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, 581 insertions, 0 deletions

diff --git a/drivers/gnss/sirf.c b/drivers/gnss/sirf.c
new file mode 100644
index 000000000..79375d14b
--- /dev/null
+++ b/drivers/gnss/sirf.c
@@ -0,0 +1,581 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SiRFstar GNSS receiver driver
+ *
+ * Copyright (C) 2018 Johan Hovold <johan@kernel.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/gnss.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/pm_runtime.h>
+#include <linux/regulator/consumer.h>
+#include <linux/sched.h>
+#include <linux/serdev.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+
+#define SIRF_BOOT_DELAY			500
+#define SIRF_ON_OFF_PULSE_TIME		100
+#define SIRF_ACTIVATE_TIMEOUT		200
+#define SIRF_HIBERNATE_TIMEOUT		200
+/*
+ * If no data arrives for this time, we assume that the chip is off.
+ * REVISIT: The report cycle is configurable and can be several minutes long,
+ * so this will only work reliably if the report cycle is set to a reasonable
+ * low value. Also power saving settings (like send data only on movement)
+ * might things work even worse.
+ * Workaround might be to parse shutdown or bootup messages.
+ */
+#define SIRF_REPORT_CYCLE	2000
+
+struct sirf_data {
+	struct gnss_device *gdev;
+	struct serdev_device *serdev;
+	speed_t	speed;
+	struct regulator *vcc;
+	struct regulator *lna;
+	struct gpio_desc *on_off;
+	struct gpio_desc *wakeup;
+	int irq;
+	bool active;
+
+	struct mutex gdev_mutex;
+	bool open;
+
+	struct mutex serdev_mutex;
+	int serdev_count;
+
+	wait_queue_head_t power_wait;
+};
+
+static int sirf_serdev_open(struct sirf_data *data)
+{
+	int ret = 0;
+
+	mutex_lock(&data->serdev_mutex);
+	if (++data->serdev_count == 1) {
+		ret = serdev_device_open(data->serdev);
+		if (ret) {
+			data->serdev_count--;
+			goto out_unlock;
+		}
+
+		serdev_device_set_baudrate(data->serdev, data->speed);
+		serdev_device_set_flow_control(data->serdev, false);
+	}
+
+out_unlock:
+	mutex_unlock(&data->serdev_mutex);
+
+	return ret;
+}
+
+static void sirf_serdev_close(struct sirf_data *data)
+{
+	mutex_lock(&data->serdev_mutex);
+	if (--data->serdev_count == 0)
+		serdev_device_close(data->serdev);
+	mutex_unlock(&data->serdev_mutex);
+}
+
+static int sirf_open(struct gnss_device *gdev)
+{
+	struct sirf_data *data = gnss_get_drvdata(gdev);
+	struct serdev_device *serdev = data->serdev;
+	int ret;
+
+	mutex_lock(&data->gdev_mutex);
+	data->open = true;
+	mutex_unlock(&data->gdev_mutex);
+
+	ret = sirf_serdev_open(data);
+	if (ret) {
+		mutex_lock(&data->gdev_mutex);
+		data->open = false;
+		mutex_unlock(&data->gdev_mutex);
+		return ret;
+	}
+
+	ret = pm_runtime_get_sync(&serdev->dev);
+	if (ret < 0) {
+		dev_err(&gdev->dev, "failed to runtime resume: %d\n", ret);
+		pm_runtime_put_noidle(&serdev->dev);
+		goto err_close;
+	}
+
+	return 0;
+
+err_close:
+	sirf_serdev_close(data);
+
+	mutex_lock(&data->gdev_mutex);
+	data->open = false;
+	mutex_unlock(&data->gdev_mutex);
+
+	return ret;
+}
+
+static void sirf_close(struct gnss_device *gdev)
+{
+	struct sirf_data *data = gnss_get_drvdata(gdev);
+	struct serdev_device *serdev = data->serdev;
+
+	sirf_serdev_close(data);
+
+	pm_runtime_put(&serdev->dev);
+
+	mutex_lock(&data->gdev_mutex);
+	data->open = false;
+	mutex_unlock(&data->gdev_mutex);
+}
+
+static int sirf_write_raw(struct gnss_device *gdev, const unsigned char *buf,
+				size_t count)
+{
+	struct sirf_data *data = gnss_get_drvdata(gdev);
+	struct serdev_device *serdev = data->serdev;
+	int ret;
+
+	/* write is only buffered synchronously */
+	ret = serdev_device_write(serdev, buf, count, MAX_SCHEDULE_TIMEOUT);
+	if (ret < 0 || ret < count)
+		return ret;
+
+	/* FIXME: determine if interrupted? */
+	serdev_device_wait_until_sent(serdev, 0);
+
+	return count;
+}
+
+static const struct gnss_operations sirf_gnss_ops = {
+	.open		= sirf_open,
+	.close		= sirf_close,
+	.write_raw	= sirf_write_raw,
+};
+
+static size_t sirf_receive_buf(struct serdev_device *serdev,
+				const u8 *buf, size_t count)
+{
+	struct sirf_data *data = serdev_device_get_drvdata(serdev);
+	struct gnss_device *gdev = data->gdev;
+	int ret = 0;
+
+	if (!data->wakeup && !data->active) {
+		data->active = true;
+		wake_up_interruptible(&data->power_wait);
+	}
+
+	mutex_lock(&data->gdev_mutex);
+	if (data->open)
+		ret = gnss_insert_raw(gdev, buf, count);
+	mutex_unlock(&data->gdev_mutex);
+
+	return ret;
+}
+
+static const struct serdev_device_ops sirf_serdev_ops = {
+	.receive_buf	= sirf_receive_buf,
+	.write_wakeup	= serdev_device_write_wakeup,
+};
+
+static irqreturn_t sirf_wakeup_handler(int irq, void *dev_id)
+{
+	struct sirf_data *data = dev_id;
+	struct device *dev = &data->serdev->dev;
+	int ret;
+
+	ret = gpiod_get_value_cansleep(data->wakeup);
+	dev_dbg(dev, "%s - wakeup = %d\n", __func__, ret);
+	if (ret < 0)
+		goto out;
+
+	data->active = ret;
+	wake_up_interruptible(&data->power_wait);
+out:
+	return IRQ_HANDLED;
+}
+
+static int sirf_wait_for_power_state_nowakeup(struct sirf_data *data,
+						bool active,
+						unsigned long timeout)
+{
+	int ret;
+
+	/* Wait for state change (including any shutdown messages). */
+	msleep(timeout);
+
+	/* Wait for data reception or timeout. */
+	data->active = false;
+	ret = wait_event_interruptible_timeout(data->power_wait,
+			data->active, msecs_to_jiffies(SIRF_REPORT_CYCLE));
+	if (ret < 0)
+		return ret;
+
+	if (ret > 0 && !active)
+		return -ETIMEDOUT;
+
+	if (ret == 0 && active)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static int sirf_wait_for_power_state(struct sirf_data *data, bool active,
+					unsigned long timeout)
+{
+	int ret;
+
+	if (!data->wakeup)
+		return sirf_wait_for_power_state_nowakeup(data, active, timeout);
+
+	ret = wait_event_interruptible_timeout(data->power_wait,
+			data->active == active, msecs_to_jiffies(timeout));
+	if (ret < 0)
+		return ret;
+
+	if (ret == 0) {
+		dev_warn(&data->serdev->dev, "timeout waiting for active state = %d\n",
+				active);
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static void sirf_pulse_on_off(struct sirf_data *data)
+{
+	gpiod_set_value_cansleep(data->on_off, 1);
+	msleep(SIRF_ON_OFF_PULSE_TIME);
+	gpiod_set_value_cansleep(data->on_off, 0);
+}
+
+static int sirf_set_active(struct sirf_data *data, bool active)
+{
+	unsigned long timeout;
+	int retries = 3;
+	int ret;
+
+	if (active)
+		timeout = SIRF_ACTIVATE_TIMEOUT;
+	else
+		timeout = SIRF_HIBERNATE_TIMEOUT;
+
+	if (!data->wakeup) {
+		ret = sirf_serdev_open(data);
+		if (ret)
+			return ret;
+	}
+
+	do {
+		sirf_pulse_on_off(data);
+		ret = sirf_wait_for_power_state(data, active, timeout);
+	} while (ret == -ETIMEDOUT && retries--);
+
+	if (!data->wakeup)
+		sirf_serdev_close(data);
+
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int sirf_runtime_suspend(struct device *dev)
+{
+	struct sirf_data *data = dev_get_drvdata(dev);
+	int ret2;
+	int ret;
+
+	if (data->on_off)
+		ret = sirf_set_active(data, false);
+	else
+		ret = regulator_disable(data->vcc);
+
+	if (ret)
+		return ret;
+
+	ret = regulator_disable(data->lna);
+	if (ret)
+		goto err_reenable;
+
+	return 0;
+
+err_reenable:
+	if (data->on_off)
+		ret2 = sirf_set_active(data, true);
+	else
+		ret2 = regulator_enable(data->vcc);
+
+	if (ret2)
+		dev_err(dev,
+			"failed to reenable power on failed suspend: %d\n",
+			ret2);
+
+	return ret;
+}
+
+static int sirf_runtime_resume(struct device *dev)
+{
+	struct sirf_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = regulator_enable(data->lna);
+	if (ret)
+		return ret;
+
+	if (data->on_off)
+		ret = sirf_set_active(data, true);
+	else
+		ret = regulator_enable(data->vcc);
+
+	if (ret)
+		goto err_disable_lna;
+
+	return 0;
+
+err_disable_lna:
+	regulator_disable(data->lna);
+
+	return ret;
+}
+
+static int __maybe_unused sirf_suspend(struct device *dev)
+{
+	struct sirf_data *data = dev_get_drvdata(dev);
+	int ret = 0;
+
+	if (!pm_runtime_suspended(dev))
+		ret = sirf_runtime_suspend(dev);
+
+	if (data->wakeup)
+		disable_irq(data->irq);
+
+	return ret;
+}
+
+static int __maybe_unused sirf_resume(struct device *dev)
+{
+	struct sirf_data *data = dev_get_drvdata(dev);
+	int ret = 0;
+
+	if (data->wakeup)
+		enable_irq(data->irq);
+
+	if (!pm_runtime_suspended(dev))
+		ret = sirf_runtime_resume(dev);
+
+	return ret;
+}
+
+static const struct dev_pm_ops sirf_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(sirf_suspend, sirf_resume)
+	SET_RUNTIME_PM_OPS(sirf_runtime_suspend, sirf_runtime_resume, NULL)
+};
+
+static int sirf_parse_dt(struct serdev_device *serdev)
+{
+	struct sirf_data *data = serdev_device_get_drvdata(serdev);
+	struct device_node *node = serdev->dev.of_node;
+	u32 speed = 9600;
+
+	of_property_read_u32(node, "current-speed", &speed);
+
+	data->speed = speed;
+
+	return 0;
+}
+
+static int sirf_probe(struct serdev_device *serdev)
+{
+	struct device *dev = &serdev->dev;
+	struct gnss_device *gdev;
+	struct sirf_data *data;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	gdev = gnss_allocate_device(dev);
+	if (!gdev)
+		return -ENOMEM;
+
+	gdev->type = GNSS_TYPE_SIRF;
+	gdev->ops = &sirf_gnss_ops;
+	gnss_set_drvdata(gdev, data);
+
+	data->serdev = serdev;
+	data->gdev = gdev;
+
+	mutex_init(&data->gdev_mutex);
+	mutex_init(&data->serdev_mutex);
+	init_waitqueue_head(&data->power_wait);
+
+	serdev_device_set_drvdata(serdev, data);
+	serdev_device_set_client_ops(serdev, &sirf_serdev_ops);
+
+	ret = sirf_parse_dt(serdev);
+	if (ret)
+		goto err_put_device;
+
+	data->vcc = devm_regulator_get(dev, "vcc");
+	if (IS_ERR(data->vcc)) {
+		ret = PTR_ERR(data->vcc);
+		goto err_put_device;
+	}
+
+	data->lna = devm_regulator_get(dev, "lna");
+	if (IS_ERR(data->lna)) {
+		ret = PTR_ERR(data->lna);
+		goto err_put_device;
+	}
+
+	data->on_off = devm_gpiod_get_optional(dev, "sirf,onoff",
+			GPIOD_OUT_LOW);
+	if (IS_ERR(data->on_off)) {
+		ret = PTR_ERR(data->on_off);
+		goto err_put_device;
+	}
+
+	if (data->on_off) {
+		data->wakeup = devm_gpiod_get_optional(dev, "sirf,wakeup",
+				GPIOD_IN);
+		if (IS_ERR(data->wakeup)) {
+			ret = PTR_ERR(data->wakeup);
+			goto err_put_device;
+		}
+
+		ret = regulator_enable(data->vcc);
+		if (ret)
+			goto err_put_device;
+
+		/* Wait for chip to boot into hibernate mode. */
+		msleep(SIRF_BOOT_DELAY);
+	}
+
+	if (data->wakeup) {
+		ret = gpiod_get_value_cansleep(data->wakeup);
+		if (ret < 0)
+			goto err_disable_vcc;
+		data->active = ret;
+
+		ret = gpiod_to_irq(data->wakeup);
+		if (ret < 0)
+			goto err_disable_vcc;
+		data->irq = ret;
+
+		ret = request_threaded_irq(data->irq, NULL, sirf_wakeup_handler,
+				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+				"wakeup", data);
+		if (ret)
+			goto err_disable_vcc;
+	}
+
+	if (data->on_off) {
+		if (!data->wakeup) {
+			data->active = false;
+
+			ret = sirf_serdev_open(data);
+			if (ret)
+				goto err_disable_vcc;
+
+			msleep(SIRF_REPORT_CYCLE);
+			sirf_serdev_close(data);
+		}
+
+		/* Force hibernate mode if already active. */
+		if (data->active) {
+			ret = sirf_set_active(data, false);
+			if (ret) {
+				dev_err(dev, "failed to set hibernate mode: %d\n",
+						ret);
+				goto err_free_irq;
+			}
+		}
+	}
+
+	if (IS_ENABLED(CONFIG_PM)) {
+		pm_runtime_set_suspended(dev);	/* clear runtime_error flag */
+		pm_runtime_enable(dev);
+	} else {
+		ret = sirf_runtime_resume(dev);
+		if (ret < 0)
+			goto err_free_irq;
+	}
+
+	ret = gnss_register_device(gdev);
+	if (ret)
+		goto err_disable_rpm;
+
+	return 0;
+
+err_disable_rpm:
+	if (IS_ENABLED(CONFIG_PM))
+		pm_runtime_disable(dev);
+	else
+		sirf_runtime_suspend(dev);
+err_free_irq:
+	if (data->wakeup)
+		free_irq(data->irq, data);
+err_disable_vcc:
+	if (data->on_off)
+		regulator_disable(data->vcc);
+err_put_device:
+	gnss_put_device(data->gdev);
+
+	return ret;
+}
+
+static void sirf_remove(struct serdev_device *serdev)
+{
+	struct sirf_data *data = serdev_device_get_drvdata(serdev);
+
+	gnss_deregister_device(data->gdev);
+
+	if (IS_ENABLED(CONFIG_PM))
+		pm_runtime_disable(&serdev->dev);
+	else
+		sirf_runtime_suspend(&serdev->dev);
+
+	if (data->wakeup)
+		free_irq(data->irq, data);
+
+	if (data->on_off)
+		regulator_disable(data->vcc);
+
+	gnss_put_device(data->gdev);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id sirf_of_match[] = {
+	{ .compatible = "fastrax,uc430" },
+	{ .compatible = "linx,r4" },
+	{ .compatible = "wi2wi,w2sg0004" },
+	{ .compatible = "wi2wi,w2sg0008i" },
+	{ .compatible = "wi2wi,w2sg0084i" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sirf_of_match);
+#endif
+
+static struct serdev_device_driver sirf_driver = {
+	.driver	= {
+		.name		= "gnss-sirf",
+		.of_match_table	= of_match_ptr(sirf_of_match),
+		.pm		= &sirf_pm_ops,
+	},
+	.probe	= sirf_probe,
+	.remove	= sirf_remove,
+};
+module_serdev_device_driver(sirf_driver);
+
+MODULE_AUTHOR("Johan Hovold <johan@kernel.org>");
+MODULE_DESCRIPTION("SiRFstar GNSS receiver driver");
+MODULE_LICENSE("GPL v2");