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, 77 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/mpc512x-clock.h b/include/dt-bindings/clock/mpc512x-clock.h
new file mode 100644
index 000000000..13c316bf2
--- /dev/null
+++ b/include/dt-bindings/clock/mpc512x-clock.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This header provides constants for MPC512x clock specs in DT bindings.
+ */
+
+#ifndef _DT_BINDINGS_CLOCK_MPC512x_CLOCK_H
+#define _DT_BINDINGS_CLOCK_MPC512x_CLOCK_H
+
+#define MPC512x_CLK_DUMMY		0
+#define MPC512x_CLK_REF			1
+#define MPC512x_CLK_SYS			2
+#define MPC512x_CLK_DIU			3
+#define MPC512x_CLK_VIU			4
+#define MPC512x_CLK_CSB			5
+#define MPC512x_CLK_E300		6
+#define MPC512x_CLK_IPS			7
+#define MPC512x_CLK_FEC			8
+#define MPC512x_CLK_SATA		9
+#define MPC512x_CLK_PATA		10
+#define MPC512x_CLK_NFC			11
+#define MPC512x_CLK_LPC			12
+#define MPC512x_CLK_MBX_BUS		13
+#define MPC512x_CLK_MBX			14
+#define MPC512x_CLK_MBX_3D		15
+#define MPC512x_CLK_AXE			16
+#define MPC512x_CLK_USB1		17
+#define MPC512x_CLK_USB2		18
+#define MPC512x_CLK_I2C			19
+#define MPC512x_CLK_MSCAN0_MCLK		20
+#define MPC512x_CLK_MSCAN1_MCLK		21
+#define MPC512x_CLK_MSCAN2_MCLK		22
+#define MPC512x_CLK_MSCAN3_MCLK		23
+#define MPC512x_CLK_BDLC		24
+#define MPC512x_CLK_SDHC		25
+#define MPC512x_CLK_PCI			26
+#define MPC512x_CLK_PSC_MCLK_IN		27
+#define MPC512x_CLK_SPDIF_TX		28
+#define MPC512x_CLK_SPDIF_RX		29
+#define MPC512x_CLK_SPDIF_MCLK		30
+#define MPC512x_CLK_SPDIF		31
+#define MPC512x_CLK_AC97		32
+#define MPC512x_CLK_PSC0_MCLK		33
+#define MPC512x_CLK_PSC1_MCLK		34
+#define MPC512x_CLK_PSC2_MCLK		35
+#define MPC512x_CLK_PSC3_MCLK		36
+#define MPC512x_CLK_PSC4_MCLK		37
+#define MPC512x_CLK_PSC5_MCLK		38
+#define MPC512x_CLK_PSC6_MCLK		39
+#define MPC512x_CLK_PSC7_MCLK		40
+#define MPC512x_CLK_PSC8_MCLK		41
+#define MPC512x_CLK_PSC9_MCLK		42
+#define MPC512x_CLK_PSC10_MCLK		43
+#define MPC512x_CLK_PSC11_MCLK		44
+#define MPC512x_CLK_PSC_FIFO		45
+#define MPC512x_CLK_PSC0		46
+#define MPC512x_CLK_PSC1		47
+#define MPC512x_CLK_PSC2		48
+#define MPC512x_CLK_PSC3		49
+#define MPC512x_CLK_PSC4		50
+#define MPC512x_CLK_PSC5		51
+#define MPC512x_CLK_PSC6		52
+#define MPC512x_CLK_PSC7		53
+#define MPC512x_CLK_PSC8		54
+#define MPC512x_CLK_PSC9		55
+#define MPC512x_CLK_PSC10		56
+#define MPC512x_CLK_PSC11		57
+#define MPC512x_CLK_SDHC2		58
+#define MPC512x_CLK_FEC2		59
+#define MPC512x_CLK_OUT0_CLK		60
+#define MPC512x_CLK_OUT1_CLK		61
+#define MPC512x_CLK_OUT2_CLK		62
+#define MPC512x_CLK_OUT3_CLK		63
+#define MPC512x_CLK_CAN_CLK_IN		64
+
+#define MPC512x_CLK_LAST_PUBLIC		64
+
+#endif