# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1475413084 -7200
# Node ID c2fc5c9301931b7b2739e27a306955b8a6313640
# Parent  e889d6aa6619c312e480f28d416b701bd43cf083
Introduced convenience functions handling page pairs.

diff -r e889d6aa6619 -r c2fc5c930193 stage2/memory.h
--- a/stage2/memory.h	Sun May 15 23:35:50 2016 +0200
+++ b/stage2/memory.h	Sun Oct 02 14:58:04 2016 +0200
@@ -1,14 +1,21 @@
 #ifndef __MEMORY_H__
 #define __MEMORY_H__
 
+/* Kernel mode addresses. */
+
 #define STAGE2_INIT_STACK	0x80004000
 #define STAGE2_EXCEPTION_STACK	0x80008000
 
 #define STAGE2_PAGE_TABLE	0x81400000
 #define STAGE2_PAGE_TABLE_TASK	0x00008000
 
+/* User mode addresses. */
+
 #define STAGE2_TASK_STACK	0x01c00000
 #define STAGE2_TASK_STACK_SIZE	0x00002000
+
+/* Common configuration. */
+
 #define STAGE2_PAGESIZE		(4 * 1024)
 
 #endif /* __MEMORY_H__ */
diff -r e889d6aa6619 -r c2fc5c930193 stage2/paging.c
--- a/stage2/paging.c	Sun May 15 23:35:50 2016 +0200
+++ b/stage2/paging.c	Sun Oct 02 14:58:04 2016 +0200
@@ -18,8 +18,19 @@
  */
 
 #include "paging.h"
+#include "memory.h"
 
 inline u32 user_address(u32 addr)
 {
 	return addr & USER_ADDRESS_MASK;
 }
+
+inline u32 previous_page(u32 addr, u32 pagesize)
+{
+	return addr - pagesize * 2;
+}
+
+inline u32 next_page(u32 addr, u32 pagesize)
+{
+	return addr + pagesize * 2;
+}
diff -r e889d6aa6619 -r c2fc5c930193 stage2/paging.h
--- a/stage2/paging.h	Sun May 15 23:35:50 2016 +0200
+++ b/stage2/paging.h	Sun Oct 02 14:58:04 2016 +0200
@@ -8,6 +8,8 @@
 #include "xburst_types.h"
 
 u32 user_address(u32 addr);
+u32 previous_page(u32 addr, u32 pagesize);
+u32 next_page(u32 addr, u32 pagesize);
 
 #endif /* __ASSEMBLER__ */
 
diff -r e889d6aa6619 -r c2fc5c930193 stage2/tasks.c
--- a/stage2/tasks.c	Sun May 15 23:35:50 2016 +0200
+++ b/stage2/tasks.c	Sun Oct 02 14:58:04 2016 +0200
@@ -68,7 +68,10 @@
 	virtual = STAGE2_TASK_STACK;
 	physical = STAGE2_TASK_STACK - STAGE2_TASK_STACK_SIZE * task;
 
-	init_page_table(STAGE2_PAGE_TABLE, virtual - STAGE2_PAGESIZE * 2, physical - STAGE2_PAGESIZE * 2, STAGE2_PAGESIZE, TLB_WRITE, task);
+	init_page_table(STAGE2_PAGE_TABLE,
+		previous_page(virtual, STAGE2_PAGESIZE),
+		previous_page(physical, STAGE2_PAGESIZE),
+		STAGE2_PAGESIZE, TLB_WRITE, task);
 
 	/*
 	Subtract from the stack pointer to prevent the called function from
@@ -86,18 +89,33 @@
 
 	/* Map the global object table for the task. */
 
-	init_page_table(STAGE2_PAGE_TABLE, user_address((u32) &_got_start), user_address((u32) &_got_copy_start), STAGE2_PAGESIZE, TLB_READ, task);
+	init_page_table(STAGE2_PAGE_TABLE,
+		user_address((u32) &_got_start),
+		user_address((u32) &_got_copy_start),
+		STAGE2_PAGESIZE, TLB_READ, task);
 
-	/* Map all shared pages for the task. */
+	/* Map all shared pages for the task. First, the read-only code region. */
 
-	for (address = (u32) &_payload_start; address < (u32) &_got_start; address += STAGE2_PAGESIZE * 2)
+	for (address = (u32) &_payload_start;
+		address < (u32) &_got_start;
+		address = next_page(address, STAGE2_PAGESIZE))
 	{
-		init_page_table(STAGE2_PAGE_TABLE, user_address(address), user_address(address), STAGE2_PAGESIZE, TLB_READ, task);
+		init_page_table(STAGE2_PAGE_TABLE,
+			user_address(address),
+			user_address(address),
+			STAGE2_PAGESIZE, TLB_READ, task);
 	}
 
-	for (address = (u32) &_got_copy_end + STAGE2_PAGESIZE * 2; address < (u32) &_memory_end; address += STAGE2_PAGESIZE * 2)
+	/* Make the pages after the code writable. */
+
+	for (address = next_page((u32) &_got_copy_end, STAGE2_PAGESIZE);
+		address < (u32) &_memory_end;
+		address = next_page(address, STAGE2_PAGESIZE))
 	{
-		init_page_table(STAGE2_PAGE_TABLE, user_address(address), user_address(address), STAGE2_PAGESIZE, TLB_WRITE, task);
+		init_page_table(STAGE2_PAGE_TABLE,
+			user_address(address),
+			user_address(address),
+			STAGE2_PAGESIZE, TLB_WRITE, task);
 	}
 }