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, 186 insertions, 0 deletions

diff --git a/include/trace/events/scmi.h b/include/trace/events/scmi.h
new file mode 100644
index 000000000..703b7bb68
--- /dev/null
+++ b/include/trace/events/scmi.h
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM scmi
+
+#if !defined(_TRACE_SCMI_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SCMI_H
+
+#include <linux/tracepoint.h>
+
+#define TRACE_SCMI_MAX_TAG_LEN	6
+
+TRACE_EVENT(scmi_fc_call,
+	TP_PROTO(u8 protocol_id, u8 msg_id, u32 res_id, u32 val1, u32 val2),
+	TP_ARGS(protocol_id, msg_id, res_id, val1, val2),
+
+	TP_STRUCT__entry(
+		__field(u8, protocol_id)
+		__field(u8, msg_id)
+		__field(u32, res_id)
+		__field(u32, val1)
+		__field(u32, val2)
+	),
+
+	TP_fast_assign(
+		__entry->protocol_id = protocol_id;
+		__entry->msg_id = msg_id;
+		__entry->res_id = res_id;
+		__entry->val1 = val1;
+		__entry->val2 = val2;
+	),
+
+	TP_printk("pt=%02X msg_id=%02X res_id:%u vals=%u:%u",
+		__entry->protocol_id, __entry->msg_id,
+		__entry->res_id, __entry->val1, __entry->val2)
+);
+
+TRACE_EVENT(scmi_xfer_begin,
+	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
+		 bool poll, int inflight),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, poll, inflight),
+
+	TP_STRUCT__entry(
+		__field(int, transfer_id)
+		__field(u8, msg_id)
+		__field(u8, protocol_id)
+		__field(u16, seq)
+		__field(bool, poll)
+		__field(int, inflight)
+	),
+
+	TP_fast_assign(
+		__entry->transfer_id = transfer_id;
+		__entry->msg_id = msg_id;
+		__entry->protocol_id = protocol_id;
+		__entry->seq = seq;
+		__entry->poll = poll;
+		__entry->inflight = inflight;
+	),
+
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X poll=%u inflight=%d",
+		  __entry->protocol_id, __entry->msg_id, __entry->seq,
+		  __entry->transfer_id, __entry->poll, __entry->inflight)
+);
+
+TRACE_EVENT(scmi_xfer_response_wait,
+	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
+		 u32 timeout, bool poll),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, timeout, poll),
+
+	TP_STRUCT__entry(
+		__field(int, transfer_id)
+		__field(u8, msg_id)
+		__field(u8, protocol_id)
+		__field(u16, seq)
+		__field(u32, timeout)
+		__field(bool, poll)
+	),
+
+	TP_fast_assign(
+		__entry->transfer_id = transfer_id;
+		__entry->msg_id = msg_id;
+		__entry->protocol_id = protocol_id;
+		__entry->seq = seq;
+		__entry->timeout = timeout;
+		__entry->poll = poll;
+	),
+
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X tmo_ms=%u poll=%u",
+		__entry->protocol_id, __entry->msg_id, __entry->seq,
+		__entry->transfer_id, __entry->timeout, __entry->poll)
+);
+
+TRACE_EVENT(scmi_xfer_end,
+	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
+		 int status, int inflight),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, status, inflight),
+
+	TP_STRUCT__entry(
+		__field(int, transfer_id)
+		__field(u8, msg_id)
+		__field(u8, protocol_id)
+		__field(u16, seq)
+		__field(int, status)
+		__field(int, inflight)
+	),
+
+	TP_fast_assign(
+		__entry->transfer_id = transfer_id;
+		__entry->msg_id = msg_id;
+		__entry->protocol_id = protocol_id;
+		__entry->seq = seq;
+		__entry->status = status;
+		__entry->inflight = inflight;
+	),
+
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X s=%d inflight=%d",
+		  __entry->protocol_id, __entry->msg_id, __entry->seq,
+		  __entry->transfer_id, __entry->status, __entry->inflight)
+);
+
+TRACE_EVENT(scmi_rx_done,
+	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
+		 u8 msg_type),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, msg_type),
+
+	TP_STRUCT__entry(
+		__field(int, transfer_id)
+		__field(u8, msg_id)
+		__field(u8, protocol_id)
+		__field(u16, seq)
+		__field(u8, msg_type)
+	),
+
+	TP_fast_assign(
+		__entry->transfer_id = transfer_id;
+		__entry->msg_id = msg_id;
+		__entry->protocol_id = protocol_id;
+		__entry->seq = seq;
+		__entry->msg_type = msg_type;
+	),
+
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X msg_type=%u",
+		__entry->protocol_id, __entry->msg_id, __entry->seq,
+		__entry->transfer_id, __entry->msg_type)
+);
+
+TRACE_EVENT(scmi_msg_dump,
+	TP_PROTO(int id, u8 channel_id, u8 protocol_id, u8 msg_id,
+		 unsigned char *tag, u16 seq, int status,
+		 void *buf, size_t len),
+	TP_ARGS(id, channel_id, protocol_id, msg_id, tag, seq, status,
+		buf, len),
+
+	TP_STRUCT__entry(
+		__field(int, id)
+		__field(u8, channel_id)
+		__field(u8, protocol_id)
+		__field(u8, msg_id)
+		__array(char, tag, TRACE_SCMI_MAX_TAG_LEN)
+		__field(u16, seq)
+		__field(int, status)
+		__field(size_t, len)
+		__dynamic_array(unsigned char, cmd, len)
+	),
+
+	TP_fast_assign(
+		__entry->id = id;
+		__entry->channel_id = channel_id;
+		__entry->protocol_id = protocol_id;
+		__entry->msg_id = msg_id;
+		strscpy(__entry->tag, tag, TRACE_SCMI_MAX_TAG_LEN);
+		__entry->seq = seq;
+		__entry->status = status;
+		__entry->len = len;
+		memcpy(__get_dynamic_array(cmd), buf, __entry->len);
+	),
+
+	TP_printk("id=%d ch=%02X pt=%02X t=%s msg_id=%02X seq=%04X s=%d pyld=%s",
+		  __entry->id, __entry->channel_id, __entry->protocol_id,
+		  __entry->tag, __entry->msg_id, __entry->seq, __entry->status,
+		__print_hex_str(__get_dynamic_array(cmd), __entry->len))
+);
+#endif /* _TRACE_SCMI_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>