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, 115 insertions, 0 deletions

diff --git a/include/net/af_rxrpc.h b/include/net/af_rxrpc.h
new file mode 100644
index 000000000..0fb4c41c9
--- /dev/null
+++ b/include/net/af_rxrpc.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* RxRPC kernel service interface definitions
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _NET_RXRPC_H
+#define _NET_RXRPC_H
+
+#include <linux/rxrpc.h>
+#include <linux/ktime.h>
+
+struct key;
+struct sock;
+struct socket;
+struct rxrpc_call;
+struct rxrpc_peer;
+struct krb5_buffer;
+enum rxrpc_abort_reason;
+
+enum rxrpc_interruptibility {
+	RXRPC_INTERRUPTIBLE,	/* Call is interruptible */
+	RXRPC_PREINTERRUPTIBLE,	/* Call can be cancelled whilst waiting for a slot */
+	RXRPC_UNINTERRUPTIBLE,	/* Call should not be interruptible at all */
+};
+
+enum rxrpc_oob_type {
+	RXRPC_OOB_CHALLENGE,	/* Security challenge for a connection */
+};
+
+/*
+ * Debug ID counter for tracing.
+ */
+extern atomic_t rxrpc_debug_id;
+
+/*
+ * Operations table for rxrpc to call out to a kernel application (e.g. kAFS).
+ */
+struct rxrpc_kernel_ops {
+	void (*notify_new_call)(struct sock *sk, struct rxrpc_call *call,
+				unsigned long user_call_ID);
+	void (*discard_new_call)(struct rxrpc_call *call, unsigned long user_call_ID);
+	void (*user_attach_call)(struct rxrpc_call *call, unsigned long user_call_ID);
+	void (*notify_oob)(struct sock *sk, struct sk_buff *oob);
+};
+
+typedef void (*rxrpc_notify_rx_t)(struct sock *, struct rxrpc_call *,
+				  unsigned long);
+typedef void (*rxrpc_notify_end_tx_t)(struct sock *, struct rxrpc_call *,
+				      unsigned long);
+
+void rxrpc_kernel_set_notifications(struct socket *sock,
+				    const struct rxrpc_kernel_ops *app_ops);
+struct rxrpc_call *rxrpc_kernel_begin_call(struct socket *sock,
+					   struct rxrpc_peer *peer,
+					   struct key *key,
+					   unsigned long user_call_ID,
+					   s64 tx_total_len,
+					   u32 hard_timeout,
+					   gfp_t gfp,
+					   rxrpc_notify_rx_t notify_rx,
+					   u16 service_id,
+					   bool upgrade,
+					   enum rxrpc_interruptibility interruptibility,
+					   unsigned int debug_id);
+int rxrpc_kernel_send_data(struct socket *, struct rxrpc_call *,
+			   struct msghdr *, size_t,
+			   rxrpc_notify_end_tx_t);
+int rxrpc_kernel_recv_data(struct socket *, struct rxrpc_call *,
+			   struct iov_iter *, size_t *, bool, u32 *, u16 *);
+bool rxrpc_kernel_abort_call(struct socket *, struct rxrpc_call *,
+			     u32, int, enum rxrpc_abort_reason);
+void rxrpc_kernel_shutdown_call(struct socket *sock, struct rxrpc_call *call);
+void rxrpc_kernel_put_call(struct socket *sock, struct rxrpc_call *call);
+struct rxrpc_peer *rxrpc_kernel_lookup_peer(struct socket *sock,
+					    struct sockaddr_rxrpc *srx, gfp_t gfp);
+void rxrpc_kernel_put_peer(struct rxrpc_peer *peer);
+struct rxrpc_peer *rxrpc_kernel_get_peer(struct rxrpc_peer *peer);
+struct rxrpc_peer *rxrpc_kernel_get_call_peer(struct socket *sock, struct rxrpc_call *call);
+const struct sockaddr_rxrpc *rxrpc_kernel_remote_srx(const struct rxrpc_peer *peer);
+const struct sockaddr *rxrpc_kernel_remote_addr(const struct rxrpc_peer *peer);
+unsigned long rxrpc_kernel_set_peer_data(struct rxrpc_peer *peer, unsigned long app_data);
+unsigned long rxrpc_kernel_get_peer_data(const struct rxrpc_peer *peer);
+unsigned int rxrpc_kernel_get_srtt(const struct rxrpc_peer *);
+int rxrpc_kernel_charge_accept(struct socket *sock, rxrpc_notify_rx_t notify_rx,
+			       unsigned long user_call_ID, gfp_t gfp,
+			       unsigned int debug_id);
+void rxrpc_kernel_set_tx_length(struct socket *, struct rxrpc_call *, s64);
+bool rxrpc_kernel_check_life(const struct socket *, const struct rxrpc_call *);
+
+int rxrpc_sock_set_min_security_level(struct sock *sk, unsigned int val);
+int rxrpc_sock_set_security_keyring(struct sock *, struct key *);
+int rxrpc_sock_set_manage_response(struct sock *sk, bool set);
+
+enum rxrpc_oob_type rxrpc_kernel_query_oob(struct sk_buff *oob,
+					   struct rxrpc_peer **_peer,
+					   unsigned long *_peer_appdata);
+struct sk_buff *rxrpc_kernel_dequeue_oob(struct socket *sock,
+					 enum rxrpc_oob_type *_type);
+void rxrpc_kernel_free_oob(struct sk_buff *oob);
+void rxrpc_kernel_query_challenge(struct sk_buff *challenge,
+				  struct rxrpc_peer **_peer,
+				  unsigned long *_peer_appdata,
+				  u16 *_service_id, u8 *_security_index);
+int rxrpc_kernel_reject_challenge(struct sk_buff *challenge, u32 abort_code,
+				  int error, enum rxrpc_abort_reason why);
+int rxkad_kernel_respond_to_challenge(struct sk_buff *challenge);
+u32 rxgk_kernel_query_challenge(struct sk_buff *challenge);
+int rxgk_kernel_respond_to_challenge(struct sk_buff *challenge,
+				     struct krb5_buffer *appdata);
+u8 rxrpc_kernel_query_call_security(struct rxrpc_call *call,
+				    u16 *_service_id, u32 *_enctype);
+
+#endif /* _NET_RXRPC_H */