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, 30 insertions, 0 deletions

diff --git a/tools/perf/util/values.h b/tools/perf/util/values.h
new file mode 100644
index 000000000..bbca33dac
--- /dev/null
+++ b/tools/perf/util/values.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_VALUES_H
+#define __PERF_VALUES_H
+
+#include <stdio.h>
+#include <linux/types.h>
+
+struct evsel;
+
+struct perf_read_values {
+	int threads;
+	int threads_max;
+	u32 *pid, *tid;
+	int num_counters;
+	int counters_max;
+	struct evsel **counters;
+	u64 **value;
+};
+
+int perf_read_values_init(struct perf_read_values *values);
+void perf_read_values_destroy(struct perf_read_values *values);
+
+int perf_read_values_add_value(struct perf_read_values *values,
+				u32 pid, u32 tid,
+				struct evsel *evsel, u64 value);
+
+void perf_read_values_display(FILE *fp, struct perf_read_values *values,
+			      int raw);
+
+#endif /* __PERF_VALUES_H */