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, 432 insertions, 0 deletions

diff --git a/net/nfc/rawsock.c b/net/nfc/rawsock.c
new file mode 100644
index 000000000..f7d7a599f
--- /dev/null
+++ b/net/nfc/rawsock.c
@@ -0,0 +1,432 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2011 Instituto Nokia de Tecnologia
+ *
+ * Authors:
+ *    Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
+ *    Lauro Ramos Venancio <lauro.venancio@openbossa.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": %s: " fmt, __func__
+
+#include <net/tcp_states.h>
+#include <linux/nfc.h>
+#include <linux/export.h>
+#include <linux/kcov.h>
+
+#include "nfc.h"
+
+static struct nfc_sock_list raw_sk_list = {
+	.lock = __RW_LOCK_UNLOCKED(raw_sk_list.lock)
+};
+
+static void nfc_sock_link(struct nfc_sock_list *l, struct sock *sk)
+{
+	write_lock(&l->lock);
+	sk_add_node(sk, &l->head);
+	write_unlock(&l->lock);
+}
+
+static void nfc_sock_unlink(struct nfc_sock_list *l, struct sock *sk)
+{
+	write_lock(&l->lock);
+	sk_del_node_init(sk);
+	write_unlock(&l->lock);
+}
+
+static void rawsock_write_queue_purge(struct sock *sk)
+{
+	pr_debug("sk=%p\n", sk);
+
+	spin_lock_bh(&sk->sk_write_queue.lock);
+	__skb_queue_purge(&sk->sk_write_queue);
+	nfc_rawsock(sk)->tx_work_scheduled = false;
+	spin_unlock_bh(&sk->sk_write_queue.lock);
+}
+
+static void rawsock_report_error(struct sock *sk, int err)
+{
+	pr_debug("sk=%p err=%d\n", sk, err);
+
+	sk->sk_shutdown = SHUTDOWN_MASK;
+	sk->sk_err = -err;
+	sk_error_report(sk);
+
+	rawsock_write_queue_purge(sk);
+}
+
+static int rawsock_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	pr_debug("sock=%p sk=%p\n", sock, sk);
+
+	if (!sk)
+		return 0;
+
+	if (sock->type == SOCK_RAW)
+		nfc_sock_unlink(&raw_sk_list, sk);
+
+	if (sk->sk_state == TCP_ESTABLISHED) {
+		/* Prevent rawsock_tx_work from starting new transmits and
+		 * wait for any in-progress work to finish.  This must happen
+		 * before the socket is orphaned to avoid a race where
+		 * rawsock_tx_work runs after the NCI device has been freed.
+		 */
+		sk->sk_shutdown |= SEND_SHUTDOWN;
+		cancel_work_sync(&nfc_rawsock(sk)->tx_work);
+		rawsock_write_queue_purge(sk);
+	}
+
+	sock_orphan(sk);
+	sock_put(sk);
+
+	return 0;
+}
+
+static int rawsock_connect(struct socket *sock, struct sockaddr_unsized *_addr,
+			   int len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_nfc *addr = (struct sockaddr_nfc *)_addr;
+	struct nfc_dev *dev;
+	int rc = 0;
+
+	pr_debug("sock=%p sk=%p flags=%d\n", sock, sk, flags);
+
+	if (!addr || len < sizeof(struct sockaddr_nfc) ||
+	    addr->sa_family != AF_NFC)
+		return -EINVAL;
+
+	pr_debug("addr dev_idx=%u target_idx=%u protocol=%u\n",
+		 addr->dev_idx, addr->target_idx, addr->nfc_protocol);
+
+	lock_sock(sk);
+
+	if (sock->state == SS_CONNECTED) {
+		rc = -EISCONN;
+		goto error;
+	}
+
+	dev = nfc_get_device(addr->dev_idx);
+	if (!dev) {
+		rc = -ENODEV;
+		goto error;
+	}
+
+	if (addr->target_idx > dev->target_next_idx - 1 ||
+	    addr->target_idx < dev->target_next_idx - dev->n_targets) {
+		rc = -EINVAL;
+		goto put_dev;
+	}
+
+	rc = nfc_activate_target(dev, addr->target_idx, addr->nfc_protocol);
+	if (rc)
+		goto put_dev;
+
+	nfc_rawsock(sk)->dev = dev;
+	nfc_rawsock(sk)->target_idx = addr->target_idx;
+	sock->state = SS_CONNECTED;
+	sk->sk_state = TCP_ESTABLISHED;
+	sk->sk_state_change(sk);
+
+	release_sock(sk);
+	return 0;
+
+put_dev:
+	nfc_put_device(dev);
+error:
+	release_sock(sk);
+	return rc;
+}
+
+static int rawsock_add_header(struct sk_buff *skb)
+{
+	*(u8 *)skb_push(skb, NFC_HEADER_SIZE) = 0;
+
+	return 0;
+}
+
+static void rawsock_data_exchange_complete(void *context, struct sk_buff *skb,
+					   int err)
+{
+	struct sock *sk = (struct sock *) context;
+
+	BUG_ON(in_hardirq());
+
+	pr_debug("sk=%p err=%d\n", sk, err);
+
+	if (err)
+		goto error;
+
+	err = rawsock_add_header(skb);
+	if (err)
+		goto error_skb;
+
+	err = sock_queue_rcv_skb(sk, skb);
+	if (err)
+		goto error_skb;
+
+	spin_lock_bh(&sk->sk_write_queue.lock);
+	if (!skb_queue_empty(&sk->sk_write_queue))
+		schedule_work(&nfc_rawsock(sk)->tx_work);
+	else
+		nfc_rawsock(sk)->tx_work_scheduled = false;
+	spin_unlock_bh(&sk->sk_write_queue.lock);
+
+	sock_put(sk);
+	return;
+
+error_skb:
+	kfree_skb(skb);
+
+error:
+	rawsock_report_error(sk, err);
+	sock_put(sk);
+}
+
+static void rawsock_tx_work(struct work_struct *work)
+{
+	struct sock *sk = to_rawsock_sk(work);
+	struct nfc_dev *dev = nfc_rawsock(sk)->dev;
+	u32 target_idx = nfc_rawsock(sk)->target_idx;
+	struct sk_buff *skb;
+	int rc;
+
+	pr_debug("sk=%p target_idx=%u\n", sk, target_idx);
+
+	if (sk->sk_shutdown & SEND_SHUTDOWN) {
+		rawsock_write_queue_purge(sk);
+		return;
+	}
+
+	skb = skb_dequeue(&sk->sk_write_queue);
+	kcov_remote_start_common(skb_get_kcov_handle(skb));
+
+	sock_hold(sk);
+	rc = nfc_data_exchange(dev, target_idx, skb,
+			       rawsock_data_exchange_complete, sk);
+	if (rc) {
+		rawsock_report_error(sk, rc);
+		sock_put(sk);
+	}
+	kcov_remote_stop();
+}
+
+static int rawsock_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
+{
+	struct sock *sk = sock->sk;
+	struct nfc_dev *dev = nfc_rawsock(sk)->dev;
+	struct sk_buff *skb;
+	int rc;
+
+	pr_debug("sock=%p sk=%p len=%zu\n", sock, sk, len);
+
+	if (msg->msg_namelen)
+		return -EOPNOTSUPP;
+
+	if (sock->state != SS_CONNECTED)
+		return -ENOTCONN;
+
+	skb = nfc_alloc_send_skb(dev, sk, msg->msg_flags, len, &rc);
+	if (skb == NULL)
+		return rc;
+
+	rc = memcpy_from_msg(skb_put(skb, len), msg, len);
+	if (rc < 0) {
+		kfree_skb(skb);
+		return rc;
+	}
+
+	spin_lock_bh(&sk->sk_write_queue.lock);
+	__skb_queue_tail(&sk->sk_write_queue, skb);
+	if (!nfc_rawsock(sk)->tx_work_scheduled) {
+		schedule_work(&nfc_rawsock(sk)->tx_work);
+		nfc_rawsock(sk)->tx_work_scheduled = true;
+	}
+	spin_unlock_bh(&sk->sk_write_queue.lock);
+
+	return len;
+}
+
+static int rawsock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+			   int flags)
+{
+	struct sock *sk = sock->sk;
+	struct sk_buff *skb;
+	int copied;
+	int rc;
+
+	pr_debug("sock=%p sk=%p len=%zu flags=%d\n", sock, sk, len, flags);
+
+	skb = skb_recv_datagram(sk, flags, &rc);
+	if (!skb)
+		return rc;
+
+	copied = skb->len;
+	if (len < copied) {
+		msg->msg_flags |= MSG_TRUNC;
+		copied = len;
+	}
+
+	rc = skb_copy_datagram_msg(skb, 0, msg, copied);
+
+	skb_free_datagram(sk, skb);
+
+	return rc ? : copied;
+}
+
+static const struct proto_ops rawsock_ops = {
+	.family         = PF_NFC,
+	.owner          = THIS_MODULE,
+	.release        = rawsock_release,
+	.bind           = sock_no_bind,
+	.connect        = rawsock_connect,
+	.socketpair     = sock_no_socketpair,
+	.accept         = sock_no_accept,
+	.getname        = sock_no_getname,
+	.poll           = datagram_poll,
+	.ioctl          = sock_no_ioctl,
+	.listen         = sock_no_listen,
+	.shutdown       = sock_no_shutdown,
+	.sendmsg        = rawsock_sendmsg,
+	.recvmsg        = rawsock_recvmsg,
+	.mmap           = sock_no_mmap,
+};
+
+static const struct proto_ops rawsock_raw_ops = {
+	.family         = PF_NFC,
+	.owner          = THIS_MODULE,
+	.release        = rawsock_release,
+	.bind           = sock_no_bind,
+	.connect        = sock_no_connect,
+	.socketpair     = sock_no_socketpair,
+	.accept         = sock_no_accept,
+	.getname        = sock_no_getname,
+	.poll           = datagram_poll,
+	.ioctl          = sock_no_ioctl,
+	.listen         = sock_no_listen,
+	.shutdown       = sock_no_shutdown,
+	.sendmsg        = sock_no_sendmsg,
+	.recvmsg        = rawsock_recvmsg,
+	.mmap           = sock_no_mmap,
+};
+
+static void rawsock_destruct(struct sock *sk)
+{
+	pr_debug("sk=%p\n", sk);
+
+	if (sk->sk_state == TCP_ESTABLISHED) {
+		nfc_deactivate_target(nfc_rawsock(sk)->dev,
+				      nfc_rawsock(sk)->target_idx,
+				      NFC_TARGET_MODE_IDLE);
+		nfc_put_device(nfc_rawsock(sk)->dev);
+	}
+
+	skb_queue_purge(&sk->sk_receive_queue);
+
+	if (!sock_flag(sk, SOCK_DEAD)) {
+		pr_err("Freeing alive NFC raw socket %p\n", sk);
+		return;
+	}
+}
+
+static int rawsock_create(struct net *net, struct socket *sock,
+			  const struct nfc_protocol *nfc_proto, int kern)
+{
+	struct sock *sk;
+
+	pr_debug("sock=%p\n", sock);
+
+	if ((sock->type != SOCK_SEQPACKET) && (sock->type != SOCK_RAW))
+		return -ESOCKTNOSUPPORT;
+
+	if (sock->type == SOCK_RAW) {
+		if (!ns_capable(net->user_ns, CAP_NET_RAW))
+			return -EPERM;
+		sock->ops = &rawsock_raw_ops;
+	} else {
+		sock->ops = &rawsock_ops;
+	}
+
+	sk = sk_alloc(net, PF_NFC, GFP_ATOMIC, nfc_proto->proto, kern);
+	if (!sk)
+		return -ENOMEM;
+
+	sock_init_data(sock, sk);
+	sk->sk_protocol = nfc_proto->id;
+	sk->sk_destruct = rawsock_destruct;
+	sock->state = SS_UNCONNECTED;
+	if (sock->type == SOCK_RAW)
+		nfc_sock_link(&raw_sk_list, sk);
+	else {
+		INIT_WORK(&nfc_rawsock(sk)->tx_work, rawsock_tx_work);
+		nfc_rawsock(sk)->tx_work_scheduled = false;
+	}
+
+	return 0;
+}
+
+void nfc_send_to_raw_sock(struct nfc_dev *dev, struct sk_buff *skb,
+			  u8 payload_type, u8 direction)
+{
+	struct sk_buff *skb_copy = NULL, *nskb;
+	struct sock *sk;
+	u8 *data;
+
+	read_lock(&raw_sk_list.lock);
+
+	sk_for_each(sk, &raw_sk_list.head) {
+		if (!skb_copy) {
+			skb_copy = __pskb_copy_fclone(skb, NFC_RAW_HEADER_SIZE,
+						      GFP_ATOMIC, true);
+			if (!skb_copy)
+				continue;
+
+			data = skb_push(skb_copy, NFC_RAW_HEADER_SIZE);
+
+			data[0] = dev ? dev->idx : 0xFF;
+			data[1] = direction & 0x01;
+			data[1] |= (payload_type << 1);
+		}
+
+		nskb = skb_clone(skb_copy, GFP_ATOMIC);
+		if (!nskb)
+			continue;
+
+		if (sock_queue_rcv_skb(sk, nskb))
+			kfree_skb(nskb);
+	}
+
+	read_unlock(&raw_sk_list.lock);
+
+	kfree_skb(skb_copy);
+}
+EXPORT_SYMBOL(nfc_send_to_raw_sock);
+
+static struct proto rawsock_proto = {
+	.name     = "NFC_RAW",
+	.owner    = THIS_MODULE,
+	.obj_size = sizeof(struct nfc_rawsock),
+};
+
+static const struct nfc_protocol rawsock_nfc_proto = {
+	.id	  = NFC_SOCKPROTO_RAW,
+	.proto    = &rawsock_proto,
+	.owner    = THIS_MODULE,
+	.create   = rawsock_create
+};
+
+int __init rawsock_init(void)
+{
+	int rc;
+
+	rc = nfc_proto_register(&rawsock_nfc_proto);
+
+	return rc;
+}
+
+void rawsock_exit(void)
+{
+	nfc_proto_unregister(&rawsock_nfc_proto);
+}