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, 35 insertions, 0 deletions

diff --git a/include/soc/imx/revision.h b/include/soc/imx/revision.h
new file mode 100644
index 000000000..b122d2fc8
--- /dev/null
+++ b/include/soc/imx/revision.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2015 Linaro Ltd.
+ */
+
+#ifndef __SOC_IMX_REVISION_H__
+#define __SOC_IMX_REVISION_H__
+
+#define IMX_CHIP_REVISION_1_0		0x10
+#define IMX_CHIP_REVISION_1_1		0x11
+#define IMX_CHIP_REVISION_1_2		0x12
+#define IMX_CHIP_REVISION_1_3		0x13
+#define IMX_CHIP_REVISION_1_4		0x14
+#define IMX_CHIP_REVISION_1_5		0x15
+#define IMX_CHIP_REVISION_2_0		0x20
+#define IMX_CHIP_REVISION_2_1		0x21
+#define IMX_CHIP_REVISION_2_2		0x22
+#define IMX_CHIP_REVISION_2_3		0x23
+#define IMX_CHIP_REVISION_3_0		0x30
+#define IMX_CHIP_REVISION_3_1		0x31
+#define IMX_CHIP_REVISION_3_2		0x32
+#define IMX_CHIP_REVISION_3_3		0x33
+#define IMX_CHIP_REVISION_UNKNOWN	0xff
+
+int mx25_revision(void);
+int mx27_revision(void);
+int mx31_revision(void);
+int mx35_revision(void);
+int mx51_revision(void);
+int mx53_revision(void);
+
+unsigned int imx_get_soc_revision(void);
+void imx_print_silicon_rev(const char *cpu, int srev);
+
+#endif /* __SOC_IMX_REVISION_H__ */