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, 49 insertions, 0 deletions

diff --git a/fs/smb/server/glob.h b/fs/smb/server/glob.h
new file mode 100644
index 000000000..4ea187af2
--- /dev/null
+++ b/fs/smb/server/glob.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *   Copyright (C) 2016 Namjae Jeon <linkinjeon@kernel.org>
+ *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
+ */
+
+#ifndef __KSMBD_GLOB_H
+#define __KSMBD_GLOB_H
+
+#include <linux/ctype.h>
+
+#include "unicode.h"
+#include "vfs_cache.h"
+
+extern int ksmbd_debug_types;
+
+#define KSMBD_DEBUG_SMB		BIT(0)
+#define KSMBD_DEBUG_AUTH	BIT(1)
+#define KSMBD_DEBUG_VFS		BIT(2)
+#define KSMBD_DEBUG_OPLOCK      BIT(3)
+#define KSMBD_DEBUG_IPC         BIT(4)
+#define KSMBD_DEBUG_CONN        BIT(5)
+#define KSMBD_DEBUG_RDMA        BIT(6)
+#define KSMBD_DEBUG_ALL         (KSMBD_DEBUG_SMB | KSMBD_DEBUG_AUTH |	\
+				KSMBD_DEBUG_VFS | KSMBD_DEBUG_OPLOCK |	\
+				KSMBD_DEBUG_IPC | KSMBD_DEBUG_CONN |	\
+				KSMBD_DEBUG_RDMA)
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#ifdef SUBMOD_NAME
+#define pr_fmt(fmt)	"ksmbd: " SUBMOD_NAME ": " fmt
+#else
+#define pr_fmt(fmt)	"ksmbd: " fmt
+#endif
+
+#define ksmbd_debug(type, fmt, ...)				\
+	do {							\
+		if (ksmbd_debug_types & KSMBD_DEBUG_##type)	\
+			pr_info(fmt, ##__VA_ARGS__);		\
+	} while (0)
+
+#define UNICODE_LEN(x)		((x) * 2)
+
+#define KSMBD_DEFAULT_GFP	(GFP_KERNEL | __GFP_RETRY_MAYFAIL)
+
+#endif /* __KSMBD_GLOB_H */