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, 57 insertions, 0 deletions

diff --git a/include/acpi/apei.h b/include/acpi/apei.h
new file mode 100644
index 000000000..dc60f7db5
--- /dev/null
+++ b/include/acpi/apei.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * apei.h - ACPI Platform Error Interface
+ */
+
+#ifndef ACPI_APEI_H
+#define ACPI_APEI_H
+
+#include <linux/acpi.h>
+#include <linux/cper.h>
+#include <asm/ioctls.h>
+
+#define APEI_ERST_INVALID_RECORD_ID	0xffffffffffffffffULL
+
+#define APEI_ERST_CLEAR_RECORD		_IOW('E', 1, u64)
+#define APEI_ERST_GET_RECORD_COUNT	_IOR('E', 2, u32)
+
+#ifdef __KERNEL__
+
+enum hest_status {
+	HEST_ENABLED,
+	HEST_DISABLED,
+	HEST_NOT_FOUND,
+};
+
+extern int hest_disable;
+extern int erst_disable;
+#ifdef CONFIG_ACPI_APEI_GHES
+extern bool ghes_disable;
+void __init acpi_ghes_init(void);
+#else
+#define ghes_disable 1
+static inline void acpi_ghes_init(void) { }
+#endif
+
+#ifdef CONFIG_ACPI_APEI
+void __init acpi_hest_init(void);
+#else
+static inline void acpi_hest_init(void) { }
+#endif
+
+int erst_write(const struct cper_record_header *record);
+ssize_t erst_get_record_count(void);
+int erst_get_record_id_begin(int *pos);
+int erst_get_record_id_next(int *pos, u64 *record_id);
+void erst_get_record_id_end(void);
+ssize_t erst_read(u64 record_id, struct cper_record_header *record,
+		  size_t buflen);
+ssize_t erst_read_record(u64 record_id, struct cper_record_header *record,
+		size_t buflen, size_t recordlen, const guid_t *creatorid);
+int erst_clear(u64 record_id);
+
+int arch_apei_enable_cmcff(struct acpi_hest_header *hest_hdr, void *data);
+void arch_apei_report_mem_error(int sev, struct cper_sec_mem_err *mem_err);
+
+#endif
+#endif