source/kernel/boot/boot.s

@@ -5,6 +5,7 @@
 .section .bootstrap_stack, "aw", @nobits
 stack_bottom:
 .skip 16384 # 16 KiB
+.globl stack_top
 stack_top:
 
 /*
@@ -75,15 +76,6 @@ _start:
 4:
 	# At this point, paging is fully set up and enabled
 isPaging:
-	/* push the pointer to the Multiboot information structure*/
-	pushl %ebx
-
-	/* push the magic value */
-	pushl %eax
-	call prekernelSetup
-
-	# Unmap the identity mapping as it is now unnecessary  
-	# movl $0, boot_page_directory + 0
 
 	# Reload cr3 to force tlb flush 
 	movl %cr3, %ecx
@@ -98,6 +90,19 @@ isPaging:
 	popf 
 
 	
+	/* push the pointer to the Multiboot information structure*/
+	pushl %ebx
+
+	/* push the magic value */
+	pushl %eax
+	call prekernelSetup
+
+	# Unmap the identity mapping as it is now unnecessary  
+	# movl $0, boot_page_directory + 0
+	
+
+
+
 	call early_main
 
 	cli

source/kernel/kernel.cpp

@@ -36,6 +36,8 @@ extern "C"
 #include "serial.h"
 #include "time.h"
 #include "definitions.h"
+extern "C"  void LoadGlobalDescriptorTable();
+
 
 /*
     Copyright © Nigel Barink 2023
@@ -50,17 +52,18 @@ extern "C" void kernel_main ()
     startSuperVisorTerminal();
 }   
 
-
 extern "C" void early_main()
 {
     init_serial();
     kterm_init();
 
 
+    setup_tss();
     initGDT();
-    //setup_tss();
     initidt();
-    
+    LoadGlobalDescriptorTable();
+    flush_tss();
+    printf("Memory setup complete!\n");
   
     // Enable interrupts
     asm volatile("STI");

source/kernel/memory/TaskStateSegment.h

@@ -34,26 +34,27 @@ struct TaskStateSegment {
 }__attribute__((packed));
 
 
-TaskStateSegment tss0 = {};
+TaskStateSegment tss0 ={};
 
-inline void flush_tss(){
-     asm volatile("mov (5 * 8) |0 , %eax; ltr %ax");
+inline void flush_tss()
+{
+     asm volatile("mov $0x2B, %ax ; ltr %ax");
 }
 
-
 void setup_tss(){
-
-
     // ensure the tss is zero'd
-    //memset((void*)&tss0, 0, sizeof(tss0));
-    tss0.ss0 = (uint32_t) &(GlobalDescriptorTable[KERNEL_DATA_SEGMENT]);
-    uint32_t esp_addr =0 ; 
-    asm volatile ("movl %%esp, %0" : "=a"(esp_addr));
-    tss0.esp0 = esp_addr;
+    memset((void*)&tss0, 0, sizeof(tss0));
+    tss0.ss0 =  (uint32_t) &GlobalDescriptorTable[KERNEL_DATA_SEGMENT];
      
+    extern uint32_t stack_top;
+    tss0.esp0 = (unsigned long)&stack_top;
 
     // Task Segment Descriptor
-    add_descriptor(TASK_STATE_SEGMENT, (unsigned long)&tss0, sizeof(tss0), 0x89, 0x0);
-    flush_tss();
+
+    uint32_t address = (unsigned long) &tss0;
+    uint32_t size = sizeof(tss0);
+    uint32_t limit = (address + size );
+
+    add_descriptor(TASK_STATE_SEGMENT, address, limit- 1, 0xE9, 0x0);
 }
 

source/kernel/memory/gdt/gdtc.cpp

@@ -40,8 +40,7 @@ void initGDT(){
       add_descriptor(USER_DATA_SEGMENT, 0, 0xFFFFFFFF, 0xF2, 0xCF);
 
       // init Gdt Descriptor
-      gdtDescriptor.limit = ((sizeof(SegmentDescriptor ) * 5 ) - 1);
+      gdtDescriptor.limit = ((sizeof(SegmentDescriptor ) * 6 ) - 1);
       gdtDescriptor.base = (unsigned int) (&GlobalDescriptorTable);
 
-      LoadGlobalDescriptorTable();
 }

source/kernel/memory/gdt/gdtc.h

@@ -32,5 +32,4 @@ struct GlobalDescriptorTableDescriptor{
 void add_descriptor(int which , unsigned long base, unsigned long limit, unsigned char access, unsigned char granularity );
 
 
-extern "C" void LoadGlobalDescriptorTable();
 void initGDT();