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, 124 insertions, 0 deletions

diff --git a/include/rdma/opa_smi.h b/include/rdma/opa_smi.h
new file mode 100644
index 000000000..a9f1b5700
--- /dev/null
+++ b/include/rdma/opa_smi.h
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
+/*
+ * Copyright (c) 2014 Intel Corporation.  All rights reserved.
+ */
+
+#ifndef OPA_SMI_H
+#define OPA_SMI_H
+
+#include <rdma/ib_mad.h>
+#include <rdma/ib_smi.h>
+
+#define OPA_SMP_LID_DATA_SIZE			2016
+#define OPA_SMP_DR_DATA_SIZE			1872
+#define OPA_SMP_MAX_PATH_HOPS			64
+
+#define OPA_MAX_VLS				32
+#define OPA_MAX_SLS				32
+#define OPA_MAX_SCS				32
+
+#define OPA_LID_PERMISSIVE			cpu_to_be32(0xFFFFFFFF)
+
+struct opa_smp {
+	u8	base_version;
+	u8	mgmt_class;
+	u8	class_version;
+	u8	method;
+	__be16	status;
+	u8	hop_ptr;
+	u8	hop_cnt;
+	__be64	tid;
+	__be16	attr_id;
+	__be16	resv;
+	__be32	attr_mod;
+	__be64	mkey;
+	union {
+		struct {
+			uint8_t data[OPA_SMP_LID_DATA_SIZE];
+		} lid;
+		struct {
+			__be32	dr_slid;
+			__be32	dr_dlid;
+			u8	initial_path[OPA_SMP_MAX_PATH_HOPS];
+			u8	return_path[OPA_SMP_MAX_PATH_HOPS];
+			u8	reserved[8];
+			u8	data[OPA_SMP_DR_DATA_SIZE];
+		} dr;
+	} route;
+} __packed;
+
+
+/* Subnet management attributes */
+/* ... */
+#define OPA_ATTRIB_ID_NODE_DESCRIPTION		cpu_to_be16(0x0010)
+#define OPA_ATTRIB_ID_NODE_INFO			cpu_to_be16(0x0011)
+#define OPA_ATTRIB_ID_PORT_INFO			cpu_to_be16(0x0015)
+#define OPA_ATTRIB_ID_PARTITION_TABLE		cpu_to_be16(0x0016)
+#define OPA_ATTRIB_ID_SL_TO_SC_MAP		cpu_to_be16(0x0017)
+#define OPA_ATTRIB_ID_VL_ARBITRATION		cpu_to_be16(0x0018)
+#define OPA_ATTRIB_ID_SM_INFO			cpu_to_be16(0x0020)
+#define OPA_ATTRIB_ID_CABLE_INFO		cpu_to_be16(0x0032)
+#define OPA_ATTRIB_ID_AGGREGATE			cpu_to_be16(0x0080)
+#define OPA_ATTRIB_ID_SC_TO_SL_MAP		cpu_to_be16(0x0082)
+#define OPA_ATTRIB_ID_SC_TO_VLR_MAP		cpu_to_be16(0x0083)
+#define OPA_ATTRIB_ID_SC_TO_VLT_MAP		cpu_to_be16(0x0084)
+#define OPA_ATTRIB_ID_SC_TO_VLNT_MAP		cpu_to_be16(0x0085)
+/* ... */
+#define OPA_ATTRIB_ID_PORT_STATE_INFO		cpu_to_be16(0x0087)
+/* ... */
+#define OPA_ATTRIB_ID_BUFFER_CONTROL_TABLE	cpu_to_be16(0x008A)
+/* ... */
+
+struct opa_node_description {
+	u8 data[64];
+} __packed;
+
+struct opa_node_info {
+	u8      base_version;
+	u8      class_version;
+	u8      node_type;
+	u8      num_ports;
+	__be32  reserved;
+	__be64  system_image_guid;
+	__be64  node_guid;
+	__be64  port_guid;
+	__be16  partition_cap;
+	__be16  device_id;
+	__be32  revision;
+	u8      local_port_num;
+	u8      vendor_id[3];   /* network byte order */
+} __packed;
+
+#define OPA_PARTITION_TABLE_BLK_SIZE 32
+
+static inline u8
+opa_get_smp_direction(struct opa_smp *smp)
+{
+	return ib_get_smp_direction((struct ib_smp *)smp);
+}
+
+static inline u8 *opa_get_smp_data(struct opa_smp *smp)
+{
+	if (smp->mgmt_class == IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE)
+		return smp->route.dr.data;
+
+	return smp->route.lid.data;
+}
+
+static inline size_t opa_get_smp_data_size(struct opa_smp *smp)
+{
+	if (smp->mgmt_class == IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE)
+		return sizeof(smp->route.dr.data);
+
+	return sizeof(smp->route.lid.data);
+}
+
+static inline size_t opa_get_smp_header_size(struct opa_smp *smp)
+{
+	if (smp->mgmt_class == IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE)
+		return sizeof(*smp) - sizeof(smp->route.dr.data);
+
+	return sizeof(*smp) - sizeof(smp->route.lid.data);
+}
+
+#endif /* OPA_SMI_H */