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, 42 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/dm814.h b/include/dt-bindings/clock/dm814.h
new file mode 100644
index 000000000..33b8826d9
--- /dev/null
+++ b/include/dt-bindings/clock/dm814.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2017 Texas Instruments, Inc.
+ */
+#ifndef __DT_BINDINGS_CLK_DM814_H
+#define __DT_BINDINGS_CLK_DM814_H
+
+#define DM814_CLKCTRL_OFFSET	0x0
+#define DM814_CLKCTRL_INDEX(offset)	((offset) - DM814_CLKCTRL_OFFSET)
+
+/* default clocks */
+#define DM814_USB_OTG_HS_CLKCTRL	DM814_CLKCTRL_INDEX(0x58)
+
+/* alwon clocks */
+#define DM814_UART1_CLKCTRL	DM814_CLKCTRL_INDEX(0x150)
+#define DM814_UART2_CLKCTRL	DM814_CLKCTRL_INDEX(0x154)
+#define DM814_UART3_CLKCTRL	DM814_CLKCTRL_INDEX(0x158)
+#define DM814_GPIO1_CLKCTRL	DM814_CLKCTRL_INDEX(0x15c)
+#define DM814_GPIO2_CLKCTRL	DM814_CLKCTRL_INDEX(0x160)
+#define DM814_I2C1_CLKCTRL	DM814_CLKCTRL_INDEX(0x164)
+#define DM814_I2C2_CLKCTRL	DM814_CLKCTRL_INDEX(0x168)
+#define DM814_WD_TIMER_CLKCTRL	DM814_CLKCTRL_INDEX(0x18c)
+#define DM814_MCSPI1_CLKCTRL	DM814_CLKCTRL_INDEX(0x190)
+#define DM814_GPMC_CLKCTRL	DM814_CLKCTRL_INDEX(0x1d0)
+#define DM814_CPGMAC0_CLKCTRL	DM814_CLKCTRL_INDEX(0x1d4)
+#define DM814_MPU_CLKCTRL	DM814_CLKCTRL_INDEX(0x1dc)
+#define DM814_RTC_CLKCTRL	DM814_CLKCTRL_INDEX(0x1f0)
+#define DM814_TPCC_CLKCTRL	DM814_CLKCTRL_INDEX(0x1f4)
+#define DM814_TPTC0_CLKCTRL	DM814_CLKCTRL_INDEX(0x1f8)
+#define DM814_TPTC1_CLKCTRL	DM814_CLKCTRL_INDEX(0x1fc)
+#define DM814_TPTC2_CLKCTRL	DM814_CLKCTRL_INDEX(0x200)
+#define DM814_TPTC3_CLKCTRL	DM814_CLKCTRL_INDEX(0x204)
+#define DM814_MMC1_CLKCTRL	DM814_CLKCTRL_INDEX(0x21c)
+#define DM814_MMC2_CLKCTRL	DM814_CLKCTRL_INDEX(0x220)
+#define DM814_MMC3_CLKCTRL	DM814_CLKCTRL_INDEX(0x224)
+
+/* alwon_ethernet clocks */
+#define DM814_ETHERNET_CLKCTRL_OFFSET	0x1d4
+#define DM814_ETHERNET_CLKCTRL_INDEX(offset)	((offset) - DM814_ETHERNET_CLKCTRL_OFFSET)
+#define DM814_ETHERNET_CPGMAC0_CLKCTRL	DM814_ETHERNET_CLKCTRL_INDEX(0x1d4)
+
+#endif