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, 114 insertions, 0 deletions

diff --git a/drivers/hid/hid-holtek-mouse.c b/drivers/hid/hid-holtek-mouse.c
new file mode 100644
index 000000000..b618a1646
--- /dev/null
+++ b/drivers/hid/hid-holtek-mouse.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for Holtek gaming mice
+ * Copyright (c) 2013 Christian Ohm
+ * Heavily inspired by various other HID drivers that adjust the report
+ * descriptor.
+*/
+
+/*
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+
+#include "hid-ids.h"
+
+/*
+ * The report descriptor of some Holtek based gaming mice specifies an
+ * excessively large number of consumer usages (2^15), which is more than
+ * HID_MAX_USAGES. This prevents proper parsing of the report descriptor.
+ *
+ * This driver fixes the report descriptor for:
+ * - USB ID 04d9:a067, sold as Sharkoon Drakonia and Perixx MX-2000
+ * - USB ID 04d9:a04a, sold as Tracer Sniper TRM-503, NOVA Gaming Slider X200
+ *   and Zalman ZM-GM1
+ * - USB ID 04d9:a081, sold as SHARKOON DarkGlider Gaming mouse
+ * - USB ID 04d9:a072, sold as LEETGION Hellion Gaming Mouse
+ * - USB ID 04d9:a0c2, sold as ETEKCITY Scroll T-140 Gaming Mouse
+ */
+
+static const __u8 *holtek_mouse_report_fixup(struct hid_device *hdev,
+		__u8 *rdesc, unsigned int *rsize)
+{
+	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+
+	if (intf->cur_altsetting->desc.bInterfaceNumber == 1) {
+		/* Change usage maximum and logical maximum from 0x7fff to
+		 * 0x2fff, so they don't exceed HID_MAX_USAGES */
+		switch (hdev->product) {
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A067:
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A072:
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A0C2:
+			if (*rsize >= 122 && rdesc[115] == 0xff && rdesc[116] == 0x7f
+					&& rdesc[120] == 0xff && rdesc[121] == 0x7f) {
+				hid_info(hdev, "Fixing up report descriptor\n");
+				rdesc[116] = rdesc[121] = 0x2f;
+			}
+			break;
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A04A:
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A070:
+		case USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A081:
+			if (*rsize >= 113 && rdesc[106] == 0xff && rdesc[107] == 0x7f
+					&& rdesc[111] == 0xff && rdesc[112] == 0x7f) {
+				hid_info(hdev, "Fixing up report descriptor\n");
+				rdesc[107] = rdesc[112] = 0x2f;
+			}
+			break;
+		}
+
+	}
+	return rdesc;
+}
+
+static int holtek_mouse_probe(struct hid_device *hdev,
+			      const struct hid_device_id *id)
+{
+	int ret;
+
+	if (!hid_is_usb(hdev))
+		return -EINVAL;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "hid parse failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (ret) {
+		hid_err(hdev, "hw start failed: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id holtek_mouse_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A067) },
+        { HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A070) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A04A) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A072) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A081) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_MOUSE_A0C2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, holtek_mouse_devices);
+
+static struct hid_driver holtek_mouse_driver = {
+	.name = "holtek_mouse",
+	.id_table = holtek_mouse_devices,
+	.report_fixup = holtek_mouse_report_fixup,
+	.probe = holtek_mouse_probe,
+};
+
+module_hid_driver(holtek_mouse_driver);
+MODULE_DESCRIPTION("HID driver for Holtek gaming mice");
+MODULE_LICENSE("GPL");