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, 197 insertions, 0 deletions

diff --git a/drivers/input/misc/pf1550-onkey.c b/drivers/input/misc/pf1550-onkey.c
new file mode 100644
index 000000000..0d1b570bb
--- /dev/null
+++ b/drivers/input/misc/pf1550-onkey.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the PF1550 ONKEY
+ * Copyright (C) 2016 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * Portions Copyright (c) 2025 Savoir-faire Linux Inc.
+ * Samuel Kayode <samuel.kayode@savoirfairelinux.com>
+ */
+
+#include <linux/err.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/pf1550.h>
+#include <linux/platform_device.h>
+
+#define PF1550_ONKEY_IRQ_NR	6
+
+struct onkey_drv_data {
+	struct device *dev;
+	const struct pf1550_ddata *pf1550;
+	bool wakeup;
+	struct input_dev *input;
+};
+
+static irqreturn_t pf1550_onkey_irq_handler(int irq, void *data)
+{
+	struct onkey_drv_data *onkey = data;
+	struct platform_device *pdev = to_platform_device(onkey->dev);
+	int i, state, irq_type = -1;
+
+	for (i = 0; i < PF1550_ONKEY_IRQ_NR; i++)
+		if (irq == platform_get_irq(pdev, i))
+			irq_type = i;
+
+	switch (irq_type) {
+	case PF1550_ONKEY_IRQ_PUSHI:
+		state = 0;
+		break;
+	case PF1550_ONKEY_IRQ_1SI:
+	case PF1550_ONKEY_IRQ_2SI:
+	case PF1550_ONKEY_IRQ_3SI:
+	case PF1550_ONKEY_IRQ_4SI:
+	case PF1550_ONKEY_IRQ_8SI:
+		state = 1;
+		break;
+	default:
+		dev_err(onkey->dev, "onkey interrupt: irq %d occurred\n",
+			irq_type);
+		return IRQ_HANDLED;
+	}
+
+	input_event(onkey->input, EV_KEY, KEY_POWER, state);
+	input_sync(onkey->input);
+
+	return IRQ_HANDLED;
+}
+
+static int pf1550_onkey_probe(struct platform_device *pdev)
+{
+	struct onkey_drv_data *onkey;
+	struct input_dev *input;
+	bool key_power = false;
+	int i, irq, error;
+
+	onkey = devm_kzalloc(&pdev->dev, sizeof(*onkey), GFP_KERNEL);
+	if (!onkey)
+		return -ENOMEM;
+
+	onkey->dev = &pdev->dev;
+
+	onkey->pf1550 = dev_get_drvdata(pdev->dev.parent);
+	if (!onkey->pf1550->regmap)
+		return dev_err_probe(&pdev->dev, -ENODEV,
+				     "failed to get regmap\n");
+
+	onkey->wakeup = device_property_read_bool(pdev->dev.parent,
+						  "wakeup-source");
+
+	if (device_property_read_bool(pdev->dev.parent,
+				      "nxp,disable-key-power")) {
+		error = regmap_clear_bits(onkey->pf1550->regmap,
+					  PF1550_PMIC_REG_PWRCTRL1,
+					  PF1550_ONKEY_RST_EN);
+		if (error)
+			return dev_err_probe(&pdev->dev, error,
+					     "failed: disable turn system off");
+	} else {
+		key_power = true;
+	}
+
+	input = devm_input_allocate_device(&pdev->dev);
+	if (!input)
+		return dev_err_probe(&pdev->dev, -ENOMEM,
+				     "failed to allocate the input device\n");
+
+	input->name = pdev->name;
+	input->phys = "pf1550-onkey/input0";
+	input->id.bustype = BUS_HOST;
+
+	if (key_power)
+		input_set_capability(input, EV_KEY, KEY_POWER);
+
+	onkey->input = input;
+	platform_set_drvdata(pdev, onkey);
+
+	for (i = 0; i < PF1550_ONKEY_IRQ_NR; i++) {
+		irq = platform_get_irq(pdev, i);
+		if (irq < 0)
+			return irq;
+
+		error = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+						  pf1550_onkey_irq_handler,
+						  IRQF_NO_SUSPEND,
+						  "pf1550-onkey", onkey);
+		if (error)
+			return dev_err_probe(&pdev->dev, error,
+					     "failed: irq request (IRQ: %d)\n",
+					     i);
+	}
+
+	error = input_register_device(input);
+	if (error)
+		return dev_err_probe(&pdev->dev, error,
+				     "failed to register input device\n");
+
+	device_init_wakeup(&pdev->dev, onkey->wakeup);
+
+	return 0;
+}
+
+static int pf1550_onkey_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct onkey_drv_data *onkey = platform_get_drvdata(pdev);
+	int i, irq;
+
+	if (!device_may_wakeup(&pdev->dev))
+		regmap_write(onkey->pf1550->regmap,
+			     PF1550_PMIC_REG_ONKEY_INT_MASK0,
+			     ONKEY_IRQ_PUSHI | ONKEY_IRQ_1SI | ONKEY_IRQ_2SI |
+			     ONKEY_IRQ_3SI | ONKEY_IRQ_4SI | ONKEY_IRQ_8SI);
+	else
+		for (i = 0; i < PF1550_ONKEY_IRQ_NR; i++) {
+			irq = platform_get_irq(pdev, i);
+			if (irq > 0)
+				enable_irq_wake(irq);
+		}
+
+	return 0;
+}
+
+static int pf1550_onkey_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct onkey_drv_data *onkey = platform_get_drvdata(pdev);
+	int i, irq;
+
+	if (!device_may_wakeup(&pdev->dev))
+		regmap_write(onkey->pf1550->regmap,
+			     PF1550_PMIC_REG_ONKEY_INT_MASK0,
+			     ~((u8)(ONKEY_IRQ_PUSHI | ONKEY_IRQ_1SI |
+			     ONKEY_IRQ_2SI | ONKEY_IRQ_3SI | ONKEY_IRQ_4SI |
+			     ONKEY_IRQ_8SI)));
+	else
+		for (i = 0; i < PF1550_ONKEY_IRQ_NR; i++) {
+			irq = platform_get_irq(pdev, i);
+			if (irq > 0)
+				disable_irq_wake(irq);
+		}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(pf1550_onkey_pm_ops, pf1550_onkey_suspend,
+			 pf1550_onkey_resume);
+
+static const struct platform_device_id pf1550_onkey_id[] = {
+	{ "pf1550-onkey", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, pf1550_onkey_id);
+
+static struct platform_driver pf1550_onkey_driver = {
+	.driver = {
+		.name = "pf1550-onkey",
+		.pm   = pm_sleep_ptr(&pf1550_onkey_pm_ops),
+	},
+	.probe = pf1550_onkey_probe,
+	.id_table = pf1550_onkey_id,
+};
+module_platform_driver(pf1550_onkey_driver);
+
+MODULE_AUTHOR("Freescale Semiconductor");
+MODULE_DESCRIPTION("PF1550 onkey Driver");
+MODULE_LICENSE("GPL");