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, 45 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/dm816.h b/include/dt-bindings/clock/dm816.h
new file mode 100644
index 000000000..fb0d94174
--- /dev/null
+++ b/include/dt-bindings/clock/dm816.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2017 Texas Instruments, Inc.
+ */
+#ifndef __DT_BINDINGS_CLK_DM816_H
+#define __DT_BINDINGS_CLK_DM816_H
+
+#define DM816_CLKCTRL_OFFSET	0x0
+#define DM816_CLKCTRL_INDEX(offset)	((offset) - DM816_CLKCTRL_OFFSET)
+
+/* default clocks */
+#define DM816_USB_OTG_HS_CLKCTRL	DM816_CLKCTRL_INDEX(0x58)
+
+/* alwon clocks */
+#define DM816_UART1_CLKCTRL	DM816_CLKCTRL_INDEX(0x150)
+#define DM816_UART2_CLKCTRL	DM816_CLKCTRL_INDEX(0x154)
+#define DM816_UART3_CLKCTRL	DM816_CLKCTRL_INDEX(0x158)
+#define DM816_GPIO1_CLKCTRL	DM816_CLKCTRL_INDEX(0x15c)
+#define DM816_GPIO2_CLKCTRL	DM816_CLKCTRL_INDEX(0x160)
+#define DM816_I2C1_CLKCTRL	DM816_CLKCTRL_INDEX(0x164)
+#define DM816_I2C2_CLKCTRL	DM816_CLKCTRL_INDEX(0x168)
+#define DM816_TIMER1_CLKCTRL	DM816_CLKCTRL_INDEX(0x170)
+#define DM816_TIMER2_CLKCTRL	DM816_CLKCTRL_INDEX(0x174)
+#define DM816_TIMER3_CLKCTRL	DM816_CLKCTRL_INDEX(0x178)
+#define DM816_TIMER4_CLKCTRL	DM816_CLKCTRL_INDEX(0x17c)
+#define DM816_TIMER5_CLKCTRL	DM816_CLKCTRL_INDEX(0x180)
+#define DM816_TIMER6_CLKCTRL	DM816_CLKCTRL_INDEX(0x184)
+#define DM816_TIMER7_CLKCTRL	DM816_CLKCTRL_INDEX(0x188)
+#define DM816_WD_TIMER_CLKCTRL	DM816_CLKCTRL_INDEX(0x18c)
+#define DM816_MCSPI1_CLKCTRL	DM816_CLKCTRL_INDEX(0x190)
+#define DM816_MAILBOX_CLKCTRL	DM816_CLKCTRL_INDEX(0x194)
+#define DM816_SPINBOX_CLKCTRL	DM816_CLKCTRL_INDEX(0x198)
+#define DM816_MMC1_CLKCTRL	DM816_CLKCTRL_INDEX(0x1b0)
+#define DM816_GPMC_CLKCTRL	DM816_CLKCTRL_INDEX(0x1d0)
+#define DM816_DAVINCI_MDIO_CLKCTRL	DM816_CLKCTRL_INDEX(0x1d4)
+#define DM816_EMAC1_CLKCTRL	DM816_CLKCTRL_INDEX(0x1d8)
+#define DM816_MPU_CLKCTRL	DM816_CLKCTRL_INDEX(0x1dc)
+#define DM816_RTC_CLKCTRL	DM816_CLKCTRL_INDEX(0x1f0)
+#define DM816_TPCC_CLKCTRL	DM816_CLKCTRL_INDEX(0x1f4)
+#define DM816_TPTC0_CLKCTRL	DM816_CLKCTRL_INDEX(0x1f8)
+#define DM816_TPTC1_CLKCTRL	DM816_CLKCTRL_INDEX(0x1fc)
+#define DM816_TPTC2_CLKCTRL	DM816_CLKCTRL_INDEX(0x200)
+#define DM816_TPTC3_CLKCTRL	DM816_CLKCTRL_INDEX(0x204)
+
+#endif