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, 51 insertions, 0 deletions

diff --git a/drivers/usb/common/Kconfig b/drivers/usb/common/Kconfig
new file mode 100644
index 000000000..b85662243
--- /dev/null
+++ b/drivers/usb/common/Kconfig
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config USB_COMMON
+	tristate
+
+
+config USB_LED_TRIG
+	bool "USB LED Triggers"
+	depends on LEDS_CLASS && USB_COMMON && LEDS_TRIGGERS
+	help
+	  This option adds LED triggers for USB host and/or gadget activity.
+
+	  Say Y here if you are working on a system with led-class supported
+	  LEDs and you want to use them as activity indicators for USB host or
+	  gadget.
+
+config USB_ULPI_BUS
+	tristate "USB ULPI PHY interface support"
+	select USB_COMMON
+	help
+	  UTMI+ Low Pin Interface (ULPI) is specification for a commonly used
+	  USB 2.0 PHY interface. The ULPI specification defines a standard set
+	  of registers that can be used to detect the vendor and product which
+	  allows ULPI to be handled as a bus. This module is the driver for that
+	  bus.
+
+	  The ULPI interfaces (the buses) are registered by the drivers for USB
+	  controllers which support ULPI register access and have ULPI PHY
+	  attached to them. The ULPI PHY drivers themselves are normal PHY
+	  drivers.
+
+	  ULPI PHYs provide often functions such as ADP sensing/probing (OTG
+	  protocol) and USB charger detection.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called ulpi.
+
+config USB_CONN_GPIO
+	tristate "USB GPIO Based Connection Detection Driver"
+	depends on GPIOLIB
+	select USB_ROLE_SWITCH
+	select POWER_SUPPLY
+	help
+	  The driver supports USB role switch between host and device via GPIO
+	  based USB cable detection, used typically if an input GPIO is used
+	  to detect USB ID pin, and another input GPIO may be also used to detect
+	  Vbus pin at the same time, it also can be used to enable/disable
+	  device if an input GPIO is only used to detect Vbus pin.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called usb-conn-gpio.ko