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, 127 insertions, 0 deletions

diff --git a/drivers/pinctrl/mediatek/mtk-eint.h b/drivers/pinctrl/mediatek/mtk-eint.h
new file mode 100644
index 000000000..3cdd6f631
--- /dev/null
+++ b/drivers/pinctrl/mediatek/mtk-eint.h
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2014-2025 MediaTek Inc.
+ *
+ * Author: Maoguang Meng <maoguang.meng@mediatek.com>
+ *	   Sean Wang <sean.wang@mediatek.com>
+ *	   Hao Chang <ot_chhao.chang@mediatek.com>
+ *	   Qingliang Li <qingliang.li@mediatek.com>
+ */
+#ifndef __MTK_EINT_H
+#define __MTK_EINT_H
+
+#include <linux/irqdomain.h>
+
+struct mtk_eint_regs {
+	unsigned int	stat;
+	unsigned int	ack;
+	unsigned int	mask;
+	unsigned int	mask_set;
+	unsigned int	mask_clr;
+	unsigned int	sens;
+	unsigned int	sens_set;
+	unsigned int	sens_clr;
+	unsigned int	soft;
+	unsigned int	soft_set;
+	unsigned int	soft_clr;
+	unsigned int	pol;
+	unsigned int	pol_set;
+	unsigned int	pol_clr;
+	unsigned int	dom_en;
+	unsigned int	dbnc_ctrl;
+	unsigned int	dbnc_set;
+	unsigned int	dbnc_clr;
+};
+
+struct mtk_eint_hw {
+	u8		port_mask;
+	u8		ports;
+	unsigned int	ap_num;
+	unsigned int	db_cnt;
+	const unsigned int *db_time;
+};
+
+struct mtk_eint_pin {
+	u16 number;
+	u8 instance;
+	u8 index;
+	bool debounce;
+	bool dual_edge;
+};
+
+extern const unsigned int debounce_time_mt2701[];
+extern const unsigned int debounce_time_mt6765[];
+extern const unsigned int debounce_time_mt6795[];
+extern const unsigned int debounce_time_mt6878[];
+
+struct mtk_eint;
+
+struct mtk_eint_xt {
+	int (*get_gpio_n)(void *data, unsigned long eint_n,
+			  unsigned int *gpio_n,
+			  struct gpio_chip **gpio_chip);
+	int (*get_gpio_state)(void *data, unsigned long eint_n);
+	int (*set_gpio_as_eint)(void *data, unsigned long eint_n);
+};
+
+struct mtk_eint {
+	struct device *dev;
+	void __iomem **base;
+	int nbase;
+	u16 *base_pin_num;
+	struct irq_domain *domain;
+	int irq;
+
+	int *dual_edge;
+	u16 **pin_list;
+	u32 **wake_mask;
+	u32 **cur_mask;
+
+	/* Used to fit into various EINT device */
+	const struct mtk_eint_hw *hw;
+	const struct mtk_eint_regs *regs;
+	struct mtk_eint_pin *pins;
+	u16 num_db_time;
+
+	/* Used to fit into various pinctrl device */
+	void *pctl;
+	const struct mtk_eint_xt *gpio_xlate;
+};
+
+#if IS_ENABLED(CONFIG_EINT_MTK)
+int mtk_eint_do_init(struct mtk_eint *eint, struct mtk_eint_pin *eint_pin);
+int mtk_eint_do_suspend(struct mtk_eint *eint);
+int mtk_eint_do_resume(struct mtk_eint *eint);
+int mtk_eint_set_debounce(struct mtk_eint *eint, unsigned long eint_n,
+			  unsigned int debounce);
+int mtk_eint_find_irq(struct mtk_eint *eint, unsigned long eint_n);
+
+#else
+static inline int mtk_eint_do_init(struct mtk_eint *eint,
+				   struct mtk_eint_pin *eint_pin)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int mtk_eint_do_suspend(struct mtk_eint *eint)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int mtk_eint_do_resume(struct mtk_eint *eint)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int mtk_eint_set_debounce(struct mtk_eint *eint, unsigned long eint_n,
+			  unsigned int debounce)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int mtk_eint_find_irq(struct mtk_eint *eint, unsigned long eint_n)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+#endif /* __MTK_EINT_H */