m68knommu: define arch_has_single_step() and friends

Towards adding CONFIG_UTRACE support for non-mmu m68k add
arch_has_single_step, and its support functions user_enable_single_step()
and user_disable_single_step().

Signed-off-by: Greg Ungerer <gerg@uclinux.org>

arch/m68k/include/asm/ptrace.h

@@ -82,6 +82,18 @@ struct switch_stack {
 #define instruction_pointer(regs) ((regs)->pc)
 #define profile_pc(regs) instruction_pointer(regs)
 extern void show_regs(struct pt_regs *);
+
+/*
+ * These are defined as per linux/ptrace.h.
+ */
+struct task_struct;
+
+#ifndef CONFIG_MMU
+#define	arch_has_single_step()	(1)
+extern void user_enable_single_step(struct task_struct *);
+extern void user_disable_single_step(struct task_struct *);
+#endif
+
 #endif /* __KERNEL__ */
 #endif /* __ASSEMBLY__ */
 #endif /* _M68K_PTRACE_H */

arch/m68knommu/kernel/ptrace.c

@@ -86,17 +86,29 @@ static inline int put_reg(struct task_struct *task, int regno,
 	return 0;
 }
 
+void user_enable_single_step(struct task_struct *task)
+{
+	unsigned long srflags;
+	srflags = get_reg(task, PT_SR) | (TRACE_BITS << 16);
+	put_reg(task, PT_SR, srflags);
+}
+
+void user_disable_single_step(struct task_struct *task)
+{
+	unsigned long srflags;
+	srflags = get_reg(task, PT_SR) & ~(TRACE_BITS << 16);
+	put_reg(task, PT_SR, srflags);
+}
+
 /*
  * Called by kernel/ptrace.c when detaching..
  *
  * Make sure the single step bit is not set.
  */
 void ptrace_disable(struct task_struct *child)
 {
-	unsigned long tmp;
 	/* make sure the single step bit is not set. */
-	tmp = get_reg(child, PT_SR) & ~(TRACE_BITS << 16);
-	put_reg(child, PT_SR, tmp);
+	user_disable_single_step(child);
 }
 
 long arch_ptrace(struct task_struct *child, long request, long addr, long data)