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, 113 insertions, 0 deletions

diff --git a/drivers/misc/mei/Kconfig b/drivers/misc/mei/Kconfig
new file mode 100644
index 000000000..2d1bc5b4d
--- /dev/null
+++ b/drivers/misc/mei/Kconfig
@@ -0,0 +1,113 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2003-2019, Intel Corporation. All rights reserved.
+config INTEL_MEI
+	tristate "Intel Management Engine Interface"
+	depends on PCI
+	depends on X86 || DRM_XE!=n || COMPILE_TEST
+	default X86_64 || MATOM
+	help
+	  The Intel Management Engine (Intel ME) provides Manageability,
+	  Security and Media services for system containing Intel chipsets.
+	  if selected /dev/mei misc device will be created.
+
+	  For more information see
+	  <https://software.intel.com/en-us/manageability/>
+
+if INTEL_MEI
+
+config INTEL_MEI_ME
+	tristate "ME Enabled Intel Chipsets"
+	default y
+	help
+	  MEI support for ME Enabled Intel chipsets.
+
+	  Supported Chipsets are:
+	  7 Series Chipset Family
+	  6 Series Chipset Family
+	  5 Series Chipset Family
+	  4 Series Chipset Family
+	  Mobile 4 Series Chipset Family
+	  ICH9
+	  82946GZ/GL
+	  82G35 Express
+	  82Q963/Q965
+	  82P965/G965
+	  Mobile PM965/GM965
+	  Mobile GME965/GLE960
+	  82Q35 Express
+	  82G33/G31/P35/P31 Express
+	  82Q33 Express
+	  82X38/X48 Express
+
+config INTEL_MEI_TXE
+	tristate "Intel Trusted Execution Environment with ME Interface"
+	help
+	  MEI Support for Trusted Execution Environment device on Intel SoCs
+
+	  Supported SoCs:
+	  Intel Bay Trail
+
+config INTEL_MEI_GSC
+	tristate "Intel MEI GSC embedded device"
+	depends on INTEL_MEI_ME
+	depends on DRM_I915!=n || DRM_XE!=n || COMPILE_TEST
+	help
+	  Intel auxiliary driver for GSC devices embedded in Intel graphics devices.
+
+	  An MEI device here called GSC can be embedded in an
+	  Intel graphics devices, to support a range of chassis
+	  tasks such as graphics card firmware update and security
+	  tasks.
+
+config INTEL_MEI_CSC
+	tristate "Intel MEI CSC embedded device"
+	depends on INTEL_MEI_ME
+	help
+	  Intel PCI driver for the chassis controller embedded in Intel graphics devices.
+
+	  An MEI device here called CSC can be embedded in discrete
+	  Intel graphics devices, to support a range of chassis
+	  tasks such as graphics card firmware update and security
+	  tasks.
+
+config INTEL_MEI_VSC_HW
+	tristate "Intel visual sensing controller device transport driver"
+	depends on ACPI && SPI
+	depends on GPIOLIB || COMPILE_TEST
+	help
+	  Intel SPI transport driver between host and Intel visual sensing
+	  controller (IVSC) device.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called mei-vsc-hw.
+
+config INTEL_MEI_VSC
+	tristate "Intel visual sensing controller device with ME interface"
+	depends on INTEL_MEI_VSC_HW
+	help
+	  Intel MEI over SPI driver for Intel visual sensing controller
+	  (IVSC) device embedded in IA platform. It supports camera sharing
+	  between IVSC for context sensing and IPU for typical media usage.
+	  Select this config should enable transport layer for IVSC device.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called mei-vsc.
+
+config INTEL_MEI_LB
+	tristate "Intel Late Binding (LB) support on ME Interface"
+	depends on INTEL_MEI_ME
+	depends on DRM_XE!=n || COMPILE_TEST
+	help
+	  Enable support for Intel Late Binding (LB) via the MEI interface.
+
+	  Late Binding is a method for applying firmware updates at runtime,
+	  allowing the Intel Xe driver to load firmware payloads such as
+	  fan controller or voltage regulator. These firmware updates are
+	  authenticated and versioned, and do not require firmware flashing
+	  or system reboot.
+
+source "drivers/misc/mei/hdcp/Kconfig"
+source "drivers/misc/mei/pxp/Kconfig"
+source "drivers/misc/mei/gsc_proxy/Kconfig"
+
+endif