core: add valgrind helper for daemon-reexec

Inspired by https://github.com/systemd/systemd/issues/2187#issuecomment-165587140

src/basic/process-util.c

@@ -33,6 +33,9 @@
 #include <sys/wait.h>
 #include <syslog.h>
 #include <unistd.h>
+#ifdef HAVE_VALGRIND_VALGRIND_H
+#include <valgrind/valgrind.h>
+#endif
 
 #include "alloc-util.h"
 #include "escape.h"
@@ -730,6 +733,23 @@ const char* personality_to_string(unsigned long p) {
         return NULL;
 }
 
+void valgrind_summary_hack(void) {
+#ifdef HAVE_VALGRIND_VALGRIND_H
+        if (getpid() == 1 && RUNNING_ON_VALGRIND) {
+                pid_t pid;
+                pid = raw_clone(SIGCHLD, NULL);
+                if (pid < 0)
+                        log_emergency_errno(errno, "Failed to fork off valgrind helper: %m");
+                else if (pid == 0)
+                        exit(EXIT_SUCCESS);
+                else {
+                        log_info("Spawned valgrind helper as PID "PID_FMT".", pid);
+                        (void) wait_for_terminate(pid, NULL);
+                }
+        }
+#endif
+}
+
 static const char *const ioprio_class_table[] = {
         [IOPRIO_CLASS_NONE] = "none",
         [IOPRIO_CLASS_RT] = "realtime",