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, 207 insertions, 0 deletions

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
new file mode 100644
index 000000000..669f76000
--- /dev/null
+++ b/drivers/char/ipmi/Kconfig
@@ -0,0 +1,207 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# IPMI device configuration
+#
+
+menuconfig IPMI_HANDLER
+	tristate 'IPMI top-level message handler'
+	depends on HAS_IOMEM
+	select IPMI_DMI_DECODE if DMI
+	help
+	  This enables the central IPMI message handler, required for IPMI
+	  to work.
+
+	  IPMI is a standard for managing sensors (temperature,
+	  voltage, etc.) in a system.
+
+	  See <file:Documentation/driver-api/ipmi.rst> for more details on the driver.
+
+	  If unsure, say N.
+
+config IPMI_DMI_DECODE
+	select IPMI_PLAT_DATA
+	bool
+
+config IPMI_PLAT_DATA
+	bool
+
+if IPMI_HANDLER
+
+config IPMI_PANIC_EVENT
+	bool 'Generate a panic event to all BMCs on a panic'
+	help
+	  When a panic occurs, this will cause the IPMI message handler to,
+	  by default, generate an IPMI event describing the panic to each
+	  interface registered with the message handler.  This is always
+	  available, the module parameter for ipmi_msghandler named
+	  panic_op can be set to "event" to chose this value, this config
+	  simply causes the default value to be set to "event".
+
+config IPMI_PANIC_STRING
+	bool 'Generate OEM events containing the panic string'
+	depends on IPMI_PANIC_EVENT
+	help
+	  When a panic occurs, this will cause the IPMI message handler to,
+	  by default, generate IPMI OEM type f0 events holding the IPMB
+	  address of the panic generator (byte 4 of the event), a sequence
+	  number for the string (byte 5 of the event) and part of the
+	  string (the rest of the event).  Bytes 1, 2, and 3 are the normal
+	  usage for an OEM event.  You can fetch these events and use the
+	  sequence numbers to piece the string together.  This config
+	  parameter sets the default value to generate these events,
+	  the module parameter for ipmi_msghandler named panic_op can
+	  be set to "string" to chose this value, this config simply
+	  causes the default value to be set to "string".
+
+config IPMI_DEVICE_INTERFACE
+	tristate 'Device interface for IPMI'
+	help
+	  This provides an IOCTL interface to the IPMI message handler so
+	  userland processes may use IPMI.  It supports poll() and select().
+
+config IPMI_SI
+	tristate 'IPMI System Interface handler'
+	select IPMI_PLAT_DATA
+	help
+	  Provides a driver for System Interfaces (KCS, SMIC, BT).
+	  Currently, only KCS and SMIC are supported.  If
+	  you are using IPMI, you should probably say "y" here.
+
+config IPMI_SSIF
+	tristate 'IPMI SMBus handler (SSIF)'
+	depends on I2C
+	help
+	  Provides a driver for a SMBus interface to a BMC, meaning that you
+	  have a driver that must be accessed over an I2C bus instead of a
+	  standard interface.  This module requires I2C support.
+
+config IPMI_IPMB
+	tristate 'IPMI IPMB interface'
+	depends on I2C && I2C_SLAVE
+	help
+	  Provides a driver for a system running right on the IPMB bus.
+	  It supports normal system interface messages to a BMC on the IPMB
+	  bus, and it also supports direct messaging on the bus using
+	  IPMB direct messages.  This module requires I2C support.
+
+config IPMI_LS2K
+	bool 'Loongson-2K IPMI interface'
+	depends on LOONGARCH
+	select MFD_LS2K_BMC_CORE
+	help
+	  Provides a driver for Loongson-2K IPMI interfaces.
+
+config IPMI_POWERNV
+	depends on PPC_POWERNV
+	tristate 'POWERNV (OPAL firmware) IPMI interface'
+	help
+	  Provides a driver for OPAL firmware-based IPMI interfaces.
+
+config IPMI_WATCHDOG
+	tristate 'IPMI Watchdog Timer'
+	help
+	  This enables the IPMI watchdog timer.
+
+config IPMI_POWEROFF
+	tristate 'IPMI Poweroff'
+	help
+	  This enables a function to power off the system with IPMI if
+	  the IPMI management controller is capable of this.
+
+endif # IPMI_HANDLER
+
+config IPMI_KCS_BMC
+	tristate
+
+config ASPEED_KCS_IPMI_BMC
+	depends on ARCH_ASPEED || COMPILE_TEST
+	select IPMI_KCS_BMC
+	select REGMAP_MMIO
+	tristate "Aspeed KCS IPMI BMC driver"
+	help
+	  Provides a driver for the KCS (Keyboard Controller Style) IPMI
+	  interface found on Aspeed SOCs (AST2400 and AST2500).
+
+	  The driver implements the BMC side of the KCS contorller, it
+	  provides the access of KCS IO space for BMC side.
+
+config NPCM7XX_KCS_IPMI_BMC
+	depends on ARCH_NPCM || COMPILE_TEST
+	select IPMI_KCS_BMC
+	select REGMAP_MMIO
+	tristate "NPCM KCS IPMI BMC driver"
+	help
+	  Provides a driver for the KCS (Keyboard Controller Style) IPMI
+	  interface found on Nuvoton NPCM SOCs.
+
+	  The driver implements the BMC side of the KCS contorller, it
+	  provides the access of KCS IO space for BMC side.
+
+	  This support is also available as a module.  If so, the module
+	  will be called kcs_bmc_npcm7xx.
+
+config IPMI_KCS_BMC_CDEV_IPMI
+	depends on IPMI_KCS_BMC
+	tristate "IPMI character device interface for BMC KCS devices"
+	help
+	  Provides a BMC-side character device implementing IPMI
+	  semantics for KCS IPMI devices.
+
+	  Say YES if you wish to expose KCS devices on the BMC for IPMI
+	  purposes.
+
+	  This support is also available as a module. The module will be
+	  called kcs_bmc_cdev_ipmi.
+
+config IPMI_KCS_BMC_SERIO
+	depends on IPMI_KCS_BMC && SERIO
+	tristate "SerIO adaptor for BMC KCS devices"
+	help
+	  Adapts the BMC KCS device for the SerIO subsystem. This allows users
+	  to take advantage of userspace interfaces provided by SerIO where
+	  appropriate.
+
+	  Say YES if you wish to expose KCS devices on the BMC via SerIO
+	  interfaces.
+
+	  This support is also available as a module. The module will be
+	  called kcs_bmc_serio.
+
+config ASPEED_BT_IPMI_BMC
+	depends on ARCH_ASPEED || COMPILE_TEST
+	depends on MFD_SYSCON
+	select REGMAP_MMIO
+	tristate "BT IPMI bmc driver"
+	help
+	  Provides a driver for the BT (Block Transfer) IPMI interface
+	  found on Aspeed SOCs (AST2400 and AST2500). The driver
+	  implements the BMC side of the BT interface.
+
+config SSIF_IPMI_BMC
+	tristate "SSIF IPMI BMC driver"
+	depends on I2C && I2C_SLAVE
+	help
+	  This enables the IPMI SMBus system interface (SSIF) at the
+	  management (BMC) side.
+
+	  The driver implements the BMC side of the SMBus system
+	  interface (SSIF).
+
+config SSIF_IPMI_BMC_KUNIT_TEST
+	bool "KUnit tests for SSIF IPMI BMC driver" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	depends on SSIF_IPMI_BMC
+	default KUNIT_ALL_TESTS
+	help
+	  This option builds unit tests that exercise the SSIF BMC state
+	  machine, including request handling, response transmission,
+	  and error paths such as aborted or truncated transfers.
+
+config IPMB_DEVICE_INTERFACE
+	tristate 'IPMB Interface handler'
+	depends on I2C
+	depends on I2C_SLAVE
+	help
+	  Provides a driver for a device (Satellite MC) to
+	  receive requests and send responses back to the BMC via
+	  the IPMB interface. This module requires I2C support.