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, 62 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/bcm2835.h b/include/dt-bindings/clock/bcm2835.h
new file mode 100644
index 000000000..b60c03430
--- /dev/null
+++ b/include/dt-bindings/clock/bcm2835.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2015 Broadcom Corporation
+ */
+
+#define BCM2835_PLLA			0
+#define BCM2835_PLLB			1
+#define BCM2835_PLLC			2
+#define BCM2835_PLLD			3
+#define BCM2835_PLLH			4
+
+#define BCM2835_PLLA_CORE		5
+#define BCM2835_PLLA_PER		6
+#define BCM2835_PLLB_ARM		7
+#define BCM2835_PLLC_CORE0		8
+#define BCM2835_PLLC_CORE1		9
+#define BCM2835_PLLC_CORE2		10
+#define BCM2835_PLLC_PER		11
+#define BCM2835_PLLD_CORE		12
+#define BCM2835_PLLD_PER		13
+#define BCM2835_PLLH_RCAL		14
+#define BCM2835_PLLH_AUX		15
+#define BCM2835_PLLH_PIX		16
+
+#define BCM2835_CLOCK_TIMER		17
+#define BCM2835_CLOCK_OTP		18
+#define BCM2835_CLOCK_UART		19
+#define BCM2835_CLOCK_VPU		20
+#define BCM2835_CLOCK_V3D		21
+#define BCM2835_CLOCK_ISP		22
+#define BCM2835_CLOCK_H264		23
+#define BCM2835_CLOCK_VEC		24
+#define BCM2835_CLOCK_HSM		25
+#define BCM2835_CLOCK_SDRAM		26
+#define BCM2835_CLOCK_TSENS		27
+#define BCM2835_CLOCK_EMMC		28
+#define BCM2835_CLOCK_PERI_IMAGE	29
+#define BCM2835_CLOCK_PWM		30
+#define BCM2835_CLOCK_PCM		31
+
+#define BCM2835_PLLA_DSI0		32
+#define BCM2835_PLLA_CCP2		33
+#define BCM2835_PLLD_DSI0		34
+#define BCM2835_PLLD_DSI1		35
+
+#define BCM2835_CLOCK_AVEO		36
+#define BCM2835_CLOCK_DFT		37
+#define BCM2835_CLOCK_GP0		38
+#define BCM2835_CLOCK_GP1		39
+#define BCM2835_CLOCK_GP2		40
+#define BCM2835_CLOCK_SLIM		41
+#define BCM2835_CLOCK_SMI		42
+#define BCM2835_CLOCK_TEC		43
+#define BCM2835_CLOCK_DPI		44
+#define BCM2835_CLOCK_CAM0		45
+#define BCM2835_CLOCK_CAM1		46
+#define BCM2835_CLOCK_DSI0E		47
+#define BCM2835_CLOCK_DSI1E		48
+#define BCM2835_CLOCK_DSI0P		49
+#define BCM2835_CLOCK_DSI1P		50
+
+#define BCM2711_CLOCK_EMMC2		51