Fix: lab3 on-board problems

kernel/exception_table.S

@@ -2,7 +2,7 @@
 
 // save general registers to stack
 .macro save_all
-	sub sp, sp, 36 * 8
+	sub sp, sp, 34 * 8
 	stp x0, x1,   [sp, 16 * 0]
 	stp x2, x3,   [sp, 16 * 1]
 	stp x4, x5,   [sp, 16 * 2]
@@ -18,17 +18,22 @@
 	stp x24, x25, [sp, 16 * 12]
 	stp x26, x27, [sp, 16 * 13]
 	stp x28, x29, [sp, 16 * 14]
-	stp x30, lr,  [sp, 16 * 15]
 
   mrs x0, spsr_el1
   mrs x1, elr_el1
   mrs x2, esr_el1
-  stp x0, x1,   [sp, 16 * 16]
-  str x2,       [sp, 16 * 17]
+  stp x0, x1,   [sp, 16 * 15]
+  stp x2, lr,   [sp, 16 * 16]
 .endm
 
 // load general registers from stack
 .macro load_all
+  ldp x0, x1,   [sp, 16 * 15]
+  ldp x2, lr,   [sp, 16 * 16]
+  msr spsr_el1, x0
+  msr elr_el1,  x1
+  msr esr_el1,  x2
+
 	ldp x0, x1,   [sp, 16 * 0]
 	ldp x2, x3,   [sp, 16 * 1]
 	ldp x4, x5,   [sp, 16 * 2]
@@ -44,14 +49,8 @@
 	ldp x24, x25, [sp, 16 * 12]
 	ldp x26, x27, [sp, 16 * 13]
 	ldp x28, x29, [sp, 16 * 14]
-	ldp x30, lr,  [sp, 16 * 15]
 
-  ldp x0, x1,   [sp, 16 * 16]
-  ldr x2,       [sp, 16 * 17]
-  msr spsr_el1, x0
-  msr elr_el1,  x1
-  msr esr_el1,  x2
-	add sp, sp, 36 * 8
+	add sp, sp, 34 * 8
 .endm
 
 _null_handler: