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, 200 insertions, 0 deletions

diff --git a/drivers/Makefile b/drivers/Makefile
new file mode 100644
index 000000000..0841ea851
--- /dev/null
+++ b/drivers/Makefile
@@ -0,0 +1,200 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux kernel device drivers.
+#
+# 15 Sep 2000, Christoph Hellwig <hch@infradead.org>
+# Rewritten to use lists instead of if-statements.
+#
+
+obj-y				+= cache/
+obj-y				+= irqchip/
+obj-y				+= bus/
+
+obj-y				+= phy/
+
+# GPIO must come after pinctrl as gpios may need to mux pins etc
+obj-$(CONFIG_PINCTRL)		+= pinctrl/
+obj-$(CONFIG_GPIOLIB)		+= gpio/
+obj-y				+= pwm/
+
+# LEDs must come before PCI, it is needed by NPEM driver
+obj-y				+= leds/
+
+obj-y				+= pci/
+
+obj-$(CONFIG_PARISC)		+= parisc/
+obj-$(CONFIG_RAPIDIO)		+= rapidio/
+obj-y				+= video/
+obj-y				+= idle/
+
+# IPMI must come before ACPI in order to provide IPMI opregion support
+obj-y				+= char/ipmi/
+
+obj-$(CONFIG_ACPI)		+= acpi/
+
+# PnP must come after ACPI since it will eventually need to check if acpi
+# was used and do nothing if so
+obj-$(CONFIG_PNP)		+= pnp/
+obj-y				+= amba/
+
+obj-y				+= clk/
+# Many drivers will want to use DMA so this has to be made available
+# really early.
+obj-$(CONFIG_DMADEVICES)	+= dma/
+
+# SOC specific infrastructure drivers.
+obj-y				+= soc/
+obj-$(CONFIG_PM_GENERIC_DOMAINS)	+= pmdomain/
+
+obj-y				+= virtio/
+obj-$(CONFIG_VDPA)		+= vdpa/
+obj-$(CONFIG_XEN)		+= xen/
+
+# regulators early, since some subsystems rely on them to initialize
+obj-$(CONFIG_REGULATOR)		+= regulator/
+
+# reset controllers early, since gpu drivers might rely on them to initialize
+obj-$(CONFIG_RESET_CONTROLLER)	+= reset/
+
+# tty/ comes before char/ so that the VT console is the boot-time
+# default.
+obj-y				+= tty/
+obj-y				+= char/
+
+# iommu/ comes before gpu as gpu are using iommu controllers
+obj-y				+= iommu/
+
+# gpu/ comes after char for AGP vs DRM startup and after iommu
+obj-y				+= gpu/
+
+obj-$(CONFIG_CONNECTOR)		+= connector/
+
+# i810fb depends on char/agp/
+obj-$(CONFIG_FB_I810)           += video/fbdev/i810/
+
+obj-$(CONFIG_PARPORT)		+= parport/
+obj-y				+= base/ block/ misc/ mfd/ nfc/
+obj-$(CONFIG_LIBNVDIMM)		+= nvdimm/
+obj-y				+= dax/
+obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/
+obj-$(CONFIG_NUBUS)		+= nubus/
+obj-y				+= cxl/
+obj-y				+= macintosh/
+obj-y				+= scsi/
+obj-y				+= nvme/
+obj-$(CONFIG_ATA)		+= ata/
+obj-$(CONFIG_TARGET_CORE)	+= target/
+obj-$(CONFIG_MTD)		+= mtd/
+obj-$(CONFIG_SPI)		+= spi/
+obj-$(CONFIG_SPMI)		+= spmi/
+obj-$(CONFIG_HSI)		+= hsi/
+obj-$(CONFIG_SLIMBUS)		+= slimbus/
+obj-y				+= net/
+obj-$(CONFIG_ATM)		+= atm/
+obj-$(CONFIG_FUSION)		+= message/
+obj-y				+= firewire/
+obj-$(CONFIG_UIO)		+= uio/
+obj-$(CONFIG_VFIO)		+= vfio/
+obj-y				+= cdrom/
+obj-y				+= auxdisplay/
+obj-$(CONFIG_PCCARD)		+= pcmcia/
+obj-$(CONFIG_DIO)		+= dio/
+obj-$(CONFIG_SBUS)		+= sbus/
+obj-$(CONFIG_ZORRO)		+= zorro/
+obj-$(CONFIG_ATA_OVER_ETH)	+= block/aoe/
+obj-$(CONFIG_TC)		+= tc/
+obj-$(CONFIG_USB_PHY)		+= usb/
+obj-$(CONFIG_USB)		+= usb/
+obj-$(CONFIG_USB_SUPPORT)	+= usb/
+obj-$(CONFIG_PCI)		+= usb/
+obj-$(CONFIG_USB_GADGET)	+= usb/
+obj-$(CONFIG_OF)		+= usb/
+obj-$(CONFIG_SERIO)		+= input/serio/
+obj-$(CONFIG_GAMEPORT)		+= input/gameport/
+obj-$(CONFIG_INPUT)		+= input/
+obj-$(CONFIG_RTC_LIB)		+= rtc/
+obj-y				+= i2c/ i3c/ media/
+obj-$(CONFIG_PPS)		+= pps/
+obj-y				+= ptp/
+obj-$(CONFIG_W1)		+= w1/
+obj-y				+= power/
+obj-$(CONFIG_HWMON)		+= hwmon/
+obj-$(CONFIG_THERMAL)		+= thermal/
+obj-$(CONFIG_WATCHDOG)		+= watchdog/
+obj-$(CONFIG_MD)		+= md/
+obj-$(CONFIG_BT)		+= bluetooth/
+obj-$(CONFIG_ACCESSIBILITY)	+= accessibility/
+obj-$(CONFIG_EDAC)		+= edac/
+obj-$(CONFIG_EISA)		+= eisa/
+obj-$(CONFIG_PM_OPP)		+= opp/
+obj-$(CONFIG_CPU_FREQ)		+= cpufreq/
+obj-$(CONFIG_CPU_IDLE)		+= cpuidle/
+obj-y				+= mmc/
+obj-y				+= ufs/
+obj-$(CONFIG_MEMSTICK)		+= memstick/
+obj-$(CONFIG_INFINIBAND)	+= infiniband/
+obj-y				+= firmware/
+obj-$(CONFIG_FWCTL)		+= fwctl/
+obj-$(CONFIG_CRYPTO)		+= crypto/
+obj-$(CONFIG_SUPERH)		+= sh/
+obj-y				+= clocksource/
+obj-$(CONFIG_DCA)		+= dca/
+obj-$(CONFIG_HID_SUPPORT)	+= hid/
+obj-$(CONFIG_PPC_PS3)		+= ps3/
+obj-$(CONFIG_OF)		+= of/
+obj-$(CONFIG_SSB)		+= ssb/
+obj-$(CONFIG_BCMA)		+= bcma/
+obj-$(CONFIG_VHOST_RING)	+= vhost/
+obj-$(CONFIG_VHOST_IOTLB)	+= vhost/
+obj-$(CONFIG_VHOST)		+= vhost/
+obj-$(CONFIG_GREYBUS)		+= greybus/
+obj-$(CONFIG_COMEDI)		+= comedi/
+obj-$(CONFIG_GPIB)		+= gpib/
+obj-$(CONFIG_STAGING)		+= staging/
+obj-y				+= platform/
+
+obj-$(CONFIG_MAILBOX)		+= mailbox/
+obj-$(CONFIG_HWSPINLOCK)	+= hwspinlock/
+obj-$(CONFIG_REMOTEPROC)	+= remoteproc/
+obj-$(CONFIG_RPMSG)		+= rpmsg/
+obj-$(CONFIG_SOUNDWIRE)		+= soundwire/
+
+# Virtualization drivers
+obj-y				+= virt/
+obj-$(CONFIG_HYPERV)		+= hv/
+
+obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/
+obj-$(CONFIG_EXTCON)		+= extcon/
+obj-$(CONFIG_MEMORY)		+= memory/
+obj-$(CONFIG_IIO)		+= iio/
+obj-$(CONFIG_IPACK_BUS)		+= ipack/
+obj-$(CONFIG_NTB)		+= ntb/
+obj-$(CONFIG_POWERCAP)		+= powercap/
+obj-$(CONFIG_MCB)		+= mcb/
+obj-$(CONFIG_PERF_EVENTS)	+= perf/
+obj-$(CONFIG_RAS)		+= ras/
+obj-$(CONFIG_USB4)		+= thunderbolt/
+obj-$(CONFIG_CORESIGHT)		+= hwtracing/coresight/
+obj-y				+= hwtracing/intel_th/
+obj-$(CONFIG_STM)		+= hwtracing/stm/
+obj-$(CONFIG_HISI_PTT)		+= hwtracing/ptt/
+obj-y				+= android/
+obj-$(CONFIG_NVMEM)		+= nvmem/
+obj-$(CONFIG_FPGA)		+= fpga/
+obj-$(CONFIG_FSI)		+= fsi/
+obj-$(CONFIG_TEE)		+= tee/
+obj-$(CONFIG_MULTIPLEXER)	+= mux/
+obj-$(CONFIG_SIOX)		+= siox/
+obj-$(CONFIG_GNSS)		+= gnss/
+obj-$(CONFIG_INTERCONNECT)	+= interconnect/
+obj-$(CONFIG_COUNTER)		+= counter/
+obj-$(CONFIG_MOST)		+= most/
+obj-$(CONFIG_PECI)		+= peci/
+obj-$(CONFIG_HTE)		+= hte/
+obj-$(CONFIG_DRM_ACCEL)		+= accel/
+obj-$(CONFIG_CDX_BUS)		+= cdx/
+obj-$(CONFIG_DPLL)		+= dpll/
+obj-y				+= resctrl/
+
+obj-$(CONFIG_DIBS)		+= dibs/
+obj-$(CONFIG_S390)		+= s390/