ARM: Fix kgdb breakpoint for Thumb2

The kgdb code needs to register an undef hook for the Thumb UDF
instruction that will fault in order to be functional on Thumb2
platforms.

Reported-by: Johannes Stezenbach <[e-mail]>
Tested-by: Johannes Stezenbach <[e-mail]>
Fixes: 5cbad0ebf45c ("kgdb: support for ARCH=arm")
Signed-off-by: Russell King (Oracle) <[e-mail]>

arch/arm/kernel/kgdb.c

···
 	return 0;
 }
 
-static struct undef_hook kgdb_brkpt_hook = {
+static struct undef_hook kgdb_brkpt_arm_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_BREAKINST,
-	.cpsr_mask		= MODE_MASK,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
 	.cpsr_val		= SVC_MODE,
 	.fn			= kgdb_brk_fn
 };
 
-static struct undef_hook kgdb_compiled_brkpt_hook = {
+static struct undef_hook kgdb_brkpt_thumb_hook = {
+	.instr_mask		= 0xffff,
+	.instr_val		= KGDB_BREAKINST & 0xffff,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
+	.cpsr_val		= PSR_T_BIT | SVC_MODE,
+	.fn			= kgdb_brk_fn
+};
+
+static struct undef_hook kgdb_compiled_brkpt_arm_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_COMPILED_BREAK,
-	.cpsr_mask		= MODE_MASK,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
 	.cpsr_val		= SVC_MODE,
+	.fn			= kgdb_compiled_brk_fn
+};
+
+static struct undef_hook kgdb_compiled_brkpt_thumb_hook = {
+	.instr_mask		= 0xffff,
+	.instr_val		= KGDB_COMPILED_BREAK & 0xffff,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
+	.cpsr_val		= PSR_T_BIT | SVC_MODE,
 	.fn			= kgdb_compiled_brk_fn
 };
 
···
 	if (ret != 0)
 		return ret;
 
-	register_undef_hook(&kgdb_brkpt_hook);
-	register_undef_hook(&kgdb_compiled_brkpt_hook);
+	register_undef_hook(&kgdb_brkpt_arm_hook);
+	register_undef_hook(&kgdb_brkpt_thumb_hook);
+	register_undef_hook(&kgdb_compiled_brkpt_arm_hook);
+	register_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
 
 	return 0;
 }
···
  */
 void kgdb_arch_exit(void)
 {
-	unregister_undef_hook(&kgdb_brkpt_hook);
-	unregister_undef_hook(&kgdb_compiled_brkpt_hook);
+	unregister_undef_hook(&kgdb_brkpt_arm_hook);
+	unregister_undef_hook(&kgdb_brkpt_thumb_hook);
+	unregister_undef_hook(&kgdb_compiled_brkpt_arm_hook);
+	unregister_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
 	unregister_die_notifier(&kgdb_notifier);
 }