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, 29 insertions, 0 deletions

diff --git a/drivers/usb/image/Kconfig b/drivers/usb/image/Kconfig
new file mode 100644
index 000000000..a65c638e7
--- /dev/null
+++ b/drivers/usb/image/Kconfig
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# USB Imaging devices configuration
+#
+comment "USB Imaging devices"
+
+config USB_MDC800
+	tristate "USB Mustek MDC800 Digital Camera support"
+	help
+	  Say Y here if you want to connect this type of still camera to
+	  your computer's USB port. This driver can be used with gphoto 0.4.3
+	  and higher (look at <http://www.gphoto.org/>).
+	  To use it create a device node with "mknod /dev/mustek c 180 32" and
+	  configure it in your software.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mdc800.
+
+config USB_MICROTEK
+	tristate "Microtek X6USB scanner support"
+	depends on SCSI
+	help
+	  Say Y here if you want support for the Microtek X6USB and
+	  possibly the Phantom 336CX, Phantom C6 and ScanMaker V6U(S)L.
+	  Support for anything but the X6 is experimental.
+	  Please report failures and successes.
+	  The scanner will appear as a scsi generic device to the rest
+	  of the system. Scsi support is required.
+	  This driver can be compiled as a module, called microtek.