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, 156 insertions, 0 deletions

diff --git a/include/trace/events/intel-sst.h b/include/trace/events/intel-sst.h
new file mode 100644
index 000000000..0416e91f8
--- /dev/null
+++ b/include/trace/events/intel-sst.h
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM intel-sst
+
+/*
+ * The TRACE_SYSTEM_VAR defaults to TRACE_SYSTEM, but must be a
+ * legitimate C variable. It is not exported to user space.
+ */
+#undef TRACE_SYSTEM_VAR
+#define TRACE_SYSTEM_VAR intel_sst
+
+#if !defined(_TRACE_INTEL_SST_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_INTEL_SST_H
+
+#include <linux/types.h>
+#include <linux/ktime.h>
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(sst_ipc_msg,
+
+	TP_PROTO(unsigned int val),
+
+	TP_ARGS(val),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	val		)
+	),
+
+	TP_fast_assign(
+		__entry->val = val;
+	),
+
+	TP_printk("0x%8.8x", (unsigned int)__entry->val)
+);
+
+DEFINE_EVENT(sst_ipc_msg, sst_ipc_msg_tx,
+
+	TP_PROTO(unsigned int val),
+
+	TP_ARGS(val)
+
+);
+
+DEFINE_EVENT(sst_ipc_msg, sst_ipc_msg_rx,
+
+	TP_PROTO(unsigned int val),
+
+	TP_ARGS(val)
+
+);
+
+DECLARE_EVENT_CLASS(sst_ipc_mailbox,
+
+	TP_PROTO(unsigned int offset, unsigned int val),
+
+	TP_ARGS(offset, val),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	offset		)
+		__field(	unsigned int,	val		)
+	),
+
+	TP_fast_assign(
+		__entry->offset = offset;
+		__entry->val = val;
+	),
+
+	TP_printk(" 0x%4.4x = 0x%8.8x",
+		(unsigned int)__entry->offset, (unsigned int)__entry->val)
+);
+
+DEFINE_EVENT(sst_ipc_mailbox, sst_ipc_inbox_rdata,
+
+	TP_PROTO(unsigned int offset, unsigned int val),
+
+	TP_ARGS(offset, val)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox, sst_ipc_inbox_wdata,
+
+	TP_PROTO(unsigned int offset, unsigned int val),
+
+	TP_ARGS(offset, val)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox, sst_ipc_outbox_rdata,
+
+	TP_PROTO(unsigned int offset, unsigned int val),
+
+	TP_ARGS(offset, val)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox, sst_ipc_outbox_wdata,
+
+	TP_PROTO(unsigned int offset, unsigned int val),
+
+	TP_ARGS(offset, val)
+
+);
+
+DECLARE_EVENT_CLASS(sst_ipc_mailbox_info,
+
+	TP_PROTO(unsigned int size),
+
+	TP_ARGS(size),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	size		)
+	),
+
+	TP_fast_assign(
+		__entry->size = size;
+	),
+
+	TP_printk("Mailbox bytes 0x%8.8x", (unsigned int)__entry->size)
+);
+
+DEFINE_EVENT(sst_ipc_mailbox_info, sst_ipc_inbox_read,
+
+	TP_PROTO(unsigned int size),
+
+	TP_ARGS(size)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox_info, sst_ipc_inbox_write,
+
+	TP_PROTO(unsigned int size),
+
+	TP_ARGS(size)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox_info, sst_ipc_outbox_read,
+
+	TP_PROTO(unsigned int size),
+
+	TP_ARGS(size)
+
+);
+
+DEFINE_EVENT(sst_ipc_mailbox_info, sst_ipc_outbox_write,
+
+	TP_PROTO(unsigned int size),
+
+	TP_ARGS(size)
+
+);
+
+#endif /* _TRACE_SST_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>