From c9a036bfbb73c47fa820cd5a869281e122b0c957 Mon Sep 17 00:00:00 2001
From: Nigel <nigelbarink@hotmail.com>
Date: Mon, 13 Feb 2023 22:44:47 +0100
Subject: [PATCH] Ring 3 ready - Fixed issue with setting up the Task Segment
 Register

---
 source/kernel/boot/boot.s               | 23 ++++++++++++--------
 source/kernel/kernel.cpp                | 13 ++++++-----
 source/kernel/memory/TaskStateSegment.h | 29 +++++++++++++------------
 source/kernel/memory/gdt/gdtc.cpp       |  3 +--
 source/kernel/memory/gdt/gdtc.h         |  1 -
 5 files changed, 38 insertions(+), 31 deletions(-)

diff --git a/source/kernel/boot/boot.s b/source/kernel/boot/boot.s
index c5e9902..c5414f9 100644
--- a/source/kernel/boot/boot.s
+++ b/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:
 
 /*
@@ -75,16 +76,7 @@ _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
 	movl %ecx, %cr3
@@ -97,6 +89,19 @@ isPaging:
 	pushl $0 
 	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
 
diff --git a/source/kernel/kernel.cpp b/source/kernel/kernel.cpp
index 2972314..f2d056f 100644
--- a/source/kernel/kernel.cpp
+++ b/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
@@ -50,18 +52,19 @@ 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");
 
@@ -73,7 +76,7 @@ extern "C" void early_main()
     initHeap(); 
 
     printf("Enable Protected mode and jump to kernel main\n");
-
+  
 
     // Set the protected bit of control register 0 
     // this will put the CPU into protected mode
diff --git a/source/kernel/memory/TaskStateSegment.h b/source/kernel/memory/TaskStateSegment.h
index c4860c1..b41a4fb 100644
--- a/source/kernel/memory/TaskStateSegment.h
+++ b/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);
 }
 
diff --git a/source/kernel/memory/gdt/gdtc.cpp b/source/kernel/memory/gdt/gdtc.cpp
index c7f15c9..a73b776 100644
--- a/source/kernel/memory/gdt/gdtc.cpp
+++ b/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();
 }
diff --git a/source/kernel/memory/gdt/gdtc.h b/source/kernel/memory/gdt/gdtc.h
index 17c8ec0..bf914a0 100644
--- a/source/kernel/memory/gdt/gdtc.h
+++ b/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();