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, 264 insertions, 0 deletions

diff --git a/include/trace/events/mptcp.h b/include/trace/events/mptcp.h
new file mode 100644
index 000000000..04521acba
--- /dev/null
+++ b/include/trace/events/mptcp.h
@@ -0,0 +1,264 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mptcp
+
+#if !defined(_TRACE_MPTCP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MPTCP_H
+
+#include <linux/ipv6.h>
+#include <linux/tcp.h>
+#include <linux/tracepoint.h>
+#include <net/ipv6.h>
+#include <net/tcp.h>
+#include <linux/sock_diag.h>
+#include <net/rstreason.h>
+
+#define show_mapping_status(status)					\
+	__print_symbolic(status,					\
+		{ 0, "MAPPING_OK" },					\
+		{ 1, "MAPPING_INVALID" },				\
+		{ 2, "MAPPING_EMPTY" },					\
+		{ 3, "MAPPING_DATA_FIN" },				\
+		{ 4, "MAPPING_DUMMY" })
+
+TRACE_EVENT(mptcp_subflow_get_send,
+
+	TP_PROTO(struct mptcp_subflow_context *subflow),
+
+	TP_ARGS(subflow),
+
+	TP_STRUCT__entry(
+		__field(bool, active)
+		__field(bool, free)
+		__field(u32, snd_wnd)
+		__field(u32, pace)
+		__field(u8, backup)
+		__field(u64, ratio)
+	),
+
+	TP_fast_assign(
+		struct sock *ssk;
+
+		__entry->active = mptcp_subflow_active(subflow);
+		__entry->backup = subflow->backup || subflow->request_bkup;
+
+		if (subflow->tcp_sock && sk_fullsock(subflow->tcp_sock))
+			__entry->free = sk_stream_memory_free(subflow->tcp_sock);
+		else
+			__entry->free = 0;
+
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		if (ssk && sk_fullsock(ssk)) {
+			__entry->snd_wnd = tcp_sk(ssk)->snd_wnd;
+			__entry->pace = READ_ONCE(ssk->sk_pacing_rate);
+		} else {
+			__entry->snd_wnd = 0;
+			__entry->pace = 0;
+		}
+
+		if (ssk && sk_fullsock(ssk) && __entry->pace)
+			__entry->ratio = div_u64((u64)ssk->sk_wmem_queued << 32, __entry->pace);
+		else
+			__entry->ratio = 0;
+	),
+
+	TP_printk("active=%d free=%d snd_wnd=%u pace=%u backup=%u ratio=%llu",
+		  __entry->active, __entry->free,
+		  __entry->snd_wnd, __entry->pace,
+		  __entry->backup, __entry->ratio)
+);
+
+DECLARE_EVENT_CLASS(mptcp_dump_mpext,
+
+	TP_PROTO(struct mptcp_ext *mpext),
+
+	TP_ARGS(mpext),
+
+	TP_STRUCT__entry(
+		__field(u64, data_ack)
+		__field(u64, data_seq)
+		__field(u32, subflow_seq)
+		__field(u16, data_len)
+		__field(u16, csum)
+		__field(u8, use_map)
+		__field(u8, dsn64)
+		__field(u8, data_fin)
+		__field(u8, use_ack)
+		__field(u8, ack64)
+		__field(u8, mpc_map)
+		__field(u8, frozen)
+		__field(u8, reset_transient)
+		__field(u8, reset_reason)
+		__field(u8, csum_reqd)
+		__field(u8, infinite_map)
+	),
+
+	TP_fast_assign(
+		__entry->data_ack = mpext->ack64 ? mpext->data_ack : mpext->data_ack32;
+		__entry->data_seq = mpext->data_seq;
+		__entry->subflow_seq = mpext->subflow_seq;
+		__entry->data_len = mpext->data_len;
+		__entry->csum = (__force u16)mpext->csum;
+		__entry->use_map = mpext->use_map;
+		__entry->dsn64 = mpext->dsn64;
+		__entry->data_fin = mpext->data_fin;
+		__entry->use_ack = mpext->use_ack;
+		__entry->ack64 = mpext->ack64;
+		__entry->mpc_map = mpext->mpc_map;
+		__entry->frozen = mpext->frozen;
+		__entry->reset_transient = mpext->reset_transient;
+		__entry->reset_reason = mpext->reset_reason;
+		__entry->csum_reqd = mpext->csum_reqd;
+		__entry->infinite_map = mpext->infinite_map;
+	),
+
+	TP_printk("data_ack=%llu data_seq=%llu subflow_seq=%u data_len=%u csum=%x use_map=%u dsn64=%u data_fin=%u use_ack=%u ack64=%u mpc_map=%u frozen=%u reset_transient=%u reset_reason=%u csum_reqd=%u infinite_map=%u",
+		  __entry->data_ack, __entry->data_seq,
+		  __entry->subflow_seq, __entry->data_len,
+		  __entry->csum, __entry->use_map,
+		  __entry->dsn64, __entry->data_fin,
+		  __entry->use_ack, __entry->ack64,
+		  __entry->mpc_map, __entry->frozen,
+		  __entry->reset_transient, __entry->reset_reason,
+		  __entry->csum_reqd, __entry->infinite_map)
+);
+
+DEFINE_EVENT(mptcp_dump_mpext, mptcp_sendmsg_frag,
+	TP_PROTO(struct mptcp_ext *mpext),
+	TP_ARGS(mpext));
+
+DEFINE_EVENT(mptcp_dump_mpext, get_mapping_status,
+	TP_PROTO(struct mptcp_ext *mpext),
+	TP_ARGS(mpext));
+
+TRACE_EVENT(ack_update_msk,
+
+	TP_PROTO(u64 data_ack, u64 old_snd_una,
+		 u64 new_snd_una, u64 new_wnd_end,
+		 u64 msk_wnd_end),
+
+	TP_ARGS(data_ack, old_snd_una,
+		new_snd_una, new_wnd_end,
+		msk_wnd_end),
+
+	TP_STRUCT__entry(
+		__field(u64, data_ack)
+		__field(u64, old_snd_una)
+		__field(u64, new_snd_una)
+		__field(u64, new_wnd_end)
+		__field(u64, msk_wnd_end)
+	),
+
+	TP_fast_assign(
+		__entry->data_ack = data_ack;
+		__entry->old_snd_una = old_snd_una;
+		__entry->new_snd_una = new_snd_una;
+		__entry->new_wnd_end = new_wnd_end;
+		__entry->msk_wnd_end = msk_wnd_end;
+	),
+
+	TP_printk("data_ack=%llu old_snd_una=%llu new_snd_una=%llu new_wnd_end=%llu msk_wnd_end=%llu",
+		  __entry->data_ack, __entry->old_snd_una,
+		  __entry->new_snd_una, __entry->new_wnd_end,
+		  __entry->msk_wnd_end)
+);
+
+TRACE_EVENT(subflow_check_data_avail,
+
+	TP_PROTO(__u8 status, struct sk_buff *skb),
+
+	TP_ARGS(status, skb),
+
+	TP_STRUCT__entry(
+		__field(u8, status)
+		__field(const void *, skb)
+	),
+
+	TP_fast_assign(
+		__entry->status = status;
+		__entry->skb = skb;
+	),
+
+	TP_printk("mapping_status=%s, skb=%p",
+		  show_mapping_status(__entry->status),
+		  __entry->skb)
+);
+
+#include <trace/events/net_probe_common.h>
+
+TRACE_EVENT(mptcp_rcvbuf_grow,
+
+	TP_PROTO(struct sock *sk, int time),
+
+	TP_ARGS(sk, time),
+
+	TP_STRUCT__entry(
+		__field(int, time)
+		__field(__u32, rtt_us)
+		__field(__u32, copied)
+		__field(__u32, inq)
+		__field(__u32, space)
+		__field(__u32, ooo_space)
+		__field(__u32, rcvbuf)
+		__field(__u32, rcv_wnd)
+		__field(__u8, scaling_ratio)
+		__field(__u16, sport)
+		__field(__u16, dport)
+		__field(__u16, family)
+		__array(__u8, saddr, 4)
+		__array(__u8, daddr, 4)
+		__array(__u8, saddr_v6, 16)
+		__array(__u8, daddr_v6, 16)
+		__field(const void *, skaddr)
+	),
+
+	TP_fast_assign(
+		struct mptcp_sock *msk = mptcp_sk(sk);
+		struct inet_sock *inet = inet_sk(sk);
+		bool ofo_empty;
+		__be32 *p32;
+
+		__entry->time = time;
+		__entry->rtt_us = mptcp_rtt_us_est(msk) >> 3;
+		__entry->copied = msk->rcvq_space.copied;
+		__entry->inq = mptcp_inq_hint(sk);
+		__entry->space = msk->rcvq_space.space;
+		ofo_empty = RB_EMPTY_ROOT(&msk->out_of_order_queue);
+		__entry->ooo_space = ofo_empty ? 0 :
+				     MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq -
+				     msk->ack_seq;
+
+		__entry->rcvbuf = sk->sk_rcvbuf;
+		__entry->rcv_wnd = atomic64_read(&msk->rcv_wnd_sent) -
+				   msk->ack_seq;
+		__entry->scaling_ratio = msk->scaling_ratio;
+		__entry->sport = ntohs(inet->inet_sport);
+		__entry->dport = ntohs(inet->inet_dport);
+		__entry->family = sk->sk_family;
+
+		p32 = (__be32 *)__entry->saddr;
+		*p32 = inet->inet_saddr;
+
+		p32 = (__be32 *)__entry->daddr;
+		*p32 = inet->inet_daddr;
+
+		TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
+			       sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
+
+		__entry->skaddr = sk;
+	),
+
+	TP_printk("time=%u rtt_us=%u copied=%u inq=%u space=%u ooo=%u scaling_ratio=%u "
+		  "rcvbuf=%u rcv_wnd=%u family=%d sport=%hu dport=%hu saddr=%pI4 "
+		  "daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c skaddr=%p",
+		  __entry->time, __entry->rtt_us, __entry->copied,
+		  __entry->inq, __entry->space, __entry->ooo_space,
+		  __entry->scaling_ratio, __entry->rcvbuf, __entry->rcv_wnd,
+		  __entry->family, __entry->sport, __entry->dport,
+		  __entry->saddr, __entry->daddr, __entry->saddr_v6,
+		  __entry->daddr_v6, __entry->skaddr)
+);
+#endif /* _TRACE_MPTCP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>