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, 399 insertions, 0 deletions

diff --git a/net/sctp/proc.c b/net/sctp/proc.c
new file mode 100644
index 000000000..43433d7e2
--- /dev/null
+++ b/net/sctp/proc.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * Copyright (c) 2003 International Business Machines, Corp.
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *    Sridhar Samudrala <sri@us.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <net/sctp/sctp.h>
+#include <net/ip.h> /* for snmp_fold_field */
+
+static const struct snmp_mib sctp_snmp_list[] = {
+	SNMP_MIB_ITEM("SctpCurrEstab", SCTP_MIB_CURRESTAB),
+	SNMP_MIB_ITEM("SctpActiveEstabs", SCTP_MIB_ACTIVEESTABS),
+	SNMP_MIB_ITEM("SctpPassiveEstabs", SCTP_MIB_PASSIVEESTABS),
+	SNMP_MIB_ITEM("SctpAborteds", SCTP_MIB_ABORTEDS),
+	SNMP_MIB_ITEM("SctpShutdowns", SCTP_MIB_SHUTDOWNS),
+	SNMP_MIB_ITEM("SctpOutOfBlues", SCTP_MIB_OUTOFBLUES),
+	SNMP_MIB_ITEM("SctpChecksumErrors", SCTP_MIB_CHECKSUMERRORS),
+	SNMP_MIB_ITEM("SctpOutCtrlChunks", SCTP_MIB_OUTCTRLCHUNKS),
+	SNMP_MIB_ITEM("SctpOutOrderChunks", SCTP_MIB_OUTORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpOutUnorderChunks", SCTP_MIB_OUTUNORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpInCtrlChunks", SCTP_MIB_INCTRLCHUNKS),
+	SNMP_MIB_ITEM("SctpInOrderChunks", SCTP_MIB_INORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpInUnorderChunks", SCTP_MIB_INUNORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpFragUsrMsgs", SCTP_MIB_FRAGUSRMSGS),
+	SNMP_MIB_ITEM("SctpReasmUsrMsgs", SCTP_MIB_REASMUSRMSGS),
+	SNMP_MIB_ITEM("SctpOutSCTPPacks", SCTP_MIB_OUTSCTPPACKS),
+	SNMP_MIB_ITEM("SctpInSCTPPacks", SCTP_MIB_INSCTPPACKS),
+	SNMP_MIB_ITEM("SctpT1InitExpireds", SCTP_MIB_T1_INIT_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT1CookieExpireds", SCTP_MIB_T1_COOKIE_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT2ShutdownExpireds", SCTP_MIB_T2_SHUTDOWN_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT3RtxExpireds", SCTP_MIB_T3_RTX_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT4RtoExpireds", SCTP_MIB_T4_RTO_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT5ShutdownGuardExpireds", SCTP_MIB_T5_SHUTDOWN_GUARD_EXPIREDS),
+	SNMP_MIB_ITEM("SctpDelaySackExpireds", SCTP_MIB_DELAY_SACK_EXPIREDS),
+	SNMP_MIB_ITEM("SctpAutocloseExpireds", SCTP_MIB_AUTOCLOSE_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT3Retransmits", SCTP_MIB_T3_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpPmtudRetransmits", SCTP_MIB_PMTUD_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpFastRetransmits", SCTP_MIB_FAST_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpInPktSoftirq", SCTP_MIB_IN_PKT_SOFTIRQ),
+	SNMP_MIB_ITEM("SctpInPktBacklog", SCTP_MIB_IN_PKT_BACKLOG),
+	SNMP_MIB_ITEM("SctpInPktDiscards", SCTP_MIB_IN_PKT_DISCARDS),
+	SNMP_MIB_ITEM("SctpInDataChunkDiscards", SCTP_MIB_IN_DATA_CHUNK_DISCARDS),
+};
+
+/* Display sctp snmp mib statistics(/proc/net/sctp/snmp). */
+static int sctp_snmp_seq_show(struct seq_file *seq, void *v)
+{
+	unsigned long buff[ARRAY_SIZE(sctp_snmp_list)];
+	const int cnt = ARRAY_SIZE(sctp_snmp_list);
+	struct net *net = seq->private;
+	int i;
+
+	memset(buff, 0, sizeof(buff));
+
+	snmp_get_cpu_field_batch_cnt(buff, sctp_snmp_list, cnt,
+				     net->sctp.sctp_statistics);
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, "%-32s\t%ld\n", sctp_snmp_list[i].name,
+						buff[i]);
+
+	return 0;
+}
+
+/* Dump local addresses of an association/endpoint. */
+static void sctp_seq_dump_local_addrs(struct seq_file *seq, struct sctp_ep_common *epb)
+{
+	struct sctp_association *asoc;
+	struct sctp_sockaddr_entry *laddr;
+	struct sctp_transport *peer;
+	union sctp_addr *addr, *primary = NULL;
+	struct sctp_af *af;
+
+	if (epb->type == SCTP_EP_TYPE_ASSOCIATION) {
+		asoc = sctp_assoc(epb);
+
+		peer = asoc->peer.primary_path;
+		if (unlikely(peer == NULL)) {
+			WARN(1, "Association %p with NULL primary path!\n", asoc);
+			return;
+		}
+
+		primary = &peer->saddr;
+	}
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(laddr, &epb->bind_addr.address_list, list) {
+		if (!laddr->valid)
+			continue;
+
+		addr = &laddr->a;
+		af = sctp_get_af_specific(addr->sa.sa_family);
+		if (primary && af->cmp_addr(addr, primary)) {
+			seq_printf(seq, "*");
+		}
+		af->seq_dump_addr(seq, addr);
+	}
+	rcu_read_unlock();
+}
+
+/* Dump remote addresses of an association. */
+static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_association *assoc)
+{
+	struct sctp_transport *transport;
+	union sctp_addr *addr, *primary;
+	struct sctp_af *af;
+
+	primary = &assoc->peer.primary_addr;
+	list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list,
+			transports) {
+		addr = &transport->ipaddr;
+
+		af = sctp_get_af_specific(addr->sa.sa_family);
+		if (af->cmp_addr(addr, primary)) {
+			seq_printf(seq, "*");
+		}
+		af->seq_dump_addr(seq, addr);
+	}
+}
+
+static void *sctp_eps_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	if (*pos >= sctp_ep_hashsize)
+		return NULL;
+
+	if (*pos < 0)
+		*pos = 0;
+
+	if (*pos == 0)
+		seq_printf(seq, " ENDPT     SOCK   STY SST HBKT LPORT   UID INODE LADDRS\n");
+
+	return (void *)pos;
+}
+
+static void sctp_eps_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+
+static void *sctp_eps_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	if (++*pos >= sctp_ep_hashsize)
+		return NULL;
+
+	return pos;
+}
+
+
+/* Display sctp endpoints (/proc/net/sctp/eps). */
+static int sctp_eps_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_hashbucket *head;
+	struct sctp_endpoint *ep;
+	struct sock *sk;
+	int    hash = *(loff_t *)v;
+
+	if (hash >= sctp_ep_hashsize)
+		return -ENOMEM;
+
+	head = &sctp_ep_hashtable[hash];
+	read_lock_bh(&head->lock);
+	sctp_for_each_hentry(ep, &head->chain) {
+		sk = ep->base.sk;
+		if (!net_eq(sock_net(sk), seq_file_net(seq)))
+			continue;
+		seq_printf(seq, "%8pK %8pK %-3d %-3d %-4d %-5d %5u %5llu ", ep, sk,
+			   sctp_sk(sk)->type, sk->sk_state, hash,
+			   ep->base.bind_addr.port,
+			   from_kuid_munged(seq_user_ns(seq), sk_uid(sk)),
+			   sock_i_ino(sk));
+
+		sctp_seq_dump_local_addrs(seq, &ep->base);
+		seq_printf(seq, "\n");
+	}
+	read_unlock_bh(&head->lock);
+
+	return 0;
+}
+
+static const struct seq_operations sctp_eps_ops = {
+	.start = sctp_eps_seq_start,
+	.next  = sctp_eps_seq_next,
+	.stop  = sctp_eps_seq_stop,
+	.show  = sctp_eps_seq_show,
+};
+
+struct sctp_ht_iter {
+	struct seq_net_private p;
+	struct rhashtable_iter hti;
+};
+
+static void *sctp_transport_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	sctp_transport_walk_start(&iter->hti);
+
+	return sctp_transport_get_idx(seq_file_net(seq), &iter->hti, *pos);
+}
+
+static void sctp_transport_seq_stop(struct seq_file *seq, void *v)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	if (v && v != SEQ_START_TOKEN) {
+		struct sctp_transport *transport = v;
+
+		sctp_transport_put(transport);
+	}
+
+	sctp_transport_walk_stop(&iter->hti);
+}
+
+static void *sctp_transport_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	if (v && v != SEQ_START_TOKEN) {
+		struct sctp_transport *transport = v;
+
+		sctp_transport_put(transport);
+	}
+
+	++*pos;
+
+	return sctp_transport_get_next(seq_file_net(seq), &iter->hti);
+}
+
+/* Display sctp associations (/proc/net/sctp/assocs). */
+static int sctp_assocs_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_transport *transport;
+	struct sctp_association *assoc;
+	struct sctp_ep_common *epb;
+	struct sock *sk;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, " ASSOC     SOCK   STY SST ST HBKT "
+				"ASSOC-ID TX_QUEUE RX_QUEUE UID INODE LPORT "
+				"RPORT LADDRS <-> RADDRS "
+				"HBINT INS OUTS MAXRT T1X T2X RTXC "
+				"wmema wmemq sndbuf rcvbuf\n");
+		return 0;
+	}
+
+	transport = (struct sctp_transport *)v;
+	assoc = transport->asoc;
+	epb = &assoc->base;
+	sk = epb->sk;
+
+	seq_printf(seq,
+		   "%8pK %8pK %-3d %-3d %-2d %-4d "
+		   "%4d %8d %8d %7u %5llu %-5d %5d ",
+		   assoc, sk, sctp_sk(sk)->type, sk->sk_state,
+		   assoc->state, 0,
+		   assoc->assoc_id,
+		   assoc->sndbuf_used,
+		   atomic_read(&assoc->rmem_alloc),
+		   from_kuid_munged(seq_user_ns(seq), sk_uid(sk)),
+		   sock_i_ino(sk),
+		   epb->bind_addr.port,
+		   assoc->peer.port);
+	seq_printf(seq, " ");
+	sctp_seq_dump_local_addrs(seq, epb);
+	seq_printf(seq, "<-> ");
+	sctp_seq_dump_remote_addrs(seq, assoc);
+	seq_printf(seq, "\t%8lu %5d %5d %4d %4d %4d %8d "
+		   "%8d %8d %8d %8d",
+		assoc->hbinterval, assoc->stream.incnt,
+		assoc->stream.outcnt, assoc->max_retrans,
+		assoc->init_retries, assoc->shutdown_retries,
+		assoc->rtx_data_chunks,
+		refcount_read(&sk->sk_wmem_alloc),
+		READ_ONCE(sk->sk_wmem_queued),
+		sk->sk_sndbuf,
+		sk->sk_rcvbuf);
+	seq_printf(seq, "\n");
+
+	return 0;
+}
+
+static const struct seq_operations sctp_assoc_ops = {
+	.start = sctp_transport_seq_start,
+	.next  = sctp_transport_seq_next,
+	.stop  = sctp_transport_seq_stop,
+	.show  = sctp_assocs_seq_show,
+};
+
+static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_association *assoc;
+	struct sctp_transport *transport, *tsp;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, "ADDR ASSOC_ID HB_ACT RTO MAX_PATH_RTX "
+				"REM_ADDR_RTX START STATE\n");
+		return 0;
+	}
+
+	transport = (struct sctp_transport *)v;
+	assoc = transport->asoc;
+
+	list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,
+				transports) {
+		/*
+		 * The remote address (ADDR)
+		 */
+		tsp->af_specific->seq_dump_addr(seq, &tsp->ipaddr);
+		seq_printf(seq, " ");
+		/*
+		 * The association ID (ASSOC_ID)
+		 */
+		seq_printf(seq, "%d ", tsp->asoc->assoc_id);
+
+		/*
+		 * If the Heartbeat is active (HB_ACT)
+		 * Note: 1 = Active, 0 = Inactive
+		 */
+		seq_printf(seq, "%d ", timer_pending(&tsp->hb_timer));
+
+		/*
+		 * Retransmit time out (RTO)
+		 */
+		seq_printf(seq, "%lu ", tsp->rto);
+
+		/*
+		 * Maximum path retransmit count (PATH_MAX_RTX)
+		 */
+		seq_printf(seq, "%d ", tsp->pathmaxrxt);
+
+		/*
+		 * remote address retransmit count (REM_ADDR_RTX)
+		 * Note: We don't have a way to tally this at the moment
+		 * so lets just leave it as zero for the moment
+		 */
+		seq_puts(seq, "0 ");
+
+		/*
+		 * remote address start time (START).  This is also not
+		 * currently implemented, but we can record it with a
+		 * jiffies marker in a subsequent patch
+		 */
+		seq_puts(seq, "0 ");
+
+		/*
+		 * The current state of this destination. I.e.
+		 * SCTP_ACTIVE, SCTP_INACTIVE, ...
+		 */
+		seq_printf(seq, "%d", tsp->state);
+
+		seq_printf(seq, "\n");
+	}
+
+	return 0;
+}
+
+static const struct seq_operations sctp_remaddr_ops = {
+	.start = sctp_transport_seq_start,
+	.next  = sctp_transport_seq_next,
+	.stop  = sctp_transport_seq_stop,
+	.show  = sctp_remaddr_seq_show,
+};
+
+/* Set up the proc fs entry for the SCTP protocol. */
+int __net_init sctp_proc_init(struct net *net)
+{
+	net->sctp.proc_net_sctp = proc_net_mkdir(net, "sctp", net->proc_net);
+	if (!net->sctp.proc_net_sctp)
+		return -ENOMEM;
+	if (!proc_create_net_single("snmp", 0444, net->sctp.proc_net_sctp,
+			 sctp_snmp_seq_show, NULL))
+		goto cleanup;
+	if (!proc_create_net("eps", 0444, net->sctp.proc_net_sctp,
+			&sctp_eps_ops, sizeof(struct seq_net_private)))
+		goto cleanup;
+	if (!proc_create_net("assocs", 0444, net->sctp.proc_net_sctp,
+			&sctp_assoc_ops, sizeof(struct sctp_ht_iter)))
+		goto cleanup;
+	if (!proc_create_net("remaddr", 0444, net->sctp.proc_net_sctp,
+			&sctp_remaddr_ops, sizeof(struct sctp_ht_iter)))
+		goto cleanup;
+	return 0;
+
+cleanup:
+	remove_proc_subtree("sctp", net->proc_net);
+	net->sctp.proc_net_sctp = NULL;
+	return -ENOMEM;
+}