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, 43 insertions, 0 deletions

diff --git a/include/sound/cs35l36.h b/include/sound/cs35l36.h
new file mode 100644
index 000000000..8f8049d39
--- /dev/null
+++ b/include/sound/cs35l36.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * linux/sound/cs35l36.h -- Platform data for CS35L36
+ *
+ * Copyright 2018 Cirrus Logic, Inc.
+ *
+ * Author: James Schulman <james.schulman@cirrus.com>
+ *
+ */
+
+#ifndef __CS35L36_H
+#define __CS35L36_H
+
+struct cs35l36_vpbr_cfg {
+	bool is_present;
+	bool vpbr_en;
+	int vpbr_thld;
+	int vpbr_atk_rate;
+	int vpbr_atk_vol;
+	int vpbr_max_attn;
+	int vpbr_wait;
+	int vpbr_rel_rate;
+	int vpbr_mute_en;
+};
+
+struct cs35l36_platform_data {
+	bool multi_amp_mode;
+	bool dcm_mode;
+	bool amp_pcm_inv;
+	bool imon_pol_inv;
+	bool vmon_pol_inv;
+	int boost_ind;
+	int bst_vctl;
+	int bst_vctl_sel;
+	int bst_ipk;
+	bool extern_boost;
+	int temp_warn_thld;
+	int irq_drv_sel;
+	int irq_gpio_sel;
+	struct cs35l36_vpbr_cfg vpbr_config;
+};
+
+#endif /* __CS35L36_H */