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, 49 insertions, 0 deletions

diff --git a/include/uapi/rdma/erdma-abi.h b/include/uapi/rdma/erdma-abi.h
new file mode 100644
index 000000000..b7a0222f9
--- /dev/null
+++ b/include/uapi/rdma/erdma-abi.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/*
+ * Copyright (c) 2020-2022, Alibaba Group.
+ */
+
+#ifndef __ERDMA_USER_H__
+#define __ERDMA_USER_H__
+
+#include <linux/types.h>
+
+#define ERDMA_ABI_VERSION       1
+
+struct erdma_ureq_create_cq {
+	__aligned_u64 db_record_va;
+	__aligned_u64 qbuf_va;
+	__u32 qbuf_len;
+	__u32 rsvd0;
+};
+
+struct erdma_uresp_create_cq {
+	__u32 cq_id;
+	__u32 num_cqe;
+};
+
+struct erdma_ureq_create_qp {
+	__aligned_u64 db_record_va;
+	__aligned_u64 qbuf_va;
+	__u32 qbuf_len;
+	__u32 rsvd0;
+};
+
+struct erdma_uresp_create_qp {
+	__u32 qp_id;
+	__u32 num_sqe;
+	__u32 num_rqe;
+	__u32 rq_offset;
+};
+
+struct erdma_uresp_alloc_ctx {
+	__u32 dev_id;
+	__u32 pad;
+	__u32 sdb_type;
+	__u32 sdb_offset;
+	__aligned_u64 sdb;
+	__aligned_u64 rdb;
+	__aligned_u64 cdb;
+};
+
+#endif