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, 118 insertions, 0 deletions

diff --git a/drivers/bcma/Kconfig b/drivers/bcma/Kconfig
new file mode 100644
index 000000000..b9558ff20
--- /dev/null
+++ b/drivers/bcma/Kconfig
@@ -0,0 +1,118 @@
+# SPDX-License-Identifier: GPL-2.0
+config BCMA_POSSIBLE
+	bool
+	depends on HAS_IOMEM && HAS_DMA
+	default y
+
+menuconfig BCMA
+	tristate "Broadcom specific AMBA"
+	depends on BCMA_POSSIBLE
+	help
+	  Bus driver for Broadcom specific Advanced Microcontroller Bus
+	  Architecture.
+
+if BCMA
+
+# Support for Block-I/O. SELECT this from the driver that needs it.
+config BCMA_BLOCKIO
+	bool
+
+config BCMA_HOST_PCI_POSSIBLE
+	bool
+	depends on PCI = y
+	default y
+
+config BCMA_HOST_PCI
+	bool "Support for BCMA on PCI-host bus"
+	depends on BCMA_HOST_PCI_POSSIBLE
+	select BCMA_DRIVER_PCI
+	default y
+
+config BCMA_HOST_SOC
+	bool "Support for BCMA in a SoC"
+	depends on HAS_IOMEM
+	help
+	  Host interface for a Broadcom AIX bus directly mapped into
+	  the memory. This only works with the Broadcom SoCs from the
+	  BCM47XX line.
+
+	  If unsure, say N
+
+config BCMA_DRIVER_PCI
+	bool "BCMA Broadcom PCI core driver"
+	depends on PCI
+	default y
+	help
+	  BCMA bus may have many versions of PCIe core. This driver
+	  supports:
+	  1) PCIe core working in clientmode
+	  2) PCIe Gen 2 clientmode core
+
+	  In general PCIe (Gen 2) clientmode core is required on PCIe
+	  hosted buses. It's responsible for initialization and basic
+	  hardware management.
+	  This driver is also prerequisite for a hostmode PCIe core
+	  support.
+
+config BCMA_DRIVER_PCI_HOSTMODE
+	bool "Driver for PCI core working in hostmode"
+	depends on MIPS && BCMA_DRIVER_PCI && PCI_DRIVERS_LEGACY && BCMA = y
+	help
+	  PCI core hostmode operation (external PCI bus).
+
+config BCMA_DRIVER_MIPS
+	bool "BCMA Broadcom MIPS core driver"
+	depends on MIPS || COMPILE_TEST
+	help
+	  Driver for the Broadcom MIPS core attached to Broadcom specific
+	  Advanced Microcontroller Bus.
+
+	  If unsure, say N
+
+config BCMA_PFLASH
+	bool
+	depends on BCMA_DRIVER_MIPS
+	default y
+
+config BCMA_SFLASH
+	bool "ChipCommon-attached serial flash support"
+	depends on BCMA_HOST_SOC
+	default y
+	help
+	  Some cheap devices have serial flash connected to the ChipCommon
+	  instead of independent SPI controller. It requires using a separated
+	  driver that implements ChipCommon specific interface communication.
+
+	  Enabling this symbol will let bcma recognize serial flash and register
+	  it as platform device.
+
+config BCMA_NFLASH
+	bool
+	depends on BCMA_DRIVER_MIPS
+	default y
+
+config BCMA_DRIVER_GMAC_CMN
+	bool "BCMA Broadcom GBIT MAC COMMON core driver"
+	help
+	  Driver for the Broadcom GBIT MAC COMMON core attached to Broadcom
+	  specific Advanced Microcontroller Bus.
+
+	  If unsure, say N
+
+config BCMA_DRIVER_GPIO
+	bool "BCMA GPIO driver"
+	depends on GPIOLIB
+	select GPIOLIB_IRQCHIP if BCMA_HOST_SOC
+	help
+	  Driver to provide access to the GPIO pins of the bcma bus.
+
+	  If unsure, say N
+
+config BCMA_DEBUG
+	bool "BCMA debugging"
+	help
+	  This turns on additional debugging messages.
+
+	  If unsure, say N
+
+endif # BCMA