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, 148 insertions, 0 deletions

diff --git a/drivers/hid/hid-ite.c b/drivers/hid/hid-ite.c
new file mode 100644
index 000000000..63908f24b
--- /dev/null
+++ b/drivers/hid/hid-ite.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver for some ITE "special" devices
+ * Copyright (c) 2017 Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define QUIRK_TOUCHPAD_ON_OFF_REPORT		BIT(0)
+
+static const __u8 *ite_report_fixup(struct hid_device *hdev, __u8 *rdesc, unsigned int *rsize)
+{
+
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if (quirks & QUIRK_TOUCHPAD_ON_OFF_REPORT) {
+		/* For Acer Aspire Switch 10 SW5-012 keyboard-dock */
+		if (*rsize == 188 && rdesc[162] == 0x81 && rdesc[163] == 0x02) {
+			hid_info(hdev, "Fixing up Acer Sw5-012 ITE keyboard report descriptor\n");
+			rdesc[163] = HID_MAIN_ITEM_RELATIVE;
+		}
+		/* For Acer One S1002/S1003 keyboard-dock */
+		if (*rsize == 188 && rdesc[185] == 0x81 && rdesc[186] == 0x02) {
+			hid_info(hdev, "Fixing up Acer S1002/S1003 ITE keyboard report descriptor\n");
+			rdesc[186] = HID_MAIN_ITEM_RELATIVE;
+		}
+		/* For Acer Aspire Switch 10E (SW3-016) keyboard-dock */
+		if (*rsize == 210 && rdesc[184] == 0x81 && rdesc[185] == 0x02) {
+			hid_info(hdev, "Fixing up Acer Aspire Switch 10E (SW3-016) ITE keyboard report descriptor\n");
+			rdesc[185] = HID_MAIN_ITEM_RELATIVE;
+		}
+	}
+
+	return rdesc;
+}
+
+static int ite_input_mapping(struct hid_device *hdev,
+		struct hid_input *hi, struct hid_field *field,
+		struct hid_usage *usage, unsigned long **bit,
+		int *max)
+{
+
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if ((quirks & QUIRK_TOUCHPAD_ON_OFF_REPORT) &&
+	    (usage->hid & HID_USAGE_PAGE) == 0x00880000) {
+		if (usage->hid == 0x00880078) {
+			/* Touchpad on, userspace expects F22 for this */
+			hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_F22);
+			return 1;
+		}
+		if (usage->hid == 0x00880079) {
+			/* Touchpad off, userspace expects F23 for this */
+			hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_F23);
+			return 1;
+		}
+		return -1;
+	}
+
+	return 0;
+}
+
+static int ite_event(struct hid_device *hdev, struct hid_field *field,
+		     struct hid_usage *usage, __s32 value)
+{
+	struct input_dev *input;
+
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !field->hidinput)
+		return 0;
+
+	input = field->hidinput->input;
+
+	/*
+	 * The ITE8595 always reports 0 as value for the rfkill button. Luckily
+	 * it is the only button in its report, and it sends a report on
+	 * release only, so receiving a report means the button was pressed.
+	 */
+	if (usage->hid == HID_GD_RFKILL_BTN) {
+		input_event(input, EV_KEY, KEY_RFKILL, 1);
+		input_sync(input);
+		input_event(input, EV_KEY, KEY_RFKILL, 0);
+		input_sync(input);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int ite_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	hid_set_drvdata(hdev, (void *)id);
+
+	ret = hid_open_report(hdev);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id ite_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ITE, USB_DEVICE_ID_ITE8595) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_258A, USB_DEVICE_ID_258A_6A88) },
+	/* ITE8595 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_SWITCH5_012),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_ONE_S1002),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_ONE_S1003),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_SWITCH5_017),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, ite_devices);
+
+static struct hid_driver ite_driver = {
+	.name = "itetech",
+	.id_table = ite_devices,
+	.probe = ite_probe,
+	.report_fixup = ite_report_fixup,
+	.input_mapping = ite_input_mapping,
+	.event = ite_event,
+};
+module_hid_driver(ite_driver);
+
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_DESCRIPTION("HID driver for some ITE \"special\" devices");
+MODULE_LICENSE("GPL");