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, 70 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/histb-clock.h b/include/dt-bindings/clock/histb-clock.h
new file mode 100644
index 000000000..e64e5770a
--- /dev/null
+++ b/include/dt-bindings/clock/histb-clock.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2016 HiSilicon Technologies Co., Ltd.
+ */
+
+#ifndef __DTS_HISTB_CLOCK_H
+#define __DTS_HISTB_CLOCK_H
+
+/* clocks provided by core CRG */
+#define HISTB_OSC_CLK			0
+#define HISTB_APB_CLK			1
+#define HISTB_AHB_CLK			2
+#define HISTB_UART1_CLK			3
+#define HISTB_UART2_CLK			4
+#define HISTB_UART3_CLK			5
+#define HISTB_I2C0_CLK			6
+#define HISTB_I2C1_CLK			7
+#define HISTB_I2C2_CLK			8
+#define HISTB_I2C3_CLK			9
+#define HISTB_I2C4_CLK			10
+#define HISTB_I2C5_CLK			11
+#define HISTB_SPI0_CLK			12
+#define HISTB_SPI1_CLK			13
+#define HISTB_SPI2_CLK			14
+#define HISTB_SCI_CLK			15
+#define HISTB_FMC_CLK			16
+#define HISTB_MMC_BIU_CLK		17
+#define HISTB_MMC_CIU_CLK		18
+#define HISTB_MMC_DRV_CLK		19
+#define HISTB_MMC_SAMPLE_CLK		20
+#define HISTB_SDIO0_BIU_CLK		21
+#define HISTB_SDIO0_CIU_CLK		22
+#define HISTB_SDIO0_DRV_CLK		23
+#define HISTB_SDIO0_SAMPLE_CLK		24
+#define HISTB_PCIE_AUX_CLK		25
+#define HISTB_PCIE_PIPE_CLK		26
+#define HISTB_PCIE_SYS_CLK		27
+#define HISTB_PCIE_BUS_CLK		28
+#define HISTB_ETH0_MAC_CLK		29
+#define HISTB_ETH0_MACIF_CLK		30
+#define HISTB_ETH1_MAC_CLK		31
+#define HISTB_ETH1_MACIF_CLK		32
+#define HISTB_COMBPHY1_CLK		33
+#define HISTB_USB2_BUS_CLK		34
+#define HISTB_USB2_PHY_CLK		35
+#define HISTB_USB2_UTMI_CLK		36
+#define HISTB_USB2_12M_CLK		37
+#define HISTB_USB2_48M_CLK		38
+#define HISTB_USB2_OTG_UTMI_CLK		39
+#define HISTB_USB2_PHY1_REF_CLK		40
+#define HISTB_USB2_PHY2_REF_CLK		41
+#define HISTB_COMBPHY0_CLK		42
+#define HISTB_USB3_BUS_CLK		43
+#define HISTB_USB3_UTMI_CLK		44
+#define HISTB_USB3_PIPE_CLK		45
+#define HISTB_USB3_SUSPEND_CLK		46
+#define HISTB_USB3_BUS_CLK1		47
+#define HISTB_USB3_UTMI_CLK1		48
+#define HISTB_USB3_PIPE_CLK1		49
+#define HISTB_USB3_SUSPEND_CLK1		50
+
+/* clocks provided by mcu CRG */
+#define HISTB_MCE_CLK			1
+#define HISTB_IR_CLK			2
+#define HISTB_TIMER01_CLK		3
+#define HISTB_LEDC_CLK			4
+#define HISTB_UART0_CLK			5
+#define HISTB_LSADC_CLK			6
+
+#endif	/* __DTS_HISTB_CLOCK_H */