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, 283 insertions, 0 deletions

diff --git a/net/rds/bind.c b/net/rds/bind.c
new file mode 100644
index 000000000..f800d920d
--- /dev/null
+++ b/net/rds/bind.c
@@ -0,0 +1,283 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <net/sock.h>
+#include <linux/in.h>
+#include <linux/ipv6.h>
+#include <linux/if_arp.h>
+#include <linux/jhash.h>
+#include <linux/ratelimit.h>
+#include "rds.h"
+
+static struct rhashtable bind_hash_table;
+
+static const struct rhashtable_params ht_parms = {
+	.nelem_hint = 768,
+	.key_len = RDS_BOUND_KEY_LEN,
+	.key_offset = offsetof(struct rds_sock, rs_bound_key),
+	.head_offset = offsetof(struct rds_sock, rs_bound_node),
+	.max_size = 16384,
+	.min_size = 1024,
+};
+
+/* Create a key for the bind hash table manipulation.  Port is in network byte
+ * order.
+ */
+static inline void __rds_create_bind_key(u8 *key, const struct in6_addr *addr,
+					 __be16 port, __u32 scope_id)
+{
+	memcpy(key, addr, sizeof(*addr));
+	key += sizeof(*addr);
+	memcpy(key, &port, sizeof(port));
+	key += sizeof(port);
+	memcpy(key, &scope_id, sizeof(scope_id));
+}
+
+/*
+ * Return the rds_sock bound at the given local address.
+ *
+ * The rx path can race with rds_release.  We notice if rds_release() has
+ * marked this socket and don't return a rs ref to the rx path.
+ */
+struct rds_sock *rds_find_bound(const struct in6_addr *addr, __be16 port,
+				__u32 scope_id)
+{
+	u8 key[RDS_BOUND_KEY_LEN];
+	struct rds_sock *rs;
+
+	__rds_create_bind_key(key, addr, port, scope_id);
+	rcu_read_lock();
+	rs = rhashtable_lookup(&bind_hash_table, key, ht_parms);
+	if (rs && (sock_flag(rds_rs_to_sk(rs), SOCK_DEAD) ||
+		   !refcount_inc_not_zero(&rds_rs_to_sk(rs)->sk_refcnt)))
+		rs = NULL;
+
+	rcu_read_unlock();
+
+	rdsdebug("returning rs %p for %pI6c:%u\n", rs, addr,
+		 ntohs(port));
+
+	return rs;
+}
+
+/* returns -ve errno or +ve port */
+static int rds_add_bound(struct rds_sock *rs, const struct in6_addr *addr,
+			 __be16 *port, __u32 scope_id)
+{
+	int ret = -EADDRINUSE;
+	u16 rover, last;
+	u8 key[RDS_BOUND_KEY_LEN];
+
+	if (*port != 0) {
+		rover = be16_to_cpu(*port);
+		if (rover == RDS_FLAG_PROBE_PORT)
+			return -EINVAL;
+		last = rover;
+	} else {
+		rover = max_t(u16, get_random_u16(), 2);
+		last = rover - 1;
+	}
+
+	do {
+		if (rover == 0)
+			rover++;
+
+		if (rover == RDS_FLAG_PROBE_PORT)
+			continue;
+		__rds_create_bind_key(key, addr, cpu_to_be16(rover),
+				      scope_id);
+		if (rhashtable_lookup_fast(&bind_hash_table, key, ht_parms))
+			continue;
+
+		memcpy(rs->rs_bound_key, key, sizeof(rs->rs_bound_key));
+		rs->rs_bound_addr = *addr;
+		net_get_random_once(&rs->rs_hash_initval,
+				    sizeof(rs->rs_hash_initval));
+		rs->rs_bound_port = cpu_to_be16(rover);
+		rs->rs_bound_node.next = NULL;
+		rds_sock_addref(rs);
+		if (!rhashtable_insert_fast(&bind_hash_table,
+					    &rs->rs_bound_node, ht_parms)) {
+			*port = rs->rs_bound_port;
+			rs->rs_bound_scope_id = scope_id;
+			ret = 0;
+			rdsdebug("rs %p binding to %pI6c:%d\n",
+				 rs, addr, (int)ntohs(*port));
+			break;
+		} else {
+			rs->rs_bound_addr = in6addr_any;
+			rds_sock_put(rs);
+			ret = -ENOMEM;
+			break;
+		}
+	} while (rover++ != last);
+
+	return ret;
+}
+
+void rds_remove_bound(struct rds_sock *rs)
+{
+
+	if (ipv6_addr_any(&rs->rs_bound_addr))
+		return;
+
+	rdsdebug("rs %p unbinding from %pI6c:%d\n",
+		 rs, &rs->rs_bound_addr,
+		 ntohs(rs->rs_bound_port));
+
+	rhashtable_remove_fast(&bind_hash_table, &rs->rs_bound_node, ht_parms);
+	rds_sock_put(rs);
+	rs->rs_bound_addr = in6addr_any;
+}
+
+int rds_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	struct in6_addr v6addr, *binding_addr;
+	struct rds_transport *trans;
+	__u32 scope_id = 0;
+	int ret = 0;
+	__be16 port;
+
+	/* We allow an RDS socket to be bound to either IPv4 or IPv6
+	 * address.
+	 */
+	if (addr_len < offsetofend(struct sockaddr, sa_family))
+		return -EINVAL;
+	if (uaddr->sa_family == AF_INET) {
+		struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
+
+		if (addr_len < sizeof(struct sockaddr_in) ||
+		    sin->sin_addr.s_addr == htonl(INADDR_ANY) ||
+		    sin->sin_addr.s_addr == htonl(INADDR_BROADCAST) ||
+		    ipv4_is_multicast(sin->sin_addr.s_addr))
+			return -EINVAL;
+		ipv6_addr_set_v4mapped(sin->sin_addr.s_addr, &v6addr);
+		binding_addr = &v6addr;
+		port = sin->sin_port;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (uaddr->sa_family == AF_INET6) {
+		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)uaddr;
+		int addr_type;
+
+		if (addr_len < sizeof(struct sockaddr_in6))
+			return -EINVAL;
+		addr_type = ipv6_addr_type(&sin6->sin6_addr);
+		if (!(addr_type & IPV6_ADDR_UNICAST)) {
+			__be32 addr4;
+
+			if (!(addr_type & IPV6_ADDR_MAPPED))
+				return -EINVAL;
+
+			/* It is a mapped address.  Need to do some sanity
+			 * checks.
+			 */
+			addr4 = sin6->sin6_addr.s6_addr32[3];
+			if (addr4 == htonl(INADDR_ANY) ||
+			    addr4 == htonl(INADDR_BROADCAST) ||
+			    ipv4_is_multicast(addr4))
+				return -EINVAL;
+		}
+		/* The scope ID must be specified for link local address. */
+		if (addr_type & IPV6_ADDR_LINKLOCAL) {
+			if (sin6->sin6_scope_id == 0)
+				return -EINVAL;
+			scope_id = sin6->sin6_scope_id;
+		}
+		binding_addr = &sin6->sin6_addr;
+		port = sin6->sin6_port;
+#endif
+	} else {
+		return -EINVAL;
+	}
+	lock_sock(sk);
+
+	/* RDS socket does not allow re-binding. */
+	if (!ipv6_addr_any(&rs->rs_bound_addr)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	/* Socket is connected.  The binding address should have the same
+	 * scope ID as the connected address, except the case when one is
+	 * non-link local address (scope_id is 0).
+	 */
+	if (!ipv6_addr_any(&rs->rs_conn_addr) && scope_id &&
+	    rs->rs_bound_scope_id &&
+	    scope_id != rs->rs_bound_scope_id) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* The transport can be set using SO_RDS_TRANSPORT option before the
+	 * socket is bound.
+	 */
+	if (rs->rs_transport) {
+		trans = rs->rs_transport;
+		if (!trans->laddr_check ||
+		    trans->laddr_check(sock_net(sock->sk),
+				       binding_addr, scope_id) != 0) {
+			ret = -ENOPROTOOPT;
+			goto out;
+		}
+	} else {
+		trans = rds_trans_get_preferred(sock_net(sock->sk),
+						binding_addr, scope_id);
+		if (!trans) {
+			ret = -EADDRNOTAVAIL;
+			pr_info_ratelimited("RDS: %s could not find a transport for %pI6c, load rds_tcp or rds_rdma?\n",
+					    __func__, binding_addr);
+			goto out;
+		}
+		rs->rs_transport = trans;
+	}
+
+	sock_set_flag(sk, SOCK_RCU_FREE);
+	ret = rds_add_bound(rs, binding_addr, &port, scope_id);
+	if (ret)
+		rs->rs_transport = NULL;
+
+out:
+	release_sock(sk);
+	return ret;
+}
+
+void rds_bind_lock_destroy(void)
+{
+	rhashtable_destroy(&bind_hash_table);
+}
+
+int rds_bind_lock_init(void)
+{
+	return rhashtable_init(&bind_hash_table, &ht_parms);
+}