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, 112 insertions, 0 deletions

diff --git a/sound/Kconfig b/sound/Kconfig
new file mode 100644
index 000000000..8b4020539
--- /dev/null
+++ b/sound/Kconfig
@@ -0,0 +1,112 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig SOUND
+	tristate "Sound card support"
+	depends on HAS_IOMEM || INDIRECT_IOMEM
+	help
+	  If you have a sound card in your computer, i.e. if it can say more
+	  than an occasional beep, say Y.
+
+if SOUND
+
+config SOUND_OSS_CORE
+	bool
+	default n
+
+config SOUND_OSS_CORE_PRECLAIM
+	bool "Preclaim OSS device numbers"
+	depends on SOUND_OSS_CORE
+	default y
+	help
+	  With this option enabled, the kernel will claim all OSS device
+	  numbers if any OSS support (native or emulation) is enabled
+	  whether the respective module is loaded or not and try to load the
+	  appropriate module using sound-slot/service-* and char-major-*
+	  module aliases when one of the device numbers is opened.  With
+	  this option disabled, kernel will only claim actually in-use
+	  device numbers and opening a missing device will generate only the
+	  standard char-major-* aliases.
+
+	  The only visible difference is use of additional module aliases
+	  and whether OSS sound devices appear multiple times in
+	  /proc/devices.  sound-slot/service-* module aliases are scheduled
+	  to be removed (ie. PRECLAIM won't be available) and this option is
+	  to make the transition easier.  This option can be overridden
+	  during boot using the kernel parameter soundcore.preclaim_oss.
+
+	  Disabling this allows alternative OSS implementations.
+
+	  If unsure, say Y.
+
+source "sound/oss/dmasound/Kconfig"
+
+menuconfig SND
+	tristate "Advanced Linux Sound Architecture"
+	help
+	  Say 'Y' or 'M' to enable ALSA (Advanced Linux Sound Architecture),
+	  the new base sound system.
+
+	  For more information, see <http://www.alsa-project.org/>
+
+if SND
+
+source "sound/core/Kconfig"
+
+source "sound/drivers/Kconfig"
+
+source "sound/isa/Kconfig"
+
+source "sound/pci/Kconfig"
+
+source "sound/hda/Kconfig"
+
+source "sound/ppc/Kconfig"
+
+source "sound/ac97/Kconfig"
+
+source "sound/aoa/Kconfig"
+
+source "sound/arm/Kconfig"
+
+source "sound/atmel/Kconfig"
+
+source "sound/spi/Kconfig"
+
+source "sound/mips/Kconfig"
+
+source "sound/sh/Kconfig"
+
+# the following will depend on the order of config.
+# here assuming USB is defined before ALSA
+source "sound/usb/Kconfig"
+
+source "sound/firewire/Kconfig"
+
+# the following will depend on the order of config.
+# here assuming PCMCIA is defined before ALSA
+source "sound/pcmcia/Kconfig"
+
+source "sound/sparc/Kconfig"
+
+source "sound/parisc/Kconfig"
+
+source "sound/soc/Kconfig"
+
+source "sound/x86/Kconfig"
+
+source "sound/synth/Kconfig"
+
+source "sound/xen/Kconfig"
+
+source "sound/virtio/Kconfig"
+
+endif # SND
+
+endif # SOUND
+
+config AC97_BUS
+	tristate
+	help
+	  This is used to avoid config and link hard dependencies between the
+	  sound subsystem and other function drivers completely unrelated to
+	  sound although they're sharing the AC97 bus. Concerned drivers
+	  should "select" this.