3 files changed, 29 insertions, 1 deletions
diff --git a/tb/sim/modeswitch.S b/tb/sim/modeswitch.S
new file mode 100644
index 0000000..c04f8a3
--- /dev/null
+++ b/tb/sim/modeswitch.S
@@ -0,0 +1,21 @@
+.global reset
+reset:
+	mrs  r0, cpsr
+	udf
+	mrs  r2, cpsr
+	ldr  r3, =#0x16f
+	bic  r3, r2, r3
+	msr  cpsr_fxc, r3
+	mrs  r4, cpsr
+	cmp  r0, r0
+	mrs  r5, spsr
+	nop
+	msr  cpsr_fxc, r0 
+	msr  spsr_fxc, r0
+	mov  pc, lr
+
+.global undefined
+undefined:
+	mrs  r1, spsr
+	mrs  r13, cpsr
+	movs pc, lr
diff --git a/tb/sim/modeswitch.py b/tb/sim/modeswitch.py
new file mode 100644
index 0000000..6919f2e
--- /dev/null
+++ b/tb/sim/modeswitch.py
@@ -0,0 +1,3 @@
+def final():
+    #TODO
+    assert_reg(r0, -1)
diff --git a/tb/sim/start.S b/tb/sim/start.S
index 54a8d1f..7639513 100644
--- a/tb/sim/start.S
+++ b/tb/sim/start.S
@@ -4,7 +4,7 @@ __reset:
 	b _start
 
 __undefined:
-	b __undefined
+	b undefined
 
 __swi:
 	b __data_abort
@@ -28,3 +28,7 @@ _start:
 	ldr sp, =_stack_end
 	bl  reset
 	b   .
+
+.weak undefined
+undefined:
+	b undefined