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, 67 insertions, 0 deletions

diff --git a/sound/soc/sof/ipc3-priv.h b/sound/soc/sof/ipc3-priv.h
new file mode 100644
index 000000000..866c5f67b
--- /dev/null
+++ b/sound/soc/sof/ipc3-priv.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * Copyright(c) 2021 Intel Corporation
+ */
+
+#ifndef __SOUND_SOC_SOF_IPC3_PRIV_H
+#define __SOUND_SOC_SOF_IPC3_PRIV_H
+
+#include "sof-priv.h"
+
+/* IPC3 specific ops */
+extern const struct sof_ipc_pcm_ops ipc3_pcm_ops;
+extern const struct sof_ipc_tplg_ops ipc3_tplg_ops;
+extern const struct sof_ipc_tplg_control_ops tplg_ipc3_control_ops;
+extern const struct sof_ipc_fw_loader_ops ipc3_loader_ops;
+extern const struct sof_ipc_fw_tracing_ops ipc3_dtrace_ops;
+
+/* helpers for fw_ready and ext_manifest parsing */
+int sof_ipc3_get_ext_windows(struct snd_sof_dev *sdev,
+			     const struct sof_ipc_ext_data_hdr *ext_hdr);
+int sof_ipc3_get_cc_info(struct snd_sof_dev *sdev,
+			 const struct sof_ipc_ext_data_hdr *ext_hdr);
+int sof_ipc3_validate_fw_version(struct snd_sof_dev *sdev);
+
+/* dtrace position update */
+int ipc3_dtrace_posn_update(struct snd_sof_dev *sdev,
+			    struct sof_ipc_dma_trace_posn *posn);
+/* RX handler backend */
+void sof_ipc3_do_rx_work(struct snd_sof_dev *sdev, struct sof_ipc_cmd_hdr *hdr, void *msg_buf);
+
+/* dtrace platform callback wrappers */
+static inline int sof_dtrace_host_init(struct snd_sof_dev *sdev,
+				       struct snd_dma_buffer *dmatb,
+				       struct sof_ipc_dma_trace_params_ext *dtrace_params)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_init)
+		return dsp_ops->trace_init(sdev, dmatb, dtrace_params);
+
+	return 0;
+}
+
+static inline int sof_dtrace_host_release(struct snd_sof_dev *sdev)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_release)
+		return dsp_ops->trace_release(sdev);
+
+	return 0;
+}
+
+static inline int sof_dtrace_host_trigger(struct snd_sof_dev *sdev, int cmd)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_trigger)
+		return dsp_ops->trace_trigger(sdev, cmd);
+
+	return 0;
+}
+
+#endif