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, 325 insertions, 0 deletions

diff --git a/drivers/input/misc/palmas-pwrbutton.c b/drivers/input/misc/palmas-pwrbutton.c
new file mode 100644
index 000000000..f22083f44
--- /dev/null
+++ b/drivers/input/misc/palmas-pwrbutton.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Texas Instruments' Palmas Power Button Input Driver
+ *
+ * Copyright (C) 2012-2014 Texas Instruments Incorporated - http://www.ti.com/
+ *	Girish S Ghongdemath
+ *	Nishanth Menon
+ */
+
+#include <linux/bitfield.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/palmas.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define PALMAS_LPK_TIME_MASK		0x0c
+#define PALMAS_PWRON_DEBOUNCE_MASK	0x03
+#define PALMAS_PWR_KEY_Q_TIME_MS	20
+
+/**
+ * struct palmas_pwron - Palmas power on data
+ * @palmas:		pointer to palmas device
+ * @input_dev:		pointer to input device
+ * @input_work:		work for detecting release of key
+ * @irq:		irq that we are hooked on to
+ */
+struct palmas_pwron {
+	struct palmas *palmas;
+	struct input_dev *input_dev;
+	struct delayed_work input_work;
+	int irq;
+};
+
+/**
+ * struct palmas_pwron_config - configuration of palmas power on
+ * @long_press_time_val:	value for long press h/w shutdown event
+ * @pwron_debounce_val:		value for debounce of power button
+ */
+struct palmas_pwron_config {
+	u8 long_press_time_val;
+	u8 pwron_debounce_val;
+};
+
+/**
+ * palmas_power_button_work() - Detects the button release event
+ * @work:	work item to detect button release
+ */
+static void palmas_power_button_work(struct work_struct *work)
+{
+	struct palmas_pwron *pwron = container_of(work,
+						  struct palmas_pwron,
+						  input_work.work);
+	struct input_dev *input_dev = pwron->input_dev;
+	unsigned int reg;
+	int error;
+
+	error = palmas_read(pwron->palmas, PALMAS_INTERRUPT_BASE,
+			    PALMAS_INT1_LINE_STATE, &reg);
+	if (error) {
+		dev_err(input_dev->dev.parent,
+			"Cannot read palmas PWRON status: %d\n", error);
+	} else if (reg & BIT(1)) {
+		/* The button is released, report event. */
+		input_report_key(input_dev, KEY_POWER, 0);
+		input_sync(input_dev);
+	} else {
+		/* The button is still depressed, keep checking. */
+		schedule_delayed_work(&pwron->input_work,
+				msecs_to_jiffies(PALMAS_PWR_KEY_Q_TIME_MS));
+	}
+}
+
+/**
+ * pwron_irq() - button press isr
+ * @irq:		irq
+ * @palmas_pwron:	pwron struct
+ *
+ * Return: IRQ_HANDLED
+ */
+static irqreturn_t pwron_irq(int irq, void *palmas_pwron)
+{
+	struct palmas_pwron *pwron = palmas_pwron;
+	struct input_dev *input_dev = pwron->input_dev;
+
+	input_report_key(input_dev, KEY_POWER, 1);
+	pm_wakeup_event(input_dev->dev.parent, 0);
+	input_sync(input_dev);
+
+	mod_delayed_work(system_dfl_wq, &pwron->input_work,
+			 msecs_to_jiffies(PALMAS_PWR_KEY_Q_TIME_MS));
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * palmas_pwron_params_ofinit() - device tree parameter parser
+ * @dev:	palmas button device
+ * @config:	configuration params that this fills up
+ */
+static void palmas_pwron_params_ofinit(struct device *dev,
+				       struct palmas_pwron_config *config)
+{
+	struct device_node *np;
+	u32 val;
+	int i, error;
+	static const u8 lpk_times[] = { 6, 8, 10, 12 };
+	static const int pwr_on_deb_ms[] = { 15, 100, 500, 1000 };
+
+	memset(config, 0, sizeof(*config));
+
+	/* Default config parameters */
+	config->long_press_time_val = ARRAY_SIZE(lpk_times) - 1;
+
+	np = dev->of_node;
+	if (!np)
+		return;
+
+	error = of_property_read_u32(np, "ti,palmas-long-press-seconds", &val);
+	if (!error) {
+		for (i = 0; i < ARRAY_SIZE(lpk_times); i++) {
+			if (val <= lpk_times[i]) {
+				config->long_press_time_val = i;
+				break;
+			}
+		}
+	}
+
+	error = of_property_read_u32(np,
+				     "ti,palmas-pwron-debounce-milli-seconds",
+				     &val);
+	if (!error) {
+		for (i = 0; i < ARRAY_SIZE(pwr_on_deb_ms); i++) {
+			if (val <= pwr_on_deb_ms[i]) {
+				config->pwron_debounce_val = i;
+				break;
+			}
+		}
+	}
+
+	dev_info(dev, "h/w controlled shutdown duration=%d seconds\n",
+		 lpk_times[config->long_press_time_val]);
+}
+
+/**
+ * palmas_pwron_probe() - probe
+ * @pdev:	platform device for the button
+ *
+ * Return: 0 for successful probe else appropriate error
+ */
+static int palmas_pwron_probe(struct platform_device *pdev)
+{
+	struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
+	struct device *dev = &pdev->dev;
+	struct input_dev *input_dev;
+	struct palmas_pwron *pwron;
+	struct palmas_pwron_config config;
+	int val;
+	int error;
+
+	palmas_pwron_params_ofinit(dev, &config);
+
+	pwron = kzalloc_obj(*pwron);
+	if (!pwron)
+		return -ENOMEM;
+
+	input_dev = input_allocate_device();
+	if (!input_dev) {
+		dev_err(dev, "Can't allocate power button\n");
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	input_dev->name = "palmas_pwron";
+	input_dev->phys = "palmas_pwron/input0";
+	input_dev->dev.parent = dev;
+
+	input_set_capability(input_dev, EV_KEY, KEY_POWER);
+
+	/*
+	 * Setup default hardware shutdown option (long key press)
+	 * and debounce.
+	 */
+	val = FIELD_PREP(PALMAS_LPK_TIME_MASK, config.long_press_time_val) |
+	      FIELD_PREP(PALMAS_PWRON_DEBOUNCE_MASK, config.pwron_debounce_val);
+	error = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+				   PALMAS_LONG_PRESS_KEY,
+				   PALMAS_LPK_TIME_MASK |
+					PALMAS_PWRON_DEBOUNCE_MASK,
+				   val);
+	if (error) {
+		dev_err(dev, "LONG_PRESS_KEY_UPDATE failed: %d\n", error);
+		goto err_free_input;
+	}
+
+	pwron->palmas = palmas;
+	pwron->input_dev = input_dev;
+
+	INIT_DELAYED_WORK(&pwron->input_work, palmas_power_button_work);
+
+	pwron->irq = platform_get_irq(pdev, 0);
+	if (pwron->irq < 0) {
+		error = pwron->irq;
+		goto err_free_input;
+	}
+
+	error = request_threaded_irq(pwron->irq, NULL, pwron_irq,
+				     IRQF_TRIGGER_HIGH |
+					IRQF_TRIGGER_LOW |
+					IRQF_ONESHOT,
+				     dev_name(dev), pwron);
+	if (error) {
+		dev_err(dev, "Can't get IRQ for pwron: %d\n", error);
+		goto err_free_input;
+	}
+
+	error = input_register_device(input_dev);
+	if (error) {
+		dev_err(dev, "Can't register power button: %d\n", error);
+		goto err_free_irq;
+	}
+
+	platform_set_drvdata(pdev, pwron);
+	device_init_wakeup(dev, true);
+
+	return 0;
+
+err_free_irq:
+	cancel_delayed_work_sync(&pwron->input_work);
+	free_irq(pwron->irq, pwron);
+err_free_input:
+	input_free_device(input_dev);
+err_free_mem:
+	kfree(pwron);
+	return error;
+}
+
+/**
+ * palmas_pwron_remove() - Cleanup on removal
+ * @pdev:	platform device for the button
+ *
+ * Return: 0
+ */
+static void palmas_pwron_remove(struct platform_device *pdev)
+{
+	struct palmas_pwron *pwron = platform_get_drvdata(pdev);
+
+	free_irq(pwron->irq, pwron);
+	cancel_delayed_work_sync(&pwron->input_work);
+
+	input_unregister_device(pwron->input_dev);
+	kfree(pwron);
+}
+
+/**
+ * palmas_pwron_suspend() - suspend handler
+ * @dev:	power button device
+ *
+ * Cancel all pending work items for the power button, setup irq for wakeup
+ *
+ * Return: 0
+ */
+static int palmas_pwron_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct palmas_pwron *pwron = platform_get_drvdata(pdev);
+
+	cancel_delayed_work_sync(&pwron->input_work);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(pwron->irq);
+
+	return 0;
+}
+
+/**
+ * palmas_pwron_resume() - resume handler
+ * @dev:	power button device
+ *
+ * Just disable the wakeup capability of irq here.
+ *
+ * Return: 0
+ */
+static int palmas_pwron_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct palmas_pwron *pwron = platform_get_drvdata(pdev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(pwron->irq);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(palmas_pwron_pm,
+				palmas_pwron_suspend, palmas_pwron_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_palmas_pwr_match[] = {
+	{ .compatible = "ti,palmas-pwrbutton" },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, of_palmas_pwr_match);
+#endif
+
+static struct platform_driver palmas_pwron_driver = {
+	.probe	= palmas_pwron_probe,
+	.remove	= palmas_pwron_remove,
+	.driver	= {
+		.name	= "palmas_pwrbutton",
+		.of_match_table = of_match_ptr(of_palmas_pwr_match),
+		.pm	= pm_sleep_ptr(&palmas_pwron_pm),
+	},
+};
+module_platform_driver(palmas_pwron_driver);
+
+MODULE_ALIAS("platform:palmas-pwrbutton");
+MODULE_DESCRIPTION("Palmas Power Button");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Texas Instruments Inc.");