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, 87 insertions, 0 deletions

diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
new file mode 100644
index 000000000..1d79a3b53
--- /dev/null
+++ b/include/scsi/scsi_devinfo.h
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCSI_SCSI_DEVINFO_H
+#define _SCSI_SCSI_DEVINFO_H
+/*
+ * Flags for SCSI devices that need special treatment
+ */
+
+/* Only scan LUN 0 */
+#define BLIST_NOLUN		((__force blist_flags_t)(1ULL << 0))
+/* Known to have LUNs, force scanning.
+ * DEPRECATED: Use max_luns=N */
+#define BLIST_FORCELUN		((__force blist_flags_t)(1ULL << 1))
+/* Flag for broken handshaking */
+#define BLIST_BORKEN		((__force blist_flags_t)(1ULL << 2))
+/* unlock by special command */
+#define BLIST_KEY		((__force blist_flags_t)(1ULL << 3))
+/* Do not use LUNs in parallel */
+#define BLIST_SINGLELUN		((__force blist_flags_t)(1ULL << 4))
+/* Buggy Tagged Command Queuing */
+#define BLIST_NOTQ		((__force blist_flags_t)(1ULL << 5))
+/* Non consecutive LUN numbering */
+#define BLIST_SPARSELUN		((__force blist_flags_t)(1ULL << 6))
+/* Avoid LUNS >= 5 */
+#define BLIST_MAX5LUN		((__force blist_flags_t)(1ULL << 7))
+/* Treat as (removable) CD-ROM */
+#define BLIST_ISROM		((__force blist_flags_t)(1ULL << 8))
+/* LUNs past 7 on a SCSI-2 device */
+#define BLIST_LARGELUN		((__force blist_flags_t)(1ULL << 9))
+/* override additional length field */
+#define BLIST_INQUIRY_36	((__force blist_flags_t)(1ULL << 10))
+/* ignore MEDIA CHANGE unit attention after resuming from runtime suspend */
+#define BLIST_IGN_MEDIA_CHANGE	((__force blist_flags_t)(1ULL << 11))
+/* do not do automatic start on add */
+#define BLIST_NOSTARTONADD	((__force blist_flags_t)(1ULL << 12))
+/* do not ask for VPD page size first on some broken targets */
+#define BLIST_NO_VPD_SIZE	((__force blist_flags_t)(1ULL << 13))
+#define __BLIST_UNUSED_14	((__force blist_flags_t)(1ULL << 14))
+#define __BLIST_UNUSED_15	((__force blist_flags_t)(1ULL << 15))
+#define __BLIST_UNUSED_16	((__force blist_flags_t)(1ULL << 16))
+/* try REPORT_LUNS even for SCSI-2 devs (if HBA supports more than 8 LUNs) */
+#define BLIST_REPORTLUN2	((__force blist_flags_t)(1ULL << 17))
+/* don't try REPORT_LUNS scan (SCSI-3 devs) */
+#define BLIST_NOREPORTLUN	((__force blist_flags_t)(1ULL << 18))
+/* don't use PREVENT-ALLOW commands */
+#define BLIST_NOT_LOCKABLE	((__force blist_flags_t)(1ULL << 19))
+/* device is actually for RAID config */
+#define BLIST_NO_ULD_ATTACH	((__force blist_flags_t)(1ULL << 20))
+/* select without ATN */
+#define BLIST_SELECT_NO_ATN	((__force blist_flags_t)(1ULL << 21))
+/* retry HARDWARE_ERROR */
+#define BLIST_RETRY_HWERROR	((__force blist_flags_t)(1ULL << 22))
+/* maximum 512 sector cdb length */
+#define BLIST_MAX_512		((__force blist_flags_t)(1ULL << 23))
+#define __BLIST_UNUSED_24	((__force blist_flags_t)(1ULL << 24))
+/* Disable T10 PI (DIF) */
+#define BLIST_NO_DIF		((__force blist_flags_t)(1ULL << 25))
+/* Ignore SBC-3 VPD pages */
+#define BLIST_SKIP_VPD_PAGES	((__force blist_flags_t)(1ULL << 26))
+#define __BLIST_UNUSED_27	((__force blist_flags_t)(1ULL << 27))
+/* Attempt to read VPD pages */
+#define BLIST_TRY_VPD_PAGES	((__force blist_flags_t)(1ULL << 28))
+/* don't try to issue RSOC */
+#define BLIST_NO_RSOC		((__force blist_flags_t)(1ULL << 29))
+/* maximum 1024 sector cdb length */
+#define BLIST_MAX_1024		((__force blist_flags_t)(1ULL << 30))
+/* Use UNMAP limit for WRITE SAME */
+#define BLIST_UNMAP_LIMIT_WS	((__force blist_flags_t)(1ULL << 31))
+/* Always retry ABORTED_COMMAND with Internal Target Failure */
+#define BLIST_RETRY_ITF		((__force blist_flags_t)(1ULL << 32))
+/* Always retry ABORTED_COMMAND with ASC 0xc1 */
+#define BLIST_RETRY_ASC_C1	((__force blist_flags_t)(1ULL << 33))
+/* Do not query the IO Advice Hints Grouping mode page */
+#define BLIST_SKIP_IO_HINTS	((__force blist_flags_t)(1ULL << 34))
+
+#define __BLIST_LAST_USED BLIST_SKIP_IO_HINTS
+
+#define __BLIST_HIGH_UNUSED (~(__BLIST_LAST_USED | \
+			       (__force blist_flags_t) \
+			       ((__force __u64)__BLIST_LAST_USED - 1ULL)))
+#define __BLIST_UNUSED_MASK (__BLIST_UNUSED_14 | \
+			     __BLIST_UNUSED_15 | \
+			     __BLIST_UNUSED_16 | \
+			     __BLIST_UNUSED_24 | \
+			     __BLIST_UNUSED_27 | \
+			     __BLIST_HIGH_UNUSED)
+
+#endif