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, 66 insertions, 0 deletions

diff --git a/fs/smb/server/misc.h b/fs/smb/server/misc.h
new file mode 100644
index 000000000..3909104e1
--- /dev/null
+++ b/fs/smb/server/misc.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
+ */
+
+#ifndef __KSMBD_MISC_H__
+#define __KSMBD_MISC_H__
+
+#ifdef CONFIG_PROC_FS
+#include <linux/proc_fs.h>
+#endif
+struct ksmbd_share_config;
+struct nls_table;
+struct kstat;
+struct ksmbd_file;
+
+int match_pattern(const char *str, size_t len, const char *pattern);
+int ksmbd_validate_filename(char *filename);
+int parse_stream_name(char *filename, char **stream_name, int *s_type);
+char *convert_to_nt_pathname(struct ksmbd_share_config *share,
+			     const struct path *path);
+int get_nlink(struct kstat *st);
+void ksmbd_conv_path_to_unix(char *path);
+void ksmbd_strip_last_slash(char *path);
+void ksmbd_conv_path_to_windows(char *path);
+char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name);
+char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename);
+
+#define KSMBD_DIR_INFO_ALIGNMENT	8
+struct ksmbd_dir_info;
+char *ksmbd_convert_dir_info_name(struct ksmbd_dir_info *d_info,
+				  const struct nls_table *local_nls,
+				  int *conv_len);
+
+#define NTFS_TIME_OFFSET	((u64)(369 * 365 + 89) * 24 * 3600 * 10000000)
+struct timespec64 ksmbd_NTtimeToUnix(__le64 ntutc);
+u64 ksmbd_UnixTimeToNT(struct timespec64 t);
+long long ksmbd_systime(void);
+
+#ifdef CONFIG_PROC_FS
+struct ksmbd_const_name {
+	unsigned int const_value;
+	const char *name;
+};
+
+void ksmbd_proc_init(void);
+void ksmbd_proc_cleanup(void);
+void ksmbd_proc_reset(void);
+struct proc_dir_entry *ksmbd_proc_create(const char *name,
+					 int (*show)(struct seq_file *m, void *v),
+			     void *v);
+void ksmbd_proc_show_flag_names(struct seq_file *m,
+				const struct ksmbd_const_name *table,
+				int count,
+				unsigned int flags);
+void ksmbd_proc_show_const_name(struct seq_file *m,
+				const char *format,
+				const struct ksmbd_const_name *table,
+				int count,
+				unsigned int const_value);
+#else
+static inline void ksmbd_proc_init(void) {}
+static inline void ksmbd_proc_cleanup(void) {}
+static inline void ksmbd_proc_reset(void) {}
+#endif
+#endif /* __KSMBD_MISC_H__ */