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, 48 insertions, 0 deletions

diff --git a/tools/perf/util/intel-pt.h b/tools/perf/util/intel-pt.h
new file mode 100644
index 000000000..18fd0be52
--- /dev/null
+++ b/tools/perf/util/intel-pt.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * intel_pt.h: Intel Processor Trace support
+ * Copyright (c) 2013-2015, Intel Corporation.
+ */
+
+#ifndef INCLUDE__PERF_INTEL_PT_H__
+#define INCLUDE__PERF_INTEL_PT_H__
+
+#define INTEL_PT_PMU_NAME "intel_pt"
+
+enum {
+	INTEL_PT_PMU_TYPE,
+	INTEL_PT_TIME_SHIFT,
+	INTEL_PT_TIME_MULT,
+	INTEL_PT_TIME_ZERO,
+	INTEL_PT_CAP_USER_TIME_ZERO,
+	INTEL_PT_TSC_BIT,
+	INTEL_PT_NORETCOMP_BIT,
+	INTEL_PT_HAVE_SCHED_SWITCH,
+	INTEL_PT_SNAPSHOT_MODE,
+	INTEL_PT_PER_CPU_MMAPS,
+	INTEL_PT_MTC_BIT,
+	INTEL_PT_MTC_FREQ_BITS,
+	INTEL_PT_TSC_CTC_N,
+	INTEL_PT_TSC_CTC_D,
+	INTEL_PT_CYC_BIT,
+	INTEL_PT_MAX_NONTURBO_RATIO,
+	INTEL_PT_FILTER_STR_LEN,
+	INTEL_PT_AUXTRACE_PRIV_MAX,
+};
+
+struct auxtrace_record;
+struct perf_tool;
+union perf_event;
+struct perf_session;
+struct perf_event_attr;
+struct perf_pmu;
+
+struct auxtrace_record *intel_pt_recording_init(int *err);
+
+int intel_pt_process_auxtrace_info(union perf_event *event,
+				   struct perf_session *session);
+
+void intel_pt_pmu_default_config(const struct perf_pmu *intel_pt_pmu,
+				 struct perf_event_attr *attr);
+
+#endif