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, 217 insertions, 0 deletions

diff --git a/include/scsi/viosrp.h b/include/scsi/viosrp.h
new file mode 100644
index 000000000..6c5559d2b
--- /dev/null
+++ b/include/scsi/viosrp.h
@@ -0,0 +1,217 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*****************************************************************************/
+/* srp.h -- SCSI RDMA Protocol definitions                                   */
+/*                                                                           */
+/* Written By: Colin Devilbis, IBM Corporation                               */
+/*                                                                           */
+/* Copyright (C) 2003 IBM Corporation                                        */
+/*                                                                           */
+/*                                                                           */
+/* This file contains structures and definitions for IBM RPA (RS/6000        */
+/* platform architecture) implementation of the SRP (SCSI RDMA Protocol)     */
+/* standard.  SRP is used on IBM iSeries and pSeries platforms to send SCSI  */
+/* commands between logical partitions.                                      */
+/*                                                                           */
+/* SRP Information Units (IUs) are sent on a "Command/Response Queue" (CRQ)  */
+/* between partitions.  The definitions in this file are architected,        */
+/* and cannot be changed without breaking compatibility with other versions  */
+/* of Linux and other operating systems (AIX, OS/400) that talk this protocol*/
+/* between logical partitions                                                */
+/*****************************************************************************/
+#ifndef VIOSRP_H
+#define VIOSRP_H
+#include <scsi/srp.h>
+
+#define SRP_VERSION "16.a"
+#define SRP_MAX_IU_LEN	256
+#define SRP_MAX_LOC_LEN 32
+
+union srp_iu {
+	struct srp_login_req login_req;
+	struct srp_login_rsp login_rsp;
+	struct srp_login_rej login_rej;
+	struct srp_i_logout i_logout;
+	struct srp_t_logout t_logout;
+	struct srp_tsk_mgmt tsk_mgmt;
+	struct srp_cmd cmd;
+	struct srp_rsp rsp;
+	u8 reserved[SRP_MAX_IU_LEN];
+};
+
+enum viosrp_crq_headers {
+	VIOSRP_CRQ_FREE = 0x00,
+	VIOSRP_CRQ_CMD_RSP = 0x80,
+	VIOSRP_CRQ_INIT_RSP = 0xC0,
+	VIOSRP_CRQ_XPORT_EVENT = 0xFF
+};
+
+enum viosrp_crq_init_formats {
+	VIOSRP_CRQ_INIT = 0x01,
+	VIOSRP_CRQ_INIT_COMPLETE = 0x02
+};
+
+enum viosrp_crq_formats {
+	VIOSRP_SRP_FORMAT = 0x01,
+	VIOSRP_MAD_FORMAT = 0x02,
+	VIOSRP_OS400_FORMAT = 0x03,
+	VIOSRP_AIX_FORMAT = 0x04,
+	VIOSRP_LINUX_FORMAT = 0x05,
+	VIOSRP_INLINE_FORMAT = 0x06
+};
+
+enum viosrp_crq_status {
+	VIOSRP_OK = 0x0,
+	VIOSRP_NONRECOVERABLE_ERR = 0x1,
+	VIOSRP_VIOLATES_MAX_XFER = 0x2,
+	VIOSRP_PARTNER_PANIC = 0x3,
+	VIOSRP_DEVICE_BUSY = 0x8,
+	VIOSRP_ADAPTER_FAIL = 0x10,
+	VIOSRP_OK2 = 0x99,
+};
+
+struct viosrp_crq {
+	union {
+		__be64 high;			/* High 64 bits */
+		struct {
+			u8 valid;		/* used by RPA */
+			u8 format;		/* SCSI vs out-of-band */
+			u8 reserved;
+			u8 status;		/* non-scsi failure? (e.g. DMA failure) */
+			__be16 timeout;		/* in seconds */
+			__be16 IU_length;	/* in bytes */
+		};
+	};
+	__be64 IU_data_ptr;	/* the TCE for transferring data */
+};
+
+/* MADs are Management requests above and beyond the IUs defined in the SRP
+ * standard.
+ */
+enum viosrp_mad_types {
+	VIOSRP_EMPTY_IU_TYPE = 0x01,
+	VIOSRP_ERROR_LOG_TYPE = 0x02,
+	VIOSRP_ADAPTER_INFO_TYPE = 0x03,
+	VIOSRP_CAPABILITIES_TYPE = 0x05,
+	VIOSRP_ENABLE_FAST_FAIL = 0x08,
+};
+
+enum viosrp_mad_status {
+	VIOSRP_MAD_SUCCESS = 0x00,
+	VIOSRP_MAD_NOT_SUPPORTED = 0xF1,
+	VIOSRP_MAD_FAILED = 0xF7,
+};
+
+enum viosrp_capability_type {
+	MIGRATION_CAPABILITIES = 0x01,
+	RESERVATION_CAPABILITIES = 0x02,
+};
+
+enum viosrp_capability_support {
+	SERVER_DOES_NOT_SUPPORTS_CAP = 0x0,
+	SERVER_SUPPORTS_CAP = 0x01,
+	SERVER_CAP_DATA = 0x02,
+};
+
+enum viosrp_reserve_type {
+	CLIENT_RESERVE_SCSI_2 = 0x01,
+};
+
+enum viosrp_capability_flag {
+	CLIENT_MIGRATED = 0x01,
+	CLIENT_RECONNECT = 0x02,
+	CAP_LIST_SUPPORTED = 0x04,
+	CAP_LIST_DATA = 0x08,
+};
+
+/*
+ * Common MAD header
+ */
+struct mad_common {
+	__be32 type;
+	__be16 status;
+	__be16 length;
+	__be64 tag;
+};
+
+/*
+ * All SRP (and MAD) requests normally flow from the
+ * client to the server.  There is no way for the server to send
+ * an asynchronous message back to the client.  The Empty IU is used
+ * to hang out a meaningless request to the server so that it can respond
+ * asynchrouously with something like a SCSI AER
+ */
+struct viosrp_empty_iu {
+	struct mad_common common;
+	__be64 buffer;
+	__be32 port;
+};
+
+struct viosrp_error_log {
+	struct mad_common common;
+	__be64 buffer;
+};
+
+struct viosrp_adapter_info {
+	struct mad_common common;
+	__be64 buffer;
+};
+
+struct viosrp_fast_fail {
+	struct mad_common common;
+};
+
+struct viosrp_capabilities {
+	struct mad_common common;
+	__be64 buffer;
+};
+
+struct mad_capability_common {
+	__be32 cap_type;
+	__be16 length;
+	__be16 server_support;
+};
+
+struct mad_reserve_cap {
+	struct mad_capability_common common;
+	__be32 type;
+};
+
+struct mad_migration_cap {
+	struct mad_capability_common common;
+	__be32 ecl;
+};
+
+struct capabilities {
+	__be32 flags;
+	char name[SRP_MAX_LOC_LEN];
+	char loc[SRP_MAX_LOC_LEN];
+	struct mad_migration_cap migration;
+	struct mad_reserve_cap reserve;
+};
+
+union mad_iu {
+	struct viosrp_empty_iu empty_iu;
+	struct viosrp_error_log error_log;
+	struct viosrp_adapter_info adapter_info;
+	struct viosrp_fast_fail fast_fail;
+	struct viosrp_capabilities capabilities;
+};
+
+union viosrp_iu {
+	union srp_iu srp;
+	union mad_iu mad;
+};
+
+struct mad_adapter_info_data {
+	char srp_version[8];
+	char partition_name[96];
+	__be32 partition_number;
+#define SRP_MAD_VERSION_1 1
+	__be32 mad_version;
+#define SRP_MAD_OS_LINUX 2
+#define SRP_MAD_OS_AIX 3
+	__be32 os_type;
+	__be32 port_max_txu[8];	/* per-port maximum transfer */
+};
+
+#endif