[PATCH v1 4/6] perf test demangle-rust: Add Rust demangling test

[Ian Rogers <irogers@google.com>]

The test cases are listed examples in:
https://doc.rust-lang.org/rustc/symbol-mangling/v0.html

This test was previously part of a different Rust v0 demangler:
https://lore.kernel.org/lkml/20250129193037.573431-1-irogers@google.com/

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/Build                   |  1 +
 tools/perf/tests/builtin-test.c          |  1 +
 tools/perf/tests/demangle-rust-v0-test.c | 74 ++++++++++++++++++++++++
 tools/perf/tests/tests.h                 |  1 +
 tools/perf/util/symbol-elf.c             |  4 +-
 5 files changed, 79 insertions(+), 2 deletions(-)
 create mode 100644 tools/perf/tests/demangle-rust-v0-test.c

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index 934f32090553..2181f5a92148 100644
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -56,6 +56,7 @@ perf-test-y += genelf.o
 perf-test-y += api-io.o
 perf-test-y += demangle-java-test.o
 perf-test-y += demangle-ocaml-test.o
+perf-test-y += demangle-rust-v0-test.o
 perf-test-y += pfm.o
 perf-test-y += parse-metric.o
 perf-test-y += pe-file-parsing.o
diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 14d30a5053be..45d3d8b3317a 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -126,6 +126,7 @@ static struct test_suite *generic_tests[] = {
 	&suite__maps__merge_in,
 	&suite__demangle_java,
 	&suite__demangle_ocaml,
+	&suite__demangle_rust,
 	&suite__parse_metric,
 	&suite__pe_file_parsing,
 	&suite__expand_cgroup_events,
diff --git a/tools/perf/tests/demangle-rust-v0-test.c b/tools/perf/tests/demangle-rust-v0-test.c
new file mode 100644
index 000000000000..efbc0fc25ffc
--- /dev/null
+++ b/tools/perf/tests/demangle-rust-v0-test.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#include "tests.h"
+#include "debug.h"
+#include "symbol.h"
+#include <linux/kernel.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int test__demangle_rust(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	int ret = TEST_OK;
+	char *buf = NULL;
+	size_t i;
+
+	struct {
+		const char *mangled, *demangled;
+	} test_cases[] = {
+		{ "_RNvMsr_NtCs3ssYzQotkvD_3std4pathNtB5_7PathBuf3newCs15kBYyAo9fc_7mycrate",
+		  "<std::path::PathBuf>::new" },
+		{ "_RNvCs15kBYyAo9fc_7mycrate7example",
+		  "mycrate::example" },
+		{ "_RNvMs_Cs4Cv8Wi1oAIB_7mycrateNtB4_7Example3foo",
+		  "<mycrate::Example>::foo" },
+		{ "_RNvXCs15kBYyAo9fc_7mycrateNtB2_7ExampleNtB2_5Trait3foo",
+		  "<mycrate::Example as mycrate::Trait>::foo" },
+		{ "_RNvMCs7qp2U7fqm6G_7mycrateNtB2_7Example3foo",
+		  "<mycrate::Example>::foo" },
+		{ "_RNvMs_Cs7qp2U7fqm6G_7mycrateNtB4_7Example3bar",
+		  "<mycrate::Example>::bar" },
+		{ "_RNvYNtCs15kBYyAo9fc_7mycrate7ExampleNtB4_5Trait7exampleB4_",
+		  "<mycrate::Example as mycrate::Trait>::example" },
+		{ "_RNCNvCsgStHSCytQ6I_7mycrate4main0B3_",
+		  "mycrate::main::{closure#0}" },
+		{ "_RNCNvCsgStHSCytQ6I_7mycrate4mains_0B3_",
+		  "mycrate::main::{closure#1}" },
+		{ "_RINvCsgStHSCytQ6I_7mycrate7examplelKj1_EB2_",
+		  "mycrate::example::<i32, 1>" },
+		{ "_RINvCs7qp2U7fqm6G_7mycrate7exampleFG0_RL1_hRL0_tEuEB2_",
+		  "mycrate::example::<for<'a, 'b> fn(&'a u8, &'b u16)>",
+		},
+		{ "_RINvCs7qp2U7fqm6G_7mycrate7exampleKy12345678_EB2_",
+		  "mycrate::example::<305419896>" },
+		{ "_RNvNvMCsd9PVOYlP1UU_7mycrateINtB4_7ExamplepKpE3foo14EXAMPLE_STATIC",
+		  "<mycrate::Example<_, _>>::foo::EXAMPLE_STATIC",
+		},
+		{ "_RINvCs7qp2U7fqm6G_7mycrate7exampleAtj8_EB2_",
+		  "mycrate::example::<[u16; 8]>" },
+		{ "_RINvCs7qp2U7fqm6G_7mycrate7exampleNtB2_7ExampleBw_EB2_",
+		  "mycrate::example::<mycrate::Example, mycrate::Example>" },
+		{ "_RINvMsY_NtCseXNvpPnDBDp_3std4pathNtB6_4Path3neweECs7qp2U7fqm6G_7mycrate",
+		  "<std::path::Path>::new::<str>" },
+		{ "_RNvNvNvCs7qp2U7fqm6G_7mycrate7EXAMPLE7___getit5___KEY",
+		  "mycrate::EXAMPLE::__getit::__KEY" },
+	};
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		buf = dso__demangle_sym(/*dso=*/NULL, /*kmodule=*/0, test_cases[i].mangled);
+		if (!buf) {
+			pr_debug("FAILED to demangle: \"%s\"\n \"%s\"\n", test_cases[i].mangled,
+				 test_cases[i].demangled);
+			continue;
+		}
+		if (strcmp(buf, test_cases[i].demangled)) {
+			pr_debug("FAILED: %s: %s != %s\n", test_cases[i].mangled,
+				 buf, test_cases[i].demangled);
+			ret = TEST_FAIL;
+		}
+		free(buf);
+	}
+
+	return ret;
+}
+
+DEFINE_SUITE("Demangle Rust", demangle_rust);
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 8aea344536b8..bb7951c61971 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -157,6 +157,7 @@ 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);
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index f953868521f2..8734e8b6cf84 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -319,7 +319,7 @@ static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
 	 * DWARF DW_compile_unit has this, but we don't always have access
 	 * to it...
 	 */
-	if (!want_demangle(dso__kernel(dso) || kmodule))
+	if (!want_demangle((dso && dso__kernel(dso)) || kmodule))
 		return demangled;
 
 	rust_demangle_demangle(elf_name, &rust_demangle);
@@ -338,7 +338,7 @@ static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
 			}
 			demangled = tmp;
 			if (rust_demangle_display_demangle(&rust_demangle, demangled, buf_len,
-							   /*alternate=*/false) == OverflowOk)
+							   /*alternate=*/true) == OverflowOk)
 				return demangled;
 		}
 		/* Buffer exceeded sensible bounds, return what is there. */
-- 
2.49.0.901.g37484f566f-goog