X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fthreads%2Floader.S;h=d67af3858f2cbefd592742c1dbab02827f4e00f2;hb=828d300fd2039b686b69244c2bd6f8b87645086d;hp=970d2e213dd03a6e12d60bca4ce77f4173811c3c;hpb=8063d8f3b3a778e9a15eff66dfd1b08652bae523;p=pintos-anon

diff --git a/src/threads/loader.S b/src/threads/loader.S
index 970d2e2..d67af38 100644
--- a/src/threads/loader.S
+++ b/src/threads/loader.S
@@ -1,5 +1,5 @@
-#include "mmu.h"
 #include "loader.h"
+#include "mmu.h"
 	
 ##############################################################################
 # Kernel loader.
@@ -12,6 +12,12 @@
 # first byte of the kernel, where start.S is linked.
 ##############################################################################
 	
+/* Flags in control register 0 */
+#define CR0_PE 0x00000001      /* Protection Enable. */
+#define CR0_EM 0x00000004      /* (Floating-point) Emulation. */
+#define CR0_PG 0x80000000      /* Paging. */
+#define CR0_WP 0x00010000      /* Write-Protect enable in kernel mode. */
+
 .globl start				# Entry point	
 start:	.code16				# This runs in real mode
 	cli				# Disable interrupts
@@ -133,35 +139,35 @@ read_sector:
 	cmpl $KERNEL_LOAD_PAGES*8 + 1, %ebx
 	jnz read_sector
 
-##### Create temporary PDE and PTE, set page directory pointer, and turn
-##### on paging.
+##### Create temporary page directory and page table, set page
+##### directory pointer, and turn on paging.
 ##### FIXME? We could use a single 4 MB page instead of 1024 4 kB pages.
 
-	# Create PDE at 64 kB.
+	# Create page directory at 64 kB.
 	movl $0x10000, %edi		
 	movl %edi, %cr3
 
-	# Fill PDE with zeroes.
+	# Fill page directory with zeroes.
 	subl %eax, %eax
 	movl $0x400, %ecx
 	rep stosl
 
-	# Set PDE entries for 0 and LOADER_PHYS_BASE to point to the
-	# PTE.
+	# Set PDEs for 0 and LOADER_PHYS_BASE to point to the
+	# page table.
 	movl $0x11000 | PG_U | PG_W | PG_P, %eax
 	movl %eax, 0x10000
 	movl %eax, 0x10000 | (LOADER_PHYS_BASE >> 20)
 
-	# Initialize PTE.
+	# Initialize page table.
 	movl $PG_U | PG_W | PG_P, %eax
 	movl $0x400, %ecx
 1:	stosl
 	addl $0x1000, %eax
 	loop 1b
 
-	# Enable paging.
+	# Turn on paging and kernel write-protect.
 	movl %cr0, %eax
-	orl $CR0_PG, %eax
+	orl $CR0_PG | CR0_WP, %eax
 	movl %eax, %cr0
 	jmp 1f
 1:
@@ -175,9 +181,10 @@ read_sector:
 	
 ##### Jump to kernel entry point.
 
-	movl $LOADER_PHYS_BASE + LOADER_BASE, %esp
+	movl $LOADER_PHYS_BASE + 0x20000, %esp
 	movl $LOADER_PHYS_BASE + LOADER_KERN_BASE, %eax
-	jmp *%eax
+	call *%eax
+	jmp panic
 
 ##### GDT