# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1456592211 -3600
# Node ID 9e9d063cdfd163ed9bd887d3695877eab08283aa
# Parent  fe0c2c187dda87955e2bc475872436ea9665a9c4
Added a generic exception handler to handle TLB misses during exceptions.

diff -r fe0c2c187dda -r 9e9d063cdfd1 stage2/entry.S
--- a/stage2/entry.S	Sat Feb 27 17:23:49 2016 +0100
+++ b/stage2/entry.S	Sat Feb 27 17:56:51 2016 +0100
@@ -20,6 +20,7 @@
 .text
 .extern interrupt_handler
 .globl _tlb_entry
+.globl _exc_entry
 .globl _irq_entry
 .globl _end_entries
 .set noreorder
@@ -27,7 +28,6 @@
 /* NOTE: Duplicated from cpu.h. */
 
 #define page_table_start 0x00040000
-#define page_table_task_size 0x00008000
 #define page_table_task_size_log2 15
 
 _tlb_entry:
@@ -94,6 +94,22 @@
 	eret
 	nop
 
+_exc_entry:
+	/* Handle TLB refill exceptions. */
+
+	mfc0 $k0, $13				/* CP0_CAUSE */
+	li $k1, 0x0000007c
+	and $k0, $k0, $k1			/* ExcCode << 2 */
+	srl $k0, $k0, 2				/* ExcCode */
+	addi $k1, $k0, -2			/* ExcCode == 2 */
+	beqz $k1, _tlb_entry
+	addi $k1, $k0, -3			/* ExcCode == 3 */
+	beqz $k1, _tlb_entry
+	nop
+_fail:
+	b _fail
+	nop
+
 _irq_entry:
 	/* Save registers that the assembler wants to trash. */
 
diff -r fe0c2c187dda -r 9e9d063cdfd1 stage2/head2.S
--- a/stage2/head2.S	Sat Feb 27 17:23:49 2016 +0100
+++ b/stage2/head2.S	Sat Feb 27 17:56:51 2016 +0100
@@ -24,6 +24,8 @@
 
 .text
 .extern c_main
+.extern _tlb_entry
+.extern _exc_entry
 .extern _irq_entry
 .extern _end_entries
 .extern _got_start
@@ -63,6 +65,14 @@
 
 	la $t0, _tlb_entry		/* start */
 	li $t1, 0x80000000
+	la $t2, _exc_entry		/* end */
+	jal _copy
+	nop
+
+	/* Copy exception handling instructions. */
+
+	la $t0, _exc_entry		/* start */
+	li $t1, 0x80000180
 	la $t2, _irq_entry		/* end */
 	jal _copy
 	nop