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/at91.h b/include/dt-bindings/clock/at91.h
new file mode 100644
index 000000000..f2a7b7d39
--- /dev/null
+++ b/include/dt-bindings/clock/at91.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * This header provides constants for AT91 pmc status.
+ *
+ * The constants defined in this header are being used in dts.
+ */
+
+#ifndef _DT_BINDINGS_CLK_AT91_H
+#define _DT_BINDINGS_CLK_AT91_H
+
+#define PMC_TYPE_CORE		0
+#define PMC_TYPE_SYSTEM		1
+#define PMC_TYPE_PERIPHERAL	2
+#define PMC_TYPE_GCK		3
+#define PMC_TYPE_PROGRAMMABLE	4
+
+#define PMC_SLOW		0
+#define PMC_MCK			1
+#define PMC_UTMI		2
+#define PMC_MAIN		3
+#define PMC_MCK2		4
+#define PMC_I2S0_MUX		5
+#define PMC_I2S1_MUX		6
+#define PMC_PLLACK		7
+#define PMC_PLLBCK		8
+#define PMC_AUDIOPLLCK		9
+#define PMC_AUDIOPINCK		10
+
+/* SAMA7G5 */
+#define PMC_CPUPLL		(PMC_MAIN + 1)
+#define PMC_SYSPLL		(PMC_MAIN + 2)
+#define PMC_DDRPLL		(PMC_MAIN + 3)
+#define PMC_IMGPLL		(PMC_MAIN + 4)
+#define PMC_BAUDPLL		(PMC_MAIN + 5)
+#define PMC_AUDIOPMCPLL		(PMC_MAIN + 6)
+#define PMC_AUDIOIOPLL		(PMC_MAIN + 7)
+#define PMC_ETHPLL		(PMC_MAIN + 8)
+#define PMC_CPU			(PMC_MAIN + 9)
+#define PMC_MCK1		(PMC_MAIN + 10)
+
+/* SAM9X7 */
+#define PMC_PLLADIV2		(PMC_MAIN + 11)
+#define PMC_LVDSPLL		(PMC_MAIN + 12)
+
+/* SAMA7D65 */
+#define PMC_MCK3		(PMC_MAIN + 13)
+#define PMC_MCK5		(PMC_MAIN + 14)
+
+#ifndef AT91_PMC_MOSCS
+#define AT91_PMC_MOSCS		0		/* MOSCS Flag */
+#define AT91_PMC_LOCKA		1		/* PLLA Lock */
+#define AT91_PMC_LOCKB		2		/* PLLB Lock */
+#define AT91_PMC_MCKRDY		3		/* Master Clock */
+#define AT91_PMC_LOCKU		6		/* UPLL Lock */
+#define AT91_PMC_PCKRDY(id)	(8 + (id))	/* Programmable Clock */
+#define AT91_PMC_MOSCSELS	16		/* Main Oscillator Selection */
+#define AT91_PMC_MOSCRCS	17		/* Main On-Chip RC */
+#define AT91_PMC_CFDEV		18		/* Clock Failure Detector Event */
+#define AT91_PMC_GCKRDY		24		/* Generated Clocks */
+#endif
+
+/* Slow clock. */
+#define SCKC_MD_SLCK		0
+#define SCKC_TD_SLCK		1
+
+#endif