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, 89 insertions, 0 deletions

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
new file mode 100644
index 000000000..b73983a17
--- /dev/null
+++ b/include/net/netns/xfrm.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NETNS_XFRM_H
+#define __NETNS_XFRM_H
+
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/workqueue.h>
+#include <linux/rhashtable-types.h>
+#include <linux/xfrm.h>
+#include <net/dst_ops.h>
+
+struct ctl_table_header;
+
+struct xfrm_policy_hash {
+	struct hlist_head	__rcu *table;
+	unsigned int		hmask;
+	u8			dbits4;
+	u8			sbits4;
+	u8			dbits6;
+	u8			sbits6;
+};
+
+struct xfrm_policy_hthresh {
+	struct work_struct	work;
+	seqlock_t		lock;
+	u8			lbits4;
+	u8			rbits4;
+	u8			lbits6;
+	u8			rbits6;
+};
+
+struct netns_xfrm {
+	struct list_head	state_all;
+	/*
+	 * Hash table to find appropriate SA towards given target (endpoint of
+	 * tunnel or destination of transport mode) allowed by selector.
+	 *
+	 * Main use is finding SA after policy selected tunnel or transport
+	 * mode. Also, it can be used by ah/esp icmp error handler to find
+	 * offending SA.
+	 */
+	struct hlist_head	__rcu *state_bydst;
+	struct hlist_head	__rcu *state_bysrc;
+	struct hlist_head	__rcu *state_byspi;
+	struct hlist_head	__rcu *state_byseq;
+	struct hlist_head	 __percpu *state_cache_input;
+	unsigned int		state_hmask;
+	unsigned int		state_num;
+	struct work_struct	state_hash_work;
+
+	struct list_head	policy_all;
+	struct hlist_head	*policy_byidx;
+	unsigned int		policy_idx_hmask;
+	unsigned int		idx_generator;
+	struct xfrm_policy_hash	policy_bydst[XFRM_POLICY_MAX];
+	unsigned int		policy_count[XFRM_POLICY_MAX * 2];
+	struct work_struct	policy_hash_work;
+	struct xfrm_policy_hthresh policy_hthresh;
+	struct list_head	inexact_bins;
+
+
+	struct sock		__rcu *nlsk;
+	struct sock		*nlsk_stash;
+
+	u32			sysctl_aevent_etime;
+	u32			sysctl_aevent_rseqth;
+	int			sysctl_larval_drop;
+	u32			sysctl_acq_expires;
+
+	u8			policy_default[XFRM_POLICY_MAX];
+
+#ifdef CONFIG_SYSCTL
+	struct ctl_table_header	*sysctl_hdr;
+#endif
+
+	struct dst_ops		xfrm4_dst_ops;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct dst_ops		xfrm6_dst_ops;
+#endif
+	spinlock_t		xfrm_state_lock;
+	seqcount_spinlock_t	xfrm_state_hash_generation;
+	seqcount_spinlock_t	xfrm_policy_hash_generation;
+
+	spinlock_t xfrm_policy_lock;
+	struct mutex xfrm_cfg_mutex;
+	struct delayed_work	nat_keepalive_work;
+};
+
+#endif