add mips32-minimal exception hanlding

am/arch/mips32-minimal/img/boot/Makefile

@@ -1,2 +1,4 @@
 start.o: start.S
-	mips-linux-gnu-gcc -EL -march=mips32 -fno-pic -MMD -mno-abicalls -fno-delayed-branch -c start.S -o start.o
+	mips-linux-gnu-gcc -I$(AM_HOME)/am/arch/mips32-minimal/include -EL -march=mips32 -fno-pic -MMD -mno-abicalls -fno-delayed-branch -c start.S -o start.o
+
+-include start.d

am/arch/mips32-minimal/img/boot/start.S

@@ -1,6 +1,14 @@
+#include <npc.h>
+
 .globl _start
-.type _start, @function
-  
+.type _start, function
+.globl _ex_entry
+.type _ex_entry, function
+ 
 _start:
   la $sp, _stack_pointer
   j _trm_init
+
+.org EX_ENTRY
+_ex_entry:
+  j _trap

am/arch/mips32-minimal/include/npc.h

@@ -1,8 +1,7 @@
 #ifndef __NPC_H__
 #define __NPC_H__
 
-#include <arch.h>
-
+#define EX_ENTRY 0x20
 #define SERIAL_PORT ((volatile char *)0x40001000)
 #define Rx 0x0
 #define Tx 0x04
@@ -11,6 +10,10 @@
 #define GPIO_TRAP ((volatile char *)0x40000000)
 #define HZ 50000000
 
+#ifndef __ASSEMBLER__
+
+#include <arch.h>
+
 struct TrapFrame{
   u32 at,
   v0,v1,
@@ -23,3 +26,5 @@ struct TrapFrame{
 void serial_init();
 
 #endif
+
+#endif

am/arch/mips32-minimal/src/trap.S

@@ -0,0 +1,4 @@
+.globl _trap
+.type _trap function
+_trap:
+  j _trap