[PATCH v3 9/9] perf test: Isolate test suite from user .perfconfig natively

[Ian Rogers <irogers@google.com>]

Running 'perf test' should not inherit the user's ~/.perfconfig
environment as customizing core properties (like core.hybrid-merge)
will trivially break stdout matching checks across the shell suite.

Explicitly set PERF_CONFIG to /dev/null inside cmd_test to globally
sandbox the environment for the entire test workflow. Test specific
config, like annotate.objdump, is read before the sandboxing so that
'perf test' still honors it.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3.1-pro
---
 tools/perf/tests/builtin-test.c | 49 +++++++++++++++++++++++++++++----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 6293b37266cf..2d53414d8271 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -14,6 +14,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "util/config.h"
+
 #include <dirent.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
@@ -1655,11 +1657,30 @@ static int run_workload(const char *work, int argc, const char **argv)
 	return -1;
 }
 
+/*
+ * Owns the string test_objdump_path points at when it came from the config. It
+ * is reachable for the lifetime of the process so leak checking won't report
+ * it.
+ */
+static char *test_objdump_config_path;
+
 static int perf_test__config(const char *var, const char *value,
 			     void *data __maybe_unused)
 {
-	if (!strcmp(var, "annotate.objdump"))
-		test_objdump_path = value;
+	if (!strcmp(var, "annotate.objdump")) {
+		/*
+		 * The config, and so value, is freed by perf_config__exit()
+		 * below, take a copy that lives as long as the tests.
+		 */
+		char *dup = strdup(value);
+
+		if (!dup)
+			return -ENOMEM;
+
+		free(test_objdump_config_path);
+		test_objdump_config_path = dup;
+		test_objdump_path = dup;
+	}
 
 	return 0;
 }
@@ -1755,13 +1776,31 @@ int cmd_test(int argc, const char **argv)
 	};
 	const char * const test_subcommands[] = { "list", NULL };
 	struct intlist *skiplist = NULL;
-        int ret = hists__init();
 	struct test_suite **suites;
+	int ret;
 
-        if (ret < 0)
+	ret = hists__init();
+	if (ret < 0)
                 return ret;
 
-	perf_config(perf_test__config, NULL);
+	/* Read test related config, like annotate.objdump, before isolating. */
+	ret = perf_config(perf_test__config, NULL);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Isolate the test suite from the user's ~/.perfconfig to ensure
+	 * behavior isn't impacted by custom variables (e.g. core.hybrid-merge).
+	 * Setting PERF_CONFIG isolates the perf commands run by the shell
+	 * tests, config_exclusive_filename does the same for this process.
+	 * Config values already read by main's perf_config are reset here, so
+	 * far only the hybrid-merge value is known to alter test output.
+	 */
+	if (setenv("PERF_CONFIG", "/dev/null", 1) < 0)
+		return -1;
+	config_exclusive_filename = "/dev/null";
+	perf_config__exit();
+	symbol_conf.hybrid_merge = false;
 
 	/* Unbuffered output */
 	setvbuf(stdout, NULL, _IONBF, 0);
-- 
2.55.0.1082.g2b9226bbc0-goog