[ALPHA] Fix SETTLS -- read TLS value to install before clobbering it.

arch/alpha/kernel/process.c

@@ -270,7 +270,7 @@ copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 	struct thread_info *childti = p->thread_info;
 	struct pt_regs * childregs;
 	struct switch_stack * childstack, *stack;
-	unsigned long stack_offset;
+	unsigned long stack_offset, settls;
 
 	stack_offset = PAGE_SIZE - sizeof(struct pt_regs);
 	if (!(regs->ps & 8))
@@ -279,6 +279,7 @@ copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 	  (stack_offset + PAGE_SIZE + (long) childti);
 		
 	*childregs = *regs;
+	settls = regs->r20;
 	childregs->r0 = 0;
 	childregs->r19 = 0;
 	childregs->r20 = 1;	/* OSF/1 has some strange fork() semantics.  */
@@ -292,14 +293,16 @@ copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 	childti->pcb.flags = 1;	/* set FEN, clear everything else */
 
 	/* Set a new TLS for the child thread?  Peek back into the
-	   syscall arguments that we saved on syscall entry.  */
+	   syscall arguments that we saved on syscall entry.  Oops,
+	   except we'd have clobbered it with the parent/child set
+	   of r20.  Read the saved copy.  */
 	/* Note: if CLONE_SETTLS is not set, then we must inherit the
 	   value from the parent, which will have been set by the block
 	   copy in dup_task_struct.  This is non-intuitive, but is
 	   required for proper operation in the case of a threaded
 	   application calling fork.  */
 	if (clone_flags & CLONE_SETTLS)
-		childti->pcb.unique = regs->r20;
+		childti->pcb.unique = settls;
 
 	return 0;
 }