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, 100 insertions, 0 deletions

diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
new file mode 100644
index 000000000..ab74b5ed0
--- /dev/null
+++ b/include/net/netns/conntrack.h
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NETNS_CONNTRACK_H
+#define __NETNS_CONNTRACK_H
+
+#include <linux/list.h>
+#include <linux/list_nulls.h>
+#include <linux/atomic.h>
+#include <linux/workqueue.h>
+#include <linux/netfilter/nf_conntrack_tcp.h>
+#ifdef CONFIG_NF_CT_PROTO_SCTP
+#include <linux/netfilter/nf_conntrack_sctp.h>
+#endif
+#include <linux/seqlock.h>
+
+struct ctl_table_header;
+struct nf_conntrack_ecache;
+
+struct nf_generic_net {
+	unsigned int timeout;
+};
+
+struct nf_tcp_net {
+	unsigned int timeouts[TCP_CONNTRACK_TIMEOUT_MAX];
+	u8 tcp_loose;
+	u8 tcp_be_liberal;
+	u8 tcp_max_retrans;
+	u8 tcp_ignore_invalid_rst;
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	unsigned int offload_timeout;
+#endif
+};
+
+enum udp_conntrack {
+	UDP_CT_UNREPLIED,
+	UDP_CT_REPLIED,
+	UDP_CT_MAX
+};
+
+struct nf_udp_net {
+	unsigned int timeouts[UDP_CT_MAX];
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	unsigned int offload_timeout;
+#endif
+};
+
+struct nf_icmp_net {
+	unsigned int timeout;
+};
+
+#ifdef CONFIG_NF_CT_PROTO_SCTP
+struct nf_sctp_net {
+	unsigned int timeouts[SCTP_CONNTRACK_MAX];
+};
+#endif
+
+#ifdef CONFIG_NF_CT_PROTO_GRE
+enum gre_conntrack {
+	GRE_CT_UNREPLIED,
+	GRE_CT_REPLIED,
+	GRE_CT_MAX
+};
+
+struct nf_gre_net {
+	struct list_head	keymap_list;
+	unsigned int		timeouts[GRE_CT_MAX];
+};
+#endif
+
+struct nf_ip_net {
+	struct nf_generic_net   generic;
+	struct nf_tcp_net	tcp;
+	struct nf_udp_net	udp;
+	struct nf_icmp_net	icmp;
+	struct nf_icmp_net	icmpv6;
+#ifdef CONFIG_NF_CT_PROTO_SCTP
+	struct nf_sctp_net	sctp;
+#endif
+#ifdef CONFIG_NF_CT_PROTO_GRE
+	struct nf_gre_net	gre;
+#endif
+};
+
+struct netns_ct {
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+	bool ecache_dwork_pending;
+#endif
+	u8			sysctl_log_invalid; /* Log invalid packets */
+	u8			sysctl_events;
+	u8			sysctl_acct;
+	u8			sysctl_tstamp;
+	u8			sysctl_checksum;
+
+	struct ip_conntrack_stat __percpu *stat;
+	struct nf_ct_event_notifier __rcu *nf_conntrack_event_cb;
+	struct nf_ip_net	nf_ct_proto;
+#if defined(CONFIG_NF_CONNTRACK_LABELS)
+	atomic_t		labels_used;
+#endif
+};
+#endif