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, 75 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-ppi b/Documentation/ABI/testing/sysfs-driver-ppi
new file mode 100644
index 000000000..1a56fc507
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-ppi
@@ -0,0 +1,75 @@
+What:		/sys/class/tpm/tpmX/ppi/
+Date:		August 2012
+KernelVersion:	3.6
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This folder includes the attributes related with PPI (Physical
+		Presence Interface). Only if TPM is supported by BIOS, this
+		folder makes sense. The folder path can be got by command
+		'find /sys/ -name 'pcrs''. For the detail information of PPI,
+		please refer to the PPI specification from
+
+		http://www.trustedcomputinggroup.org/
+
+		In Linux 4.2 ppi was moved to the character device directory.
+		A symlink from tpmX/device/ppi to tpmX/ppi to provide backwards
+		compatibility.
+
+What:		/sys/class/tpm/tpmX/ppi/version
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the version of the PPI supported by the
+		platform.
+		This file is readonly.
+
+What:		/sys/class/tpm/tpmX/ppi/request
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the request for an operation to be
+		executed in the pre-OS environment. It is the only input from
+		the OS to the pre-OS environment. The request should be an
+		integer value range from 1 to 160, and 0 means no request.
+		This file can be read and written.
+
+What:		/sys/class/tpm/tpmX/ppi/response
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the response to the most recent operation
+		request it acted upon. The format is "<request> <response num>
+		: <response description>".
+		This file is readonly.
+
+What:		/sys/class/tpm/tpmX/ppi/transition_action
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the platform-specific action that should
+		take place in order to transition to the BIOS for execution of
+		a requested operation. The format is "<action num>: <action
+		description>".
+		This file is readonly.
+
+What:		/sys/class/tpm/tpmX/ppi/tcg_operations
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows whether it is allowed to request an
+		operation to be executed in the pre-OS environment by the BIOS
+		for the requests defined by TCG, i.e. requests from 1 to 22.
+		The format is "<request> <status num>: <status description>".
+		This attribute is only supported by PPI version 1.2+.
+		This file is readonly.
+
+What:		/sys/class/tpm/tpmX/ppi/vs_operations
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows whether it is allowed to request an
+		operation to be executed in the pre-OS environment by the BIOS
+		for the verdor specific requests, i.e. requests from 128 to
+		255. The format is same with tcg_operations. This attribute
+		is also only supported by PPI version 1.2+.
+		This file is readonly.