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, 148 insertions, 0 deletions

diff --git a/net/bluetooth/Kconfig b/net/bluetooth/Kconfig
new file mode 100644
index 000000000..d250e94e9
--- /dev/null
+++ b/net/bluetooth/Kconfig
@@ -0,0 +1,148 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Bluetooth subsystem configuration
+#
+
+menuconfig BT
+	tristate "Bluetooth subsystem support"
+	depends on !S390
+	depends on RFKILL || !RFKILL
+	select CRC16
+	select CRYPTO
+	select CRYPTO_LIB_AES
+	select CRYPTO_LIB_AES_CBC_MACS
+	select CRYPTO_ECDH
+	help
+	  Bluetooth is low-cost, low-power, short-range wireless technology.
+	  It was designed as a replacement for cables and other short-range
+	  technologies like IrDA.  Bluetooth operates in personal area range
+	  that typically extends up to 10 meters.  More information about
+	  Bluetooth can be found at <https://www.bluetooth.com/>.
+
+	  Linux Bluetooth subsystem consist of several layers:
+	     Bluetooth Core
+		HCI device and connection manager, scheduler
+		SCO audio links
+		L2CAP (Logical Link Control and Adaptation Protocol)
+		SMP (Security Manager Protocol) on LE (Low Energy) links
+		ISO isochronous links
+	     HCI Device drivers (Interface to the hardware)
+	     RFCOMM Module (RFCOMM Protocol)  
+	     BNEP Module (Bluetooth Network Encapsulation Protocol)
+	     HIDP Module (Human Interface Device Protocol)
+
+	  Say Y here to compile Bluetooth support into the kernel or say M to
+	  compile it as module (bluetooth).
+
+	  To use Linux Bluetooth subsystem, you will need several user-space
+	  utilities like hciconfig and bluetoothd.  These utilities and updates
+	  to Bluetooth kernel modules are provided in the BlueZ packages.  For
+	  more information, see <http://www.bluez.org/>.
+
+config BT_BREDR
+	bool "Bluetooth Classic (BR/EDR) features"
+	depends on BT
+	default y
+	help
+	  Bluetooth Classic includes support for Basic Rate (BR)
+	  available with Bluetooth version 1.0b or later and support
+	  for Enhanced Data Rate (EDR) available with Bluetooth
+	  version 2.0 or later.
+
+source "net/bluetooth/rfcomm/Kconfig"
+
+source "net/bluetooth/bnep/Kconfig"
+
+source "net/bluetooth/hidp/Kconfig"
+
+config BT_LE
+	bool "Bluetooth Low Energy (LE) features"
+	depends on BT
+	default y
+	help
+	  Bluetooth Low Energy includes support low-energy physical
+	  layer available with Bluetooth version 4.0 or later.
+
+config BT_LE_L2CAP_ECRED
+	bool "Bluetooth L2CAP Enhanced Credit Flow Control"
+	depends on BT_LE
+	default y
+	help
+	  Bluetooth Low Energy L2CAP Enhanced Credit Flow Control available with
+	  Bluetooth version 5.2 or later.
+
+	  This can be overridden by passing bluetooth.enable_ecred=[1|0]
+	  on the kernel commandline.
+
+config BT_6LOWPAN
+	tristate "Bluetooth 6LoWPAN support"
+	depends on BT_LE && 6LOWPAN
+	help
+	  IPv6 compression over Bluetooth Low Energy.
+
+config BT_LEDS
+	bool "Enable LED triggers"
+	depends on BT
+	depends on LEDS_CLASS
+	select LEDS_TRIGGERS
+	help
+	  This option selects a few LED triggers for different
+	  Bluetooth events.
+
+config BT_MSFTEXT
+	bool "Enable Microsoft extensions"
+	depends on BT
+	help
+	  This options enables support for the Microsoft defined HCI
+	  vendor extensions.
+
+config BT_AOSPEXT
+	bool "Enable Android Open Source Project extensions"
+	depends on BT
+	help
+	  This options enables support for the Android Open Source
+	  Project defined HCI vendor extensions.
+
+config BT_DEBUGFS
+	bool "Export Bluetooth internals in debugfs"
+	depends on BT && DEBUG_FS
+	default y
+	help
+	  Provide extensive information about internal Bluetooth states
+	  in debugfs.
+
+config BT_SELFTEST
+	bool "Bluetooth self testing support"
+	depends on BT && DEBUG_KERNEL
+	help
+	  Run self tests when initializing the Bluetooth subsystem.  This
+	  is a developer option and can cause significant delay when booting
+	  the system.
+
+	  When the Bluetooth subsystem is built as module, then the test
+	  cases are run first thing at module load time.  When the Bluetooth
+	  subsystem is compiled into the kernel image, then the test cases
+	  are run late in the initcall hierarchy.
+
+config BT_SELFTEST_ECDH
+	bool "ECDH test cases"
+	depends on BT_LE && BT_SELFTEST
+	help
+	  Run test cases for ECDH cryptographic functionality used by the
+	  Bluetooth Low Energy Secure Connections feature.
+
+config BT_SELFTEST_SMP
+	bool "SMP test cases"
+	depends on BT_LE && BT_SELFTEST
+	help
+	  Run test cases for SMP cryptographic functionality, including both
+	  legacy SMP as well as the Secure Connections features.
+
+config BT_FEATURE_DEBUG
+	bool "Enable runtime option for debugging statements"
+	depends on BT && !DYNAMIC_DEBUG
+	help
+	  This provides an option to enable/disable debugging statements
+	  at runtime via the experimental features interface.
+
+source "drivers/bluetooth/Kconfig"