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, 220 insertions, 0 deletions

diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c
new file mode 100644
index 000000000..9c5b695db
--- /dev/null
+++ b/net/rfkill/rfkill-gpio.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2011, NVIDIA Corporation.
+ */
+
+#include <linux/dmi.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rfkill.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/slab.h>
+#include <linux/acpi.h>
+#include <linux/gpio/consumer.h>
+
+struct rfkill_gpio_data {
+	const char		*name;
+	enum rfkill_type	type;
+	struct gpio_desc	*reset_gpio;
+	struct gpio_desc	*shutdown_gpio;
+
+	struct rfkill		*rfkill_dev;
+	struct clk		*clk;
+
+	bool			clk_enabled;
+};
+
+static int rfkill_gpio_set_power(void *data, bool blocked)
+{
+	struct rfkill_gpio_data *rfkill = data;
+
+	if (!blocked && !IS_ERR(rfkill->clk) && !rfkill->clk_enabled) {
+		int ret = clk_enable(rfkill->clk);
+
+		if (ret)
+			return ret;
+	}
+
+	gpiod_set_value_cansleep(rfkill->shutdown_gpio, !blocked);
+	gpiod_set_value_cansleep(rfkill->reset_gpio, !blocked);
+
+	if (blocked && !IS_ERR(rfkill->clk) && rfkill->clk_enabled)
+		clk_disable(rfkill->clk);
+
+	rfkill->clk_enabled = !blocked;
+
+	return 0;
+}
+
+static const struct rfkill_ops rfkill_gpio_ops = {
+	.set_block = rfkill_gpio_set_power,
+};
+
+static const struct acpi_gpio_params reset_gpios = { 0, 0, false };
+static const struct acpi_gpio_params shutdown_gpios = { 1, 0, false };
+
+static const struct acpi_gpio_mapping acpi_rfkill_default_gpios[] = {
+	{ "reset-gpios", &reset_gpios, 1 },
+	{ "shutdown-gpios", &shutdown_gpios, 1 },
+	{ },
+};
+
+static int rfkill_gpio_acpi_probe(struct device *dev,
+				  struct rfkill_gpio_data *rfkill)
+{
+	const struct acpi_device_id *id;
+
+	id = acpi_match_device(dev->driver->acpi_match_table, dev);
+	if (!id)
+		return -ENODEV;
+
+	rfkill->type = (unsigned)id->driver_data;
+
+	return devm_acpi_dev_add_driver_gpios(dev, acpi_rfkill_default_gpios);
+}
+
+/* List of DMI matches for devices on which rfkill-gpio should not load,
+ * to avoid firmware bugs.
+ */
+static const struct dmi_system_id rfkill_gpio_deny_table[] = {
+	{
+		/* Lenovo Yoga Tab 3 Pro YT3-X90, bogus "BCM4752" device in DSDT */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Intel Corporation"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "Blade3-10A-001"),
+		},
+	},
+	{ }
+};
+
+static int rfkill_gpio_probe(struct platform_device *pdev)
+{
+	struct rfkill_gpio_data *rfkill;
+	const char *type_name = NULL;
+	const char *name_property;
+	const char *type_property;
+	struct gpio_desc *gpio;
+	int ret;
+
+	if (dmi_check_system(rfkill_gpio_deny_table))
+		return -ENODEV;
+
+	rfkill = devm_kzalloc(&pdev->dev, sizeof(*rfkill), GFP_KERNEL);
+	if (!rfkill)
+		return -ENOMEM;
+
+	if (dev_of_node(&pdev->dev)) {
+		name_property = "label";
+		type_property = "radio-type";
+	} else {
+		name_property = "name";
+		type_property = "type";
+	}
+	device_property_read_string(&pdev->dev, name_property, &rfkill->name);
+	device_property_read_string(&pdev->dev, type_property, &type_name);
+
+	if (!rfkill->name)
+		rfkill->name = dev_name(&pdev->dev);
+
+	rfkill->type = rfkill_find_type(type_name);
+
+	if (ACPI_HANDLE(&pdev->dev)) {
+		ret = rfkill_gpio_acpi_probe(&pdev->dev, rfkill);
+		if (ret)
+			return ret;
+	}
+
+	rfkill->clk = devm_clk_get(&pdev->dev, NULL);
+
+	gpio = devm_gpiod_get_optional(&pdev->dev, "reset", GPIOD_ASIS);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+
+	rfkill->reset_gpio = gpio;
+
+	gpio = devm_gpiod_get_optional(&pdev->dev, "shutdown", GPIOD_ASIS);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+
+	rfkill->shutdown_gpio = gpio;
+
+	/* Make sure at-least one GPIO is defined for this instance */
+	if (!rfkill->reset_gpio && !rfkill->shutdown_gpio) {
+		dev_err(&pdev->dev, "invalid platform data\n");
+		return -EINVAL;
+	}
+
+	ret = gpiod_direction_output(rfkill->reset_gpio, true);
+	if (ret)
+		return ret;
+
+	ret = gpiod_direction_output(rfkill->shutdown_gpio, true);
+	if (ret)
+		return ret;
+
+	rfkill->rfkill_dev = rfkill_alloc(rfkill->name, &pdev->dev,
+					  rfkill->type, &rfkill_gpio_ops,
+					  rfkill);
+	if (!rfkill->rfkill_dev)
+		return -ENOMEM;
+
+	if (device_property_present(&pdev->dev, "default-blocked"))
+		rfkill_init_sw_state(rfkill->rfkill_dev, true);
+
+	ret = rfkill_register(rfkill->rfkill_dev);
+	if (ret < 0)
+		goto err_destroy;
+
+	platform_set_drvdata(pdev, rfkill);
+
+	dev_info(&pdev->dev, "%s device registered.\n", rfkill->name);
+
+	return 0;
+
+err_destroy:
+	rfkill_destroy(rfkill->rfkill_dev);
+
+	return ret;
+}
+
+static void rfkill_gpio_remove(struct platform_device *pdev)
+{
+	struct rfkill_gpio_data *rfkill = platform_get_drvdata(pdev);
+
+	rfkill_unregister(rfkill->rfkill_dev);
+	rfkill_destroy(rfkill->rfkill_dev);
+}
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id rfkill_acpi_match[] = {
+	{ "BCM4752", RFKILL_TYPE_GPS },
+	{ "LNV4752", RFKILL_TYPE_GPS },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, rfkill_acpi_match);
+#endif
+
+static const struct of_device_id rfkill_of_match[] __maybe_unused = {
+	{ .compatible = "rfkill-gpio", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, rfkill_of_match);
+
+static struct platform_driver rfkill_gpio_driver = {
+	.probe = rfkill_gpio_probe,
+	.remove = rfkill_gpio_remove,
+	.driver = {
+		.name = "rfkill_gpio",
+		.acpi_match_table = ACPI_PTR(rfkill_acpi_match),
+		.of_match_table = of_match_ptr(rfkill_of_match),
+	},
+};
+
+module_platform_driver(rfkill_gpio_driver);
+
+MODULE_DESCRIPTION("gpio rfkill");
+MODULE_AUTHOR("NVIDIA");
+MODULE_LICENSE("GPL");