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, 55 insertions, 0 deletions

diff --git a/drivers/hid/hid-ortek.c b/drivers/hid/hid-ortek.c
new file mode 100644
index 000000000..f27297269
--- /dev/null
+++ b/drivers/hid/hid-ortek.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for various devices which are apparently based on the same chipset
+ *  from certain vendor which produces chips that contain wrong LogicalMaximum
+ *  value in their HID report descriptor. Currently supported devices are:
+ *
+ *    Ortek PKB-1700
+ *    Ortek WKB-2000
+ *    iHome IMAC-A210S
+ *    Skycable wireless presenter
+ *
+ *  Copyright (c) 2010 Johnathon Harris <jmharris@gmail.com>
+ *  Copyright (c) 2011 Jiri Kosina
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static const __u8 *ortek_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	if (*rsize >= 56 && rdesc[54] == 0x25 && rdesc[55] == 0x01) {
+		hid_info(hdev, "Fixing up logical maximum in report descriptor (Ortek)\n");
+		rdesc[55] = 0x92;
+	} else if (*rsize >= 54 && rdesc[52] == 0x25 && rdesc[53] == 0x01) {
+		hid_info(hdev, "Fixing up logical maximum in report descriptor (Skycable)\n");
+		rdesc[53] = 0x65;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id ortek_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ORTEK, USB_DEVICE_ID_ORTEK_PKB1700) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ORTEK, USB_DEVICE_ID_ORTEK_WKB2000) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ORTEK, USB_DEVICE_ID_ORTEK_IHOME_IMAC_A210S) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SKYCABLE, USB_DEVICE_ID_SKYCABLE_WIRELESS_PRESENTER) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, ortek_devices);
+
+static struct hid_driver ortek_driver = {
+	.name = "ortek",
+	.id_table = ortek_devices,
+	.report_fixup = ortek_report_fixup
+};
+module_hid_driver(ortek_driver);
+
+MODULE_DESCRIPTION("HID driver for Ortek PKB-1700/WKB-2000/Skycable wireless keyboard and mouse trackpad");
+MODULE_LICENSE("GPL");