ptrace/x86: simplify the "disable" logic in ptrace_write_dr7()

ptrace_write_dr7() looks unnecessarily overcomplicated.  We can factor
out ptrace_modify_breakpoint() and do not do "continue" twice, just we
need to pass the proper "disabled" argument to
ptrace_modify_breakpoint().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/ptrace.c

@@ -637,9 +637,7 @@ static int ptrace_write_dr7(struct task_struct *tsk, unsigned long data)
 	struct thread_struct *thread = &(tsk->thread);
 	unsigned long old_dr7;
 	int i, orig_ret = 0, rc = 0;
-	int enabled, second_pass = 0;
-	unsigned len, type;
-	struct perf_event *bp;
+	int second_pass = 0;
 
 	data &= ~DR_CONTROL_RESERVED;
 	old_dr7 = ptrace_get_dr7(thread->ptrace_bps);
@@ -649,30 +647,22 @@ restore:
 	 * appropriate changes to each.
 	 */
 	for (i = 0; i < HBP_NUM; i++) {
-		enabled = decode_dr7(data, i, &len, &type);
-		bp = thread->ptrace_bps[i];
-
-		if (!enabled) {
-			if (bp) {
-				/*
-				 * Don't unregister the breakpoints right-away,
-				 * unless all register_user_hw_breakpoint()
-				 * requests have succeeded. This prevents
-				 * any window of opportunity for debug
-				 * register grabbing by other users.
-				 */
-				if (!second_pass)
-					continue;
-
-				rc = ptrace_modify_breakpoint(bp, len, type,
-							      tsk, 1);
-				if (rc)
-					break;
-			}
-			continue;
+		unsigned len, type;
+		bool disabled = !decode_dr7(data, i, &len, &type);
+		struct perf_event *bp = thread->ptrace_bps[i];
+
+		if (disabled) {
+			/*
+			 * Don't unregister the breakpoints right-away, unless
+			 * all register_user_hw_breakpoint() requests have
+			 * succeeded. This prevents any window of opportunity
+			 * for debug register grabbing by other users.
+			 */
+			if (!bp || !second_pass)
+				continue;
 		}
 
-		rc = ptrace_modify_breakpoint(bp, len, type, tsk, 0);
+		rc = ptrace_modify_breakpoint(bp, len, type, tsk, disabled);
 		if (rc)
 			break;
 	}