From 21f33a176849f0df527b5fe8d9274726c5de9971 Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Sat, 3 Oct 2009 16:48:28 +0000
Subject: [PATCH] - 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.
Upgrade to CVS Suite for more features and support:
http://march-hare.com/cvsnt/


git-svn-id: http://moon:8086/svn/vhdl/trunk@494 cc03376c-175c-47c8-b038-4cd826a8556b
---
 lib/CPUs/MIPS/bsp/examples/kernel.S  | 26 +++++++++++++----------
 lib/CPUs/MIPS/bsp/examples/link.ld   |  6 ++++--
 lib/CPUs/MIPS/bsp/examples/startup.S | 31 ++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/lib/CPUs/MIPS/bsp/examples/kernel.S b/lib/CPUs/MIPS/bsp/examples/kernel.S
index bcffffb..aa0648b 100644
--- a/lib/CPUs/MIPS/bsp/examples/kernel.S
+++ b/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)	
diff --git a/lib/CPUs/MIPS/bsp/examples/link.ld b/lib/CPUs/MIPS/bsp/examples/link.ld
index 2eb2b86..44b93b3 100644
--- a/lib/CPUs/MIPS/bsp/examples/link.ld
+++ b/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           :
   {
diff --git a/lib/CPUs/MIPS/bsp/examples/startup.S b/lib/CPUs/MIPS/bsp/examples/startup.S
index d595475..605631a 100644
--- a/lib/CPUs/MIPS/bsp/examples/startup.S
+++ b/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