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, 71 insertions, 0 deletions

diff --git a/include/rdma/rdma_counter.h b/include/rdma/rdma_counter.h
new file mode 100644
index 000000000..4204d08a0
--- /dev/null
+++ b/include/rdma/rdma_counter.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
+/*
+ * Copyright (c) 2019 Mellanox Technologies. All rights reserved.
+ */
+
+#ifndef _RDMA_COUNTER_H_
+#define _RDMA_COUNTER_H_
+
+#include <linux/mutex.h>
+#include <linux/pid_namespace.h>
+
+#include <rdma/restrack.h>
+#include <rdma/rdma_netlink.h>
+
+struct ib_device;
+struct ib_qp;
+
+struct auto_mode_param {
+	int qp_type;
+};
+
+struct rdma_counter_mode {
+	enum rdma_nl_counter_mode mode;
+	enum rdma_nl_counter_mask mask;
+	struct auto_mode_param param;
+	bool bind_opcnt;
+};
+
+struct rdma_port_counter {
+	struct rdma_counter_mode mode;
+	struct rdma_hw_stats *hstats;
+	unsigned int num_counters;
+	struct mutex lock;
+};
+
+struct rdma_counter {
+	struct rdma_restrack_entry	res;
+	struct ib_device		*device;
+	uint32_t			id;
+	struct kref			kref;
+	struct rdma_counter_mode	mode;
+	struct mutex			lock;
+	struct rdma_hw_stats		*stats;
+	u32				port;
+};
+
+void rdma_counter_init(struct ib_device *dev);
+void rdma_counter_release(struct ib_device *dev);
+int rdma_counter_set_auto_mode(struct ib_device *dev, u32 port,
+			       enum rdma_nl_counter_mask mask,
+			       bool bind_opcnt,
+			       struct netlink_ext_ack *extack);
+int rdma_counter_bind_qp_auto(struct ib_qp *qp, u32 port);
+int rdma_counter_unbind_qp(struct ib_qp *qp, u32 port, bool force);
+
+int rdma_counter_query_stats(struct rdma_counter *counter);
+u64 rdma_counter_get_hwstat_value(struct ib_device *dev, u32 port, u32 index);
+int rdma_counter_bind_qpn(struct ib_device *dev, u32 port,
+			  u32 qp_num, u32 counter_id);
+int rdma_counter_bind_qpn_alloc(struct ib_device *dev, u32 port,
+				u32 qp_num, u32 *counter_id);
+int rdma_counter_unbind_qpn(struct ib_device *dev, u32 port,
+			    u32 qp_num, u32 counter_id);
+int rdma_counter_get_mode(struct ib_device *dev, u32 port,
+			  enum rdma_nl_counter_mode *mode,
+			  enum rdma_nl_counter_mask *mask,
+			  bool *opcnt);
+
+int rdma_counter_modify(struct ib_device *dev, u32 port,
+			unsigned int index, bool enable);
+#endif /* _RDMA_COUNTER_H_ */