csky: Implement copy_thread_tls

This is required for clone3 which passes the TLS value through a
struct rather than a register.

Cc: Amanieu d'Antras <amanieu@gmail.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

arch/csky/Kconfig

@@ -36,6 +36,7 @@ config CSKY
 	select GX6605S_TIMER if CPU_CK610
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_COPY_THREAD_TLS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER

arch/csky/kernel/process.c

@@ -40,10 +40,11 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
 	return sw->r15;
 }
 
-int copy_thread(unsigned long clone_flags,
+int copy_thread_tls(unsigned long clone_flags,
 		unsigned long usp,
 		unsigned long kthread_arg,
-		struct task_struct *p)
+		struct task_struct *p,
+		unsigned long tls)
 {
 	struct switch_stack *childstack;
 	struct pt_regs *childregs = task_pt_regs(p);
@@ -70,7 +71,7 @@ int copy_thread(unsigned long clone_flags,
 			childregs->usp = usp;
 		if (clone_flags & CLONE_SETTLS)
 			task_thread_info(p)->tp_value = childregs->tls
-						      = childregs->regs[0];
+						      = tls;
 
 		childregs->a0 = 0;
 		childstack->r15 = (unsigned long) ret_from_fork;