[CRIU] [PATCH v2 2/3] utils: Add sys_clone_unified()

[Kirill Tkhai]

Cleanup fork() definition and make a generic function
for all archs. It may be useful, when you want to add
more clone flags to fork(), or if you want to pass more,
than one argument to child function (glibc's clone
alows only one).

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 criu/include/util.h  |    3 +++
 criu/util.c          |   25 +++++++++++++++----------
 test/zdtm/lib/test.c |   23 ++++++++++++++---------
 3 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/criu/include/util.h b/criu/include/util.h
index ea915501c..48710ebff 100644
--- a/criu/include/util.h
+++ b/criu/include/util.h
@@ -61,6 +61,9 @@ extern int open_pid_proc(pid_t pid);
 extern int close_pid_proc(void);
 extern int set_proc_fd(int fd);
 
+extern pid_t sys_clone_unified(unsigned long flags, void *child_stack, void *parent_tid,
+			       void *child_tid, unsigned long newtls);
+
 /*
  * Values for pid argument of the proc opening routines below.
  * SELF would open file under /proc/self
diff --git a/criu/util.c b/criu/util.c
index 563dbd50b..84fcc80a4 100644
--- a/criu/util.c
+++ b/criu/util.c
@@ -1433,20 +1433,25 @@ int getpid()
        return syscall(__NR_getpid);
 }
 
+pid_t sys_clone_unified(unsigned long flags, void *child_stack, void *parent_tid,
+			void *child_tid, unsigned long newtls)
+{
+#ifdef __x86_64__
+	return (pid_t)syscall(__NR_clone, flags, child_stack, parent_tid, child_tid, newtls);
+#elif (__i386__ || __arm__ || __aarch64__ || __powerpc64__)
+	return (pid_t)syscall(__NR_clone, flags, child_stack, parent_tid, newtls, child_tid);
+#elif __s390x__
+	return (pid_t)syscall(__NR_clone, child_stack, flags, parent_tid, child_tid, newtls);
+#else
+#error "Unsupported architecture"
+#endif
+}
+
 /*
  * In glibc 2.24, fork() may fail when parent and child are
  * from different pid namespaces and have the same pid.
  */
 pid_t fork()
 {
-	/*
-	 * Two last arguments are swapped on different archs,
-	 * but we don't care as they are zero anyway.
-	 */
-#ifdef __s390x__
-	/* See kernel/fork.c: CONFIG_CLONE_BACKWARDS2 */
-	return (pid_t)syscall(__NR_clone, 0, SIGCHLD, NULL, 0, NULL);
-#else
-	return (pid_t)syscall(__NR_clone, SIGCHLD, 0, 0, 0, 0);
-#endif
+	return sys_clone_unified(SIGCHLD, 0, NULL, NULL, 0);
 }
diff --git a/test/zdtm/lib/test.c b/test/zdtm/lib/test.c
index 5f1208399..620dcfce6 100644
--- a/test/zdtm/lib/test.c
+++ b/test/zdtm/lib/test.c
@@ -286,20 +286,25 @@ void test_waitsig(void)
 	futex_wait_while(&sig_received, 0);
 }
 
-pid_t fork()
+pid_t sys_clone_unified(unsigned long flags, void *child_stack, void *parent_tid,
+			void *child_tid, unsigned long newtls)
 {
-	/*
-	 * Two last arguments are swapped on different archs,
-	 * but we don't care as they are zero anyway.
-	 */
-#ifdef __s390x__
-	/* See kernel/fork.c: CONFIG_CLONE_BACKWARDS2 */
-	return (pid_t)syscall(__NR_clone, 0, SIGCHLD, NULL, 0, NULL);
+#ifdef __x86_64__
+	return (pid_t)syscall(__NR_clone, flags, child_stack, parent_tid, child_tid, newtls);
+#elif (__i386__ || __arm__ || __aarch64__ ||__powerpc64__)
+	return (pid_t)syscall(__NR_clone, flags, child_stack, parent_tid, newtls, child_tid);
+#elif __s390x__
+	return (pid_t)syscall(__NR_clone, child_stack, flags, parent_tid, child_tid, newtls);
 #else
-	return (pid_t)syscall(__NR_clone, SIGCHLD, 0, 0, 0, 0);
+#error "Unsupported architecture"
 #endif
 }
 
+pid_t fork()
+{
+	return sys_clone_unified(SIGCHLD, NULL, NULL, NULL, 0);
+}
+
 int getpid()
 {
        return syscall(__NR_getpid);