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, 26 insertions, 0 deletions

diff --git a/drivers/misc/keba/Kconfig b/drivers/misc/keba/Kconfig
new file mode 100644
index 000000000..d6d47197a
--- /dev/null
+++ b/drivers/misc/keba/Kconfig
@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: GPL-2.0
+config KEBA_CP500
+	tristate "KEBA CP500 system FPGA support"
+	depends on X86_64 || ARM64 || COMPILE_TEST
+	depends on PCI
+	depends on I2C
+	select AUXILIARY_BUS
+	help
+	  This driver supports the KEBA CP500 system FPGA, which is used in
+	  KEBA CP500 devices. It registers all sub devices present on the CP500
+	  system FPGA as separate devices. A driver is needed for each sub
+	  device.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called cp500.
+
+config KEBA_LAN9252
+	tristate "KEBA CP500 LAN9252 configuration"
+	depends on SPI
+	depends on KEBA_CP500 || COMPILE_TEST
+	help
+	  This driver is used for updating the configuration of the LAN9252
+	  controller on KEBA CP500 devices.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called lan9252.