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, 112 insertions, 0 deletions

diff --git a/include/uapi/rdma/mthca-abi.h b/include/uapi/rdma/mthca-abi.h
new file mode 100644
index 000000000..91b12e1a6
--- /dev/null
+++ b/include/uapi/rdma/mthca-abi.h
@@ -0,0 +1,112 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR Linux-OpenIB) */
+/*
+ * Copyright (c) 2005 Topspin Communications.  All rights reserved.
+ * Copyright (c) 2005, 2006 Cisco Systems.  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 MTHCA_ABI_USER_H
+#define MTHCA_ABI_USER_H
+
+#include <linux/types.h>
+
+/*
+ * Increment this value if any changes that break userspace ABI
+ * compatibility are made.
+ */
+#define MTHCA_UVERBS_ABI_VERSION	1
+
+/*
+ * Make sure that all structs defined in this file remain laid out so
+ * that they pack the same way on 32-bit and 64-bit architectures (to
+ * avoid incompatibility between 32-bit userspace and 64-bit kernels).
+ * In particular do not use pointer types -- pass pointers in __u64
+ * instead.
+ */
+struct mthca_alloc_ucontext_resp {
+	__u32 qp_tab_size;
+	__u32 uarc_size;
+};
+
+struct mthca_alloc_pd_resp {
+	__u32 pdn;
+	__u32 reserved;
+};
+
+/*
+ * Mark the memory region with a DMA attribute that causes
+ * in-flight DMA to be flushed when the region is written to:
+ */
+#define MTHCA_MR_DMASYNC	0x1
+
+struct mthca_reg_mr {
+	__u32 mr_attrs;
+	__u32 reserved;
+};
+
+struct mthca_create_cq {
+	__u32 lkey;
+	__u32 pdn;
+	__aligned_u64 arm_db_page;
+	__aligned_u64 set_db_page;
+	__u32 arm_db_index;
+	__u32 set_db_index;
+};
+
+struct mthca_create_cq_resp {
+	__u32 cqn;
+	__u32 reserved;
+};
+
+struct mthca_resize_cq {
+	__u32 lkey;
+	__u32 reserved;
+};
+
+struct mthca_create_srq {
+	__u32 lkey;
+	__u32 db_index;
+	__aligned_u64 db_page;
+};
+
+struct mthca_create_srq_resp {
+	__u32 srqn;
+	__u32 reserved;
+};
+
+struct mthca_create_qp {
+	__u32 lkey;
+	__u32 reserved;
+	__aligned_u64 sq_db_page;
+	__aligned_u64 rq_db_page;
+	__u32 sq_db_index;
+	__u32 rq_db_index;
+};
+#endif /* MTHCA_ABI_USER_H */