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, 170 insertions, 0 deletions

diff --git a/sound/firewire/fireface/ff.h b/sound/firewire/fireface/ff.h
new file mode 100644
index 000000000..c9c35c67d
--- /dev/null
+++ b/sound/firewire/fireface/ff.h
@@ -0,0 +1,170 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * ff.h - a part of driver for RME Fireface series
+ *
+ * Copyright (c) 2015-2017 Takashi Sakamoto
+ */
+
+#ifndef SOUND_FIREFACE_H_INCLUDED
+#define SOUND_FIREFACE_H_INCLUDED
+
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/firewire-constants.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/sched/signal.h>
+
+#include <sound/core.h>
+#include <sound/info.h>
+#include <sound/rawmidi.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/hwdep.h>
+#include <sound/firewire.h>
+
+#include "../lib.h"
+#include "../amdtp-stream.h"
+#include "../iso-resources.h"
+
+#define SND_FF_MAXIMIM_MIDI_QUADS	9
+#define SND_FF_IN_MIDI_PORTS		2
+#define SND_FF_OUT_MIDI_PORTS		2
+
+enum snd_ff_unit_version {
+	SND_FF_UNIT_VERSION_FF800	= 0x000001,
+	SND_FF_UNIT_VERSION_FF400	= 0x000002,
+	SND_FF_UNIT_VERSION_UFX		= 0x000003,
+	SND_FF_UNIT_VERSION_UCX		= 0x000004,
+	SND_FF_UNIT_VERSION_802		= 0x000005,
+};
+
+enum snd_ff_stream_mode {
+	SND_FF_STREAM_MODE_LOW = 0,
+	SND_FF_STREAM_MODE_MID,
+	SND_FF_STREAM_MODE_HIGH,
+	SND_FF_STREAM_MODE_COUNT,
+};
+
+struct snd_ff_protocol;
+struct snd_ff_spec {
+	const unsigned int pcm_capture_channels[SND_FF_STREAM_MODE_COUNT];
+	const unsigned int pcm_playback_channels[SND_FF_STREAM_MODE_COUNT];
+
+	unsigned int midi_in_ports;
+	unsigned int midi_out_ports;
+
+	const struct snd_ff_protocol *protocol;
+	u64 midi_high_addr;
+	u8 midi_addr_range;
+	u64 midi_rx_addrs[SND_FF_OUT_MIDI_PORTS];
+};
+
+struct snd_ff {
+	struct snd_card *card;
+	struct fw_unit *unit;
+	struct mutex mutex;
+	spinlock_t lock;
+
+	enum snd_ff_unit_version unit_version;
+	const struct snd_ff_spec *spec;
+
+	/* To handle MIDI tx. */
+	struct snd_rawmidi_substream *tx_midi_substreams[SND_FF_IN_MIDI_PORTS];
+	struct fw_address_handler async_handler;
+
+	/* TO handle MIDI rx. */
+	struct snd_rawmidi_substream *rx_midi_substreams[SND_FF_OUT_MIDI_PORTS];
+	bool on_sysex[SND_FF_OUT_MIDI_PORTS];
+	__le32 msg_buf[SND_FF_OUT_MIDI_PORTS][SND_FF_MAXIMIM_MIDI_QUADS];
+	struct work_struct rx_midi_work[SND_FF_OUT_MIDI_PORTS];
+	struct fw_transaction transactions[SND_FF_OUT_MIDI_PORTS];
+	ktime_t next_ktime[SND_FF_OUT_MIDI_PORTS];
+	bool rx_midi_error[SND_FF_OUT_MIDI_PORTS];
+	unsigned int rx_bytes[SND_FF_OUT_MIDI_PORTS];
+
+	unsigned int substreams_counter;
+	struct amdtp_stream tx_stream;
+	struct amdtp_stream rx_stream;
+	struct fw_iso_resources tx_resources;
+	struct fw_iso_resources rx_resources;
+
+	int dev_lock_count;
+	bool dev_lock_changed;
+	wait_queue_head_t hwdep_wait;
+
+	struct amdtp_domain domain;
+
+	void *msg_parser;
+};
+
+enum snd_ff_clock_src {
+	SND_FF_CLOCK_SRC_INTERNAL,
+	SND_FF_CLOCK_SRC_SPDIF,
+	SND_FF_CLOCK_SRC_ADAT1,
+	SND_FF_CLOCK_SRC_ADAT2,
+	SND_FF_CLOCK_SRC_WORD,
+	SND_FF_CLOCK_SRC_LTC,
+	/* TODO: perhaps TCO exists. */
+};
+
+struct snd_ff_protocol {
+	size_t msg_parser_size;
+	bool (*has_msg)(struct snd_ff *ff);
+	long (*copy_msg_to_user)(struct snd_ff *ff, char __user *buf, long count);
+	void (*handle_msg)(struct snd_ff *ff, unsigned int offset, const __le32 *buf,
+			   size_t length, u32 tstamp);
+	int (*fill_midi_msg)(struct snd_ff *ff,
+			     struct snd_rawmidi_substream *substream,
+			     unsigned int port);
+	int (*get_clock)(struct snd_ff *ff, unsigned int *rate,
+			 enum snd_ff_clock_src *src);
+	int (*switch_fetching_mode)(struct snd_ff *ff, bool enable);
+	int (*allocate_resources)(struct snd_ff *ff, unsigned int rate);
+	int (*begin_session)(struct snd_ff *ff, unsigned int rate);
+	void (*finish_session)(struct snd_ff *ff);
+	void (*dump_status)(struct snd_ff *ff, struct snd_info_buffer *buffer);
+};
+
+extern const struct snd_ff_protocol snd_ff_protocol_ff800;
+extern const struct snd_ff_protocol snd_ff_protocol_ff400;
+extern const struct snd_ff_protocol snd_ff_protocol_latter;
+
+int snd_ff_transaction_register(struct snd_ff *ff);
+int snd_ff_transaction_reregister(struct snd_ff *ff);
+void snd_ff_transaction_unregister(struct snd_ff *ff);
+
+int amdtp_ff_set_parameters(struct amdtp_stream *s, unsigned int rate,
+			    unsigned int pcm_channels);
+int amdtp_ff_add_pcm_hw_constraints(struct amdtp_stream *s,
+				    struct snd_pcm_runtime *runtime);
+int amdtp_ff_init(struct amdtp_stream *s, struct fw_unit *unit,
+		  enum amdtp_stream_direction dir);
+
+int snd_ff_stream_get_multiplier_mode(enum cip_sfc sfc,
+				      enum snd_ff_stream_mode *mode);
+int snd_ff_stream_init_duplex(struct snd_ff *ff);
+void snd_ff_stream_destroy_duplex(struct snd_ff *ff);
+int snd_ff_stream_reserve_duplex(struct snd_ff *ff, unsigned int rate,
+				 unsigned int frames_per_period,
+				 unsigned int frames_per_buffer);
+int snd_ff_stream_start_duplex(struct snd_ff *ff, unsigned int rate);
+void snd_ff_stream_stop_duplex(struct snd_ff *ff);
+void snd_ff_stream_update_duplex(struct snd_ff *ff);
+
+void snd_ff_stream_lock_changed(struct snd_ff *ff);
+int snd_ff_stream_lock_try(struct snd_ff *ff);
+void snd_ff_stream_lock_release(struct snd_ff *ff);
+
+void snd_ff_proc_init(struct snd_ff *ff);
+const char *snd_ff_proc_get_clk_label(enum snd_ff_clock_src src);
+
+int snd_ff_create_midi_devices(struct snd_ff *ff);
+
+int snd_ff_create_pcm_devices(struct snd_ff *ff);
+
+int snd_ff_create_hwdep_devices(struct snd_ff *ff);
+
+#endif