utils: Add print_stack_trace()

Function to print call trace of a process.

Borrowed from this fm:
https://www.gnu.org/software/libc/manual/html_node/Backtraces.html

backtrace() and backtrace_symbols() are not implemented in alpine,
so we use __GLIBC__ ifdef to do not compile this function there.

v4: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/include/util.h

@@ -348,6 +348,11 @@ extern int epoll_run_rfds(int epfd, struct epoll_event *evs, int nr_fds, int tmo
 extern int epoll_prepare(int nr_events, struct epoll_event **evs);
 
 extern int call_in_child_process(int (*fn)(void *), void *arg);
+#ifdef __GLIBC__
+extern void print_stack_trace(pid_t pid);
+#else
+static inline void print_stack_trace(pid_t pid) {}
+#endif
 
 #define block_sigmask(saved_mask, sig_mask)	({					\
 		sigset_t ___blocked_mask;						\

criu/util.c

@@ -1407,3 +1407,21 @@ out:
 	close_pid_proc();
 	return ret;
 }
+
+#ifdef __GLIBC__
+#include <execinfo.h>
+void print_stack_trace(pid_t pid)
+{
+	void *array[10];
+	char **strings;
+	size_t size, i;
+
+	size = backtrace(array, 10);
+	strings = backtrace_symbols(array, size);
+
+	for (i = 0; i < size; i++)
+		pr_err("stack %d#%zu: %s\n", pid, i, strings[i]);
+
+	free(strings);
+}
+#endif