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, 124 insertions, 0 deletions

diff --git a/drivers/message/fusion/Kconfig b/drivers/message/fusion/Kconfig
new file mode 100644
index 000000000..88a6e506a
--- /dev/null
+++ b/drivers/message/fusion/Kconfig
@@ -0,0 +1,124 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menuconfig FUSION
+	bool "Fusion MPT device support"
+	depends on PCI && HAS_IOPORT
+	help
+	Say Y here to get to see options for Fusion Message
+	Passing Technology (MPT) drivers.
+	This option alone does not add any kernel code.
+
+	If you say N, all options in this submenu will be skipped and disabled.
+
+if FUSION
+
+config FUSION_SPI
+	tristate "Fusion MPT ScsiHost drivers for SPI"
+	depends on PCI && SCSI
+	select SCSI_SPI_ATTRS
+	help
+	  SCSI HOST support for a parallel SCSI host adapters.
+
+	  List of supported controllers:
+
+	  LSI53C1020
+	  LSI53C1020A
+	  LSI53C1030
+	  LSI53C1035
+	  ATTO UL4D
+
+config FUSION_FC
+	tristate "Fusion MPT ScsiHost drivers for FC"
+	depends on PCI && SCSI
+	depends on SCSI_FC_ATTRS
+	help
+	  SCSI HOST support for a Fiber Channel host adapters.
+
+	  List of supported controllers:
+
+	  LSIFC909
+	  LSIFC919
+	  LSIFC919X
+	  LSIFC929
+	  LSIFC929X
+	  LSIFC929XL
+	  LSIFC949X
+	  LSIFC949E
+	  Brocade FC 410/420
+
+config FUSION_SAS
+	tristate "Fusion MPT ScsiHost drivers for SAS"
+	depends on PCI && SCSI
+	select SCSI_SAS_ATTRS
+	help
+	  SCSI HOST support for a SAS host adapters.
+
+	  List of supported controllers:
+
+	  LSISAS1064
+	  LSISAS1068
+	  LSISAS1064E
+	  LSISAS1068E
+	  LSISAS1078
+
+config FUSION_MAX_SGE
+	int "Maximum number of scatter gather entries (16 - 128)"
+	default "128"
+	range 16 128
+	help
+	  This option allows you to specify the maximum number of scatter-
+	  gather entries per I/O. The driver default is 128, which matches
+	  SCSI_MAX_PHYS_SEGMENTS. However, it may decreased down to 16.
+	  Decreasing this parameter will reduce memory requirements
+	  on a per controller instance.
+
+config FUSION_CTL
+	tristate "Fusion MPT misc device (ioctl) driver"
+	depends on FUSION_SPI || FUSION_FC || FUSION_SAS
+	help
+	  The Fusion MPT misc device driver provides specialized control
+	  of MPT adapters via system ioctl calls.  Use of ioctl calls to
+	  the MPT driver requires that you create and use a misc device
+	  node ala:
+	  mknod /dev/mptctl c 10 240
+
+	  One use of this ioctl interface is to perform an upgrade (reflash)
+	  of the MPT adapter firmware.  Refer to readme file(s) distributed
+	  with the Fusion MPT linux driver for additional details.
+
+	  If enabled by saying M to this, a driver named: mptctl
+	  will be compiled.
+
+	  If unsure whether you really want or need this, say N.
+
+config FUSION_LAN
+	tristate "Fusion MPT LAN driver"
+	depends on FUSION_FC && NET_FC
+	help
+	  This module supports LAN IP traffic over Fibre Channel port(s)
+	  on Fusion MPT compatible hardware (LSIFC9xx chips).
+	  The physical interface used is defined in RFC 2625.
+	  Please refer to that document for details.
+
+	  Installing this driver requires the knowledge to configure and
+	  activate a new network interface, "fc0", using standard Linux tools.
+
+	  If enabled by saying M to this, a driver named: mptlan
+	  will be compiled.
+
+	  If unsure whether you really want or need this, say N.
+
+config FUSION_LOGGING
+	bool "Fusion MPT logging facility"
+	help
+	  This turns on a logging facility that can be used to debug a number
+	  of Fusion MPT related problems.
+
+	  The debug level can be programmed on the fly via SysFS (hex values)
+
+	  echo [level] > /sys/class/scsi_host/host#/debug_level
+
+	  There are various debug levels that can be found in the source:
+	  file:drivers/message/fusion/mptdebug.h
+
+endif # FUSION