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, 56 insertions, 0 deletions

diff --git a/fs/lockd/nlm.h b/fs/lockd/nlm.h
new file mode 100644
index 000000000..47be65d01
--- /dev/null
+++ b/fs/lockd/nlm.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Declarations for the Network Lock Manager protocol.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#ifndef _LOCKD_NLM_H
+#define _LOCKD_NLM_H
+
+
+/* Maximum file offset in file_lock.fl_end */
+# define NLM_OFFSET_MAX		((s32) 0x7fffffff)
+# define NLM4_OFFSET_MAX	((s64) ((~(u64)0) >> 1))
+
+/* Return states for NLM */
+enum {
+	NLM_LCK_GRANTED			= 0,
+	NLM_LCK_DENIED			= 1,
+	NLM_LCK_DENIED_NOLOCKS		= 2,
+	NLM_LCK_BLOCKED			= 3,
+	NLM_LCK_DENIED_GRACE_PERIOD	= 4,
+#ifdef CONFIG_LOCKD_V4
+	NLM_DEADLCK			= 5,
+	NLM_ROFS			= 6,
+	NLM_STALE_FH			= 7,
+	NLM_FBIG			= 8,
+	NLM_FAILED			= 9,
+#endif
+};
+
+#define NLM_PROGRAM		100021
+
+#define NLMPROC_NULL		0
+#define NLMPROC_TEST		1
+#define NLMPROC_LOCK		2
+#define NLMPROC_CANCEL		3
+#define NLMPROC_UNLOCK		4
+#define NLMPROC_GRANTED		5
+#define NLMPROC_TEST_MSG	6
+#define NLMPROC_LOCK_MSG	7
+#define NLMPROC_CANCEL_MSG	8
+#define NLMPROC_UNLOCK_MSG	9
+#define NLMPROC_GRANTED_MSG	10
+#define NLMPROC_TEST_RES	11
+#define NLMPROC_LOCK_RES	12
+#define NLMPROC_CANCEL_RES	13
+#define NLMPROC_UNLOCK_RES	14
+#define NLMPROC_GRANTED_RES	15
+#define NLMPROC_NSM_NOTIFY	16		/* statd callback */
+#define NLMPROC_SHARE		20
+#define NLMPROC_UNSHARE		21
+#define NLMPROC_NM_LOCK		22
+#define NLMPROC_FREE_ALL	23
+
+#endif /* _LOCKD_NLM_H */