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, 116 insertions, 0 deletions

diff --git a/include/sound/jack.h b/include/sound/jack.h
new file mode 100644
index 000000000..715b95983
--- /dev/null
+++ b/include/sound/jack.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_JACK_H
+#define __SOUND_JACK_H
+
+/*
+ *  Jack abstraction layer
+ *
+ *  Copyright 2008 Wolfson Microelectronics plc
+ */
+
+#include <sound/core.h>
+
+struct input_dev;
+
+/**
+ * enum snd_jack_types - Jack types which can be reported
+ * @SND_JACK_HEADPHONE: Headphone
+ * @SND_JACK_MICROPHONE: Microphone
+ * @SND_JACK_HEADSET: Headset
+ * @SND_JACK_LINEOUT: Line out
+ * @SND_JACK_MECHANICAL: Mechanical switch
+ * @SND_JACK_VIDEOOUT: Video out
+ * @SND_JACK_AVOUT: AV (Audio Video) out
+ * @SND_JACK_LINEIN:  Line in
+ * @SND_JACK_USB: USB audio device
+ * @SND_JACK_BTN_0: Button 0
+ * @SND_JACK_BTN_1: Button 1
+ * @SND_JACK_BTN_2: Button 2
+ * @SND_JACK_BTN_3: Button 3
+ * @SND_JACK_BTN_4: Button 4
+ * @SND_JACK_BTN_5: Button 5
+ *
+ * These values are used as a bitmask.
+ *
+ * Note that this must be kept in sync with the lookup table in
+ * sound/core/jack.c.
+ */
+enum snd_jack_types {
+	SND_JACK_HEADPHONE	= 0x0001,
+	SND_JACK_MICROPHONE	= 0x0002,
+	SND_JACK_HEADSET	= SND_JACK_HEADPHONE | SND_JACK_MICROPHONE,
+	SND_JACK_LINEOUT	= 0x0004,
+	SND_JACK_MECHANICAL	= 0x0008, /* If detected separately */
+	SND_JACK_VIDEOOUT	= 0x0010,
+	SND_JACK_AVOUT		= SND_JACK_LINEOUT | SND_JACK_VIDEOOUT,
+	SND_JACK_LINEIN		= 0x0020,
+	SND_JACK_USB		= 0x0040,
+
+	/* Kept separate from switches to facilitate implementation */
+	SND_JACK_BTN_0		= 0x4000,
+	SND_JACK_BTN_1		= 0x2000,
+	SND_JACK_BTN_2		= 0x1000,
+	SND_JACK_BTN_3		= 0x0800,
+	SND_JACK_BTN_4		= 0x0400,
+	SND_JACK_BTN_5		= 0x0200,
+};
+
+/* Keep in sync with definitions above */
+#define SND_JACK_SWITCH_TYPES 7
+
+struct snd_jack {
+	struct list_head kctl_list;
+	struct snd_card *card;
+	const char *id;
+#ifdef CONFIG_SND_JACK_INPUT_DEV
+	struct input_dev *input_dev;
+	struct mutex input_dev_lock;
+	int registered;
+	int type;
+	char name[100];
+	unsigned int key[6];   /* Keep in sync with definitions above */
+#endif /* CONFIG_SND_JACK_INPUT_DEV */
+	int hw_status_cache;
+	void *private_data;
+	void (*private_free)(struct snd_jack *);
+};
+
+#ifdef CONFIG_SND_JACK
+
+int snd_jack_new(struct snd_card *card, const char *id, int type,
+		 struct snd_jack **jack, bool initial_kctl, bool phantom_jack);
+int snd_jack_add_new_kctl(struct snd_jack *jack, const char * name, int mask);
+#ifdef CONFIG_SND_JACK_INPUT_DEV
+int snd_jack_set_key(struct snd_jack *jack, enum snd_jack_types type,
+		     int keytype);
+#endif
+void snd_jack_report(struct snd_jack *jack, int status);
+
+#else
+static inline int snd_jack_new(struct snd_card *card, const char *id, int type,
+			       struct snd_jack **jack, bool initial_kctl, bool phantom_jack)
+{
+	return 0;
+}
+
+static inline int snd_jack_add_new_kctl(struct snd_jack *jack, const char * name, int mask)
+{
+	return 0;
+}
+
+static inline void snd_jack_report(struct snd_jack *jack, int status)
+{
+}
+
+#endif
+
+#if !defined(CONFIG_SND_JACK) || !defined(CONFIG_SND_JACK_INPUT_DEV)
+static inline int snd_jack_set_key(struct snd_jack *jack,
+				   enum snd_jack_types type,
+				   int keytype)
+{
+	return 0;
+}
+#endif /* !CONFIG_SND_JACK || !CONFIG_SND_JACK_INPUT_DEV */
+
+#endif