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, 92 insertions, 0 deletions

diff --git a/drivers/clk/qcom/common.h b/drivers/clk/qcom/common.h
new file mode 100644
index 000000000..6f2406f88
--- /dev/null
+++ b/drivers/clk/qcom/common.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2014, The Linux Foundation. All rights reserved. */
+
+#ifndef __QCOM_CLK_COMMON_H__
+#define __QCOM_CLK_COMMON_H__
+
+struct platform_device;
+struct regmap_config;
+struct clk_regmap;
+struct qcom_reset_map;
+struct regmap;
+struct freq_tbl;
+struct clk_hw;
+
+#define PLL_LOCK_COUNT_SHIFT	8
+#define PLL_LOCK_COUNT_MASK	0x3f
+#define PLL_BIAS_COUNT_SHIFT	14
+#define PLL_BIAS_COUNT_MASK	0x3f
+#define PLL_VOTE_FSM_ENA	BIT(20)
+#define PLL_VOTE_FSM_RESET	BIT(21)
+
+struct qcom_icc_hws_data {
+	int master_id;
+	int slave_id;
+	int clk_id;
+};
+
+struct qcom_cc_driver_data {
+	struct clk_alpha_pll **alpha_plls;
+	size_t num_alpha_plls;
+	const u32 *clk_cbcrs;
+	size_t num_clk_cbcrs;
+	const struct clk_rcg_dfs_data *dfs_rcgs;
+	size_t num_dfs_rcgs;
+	void (*clk_regs_configure)(struct device *dev, struct regmap *regmap);
+};
+
+struct qcom_cc_desc {
+	const struct regmap_config *config;
+	struct clk_regmap **clks;
+	size_t num_clks;
+	const struct qcom_reset_map *resets;
+	size_t num_resets;
+	struct gdsc **gdscs;
+	size_t num_gdscs;
+	struct clk_hw **clk_hws;
+	size_t num_clk_hws;
+	const struct qcom_icc_hws_data *icc_hws;
+	size_t num_icc_hws;
+	unsigned int icc_first_node_id;
+	bool use_rpm;
+	const struct qcom_cc_driver_data *driver_data;
+};
+
+/**
+ * struct parent_map - map table for source select configuration values
+ * @src: source
+ * @cfg: configuration value
+ */
+struct parent_map {
+	u8 src;
+	u8 cfg;
+};
+
+extern const struct freq_tbl *qcom_find_freq(const struct freq_tbl *f,
+					     unsigned long rate);
+extern const struct freq_tbl *qcom_find_freq_floor(const struct freq_tbl *f,
+						   unsigned long rate);
+extern const struct freq_multi_tbl *qcom_find_freq_multi(const struct freq_multi_tbl *f,
+							 unsigned long rate);
+extern void
+qcom_pll_set_fsm_mode(struct regmap *m, u32 reg, u8 bias_count, u8 lock_count);
+extern int qcom_find_src_index(struct clk_hw *hw, const struct parent_map *map,
+			       u8 src);
+extern int qcom_find_cfg_index(struct clk_hw *hw, const struct parent_map *map,
+			       u8 cfg);
+
+extern int qcom_cc_register_board_clk(struct device *dev, const char *path,
+				      const char *name, unsigned long rate);
+extern int qcom_cc_register_sleep_clk(struct device *dev);
+
+extern struct regmap *qcom_cc_map(struct platform_device *pdev,
+				  const struct qcom_cc_desc *desc);
+extern int qcom_cc_really_probe(struct device *dev,
+				const struct qcom_cc_desc *desc,
+				struct regmap *regmap);
+extern int qcom_cc_probe(struct platform_device *pdev,
+			 const struct qcom_cc_desc *desc);
+extern int qcom_cc_probe_by_index(struct platform_device *pdev, int index,
+				  const struct qcom_cc_desc *desc);
+
+#endif