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, 459 insertions, 0 deletions

diff --git a/drivers/mfd/as3722.c b/drivers/mfd/as3722.c
new file mode 100644
index 000000000..7ab6fcc9c
--- /dev/null
+++ b/drivers/mfd/as3722.c
@@ -0,0 +1,459 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Core driver for ams AS3722 PMICs
+ *
+ * Copyright (C) 2013 AMS AG
+ * Copyright (c) 2013, NVIDIA Corporation. All rights reserved.
+ *
+ * Author: Florian Lobmaier <florian.lobmaier@ams.com>
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/as3722.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define AS3722_DEVICE_ID	0x0C
+
+static const struct resource as3722_rtc_resource[] = {
+	DEFINE_RES_IRQ_NAMED(AS3722_IRQ_RTC_ALARM, "as3722-rtc-alarm"),
+};
+
+static const struct resource as3722_adc_resource[] = {
+	DEFINE_RES_IRQ_NAMED(AS3722_IRQ_ADC, "as3722-adc"),
+};
+
+static const struct mfd_cell as3722_devs[] = {
+	{
+		.name = "as3722-pinctrl",
+	},
+	{
+		.name = "as3722-regulator",
+	},
+	{
+		.name = "as3722-rtc",
+		.num_resources = ARRAY_SIZE(as3722_rtc_resource),
+		.resources = as3722_rtc_resource,
+	},
+	{
+		.name = "as3722-adc",
+		.num_resources = ARRAY_SIZE(as3722_adc_resource),
+		.resources = as3722_adc_resource,
+	},
+	{
+		.name = "as3722-power-off",
+	},
+	{
+		.name = "as3722-wdt",
+	},
+};
+
+static const struct regmap_irq as3722_irqs[] = {
+	/* INT1 IRQs */
+	[AS3722_IRQ_LID] = {
+		.mask = AS3722_INTERRUPT_MASK1_LID,
+	},
+	[AS3722_IRQ_ACOK] = {
+		.mask = AS3722_INTERRUPT_MASK1_ACOK,
+	},
+	[AS3722_IRQ_ENABLE1] = {
+		.mask = AS3722_INTERRUPT_MASK1_ENABLE1,
+	},
+	[AS3722_IRQ_OCCUR_ALARM_SD0] = {
+		.mask = AS3722_INTERRUPT_MASK1_OCURR_ALARM_SD0,
+	},
+	[AS3722_IRQ_ONKEY_LONG_PRESS] = {
+		.mask = AS3722_INTERRUPT_MASK1_ONKEY_LONG,
+	},
+	[AS3722_IRQ_ONKEY] = {
+		.mask = AS3722_INTERRUPT_MASK1_ONKEY,
+	},
+	[AS3722_IRQ_OVTMP] = {
+		.mask = AS3722_INTERRUPT_MASK1_OVTMP,
+	},
+	[AS3722_IRQ_LOWBAT] = {
+		.mask = AS3722_INTERRUPT_MASK1_LOWBAT,
+	},
+
+	/* INT2 IRQs */
+	[AS3722_IRQ_SD0_LV] = {
+		.mask = AS3722_INTERRUPT_MASK2_SD0_LV,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_SD1_LV] = {
+		.mask = AS3722_INTERRUPT_MASK2_SD1_LV,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_SD2_LV] = {
+		.mask = AS3722_INTERRUPT_MASK2_SD2345_LV,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_PWM1_OV_PROT] = {
+		.mask = AS3722_INTERRUPT_MASK2_PWM1_OV_PROT,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_PWM2_OV_PROT] = {
+		.mask = AS3722_INTERRUPT_MASK2_PWM2_OV_PROT,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_ENABLE2] = {
+		.mask = AS3722_INTERRUPT_MASK2_ENABLE2,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_SD6_LV] = {
+		.mask = AS3722_INTERRUPT_MASK2_SD6_LV,
+		.reg_offset = 1,
+	},
+	[AS3722_IRQ_RTC_REP] = {
+		.mask = AS3722_INTERRUPT_MASK2_RTC_REP,
+		.reg_offset = 1,
+	},
+
+	/* INT3 IRQs */
+	[AS3722_IRQ_RTC_ALARM] = {
+		.mask = AS3722_INTERRUPT_MASK3_RTC_ALARM,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_GPIO1] = {
+		.mask = AS3722_INTERRUPT_MASK3_GPIO1,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_GPIO2] = {
+		.mask = AS3722_INTERRUPT_MASK3_GPIO2,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_GPIO3] = {
+		.mask = AS3722_INTERRUPT_MASK3_GPIO3,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_GPIO4] = {
+		.mask = AS3722_INTERRUPT_MASK3_GPIO4,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_GPIO5] = {
+		.mask = AS3722_INTERRUPT_MASK3_GPIO5,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_WATCHDOG] = {
+		.mask = AS3722_INTERRUPT_MASK3_WATCHDOG,
+		.reg_offset = 2,
+	},
+	[AS3722_IRQ_ENABLE3] = {
+		.mask = AS3722_INTERRUPT_MASK3_ENABLE3,
+		.reg_offset = 2,
+	},
+
+	/* INT4 IRQs */
+	[AS3722_IRQ_TEMP_SD0_SHUTDOWN] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD0_SHUTDOWN,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_TEMP_SD1_SHUTDOWN] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD1_SHUTDOWN,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_TEMP_SD2_SHUTDOWN] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD6_SHUTDOWN,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_TEMP_SD0_ALARM] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD0_ALARM,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_TEMP_SD1_ALARM] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD1_ALARM,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_TEMP_SD6_ALARM] = {
+		.mask = AS3722_INTERRUPT_MASK4_TEMP_SD6_ALARM,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_OCCUR_ALARM_SD6] = {
+		.mask = AS3722_INTERRUPT_MASK4_OCCUR_ALARM_SD6,
+		.reg_offset = 3,
+	},
+	[AS3722_IRQ_ADC] = {
+		.mask = AS3722_INTERRUPT_MASK4_ADC,
+		.reg_offset = 3,
+	},
+};
+
+static const struct regmap_irq_chip as3722_irq_chip = {
+	.name = "as3722",
+	.irqs = as3722_irqs,
+	.num_irqs = ARRAY_SIZE(as3722_irqs),
+	.num_regs = 4,
+	.status_base = AS3722_INTERRUPT_STATUS1_REG,
+	.mask_base = AS3722_INTERRUPT_MASK1_REG,
+};
+
+static int as3722_check_device_id(struct as3722 *as3722)
+{
+	u32 val;
+	int ret;
+
+	/* Check that this is actually a AS3722 */
+	ret = as3722_read(as3722, AS3722_ASIC_ID1_REG, &val);
+	if (ret < 0) {
+		dev_err(as3722->dev, "ASIC_ID1 read failed: %d\n", ret);
+		return ret;
+	}
+
+	if (val != AS3722_DEVICE_ID) {
+		dev_err(as3722->dev, "Device is not AS3722, ID is 0x%x\n", val);
+		return -ENODEV;
+	}
+
+	ret = as3722_read(as3722, AS3722_ASIC_ID2_REG, &val);
+	if (ret < 0) {
+		dev_err(as3722->dev, "ASIC_ID2 read failed: %d\n", ret);
+		return ret;
+	}
+
+	dev_info(as3722->dev, "AS3722 with revision 0x%x found\n", val);
+	return 0;
+}
+
+static int as3722_configure_pullups(struct as3722 *as3722)
+{
+	int ret;
+	u32 val = 0;
+
+	if (as3722->en_intern_int_pullup)
+		val |= AS3722_INT_PULL_UP;
+	if (as3722->en_intern_i2c_pullup)
+		val |= AS3722_I2C_PULL_UP;
+
+	ret = as3722_update_bits(as3722, AS3722_IOVOLTAGE_REG,
+			AS3722_INT_PULL_UP | AS3722_I2C_PULL_UP, val);
+	if (ret < 0)
+		dev_err(as3722->dev, "IOVOLTAGE_REG update failed: %d\n", ret);
+	return ret;
+}
+
+static const struct regmap_range as3722_readable_ranges[] = {
+	regmap_reg_range(AS3722_SD0_VOLTAGE_REG, AS3722_SD6_VOLTAGE_REG),
+	regmap_reg_range(AS3722_GPIO0_CONTROL_REG, AS3722_LDO7_VOLTAGE_REG),
+	regmap_reg_range(AS3722_LDO9_VOLTAGE_REG, AS3722_REG_SEQU_MOD3_REG),
+	regmap_reg_range(AS3722_SD_PHSW_CTRL_REG, AS3722_PWM_CONTROL_H_REG),
+	regmap_reg_range(AS3722_WATCHDOG_TIMER_REG, AS3722_WATCHDOG_TIMER_REG),
+	regmap_reg_range(AS3722_WATCHDOG_SOFTWARE_SIGNAL_REG,
+					AS3722_BATTERY_VOLTAGE_MONITOR2_REG),
+	regmap_reg_range(AS3722_SD_CONTROL_REG, AS3722_PWM_VCONTROL4_REG),
+	regmap_reg_range(AS3722_BB_CHARGER_REG, AS3722_SRAM_REG),
+	regmap_reg_range(AS3722_RTC_ACCESS_REG, AS3722_RTC_ACCESS_REG),
+	regmap_reg_range(AS3722_RTC_STATUS_REG, AS3722_TEMP_STATUS_REG),
+	regmap_reg_range(AS3722_ADC0_CONTROL_REG, AS3722_ADC_CONFIGURATION_REG),
+	regmap_reg_range(AS3722_ASIC_ID1_REG, AS3722_ASIC_ID2_REG),
+	regmap_reg_range(AS3722_LOCK_REG, AS3722_LOCK_REG),
+	regmap_reg_range(AS3722_FUSE7_REG, AS3722_FUSE7_REG),
+};
+
+static const struct regmap_access_table as3722_readable_table = {
+	.yes_ranges = as3722_readable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(as3722_readable_ranges),
+};
+
+static const struct regmap_range as3722_writable_ranges[] = {
+	regmap_reg_range(AS3722_SD0_VOLTAGE_REG, AS3722_SD6_VOLTAGE_REG),
+	regmap_reg_range(AS3722_GPIO0_CONTROL_REG, AS3722_LDO7_VOLTAGE_REG),
+	regmap_reg_range(AS3722_LDO9_VOLTAGE_REG, AS3722_GPIO_SIGNAL_OUT_REG),
+	regmap_reg_range(AS3722_REG_SEQU_MOD1_REG, AS3722_REG_SEQU_MOD3_REG),
+	regmap_reg_range(AS3722_SD_PHSW_CTRL_REG, AS3722_PWM_CONTROL_H_REG),
+	regmap_reg_range(AS3722_WATCHDOG_TIMER_REG, AS3722_WATCHDOG_TIMER_REG),
+	regmap_reg_range(AS3722_WATCHDOG_SOFTWARE_SIGNAL_REG,
+					AS3722_BATTERY_VOLTAGE_MONITOR2_REG),
+	regmap_reg_range(AS3722_SD_CONTROL_REG, AS3722_PWM_VCONTROL4_REG),
+	regmap_reg_range(AS3722_BB_CHARGER_REG, AS3722_SRAM_REG),
+	regmap_reg_range(AS3722_INTERRUPT_MASK1_REG, AS3722_TEMP_STATUS_REG),
+	regmap_reg_range(AS3722_ADC0_CONTROL_REG, AS3722_ADC1_CONTROL_REG),
+	regmap_reg_range(AS3722_ADC1_THRESHOLD_HI_MSB_REG,
+					AS3722_ADC_CONFIGURATION_REG),
+	regmap_reg_range(AS3722_LOCK_REG, AS3722_LOCK_REG),
+};
+
+static const struct regmap_access_table as3722_writable_table = {
+	.yes_ranges = as3722_writable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(as3722_writable_ranges),
+};
+
+static const struct regmap_range as3722_cacheable_ranges[] = {
+	regmap_reg_range(AS3722_SD0_VOLTAGE_REG, AS3722_LDO11_VOLTAGE_REG),
+	regmap_reg_range(AS3722_SD_CONTROL_REG, AS3722_LDOCONTROL1_REG),
+};
+
+static const struct regmap_access_table as3722_volatile_table = {
+	.no_ranges = as3722_cacheable_ranges,
+	.n_no_ranges = ARRAY_SIZE(as3722_cacheable_ranges),
+};
+
+static const struct regmap_config as3722_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = AS3722_MAX_REGISTER,
+	.cache_type = REGCACHE_MAPLE,
+	.rd_table = &as3722_readable_table,
+	.wr_table = &as3722_writable_table,
+	.volatile_table = &as3722_volatile_table,
+};
+
+static int as3722_i2c_of_probe(struct i2c_client *i2c,
+			struct as3722 *as3722)
+{
+	struct device_node *np = i2c->dev.of_node;
+	struct irq_data *irq_data;
+
+	if (!np) {
+		dev_err(&i2c->dev, "Device Tree not found\n");
+		return -EINVAL;
+	}
+
+	irq_data = irq_get_irq_data(i2c->irq);
+	if (!irq_data) {
+		dev_err(&i2c->dev, "Invalid IRQ: %d\n", i2c->irq);
+		return -EINVAL;
+	}
+
+	as3722->en_intern_int_pullup = of_property_read_bool(np,
+					"ams,enable-internal-int-pullup");
+	as3722->en_intern_i2c_pullup = of_property_read_bool(np,
+					"ams,enable-internal-i2c-pullup");
+	as3722->en_ac_ok_pwr_on = of_property_read_bool(np,
+					"ams,enable-ac-ok-power-on");
+	as3722->irq_flags = irqd_get_trigger_type(irq_data);
+	dev_dbg(&i2c->dev, "IRQ flags are 0x%08lx\n", as3722->irq_flags);
+	return 0;
+}
+
+static int as3722_i2c_probe(struct i2c_client *i2c)
+{
+	struct as3722 *as3722;
+	unsigned long irq_flags;
+	int ret;
+	u8 val = 0;
+
+	as3722 = devm_kzalloc(&i2c->dev, sizeof(struct as3722), GFP_KERNEL);
+	if (!as3722)
+		return -ENOMEM;
+
+	as3722->dev = &i2c->dev;
+	as3722->chip_irq = i2c->irq;
+	i2c_set_clientdata(i2c, as3722);
+
+	ret = as3722_i2c_of_probe(i2c, as3722);
+	if (ret < 0)
+		return ret;
+
+	as3722->regmap = devm_regmap_init_i2c(i2c, &as3722_regmap_config);
+	if (IS_ERR(as3722->regmap)) {
+		ret = PTR_ERR(as3722->regmap);
+		dev_err(&i2c->dev, "regmap init failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = as3722_check_device_id(as3722);
+	if (ret < 0)
+		return ret;
+
+	irq_flags = as3722->irq_flags | IRQF_ONESHOT;
+	ret = devm_regmap_add_irq_chip(as3722->dev, as3722->regmap,
+				       as3722->chip_irq,
+				       irq_flags, -1, &as3722_irq_chip,
+				       &as3722->irq_data);
+	if (ret < 0) {
+		dev_err(as3722->dev, "Failed to add regmap irq: %d\n", ret);
+		return ret;
+	}
+
+	ret = as3722_configure_pullups(as3722);
+	if (ret < 0)
+		return ret;
+
+	if (as3722->en_ac_ok_pwr_on)
+		val = AS3722_CTRL_SEQU1_AC_OK_PWR_ON;
+	ret = as3722_update_bits(as3722, AS3722_CTRL_SEQU1_REG,
+			AS3722_CTRL_SEQU1_AC_OK_PWR_ON, val);
+	if (ret < 0) {
+		dev_err(as3722->dev, "CTRLsequ1 update failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_mfd_add_devices(&i2c->dev, -1, as3722_devs,
+				   ARRAY_SIZE(as3722_devs), NULL, 0,
+				   regmap_irq_get_domain(as3722->irq_data));
+	if (ret) {
+		dev_err(as3722->dev, "Failed to add MFD devices: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_device_init_wakeup(as3722->dev);
+	if (ret)
+		return dev_err_probe(as3722->dev, ret, "Failed to init wakeup\n");
+
+	dev_dbg(as3722->dev, "AS3722 core driver initialized successfully\n");
+	return 0;
+}
+
+static int __maybe_unused as3722_i2c_suspend(struct device *dev)
+{
+	struct as3722 *as3722 = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(as3722->chip_irq);
+	disable_irq(as3722->chip_irq);
+
+	return 0;
+}
+
+static int __maybe_unused as3722_i2c_resume(struct device *dev)
+{
+	struct as3722 *as3722 = dev_get_drvdata(dev);
+
+	enable_irq(as3722->chip_irq);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(as3722->chip_irq);
+
+	return 0;
+}
+
+static const struct of_device_id as3722_of_match[] = {
+	{ .compatible = "ams,as3722", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, as3722_of_match);
+
+static const struct i2c_device_id as3722_i2c_id[] = {
+	{ "as3722" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, as3722_i2c_id);
+
+static const struct dev_pm_ops as3722_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(as3722_i2c_suspend, as3722_i2c_resume)
+};
+
+static struct i2c_driver as3722_i2c_driver = {
+	.driver = {
+		.name = "as3722",
+		.of_match_table = as3722_of_match,
+		.pm = &as3722_pm_ops,
+	},
+	.probe = as3722_i2c_probe,
+	.id_table = as3722_i2c_id,
+};
+
+module_i2c_driver(as3722_i2c_driver);
+
+MODULE_DESCRIPTION("I2C support for AS3722 PMICs");
+MODULE_AUTHOR("Florian Lobmaier <florian.lobmaier@ams.com>");
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_LICENSE("GPL");