ptrace: generic PTRACE_SINGLEBLOCK

This makes ptrace_request handle PTRACE_SINGLEBLOCK along with
PTRACE_CONT et al.  The new generic code makes use of the
arch_has_block_step macro and generic entry points on machines
that define them.

[ mingo@elte.hu: bugfix ]
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/ptrace.h

@@ -187,7 +187,7 @@ static inline void user_disable_single_step(struct task_struct *task)
  * supports step-until-branch for user mode.  It can be a constant or it
  * can test a CPU feature bit.
  */
-#define arch_has_single_step()		(0)
+#define arch_has_block_step()		(0)
 
 /**
  * user_enable_block_step - step until branch in user-mode task

kernel/ptrace.c

@@ -373,6 +373,12 @@ static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
 #define is_singlestep(request)		0
 #endif
 
+#ifdef PTRACE_SINGLEBLOCK
+#define is_singleblock(request)		((request) == PTRACE_SINGLEBLOCK)
+#else
+#define is_singleblock(request)		0
+#endif
+
 #ifdef PTRACE_SYSEMU
 #define is_sysemu_singlestep(request)	((request) == PTRACE_SYSEMU_SINGLESTEP)
 #else
@@ -396,7 +402,11 @@ static int ptrace_resume(struct task_struct *child, long request, long data)
 		clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 #endif
 
-	if (is_singlestep(request) || is_sysemu_singlestep(request)) {
+	if (is_singleblock(request)) {
+		if (unlikely(!arch_has_block_step()))
+			return -EIO;
+		user_enable_block_step(child);
+	} else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 		if (unlikely(!arch_has_single_step()))
 			return -EIO;
 		user_enable_single_step(child);
@@ -438,6 +448,9 @@ int ptrace_request(struct task_struct *child, long request,
 #ifdef PTRACE_SINGLESTEP
 	case PTRACE_SINGLESTEP:
 #endif
+#ifdef PTRACE_SINGLEBLOCK
+	case PTRACE_SINGLEBLOCK:
+#endif
 #ifdef PTRACE_SYSEMU
 	case PTRACE_SYSEMU:
 	case PTRACE_SYSEMU_SINGLESTEP: