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, 212 insertions, 0 deletions

diff --git a/drivers/extcon/extcon-adc-jack.c b/drivers/extcon/extcon-adc-jack.c
new file mode 100644
index 000000000..7e3c9f382
--- /dev/null
+++ b/drivers/extcon/extcon-adc-jack.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/extcon/extcon-adc-jack.c
+ *
+ * Analog Jack extcon driver with ADC-based detection capability.
+ *
+ * Copyright (C) 2016 Samsung Electronics
+ * Chanwoo Choi <cw00.choi@samsung.com>
+ *
+ * Copyright (C) 2012 Samsung Electronics
+ * MyungJoo Ham <myungjoo.ham@samsung.com>
+ *
+ * Modified for calling to IIO to get adc by <anish.singh@samsung.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/workqueue.h>
+#include <linux/iio/consumer.h>
+#include <linux/extcon/extcon-adc-jack.h>
+#include <linux/extcon-provider.h>
+
+/**
+ * struct adc_jack_data - internal data for adc_jack device driver
+ * @dev:		The device structure associated with the adc_jack.
+ * @edev:		extcon device.
+ * @cable_names:	list of supported cables.
+ * @adc_conditions:	list of adc value conditions.
+ * @num_conditions:	size of adc_conditions.
+ * @irq:		irq number of attach/detach event (0 if not exist).
+ * @handling_delay:	interrupt handler will schedule extcon event
+ *			handling at handling_delay jiffies.
+ * @handler:		extcon event handler called by interrupt handler.
+ * @chan:		iio channel being queried.
+ * @wakeup_source:	Indicates if the device can wake up the system.
+ */
+struct adc_jack_data {
+	struct device *dev;
+	struct extcon_dev *edev;
+
+	const unsigned int **cable_names;
+	struct adc_jack_cond *adc_conditions;
+	int num_conditions;
+
+	int irq;
+	unsigned long handling_delay; /* in jiffies */
+	struct delayed_work handler;
+
+	struct iio_channel *chan;
+	bool wakeup_source;
+};
+
+static void adc_jack_handler(struct work_struct *work)
+{
+	struct adc_jack_data *data = container_of(to_delayed_work(work),
+			struct adc_jack_data,
+			handler);
+	struct adc_jack_cond *def;
+	int ret, adc_val;
+	int i;
+
+	ret = iio_read_channel_raw(data->chan, &adc_val);
+	if (ret < 0) {
+		dev_err(data->dev, "read channel() error: %d\n", ret);
+		return;
+	}
+
+	/* Get state from adc value with adc_conditions */
+	for (i = 0; i < data->num_conditions; i++) {
+		def = &data->adc_conditions[i];
+		if (def->min_adc <= adc_val && def->max_adc >= adc_val) {
+			extcon_set_state_sync(data->edev, def->id, true);
+			return;
+		}
+	}
+
+	/* Set the detached state if adc value is not included in the range */
+	for (i = 0; i < data->num_conditions; i++) {
+		def = &data->adc_conditions[i];
+		extcon_set_state_sync(data->edev, def->id, false);
+	}
+}
+
+static irqreturn_t adc_jack_irq_thread(int irq, void *_data)
+{
+	struct adc_jack_data *data = _data;
+
+	queue_delayed_work(system_power_efficient_wq,
+			   &data->handler, data->handling_delay);
+	return IRQ_HANDLED;
+}
+
+static int adc_jack_probe(struct platform_device *pdev)
+{
+	struct adc_jack_data *data;
+	struct adc_jack_pdata *pdata = dev_get_platdata(&pdev->dev);
+	int i, err = 0;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (!pdata->cable_names) {
+		dev_err(&pdev->dev, "error: cable_names not defined.\n");
+		return -EINVAL;
+	}
+
+	data->dev = &pdev->dev;
+	data->edev = devm_extcon_dev_allocate(&pdev->dev, pdata->cable_names);
+	if (IS_ERR(data->edev)) {
+		dev_err(&pdev->dev, "failed to allocate extcon device\n");
+		return -ENOMEM;
+	}
+
+	if (!pdata->adc_conditions) {
+		dev_err(&pdev->dev, "error: adc_conditions not defined.\n");
+		return -EINVAL;
+	}
+	data->adc_conditions = pdata->adc_conditions;
+
+	/* Check the length of array and set num_conditions */
+	for (i = 0; data->adc_conditions[i].id != EXTCON_NONE; i++);
+	data->num_conditions = i;
+
+	data->chan = devm_iio_channel_get(&pdev->dev, pdata->consumer_channel);
+	if (IS_ERR(data->chan))
+		return PTR_ERR(data->chan);
+
+	data->handling_delay = msecs_to_jiffies(pdata->handling_delay_ms);
+	data->wakeup_source = pdata->wakeup_source;
+
+	INIT_DEFERRABLE_WORK(&data->handler, adc_jack_handler);
+
+	platform_set_drvdata(pdev, data);
+
+	err = devm_extcon_dev_register(&pdev->dev, data->edev);
+	if (err)
+		return err;
+
+	data->irq = platform_get_irq(pdev, 0);
+	if (data->irq < 0)
+		return -ENODEV;
+
+	err = request_any_context_irq(data->irq, adc_jack_irq_thread,
+			pdata->irq_flags, pdata->name, data);
+
+	if (err < 0) {
+		dev_err(&pdev->dev, "error: irq %d\n", data->irq);
+		return err;
+	}
+
+	if (data->wakeup_source)
+		device_init_wakeup(&pdev->dev, 1);
+
+	adc_jack_handler(&data->handler.work);
+	return 0;
+}
+
+static void adc_jack_remove(struct platform_device *pdev)
+{
+	struct adc_jack_data *data = platform_get_drvdata(pdev);
+
+	if (data->wakeup_source)
+		device_init_wakeup(&pdev->dev, false);
+	free_irq(data->irq, data);
+	cancel_work_sync(&data->handler.work);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int adc_jack_suspend(struct device *dev)
+{
+	struct adc_jack_data *data = dev_get_drvdata(dev);
+
+	cancel_delayed_work_sync(&data->handler);
+	if (device_may_wakeup(data->dev))
+		enable_irq_wake(data->irq);
+
+	return 0;
+}
+
+static int adc_jack_resume(struct device *dev)
+{
+	struct adc_jack_data *data = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(data->dev))
+		disable_irq_wake(data->irq);
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static SIMPLE_DEV_PM_OPS(adc_jack_pm_ops,
+		adc_jack_suspend, adc_jack_resume);
+
+static struct platform_driver adc_jack_driver = {
+	.probe          = adc_jack_probe,
+	.remove         = adc_jack_remove,
+	.driver         = {
+		.name   = "adc-jack",
+		.pm = &adc_jack_pm_ops,
+	},
+};
+
+module_platform_driver(adc_jack_driver);
+
+MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
+MODULE_DESCRIPTION("ADC Jack extcon driver");
+MODULE_LICENSE("GPL v2");