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, 64 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-alienware-wmi b/Documentation/ABI/testing/debugfs-alienware-wmi
new file mode 100644
index 000000000..c7f525d6b
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-alienware-wmi
@@ -0,0 +1,64 @@
+What:		/sys/kernel/debug/alienware-wmi-<wmi_device_name>/system_description
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	Kurt Borja <kuurtb@gmail.com>
+Description:
+		This file exposes the raw ``system_description`` number reported
+		by the WMAX device.
+
+		Only present on devices with the AWCC interface.
+
+		See Documentation/admin-guide/laptops/alienware-wmi.rst for
+		details.
+
+		RO
+
+What:		/sys/kernel/debug/alienware-wmi-<wmi_device_name>/hwmon_data
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	Kurt Borja <kuurtb@gmail.com>
+Description:
+		This file exposes HWMON private data.
+
+		Includes fan sensor count, temperature sensor count, internal
+		fan IDs and internal temp IDs.
+
+		See Documentation/admin-guide/laptops/alienware-wmi.rst for
+		details.
+
+		RO
+
+What:		/sys/kernel/debug/alienware-wmi-<wmi_device_name>/pprof_data
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	Kurt Borja <kuurtb@gmail.com>
+Description:
+		This file exposes Platform Profile private data.
+
+		Includes internal mapping to platform profiles and thermal
+		profile IDs.
+
+		See Documentation/admin-guide/laptops/alienware-wmi.rst for
+		details.
+
+		RO
+
+What:		/sys/kernel/debug/alienware-wmi-<wmi_device_name>/gpio_ctl/total_gpios
+Date:		May 2025
+KernelVersion:	6.16
+Contact:	Kurt Borja <kuurtb@gmail.com>
+Description:
+		Total number of GPIO pins reported by the device.
+
+		RO
+
+What:		/sys/kernel/debug/alienware-wmi-<wmi_device_name>/gpio_ctl/pinX
+Date:		May 2025
+KernelVersion:	6.16
+Contact:	Kurt Borja <kuurtb@gmail.com>
+Description:
+		This file controls GPIO pin X status.
+
+		See Documentation/wmi/devices/alienware-wmi.rst for details.
+
+		RW