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, 33 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/berlin2q.h b/include/dt-bindings/clock/berlin2q.h
new file mode 100644
index 000000000..44b4ac382
--- /dev/null
+++ b/include/dt-bindings/clock/berlin2q.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Berlin2 BG2Q clock tree IDs
+ */
+
+#define CLKID_SYS		0
+#define CLKID_DRMFIGO		1
+#define CLKID_CFG		2
+#define CLKID_GFX2D		3
+#define CLKID_ZSP		4
+#define CLKID_PERIF		5
+#define CLKID_PCUBE		6
+#define CLKID_VSCOPE		7
+#define CLKID_NFC_ECC		8
+#define CLKID_VPP		9
+#define CLKID_APP		10
+#define CLKID_SDIO0XIN		11
+#define CLKID_SDIO1XIN		12
+#define CLKID_GFX2DAXI		13
+#define CLKID_GETH0		14
+#define CLKID_SATA		15
+#define CLKID_AHBAPB		16
+#define CLKID_USB0		17
+#define CLKID_USB1		18
+#define CLKID_USB2		19
+#define CLKID_USB3		20
+#define CLKID_PBRIDGE		21
+#define CLKID_SDIO		22
+#define CLKID_NFC		23
+#define CLKID_SMEMC		24
+#define CLKID_PCIE		25
+#define CLKID_TWD		26
+#define CLKID_CPU		27