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, 63 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/stm32fx-clock.h b/include/dt-bindings/clock/stm32fx-clock.h
new file mode 100644
index 000000000..b6ff9c68c
--- /dev/null
+++ b/include/dt-bindings/clock/stm32fx-clock.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * stm32fx-clock.h
+ *
+ * Copyright (C) 2016 STMicroelectronics
+ * Author: Gabriel Fernandez for STMicroelectronics.
+ */
+
+/*
+ * List of clocks which are not derived from system clock (SYSCLOCK)
+ *
+ * The index of these clocks is the secondary index of DT bindings
+ * (see Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml)
+ *
+ * e.g:
+	<assigned-clocks = <&rcc 1 CLK_LSE>;
+*/
+
+#ifndef _DT_BINDINGS_CLK_STMFX_H
+#define _DT_BINDINGS_CLK_STMFX_H
+
+#define SYSTICK			0
+#define FCLK			1
+#define CLK_LSI			2
+#define CLK_LSE			3
+#define CLK_HSE_RTC		4
+#define CLK_RTC			5
+#define PLL_VCO_I2S		6
+#define PLL_VCO_SAI		7
+#define CLK_LCD			8
+#define CLK_I2S			9
+#define CLK_SAI1		10
+#define CLK_SAI2		11
+#define CLK_I2SQ_PDIV		12
+#define CLK_SAIQ_PDIV		13
+#define CLK_HSI			14
+#define CLK_SYSCLK		15
+#define CLK_F469_DSI		16
+
+#define END_PRIMARY_CLK		17
+
+#define CLK_HDMI_CEC		16
+#define CLK_SPDIF		17
+#define CLK_USART1		18
+#define CLK_USART2		19
+#define CLK_USART3		20
+#define CLK_UART4		21
+#define CLK_UART5		22
+#define CLK_USART6		23
+#define CLK_UART7		24
+#define CLK_UART8		25
+#define CLK_I2C1		26
+#define CLK_I2C2		27
+#define CLK_I2C3		28
+#define CLK_I2C4		29
+#define CLK_LPTIMER		30
+#define CLK_PLL_SRC		31
+#define CLK_DFSDM1		32
+#define CLK_ADFSDM1		33
+#define CLK_F769_DSI		34
+#define END_PRIMARY_CLK_F7	35
+
+#endif