\
+	[_irq] = {					\
+		.reg_offset = (_off),			\
+		.mask = (_mask),			\
+		.type = {				\
+			.type_reg_offset = (_off),	\
+			.types_supported = (_types),	\
+		},					\
+	}
+
+static const struct regmap_irq pm8008_irqs[] = {
+	_IRQ(PM8008_IRQ_MISC_UVLO,    PM8008_MISC,	BIT(0), IRQ_TYPE_EDGE_RISING),
+	_IRQ(PM8008_IRQ_MISC_OVLO,    PM8008_MISC,	BIT(1), IRQ_TYPE_EDGE_RISING),
+	_IRQ(PM8008_IRQ_MISC_OTST2,   PM8008_MISC,	BIT(2), IRQ_TYPE_EDGE_RISING),
+	_IRQ(PM8008_IRQ_MISC_OTST3,   PM8008_MISC,	BIT(3), IRQ_TYPE_EDGE_RISING),
+	_IRQ(PM8008_IRQ_MISC_LDO_OCP, PM8008_MISC,	BIT(4), IRQ_TYPE_EDGE_RISING),
+	_IRQ(PM8008_IRQ_TEMP_ALARM,   PM8008_TEMP_ALARM,BIT(0), IRQ_TYPE_SENSE_MASK),
+	_IRQ(PM8008_IRQ_GPIO1,	      PM8008_GPIO1,	BIT(0), IRQ_TYPE_SENSE_MASK),
+	_IRQ(PM8008_IRQ_GPIO2,	      PM8008_GPIO2,	BIT(0), IRQ_TYPE_SENSE_MASK),
+};
+
+static const unsigned int pm8008_periph_base[] = {
+	PM8008_PERIPH_0_BASE,
+	PM8008_PERIPH_1_BASE,
+	PM8008_PERIPH_2_BASE,
+	PM8008_PERIPH_3_BASE,
+};
+
+static unsigned int pm8008_get_irq_reg(struct regmap_irq_chip_data *data,
+				       unsigned int base, int index)
+{
+	/* Simple linear addressing for the main status register */
+	if (base == I2C_INTR_STATUS_BASE)
+		return base + index;
+
+	return pm8008_periph_base[index] + base;
+}
+
+static int pm8008_set_type_config(unsigned int **buf, unsigned int type,
+				  const struct regmap_irq *irq_data, int idx,
+				  void *irq_drv_data)
+{
+	switch (type) {
+	case IRQ_TYPE_EDGE_FALLING:
+	case IRQ_TYPE_LEVEL_LOW:
+		buf[POLARITY_HI_INDEX][idx] &= ~irq_data->mask;
+		buf[POLARITY_LO_INDEX][idx] |= irq_data->mask;
+		break;
+
+	case IRQ_TYPE_EDGE_RISING:
+	case IRQ_TYPE_LEVEL_HIGH:
+		buf[POLARITY_HI_INDEX][idx] |= irq_data->mask;
+		buf[POLARITY_LO_INDEX][idx] &= ~irq_data->mask;
+		break;
+
+	case IRQ_TYPE_EDGE_BOTH:
+		buf[POLARITY_HI_INDEX][idx] |= irq_data->mask;
+		buf[POLARITY_LO_INDEX][idx] |= irq_data->mask;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	if (type & IRQ_TYPE_EDGE_BOTH)
+		buf[SET_TYPE_INDEX][idx] |= irq_data->mask;
+	else
+		buf[SET_TYPE_INDEX][idx] &= ~irq_data->mask;
+
+	return 0;
+}
+
+static const struct regmap_irq_chip pm8008_irq_chip = {
+	.name			= "pm8008",
+	.main_status		= I2C_INTR_STATUS_BASE,
+	.num_main_regs		= 1,
+	.irqs			= pm8008_irqs,
+	.num_irqs		= ARRAY_SIZE(pm8008_irqs),
+	.num_regs		= PM8008_NUM_PERIPHS,
+	.status_base		= INT_LATCHED_STS_OFFSET,
+	.mask_base		= INT_EN_CLR_OFFSET,
+	.unmask_base		= INT_EN_SET_OFFSET,
+	.mask_unmask_non_inverted = true,
+	.ack_base		= INT_LATCHED_CLR_OFFSET,
+	.config_base		= pm8008_config_regs,
+	.num_config_bases	= ARRAY_SIZE(pm8008_config_regs),
+	.num_config_regs	= PM8008_NUM_PERIPHS,
+	.set_type_config	= pm8008_set_type_config,
+	.get_irq_reg		= pm8008_get_irq_reg,
+};
+
+static const struct regmap_config qcom_mfd_regmap_cfg = {
+	.name		= "primary",
+	.reg_bits	= 16,
+	.val_bits	= 8,
+	.max_register	= 0xffff,
+};
+
+static const struct regmap_config pm8008_regmap_cfg_2 = {
+	.name		= "secondary",
+	.reg_bits	= 16,
+	.val_bits	= 8,
+	.max_register	= 0xffff,
+};
+
+static const struct resource pm8008_temp_res[] = {
+	DEFINE_RES_MEM(PM8008_TEMP_ALARM_ADDR, 0x100),
+	DEFINE_RES_IRQ(PM8008_IRQ_TEMP_ALARM),
+};
+
+static const struct mfd_cell pm8008_cells[] = {
+	MFD_CELL_NAME("pm8008-regulator"),
+	MFD_CELL_RES("qpnp-temp-alarm", pm8008_temp_res),
+	MFD_CELL_NAME("pm8008-gpio"),
+};
+
+static void devm_irq_domain_fwnode_release(void *data)
+{
+	struct fwnode_handle *fwnode = data;
+
+	irq_domain_free_fwnode(fwnode);
+}
+
+static int pm8008_probe(struct i2c_client *client)
+{
+	struct regmap_irq_chip_data *irq_data;
+	struct device *dev = &client->dev;
+	struct regmap *regmap, *regmap2;
+	struct fwnode_handle *fwnode;
+	struct i2c_client *dummy;
+	struct gpio_desc *reset;
+	char *name;
+	int ret;
+
+	dummy = devm_i2c_new_dummy_device(dev, client->adapter, client->addr + 1);
+	if (IS_ERR(dummy)) {
+		ret = PTR_ERR(dummy);
+		dev_err(dev, "failed to claim second address: %d\n", ret);
+		return ret;
+	}
+
+	regmap2 = devm_regmap_init_i2c(dummy, &qcom_mfd_regmap_cfg);
+	if (IS_ERR(regmap2))
+		return PTR_ERR(regmap2);
+
+	ret = regmap_attach_dev(dev, regmap2, &pm8008_regmap_cfg_2);
+	if (ret)
+		return ret;
+
+	/* Default regmap must be attached last. */
+	regmap = devm_regmap_init_i2c(client, &qcom_mfd_regmap_cfg);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(reset))
+		return PTR_ERR(reset);
+
+	/*
+	 * The PMIC does not appear to require a post-reset delay, but wait
+	 * for a millisecond for now anyway.
+	 */
+	usleep_range(1000, 2000);
+
+	name = devm_kasprintf(dev, GFP_KERNEL, "%pOF-internal", dev->of_node);
+	if (!name)
+		return -ENOMEM;
+
+	name = strreplace(name, '/', ':');
+
+	fwnode = irq_domain_alloc_named_fwnode(name);
+	if (!fwnode)
+		return -ENOMEM;
+
+	ret = devm_add_action_or_reset(dev, devm_irq_domain_fwnode_release, fwnode);
+	if (ret)
+		return ret;
+
+	ret = devm_regmap_add_irq_chip_fwnode(dev, fwnode, regmap, client->irq,
+				IRQF_SHARED, 0, &pm8008_irq_chip, &irq_data);
+	if (ret) {
+		dev_err(dev, "failed to add IRQ chip: %d\n", ret);
+		return ret;
+	}
+
+	/* Needed by GPIO driver. */
+	dev_set_drvdata(dev, regmap_irq_get_domain(irq_data));
+
+	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO, pm8008_cells,
+				ARRAY_SIZE(pm8008_cells), NULL, 0,
+				regmap_irq_get_domain(irq_data));
+}
+
+static const struct of_device_id pm8008_match[] = {
+	{ .compatible = "qcom,pm8008", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, pm8008_match);
+
+static struct i2c_driver pm8008_mfd_driver = {
+	.driver = {
+		.name = "pm8008",
+		.of_match_table = pm8008_match,
+	},
+	.probe = pm8008_probe,
+};
+module_i2c_driver(pm8008_mfd_driver);
+
+MODULE_DESCRIPTION("QCOM PM8008 Power Management IC driver");
+MODULE_LICENSE("GPL v2");