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, 218 insertions, 0 deletions

diff --git a/drivers/extcon/extcon-qcom-spmi-misc.c b/drivers/extcon/extcon-qcom-spmi-misc.c
new file mode 100644
index 000000000..3c522c9c9
--- /dev/null
+++ b/drivers/extcon/extcon-qcom-spmi-misc.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * extcon-qcom-spmi-misc.c - Qualcomm USB extcon driver to support USB ID
+ *			and VBUS detection based on extcon-usb-gpio.c.
+ *
+ * Copyright (C) 2016 Linaro, Ltd.
+ * Stephen Boyd <stephen.boyd@linaro.org>
+ */
+
+#include <linux/devm-helpers.h>
+#include <linux/extcon-provider.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+#define USB_ID_DEBOUNCE_MS	5	/* ms */
+
+struct qcom_usb_extcon_info {
+	struct extcon_dev *edev;
+	int id_irq;
+	int vbus_irq;
+	struct delayed_work wq_detcable;
+	unsigned long debounce_jiffies;
+};
+
+static const unsigned int qcom_usb_extcon_cable[] = {
+	EXTCON_USB,
+	EXTCON_USB_HOST,
+	EXTCON_NONE,
+};
+
+static void qcom_usb_extcon_detect_cable(struct work_struct *work)
+{
+	bool state = false;
+	int ret;
+	union extcon_property_value val;
+	struct qcom_usb_extcon_info *info = container_of(to_delayed_work(work),
+						    struct qcom_usb_extcon_info,
+						    wq_detcable);
+
+	if (info->id_irq > 0) {
+		/* check ID and update cable state */
+		ret = irq_get_irqchip_state(info->id_irq,
+				IRQCHIP_STATE_LINE_LEVEL, &state);
+		if (ret)
+			return;
+
+		if (!state) {
+			val.intval = true;
+			extcon_set_property(info->edev, EXTCON_USB_HOST,
+						EXTCON_PROP_USB_SS, val);
+		}
+		extcon_set_state_sync(info->edev, EXTCON_USB_HOST, !state);
+	}
+
+	if (info->vbus_irq > 0) {
+		/* check VBUS and update cable state */
+		ret = irq_get_irqchip_state(info->vbus_irq,
+				IRQCHIP_STATE_LINE_LEVEL, &state);
+		if (ret)
+			return;
+
+		if (state) {
+			val.intval = true;
+			extcon_set_property(info->edev, EXTCON_USB,
+						EXTCON_PROP_USB_SS, val);
+		}
+		extcon_set_state_sync(info->edev, EXTCON_USB, state);
+	}
+}
+
+static irqreturn_t qcom_usb_irq_handler(int irq, void *dev_id)
+{
+	struct qcom_usb_extcon_info *info = dev_id;
+
+	queue_delayed_work(system_power_efficient_wq, &info->wq_detcable,
+			   info->debounce_jiffies);
+
+	return IRQ_HANDLED;
+}
+
+static int qcom_usb_extcon_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct qcom_usb_extcon_info *info;
+	int ret;
+
+	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	info->edev = devm_extcon_dev_allocate(dev, qcom_usb_extcon_cable);
+	if (IS_ERR(info->edev)) {
+		dev_err(dev, "failed to allocate extcon device\n");
+		return -ENOMEM;
+	}
+
+	ret = devm_extcon_dev_register(dev, info->edev);
+	if (ret < 0) {
+		dev_err(dev, "failed to register extcon device\n");
+		return ret;
+	}
+
+	ret = extcon_set_property_capability(info->edev,
+			EXTCON_USB, EXTCON_PROP_USB_SS);
+	ret |= extcon_set_property_capability(info->edev,
+			EXTCON_USB_HOST, EXTCON_PROP_USB_SS);
+	if (ret) {
+		dev_err(dev, "failed to register extcon props rc=%d\n",
+						ret);
+		return ret;
+	}
+
+	info->debounce_jiffies = msecs_to_jiffies(USB_ID_DEBOUNCE_MS);
+
+	ret = devm_delayed_work_autocancel(dev, &info->wq_detcable,
+					   qcom_usb_extcon_detect_cable);
+	if (ret)
+		return ret;
+
+	info->id_irq = platform_get_irq_byname_optional(pdev, "usb_id");
+	if (info->id_irq > 0) {
+		ret = devm_request_threaded_irq(dev, info->id_irq, NULL,
+					qcom_usb_irq_handler,
+					IRQF_TRIGGER_RISING |
+					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+					pdev->name, info);
+		if (ret < 0) {
+			dev_err(dev, "failed to request handler for ID IRQ\n");
+			return ret;
+		}
+	}
+
+	info->vbus_irq = platform_get_irq_byname_optional(pdev, "usb_vbus");
+	if (info->vbus_irq > 0) {
+		ret = devm_request_threaded_irq(dev, info->vbus_irq, NULL,
+					qcom_usb_irq_handler,
+					IRQF_TRIGGER_RISING |
+					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+					pdev->name, info);
+		if (ret < 0) {
+			dev_err(dev, "failed to request handler for VBUS IRQ\n");
+			return ret;
+		}
+	}
+
+	if (info->id_irq < 0 && info->vbus_irq < 0) {
+		dev_err(dev, "ID and VBUS IRQ not found\n");
+		return -EINVAL;
+	}
+
+	platform_set_drvdata(pdev, info);
+	devm_device_init_wakeup(dev);
+
+	/* Perform initial detection */
+	qcom_usb_extcon_detect_cable(&info->wq_detcable.work);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int qcom_usb_extcon_suspend(struct device *dev)
+{
+	struct qcom_usb_extcon_info *info = dev_get_drvdata(dev);
+	int ret = 0;
+
+	if (device_may_wakeup(dev)) {
+		if (info->id_irq > 0)
+			ret = enable_irq_wake(info->id_irq);
+		if (info->vbus_irq > 0)
+			ret = enable_irq_wake(info->vbus_irq);
+	}
+
+	return ret;
+}
+
+static int qcom_usb_extcon_resume(struct device *dev)
+{
+	struct qcom_usb_extcon_info *info = dev_get_drvdata(dev);
+	int ret = 0;
+
+	if (device_may_wakeup(dev)) {
+		if (info->id_irq > 0)
+			ret = disable_irq_wake(info->id_irq);
+		if (info->vbus_irq > 0)
+			ret = disable_irq_wake(info->vbus_irq);
+	}
+
+	return ret;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(qcom_usb_extcon_pm_ops,
+			 qcom_usb_extcon_suspend, qcom_usb_extcon_resume);
+
+static const struct of_device_id qcom_usb_extcon_dt_match[] = {
+	{ .compatible = "qcom,pm8941-misc", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, qcom_usb_extcon_dt_match);
+
+static struct platform_driver qcom_usb_extcon_driver = {
+	.probe		= qcom_usb_extcon_probe,
+	.driver		= {
+		.name	= "extcon-pm8941-misc",
+		.pm	= &qcom_usb_extcon_pm_ops,
+		.of_match_table = qcom_usb_extcon_dt_match,
+	},
+};
+module_platform_driver(qcom_usb_extcon_driver);
+
+MODULE_DESCRIPTION("QCOM USB ID extcon driver");
+MODULE_AUTHOR("Stephen Boyd <stephen.boyd@linaro.org>");
+MODULE_LICENSE("GPL v2");