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, 141 insertions, 0 deletions

diff --git a/include/soc/fsl/dpaa2-io.h b/include/soc/fsl/dpaa2-io.h
new file mode 100644
index 000000000..4bf62de2e
--- /dev/null
+++ b/include/soc/fsl/dpaa2-io.h
@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
+/*
+ * Copyright 2014-2016 Freescale Semiconductor Inc.
+ * Copyright 2017-2019 NXP
+ *
+ */
+#ifndef __FSL_DPAA2_IO_H
+#define __FSL_DPAA2_IO_H
+
+#include <linux/types.h>
+#include <linux/cpumask.h>
+#include <linux/irqreturn.h>
+
+#include "dpaa2-fd.h"
+#include "dpaa2-global.h"
+
+struct dpaa2_io;
+struct dpaa2_io_store;
+struct device;
+
+/**
+ * DOC: DPIO Service
+ *
+ * The DPIO service provides APIs for users to interact with the datapath
+ * by enqueueing and dequeing frame descriptors.
+ *
+ * The following set of APIs can be used to enqueue and dequeue frames
+ * as well as producing notification callbacks when data is available
+ * for dequeue.
+ */
+
+#define DPAA2_IO_ANY_CPU	-1
+
+/**
+ * struct dpaa2_io_desc - The DPIO descriptor
+ * @receives_notifications: Use notificaton mode. Non-zero if the DPIO
+ *                  has a channel.
+ * @has_8prio:      Set to non-zero for channel with 8 priority WQs.  Ignored
+ *                  unless receives_notification is TRUE.
+ * @cpu:            The cpu index that at least interrupt handlers will
+ *                  execute on.
+ * @stash_affinity: The stash affinity for this portal favour 'cpu'
+ * @regs_cena:      The cache enabled regs.
+ * @regs_cinh:      The cache inhibited regs
+ * @dpio_id:        The dpio index
+ * @qman_version:   The qman version
+ * @qman_clk:       The qman clock frequency in Hz
+ *
+ * Describes the attributes and features of the DPIO object.
+ */
+struct dpaa2_io_desc {
+	int receives_notifications;
+	int has_8prio;
+	int cpu;
+	void *regs_cena;
+	void __iomem *regs_cinh;
+	int dpio_id;
+	u32 qman_version;
+	u32 qman_clk;
+};
+
+struct dpaa2_io *dpaa2_io_create(const struct dpaa2_io_desc *desc,
+				 struct device *dev);
+
+void dpaa2_io_down(struct dpaa2_io *d);
+
+irqreturn_t dpaa2_io_irq(struct dpaa2_io *obj);
+
+struct dpaa2_io *dpaa2_io_service_select(int cpu);
+
+/**
+ * struct dpaa2_io_notification_ctx - The DPIO notification context structure
+ * @cb:           The callback to be invoked when the notification arrives
+ * @is_cdan:      Zero for FQDAN, non-zero for CDAN
+ * @id:           FQID or channel ID, needed for rearm
+ * @desired_cpu:  The cpu on which the notifications will show up. Use
+ *                DPAA2_IO_ANY_CPU if don't care
+ * @dpio_id:      The dpio index
+ * @qman64:       The 64-bit context value shows up in the FQDAN/CDAN.
+ * @node:         The list node
+ * @dpio_private: The dpio object internal to dpio_service
+ *
+ * Used when a FQDAN/CDAN registration is made by drivers.
+ */
+struct dpaa2_io_notification_ctx {
+	void (*cb)(struct dpaa2_io_notification_ctx *ctx);
+	int is_cdan;
+	u32 id;
+	int desired_cpu;
+	int dpio_id;
+	u64 qman64;
+	struct list_head node;
+	void *dpio_private;
+};
+
+int dpaa2_io_get_cpu(struct dpaa2_io *d);
+
+int dpaa2_io_service_register(struct dpaa2_io *service,
+			      struct dpaa2_io_notification_ctx *ctx,
+			      struct device *dev);
+void dpaa2_io_service_deregister(struct dpaa2_io *service,
+				 struct dpaa2_io_notification_ctx *ctx,
+				 struct device *dev);
+int dpaa2_io_service_rearm(struct dpaa2_io *service,
+			   struct dpaa2_io_notification_ctx *ctx);
+
+int dpaa2_io_service_pull_fq(struct dpaa2_io *d, u32 fqid,
+			     struct dpaa2_io_store *s);
+int dpaa2_io_service_pull_channel(struct dpaa2_io *d, u32 channelid,
+				  struct dpaa2_io_store *s);
+
+int dpaa2_io_service_enqueue_fq(struct dpaa2_io *d, u32 fqid,
+				const struct dpaa2_fd *fd);
+int dpaa2_io_service_enqueue_multiple_fq(struct dpaa2_io *d, u32 fqid,
+				const struct dpaa2_fd *fd, int number_of_frame);
+int dpaa2_io_service_enqueue_multiple_desc_fq(struct dpaa2_io *d, u32 *fqid,
+				const struct dpaa2_fd *fd, int number_of_frame);
+int dpaa2_io_service_enqueue_qd(struct dpaa2_io *d, u32 qdid, u8 prio,
+				u16 qdbin, const struct dpaa2_fd *fd);
+int dpaa2_io_service_release(struct dpaa2_io *d, u16 bpid,
+			     const u64 *buffers, unsigned int num_buffers);
+int dpaa2_io_service_acquire(struct dpaa2_io *d, u16 bpid,
+			     u64 *buffers, unsigned int num_buffers);
+
+struct dpaa2_io_store *dpaa2_io_store_create(unsigned int max_frames,
+					     struct device *dev);
+void dpaa2_io_store_destroy(struct dpaa2_io_store *s);
+struct dpaa2_dq *dpaa2_io_store_next(struct dpaa2_io_store *s, int *is_last);
+
+int dpaa2_io_query_fq_count(struct dpaa2_io *d, u32 fqid,
+			    u32 *fcnt, u32 *bcnt);
+int dpaa2_io_query_bp_count(struct dpaa2_io *d, u16 bpid,
+			    u32 *num);
+
+int dpaa2_io_set_irq_coalescing(struct dpaa2_io *d, u32 irq_holdoff);
+void dpaa2_io_get_irq_coalescing(struct dpaa2_io *d, u32 *irq_holdoff);
+void dpaa2_io_set_adaptive_coalescing(struct dpaa2_io *d,
+				      int use_adaptive_rx_coalesce);
+int dpaa2_io_get_adaptive_coalescing(struct dpaa2_io *d);
+void dpaa2_io_update_net_dim(struct dpaa2_io *d, __u64 frames, __u64 bytes);
+#endif /* __FSL_DPAA2_IO_H */