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, 115 insertions, 0 deletions

diff --git a/drivers/usb/cdns3/Kconfig b/drivers/usb/cdns3/Kconfig
new file mode 100644
index 000000000..39ad23d1a
--- /dev/null
+++ b/drivers/usb/cdns3/Kconfig
@@ -0,0 +1,115 @@
+config USB_CDNS_SUPPORT
+	tristate "Cadence USB Support"
+	depends on USB_SUPPORT && HAS_DMA
+	depends on USB || USB_GADGET
+	depends on USB if !USB_GADGET
+	depends on USB_GADGET if !USB
+	select USB_XHCI_PLATFORM if USB_XHCI_HCD
+	select USB_ROLE_SWITCH
+	help
+	  Say Y here if your system has a Cadence USBSS or USBSSP
+	  dual-role controller.
+	  It supports: dual-role switch, Host-only, and Peripheral-only.
+
+if USB_CDNS_SUPPORT
+
+config USB_CDNS3
+	tristate "Cadence USB dual-role controller (USBSS and USBSSP)"
+	depends on USB_CDNS_SUPPORT
+	help
+	  Say Y or M here if your system has an on-chip Cadence USB
+	  dual-role controller. This covers both USBSS (USB 3.0) and
+	  USBSSP (SuperSpeed Plus) IP; the driver detects the variant at
+	  runtime.
+
+	  The core driver (core, DRD, generic platform binding for the
+	  "cdns,usb3" device tree compatible, optional host and gadget)
+	  builds as one module named cdns.ko when built as a loadable
+	  module.
+
+	  It supports: dual-role switch, Host-only, and Peripheral-only.
+
+if USB_CDNS3
+
+config USB_CDNS3_HOST
+	bool "Cadence USB host controller (xHCI)"
+	depends on USB=y || USB=USB_CDNS3
+	help
+	  Say Y here to enable host controller functionality for Cadence
+	  USBSS and USBSSP dual-role controllers.
+
+	  The host controller is xHCI compliant and uses the standard
+	  xHCI driver.
+
+config USB_CDNS3_GADGET
+	bool "Cadence USB device controller (USBSS and USBSSP)"
+	depends on USB_GADGET=y || USB_GADGET=USB_CDNS3
+	help
+	  Say Y here to include Cadence USB device (gadget) support for
+	  both USBSS (USB 3.0) and USBSSP (SuperSpeed Plus) IP in the
+	  cdns.ko module. The implementation is selected at runtime from
+	  the detected controller version.
+
+	  USBSS gadget supports FF, HS and SS mode (not LS or SSP).
+	  USBSSP gadget supports FF, HS, SS and SSP mode (not LS).
+
+comment "Platform glue driver support"
+
+config USB_CDNS3_PCI_WRAP
+	tristate "Cadence USB3 support on PCIe-based platforms"
+	depends on USB_PCI && ACPI
+	default USB_CDNS3
+	help
+	  If you're using the USBSS Core IP with a PCIe, please say
+	  'Y' or 'M' here.
+
+	  If you choose to build this driver as module it will
+	  be dynamically linked and module will be called cdns3-pci.ko
+
+config USB_CDNSP_PCI
+	tristate "Cadence USBSSP support on PCIe-based platforms"
+	depends on USB_PCI && ACPI
+	default USB_CDNS3
+	help
+	  If you're using the USBSSP Core IP with a PCIe, please say
+	  'Y' or 'M' here.
+
+	  If you choose to build this driver as module it will
+	  be dynamically linked and module will be called cdnsp-pci.ko
+
+config USB_CDNS3_TI
+	tristate "Cadence USB3 support on TI platforms"
+	depends on ARCH_K3 || COMPILE_TEST
+	default USB_CDNS3
+	help
+	  Say 'Y' or 'M' here if you are building for Texas Instruments
+	  platforms that contain Cadence USB3 controller core.
+
+	  e.g. J721e.
+
+config USB_CDNS3_IMX
+	tristate "Cadence USB3 support on NXP i.MX platforms"
+	depends on ARCH_MXC || COMPILE_TEST
+	default USB_CDNS3
+	help
+	  Say 'Y' or 'M' here if you are building for NXP i.MX
+	  platforms that contain Cadence USB3 controller core.
+
+	  For example, imx8qm and imx8qxp.
+
+config USB_CDNS3_STARFIVE
+	tristate "Cadence USB3 support on StarFive SoC platforms"
+	depends on ARCH_STARFIVE || COMPILE_TEST
+	default USB_CDNS3
+	help
+	  Say 'Y' or 'M' here if you are building for StarFive SoCs
+	  platforms that contain Cadence USB3 controller core.
+
+	  e.g. JH7110.
+
+	  If you choose to build this driver as module it will
+	  be dynamically linked and module will be called cdns3-starfive.ko
+
+endif # USB_CDNS3
+
+endif # USB_CDNS_SUPPORT