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, 259 insertions, 0 deletions

diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
new file mode 100644
index 000000000..7cedf05be
--- /dev/null
+++ b/tools/perf/tests/tests.h
@@ -0,0 +1,259 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef TESTS_H
+#define TESTS_H
+
+#include <stdbool.h>
+#include "util/debug.h"
+
+enum {
+	TEST_OK   =  0,
+	TEST_FAIL = -1,
+	TEST_SKIP = -2,
+};
+
+#define TEST_ASSERT_VAL(text, cond)					 \
+do {									 \
+	if (!(cond)) {							 \
+		pr_debug("FAILED %s:%d %s\n", __FILE__, __LINE__, text); \
+		return TEST_FAIL;					 \
+	}								 \
+} while (0)
+
+#define TEST_ASSERT_EQUAL(text, val, expected)				 \
+do {									 \
+	if (val != expected) {						 \
+		pr_debug("FAILED %s:%d %s (%d != %d)\n",		 \
+			 __FILE__, __LINE__, text, val, expected);	 \
+		return TEST_FAIL;						 \
+	}								 \
+} while (0)
+
+struct test_suite;
+
+typedef int (*test_fnptr)(struct test_suite *, int);
+
+struct test_case {
+	const char *name;
+	const char *desc;
+	const char *skip_reason;
+	test_fnptr run_case;
+	bool exclusive;
+	void *priv;
+};
+
+struct test_suite {
+	const char *desc;
+	struct test_case *test_cases;
+	void *priv;
+	int (*setup)(struct test_suite *suite);
+};
+
+#define DECLARE_SUITE(name) \
+	extern struct test_suite suite__##name;
+
+#define TEST_CASE(description, _name)			\
+	{						\
+		.name = #_name,				\
+		.desc = description,			\
+		.run_case = test__##_name,		\
+	}
+
+#define TEST_CASE_REASON(description, _name, _reason)	\
+	{						\
+		.name = #_name,				\
+		.desc = description,			\
+		.run_case = test__##_name,		\
+		.skip_reason = _reason,			\
+	}
+
+#define TEST_CASE_EXCLUSIVE(description, _name)		\
+	{						\
+		.name = #_name,				\
+		.desc = description,			\
+		.run_case = test__##_name,		\
+		.exclusive = true,			\
+	}
+
+#define TEST_CASE_REASON_EXCLUSIVE(description, _name, _reason)	\
+	{						\
+		.name = #_name,				\
+		.desc = description,			\
+		.run_case = test__##_name,		\
+		.skip_reason = _reason,			\
+		.exclusive = true,			\
+	}
+
+#define DEFINE_SUITE(description, _name)		\
+	struct test_case tests__##_name[] = {           \
+		TEST_CASE(description, _name),		\
+		{	.name = NULL, }			\
+	};						\
+	struct test_suite suite__##_name = {		\
+		.desc = description,			\
+		.test_cases = tests__##_name,		\
+	}
+
+#define DEFINE_SUITE_EXCLUSIVE(description, _name)	\
+	struct test_case tests__##_name[] = {           \
+		TEST_CASE_EXCLUSIVE(description, _name),\
+		{	.name = NULL, }			\
+	};						\
+	struct test_suite suite__##_name = {		\
+		.desc = description,			\
+		.test_cases = tests__##_name,		\
+	}
+
+/* Tests */
+DECLARE_SUITE(vmlinux_matches_kallsyms);
+DECLARE_SUITE(openat_syscall_event);
+DECLARE_SUITE(openat_syscall_event_on_all_cpus);
+DECLARE_SUITE(basic_mmap);
+DECLARE_SUITE(PERF_RECORD);
+DECLARE_SUITE(perf_evsel__roundtrip_name_test);
+DECLARE_SUITE(perf_evsel__tp_sched_test);
+DECLARE_SUITE(syscall_openat_tp_fields);
+DECLARE_SUITE(pmu);
+DECLARE_SUITE(pmu_events);
+DECLARE_SUITE(hwmon_pmu);
+DECLARE_SUITE(tool_pmu);
+DECLARE_SUITE(attr);
+DECLARE_SUITE(dso_data);
+DECLARE_SUITE(dso_data_cache);
+DECLARE_SUITE(dso_data_reopen);
+DECLARE_SUITE(parse_events);
+DECLARE_SUITE(hists_link);
+DECLARE_SUITE(bp_signal);
+DECLARE_SUITE(bp_signal_overflow);
+DECLARE_SUITE(bp_accounting);
+DECLARE_SUITE(wp);
+DECLARE_SUITE(task_exit);
+DECLARE_SUITE(mem);
+DECLARE_SUITE(sw_clock_freq);
+DECLARE_SUITE(code_reading);
+DECLARE_SUITE(sample_parsing);
+DECLARE_SUITE(keep_tracking);
+DECLARE_SUITE(parse_no_sample_id_all);
+DECLARE_SUITE(dwarf_unwind);
+DECLARE_SUITE(expr);
+DECLARE_SUITE(hists_filter);
+DECLARE_SUITE(mmap_thread_lookup);
+DECLARE_SUITE(thread_maps_share);
+DECLARE_SUITE(hists_output);
+DECLARE_SUITE(hists_cumulate);
+DECLARE_SUITE(switch_tracking);
+DECLARE_SUITE(fdarray__filter);
+DECLARE_SUITE(fdarray__add);
+DECLARE_SUITE(kmod_path__parse);
+DECLARE_SUITE(thread_map);
+DECLARE_SUITE(bpf);
+DECLARE_SUITE(session_topology);
+DECLARE_SUITE(thread_map_synthesize);
+DECLARE_SUITE(thread_map_remove);
+DECLARE_SUITE(cpu_map);
+DECLARE_SUITE(synthesize_stat_config);
+DECLARE_SUITE(synthesize_stat);
+DECLARE_SUITE(synthesize_stat_round);
+DECLARE_SUITE(event_update);
+DECLARE_SUITE(event_times);
+DECLARE_SUITE(backward_ring_buffer);
+DECLARE_SUITE(sdt_event);
+DECLARE_SUITE(is_printable_array);
+DECLARE_SUITE(bitmap_print);
+DECLARE_SUITE(perf_hooks);
+DECLARE_SUITE(unit_number__scnprint);
+DECLARE_SUITE(mem2node);
+DECLARE_SUITE(maps);
+DECLARE_SUITE(time_utils);
+DECLARE_SUITE(jit_write_elf);
+DECLARE_SUITE(api_io);
+DECLARE_SUITE(demangle_java);
+DECLARE_SUITE(demangle_ocaml);
+DECLARE_SUITE(demangle_rust);
+DECLARE_SUITE(pfm);
+DECLARE_SUITE(parse_metric);
+DECLARE_SUITE(pe_file_parsing);
+DECLARE_SUITE(expand_cgroup_events);
+DECLARE_SUITE(perf_time_to_tsc);
+DECLARE_SUITE(dlfilter);
+DECLARE_SUITE(sigtrap);
+DECLARE_SUITE(event_groups);
+DECLARE_SUITE(symbols);
+DECLARE_SUITE(util);
+DECLARE_SUITE(uncore_event_sorting);
+DECLARE_SUITE(subcmd_help);
+DECLARE_SUITE(kallsyms_split);
+
+/*
+ * PowerPC and S390 do not support creation of instruction breakpoints using the
+ * perf_event interface.
+ *
+ * ARM requires explicit rounding down of the instruction pointer in Thumb mode,
+ * and then requires the single-step to be handled explicitly in the overflow
+ * handler to avoid stepping into the SIGIO handler and getting stuck on the
+ * breakpointed instruction.
+ *
+ * Since arm64 has the same issue with arm for the single-step handling, this
+ * case also gets stuck on the breakpointed instruction.
+ *
+ * Just disable the test for these architectures until these issues are
+ * resolved.
+ */
+#if defined(__powerpc__) || defined(__s390x__) || defined(__arm__) || defined(__aarch64__)
+#define BP_SIGNAL_IS_SUPPORTED 0
+#else
+#define BP_SIGNAL_IS_SUPPORTED 1
+#endif
+
+#ifdef HAVE_DWARF_UNWIND_SUPPORT
+struct thread;
+struct perf_sample;
+int test__arch_unwind_sample(struct perf_sample *sample,
+			     struct thread *thread);
+#endif
+
+#if defined(__arm__)
+DECLARE_SUITE(vectors_page);
+#endif
+
+/*
+ * Define test workloads to be used in test suites.
+ */
+typedef int (*workload_fnptr)(int argc, const char **argv);
+
+struct test_workload {
+	const char	*name;
+	workload_fnptr	func;
+};
+
+#define DECLARE_WORKLOAD(work) \
+	extern struct test_workload workload__##work
+
+#define DEFINE_WORKLOAD(work) \
+struct test_workload workload__##work = {	\
+	.name = #work,				\
+	.func = work,				\
+}
+
+/* The list of test workloads */
+DECLARE_WORKLOAD(noploop);
+DECLARE_WORKLOAD(thloop);
+DECLARE_WORKLOAD(named_threads);
+DECLARE_WORKLOAD(leafloop);
+DECLARE_WORKLOAD(sqrtloop);
+DECLARE_WORKLOAD(brstack);
+DECLARE_WORKLOAD(datasym);
+DECLARE_WORKLOAD(landlock);
+DECLARE_WORKLOAD(traploop);
+DECLARE_WORKLOAD(inlineloop);
+DECLARE_WORKLOAD(jitdump);
+DECLARE_WORKLOAD(context_switch_loop);
+DECLARE_WORKLOAD(deterministic);
+
+#ifdef HAVE_RUST_SUPPORT
+DECLARE_WORKLOAD(code_with_type);
+#endif
+
+extern const char *dso_to_test;
+extern const char *test_objdump_path;
+
+#endif /* TESTS_H */