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, 25 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-tee b/Documentation/ABI/testing/sysfs-class-tee
new file mode 100644
index 000000000..1a0a3050a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-tee
@@ -0,0 +1,25 @@
+What:		/sys/class/tee/tee{,priv}X/rpmb_routing_model
+Date:		May 2024
+KernelVersion:	6.10
+Contact:        op-tee@lists.trustedfirmware.org
+Description:
+		RPMB frames can be routed to the RPMB device via the
+		user-space daemon tee-supplicant or the RPMB subsystem
+		in the kernel. The value "user" means that the driver
+		will route the RPMB frames via user space. Conversely,
+		"kernel" means that the frames are routed via the RPMB
+		subsystem without assistance from tee-supplicant. It
+		should be assumed that RPMB frames are routed via user
+		space if the variable is absent. The primary purpose
+		of this variable is to let systemd know whether
+		tee-supplicant is needed in the early boot with initramfs.
+
+What:		/sys/class/tee/tee{,priv}X/revision
+Date:		Jan 2026
+KernelVersion:	6.19
+Contact:	op-tee@lists.trustedfirmware.org
+Description:
+		Read-only revision string reported by the TEE driver. This is
+		for diagnostics only and must not be used to infer feature
+		support. Use TEE_IOC_VERSION for capability and compatibility
+		checks.