perf test: Add Symbols test

Add a test to check function symbols do not overlap and are not zero
length.

The main motivation for the test is to make it easier to review changes
to PLT symbol synthesis i.e. changes to dso__synthesize_plt_symbols().

By default the test uses the perf executable as a test DSO, but a
specific DSO can be specified via a new perf test option "--dso".

The test is useful in the following ways:

 - Any DSO can be tested, even ones that do not run on the current
 architecture. For example, using cross-compiled DSOs to see how
 well perf handles different architectures.

 - With verbose > 1 (e.g. -vv), all the symbols are printed, which
 makes it easier to see issues.

 - perf removes duplicate symbols and expands zero-length symbols
 to reach the next symbol, however that is done before adding
 synthesized symbols, so the test is checking those also.

Example:

  $ perf test -v Symbols
   74: Symbols                                                         :
  --- start ---
  test child forked, pid 154918
  Testing /home/user/bin/perf
  Overlapping symbols:
   7d000-7f3a0 g _init
   7d030-7d040 g __printf_chk@plt
  test child finished with -1
  ---- end ----
  Symbols: FAILED!

Note the test fails because perf expands the _init symbol over the PLT
because there are no PLT symbols at that point, but then
dso__synthesize_plt_symbols() creates them.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20230120123456.12449-2-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-test.txt

@@ -34,3 +34,6 @@ OPTIONS
 -F::
 --dont-fork::
 	Do not fork child for each test, run all tests within single process.
+
+--dso::
+	Specify a DSO for the "Symbols" test.

tools/perf/tests/Build

@@ -68,6 +68,7 @@ perf-y += perf-time-to-tsc.o
 perf-y += dlfilter-test.o
 perf-y += sigtrap.o
 perf-y += event_groups.o
+perf-y += symbols.o
 
 $(OUTPUT)tests/llvm-src-base.c: tests/bpf-script-example.c tests/Build
 	$(call rule_mkdir)

tools/perf/tests/builtin-test.c

@@ -31,6 +31,7 @@
 #include "builtin-test-list.h"
 
 static bool dont_fork;
+const char *dso_to_test;
 
 struct test_suite *__weak arch_tests[] = {
 	NULL,
@@ -117,6 +118,7 @@ static struct test_suite *generic_tests[] = {
 	&suite__dlfilter,
 	&suite__sigtrap,
 	&suite__event_groups,
+	&suite__symbols,
 	NULL,
 };
 
@@ -521,6 +523,7 @@ int cmd_test(int argc, const char **argv)
 	OPT_BOOLEAN('F', "dont-fork", &dont_fork,
 		    "Do not fork for testcase"),
 	OPT_STRING('w', "workload", &workload, "work", "workload to run for testing"),
+	OPT_STRING(0, "dso", &dso_to_test, "dso", "dso to test"),
 	OPT_END()
 	};
 	const char * const test_subcommands[] = { "list", NULL };

tools/perf/tests/symbols.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <linux/string.h>
+#include <sys/mman.h>
+#include <limits.h>
+#include "debug.h"
+#include "dso.h"
+#include "machine.h"
+#include "thread.h"
+#include "symbol.h"
+#include "map.h"
+#include "util.h"
+#include "tests.h"
+
+struct test_info {
+	struct machine *machine;
+	struct thread *thread;
+};
+
+static int init_test_info(struct test_info *ti)
+{
+	ti->machine = machine__new_host();
+	if (!ti->machine) {
+		pr_debug("machine__new_host() failed!\n");
+		return TEST_FAIL;
+	}
+
+	/* Create a dummy thread */
+	ti->thread = machine__findnew_thread(ti->machine, 100, 100);
+	if (!ti->thread) {
+		pr_debug("machine__findnew_thread() failed!\n");
+		return TEST_FAIL;
+	}
+
+	return TEST_OK;
+}
+
+static void exit_test_info(struct test_info *ti)
+{
+	thread__put(ti->thread);
+	machine__delete(ti->machine);
+}
+
+static void get_test_dso_filename(char *filename, size_t max_sz)
+{
+	if (dso_to_test)
+		strlcpy(filename, dso_to_test, max_sz);
+	else
+		perf_exe(filename, max_sz);
+}
+
+static int create_map(struct test_info *ti, char *filename, struct map **map_p)
+{
+	/* Create a dummy map at 0x100000 */
+	*map_p = map__new(ti->machine, 0x100000, 0xffffffff, 0, NULL,
+			  PROT_EXEC, 0, NULL, filename, ti->thread);
+	if (!*map_p) {
+		pr_debug("Failed to create map!");
+		return TEST_FAIL;
+	}
+
+	return TEST_OK;
+}
+
+static int test_dso(struct dso *dso)
+{
+	struct symbol *last_sym = NULL;
+	struct rb_node *nd;
+	int ret = TEST_OK;
+
+	/* dso__fprintf() prints all the symbols */
+	if (verbose > 1)
+		dso__fprintf(dso, stderr);
+
+	for (nd = rb_first_cached(&dso->symbols); nd; nd = rb_next(nd)) {
+		struct symbol *sym = rb_entry(nd, struct symbol, rb_node);
+
+		if (sym->type != STT_FUNC && sym->type != STT_GNU_IFUNC)
+			continue;
+
+		/* Check for overlapping function symbols */
+		if (last_sym && sym->start < last_sym->end) {
+			pr_debug("Overlapping symbols:\n");
+			symbol__fprintf(last_sym, stderr);
+			symbol__fprintf(sym, stderr);
+			ret = TEST_FAIL;
+		}
+		/* Check for zero-length function symbol */
+		if (sym->start == sym->end) {
+			pr_debug("Zero-length symbol:\n");
+			symbol__fprintf(sym, stderr);
+			ret = TEST_FAIL;
+		}
+		last_sym = sym;
+	}
+
+	return ret;
+}
+
+static int test_file(struct test_info *ti, char *filename)
+{
+	struct map *map = NULL;
+	int ret, nr;
+
+	pr_debug("Testing %s\n", filename);
+
+	ret = create_map(ti, filename, &map);
+	if (ret != TEST_OK)
+		return ret;
+
+	nr = dso__load(map->dso, map);
+	if (nr < 0) {
+		pr_debug("dso__load() failed!\n");
+		ret = TEST_FAIL;
+		goto out_put;
+	}
+
+	if (nr == 0) {
+		pr_debug("DSO has no symbols!\n");
+		ret = TEST_SKIP;
+		goto out_put;
+	}
+
+	ret = test_dso(map->dso);
+out_put:
+	map__put(map);
+
+	return ret;
+}
+
+static int test__symbols(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	char filename[PATH_MAX];
+	struct test_info ti;
+	int ret;
+
+	ret = init_test_info(&ti);
+	if (ret != TEST_OK)
+		return ret;
+
+	get_test_dso_filename(filename, sizeof(filename));
+
+	ret = test_file(&ti, filename);
+
+	exit_test_info(&ti);
+
+	return ret;
+}
+
+DEFINE_SUITE("Symbols", symbols);

tools/perf/tests/tests.h

@@ -148,6 +148,7 @@ DECLARE_SUITE(perf_time_to_tsc);
 DECLARE_SUITE(dlfilter);
 DECLARE_SUITE(sigtrap);
 DECLARE_SUITE(event_groups);
+DECLARE_SUITE(symbols);
 
 /*
  * PowerPC and S390 do not support creation of instruction breakpoints using the
@@ -208,4 +209,6 @@ DECLARE_WORKLOAD(sqrtloop);
 DECLARE_WORKLOAD(brstack);
 DECLARE_WORKLOAD(datasym);
 
+extern const char *dso_to_test;
+
 #endif /* TESTS_H */