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, 92 insertions, 0 deletions

diff --git a/drivers/soc/mediatek/Kconfig b/drivers/soc/mediatek/Kconfig
new file mode 100644
index 000000000..d7293977f
--- /dev/null
+++ b/drivers/soc/mediatek/Kconfig
@@ -0,0 +1,92 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# MediaTek SoC drivers
+#
+menu "MediaTek SoC drivers"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+
+config MTK_CMDQ
+	tristate "MediaTek CMDQ Support"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	select MAILBOX
+	select MTK_CMDQ_MBOX
+	select MTK_INFRACFG
+	help
+	  Say yes here to add support for the MediaTek Command Queue (CMDQ)
+	  driver. The CMDQ is used to help read/write registers with critical
+	  time limitation, such as updating display configuration during the
+	  vblank.
+
+config MTK_DEVAPC
+	tristate "Mediatek Device APC Support"
+	help
+	  Say yes here to enable support for Mediatek Device APC driver.
+	  This driver is mainly used to handle the violation which catches
+	  unexpected transaction.
+	  The violation information is logged for further analysis or
+	  countermeasures.
+
+config MTK_DVFSRC
+	tristate "MediaTek DVFSRC Support"
+	depends on ARCH_MEDIATEK
+	help
+	  Say yes here to add support for the MediaTek Dynamic Voltage
+	  and Frequency Scaling Resource Collector (DVFSRC): a HW
+	  IP found on many MediaTek SoCs, which is responsible for
+	  collecting DVFS requests from various SoC IPs, other than
+	  software, and performing bandwidth scaling to provide the
+	  best achievable performance-per-watt.
+
+config MTK_INFRACFG
+	bool "MediaTek INFRACFG Support"
+	select REGMAP
+	help
+	  Say yes here to add support for the MediaTek INFRACFG controller. The
+	  INFRACFG controller contains various infrastructure registers not
+	  directly associated to any device.
+
+config MTK_PMIC_WRAP
+	tristate "MediaTek PMIC Wrapper Support"
+	depends on RESET_CONTROLLER
+	depends on OF
+	select REGMAP
+	help
+	  Say yes here to add support for MediaTek PMIC Wrapper found
+	  on different MediaTek SoCs. The PMIC wrapper is a proprietary
+	  hardware to connect the PMIC.
+
+config MTK_REGULATOR_COUPLER
+	bool "MediaTek SoC Regulator Coupler" if COMPILE_TEST
+	default ARCH_MEDIATEK
+	depends on REGULATOR
+
+config MTK_MMSYS
+	tristate "MediaTek MMSYS Support"
+	default ARCH_MEDIATEK
+	depends on HAS_IOMEM
+	depends on MTK_CMDQ || MTK_CMDQ=n
+	help
+	  Say yes here to add support for the MediaTek Multimedia
+	  Subsystem (MMSYS).
+
+config MTK_SVS
+	tristate "MediaTek Smart Voltage Scaling(SVS)"
+	depends on NVMEM_MTK_EFUSE && NVMEM
+	help
+	  The Smart Voltage Scaling(SVS) engine is a piece of hardware
+	  which has several controllers(banks) for calculating suitable
+	  voltage to different power domains(CPU/GPU/CCI) according to
+	  chip process corner, temperatures and other factors. Then DVFS
+	  driver could apply SVS bank voltage to PMIC/Buck.
+
+config MTK_SOCINFO
+	tristate "MediaTek SoC Information"
+	default y
+	depends on NVMEM_MTK_EFUSE
+	select SOC_BUS
+	help
+	  The MediaTek SoC Information (mtk-socinfo) driver provides
+	  information about the SoC to the userspace including the
+	  manufacturer name, marketing name and soc name.
+
+endmenu