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, 159 insertions, 0 deletions

diff --git a/include/net/phonet/pep.h b/include/net/phonet/pep.h
new file mode 100644
index 000000000..645dddf5c
--- /dev/null
+++ b/include/net/phonet/pep.h
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * File: pep.h
+ *
+ * Phonet Pipe End Point sockets definitions
+ *
+ * Copyright (C) 2008 Nokia Corporation.
+ */
+
+#ifndef NET_PHONET_PEP_H
+#define NET_PHONET_PEP_H
+
+#include <linux/skbuff.h>
+#include <net/phonet/phonet.h>
+
+struct pep_sock {
+	struct pn_sock		pn_sk;
+
+	/* XXX: union-ify listening vs connected stuff ? */
+	/* Listening socket stuff: */
+	struct hlist_head	hlist;
+
+	/* Connected socket stuff: */
+	struct sock		*listener;
+	struct sk_buff_head	ctrlreq_queue;
+#define PNPIPE_CTRLREQ_MAX	10
+	atomic_t		tx_credits;
+	int			ifindex;
+	u16			peer_type;	/* peer type/subtype */
+	u8			pipe_handle;
+
+	u8			rx_credits;
+	u8			rx_fc;	/* RX flow control */
+	u8			tx_fc;	/* TX flow control */
+	u8			init_enable;	/* auto-enable at creation */
+	u8			aligned;
+};
+
+static inline struct pep_sock *pep_sk(struct sock *sk)
+{
+	return (struct pep_sock *)sk;
+}
+
+extern const struct proto_ops phonet_stream_ops;
+
+/* Pipe protocol definitions */
+struct pnpipehdr {
+	u8			utid; /* transaction ID */
+	u8			message_id;
+	u8			pipe_handle;
+	union {
+		u8		state_after_connect;	/* connect request */
+		u8		state_after_reset;	/* reset request */
+		u8		error_code;		/* any response */
+		u8		pep_type;		/* status indication */
+		u8		data0;			/* anything else */
+	};
+	u8			data[];
+};
+#define other_pep_type		data[0]
+
+static inline struct pnpipehdr *pnp_hdr(struct sk_buff *skb)
+{
+	return (struct pnpipehdr *)skb_transport_header(skb);
+}
+
+#define MAX_PNPIPE_HEADER (MAX_PHONET_HEADER + 4)
+
+enum {
+	PNS_PIPE_CREATE_REQ = 0x00,
+	PNS_PIPE_CREATE_RESP,
+	PNS_PIPE_REMOVE_REQ,
+	PNS_PIPE_REMOVE_RESP,
+
+	PNS_PIPE_DATA = 0x20,
+	PNS_PIPE_ALIGNED_DATA,
+
+	PNS_PEP_CONNECT_REQ = 0x40,
+	PNS_PEP_CONNECT_RESP,
+	PNS_PEP_DISCONNECT_REQ,
+	PNS_PEP_DISCONNECT_RESP,
+	PNS_PEP_RESET_REQ,
+	PNS_PEP_RESET_RESP,
+	PNS_PEP_ENABLE_REQ,
+	PNS_PEP_ENABLE_RESP,
+	PNS_PEP_CTRL_REQ,
+	PNS_PEP_CTRL_RESP,
+	PNS_PEP_DISABLE_REQ = 0x4C,
+	PNS_PEP_DISABLE_RESP,
+
+	PNS_PEP_STATUS_IND = 0x60,
+	PNS_PIPE_CREATED_IND,
+	PNS_PIPE_RESET_IND = 0x63,
+	PNS_PIPE_ENABLED_IND,
+	PNS_PIPE_REDIRECTED_IND,
+	PNS_PIPE_DISABLED_IND = 0x66,
+};
+
+#define PN_PIPE_INVALID_HANDLE	0xff
+#define PN_PEP_TYPE_COMMON	0x00
+
+/* Phonet pipe status indication */
+enum {
+	PN_PEP_IND_FLOW_CONTROL,
+	PN_PEP_IND_ID_MCFC_GRANT_CREDITS,
+};
+
+/* Phonet pipe error codes */
+enum {
+	PN_PIPE_NO_ERROR,
+	PN_PIPE_ERR_INVALID_PARAM,
+	PN_PIPE_ERR_INVALID_HANDLE,
+	PN_PIPE_ERR_INVALID_CTRL_ID,
+	PN_PIPE_ERR_NOT_ALLOWED,
+	PN_PIPE_ERR_PEP_IN_USE,
+	PN_PIPE_ERR_OVERLOAD,
+	PN_PIPE_ERR_DEV_DISCONNECTED,
+	PN_PIPE_ERR_TIMEOUT,
+	PN_PIPE_ERR_ALL_PIPES_IN_USE,
+	PN_PIPE_ERR_GENERAL,
+	PN_PIPE_ERR_NOT_SUPPORTED,
+};
+
+/* Phonet pipe states */
+enum {
+	PN_PIPE_DISABLE,
+	PN_PIPE_ENABLE,
+};
+
+/* Phonet pipe sub-block types */
+enum {
+	PN_PIPE_SB_CREATE_REQ_PEP_SUB_TYPE,
+	PN_PIPE_SB_CONNECT_REQ_PEP_SUB_TYPE,
+	PN_PIPE_SB_REDIRECT_REQ_PEP_SUB_TYPE,
+	PN_PIPE_SB_NEGOTIATED_FC,
+	PN_PIPE_SB_REQUIRED_FC_TX,
+	PN_PIPE_SB_PREFERRED_FC_RX,
+	PN_PIPE_SB_ALIGNED_DATA,
+};
+
+/* Phonet pipe flow control models */
+enum {
+	PN_NO_FLOW_CONTROL,
+	PN_LEGACY_FLOW_CONTROL,
+	PN_ONE_CREDIT_FLOW_CONTROL,
+	PN_MULTI_CREDIT_FLOW_CONTROL,
+	PN_MAX_FLOW_CONTROL,
+};
+
+#define pn_flow_safe(fc) ((fc) >> 1)
+
+/* Phonet pipe flow control states */
+enum {
+	PEP_IND_EMPTY,
+	PEP_IND_BUSY,
+	PEP_IND_READY,
+};
+
+#endif