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, 62 insertions, 0 deletions

diff --git a/drivers/net/wireguard/device.h b/drivers/net/wireguard/device.h
new file mode 100644
index 000000000..43c7cebbf
--- /dev/null
+++ b/drivers/net/wireguard/device.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef _WG_DEVICE_H
+#define _WG_DEVICE_H
+
+#include "noise.h"
+#include "allowedips.h"
+#include "peerlookup.h"
+#include "cookie.h"
+
+#include <linux/types.h>
+#include <linux/netdevice.h>
+#include <linux/workqueue.h>
+#include <linux/mutex.h>
+#include <linux/net.h>
+#include <linux/ptr_ring.h>
+
+struct wg_device;
+
+struct multicore_worker {
+	void *ptr;
+	struct work_struct work;
+};
+
+struct crypt_queue {
+	struct ptr_ring ring;
+	struct multicore_worker __percpu *worker;
+	int last_cpu;
+};
+
+struct prev_queue {
+	struct sk_buff *head, *tail, *peeked;
+	struct { struct sk_buff *next, *prev; } empty; // Match first 2 members of struct sk_buff.
+	atomic_t count;
+};
+
+struct wg_device {
+	struct net_device *dev;
+	struct crypt_queue encrypt_queue, decrypt_queue, handshake_queue;
+	struct sock __rcu *sock4, *sock6;
+	struct net __rcu *creating_net;
+	struct noise_static_identity static_identity;
+	struct workqueue_struct *packet_crypt_wq,*handshake_receive_wq, *handshake_send_wq;
+	struct cookie_checker cookie_checker;
+	struct pubkey_hashtable *peer_hashtable;
+	struct index_hashtable *index_hashtable;
+	struct allowedips peer_allowedips;
+	struct mutex device_update_lock, socket_update_lock;
+	struct list_head device_list, peer_list;
+	atomic_t handshake_queue_len;
+	unsigned int num_peers, device_update_gen;
+	u32 fwmark;
+	u16 incoming_port;
+};
+
+int wg_device_init(void);
+void wg_device_uninit(void);
+
+#endif /* _WG_DEVICE_H */