s390: opt into HAVE_COPY_THREAD_TLS

This the s390 version of commit c1bd55f9 ("x86: opt into
HAVE_COPY_THREAD_TLS, for both 32-bit and 64-bit").

Simply use the tls system call argument instead of extracting the tls
argument by magic from the pt_regs structure.

See commit 3033f14a ("clone: support passing tls argument via C
rather than pt_regs magic") for more background.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -134,6 +134,7 @@ config S390
 	select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
+	select HAVE_COPY_THREAD_TLS
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_API_DEBUG
 	select HAVE_DMA_CONTIGUOUS

arch/s390/kernel/process.c

@@ -100,8 +100,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 	return 0;
 }
 
-int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
-		unsigned long arg, struct task_struct *p)
+int copy_thread_tls(unsigned long clone_flags, unsigned long new_stackp,
+		    unsigned long arg, struct task_struct *p, unsigned long tls)
 {
 	struct fake_frame
 	{
@@ -156,7 +156,6 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
 
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS) {
-		unsigned long tls = frame->childregs.gprs[6];
 		if (is_compat_task()) {
 			p->thread.acrs[0] = (unsigned int)tls;
 		} else {