perf test: Add a signal handler around running a test

Add a signal handler around running a test. If a signal occurs during
the test a siglongjmp unwinds the stack and output is flushed. The
global run_test_jmp_buf is either unique per forked child or not
shared during sequential execution.

Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Veronika Molnarova <vmolnaro@redhat.com>
Link: https://lore.kernel.org/r/20241025192109.132482-7-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Author: captain5050

tools/perf/tests/builtin-test.c

@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <poll.h>
 #include <unistd.h>
+#include <setjmp.h>
 #include <string.h>
 #include <stdlib.h>
 #include <sys/types.h>
@@ -229,16 +230,41 @@ struct child_test {
 	int subtest;
 };
 
+static jmp_buf run_test_jmp_buf;
+
+static void child_test_sig_handler(int sig)
+{
+	siglongjmp(run_test_jmp_buf, sig);
+}
+
 static int run_test_child(struct child_process *process)
 {
-	struct child_test *child = container_of(process, struct child_test, process);
+	const int signals[] = {
+		SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGINT, SIGPIPE, SIGQUIT, SIGSEGV, SIGTERM,
+	};
+	static struct child_test *child;
 	int err;
 
+	err = sigsetjmp(run_test_jmp_buf, 1);
+	if (err) {
+		fprintf(stderr, "\n---- unexpected signal (%d) ----\n", err);
+		err = err > 0 ? -err : -1;
+		goto err_out;
+	}
+
+	child = container_of(process, struct child_test, process);
+	for (size_t i = 0; i < ARRAY_SIZE(signals); i++)
+		signal(signals[i], child_test_sig_handler);
+
 	pr_debug("--- start ---\n");
 	pr_debug("test child forked, pid %d\n", getpid());
 	err = test_function(child->test, child->subtest)(child->test, child->subtest);
 	pr_debug("---- end(%d) ----\n", err);
+
+err_out:
 	fflush(NULL);
+	for (size_t i = 0; i < ARRAY_SIZE(signals); i++)
+		signal(signals[i], SIG_DFL);
 	return -err;
 }