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, 33 insertions, 0 deletions

diff --git a/fs/nfs/sysfs.h b/fs/nfs/sysfs.h
new file mode 100644
index 000000000..c5d1990ca
--- /dev/null
+++ b/fs/nfs/sysfs.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2019 Hammerspace Inc
+ */
+
+#ifndef __NFS_SYSFS_H
+#define __NFS_SYSFS_H
+
+#define CONTAINER_ID_MAXLEN (64)
+
+struct nfs_netns_client {
+	struct kobject kobject;
+	struct kobject nfs_net_kobj;
+	struct net *net;
+	const char __rcu *identifier;
+};
+
+extern struct kobject *nfs_net_kobj;
+
+extern int nfs_sysfs_init(void);
+extern void nfs_sysfs_exit(void);
+
+void nfs_netns_sysfs_setup(struct nfs_net *netns, struct net *net);
+void nfs_netns_sysfs_destroy(struct nfs_net *netns);
+
+void nfs_sysfs_link_rpc_client(struct nfs_server *server,
+			struct rpc_clnt *clnt, const char *sysfs_prefix);
+void nfs_sysfs_add_server(struct nfs_server *s);
+void nfs_sysfs_move_server_to_sb(struct super_block *s);
+void nfs_sysfs_move_sb_to_server(struct nfs_server *s);
+void nfs_sysfs_remove_server(struct nfs_server *s);
+
+#endif