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, 121 insertions, 0 deletions

diff --git a/include/trace/events/sof.h b/include/trace/events/sof.h
new file mode 100644
index 000000000..3061423c0
--- /dev/null
+++ b/include/trace/events/sof.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright(c) 2022 Intel Corporation
+ *
+ * Author: Noah Klayman <noah.klayman@intel.com>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM sof
+
+#if !defined(_TRACE_SOF_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SOF_H
+#include <linux/tracepoint.h>
+#include <linux/types.h>
+#include <sound/sof/stream.h>
+#include "../../../sound/soc/sof/sof-audio.h"
+
+DECLARE_EVENT_CLASS(sof_widget_template,
+	TP_PROTO(struct snd_sof_widget *swidget),
+	TP_ARGS(swidget),
+	TP_STRUCT__entry(
+		__string(name, swidget->widget->name)
+		__field(int, use_count)
+	),
+	TP_fast_assign(
+		__assign_str(name);
+		__entry->use_count = swidget->use_count;
+	),
+	TP_printk("name=%s use_count=%d", __get_str(name), __entry->use_count)
+);
+
+DEFINE_EVENT(sof_widget_template, sof_widget_setup,
+	TP_PROTO(struct snd_sof_widget *swidget),
+	TP_ARGS(swidget)
+);
+
+DEFINE_EVENT(sof_widget_template, sof_widget_free,
+	TP_PROTO(struct snd_sof_widget *swidget),
+	TP_ARGS(swidget)
+);
+
+TRACE_EVENT(sof_ipc3_period_elapsed_position,
+	TP_PROTO(struct snd_sof_dev *sdev, struct sof_ipc_stream_posn *posn),
+	TP_ARGS(sdev, posn),
+	TP_STRUCT__entry(
+		__string(device_name, dev_name(sdev->dev))
+		__field(u64, host_posn)
+		__field(u64, dai_posn)
+		__field(u64, wallclock)
+	),
+	TP_fast_assign(
+		__assign_str(device_name);
+		__entry->host_posn = posn->host_posn;
+		__entry->dai_posn = posn->dai_posn;
+		__entry->wallclock = posn->wallclock;
+	),
+	TP_printk("device_name=%s host_posn=%#llx dai_posn=%#llx wallclock=%#llx",
+		  __get_str(device_name), __entry->host_posn, __entry->dai_posn,
+		  __entry->wallclock)
+);
+
+TRACE_EVENT(sof_pcm_pointer_position,
+	TP_PROTO(struct snd_sof_dev *sdev,
+		struct snd_sof_pcm *spcm,
+		struct snd_pcm_substream *substream,
+		snd_pcm_uframes_t dma_posn,
+		snd_pcm_uframes_t dai_posn
+	),
+	TP_ARGS(sdev, spcm, substream, dma_posn, dai_posn),
+	TP_STRUCT__entry(
+		__string(device_name, dev_name(sdev->dev))
+		__field(u32, pcm_id)
+		__field(int, stream)
+		__field(unsigned long, dma_posn)
+		__field(unsigned long, dai_posn)
+	),
+	TP_fast_assign(
+		__assign_str(device_name);
+		__entry->pcm_id = le32_to_cpu(spcm->pcm.pcm_id);
+		__entry->stream = substream->stream;
+		__entry->dma_posn = dma_posn;
+		__entry->dai_posn = dai_posn;
+	),
+	TP_printk("device_name=%s pcm_id=%d stream=%d dma_posn=%lu dai_posn=%lu",
+		  __get_str(device_name), __entry->pcm_id, __entry->stream,
+		  __entry->dma_posn, __entry->dai_posn)
+);
+
+TRACE_EVENT(sof_stream_position_ipc_rx,
+	TP_PROTO(struct device *dev),
+	TP_ARGS(dev),
+	TP_STRUCT__entry(
+		__string(device_name, dev_name(dev))
+	),
+	TP_fast_assign(
+		__assign_str(device_name);
+	),
+	TP_printk("device_name=%s", __get_str(device_name))
+);
+
+TRACE_EVENT(sof_ipc4_fw_config,
+	TP_PROTO(struct snd_sof_dev *sdev, char *key, u32 value),
+	TP_ARGS(sdev, key, value),
+	TP_STRUCT__entry(
+		__string(device_name, dev_name(sdev->dev))
+		__string(key, key)
+		__field(u32, value)
+	),
+	TP_fast_assign(
+		__assign_str(device_name);
+		__assign_str(key);
+		__entry->value = value;
+	),
+	TP_printk("device_name=%s key=%s value=%d",
+		  __get_str(device_name), __get_str(key), __entry->value)
+);
+
+#endif /* _TRACE_SOF_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>