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, 98 insertions, 0 deletions

diff --git a/drivers/hid/hid-glorious.c b/drivers/hid/hid-glorious.c
new file mode 100644
index 000000000..5bbd81248
--- /dev/null
+++ b/drivers/hid/hid-glorious.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  USB HID driver for Glorious PC Gaming Race
+ *  Glorious Model O, O- and D mice.
+ *
+ *  Copyright (c) 2020 Samuel Čavoj <sammko@sammserver.com>
+ */
+
+/*
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+MODULE_AUTHOR("Samuel Čavoj <sammko@sammserver.com>");
+MODULE_DESCRIPTION("HID driver for Glorious PC Gaming Race mice");
+
+/*
+ * Glorious Model O and O- specify the const flag in the consumer input
+ * report descriptor, which leads to inputs being ignored. Fix this
+ * by patching the descriptor.
+ *
+ * Glorious Model I incorrectly specifes the Usage Minimum for its
+ * keyboard HID report, causing keycodes to be misinterpreted.
+ * Fix this by setting Usage Minimum to 0 in that report.
+ */
+static const __u8 *glorious_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	if (*rsize == 213 &&
+		rdesc[84] == 129 && rdesc[112] == 129 && rdesc[140] == 129 &&
+		rdesc[85] == 3   && rdesc[113] == 3   && rdesc[141] == 3) {
+		hid_info(hdev, "patching Glorious Model O consumer control report descriptor\n");
+		rdesc[85] = rdesc[113] = rdesc[141] = \
+			HID_MAIN_ITEM_VARIABLE | HID_MAIN_ITEM_RELATIVE;
+	}
+	if (*rsize == 156 && rdesc[41] == 1) {
+		hid_info(hdev, "patching Glorious Model I keyboard report descriptor\n");
+		rdesc[41] = 0;
+	}
+	return rdesc;
+}
+
+static void glorious_update_name(struct hid_device *hdev)
+{
+	const char *model = "Device";
+
+	switch (hdev->product) {
+	case USB_DEVICE_ID_GLORIOUS_MODEL_O:
+		model = "Model O"; break;
+	case USB_DEVICE_ID_GLORIOUS_MODEL_D:
+		model = "Model D"; break;
+	case USB_DEVICE_ID_GLORIOUS_MODEL_I:
+		model = "Model I"; break;
+	}
+
+	snprintf(hdev->name, sizeof(hdev->name), "%s %s", "Glorious", model);
+}
+
+static int glorious_probe(struct hid_device *hdev,
+		const struct hid_device_id *id)
+{
+	int ret;
+
+	hdev->quirks |= HID_QUIRK_INPUT_PER_APP;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	glorious_update_name(hdev);
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id glorious_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SINOWEALTH,
+		USB_DEVICE_ID_GLORIOUS_MODEL_O) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SINOWEALTH,
+		USB_DEVICE_ID_GLORIOUS_MODEL_D) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LAVIEW,
+		USB_DEVICE_ID_GLORIOUS_MODEL_I) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, glorious_devices);
+
+static struct hid_driver glorious_driver = {
+	.name = "glorious",
+	.id_table = glorious_devices,
+	.probe = glorious_probe,
+	.report_fixup = glorious_report_fixup
+};
+
+module_hid_driver(glorious_driver);
+
+MODULE_LICENSE("GPL");