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, 36 insertions, 0 deletions

diff --git a/drivers/interconnect/mediatek/Kconfig b/drivers/interconnect/mediatek/Kconfig
new file mode 100644
index 000000000..9fd3f2170
--- /dev/null
+++ b/drivers/interconnect/mediatek/Kconfig
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config INTERCONNECT_MTK
+	bool "MediaTek interconnect drivers"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	help
+	  Support for MediaTek's bus interconnect hardware.
+
+config INTERCONNECT_MTK_DVFSRC_EMI
+	tristate "MediaTek DVFSRC EMI interconnect driver"
+	depends on INTERCONNECT_MTK && MTK_DVFSRC
+	help
+	  This is a driver for the MediaTek External Memory Interface
+	  interconnect on SoCs equipped with the integrated Dynamic
+	  Voltage Frequency Scaling Resource Collector (DVFSRC) MCU
+
+config INTERCONNECT_MTK_MT8183
+	tristate "MediaTek MT8183 interconnect driver"
+	depends on INTERCONNECT_MTK_DVFSRC_EMI
+	help
+	  This is a driver for the MediaTek bus interconnect on MT8183-based
+	  platforms.
+
+config INTERCONNECT_MTK_MT8195
+	tristate "MediaTek MT8195 interconnect driver"
+	depends on INTERCONNECT_MTK_DVFSRC_EMI
+	help
+	  This is a driver for the MediaTek bus interconnect on MT8195-based
+	  platforms.
+
+config INTERCONNECT_MTK_MT8196
+	tristate "MediaTek MT8196 interconnect driver"
+	depends on INTERCONNECT_MTK_DVFSRC_EMI
+	help
+	  This is a driver for the MediaTek bus interconnect on MT8196-based
+	  platforms.