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, 232 insertions, 0 deletions

diff --git a/drivers/input/keyboard/atakbd.c b/drivers/input/keyboard/atakbd.c
new file mode 100644
index 000000000..07e17e563
--- /dev/null
+++ b/drivers/input/keyboard/atakbd.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  atakbd.c
+ *
+ *  Copyright (c) 2005 Michael Schmitz
+ *
+ * Based on amikbd.c, which is
+ *
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *
+ *  Based on the work of:
+ *	Hamish Macdonald
+ */
+
+/*
+ * Atari keyboard driver for Linux/m68k
+ *
+ * The low level init and interrupt stuff is handled in arch/mm68k/atari/atakeyb.c
+ * (the keyboard ACIA also handles the mouse and joystick data, and the keyboard
+ * interrupt is shared with the MIDI ACIA so MIDI data also get handled there).
+ * This driver only deals with handing key events off to the input layer.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+
+#include <asm/atariints.h>
+#include <asm/atarihw.h>
+#include <asm/atarikb.h>
+#include <asm/irq.h>
+
+MODULE_AUTHOR("Michael Schmitz <schmitz@biophys.uni-duesseldorf.de>");
+MODULE_DESCRIPTION("Atari keyboard driver");
+MODULE_LICENSE("GPL");
+
+/*
+ 0x47: KP_7     71
+ 0x48: KP_8     72
+ 0x49: KP_9     73
+ 0x62: KP_/     98
+ 0x4b: KP_4     75
+ 0x4c: KP_5     76
+ 0x4d: KP_6     77
+ 0x37: KP_*     55
+ 0x4f: KP_1     79
+ 0x50: KP_2     80
+ 0x51: KP_3     81
+ 0x4a: KP_-     74
+ 0x52: KP_0     82
+ 0x53: KP_.     83
+ 0x4e: KP_+     78
+
+ 0x67: Up       103
+ 0x6c: Down     108
+ 0x69: Left     105
+ 0x6a: Right    106
+ */
+
+
+static unsigned char atakbd_keycode[0x73] = {	/* American layout */
+	[1]	 = KEY_ESC,
+	[2]	 = KEY_1,
+	[3]	 = KEY_2,
+	[4]	 = KEY_3,
+	[5]	 = KEY_4,
+	[6]	 = KEY_5,
+	[7]	 = KEY_6,
+	[8]	 = KEY_7,
+	[9]	 = KEY_8,
+	[10]	 = KEY_9,
+	[11]	 = KEY_0,
+	[12]	 = KEY_MINUS,
+	[13]	 = KEY_EQUAL,
+	[14]	 = KEY_BACKSPACE,
+	[15]	 = KEY_TAB,
+	[16]	 = KEY_Q,
+	[17]	 = KEY_W,
+	[18]	 = KEY_E,
+	[19]	 = KEY_R,
+	[20]	 = KEY_T,
+	[21]	 = KEY_Y,
+	[22]	 = KEY_U,
+	[23]	 = KEY_I,
+	[24]	 = KEY_O,
+	[25]	 = KEY_P,
+	[26]	 = KEY_LEFTBRACE,
+	[27]	 = KEY_RIGHTBRACE,
+	[28]	 = KEY_ENTER,
+	[29]	 = KEY_LEFTCTRL,
+	[30]	 = KEY_A,
+	[31]	 = KEY_S,
+	[32]	 = KEY_D,
+	[33]	 = KEY_F,
+	[34]	 = KEY_G,
+	[35]	 = KEY_H,
+	[36]	 = KEY_J,
+	[37]	 = KEY_K,
+	[38]	 = KEY_L,
+	[39]	 = KEY_SEMICOLON,
+	[40]	 = KEY_APOSTROPHE,
+	[41]	 = KEY_GRAVE,
+	[42]	 = KEY_LEFTSHIFT,
+	[43]	 = KEY_BACKSLASH,
+	[44]	 = KEY_Z,
+	[45]	 = KEY_X,
+	[46]	 = KEY_C,
+	[47]	 = KEY_V,
+	[48]	 = KEY_B,
+	[49]	 = KEY_N,
+	[50]	 = KEY_M,
+	[51]	 = KEY_COMMA,
+	[52]	 = KEY_DOT,
+	[53]	 = KEY_SLASH,
+	[54]	 = KEY_RIGHTSHIFT,
+	[55]	 = KEY_KPASTERISK,
+	[56]	 = KEY_LEFTALT,
+	[57]	 = KEY_SPACE,
+	[58]	 = KEY_CAPSLOCK,
+	[59]	 = KEY_F1,
+	[60]	 = KEY_F2,
+	[61]	 = KEY_F3,
+	[62]	 = KEY_F4,
+	[63]	 = KEY_F5,
+	[64]	 = KEY_F6,
+	[65]	 = KEY_F7,
+	[66]	 = KEY_F8,
+	[67]	 = KEY_F9,
+	[68]	 = KEY_F10,
+	[71]	 = KEY_HOME,
+	[72]	 = KEY_UP,
+	[74]	 = KEY_KPMINUS,
+	[75]	 = KEY_LEFT,
+	[77]	 = KEY_RIGHT,
+	[78]	 = KEY_KPPLUS,
+	[80]	 = KEY_DOWN,
+	[82]	 = KEY_INSERT,
+	[83]	 = KEY_DELETE,
+	[96]	 = KEY_102ND,
+	[97]	 = KEY_UNDO,
+	[98]	 = KEY_HELP,
+	[99]	 = KEY_KPLEFTPAREN,
+	[100]	 = KEY_KPRIGHTPAREN,
+	[101]	 = KEY_KPSLASH,
+	[102]	 = KEY_KPASTERISK,
+	[103]	 = KEY_KP7,
+	[104]	 = KEY_KP8,
+	[105]	 = KEY_KP9,
+	[106]	 = KEY_KP4,
+	[107]	 = KEY_KP5,
+	[108]	 = KEY_KP6,
+	[109]	 = KEY_KP1,
+	[110]	 = KEY_KP2,
+	[111]	 = KEY_KP3,
+	[112]	 = KEY_KP0,
+	[113]	 = KEY_KPDOT,
+	[114]	 = KEY_KPENTER,
+};
+
+static struct input_dev *atakbd_dev;
+
+static void atakbd_interrupt(unsigned char scancode, char down)
+{
+
+	if (scancode < 0x73) {		/* scancodes < 0xf3 are keys */
+
+		// report raw events here?
+
+		scancode = atakbd_keycode[scancode];
+
+		input_report_key(atakbd_dev, scancode, down);
+		input_sync(atakbd_dev);
+	} else				/* scancodes >= 0xf3 are mouse data, most likely */
+		printk(KERN_INFO "atakbd: unhandled scancode %x\n", scancode);
+
+	return;
+}
+
+static int __init atakbd_init(void)
+{
+	int i, error;
+
+	if (!MACH_IS_ATARI || !ATARIHW_PRESENT(ST_MFP))
+		return -ENODEV;
+
+	// need to init core driver if not already done so
+	error = atari_keyb_init();
+	if (error)
+		return error;
+
+	atakbd_dev = input_allocate_device();
+	if (!atakbd_dev)
+		return -ENOMEM;
+
+	atakbd_dev->name = "Atari Keyboard";
+	atakbd_dev->phys = "atakbd/input0";
+	atakbd_dev->id.bustype = BUS_HOST;
+	atakbd_dev->id.vendor = 0x0001;
+	atakbd_dev->id.product = 0x0001;
+	atakbd_dev->id.version = 0x0100;
+
+	atakbd_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+	atakbd_dev->keycode = atakbd_keycode;
+	atakbd_dev->keycodesize = sizeof(unsigned char);
+	atakbd_dev->keycodemax = ARRAY_SIZE(atakbd_keycode);
+
+	for (i = 1; i < 0x72; i++) {
+		set_bit(atakbd_keycode[i], atakbd_dev->keybit);
+	}
+
+	/* error check */
+	error = input_register_device(atakbd_dev);
+	if (error) {
+		input_free_device(atakbd_dev);
+		return error;
+	}
+
+	atari_input_keyboard_interrupt_hook = atakbd_interrupt;
+
+	return 0;
+}
+
+static void __exit atakbd_exit(void)
+{
+	atari_input_keyboard_interrupt_hook = NULL;
+	input_unregister_device(atakbd_dev);
+}
+
+module_init(atakbd_init);
+module_exit(atakbd_exit);