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, 113 insertions, 0 deletions

diff --git a/drivers/interconnect/imx/imx.h b/drivers/interconnect/imx/imx.h
new file mode 100644
index 000000000..d4d0e9888
--- /dev/null
+++ b/drivers/interconnect/imx/imx.h
@@ -0,0 +1,113 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Interconnect framework driver for i.MX SoC
+ *
+ * Copyright (c) 2019, BayLibre
+ * Copyright (c) 2019-2020, NXP
+ * Author: Alexandre Bailon <abailon@baylibre.com>
+ * Author: Leonard Crestez <leonard.crestez@nxp.com>
+ */
+#ifndef __DRIVERS_INTERCONNECT_IMX_H
+#define __DRIVERS_INTERCONNECT_IMX_H
+
+#include <linux/args.h>
+#include <linux/bits.h>
+#include <linux/types.h>
+
+#include <linux/interconnect-provider.h>
+
+struct platform_device;
+
+#define IMX_ICC_MAX_LINKS	4
+
+/*
+ * High throughput priority level in Regulator mode
+ * Read Priority in Fixed/Limiter mode
+ */
+#define PRIORITY0_SHIFT	0
+/*
+ * Low throughput priority level in Regulator mode
+ * Write Priority in Fixed/Limiter mode
+ */
+#define PRIORITY1_SHIFT	8
+#define PRIORITY_MASK		0x7
+
+#define PRIORITY_COMP_MARK	BIT(31)	/* Must set */
+
+#define IMX_NOC_MODE_FIXED		0
+#define IMX_NOC_MODE_LIMITER		1
+#define IMX_NOC_MODE_BYPASS		2
+#define IMX_NOC_MODE_REGULATOR		3
+#define IMX_NOC_MODE_UNCONFIGURED	0xFF
+
+#define IMX_NOC_PRIO_REG	0x8
+#define IMX_NOC_MODE_REG	0xC
+#define IMX_NOC_BANDWIDTH_REG	0x10
+#define IMX_NOC_SATURATION	0x14
+#define IMX_NOC_EXT_CTL_REG	0x18
+
+struct imx_icc_provider {
+	void __iomem *noc_base;
+	struct icc_provider provider;
+};
+
+/*
+ * struct imx_icc_node_adj - Describe a dynamic adjustable node
+ */
+struct imx_icc_node_adj_desc {
+	unsigned int bw_mul, bw_div;
+	const char *phandle_name;
+	bool main_noc;
+};
+
+/*
+ * struct imx_icc_node - Describe an interconnect node
+ * @name: name of the node
+ * @id: an unique id to identify the node
+ * @links: an array of slaves' node id
+ * @num_links: number of id defined in links
+ */
+struct imx_icc_node_desc {
+	const char *name;
+	u16 id;
+	u16 links[IMX_ICC_MAX_LINKS];
+	u16 num_links;
+	const struct imx_icc_node_adj_desc *adj;
+};
+
+/*
+ * struct imx_icc_noc_setting - Describe an interconnect node setting
+ * @reg: register offset inside the NoC
+ * @prio_level: priority level
+ * @mode: functional mode
+ * @ext_control: external input control
+ */
+struct imx_icc_noc_setting {
+	u32 reg;
+	u32 prio_level;
+	u32 mode;
+	u32 ext_control;
+};
+
+#define DEFINE_BUS_INTERCONNECT(_name, _id, _adj, ...)			\
+	{								\
+		.id = _id,						\
+		.name = _name,						\
+		.adj = _adj,						\
+		.num_links = COUNT_ARGS(__VA_ARGS__),			\
+		.links = { __VA_ARGS__ },				\
+	}
+
+#define DEFINE_BUS_MASTER(_name, _id, _dest_id)				\
+	DEFINE_BUS_INTERCONNECT(_name, _id, NULL, _dest_id)
+
+#define DEFINE_BUS_SLAVE(_name, _id, _adj)				\
+	DEFINE_BUS_INTERCONNECT(_name, _id, _adj)
+
+int imx_icc_register(struct platform_device *pdev,
+		     struct imx_icc_node_desc *nodes,
+		     int nodes_count,
+		     struct imx_icc_noc_setting *noc_settings);
+void imx_icc_unregister(struct platform_device *pdev);
+
+#endif /* __DRIVERS_INTERCONNECT_IMX_H */