# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1462881485 -7200
# Node ID 593fb3352d9b0dee806eaf09594cb2554b405e2c
# Parent  739db6eca61a4a7f7462318fae8b74c10dfb83ac
Mapped task stacks from 0x01c0000 downwards, moved kernel stacks to 0x8000 and
below, made the code region read-only. Added definitions for TLB flags.

diff -r 739db6eca61a -r 593fb3352d9b include/mips.h
--- a/include/mips.h	Thu May 05 12:19:24 2016 +0200
+++ b/include/mips.h	Tue May 10 13:58:05 2016 +0200
@@ -25,4 +25,14 @@
 
 #define CAUSE_IV	0x00800000
 
+#define TLB_CACHED	0x00000018
+#define TLB_DIRTY	0x00000004
+#define TLB_VALID	0x00000002
+#define TLB_GLOBAL	0x00000001
+
+#define TLB_READ	(TLB_CACHED | TLB_VALID)
+#define TLB_WRITE	(TLB_CACHED | TLB_DIRTY | TLB_VALID)
+#define TLB_ALL_READ	(TLB_CACHED | TLB_VALID | TLB_GLOBAL)
+#define TLB_ALL_WRITE	(TLB_CACHED | TLB_DIRTY | TLB_VALID | TLB_GLOBAL)
+
 #endif /* __MIPS_H__ */
diff -r 739db6eca61a -r 593fb3352d9b stage2/entry.S
--- a/stage2/entry.S	Thu May 05 12:19:24 2016 +0200
+++ b/stage2/entry.S	Tue May 10 13:58:05 2016 +0200
@@ -136,9 +136,9 @@
 	lw $k1, 0($k1)				/* &stack_pointers[current_task] */
 	sw $sp, 0($k1)
 
-	/* Switch to the kernel stack. */
+	/* Switch to the kernel exception stack. */
 
-	li $sp, 0x80070000
+	li $sp, 0x80008000
 
 	/* Invoke the rest of the interrupt handling process. */
 
diff -r 739db6eca61a -r 593fb3352d9b stage2/head2.S
--- a/stage2/head2.S	Thu May 05 12:19:24 2016 +0200
+++ b/stage2/head2.S	Tue May 10 13:58:05 2016 +0200
@@ -51,9 +51,9 @@
 	.word 0
 
 real_start:     
-	/* Initialise the stack. */
+	/* Initialise the default kernel stack. */
 
-	la $sp, 0x80080000
+	la $sp, 0x80004000
 
 	/* Initialise the globals pointer. */
 
diff -r 739db6eca61a -r 593fb3352d9b stage2/tasks.c
--- a/stage2/tasks.c	Thu May 05 12:19:24 2016 +0200
+++ b/stage2/tasks.c	Tue May 10 13:58:05 2016 +0200
@@ -19,6 +19,7 @@
 
 #include "cpu.h"
 #include "cpu_op.h"
+#include "mips.h"
 #include "paging.h"
 #include "tasks.h"
 
@@ -33,7 +34,7 @@
 
 /* Address locations and paging configuration. */
 
-const u32 stack_start = 0x00080000;
+const u32 stack_start = 0x01c00000;
 const u32 stack_size = 0x00002000;
 const u32 pagesize = 4 * 1024;
 
@@ -65,13 +66,14 @@
 
 	/*
 	Each task employs a stack at a multiple of the given start address in
-	physical memory, but at the same address in virtual memory.
+	physical memory, but at the same address in virtual memory. Task zero
+	is never started.
 	*/
 
 	virtual = stack_start;
 	physical = stack_start - stack_size * task;
 
-	init_page_table(page_table_start, virtual - pagesize * 2, physical - pagesize * 2, pagesize, 0x1e, task);
+	init_page_table(page_table_start, virtual - pagesize * 2, physical - pagesize * 2, pagesize, TLB_WRITE, task);
 
 	/*
 	Subtract from the stack pointer to prevent the called function from
@@ -89,18 +91,18 @@
 
 	/* Map the global object table for the task. */
 
-	init_page_table(page_table_start, user_address((u32) &_got_start), user_address((u32) &_got_copy_start), pagesize, 0x1e, task);
+	init_page_table(page_table_start, user_address((u32) &_got_start), user_address((u32) &_got_copy_start), pagesize, TLB_READ, task);
 
 	/* Map all shared pages for the task. */
 
 	for (address = (u32) &_payload_start; address < (u32) &_got_start; address += pagesize * 2)
 	{
-		init_page_table(page_table_start, user_address(address), user_address(address), pagesize, 0x1e, task);
+		init_page_table(page_table_start, user_address(address), user_address(address), pagesize, TLB_READ, task);
 	}
 
 	for (address = (u32) &_got_copy_end + pagesize * 2; address < (u32) &_memory_end; address += pagesize * 2)
 	{
-		init_page_table(page_table_start, user_address(address), user_address(address), pagesize, 0x1e, task);
+		init_page_table(page_table_start, user_address(address), user_address(address), pagesize, TLB_WRITE, task);
 	}
 }