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, 101 insertions, 0 deletions

diff --git a/scripts/kconfig/lxdialog/yesno.c b/scripts/kconfig/lxdialog/yesno.c
new file mode 100644
index 000000000..b57d25e15
--- /dev/null
+++ b/scripts/kconfig/lxdialog/yesno.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  yesno.c -- implements the yes/no box
+ *
+ *  ORIGINAL AUTHOR: Savio Lam (lam836@cs.cuhk.hk)
+ *  MODIFIED FOR LINUX KERNEL CONFIG BY: William Roadcap (roadcap@cfw.com)
+ */
+
+#include "dialog.h"
+
+/*
+ * Display termination buttons
+ */
+static void print_buttons(WINDOW * dialog, int height, int width, int selected)
+{
+	int x = width / 2 - 10;
+	int y = height - 2;
+
+	print_button(dialog, " Yes ", y, x, selected == 0);
+	print_button(dialog, "  No  ", y, x + 13, selected == 1);
+
+	wmove(dialog, y, x + 1 + 13 * selected);
+	wrefresh(dialog);
+}
+
+/*
+ * Display a dialog box with two buttons - Yes and No
+ */
+int dialog_yesno(const char *title, const char *prompt, int height, int width)
+{
+	int i, x, y, key = 0, button = 0;
+	WINDOW *dialog;
+
+do_resize:
+	if (getmaxy(stdscr) < (height + YESNO_HEIGHT_MIN))
+		return -ERRDISPLAYTOOSMALL;
+	if (getmaxx(stdscr) < (width + YESNO_WIDTH_MIN))
+		return -ERRDISPLAYTOOSMALL;
+
+	/* center dialog box on screen */
+	x = (getmaxx(stdscr) - width) / 2;
+	y = (getmaxy(stdscr) - height) / 2;
+
+	draw_shadow(stdscr, y, x, height, width);
+
+	dialog = newwin(height, width, y, x);
+	keypad(dialog, TRUE);
+
+	draw_box(dialog, 0, 0, height, width,
+		 dlg.dialog.atr, dlg.border.atr);
+	wattrset(dialog, dlg.border.atr);
+	mvwaddch(dialog, height - 3, 0, ACS_LTEE);
+	for (i = 0; i < width - 2; i++)
+		waddch(dialog, ACS_HLINE);
+	wattrset(dialog, dlg.dialog.atr);
+	waddch(dialog, ACS_RTEE);
+
+	print_title(dialog, title, width);
+
+	wattrset(dialog, dlg.dialog.atr);
+	print_autowrap(dialog, prompt, width - 2, 1, 3);
+
+	print_buttons(dialog, height, width, 0);
+
+	while (key != KEY_ESC) {
+		key = wgetch(dialog);
+		switch (key) {
+		case 'Y':
+		case 'y':
+			delwin(dialog);
+			return 0;
+		case 'N':
+		case 'n':
+			delwin(dialog);
+			return 1;
+
+		case TAB:
+		case KEY_LEFT:
+		case KEY_RIGHT:
+			button = ((key == KEY_LEFT ? --button : ++button) < 0) ? 1 : (button > 1 ? 0 : button);
+
+			print_buttons(dialog, height, width, button);
+			wrefresh(dialog);
+			break;
+		case ' ':
+		case '\n':
+			delwin(dialog);
+			return button;
+		case KEY_ESC:
+			key = on_key_esc(dialog);
+			break;
+		case KEY_RESIZE:
+			delwin(dialog);
+			on_key_resize();
+			goto do_resize;
+		}
+	}
+
+	delwin(dialog);
+	return key;		/* ESC pressed */
+}