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, 52 insertions, 0 deletions

diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
new file mode 100644
index 000000000..52eb7e4ba
--- /dev/null
+++ b/drivers/virt/Kconfig
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Virtualization support drivers
+#
+
+menuconfig VIRT_DRIVERS
+	bool "Virtualization drivers"
+	help
+	  Say Y here to get to see options for device drivers that support
+	  virtualization environments.
+
+	  If you say N, all options in this submenu will be skipped and disabled.
+
+if VIRT_DRIVERS
+
+config VMGENID
+	tristate "Virtual Machine Generation ID driver"
+	default y
+	help
+	  Say Y here to use the hypervisor-provided Virtual Machine Generation ID
+	  to reseed the RNG when the VM is cloned. This is highly recommended if
+	  you intend to do any rollback / cloning / snapshotting of VMs.
+
+	  Prefer Y to M so that this protection is activated very early.
+
+config FSL_HV_MANAGER
+	tristate "Freescale hypervisor management driver"
+	depends on FSL_SOC
+	select EPAPR_PARAVIRT
+	help
+          The Freescale hypervisor management driver provides several services
+	  to drivers and applications related to the Freescale hypervisor:
+
+          1) An ioctl interface for querying and managing partitions.
+
+          2) A file interface to reading incoming doorbells.
+
+          3) An interrupt handler for shutting down the partition upon
+	     receiving the shutdown doorbell from a manager partition.
+
+          4) A kernel interface for receiving callbacks when a managed
+	     partition shuts down.
+
+source "drivers/virt/vboxguest/Kconfig"
+
+source "drivers/virt/nitro_enclaves/Kconfig"
+
+source "drivers/virt/acrn/Kconfig"
+
+endif
+
+source "drivers/virt/coco/Kconfig"