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, 78 insertions, 0 deletions

diff --git a/include/scsi/iser.h b/include/scsi/iser.h
new file mode 100644
index 000000000..07a83bfa2
--- /dev/null
+++ b/include/scsi/iser.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2015 Mellanox Technologies. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *	- Redistributions of source code must retain the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer.
+ *
+ *	- Redistributions in binary form must reproduce the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer in the documentation and/or other materials
+ *	  provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef ISCSI_ISER_H
+#define ISCSI_ISER_H
+
+#define ISER_ZBVA_NOT_SUP		0x80
+#define ISER_SEND_W_INV_NOT_SUP		0x40
+#define ISERT_ZBVA_NOT_USED		0x80
+#define ISERT_SEND_W_INV_NOT_USED	0x40
+
+#define ISCSI_CTRL	0x10
+#define ISER_HELLO	0x20
+#define ISER_HELLORPLY	0x30
+
+#define ISER_VER	0x10
+#define ISER_WSV	0x08
+#define ISER_RSV	0x04
+
+/**
+ * struct iser_cm_hdr - iSER CM header (from iSER Annex A12)
+ *
+ * @flags:        flags support (zbva, send_w_inv)
+ * @rsvd:         reserved
+ */
+struct iser_cm_hdr {
+	u8      flags;
+	u8      rsvd[3];
+} __packed;
+
+/**
+ * struct iser_ctrl - iSER header of iSCSI control PDU
+ *
+ * @flags:        opcode and read/write valid bits
+ * @rsvd:         reserved
+ * @write_stag:   write rkey
+ * @write_va:     write virtual address
+ * @read_stag:    read rkey
+ * @read_va:      read virtual address
+ */
+struct iser_ctrl {
+	u8      flags;
+	u8      rsvd[3];
+	__be32  write_stag;
+	__be64  write_va;
+	__be32  read_stag;
+	__be64  read_va;
+} __packed;
+
+#endif /* ISCSI_ISER_H */