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, 179 insertions, 0 deletions

diff --git a/fs/afs/protocol_yfs.h b/fs/afs/protocol_yfs.h
new file mode 100644
index 000000000..b2f06c191
--- /dev/null
+++ b/fs/afs/protocol_yfs.h
@@ -0,0 +1,179 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* YFS protocol bits
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define YFS_FS_SERVICE	2500
+#define YFS_CM_SERVICE	2501
+
+#define YFSCBMAX	1024
+
+enum YFS_CM_Operations {
+	YFSCBProbe		= 206,	/* probe client */
+	YFSCBGetLock		= 207,	/* get contents of CM lock table */
+	YFSCBXStatsVersion	= 209,	/* get version of extended statistics */
+	YFSCBGetXStats		= 210,	/* get contents of extended statistics data */
+	YFSCBInitCallBackState3	= 213,	/* initialise callback state, version 3 */
+	YFSCBProbeUuid		= 214,	/* check the client hasn't rebooted */
+	YFSCBGetServerPrefs	= 215,
+	YFSCBGetCellServDV	= 216,
+	YFSCBGetLocalCell	= 217,
+	YFSCBGetCacheConfig	= 218,
+	YFSCBGetCellByNum	= 65537,
+	YFSCBTellMeAboutYourself = 65538, /* get client capabilities */
+	YFSCBCallBack		= 64204,
+};
+
+enum YFS_FS_Operations {
+	YFSFETCHACL		= 64131, /* YFS Fetch file AFS3 ACL */
+	YFSFETCHSTATUS		= 64132, /* YFS Fetch file status */
+	YFSSTOREACL		= 64134, /* YFS Store file AFS3 ACL */
+	YFSSTORESTATUS		= 64135, /* YFS Store file status */
+	YFSREMOVEFILE		= 64136, /* YFS Remove a file */
+	YFSCREATEFILE		= 64137, /* YFS Create a file */
+	YFSRENAME		= 64138, /* YFS Rename or move a file or directory */
+	YFSSYMLINK		= 64139, /* YFS Create a symbolic link */
+	YFSLINK			= 64140, /* YFS Create a hard link */
+	YFSMAKEDIR		= 64141, /* YFS Create a directory */
+	YFSREMOVEDIR		= 64142, /* YFS Remove a directory */
+	YFSGETVOLUMESTATUS	= 64149, /* YFS Get volume status information */
+	YFSSETVOLUMESTATUS	= 64150, /* YFS Set volume status information */
+	YFSSETLOCK		= 64156, /* YFS Request a file lock */
+	YFSEXTENDLOCK		= 64157, /* YFS Extend a file lock */
+	YFSRELEASELOCK		= 64158, /* YFS Release a file lock */
+	YFSLOOKUP		= 64161, /* YFS lookup file in directory */
+	YFSFLUSHCPS		= 64165,
+	YFSFETCHOPAQUEACL	= 64168, /* YFS Fetch file YFS ACL */
+	YFSWHOAMI		= 64170,
+	YFSREMOVEACL		= 64171,
+	YFSREMOVEFILE2		= 64173,
+	YFSSTOREOPAQUEACL2	= 64174,
+	YFSRENAME_REPLACE	= 64176,
+	YFSRENAME_NOREPLACE	= 64177,
+	YFSRENAME_EXCHANGE	= 64187,
+	YFSINLINEBULKSTATUS	= 64536, /* YFS Fetch multiple file statuses with errors */
+	YFSFETCHDATA64		= 64537, /* YFS Fetch file data */
+	YFSSTOREDATA64		= 64538, /* YFS Store file data */
+	YFSUPDATESYMLINK	= 64540,
+};
+
+struct yfs_xdr_u64 {
+	__be32			msw;
+	__be32			lsw;
+} __packed;
+
+static inline u64 xdr_to_u64(const struct yfs_xdr_u64 x)
+{
+	return ((u64)ntohl(x.msw) << 32) | ntohl(x.lsw);
+}
+
+static inline struct yfs_xdr_u64 u64_to_xdr(const u64 x)
+{
+	return (struct yfs_xdr_u64){ .msw = htonl(x >> 32), .lsw = htonl(x) };
+}
+
+struct yfs_xdr_vnode {
+	struct yfs_xdr_u64	lo;
+	__be32			hi;
+	__be32			unique;
+} __packed;
+
+struct yfs_xdr_YFSFid {
+	struct yfs_xdr_u64	volume;
+	struct yfs_xdr_vnode	vnode;
+} __packed;
+
+
+struct yfs_xdr_YFSFetchStatus {
+	__be32			type;
+	__be32			nlink;
+	struct yfs_xdr_u64	size;
+	struct yfs_xdr_u64	data_version;
+	struct yfs_xdr_u64	author;
+	struct yfs_xdr_u64	owner;
+	struct yfs_xdr_u64	group;
+	__be32			mode;
+	__be32			caller_access;
+	__be32			anon_access;
+	struct yfs_xdr_vnode	parent;
+	__be32			data_access_protocol;
+	struct yfs_xdr_u64	mtime_client;
+	struct yfs_xdr_u64	mtime_server;
+	__be32			lock_count;
+	__be32			abort_code;
+} __packed;
+
+struct yfs_xdr_YFSCallBack {
+	__be32			version;
+	struct yfs_xdr_u64	expiration_time;
+	__be32			type;
+} __packed;
+
+struct yfs_xdr_YFSStoreStatus {
+	__be32			mask;
+	__be32			mode;
+	struct yfs_xdr_u64	mtime_client;
+	struct yfs_xdr_u64	owner;
+	struct yfs_xdr_u64	group;
+} __packed;
+
+struct yfs_xdr_RPCFlags {
+	__be32			rpc_flags;
+} __packed;
+
+struct yfs_xdr_YFSVolSync {
+	struct yfs_xdr_u64	vol_creation_date;
+	struct yfs_xdr_u64	vol_update_date;
+	struct yfs_xdr_u64	max_quota;
+	struct yfs_xdr_u64	blocks_in_use;
+	struct yfs_xdr_u64	blocks_avail;
+} __packed;
+
+enum yfs_volume_type {
+	yfs_volume_type_ro = 0,
+	yfs_volume_type_rw = 1,
+};
+
+#define yfs_FVSOnline		0x1
+#define yfs_FVSInservice	0x2
+#define yfs_FVSBlessed		0x4
+#define yfs_FVSNeedsSalvage	0x8
+
+struct yfs_xdr_YFSFetchVolumeStatus {
+	struct yfs_xdr_u64	vid;
+	struct yfs_xdr_u64	parent_id;
+	__be32			flags;
+	__be32			type;
+	struct yfs_xdr_u64	max_quota;
+	struct yfs_xdr_u64	blocks_in_use;
+	struct yfs_xdr_u64	part_blocks_avail;
+	struct yfs_xdr_u64	part_max_blocks;
+	struct yfs_xdr_u64	vol_copy_date;
+	struct yfs_xdr_u64	vol_backup_date;
+} __packed;
+
+struct yfs_xdr_YFSStoreVolumeStatus {
+	__be32			mask;
+	struct yfs_xdr_u64	min_quota;
+	struct yfs_xdr_u64	max_quota;
+	struct yfs_xdr_u64	file_quota;
+} __packed;
+
+enum yfs_lock_type {
+	yfs_LockNone		= -1,
+	yfs_LockRead		= 0,
+	yfs_LockWrite		= 1,
+	yfs_LockExtend		= 2,
+	yfs_LockRelease		= 3,
+	yfs_LockMandatoryRead	= 0x100,
+	yfs_LockMandatoryWrite	= 0x101,
+	yfs_LockMandatoryExtend	= 0x102,
+};
+
+/* RXYFS Viced Capability Flags */
+#define YFS_VICED_CAPABILITY_ERRORTRANS		0x0001 /* Deprecated v0.195 */
+#define YFS_VICED_CAPABILITY_64BITFILES		0x0002 /* Deprecated v0.195 */
+#define YFS_VICED_CAPABILITY_WRITELOCKACL	0x0004 /* Can lock a file even without lock perm */
+#define YFS_VICED_CAPABILITY_SANEACLS		0x0008 /* Deprecated v0.195 */