- added exception vector table.

S/W can write exception handler entry to this table.
  Exception handler can now reside anywhere in memory.

Committed on the Free edition of March Hare Software CVSNT Server.
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git-svn-id: http://moon:8086/svn/vhdl/trunk@494 cc03376c-175c-47c8-b038-4cd826a8556b

lib/CPUs/MIPS/bsp/examples/kernel.S

@@ -1,9 +1,13 @@
 #include <regdef.h>
 #include <xcpt_asm.h>
 
-		.section .ktext,"ax"
+		.section .exc_vect
+_xcpt_vector_tbl:
+		.fill	16, 4, 0		
+			
+		.text
 
-LEAF(xcptlow_handler)
+LEAF(_xcpt_handler)
 		.set noreorder
 		.set noat
 		/* Note: exceptions do not save and restore registers k0 and k1.
@@ -91,21 +95,21 @@ LEAF(xcptlow_handler)
 		/* and call the C exception handler */
 		move a0, sp	# arg1 = &xcp
 		subu sp, 16	# (arg save area)
-		j _xcptcall
+		j _xcpt_call
 		move ra, zero	# fake return address
 		
-		/* This strange call to _xcptcall with zero return address is to
+		/* This strange call to _xcpt_call with zero return address is to
 		* help exception-aware debuggers to trace back over the exception event.
 		* We are basically interposing a bogus stackframe (with a zero return
 		* address) between the C exception handler and the actual machine
 		* exception.
 		*/
-xcptrest:
+$xcptrest:
 		.set noat
 		add AT, sp, 16
 		
 		/* at points to exception frame */
-xcptrestother:
+$xcptrestother:
 		/* restore all state */
 		/* restore most general registers */
 		lw t0, XCP_T0(AT)
@@ -160,10 +164,10 @@ xcptrestother:
 
 		.set reorder
 		.set at
-END(xcptlow_handler)
+END(_xcpt_handler)
 		
-
-LEAF(_xcptcall)
+		
+LEAF(_xcpt_call)
 		/* on entry: a0 == &xcp */
 		subu sp, 24
 		sw ra, 16(sp)
@@ -173,8 +177,8 @@ LEAF(_xcptcall)
 		nop
 		lw ra, 16(sp)
 		addu sp, 24
-		beqz ra, xcptrest
+		beqz ra, $xcptrest
 		nop
 		j ra
 		nop
-END(_xcptcall)	
+END(_xcpt_call)	

lib/CPUs/MIPS/bsp/examples/link.ld

@@ -31,9 +31,11 @@ SECTIONS
      *(.start)
    }
    /* Kernel text with low-level exception handler */
-   .ktext __executable_start + 0x180 :
+   .exc_vector __executable_start + 0x080 :
    {
-     *(.ktext)
+      _exc_vect_start = .;
+     *(.exc_vect)
+      _exc_vect_end = .;
    }
   .init           :
   {

lib/CPUs/MIPS/bsp/examples/startup.S

@@ -9,11 +9,19 @@ argv:		.word		argv0
 		.section .start, "ax"
 		.extern _init
 		.extern dbg_init
+		.extern _exc_vect_start
+		.extern _xcpt_handler
 		.align	2
 		.globl _start
 _start:
 		.set	noreorder
+		j	init
+		nop		
+		.set	reorder
 
+		.text
+		.set	noreorder
+init:
 		# Set stack pointer 
 		la $sp, stack_ptr
 		# Set global pointer 
@@ -27,6 +35,17 @@ $zeroise:
 		bne $8, $9, $zeroise
 		addiu	$8, 4
 
+		# Install exception vector jump code
+		la $t1, _exc_vect_copy_start
+		la $t2, _exc_vect_copy_end
+		la $t0, _exc_vect_start
+
+$install:	lw	$v0, 0($t1)
+		addiu	$t1, 4
+		sw	$v0, 0($t0)
+		bne	$t1, $t2, $install
+		addiu	$t0, 4
+		
 		# Call _init
 		la $k0, _init
 		jalr $k0
@@ -41,6 +60,12 @@ $zeroise:
 		li	$a0, 1
 		la	$a1, argv
 
+		# Set user-mode
+		mfc0	$a0, $12
+		li	$a1, 3
+		or	$a0, $a1
+		mtc0	$a0, $12
+		
 		# Call main
 		la $k0, main
 		jalr $k0
@@ -52,5 +77,11 @@ _terminate:
 		la $t0, exit
 		jalr $t0
 		move $a0, $v0
+
+_exc_vect_copy_start:
+		la $k0, _xcpt_handler
+		jr $k0
+		nop
+_exc_vect_copy_end:
 		
 		.set	reorder