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, 25 insertions, 0 deletions

diff --git a/fs/lockd/netns.h b/fs/lockd/netns.h
new file mode 100644
index 000000000..88e8e2a97
--- /dev/null
+++ b/fs/lockd/netns.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LOCKD_NETNS_H__
+#define __LOCKD_NETNS_H__
+
+#include <linux/fs.h>
+#include <linux/filelock.h>
+#include <net/netns/generic.h>
+
+struct lockd_net {
+	unsigned int nlmsvc_users;
+	unsigned long next_gc;
+	unsigned long nrhosts;
+	u32 gracetime;
+	u16 tcp_port;
+	u16 udp_port;
+
+	struct delayed_work grace_period_end;
+	struct lock_manager lockd_manager;
+
+	struct list_head nsm_handles;
+};
+
+extern unsigned int lockd_net_id;
+
+#endif