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, 192 insertions, 0 deletions

diff --git a/include/soc/fsl/dpaa2-global.h b/include/soc/fsl/dpaa2-global.h
new file mode 100644
index 000000000..2bfc379d3
--- /dev/null
+++ b/include/soc/fsl/dpaa2-global.h
@@ -0,0 +1,192 @@
+/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
+/*
+ * Copyright 2014-2016 Freescale Semiconductor Inc.
+ * Copyright 2016 NXP
+ *
+ */
+#ifndef __FSL_DPAA2_GLOBAL_H
+#define __FSL_DPAA2_GLOBAL_H
+
+#include <linux/types.h>
+#include <linux/cpumask.h>
+#include "dpaa2-fd.h"
+
+struct dpaa2_dq {
+	union {
+		struct common {
+			u8 verb;
+			u8 reserved[63];
+		} common;
+		struct dq {
+			u8 verb;
+			u8 stat;
+			__le16 seqnum;
+			__le16 oprid;
+			u8 reserved;
+			u8 tok;
+			__le32 fqid;
+			u32 reserved2;
+			__le32 fq_byte_cnt;
+			__le32 fq_frm_cnt;
+			__le64 fqd_ctx;
+			u8 fd[32];
+		} dq;
+		struct scn {
+			u8 verb;
+			u8 stat;
+			u8 state;
+			u8 reserved;
+			__le32 rid_tok;
+			__le64 ctx;
+		} scn;
+	};
+};
+
+/* Parsing frame dequeue results */
+/* FQ empty */
+#define DPAA2_DQ_STAT_FQEMPTY       0x80
+/* FQ held active */
+#define DPAA2_DQ_STAT_HELDACTIVE    0x40
+/* FQ force eligible */
+#define DPAA2_DQ_STAT_FORCEELIGIBLE 0x20
+/* valid frame */
+#define DPAA2_DQ_STAT_VALIDFRAME    0x10
+/* FQ ODP enable */
+#define DPAA2_DQ_STAT_ODPVALID      0x04
+/* volatile dequeue */
+#define DPAA2_DQ_STAT_VOLATILE      0x02
+/* volatile dequeue command is expired */
+#define DPAA2_DQ_STAT_EXPIRED       0x01
+
+#define DQ_FQID_MASK		0x00FFFFFF
+#define DQ_FRAME_COUNT_MASK	0x00FFFFFF
+
+/**
+ * dpaa2_dq_flags() - Get the stat field of dequeue response
+ * @dq: the dequeue result.
+ */
+static inline u32 dpaa2_dq_flags(const struct dpaa2_dq *dq)
+{
+	return dq->dq.stat;
+}
+
+/**
+ * dpaa2_dq_is_pull() - Check whether the dq response is from a pull
+ *                      command.
+ * @dq: the dequeue result
+ *
+ * Return 1 for volatile(pull) dequeue, 0 for static dequeue.
+ */
+static inline int dpaa2_dq_is_pull(const struct dpaa2_dq *dq)
+{
+	return (int)(dpaa2_dq_flags(dq) & DPAA2_DQ_STAT_VOLATILE);
+}
+
+/**
+ * dpaa2_dq_is_pull_complete() - Check whether the pull command is completed.
+ * @dq: the dequeue result
+ *
+ * Return boolean.
+ */
+static inline bool dpaa2_dq_is_pull_complete(const struct dpaa2_dq *dq)
+{
+	return !!(dpaa2_dq_flags(dq) & DPAA2_DQ_STAT_EXPIRED);
+}
+
+/**
+ * dpaa2_dq_seqnum() - Get the seqnum field in dequeue response
+ * @dq: the dequeue result
+ *
+ * seqnum is valid only if VALIDFRAME flag is TRUE
+ *
+ * Return seqnum.
+ */
+static inline u16 dpaa2_dq_seqnum(const struct dpaa2_dq *dq)
+{
+	return le16_to_cpu(dq->dq.seqnum);
+}
+
+/**
+ * dpaa2_dq_odpid() - Get the odpid field in dequeue response
+ * @dq: the dequeue result
+ *
+ * odpid is valid only if ODPVALID flag is TRUE.
+ *
+ * Return odpid.
+ */
+static inline u16 dpaa2_dq_odpid(const struct dpaa2_dq *dq)
+{
+	return le16_to_cpu(dq->dq.oprid);
+}
+
+/**
+ * dpaa2_dq_fqid() - Get the fqid in dequeue response
+ * @dq: the dequeue result
+ *
+ * Return fqid.
+ */
+static inline u32 dpaa2_dq_fqid(const struct dpaa2_dq *dq)
+{
+	return le32_to_cpu(dq->dq.fqid) & DQ_FQID_MASK;
+}
+
+/**
+ * dpaa2_dq_byte_count() - Get the byte count in dequeue response
+ * @dq: the dequeue result
+ *
+ * Return the byte count remaining in the FQ.
+ */
+static inline u32 dpaa2_dq_byte_count(const struct dpaa2_dq *dq)
+{
+	return le32_to_cpu(dq->dq.fq_byte_cnt);
+}
+
+/**
+ * dpaa2_dq_frame_count() - Get the frame count in dequeue response
+ * @dq: the dequeue result
+ *
+ * Return the frame count remaining in the FQ.
+ */
+static inline u32 dpaa2_dq_frame_count(const struct dpaa2_dq *dq)
+{
+	return le32_to_cpu(dq->dq.fq_frm_cnt) & DQ_FRAME_COUNT_MASK;
+}
+
+/**
+ * dpaa2_dq_fd_ctx() - Get the frame queue context in dequeue response
+ * @dq: the dequeue result
+ *
+ * Return the frame queue context.
+ */
+static inline u64 dpaa2_dq_fqd_ctx(const struct dpaa2_dq *dq)
+{
+	return le64_to_cpu(dq->dq.fqd_ctx);
+}
+
+/**
+ * dpaa2_dq_fd() - Get the frame descriptor in dequeue response
+ * @dq: the dequeue result
+ *
+ * Return the frame descriptor.
+ */
+static inline const struct dpaa2_fd *dpaa2_dq_fd(const struct dpaa2_dq *dq)
+{
+	return (const struct dpaa2_fd *)&dq->dq.fd[0];
+}
+
+#define DPAA2_CSCN_SIZE		sizeof(struct dpaa2_dq)
+#define DPAA2_CSCN_ALIGN	16
+#define DPAA2_CSCN_STATE_CG	BIT(0)
+
+/**
+ * dpaa2_cscn_state_congested() - Check congestion state
+ * @cscn: congestion SCN (delivered to WQ or memory)
+ *
+i * Return true is congested.
+ */
+static inline bool dpaa2_cscn_state_congested(struct dpaa2_dq *cscn)
+{
+	return !!(cscn->scn.state & DPAA2_CSCN_STATE_CG);
+}
+
+#endif /* __FSL_DPAA2_GLOBAL_H */