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, 486 insertions, 0 deletions

diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
new file mode 100644
index 000000000..169f9dfda
--- /dev/null
+++ b/net/rxrpc/local_object.c
@@ -0,0 +1,486 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Local endpoint object management
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/udp.h>
+#include <linux/ip.h>
+#include <linux/hashtable.h>
+#include <net/sock.h>
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+#include <net/af_rxrpc.h>
+#include "ar-internal.h"
+
+static void rxrpc_local_rcu(struct rcu_head *);
+
+/*
+ * Handle an ICMP/ICMP6 error turning up at the tunnel.  Push it through the
+ * usual mechanism so that it gets parsed and presented through the UDP
+ * socket's error_report().
+ */
+static void rxrpc_encap_err_rcv(struct sock *sk, struct sk_buff *skb, int err,
+				__be16 port, u32 info, u8 *payload)
+{
+	if (ip_hdr(skb)->version == IPVERSION)
+		return ip_icmp_error(sk, skb, err, port, info, payload);
+	if (IS_ENABLED(CONFIG_AF_RXRPC_IPV6))
+		return ipv6_icmp_error(sk, skb, err, port, info, payload);
+}
+
+/*
+ * Set or clear the Don't Fragment flag on a socket.
+ */
+void rxrpc_local_dont_fragment(const struct rxrpc_local *local, bool set)
+{
+	if (set)
+		ip_sock_set_mtu_discover(local->socket->sk, IP_PMTUDISC_DO);
+	else
+		ip_sock_set_mtu_discover(local->socket->sk, IP_PMTUDISC_DONT);
+}
+
+/*
+ * Compare a local to an address.  Return -ve, 0 or +ve to indicate less than,
+ * same or greater than.
+ *
+ * We explicitly don't compare the RxRPC service ID as we want to reject
+ * conflicting uses by differing services.  Further, we don't want to share
+ * addresses with different options (IPv6), so we don't compare those bits
+ * either.
+ */
+static long rxrpc_local_cmp_key(const struct rxrpc_local *local,
+				const struct sockaddr_rxrpc *srx)
+{
+	long diff;
+
+	diff = ((local->srx.transport_type - srx->transport_type) ?:
+		(local->srx.transport_len - srx->transport_len) ?:
+		(local->srx.transport.family - srx->transport.family));
+	if (diff != 0)
+		return diff;
+
+	switch (srx->transport.family) {
+	case AF_INET:
+		/* If the choice of UDP port is left up to the transport, then
+		 * the endpoint record doesn't match.
+		 */
+		return ((u16 __force)local->srx.transport.sin.sin_port -
+			(u16 __force)srx->transport.sin.sin_port) ?:
+			memcmp(&local->srx.transport.sin.sin_addr,
+			       &srx->transport.sin.sin_addr,
+			       sizeof(struct in_addr));
+#ifdef CONFIG_AF_RXRPC_IPV6
+	case AF_INET6:
+		/* If the choice of UDP6 port is left up to the transport, then
+		 * the endpoint record doesn't match.
+		 */
+		return ((u16 __force)local->srx.transport.sin6.sin6_port -
+			(u16 __force)srx->transport.sin6.sin6_port) ?:
+			memcmp(&local->srx.transport.sin6.sin6_addr,
+			       &srx->transport.sin6.sin6_addr,
+			       sizeof(struct in6_addr));
+#endif
+	default:
+		BUG();
+	}
+}
+
+static void rxrpc_client_conn_reap_timeout(struct timer_list *timer)
+{
+	struct rxrpc_local *local =
+		container_of(timer, struct rxrpc_local, client_conn_reap_timer);
+
+	if (!local->kill_all_client_conns &&
+	    test_and_set_bit(RXRPC_CLIENT_CONN_REAP_TIMER, &local->client_conn_flags))
+		rxrpc_wake_up_io_thread(local);
+}
+
+/*
+ * Allocate a new local endpoint.
+ */
+static struct rxrpc_local *rxrpc_alloc_local(struct net *net,
+					     const struct sockaddr_rxrpc *srx)
+{
+	struct rxrpc_local *local;
+	u32 tmp;
+
+	local = kzalloc_obj(struct rxrpc_local);
+	if (local) {
+		refcount_set(&local->ref, 1);
+		atomic_set(&local->active_users, 1);
+		local->net = net;
+		local->rxnet = rxrpc_net(net);
+		INIT_HLIST_NODE(&local->link);
+		init_completion(&local->io_thread_ready);
+#ifdef CONFIG_AF_RXRPC_INJECT_RX_DELAY
+		skb_queue_head_init(&local->rx_delay_queue);
+#endif
+		skb_queue_head_init(&local->rx_queue);
+		INIT_LIST_HEAD(&local->conn_attend_q);
+		INIT_LIST_HEAD(&local->call_attend_q);
+
+		local->client_bundles = RB_ROOT;
+		spin_lock_init(&local->client_bundles_lock);
+		local->kill_all_client_conns = false;
+		INIT_LIST_HEAD(&local->idle_client_conns);
+		timer_setup(&local->client_conn_reap_timer,
+			    rxrpc_client_conn_reap_timeout, 0);
+
+		spin_lock_init(&local->lock);
+		rwlock_init(&local->services_lock);
+		local->debug_id = atomic_inc_return(&rxrpc_debug_id);
+		memcpy(&local->srx, srx, sizeof(*srx));
+		local->srx.srx_service = 0;
+		idr_init(&local->conn_ids);
+		get_random_bytes(&tmp, sizeof(tmp));
+		tmp &= 0x3fffffff;
+		if (tmp == 0)
+			tmp = 1;
+		idr_set_cursor(&local->conn_ids, tmp);
+		INIT_LIST_HEAD(&local->new_client_calls);
+		spin_lock_init(&local->client_call_lock);
+
+		trace_rxrpc_local(local->debug_id, rxrpc_local_new, 1, 1);
+	}
+
+	_leave(" = %p", local);
+	return local;
+}
+
+/*
+ * create the local socket
+ * - must be called with rxrpc_local_mutex locked
+ */
+static int rxrpc_open_socket(struct rxrpc_local *local, struct net *net)
+{
+	struct udp_tunnel_sock_cfg tuncfg = {NULL};
+	struct sockaddr_rxrpc *srx = &local->srx;
+	struct udp_port_cfg udp_conf = {0};
+	struct task_struct *io_thread;
+	struct sock *usk;
+	int ret;
+
+	_enter("%p{%d,%d}",
+	       local, srx->transport_type, srx->transport.family);
+
+	udp_conf.family = srx->transport.family;
+	udp_conf.use_udp_checksums = true;
+	if (udp_conf.family == AF_INET) {
+		udp_conf.local_ip = srx->transport.sin.sin_addr;
+		udp_conf.local_udp_port = srx->transport.sin.sin_port;
+#if IS_ENABLED(CONFIG_AF_RXRPC_IPV6)
+	} else {
+		udp_conf.local_ip6 = srx->transport.sin6.sin6_addr;
+		udp_conf.local_udp_port = srx->transport.sin6.sin6_port;
+		udp_conf.use_udp6_tx_checksums = true;
+		udp_conf.use_udp6_rx_checksums = true;
+#endif
+	}
+	ret = udp_sock_create(net, &udp_conf, &local->socket);
+	if (ret < 0) {
+		_leave(" = %d [socket]", ret);
+		return ret;
+	}
+
+	tuncfg.encap_type = UDP_ENCAP_RXRPC;
+	tuncfg.encap_rcv = rxrpc_encap_rcv;
+	tuncfg.encap_err_rcv = rxrpc_encap_err_rcv;
+	tuncfg.sk_user_data = local;
+	setup_udp_tunnel_sock(net, local->socket->sk, &tuncfg);
+
+	/* set the socket up */
+	usk = local->socket->sk;
+	usk->sk_error_report = rxrpc_error_report;
+
+	switch (srx->transport.family) {
+	case AF_INET6:
+		/* we want to receive ICMPv6 errors */
+		ip6_sock_set_recverr(usk);
+
+		/* Fall through and set IPv4 options too otherwise we don't get
+		 * errors from IPv4 packets sent through the IPv6 socket.
+		 */
+		fallthrough;
+	case AF_INET:
+		/* we want to receive ICMP errors */
+		ip_sock_set_recverr(usk);
+
+		/* we want to set the don't fragment bit */
+		rxrpc_local_dont_fragment(local, true);
+		break;
+
+	default:
+		BUG();
+	}
+
+	io_thread = kthread_run(rxrpc_io_thread, local,
+				"krxrpcio/%u", ntohs(udp_conf.local_udp_port));
+	if (IS_ERR(io_thread)) {
+		ret = PTR_ERR(io_thread);
+		goto error_sock;
+	}
+
+	wait_for_completion(&local->io_thread_ready);
+	WRITE_ONCE(local->io_thread, io_thread);
+	_leave(" = 0");
+	return 0;
+
+error_sock:
+	kernel_sock_shutdown(local->socket, SHUT_RDWR);
+	local->socket->sk->sk_user_data = NULL;
+	sock_release(local->socket);
+	local->socket = NULL;
+	return ret;
+}
+
+/*
+ * Look up or create a new local endpoint using the specified local address.
+ */
+struct rxrpc_local *rxrpc_lookup_local(struct net *net,
+				       const struct sockaddr_rxrpc *srx)
+{
+	struct rxrpc_local *local;
+	struct rxrpc_net *rxnet = rxrpc_net(net);
+	struct hlist_node *cursor;
+	long diff;
+	int ret;
+
+	_enter("{%d,%d,%pISp}",
+	       srx->transport_type, srx->transport.family, &srx->transport);
+
+	mutex_lock(&rxnet->local_mutex);
+
+	hlist_for_each(cursor, &rxnet->local_endpoints) {
+		local = hlist_entry(cursor, struct rxrpc_local, link);
+
+		diff = rxrpc_local_cmp_key(local, srx);
+		if (diff != 0)
+			continue;
+
+		/* Services aren't allowed to share transport sockets, so
+		 * reject that here.  It is possible that the object is dying -
+		 * but it may also still have the local transport address that
+		 * we want bound.
+		 */
+		if (srx->srx_service) {
+			local = NULL;
+			goto addr_in_use;
+		}
+
+		/* Found a match.  We want to replace a dying object.
+		 * Attempting to bind the transport socket may still fail if
+		 * we're attempting to use a local address that the dying
+		 * object is still using.
+		 */
+		if (!rxrpc_use_local(local, rxrpc_local_use_lookup))
+			break;
+
+		goto found;
+	}
+
+	local = rxrpc_alloc_local(net, srx);
+	if (!local)
+		goto nomem;
+
+	ret = rxrpc_open_socket(local, net);
+	if (ret < 0)
+		goto sock_error;
+
+	if (cursor) {
+		hlist_replace_rcu(cursor, &local->link);
+		cursor->pprev = NULL;
+	} else {
+		hlist_add_head_rcu(&local->link, &rxnet->local_endpoints);
+	}
+
+found:
+	mutex_unlock(&rxnet->local_mutex);
+	_leave(" = %p", local);
+	return local;
+
+nomem:
+	ret = -ENOMEM;
+sock_error:
+	mutex_unlock(&rxnet->local_mutex);
+	if (local)
+		call_rcu(&local->rcu, rxrpc_local_rcu);
+	_leave(" = %d", ret);
+	return ERR_PTR(ret);
+
+addr_in_use:
+	mutex_unlock(&rxnet->local_mutex);
+	_leave(" = -EADDRINUSE");
+	return ERR_PTR(-EADDRINUSE);
+}
+
+/*
+ * Get a ref on a local endpoint.
+ */
+struct rxrpc_local *rxrpc_get_local(struct rxrpc_local *local,
+				    enum rxrpc_local_trace why)
+{
+	int r, u;
+
+	u = atomic_read(&local->active_users);
+	__refcount_inc(&local->ref, &r);
+	trace_rxrpc_local(local->debug_id, why, r + 1, u);
+	return local;
+}
+
+/*
+ * Get a ref on a local endpoint unless its usage has already reached 0.
+ */
+struct rxrpc_local *rxrpc_get_local_maybe(struct rxrpc_local *local,
+					  enum rxrpc_local_trace why)
+{
+	int r, u;
+
+	if (local && __refcount_inc_not_zero(&local->ref, &r)) {
+		u = atomic_read(&local->active_users);
+		trace_rxrpc_local(local->debug_id, why, r + 1, u);
+		return local;
+	}
+
+	return NULL;
+}
+
+/*
+ * Drop a ref on a local endpoint.
+ */
+void rxrpc_put_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
+{
+	unsigned int debug_id;
+	bool dead;
+	int r, u;
+
+	if (local) {
+		debug_id = local->debug_id;
+
+		u = atomic_read(&local->active_users);
+		dead = __refcount_dec_and_test(&local->ref, &r);
+		trace_rxrpc_local(debug_id, why, r, u);
+
+		if (dead)
+			call_rcu(&local->rcu, rxrpc_local_rcu);
+	}
+}
+
+/*
+ * Start using a local endpoint.
+ */
+struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local,
+				    enum rxrpc_local_trace why)
+{
+	local = rxrpc_get_local_maybe(local, rxrpc_local_get_for_use);
+	if (!local)
+		return NULL;
+
+	if (!__rxrpc_use_local(local, why)) {
+		rxrpc_put_local(local, rxrpc_local_put_for_use);
+		return NULL;
+	}
+
+	return local;
+}
+
+/*
+ * Cease using a local endpoint.  Once the number of active users reaches 0, we
+ * start the closure of the transport in the I/O thread..
+ */
+void rxrpc_unuse_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
+{
+	unsigned int debug_id;
+	int r, u;
+
+	if (local) {
+		debug_id = local->debug_id;
+		r = refcount_read(&local->ref);
+		u = atomic_dec_return(&local->active_users);
+		trace_rxrpc_local(debug_id, why, r, u);
+		if (u == 0)
+			kthread_stop(local->io_thread);
+	}
+}
+
+/*
+ * Destroy a local endpoint's socket and then hand the record to RCU to dispose
+ * of.
+ *
+ * Closing the socket cannot be done from bottom half context or RCU callback
+ * context because it might sleep.
+ */
+void rxrpc_destroy_local(struct rxrpc_local *local)
+{
+	struct socket *socket = local->socket;
+	struct rxrpc_net *rxnet = local->rxnet;
+
+	_enter("%d", local->debug_id);
+
+	local->dead = true;
+
+	mutex_lock(&rxnet->local_mutex);
+	hlist_del_init_rcu(&local->link);
+	mutex_unlock(&rxnet->local_mutex);
+
+	rxrpc_clean_up_local_conns(local);
+	rxrpc_service_connection_reaper(&rxnet->service_conn_reaper);
+	ASSERT(!local->service);
+
+	if (socket) {
+		local->socket = NULL;
+		kernel_sock_shutdown(socket, SHUT_RDWR);
+		socket->sk->sk_user_data = NULL;
+		sock_release(socket);
+	}
+
+	/* At this point, there should be no more packets coming in to the
+	 * local endpoint.
+	 */
+#ifdef CONFIG_AF_RXRPC_INJECT_RX_DELAY
+	rxrpc_purge_queue(&local->rx_delay_queue);
+#endif
+	rxrpc_purge_queue(&local->rx_queue);
+	rxrpc_purge_client_connections(local);
+	page_frag_cache_drain(&local->tx_alloc);
+}
+
+/*
+ * Destroy a local endpoint after the RCU grace period expires.
+ */
+static void rxrpc_local_rcu(struct rcu_head *rcu)
+{
+	struct rxrpc_local *local = container_of(rcu, struct rxrpc_local, rcu);
+
+	rxrpc_see_local(local, rxrpc_local_free);
+	kfree(local);
+}
+
+/*
+ * Verify the local endpoint list is empty by this point.
+ */
+void rxrpc_destroy_all_locals(struct rxrpc_net *rxnet)
+{
+	struct rxrpc_local *local;
+
+	_enter("");
+
+	flush_workqueue(rxrpc_workqueue);
+
+	if (!hlist_empty(&rxnet->local_endpoints)) {
+		mutex_lock(&rxnet->local_mutex);
+		hlist_for_each_entry(local, &rxnet->local_endpoints, link) {
+			pr_err("AF_RXRPC: Leaked local %p {%d}\n",
+			       local, refcount_read(&local->ref));
+		}
+		mutex_unlock(&rxnet->local_mutex);
+		BUG();
+	}
+}