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, 206 insertions, 0 deletions

diff --git a/drivers/input/misc/yealink.h b/drivers/input/misc/yealink.h
new file mode 100644
index 000000000..69f700431
--- /dev/null
+++ b/drivers/input/misc/yealink.h
@@ -0,0 +1,206 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * drivers/usb/input/yealink.h
+ *
+ * Copyright (c) 2005 Henk Vergonet <Henk.Vergonet@gmail.com>
+ */
+#ifndef INPUT_YEALINK_H
+#define INPUT_YEALINK_H
+
+/* Using the control channel on interface 3 various aspects of the phone
+ * can be controlled like LCD, LED, dialtone and the ringtone.
+ */
+
+struct yld_ctl_packet {
+	u8	cmd;		/* command code, see below */
+	u8	size;		/* 1-11, size of used data bytes. */
+	__be16	offset;		/* internal packet offset */
+	u8	data[11];
+	s8	sum;		/* negative sum of 15 preceding bytes */
+} __attribute__ ((packed));
+
+#define USB_PKT_LEN	sizeof(struct yld_ctl_packet)
+
+/* The following yld_ctl_packet's are available: */
+
+/* Init registers
+ *
+ * cmd		0x8e
+ * size		10
+ * offset	0
+ * data		0,0,0,0....
+ */
+#define CMD_INIT		0x8e
+
+/* Request key scan
+ *
+ * cmd		0x80
+ * size		1
+ * offset	0
+ * data[0]	on return returns the key number, if it changes there's a new
+ * 		key pressed.
+ */
+#define CMD_KEYPRESS		0x80
+
+/* Request scancode
+ *
+ * cmd		0x81
+ * size		1
+ * offset	key number [0-1f]
+ * data[0]	on return returns the scancode
+ */
+#define CMD_SCANCODE		0x81
+
+/* Set LCD
+ *
+ * cmd		0x04
+ * size		1-11
+ * offset	0-23
+ * data		segment bits
+ */
+#define CMD_LCD			0x04
+
+/* Set led
+ *
+ * cmd		0x05
+ * size		1
+ * offset	0
+ * data[0]	0 OFF / 1 ON
+ */
+#define CMD_LED			0x05
+
+/* Set ringtone volume
+ *
+ * cmd		0x11
+ * size		1
+ * offset	0
+ * data[0]	0-0xff  volume
+ */
+#define CMD_RING_VOLUME		0x11
+
+/* Set ringtone notes
+ *
+ * cmd		0x02
+ * size		1-11
+ * offset	0->
+ * data		binary representation LE16(-freq), LE16(duration) ....
+ */
+#define CMD_RING_NOTE		0x02
+
+/* Sound ringtone via the speaker on the back
+ *
+ * cmd		0x03
+ * size		1
+ * offset	0
+ * data[0]	0 OFF / 0x24 ON
+ */
+#define CMD_RINGTONE		0x03
+
+/* Sound dial tone via the ear speaker
+ *
+ * cmd		0x09
+ * size		1
+ * offset	0
+ * data[0]	0 OFF / 1 ON
+ */
+#define CMD_DIALTONE		0x09
+
+#endif /* INPUT_YEALINK_H */
+
+
+#if defined(_SEG) && defined(_PIC)
+/* This table maps the LCD segments onto individual bit positions in the
+ * yld_status struct.
+ */
+
+/* LCD, each segment must be driven separately.
+ *
+ * Layout:
+ *
+ *   |[]   [][]   [][]   [][]   in   |[][]
+ *   |[] M [][] D [][] : [][]   out  |[][]
+ *                             store
+ *
+ *    NEW REP         SU MO TU WE TH FR SA
+ *
+ *    [] [] [] [] [] [] [] [] [] [] [] []
+ *    [] [] [] [] [] [] [] [] [] [] [] []
+ */
+
+/* Line 1
+ *	Format		: 18.e8.M8.88...188
+ *	Icon names	: M D : IN OUT STORE
+ */
+#define LCD_LINE1_OFFSET	0
+#define LCD_LINE1_SIZE		17
+
+/* Note: first g then f =>			       !      !      */
+/* _SEG(    type    a      b      c      d      e      g      f   )  */
+	_SEG('1',  0,0 , 22,2 , 22,2 ,  0,0 ,  0,0 ,  0,0 ,  0,0	),
+	_SEG('8', 20,1 , 20,2 , 20,4 , 20,8 , 21,4 , 21,2 , 21,1	),
+	_PIC('.', 22,1 , "M"						),
+	_SEG('e', 18,1 , 18,2 , 18,4 , 18,1 , 19,2 , 18,1 , 19,1	),
+	_SEG('8', 16,1 , 16,2 , 16,4 , 16,8 , 17,4 , 17,2 , 17,1	),
+	_PIC('.', 15,8 , "D"						),
+	_SEG('M', 14,1 , 14,2 , 14,4 , 14,1 , 15,4 , 15,2 , 15,1	),
+	_SEG('8', 12,1 , 12,2 , 12,4 , 12,8 , 13,4 , 13,2 , 13,1	),
+	_PIC('.', 11,8 , ":"						),
+	_SEG('8', 10,1 , 10,2 , 10,4 , 10,8 , 11,4 , 11,2 , 11,1	),
+	_SEG('8',  8,1 ,  8,2 ,  8,4 ,  8,8 ,  9,4 ,  9,2 ,  9,1	),
+	_PIC('.',  7,1 , "IN"						),
+	_PIC('.',  7,2 , "OUT"						),
+	_PIC('.',  7,4 , "STORE"					),
+	_SEG('1',  0,0 ,  5,1 ,  5,1 ,  0,0 ,  0,0 ,  0,0 ,  0,0	),
+	_SEG('8',  4,1 ,  4,2 ,  4,4 ,  4,8 ,  5,8 ,  5,4 ,  5,2	),
+	_SEG('8',  2,1 ,  2,2 ,  2,4 ,  2,8 ,  3,4 ,  3,2 ,  3,1	),
+
+/* Line 2
+ *	Format		: .........
+ *	Pict. name	: NEW REP SU MO TU WE TH FR SA
+ */
+#define LCD_LINE2_OFFSET	LCD_LINE1_OFFSET + LCD_LINE1_SIZE
+#define LCD_LINE2_SIZE		9
+
+	_PIC('.', 23,2 , "NEW"	),
+	_PIC('.', 23,4 , "REP"	),
+	_PIC('.',  1,8 , "SU"	),
+	_PIC('.',  1,4 , "MO"	),
+	_PIC('.',  1,2 , "TU"	),
+	_PIC('.',  1,1 , "WE"	),
+	_PIC('.',  0,1 , "TH"	),
+	_PIC('.',  0,2 , "FR"	),
+	_PIC('.',  0,4 , "SA"	),
+
+/* Line 3
+ *	Format		: 888888888888
+ */
+#define LCD_LINE3_OFFSET	LCD_LINE2_OFFSET + LCD_LINE2_SIZE
+#define LCD_LINE3_SIZE		12
+
+	_SEG('8', 22,16, 22,32, 22,64, 22,128, 23,128, 23,64, 23,32  ),
+	_SEG('8', 20,16, 20,32, 20,64, 20,128, 21,128, 21,64, 21,32  ),
+	_SEG('8', 18,16, 18,32, 18,64, 18,128, 19,128, 19,64, 19,32  ),
+	_SEG('8', 16,16, 16,32, 16,64, 16,128, 17,128, 17,64, 17,32  ),
+	_SEG('8', 14,16, 14,32, 14,64, 14,128, 15,128, 15,64, 15,32  ),
+	_SEG('8', 12,16, 12,32, 12,64, 12,128, 13,128, 13,64, 13,32  ),
+	_SEG('8', 10,16, 10,32, 10,64, 10,128, 11,128, 11,64, 11,32  ),
+	_SEG('8',  8,16,  8,32,  8,64,  8,128,  9,128,  9,64,  9,32  ),
+	_SEG('8',  6,16,  6,32,  6,64,  6,128,  7,128,  7,64,  7,32  ),
+	_SEG('8',  4,16,  4,32,  4,64,  4,128,  5,128,  5,64,  5,32  ),
+	_SEG('8',  2,16,  2,32,  2,64,  2,128,  3,128,  3,64,  3,32  ),
+	_SEG('8',  0,16,  0,32,  0,64,  0,128,  1,128,  1,64,  1,32  ),
+
+/* Line 4
+ *
+ * The LED, DIALTONE and RINGTONE are implemented as icons and use the same
+ * sysfs interface.
+ */
+#define LCD_LINE4_OFFSET	LCD_LINE3_OFFSET + LCD_LINE3_SIZE
+
+	_PIC('.', offsetof(struct yld_status, led)	, 0x01, "LED" ),
+	_PIC('.', offsetof(struct yld_status, dialtone) , 0x01, "DIALTONE" ),
+	_PIC('.', offsetof(struct yld_status, ringtone) , 0x24, "RINGTONE" ),
+
+#undef _SEG
+#undef _PIC
+#endif /* _SEG && _PIC */