[PATCH] ppc64: allow xmon=off

If both CONFIG_XMON and CONFIG_XMON_DEFAULT is enabled in the .config,
there is no way to disable xmon again. setup_system calls first xmon_init,
later parse_early_param. So a new 'xmon=off' cmdline option will do the right
thing.
Signed-off-by: Olaf Hering <olh@suse.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/ppc64/kernel/setup.c

@@ -627,7 +627,7 @@ void __init setup_system(void)
 	 * Initialize xmon
 	 */
 #ifdef CONFIG_XMON_DEFAULT
-	xmon_init();
+	xmon_init(1);
 #endif
 	/*
 	 * Register early console
@@ -1343,11 +1343,13 @@ static int __init early_xmon(char *p)
 	/* ensure xmon is enabled */
 	if (p) {
 		if (strncmp(p, "on", 2) == 0)
-			xmon_init();
+			xmon_init(1);
+		if (strncmp(p, "off", 3) == 0)
+			xmon_init(0);
 		if (strncmp(p, "early", 5) != 0)
 			return 0;
 	}
-	xmon_init();
+	xmon_init(1);
 	debugger(NULL);
 
 	return 0;

arch/ppc64/xmon/start.c

@@ -27,7 +27,7 @@ static void sysrq_handle_xmon(int key, struct pt_regs *pt_regs,
 			      struct tty_struct *tty) 
 {
 	/* ensure xmon is enabled */
-	xmon_init();
+	xmon_init(1);
 	debugger(pt_regs);
 }
 

arch/ppc64/xmon/xmon.c

@@ -2496,8 +2496,9 @@ static void dump_stab(void)
 	}
 }
 
-void xmon_init(void)
+void xmon_init(int enable)
 {
+	if (enable) {
 		__debugger = xmon;
 		__debugger_ipi = xmon_ipi;
 		__debugger_bpt = xmon_bpt;
@@ -2505,6 +2506,15 @@ void xmon_init(void)
 		__debugger_iabr_match = xmon_iabr_match;
 		__debugger_dabr_match = xmon_dabr_match;
 		__debugger_fault_handler = xmon_fault_handler;
+	} else {
+		__debugger = NULL;
+		__debugger_ipi = NULL;
+		__debugger_bpt = NULL;
+		__debugger_sstep = NULL;
+		__debugger_iabr_match = NULL;
+		__debugger_dabr_match = NULL;
+		__debugger_fault_handler = NULL;
+	}
 }
 
 void dump_segments(void)

include/asm-ppc64/system.h

@@ -88,7 +88,7 @@ DEBUGGER_BOILERPLATE(debugger_dabr_match)
 DEBUGGER_BOILERPLATE(debugger_fault_handler)
 
 #ifdef CONFIG_XMON
-extern void xmon_init(void);
+extern void xmon_init(int enable);
 #endif
 
 #else