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, 51 insertions, 0 deletions

diff --git a/drivers/leds/simatic/Kconfig b/drivers/leds/simatic/Kconfig
new file mode 100644
index 000000000..e616cc6d6
--- /dev/null
+++ b/drivers/leds/simatic/Kconfig
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config LEDS_SIEMENS_SIMATIC_IPC
+	tristate "LED driver for Siemens Simatic IPCs"
+	depends on LEDS_CLASS
+	depends on SIEMENS_SIMATIC_IPC
+	default y
+	help
+	  This option enables support for the LEDs of several Industrial PCs
+	  from Siemens.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called simatic-ipc-leds.
+
+config LEDS_SIEMENS_SIMATIC_IPC_APOLLOLAKE
+	tristate "LED driver for Siemens Simatic IPCs based on Intel Apollo Lake GPIO"
+	depends on LEDS_GPIO
+	depends on PINCTRL_BROXTON
+	depends on SIEMENS_SIMATIC_IPC
+	default LEDS_SIEMENS_SIMATIC_IPC
+	help
+	  This option enables support for the LEDs of several Industrial PCs
+	  from Siemens based on Apollo Lake GPIO i.e. IPC127E.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called simatic-ipc-leds-gpio-apollolake.
+
+config LEDS_SIEMENS_SIMATIC_IPC_F7188X
+	tristate "LED driver for Siemens Simatic IPCs based on Nuvoton GPIO"
+	depends on LEDS_GPIO
+	depends on GPIO_F7188X
+	depends on SIEMENS_SIMATIC_IPC
+	default LEDS_SIEMENS_SIMATIC_IPC
+	help
+	  This option enables support for the LEDs of several Industrial PCs
+	  from Siemens based on Nuvoton GPIO i.e. IPC227G.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called simatic-ipc-leds-gpio-f7188x.
+
+config LEDS_SIEMENS_SIMATIC_IPC_ELKHARTLAKE
+	tristate "LED driver for Siemens Simatic IPCs based on Intel Elkhart Lake GPIO"
+	depends on LEDS_GPIO
+	depends on PINCTRL_ELKHARTLAKE
+	depends on SIEMENS_SIMATIC_IPC
+	default LEDS_SIEMENS_SIMATIC_IPC
+	help
+	  This option enables support for the LEDs of several Industrial PCs
+	  from Siemens based on Elkhart Lake GPIO i.e. BX-21A.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called simatic-ipc-leds-gpio-elkhartlake.