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, 66 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/r8a73a4-clock.h b/include/dt-bindings/clock/r8a73a4-clock.h
new file mode 100644
index 000000000..028ecef81
--- /dev/null
+++ b/include/dt-bindings/clock/r8a73a4-clock.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright 2014 Ulrich Hecht
+ */
+
+#ifndef __DT_BINDINGS_CLOCK_R8A73A4_H__
+#define __DT_BINDINGS_CLOCK_R8A73A4_H__
+
+/* CPG */
+#define R8A73A4_CLK_MAIN	0
+#define R8A73A4_CLK_PLL0	1
+#define R8A73A4_CLK_PLL1	2
+#define R8A73A4_CLK_PLL2	3
+#define R8A73A4_CLK_PLL2S	4
+#define R8A73A4_CLK_PLL2H	5
+#define R8A73A4_CLK_Z		6
+#define R8A73A4_CLK_Z2		7
+#define R8A73A4_CLK_I		8
+#define R8A73A4_CLK_M3		9
+#define R8A73A4_CLK_B		10
+#define R8A73A4_CLK_M1		11
+#define R8A73A4_CLK_M2		12
+#define R8A73A4_CLK_ZX		13
+#define R8A73A4_CLK_ZS		14
+#define R8A73A4_CLK_HP		15
+#define R8A73A4_CLK_ZTR		16
+#define R8A73A4_CLK_ZT		17
+
+/* MSTP1 */
+#define R8A73A4_CLK_TMU0	25
+#define R8A73A4_CLK_TMU3	21
+
+/* MSTP2 */
+#define R8A73A4_CLK_DMAC	18
+#define R8A73A4_CLK_SCIFB3	17
+#define R8A73A4_CLK_SCIFB2	16
+#define R8A73A4_CLK_SCIFB1	7
+#define R8A73A4_CLK_SCIFB0	6
+#define R8A73A4_CLK_SCIFA0	4
+#define R8A73A4_CLK_SCIFA1	3
+
+/* MSTP3 */
+#define R8A73A4_CLK_CMT1	29
+#define R8A73A4_CLK_IIC1	23
+#define R8A73A4_CLK_IIC0	18
+#define R8A73A4_CLK_IIC7	17
+#define R8A73A4_CLK_IIC6	16
+#define R8A73A4_CLK_MMCIF0	15
+#define R8A73A4_CLK_SDHI0	14
+#define R8A73A4_CLK_SDHI1	13
+#define R8A73A4_CLK_SDHI2	12
+#define R8A73A4_CLK_MMCIF1	5
+#define R8A73A4_CLK_IIC2	0
+
+/* MSTP4 */
+#define R8A73A4_CLK_IIC3	11
+#define R8A73A4_CLK_IIC4	10
+#define R8A73A4_CLK_IIC5	9
+#define R8A73A4_CLK_INTC_SYS	8
+#define R8A73A4_CLK_IRQC	7
+
+/* MSTP5 */
+#define R8A73A4_CLK_THERMAL	22
+#define R8A73A4_CLK_IIC8	15
+
+#endif /* __DT_BINDINGS_CLOCK_R8A73A4_H__ */