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, 494 insertions, 0 deletions

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
new file mode 100644
index 000000000..9f0546535
--- /dev/null
+++ b/drivers/hid/hid-bigbenff.c
@@ -0,0 +1,494 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  LED & force feedback support for BigBen Interactive
+ *
+ *  0x146b:0x0902 "Bigben Interactive Bigben Game Pad"
+ *  "Kid-friendly Wired Controller" PS3OFMINIPAD SONY
+ *  sold for use with the PS3
+ *
+ *  Copyright (c) 2018 Hanno Zulla <kontakt@hanno.de>
+ */
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/leds.h>
+#include <linux/hid.h>
+
+#include "hid-ids.h"
+
+
+/*
+ * The original descriptor for 0x146b:0x0902
+ *
+ *   0x05, 0x01,        // Usage Page (Generic Desktop Ctrls)
+ *   0x09, 0x05,        // Usage (Game Pad)
+ *   0xA1, 0x01,        // Collection (Application)
+ *   0x15, 0x00,        //   Logical Minimum (0)
+ *   0x25, 0x01,        //   Logical Maximum (1)
+ *   0x35, 0x00,        //   Physical Minimum (0)
+ *   0x45, 0x01,        //   Physical Maximum (1)
+ *   0x75, 0x01,        //   Report Size (1)
+ *   0x95, 0x0D,        //   Report Count (13)
+ *   0x05, 0x09,        //   Usage Page (Button)
+ *   0x19, 0x01,        //   Usage Minimum (0x01)
+ *   0x29, 0x0D,        //   Usage Maximum (0x0D)
+ *   0x81, 0x02,        //   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0x95, 0x03,        //   Report Count (3)
+ *   0x81, 0x01,        //   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0x05, 0x01,        //   Usage Page (Generic Desktop Ctrls)
+ *   0x25, 0x07,        //   Logical Maximum (7)
+ *   0x46, 0x3B, 0x01,  //   Physical Maximum (315)
+ *   0x75, 0x04,        //   Report Size (4)
+ *   0x95, 0x01,        //   Report Count (1)
+ *   0x65, 0x14,        //   Unit (System: English Rotation, Length: Centimeter)
+ *   0x09, 0x39,        //   Usage (Hat switch)
+ *   0x81, 0x42,        //   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,Null State)
+ *   0x65, 0x00,        //   Unit (None)
+ *   0x95, 0x01,        //   Report Count (1)
+ *   0x81, 0x01,        //   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0x26, 0xFF, 0x00,  //   Logical Maximum (255)
+ *   0x46, 0xFF, 0x00,  //   Physical Maximum (255)
+ *   0x09, 0x30,        //   Usage (X)
+ *   0x09, 0x31,        //   Usage (Y)
+ *   0x09, 0x32,        //   Usage (Z)
+ *   0x09, 0x35,        //   Usage (Rz)
+ *   0x75, 0x08,        //   Report Size (8)
+ *   0x95, 0x04,        //   Report Count (4)
+ *   0x81, 0x02,        //   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0x06, 0x00, 0xFF,  //   Usage Page (Vendor Defined 0xFF00)
+ *   0x09, 0x20,        //   Usage (0x20)
+ *   0x09, 0x21,        //   Usage (0x21)
+ *   0x09, 0x22,        //   Usage (0x22)
+ *   0x09, 0x23,        //   Usage (0x23)
+ *   0x09, 0x24,        //   Usage (0x24)
+ *   0x09, 0x25,        //   Usage (0x25)
+ *   0x09, 0x26,        //   Usage (0x26)
+ *   0x09, 0x27,        //   Usage (0x27)
+ *   0x09, 0x28,        //   Usage (0x28)
+ *   0x09, 0x29,        //   Usage (0x29)
+ *   0x09, 0x2A,        //   Usage (0x2A)
+ *   0x09, 0x2B,        //   Usage (0x2B)
+ *   0x95, 0x0C,        //   Report Count (12)
+ *   0x81, 0x02,        //   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0x0A, 0x21, 0x26,  //   Usage (0x2621)
+ *   0x95, 0x08,        //   Report Count (8)
+ *   0xB1, 0x02,        //   Feature (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile)
+ *   0x0A, 0x21, 0x26,  //   Usage (0x2621)
+ *   0x91, 0x02,        //   Output (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile)
+ *   0x26, 0xFF, 0x03,  //   Logical Maximum (1023)
+ *   0x46, 0xFF, 0x03,  //   Physical Maximum (1023)
+ *   0x09, 0x2C,        //   Usage (0x2C)
+ *   0x09, 0x2D,        //   Usage (0x2D)
+ *   0x09, 0x2E,        //   Usage (0x2E)
+ *   0x09, 0x2F,        //   Usage (0x2F)
+ *   0x75, 0x10,        //   Report Size (16)
+ *   0x95, 0x04,        //   Report Count (4)
+ *   0x81, 0x02,        //   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+ *   0xC0,              // End Collection
+ */
+
+#define PID0902_RDESC_ORIG_SIZE 137
+
+/*
+ * The fixed descriptor for 0x146b:0x0902
+ *
+ * - map buttons according to gamepad.rst
+ * - assign right stick from Z/Rz to Rx/Ry
+ * - map previously unused analog trigger data to Z/RZ
+ * - simplify feature and output descriptor
+ */
+static const __u8 pid0902_rdesc_fixed[] = {
+	0x05, 0x01,        /* Usage Page (Generic Desktop Ctrls) */
+	0x09, 0x05,        /* Usage (Game Pad) */
+	0xA1, 0x01,        /* Collection (Application) */
+	0x15, 0x00,        /*   Logical Minimum (0) */
+	0x25, 0x01,        /*   Logical Maximum (1) */
+	0x35, 0x00,        /*   Physical Minimum (0) */
+	0x45, 0x01,        /*   Physical Maximum (1) */
+	0x75, 0x01,        /*   Report Size (1) */
+	0x95, 0x0D,        /*   Report Count (13) */
+	0x05, 0x09,        /*   Usage Page (Button) */
+	0x09, 0x05,        /*   Usage (BTN_WEST) */
+	0x09, 0x01,        /*   Usage (BTN_SOUTH) */
+	0x09, 0x02,        /*   Usage (BTN_EAST) */
+	0x09, 0x04,        /*   Usage (BTN_NORTH) */
+	0x09, 0x07,        /*   Usage (BTN_TL) */
+	0x09, 0x08,        /*   Usage (BTN_TR) */
+	0x09, 0x09,        /*   Usage (BTN_TL2) */
+	0x09, 0x0A,        /*   Usage (BTN_TR2) */
+	0x09, 0x0B,        /*   Usage (BTN_SELECT) */
+	0x09, 0x0C,        /*   Usage (BTN_START) */
+	0x09, 0x0E,        /*   Usage (BTN_THUMBL) */
+	0x09, 0x0F,        /*   Usage (BTN_THUMBR) */
+	0x09, 0x0D,        /*   Usage (BTN_MODE) */
+	0x81, 0x02,        /*   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x75, 0x01,        /*   Report Size (1) */
+	0x95, 0x03,        /*   Report Count (3) */
+	0x81, 0x01,        /*   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x05, 0x01,        /*   Usage Page (Generic Desktop Ctrls) */
+	0x25, 0x07,        /*   Logical Maximum (7) */
+	0x46, 0x3B, 0x01,  /*   Physical Maximum (315) */
+	0x75, 0x04,        /*   Report Size (4) */
+	0x95, 0x01,        /*   Report Count (1) */
+	0x65, 0x14,        /*   Unit (System: English Rotation, Length: Centimeter) */
+	0x09, 0x39,        /*   Usage (Hat switch) */
+	0x81, 0x42,        /*   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,Null State) */
+	0x65, 0x00,        /*   Unit (None) */
+	0x95, 0x01,        /*   Report Count (1) */
+	0x81, 0x01,        /*   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x26, 0xFF, 0x00,  /*   Logical Maximum (255) */
+	0x46, 0xFF, 0x00,  /*   Physical Maximum (255) */
+	0x09, 0x30,        /*   Usage (X) */
+	0x09, 0x31,        /*   Usage (Y) */
+	0x09, 0x33,        /*   Usage (Rx) */
+	0x09, 0x34,        /*   Usage (Ry) */
+	0x75, 0x08,        /*   Report Size (8) */
+	0x95, 0x04,        /*   Report Count (4) */
+	0x81, 0x02,        /*   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x95, 0x0A,        /*   Report Count (10) */
+	0x81, 0x01,        /*   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x05, 0x01,        /*   Usage Page (Generic Desktop Ctrls) */
+	0x26, 0xFF, 0x00,  /*   Logical Maximum (255) */
+	0x46, 0xFF, 0x00,  /*   Physical Maximum (255) */
+	0x09, 0x32,        /*   Usage (Z) */
+	0x09, 0x35,        /*   Usage (Rz) */
+	0x95, 0x02,        /*   Report Count (2) */
+	0x81, 0x02,        /*   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x95, 0x08,        /*   Report Count (8) */
+	0x81, 0x01,        /*   Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0x06, 0x00, 0xFF,  /*   Usage Page (Vendor Defined 0xFF00) */
+	0xB1, 0x02,        /*   Feature (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile) */
+	0x0A, 0x21, 0x26,  /*   Usage (0x2621) */
+	0x95, 0x08,        /*   Report Count (8) */
+	0x91, 0x02,        /*   Output (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile) */
+	0x0A, 0x21, 0x26,  /*   Usage (0x2621) */
+	0x95, 0x08,        /*   Report Count (8) */
+	0x81, 0x02,        /*   Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position) */
+	0xC0,              /* End Collection */
+};
+
+#define NUM_LEDS 4
+
+struct bigben_device {
+	struct hid_device *hid;
+	struct hid_report *report;
+	spinlock_t lock;
+	bool removed;
+	u8 led_state;         /* LED1 = 1 .. LED4 = 8 */
+	u8 right_motor_on;    /* right motor off/on 0/1 */
+	u8 left_motor_force;  /* left motor force 0-255 */
+	struct led_classdev *leds[NUM_LEDS];
+	bool work_led;
+	bool work_ff;
+	struct work_struct worker;
+};
+
+static inline void bigben_schedule_work(struct bigben_device *bigben)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&bigben->lock, flags);
+	if (!bigben->removed)
+		schedule_work(&bigben->worker);
+	spin_unlock_irqrestore(&bigben->lock, flags);
+}
+
+static void bigben_worker(struct work_struct *work)
+{
+	struct bigben_device *bigben = container_of(work,
+		struct bigben_device, worker);
+	struct hid_field *report_field = bigben->report->field[0];
+	bool do_work_led = false;
+	bool do_work_ff = false;
+	u8 *buf;
+	u32 len;
+	unsigned long flags;
+
+	buf = hid_alloc_report_buf(bigben->report, GFP_KERNEL);
+	if (!buf)
+		return;
+
+	len = hid_report_len(bigben->report);
+
+	/* LED work */
+	spin_lock_irqsave(&bigben->lock, flags);
+
+	if (bigben->work_led) {
+		bigben->work_led = false;
+		do_work_led = true;
+		report_field->value[0] = 0x01; /* 1 = led message */
+		report_field->value[1] = 0x08; /* reserved value, always 8 */
+		report_field->value[2] = bigben->led_state;
+		report_field->value[3] = 0x00; /* padding */
+		report_field->value[4] = 0x00; /* padding */
+		report_field->value[5] = 0x00; /* padding */
+		report_field->value[6] = 0x00; /* padding */
+		report_field->value[7] = 0x00; /* padding */
+		hid_output_report(bigben->report, buf);
+	}
+
+	spin_unlock_irqrestore(&bigben->lock, flags);
+
+	if (do_work_led) {
+		hid_hw_raw_request(bigben->hid, bigben->report->id, buf, len,
+				   bigben->report->type, HID_REQ_SET_REPORT);
+	}
+
+	/* FF work */
+	spin_lock_irqsave(&bigben->lock, flags);
+
+	if (bigben->work_ff) {
+		bigben->work_ff = false;
+		do_work_ff = true;
+		report_field->value[0] = 0x02; /* 2 = rumble effect message */
+		report_field->value[1] = 0x08; /* reserved value, always 8 */
+		report_field->value[2] = bigben->right_motor_on;
+		report_field->value[3] = bigben->left_motor_force;
+		report_field->value[4] = 0xff; /* duration 0-254 (255 = nonstop) */
+		report_field->value[5] = 0x00; /* padding */
+		report_field->value[6] = 0x00; /* padding */
+		report_field->value[7] = 0x00; /* padding */
+		hid_output_report(bigben->report, buf);
+	}
+
+	spin_unlock_irqrestore(&bigben->lock, flags);
+
+	if (do_work_ff) {
+		hid_hw_raw_request(bigben->hid, bigben->report->id, buf, len,
+				   bigben->report->type, HID_REQ_SET_REPORT);
+	}
+
+	kfree(buf);
+}
+
+static int hid_bigben_play_effect(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct bigben_device *bigben = hid_get_drvdata(hid);
+	u8 right_motor_on;
+	u8 left_motor_force;
+	unsigned long flags;
+
+	if (!bigben) {
+		hid_err(hid, "no device data\n");
+		return 0;
+	}
+
+	if (effect->type != FF_RUMBLE)
+		return 0;
+
+	right_motor_on   = effect->u.rumble.weak_magnitude ? 1 : 0;
+	left_motor_force = effect->u.rumble.strong_magnitude / 256;
+
+	if (right_motor_on != bigben->right_motor_on ||
+			left_motor_force != bigben->left_motor_force) {
+		spin_lock_irqsave(&bigben->lock, flags);
+		bigben->right_motor_on   = right_motor_on;
+		bigben->left_motor_force = left_motor_force;
+		bigben->work_ff = true;
+		spin_unlock_irqrestore(&bigben->lock, flags);
+
+		bigben_schedule_work(bigben);
+	}
+
+	return 0;
+}
+
+static void bigben_set_led(struct led_classdev *led,
+	enum led_brightness value)
+{
+	struct device *dev = led->dev->parent;
+	struct hid_device *hid = to_hid_device(dev);
+	struct bigben_device *bigben = hid_get_drvdata(hid);
+	int n;
+	bool work;
+	unsigned long flags;
+
+	if (!bigben) {
+		hid_err(hid, "no device data\n");
+		return;
+	}
+
+	for (n = 0; n < NUM_LEDS; n++) {
+		if (led == bigben->leds[n]) {
+			spin_lock_irqsave(&bigben->lock, flags);
+			if (value == LED_OFF) {
+				work = (bigben->led_state & BIT(n));
+				bigben->led_state &= ~BIT(n);
+			} else {
+				work = !(bigben->led_state & BIT(n));
+				bigben->led_state |= BIT(n);
+			}
+			spin_unlock_irqrestore(&bigben->lock, flags);
+
+			if (work) {
+				bigben->work_led = true;
+				bigben_schedule_work(bigben);
+			}
+			return;
+		}
+	}
+}
+
+static enum led_brightness bigben_get_led(struct led_classdev *led)
+{
+	struct device *dev = led->dev->parent;
+	struct hid_device *hid = to_hid_device(dev);
+	struct bigben_device *bigben = hid_get_drvdata(hid);
+	int n;
+
+	if (!bigben) {
+		hid_err(hid, "no device data\n");
+		return LED_OFF;
+	}
+
+	for (n = 0; n < NUM_LEDS; n++) {
+		if (led == bigben->leds[n])
+			return (bigben->led_state & BIT(n)) ? LED_ON : LED_OFF;
+	}
+
+	return LED_OFF;
+}
+
+static void bigben_remove(struct hid_device *hid)
+{
+	struct bigben_device *bigben = hid_get_drvdata(hid);
+	unsigned long flags;
+
+	spin_lock_irqsave(&bigben->lock, flags);
+	bigben->removed = true;
+	spin_unlock_irqrestore(&bigben->lock, flags);
+
+	cancel_work_sync(&bigben->worker);
+	hid_hw_stop(hid);
+}
+
+static int bigben_probe(struct hid_device *hid,
+	const struct hid_device_id *id)
+{
+	struct bigben_device *bigben;
+	struct hid_input *hidinput;
+	struct led_classdev *led;
+	char *name;
+	size_t name_sz;
+	int n, error;
+
+	bigben = devm_kzalloc(&hid->dev, sizeof(*bigben), GFP_KERNEL);
+	if (!bigben)
+		return -ENOMEM;
+	hid_set_drvdata(hid, bigben);
+	bigben->hid = hid;
+	bigben->removed = false;
+
+	error = hid_parse(hid);
+	if (error) {
+		hid_err(hid, "parse failed\n");
+		return error;
+	}
+
+	error = hid_hw_start(hid, HID_CONNECT_DEFAULT & ~HID_CONNECT_FF);
+	if (error) {
+		hid_err(hid, "hw start failed\n");
+		return error;
+	}
+
+	bigben->report = hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 8);
+	if (!bigben->report) {
+		hid_err(hid, "no output report found\n");
+		error = -ENODEV;
+		goto error_hw_stop;
+	}
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		error = -ENODEV;
+		goto error_hw_stop;
+	}
+
+	hidinput = list_first_entry(&hid->inputs, struct hid_input, list);
+	set_bit(FF_RUMBLE, hidinput->input->ffbit);
+
+	INIT_WORK(&bigben->worker, bigben_worker);
+	spin_lock_init(&bigben->lock);
+
+	error = input_ff_create_memless(hidinput->input, NULL,
+		hid_bigben_play_effect);
+	if (error)
+		goto error_hw_stop;
+
+	name_sz = strlen(dev_name(&hid->dev)) + strlen(":red:bigben#") + 1;
+
+	for (n = 0; n < NUM_LEDS; n++) {
+		led = devm_kzalloc(
+			&hid->dev,
+			sizeof(struct led_classdev) + name_sz,
+			GFP_KERNEL
+		);
+		if (!led) {
+			error = -ENOMEM;
+			goto error_hw_stop;
+		}
+		name = (void *)(&led[1]);
+		snprintf(name, name_sz,
+			"%s:red:bigben%d",
+			dev_name(&hid->dev), n + 1
+		);
+		led->name = name;
+		led->brightness = (n == 0) ? LED_ON : LED_OFF;
+		led->max_brightness = 1;
+		led->brightness_get = bigben_get_led;
+		led->brightness_set = bigben_set_led;
+		bigben->leds[n] = led;
+		error = devm_led_classdev_register(&hid->dev, led);
+		if (error)
+			goto error_hw_stop;
+	}
+
+	/* initial state: LED1 is on, no rumble effect */
+	bigben->led_state = BIT(0);
+	bigben->right_motor_on = 0;
+	bigben->left_motor_force = 0;
+	bigben->work_led = true;
+	bigben->work_ff = true;
+	bigben_schedule_work(bigben);
+
+	hid_info(hid, "LED and force feedback support for BigBen gamepad\n");
+
+	return 0;
+
+error_hw_stop:
+	hid_hw_stop(hid);
+	return error;
+}
+
+static const __u8 *bigben_report_fixup(struct hid_device *hid, __u8 *rdesc,
+	unsigned int *rsize)
+{
+	if (*rsize == PID0902_RDESC_ORIG_SIZE) {
+		*rsize = sizeof(pid0902_rdesc_fixed);
+		return pid0902_rdesc_fixed;
+	} else
+		hid_warn(hid, "unexpected rdesc, please submit for review\n");
+	return rdesc;
+}
+
+static const struct hid_device_id bigben_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_BIGBEN, USB_DEVICE_ID_BIGBEN_PS3OFMINIPAD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, bigben_devices);
+
+static struct hid_driver bigben_driver = {
+	.name = "bigben",
+	.id_table = bigben_devices,
+	.probe = bigben_probe,
+	.report_fixup = bigben_report_fixup,
+	.remove = bigben_remove,
+};
+module_hid_driver(bigben_driver);
+
+MODULE_DESCRIPTION("LED & force feedback support for BigBen Interactive");
+MODULE_LICENSE("GPL");