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, 63 insertions, 0 deletions

diff --git a/drivers/soundwire/Kconfig b/drivers/soundwire/Kconfig
new file mode 100644
index 000000000..196a7daaa
--- /dev/null
+++ b/drivers/soundwire/Kconfig
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# SoundWire subsystem configuration
+#
+
+menuconfig SOUNDWIRE
+	tristate "SoundWire support"
+	depends on ACPI || OF
+	depends on SND_SOC_SDCA_OPTIONAL
+	help
+	  SoundWire is a 2-Pin interface with data and clock line ratified
+	  by the MIPI Alliance. SoundWire is used for transporting data
+	  typically related to audio functions. SoundWire interface is
+	  optimized to integrate audio devices in mobile or mobile inspired
+	  systems. Say Y to enable this subsystem, N if you do not have such
+	  a device
+
+if SOUNDWIRE
+
+comment "SoundWire Devices"
+
+config SOUNDWIRE_AMD
+	tristate "AMD SoundWire Manager driver"
+	select SOUNDWIRE_GENERIC_ALLOCATION
+	depends on ACPI && SND_SOC
+	help
+	  SoundWire AMD Manager driver.
+	  If you have an AMD platform which has a SoundWire Manager then
+	  enable this config option to get the SoundWire support for that
+	  device.
+
+config SOUNDWIRE_CADENCE
+	tristate
+	select CRC8
+
+config SOUNDWIRE_INTEL
+	tristate "Intel SoundWire Master driver"
+	select SOUNDWIRE_CADENCE
+	select SOUNDWIRE_GENERIC_ALLOCATION
+	select AUXILIARY_BUS
+	depends on ACPI && SND_SOC
+	depends on SND_SOC_SOF_HDA_MLINK || !SND_SOC_SOF_HDA_MLINK
+	depends on SND_HDA_CORE || !SND_HDA_ALIGNED_MMIO
+	help
+	  SoundWire Intel Master driver.
+	  If you have an Intel platform which has a SoundWire Master then
+	  enable this config option to get the SoundWire support for that
+	  device.
+
+config SOUNDWIRE_QCOM
+	tristate "Qualcomm SoundWire Master driver"
+	imply SLIMBUS
+	depends on SND_SOC
+	help
+	  SoundWire Qualcomm Master driver.
+	  If you have an Qualcomm platform which has a SoundWire Master then
+	  enable this config option to get the SoundWire support for that
+	  device
+
+config SOUNDWIRE_GENERIC_ALLOCATION
+	tristate
+
+endif