# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1448064652 -3600
# Node ID 4aa74d63b1d097edcb915b8ba2057cb60f26c2c0
# Parent  ac3734da88fd65005231b3f9af00c6b94dc332e3
Added a separate "kernel" stack.

diff -r ac3734da88fd -r 4aa74d63b1d0 boot_usb
--- a/boot_usb	Fri Jul 03 21:23:35 2015 +0200
+++ b/boot_usb	Sat Nov 21 01:10:52 2015 +0100
@@ -7,4 +7,5 @@
 xbboot flush_cache
 xbboot set_addr 0x80010000
 xbboot bulk_write stage2/stage2.bin
+xbboot flush_cache
 xbboot start2 0x80010000
diff -r ac3734da88fd -r 4aa74d63b1d0 stage2/handlers.S
--- a/stage2/handlers.S	Fri Jul 03 21:23:35 2015 +0200
+++ b/stage2/handlers.S	Sat Nov 21 01:10:52 2015 +0100
@@ -21,20 +21,24 @@
 .text
 .extern irq_handle
 .extern irq_counter
+.globl _exc_stack
 .globl real_exception_handler
 .set noreorder
 .set noat
 
-#define C0_STATUS	$12
-#define C0_CAUSE	$13
-#define C0_EPC		$14
-#define C0_CONFIG	$16
-#define C0_ERROREPC	$30
-#define S_CauseExcCode	2
-#define M_CauseExcCode	(0x1f << S_CauseExcCode)
+#define C0_STATUS   $12
+#define C0_CAUSE    $13
+#define C0_EPC      $14
+#define C0_CONFIG   $16
+#define C0_ERROREPC $30
+#define S_CauseExcCode  2
+#define M_CauseExcCode  (0x1f << S_CauseExcCode)
+
+_exc_stack:
+    .word 0
 
 real_exception_handler:
-    addiu   $sp, -0x88		/* multiple of 8 */
+    addiu   $sp, -0x88      /* multiple of 8 */
     sw      $ra,    0($sp)
     sw      $fp,    4($sp)
     sw      $gp,    8($sp)
@@ -97,6 +101,14 @@
     nop
     
 _int:
+    /* Initialise the kernel stack. */
+
+    la      $k1, _exc_stack
+    lw      $k0, 0($k1)
+    sw      $sp, 0($k0)
+    addiu   $k0, -4
+    move    $sp, $k0
+
     /* Initialise the globals pointer. */
 
     lui $gp, %hi(_GLOBAL_OFFSET_TABLE_)
@@ -113,6 +125,12 @@
 
     jal     irq_handle
     nop
+
+    /* Restore the user stack. */
+
+    addiu   $sp, 4
+    lw      $sp, 0($sp)
+
     j       _exception_return
     nop
     
@@ -176,7 +194,7 @@
     sll     $zero, 1
     sll     $zero, 1
     sll     $zero, 1
-    addiu   $sp, 0x88		/* multiple of 8 */
+    addiu   $sp, 0x88       /* multiple of 8 */
     eret
     nop
 
diff -r ac3734da88fd -r 4aa74d63b1d0 stage2/head2.S
--- a/stage2/head2.S	Fri Jul 03 21:23:35 2015 +0200
+++ b/stage2/head2.S	Sat Nov 21 01:10:52 2015 +0100
@@ -28,13 +28,17 @@
 .extern _exc_entry
 .extern _irq_entry
 .extern _end_entries
+.extern _exc_stack
 .globl _start
 .set noreorder
 
 _start:
-	/* Initialise the stack. */
+	/* Initialise the stacks. */
 
 	la $sp, 0x80080000
+	la $k0, 0x80090000
+	la $k1, _exc_stack
+	sw $k0, 0($k1)
 
 	/* Initialise the globals pointer. */