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, 79 insertions, 0 deletions

diff --git a/include/sound/hda_chmap.h b/include/sound/hda_chmap.h
new file mode 100644
index 000000000..e508f3192
--- /dev/null
+++ b/include/sound/hda_chmap.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * For multichannel support
+ */
+
+#ifndef __SOUND_HDA_CHMAP_H
+#define __SOUND_HDA_CHMAP_H
+
+#include <sound/pcm.h>
+#include <sound/hdaudio.h>
+
+
+#define SND_PRINT_CHANNEL_ALLOCATION_ADVISED_BUFSIZE 80
+
+struct hdac_cea_channel_speaker_allocation {
+	int ca_index;
+	int speakers[8];
+
+	/* derived values, just for convenience */
+	int channels;
+	int spk_mask;
+};
+struct hdac_chmap;
+
+struct hdac_chmap_ops {
+	/*
+	 * Helpers for producing the channel map TLVs. These can be overridden
+	 * for devices that have non-standard mapping requirements.
+	 */
+	int (*chmap_cea_alloc_validate_get_type)(struct hdac_chmap *chmap,
+		struct hdac_cea_channel_speaker_allocation *cap, int channels);
+	void (*cea_alloc_to_tlv_chmap)(struct hdac_chmap *hchmap,
+		struct hdac_cea_channel_speaker_allocation *cap,
+		unsigned int *chmap, int channels);
+
+	/* check that the user-given chmap is supported */
+	int (*chmap_validate)(struct hdac_chmap *hchmap, int ca,
+			int channels, unsigned char *chmap);
+
+	int (*get_spk_alloc)(struct hdac_device *hdac, int pcm_idx);
+
+	void (*get_chmap)(struct hdac_device *hdac, int pcm_idx,
+					unsigned char *chmap);
+	void (*set_chmap)(struct hdac_device *hdac, int pcm_idx,
+			unsigned char *chmap, int prepared);
+	bool (*is_pcm_attached)(struct hdac_device *hdac, int pcm_idx);
+
+	/* get and set channel assigned to each HDMI ASP (audio sample packet) slot */
+	int (*pin_get_slot_channel)(struct hdac_device *codec,
+			hda_nid_t pin_nid, int asp_slot);
+	int (*pin_set_slot_channel)(struct hdac_device *codec,
+			hda_nid_t pin_nid, int asp_slot, int channel);
+	void (*set_channel_count)(struct hdac_device *codec,
+				hda_nid_t cvt_nid, int chs);
+};
+
+struct hdac_chmap {
+	unsigned int channels_max; /* max over all cvts */
+	struct hdac_chmap_ops ops;
+	struct hdac_device *hdac;
+};
+
+void snd_hdac_register_chmap_ops(struct hdac_device *hdac,
+				struct hdac_chmap *chmap);
+int snd_hdac_channel_allocation(struct hdac_device *hdac, int spk_alloc,
+			int channels, bool chmap_set,
+			bool non_pcm, unsigned char *map);
+int snd_hdac_get_active_channels(int ca);
+void snd_hdac_setup_channel_mapping(struct hdac_chmap *chmap,
+		       hda_nid_t pin_nid, bool non_pcm, int ca,
+		       int channels, unsigned char *map,
+		       bool chmap_set);
+void snd_hdac_print_channel_allocation(int spk_alloc, char *buf, int buflen);
+struct hdac_cea_channel_speaker_allocation *snd_hdac_get_ch_alloc_from_ca(int ca);
+int snd_hdac_chmap_to_spk_mask(unsigned char c);
+int snd_hdac_spk_to_chmap(int spk);
+int snd_hdac_add_chmap_ctls(struct snd_pcm *pcm, int pcm_idx,
+				struct hdac_chmap *chmap);
+#endif /* __SOUND_HDA_CHMAP_H */