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, 266 insertions, 0 deletions

diff --git a/drivers/input/misc/mc13783-pwrbutton.c b/drivers/input/misc/mc13783-pwrbutton.c
new file mode 100644
index 000000000..cb781ce96
--- /dev/null
+++ b/drivers/input/misc/mc13783-pwrbutton.c
@@ -0,0 +1,266 @@
+/*
+ * Copyright (C) 2011 Philippe Rétornaz
+ *
+ * Based on twl4030-pwrbutton driver by:
+ *     Peter De Schrijver <peter.de-schrijver@nokia.com>
+ *     Felipe Balbi <felipe.balbi@nokia.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General
+ * Public License. See the file "COPYING" in the main directory of this
+ * archive for more details.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335  USA
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/mc13783.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+struct mc13783_pwrb {
+	struct input_dev *pwr;
+	struct mc13xxx *mc13783;
+#define MC13783_PWRB_B1_POL_INVERT	(1 << 0)
+#define MC13783_PWRB_B2_POL_INVERT	(1 << 1)
+#define MC13783_PWRB_B3_POL_INVERT	(1 << 2)
+	int flags;
+	unsigned short keymap[3];
+};
+
+#define MC13783_REG_INTERRUPT_SENSE_1		5
+#define MC13783_IRQSENSE1_ONOFD1S		(1 << 3)
+#define MC13783_IRQSENSE1_ONOFD2S		(1 << 4)
+#define MC13783_IRQSENSE1_ONOFD3S		(1 << 5)
+
+#define MC13783_REG_POWER_CONTROL_2		15
+#define MC13783_POWER_CONTROL_2_ON1BDBNC	4
+#define MC13783_POWER_CONTROL_2_ON2BDBNC	6
+#define MC13783_POWER_CONTROL_2_ON3BDBNC	8
+#define MC13783_POWER_CONTROL_2_ON1BRSTEN	(1 << 1)
+#define MC13783_POWER_CONTROL_2_ON2BRSTEN	(1 << 2)
+#define MC13783_POWER_CONTROL_2_ON3BRSTEN	(1 << 3)
+
+static irqreturn_t button_irq(int irq, void *_priv)
+{
+	struct mc13783_pwrb *priv = _priv;
+	int val;
+
+	mc13xxx_reg_read(priv->mc13783, MC13783_REG_INTERRUPT_SENSE_1, &val);
+
+	switch (irq) {
+	case MC13783_IRQ_ONOFD1:
+		val = val & MC13783_IRQSENSE1_ONOFD1S ? 1 : 0;
+		if (priv->flags & MC13783_PWRB_B1_POL_INVERT)
+			val ^= 1;
+		input_report_key(priv->pwr, priv->keymap[0], val);
+		break;
+
+	case MC13783_IRQ_ONOFD2:
+		val = val & MC13783_IRQSENSE1_ONOFD2S ? 1 : 0;
+		if (priv->flags & MC13783_PWRB_B2_POL_INVERT)
+			val ^= 1;
+		input_report_key(priv->pwr, priv->keymap[1], val);
+		break;
+
+	case MC13783_IRQ_ONOFD3:
+		val = val & MC13783_IRQSENSE1_ONOFD3S ? 1 : 0;
+		if (priv->flags & MC13783_PWRB_B3_POL_INVERT)
+			val ^= 1;
+		input_report_key(priv->pwr, priv->keymap[2], val);
+		break;
+	}
+
+	input_sync(priv->pwr);
+
+	return IRQ_HANDLED;
+}
+
+static int mc13783_pwrbutton_probe(struct platform_device *pdev)
+{
+	const struct mc13xxx_buttons_platform_data *pdata;
+	struct mc13xxx *mc13783 = dev_get_drvdata(pdev->dev.parent);
+	struct input_dev *pwr;
+	struct mc13783_pwrb *priv;
+	int err = 0;
+	int reg = 0;
+
+	pdata = dev_get_platdata(&pdev->dev);
+	if (!pdata) {
+		dev_err(&pdev->dev, "missing platform data\n");
+		return -ENODEV;
+	}
+
+	pwr = input_allocate_device();
+	if (!pwr) {
+		dev_dbg(&pdev->dev, "Can't allocate power button\n");
+		return -ENOMEM;
+	}
+
+	priv = kzalloc_obj(*priv);
+	if (!priv) {
+		err = -ENOMEM;
+		dev_dbg(&pdev->dev, "Can't allocate power button\n");
+		goto free_input_dev;
+	}
+
+	reg |= (pdata->b1on_flags & 0x3) << MC13783_POWER_CONTROL_2_ON1BDBNC;
+	reg |= (pdata->b2on_flags & 0x3) << MC13783_POWER_CONTROL_2_ON2BDBNC;
+	reg |= (pdata->b3on_flags & 0x3) << MC13783_POWER_CONTROL_2_ON3BDBNC;
+
+	priv->pwr = pwr;
+	priv->mc13783 = mc13783;
+
+	mc13xxx_lock(mc13783);
+
+	if (pdata->b1on_flags & MC13783_BUTTON_ENABLE) {
+		priv->keymap[0] = pdata->b1on_key;
+		if (pdata->b1on_key != KEY_RESERVED)
+			__set_bit(pdata->b1on_key, pwr->keybit);
+
+		if (pdata->b1on_flags & MC13783_BUTTON_POL_INVERT)
+			priv->flags |= MC13783_PWRB_B1_POL_INVERT;
+
+		if (pdata->b1on_flags & MC13783_BUTTON_RESET_EN)
+			reg |= MC13783_POWER_CONTROL_2_ON1BRSTEN;
+
+		err = mc13xxx_irq_request(mc13783, MC13783_IRQ_ONOFD1,
+					  button_irq, "b1on", priv);
+		if (err) {
+			dev_dbg(&pdev->dev, "Can't request irq\n");
+			goto free_priv;
+		}
+	}
+
+	if (pdata->b2on_flags & MC13783_BUTTON_ENABLE) {
+		priv->keymap[1] = pdata->b2on_key;
+		if (pdata->b2on_key != KEY_RESERVED)
+			__set_bit(pdata->b2on_key, pwr->keybit);
+
+		if (pdata->b2on_flags & MC13783_BUTTON_POL_INVERT)
+			priv->flags |= MC13783_PWRB_B2_POL_INVERT;
+
+		if (pdata->b2on_flags & MC13783_BUTTON_RESET_EN)
+			reg |= MC13783_POWER_CONTROL_2_ON2BRSTEN;
+
+		err = mc13xxx_irq_request(mc13783, MC13783_IRQ_ONOFD2,
+					  button_irq, "b2on", priv);
+		if (err) {
+			dev_dbg(&pdev->dev, "Can't request irq\n");
+			goto free_irq_b1;
+		}
+	}
+
+	if (pdata->b3on_flags & MC13783_BUTTON_ENABLE) {
+		priv->keymap[2] = pdata->b3on_key;
+		if (pdata->b3on_key != KEY_RESERVED)
+			__set_bit(pdata->b3on_key, pwr->keybit);
+
+		if (pdata->b3on_flags & MC13783_BUTTON_POL_INVERT)
+			priv->flags |= MC13783_PWRB_B3_POL_INVERT;
+
+		if (pdata->b3on_flags & MC13783_BUTTON_RESET_EN)
+			reg |= MC13783_POWER_CONTROL_2_ON3BRSTEN;
+
+		err = mc13xxx_irq_request(mc13783, MC13783_IRQ_ONOFD3,
+					  button_irq, "b3on", priv);
+		if (err) {
+			dev_dbg(&pdev->dev, "Can't request irq: %d\n", err);
+			goto free_irq_b2;
+		}
+	}
+
+	mc13xxx_reg_rmw(mc13783, MC13783_REG_POWER_CONTROL_2, 0x3FE, reg);
+
+	mc13xxx_unlock(mc13783);
+
+	pwr->name = "mc13783_pwrbutton";
+	pwr->phys = "mc13783_pwrbutton/input0";
+	pwr->dev.parent = &pdev->dev;
+
+	pwr->keycode = priv->keymap;
+	pwr->keycodemax = ARRAY_SIZE(priv->keymap);
+	pwr->keycodesize = sizeof(priv->keymap[0]);
+	__set_bit(EV_KEY, pwr->evbit);
+
+	err = input_register_device(pwr);
+	if (err) {
+		dev_dbg(&pdev->dev, "Can't register power button: %d\n", err);
+		goto free_irq;
+	}
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+
+free_irq:
+	mc13xxx_lock(mc13783);
+
+	if (pdata->b3on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(mc13783, MC13783_IRQ_ONOFD3, priv);
+
+free_irq_b2:
+	if (pdata->b2on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(mc13783, MC13783_IRQ_ONOFD2, priv);
+
+free_irq_b1:
+	if (pdata->b1on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(mc13783, MC13783_IRQ_ONOFD1, priv);
+
+free_priv:
+	mc13xxx_unlock(mc13783);
+	kfree(priv);
+
+free_input_dev:
+	input_free_device(pwr);
+
+	return err;
+}
+
+static void mc13783_pwrbutton_remove(struct platform_device *pdev)
+{
+	struct mc13783_pwrb *priv = platform_get_drvdata(pdev);
+	const struct mc13xxx_buttons_platform_data *pdata;
+
+	pdata = dev_get_platdata(&pdev->dev);
+
+	mc13xxx_lock(priv->mc13783);
+
+	if (pdata->b3on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(priv->mc13783, MC13783_IRQ_ONOFD3, priv);
+	if (pdata->b2on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(priv->mc13783, MC13783_IRQ_ONOFD2, priv);
+	if (pdata->b1on_flags & MC13783_BUTTON_ENABLE)
+		mc13xxx_irq_free(priv->mc13783, MC13783_IRQ_ONOFD1, priv);
+
+	mc13xxx_unlock(priv->mc13783);
+
+	input_unregister_device(priv->pwr);
+	kfree(priv);
+}
+
+static struct platform_driver mc13783_pwrbutton_driver = {
+	.probe		= mc13783_pwrbutton_probe,
+	.remove		= mc13783_pwrbutton_remove,
+	.driver		= {
+		.name	= "mc13783-pwrbutton",
+	},
+};
+
+module_platform_driver(mc13783_pwrbutton_driver);
+
+MODULE_ALIAS("platform:mc13783-pwrbutton");
+MODULE_DESCRIPTION("MC13783 Power Button");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Philippe Retornaz");