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, 158 insertions, 0 deletions

diff --git a/fs/ntfs/object_id.c b/fs/ntfs/object_id.c
new file mode 100644
index 000000000..89002c375
--- /dev/null
+++ b/fs/ntfs/object_id.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Pocessing of object ids
+ *
+ * Part of this file is based on code from the NTFS-3G.
+ *
+ * Copyright (c) 2009-2019 Jean-Pierre Andre
+ * Copyright (c) 2026 LG Electronics Co., Ltd.
+ */
+
+#include "ntfs.h"
+#include "index.h"
+#include "object_id.h"
+
+struct object_id_index_key {
+	union {
+		u32 alignment;
+		struct guid guid;
+	} object_id;
+} __packed;
+
+struct object_id_index_data {
+	__le64 file_id;
+	struct guid birth_volume_id;
+	struct guid birth_object_id;
+	struct guid domain_id;
+} __packed;
+
+/* Index entry in $Extend/$ObjId */
+struct object_id_index {
+	struct index_entry_header header;
+	struct object_id_index_key key;
+	struct object_id_index_data data;
+} __packed;
+
+__le16 objid_index_name[] = {cpu_to_le16('$'), cpu_to_le16('O'), 0};
+
+/*
+ * open_object_id_index - Open the $Extend/$ObjId file and its index
+ * @vol: NTFS volume structure
+ *
+ * Opens the $ObjId system file and retrieves its index context.
+ *
+ * Return: The index context if opened successfully, or NULL if an error
+ *	   occurred.
+ */
+static struct ntfs_index_context *open_object_id_index(struct ntfs_volume *vol)
+{
+	struct inode *dir_vi, *vi;
+	struct ntfs_inode *dir_ni;
+	struct ntfs_index_context *xo = NULL;
+	struct ntfs_name *name = NULL;
+	u64 mref;
+	int uname_len;
+	__le16 *uname;
+
+	uname_len = ntfs_nlstoucs(vol, "$ObjId", 6, &uname,
+			NTFS_MAX_NAME_LEN);
+	if (uname_len < 0)
+		return NULL;
+
+	/* do not use path_name_to inode - could reopen root */
+	dir_vi = ntfs_iget(vol->sb, FILE_Extend);
+	if (IS_ERR(dir_vi)) {
+		kmem_cache_free(ntfs_name_cache, uname);
+		return NULL;
+	}
+	dir_ni = NTFS_I(dir_vi);
+
+	mutex_lock_nested(&dir_ni->mrec_lock, NTFS_EXTEND_MUTEX_PARENT);
+	mref = ntfs_lookup_inode_by_name(dir_ni, uname, uname_len, &name);
+	mutex_unlock(&dir_ni->mrec_lock);
+	kfree(name);
+	kmem_cache_free(ntfs_name_cache, uname);
+	if (IS_ERR_MREF(mref))
+		goto put_dir_vi;
+
+	vi = ntfs_iget(vol->sb, MREF(mref));
+	if (IS_ERR(vi))
+		goto put_dir_vi;
+
+	xo = ntfs_index_ctx_get(NTFS_I(vi), objid_index_name, 2);
+	if (!xo)
+		iput(vi);
+put_dir_vi:
+	iput(dir_vi);
+	return xo;
+}
+
+
+/*
+ * remove_object_id_index - Remove an object id index entry if attribute present
+ * @ni: NTFS inode structure containing the attribute
+ * @xo:	Index context for the object id index
+ *
+ * Reads the existing object ID attribute and removes it from the index.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+static int remove_object_id_index(struct ntfs_inode *ni, struct ntfs_index_context *xo)
+{
+	struct object_id_index_key key = {0};
+	s64 size;
+
+	if (ni->data_size == 0)
+		return -ENODATA;
+
+	/* read the existing object id attribute */
+	size = ntfs_inode_attr_pread(VFS_I(ni), 0, sizeof(struct guid),
+				     (char *)&key);
+	if (size != sizeof(struct guid))
+		return -ENODATA;
+
+	if (!ntfs_index_lookup(&key, sizeof(struct object_id_index_key), xo))
+		return ntfs_index_rm(xo);
+
+	return 0;
+}
+
+/*
+ * ntfs_delete_object_id_index - Delete an object_id index entry
+ * @ni:	NTFS inode structure
+ *
+ * Opens the object ID index and removes the entry corresponding to the inode.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+int ntfs_delete_object_id_index(struct ntfs_inode *ni)
+{
+	struct ntfs_index_context *xo;
+	struct ntfs_inode *xoni;
+	struct inode *attr_vi;
+	int ret = 0;
+
+	attr_vi = ntfs_attr_iget(VFS_I(ni), AT_OBJECT_ID, AT_UNNAMED, 0);
+	if (IS_ERR(attr_vi))
+		return PTR_ERR(attr_vi);
+
+	/*
+	 * read the existing object id and un-index it
+	 */
+	xo = open_object_id_index(ni->vol);
+	if (xo) {
+		xoni = xo->idx_ni;
+		mutex_lock_nested(&xoni->mrec_lock, NTFS_EXTEND_MUTEX_PARENT);
+		ret = remove_object_id_index(NTFS_I(attr_vi), xo);
+		if (!ret) {
+			ntfs_index_entry_mark_dirty(xo);
+			mark_mft_record_dirty(xoni);
+		}
+		ntfs_index_ctx_put(xo);
+		mutex_unlock(&xoni->mrec_lock);
+		iput(VFS_I(xoni));
+	}
+
+	iput(attr_vi);
+	return ret;
+}