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, 74 insertions, 0 deletions

diff --git a/include/scsi/scsi_status.h b/include/scsi/scsi_status.h
new file mode 100644
index 000000000..9cb85262d
--- /dev/null
+++ b/include/scsi/scsi_status.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _SCSI_SCSI_STATUS_H
+#define _SCSI_SCSI_STATUS_H
+
+#include <linux/types.h>
+#include <scsi/scsi_proto.h>
+
+/* Message codes. */
+enum scsi_msg_byte {
+	COMMAND_COMPLETE	= 0x00,
+	EXTENDED_MESSAGE	= 0x01,
+	SAVE_POINTERS		= 0x02,
+	RESTORE_POINTERS	= 0x03,
+	DISCONNECT		= 0x04,
+	INITIATOR_ERROR		= 0x05,
+	ABORT_TASK_SET		= 0x06,
+	MESSAGE_REJECT		= 0x07,
+	NOP			= 0x08,
+	MSG_PARITY_ERROR	= 0x09,
+	LINKED_CMD_COMPLETE	= 0x0a,
+	LINKED_FLG_CMD_COMPLETE	= 0x0b,
+	TARGET_RESET		= 0x0c,
+	ABORT_TASK		= 0x0d,
+	CLEAR_TASK_SET		= 0x0e,
+	INITIATE_RECOVERY	= 0x0f,            /* SCSI-II only */
+	RELEASE_RECOVERY	= 0x10,            /* SCSI-II only */
+	TERMINATE_IO_PROC	= 0x11,            /* SCSI-II only */
+	CLEAR_ACA		= 0x16,
+	LOGICAL_UNIT_RESET	= 0x17,
+	SIMPLE_QUEUE_TAG	= 0x20,
+	HEAD_OF_QUEUE_TAG	= 0x21,
+	ORDERED_QUEUE_TAG	= 0x22,
+	IGNORE_WIDE_RESIDUE	= 0x23,
+	ACA			= 0x24,
+	QAS_REQUEST		= 0x55,
+
+	/* Old SCSI2 names, don't use in new code */
+	BUS_DEVICE_RESET	= TARGET_RESET,
+	ABORT			= ABORT_TASK_SET,
+};
+
+/* Host byte codes. */
+enum scsi_host_status {
+	DID_OK		= 0x00,	/* NO error                                */
+	DID_NO_CONNECT	= 0x01,	/* Couldn't connect before timeout period  */
+	DID_BUS_BUSY	= 0x02,	/* BUS stayed busy through time out period */
+	DID_TIME_OUT	= 0x03,	/* TIMED OUT for other reason              */
+	DID_BAD_TARGET	= 0x04,	/* BAD target.                             */
+	DID_ABORT	= 0x05,	/* Told to abort for some other reason     */
+	DID_PARITY	= 0x06,	/* Parity error                            */
+	DID_ERROR	= 0x07,	/* Internal error                          */
+	DID_RESET	= 0x08,	/* Reset by somebody.                      */
+	DID_BAD_INTR	= 0x09,	/* Got an interrupt we weren't expecting.  */
+	DID_PASSTHROUGH	= 0x0a,	/* Force command past mid-layer            */
+	DID_SOFT_ERROR	= 0x0b,	/* The low level driver just wish a retry  */
+	DID_IMM_RETRY	= 0x0c,	/* Retry without decrementing retry count  */
+	DID_REQUEUE	= 0x0d,	/* Requeue command (no immediate retry) also
+				 * without decrementing the retry count	   */
+	DID_TRANSPORT_DISRUPTED = 0x0e, /* Transport error disrupted execution
+					 * and the driver blocked the port to
+					 * recover the link. Transport class will
+					 * retry or fail IO */
+	DID_TRANSPORT_FAILFAST = 0x0f, /* Transport class fastfailed the io */
+	/*
+	 * We used to have DID_TARGET_FAILURE, DID_NEXUS_FAILURE,
+	 * DID_ALLOC_FAILURE and DID_MEDIUM_ERROR at 0x10 - 0x13. For compat
+	 * with userspace apps that parse the host byte for SG IO, we leave
+	 * that block of codes unused and start at 0x14 below.
+	 */
+	DID_TRANSPORT_MARGINAL = 0x14, /* Transport marginal errors */
+};
+
+#endif /* _SCSI_SCSI_STATUS_H */