From 1d3ff04f2dd47c71aa0b2d7e7601f0d31b3eab60 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Thu, 26 Sep 2019 22:58:06 +0200
Subject: Added higher half kernel with paging

---
 src/kernel/boot.asm       | 109 ++++++++++++++++++++++++++++++----------------
 src/kernel/graphics/vga.c |   2 +-
 src/kernel/kernel.c       |   7 ++-
 src/kernel/linker.ld      |  47 ++++++++++----------
 4 files changed, 100 insertions(+), 65 deletions(-)

diff --git a/src/kernel/boot.asm b/src/kernel/boot.asm
index 197e13c..ef6bf0e 100644
--- a/src/kernel/boot.asm
+++ b/src/kernel/boot.asm
@@ -1,39 +1,72 @@
-[bits 32]
-global start
-global vbe_init_structure
+global start ; Make start available to linker
+extern kernel_main ; Get main function from kernel.c
+
+; Set Multiboot headers for GRUB
+MODULEALIGN equ  1<<0
+MEMINFO     equ  1<<1
+FLAGS       equ  MODULEALIGN | MEMINFO
+MAGIC       equ  0x1BADB002
+CHECKSUM    equ  -(MAGIC + FLAGS)
+
+; Set virtual base address of kernel space
+KERNEL_VIRTUAL_BASE equ 0xC0000000 ; 3GB
+KERNEL_PAGE_NUMBER equ (KERNEL_VIRTUAL_BASE >> 22) ; Page directory index of kernel's 4MB PTE.
+
+section .data
+align 0x1000
+BootPageDirectory:
+    ; Create page directory entry to identity-map the first 4MB of the 32-bit physical address space.
+    dd 0x00000083
+    times (KERNEL_PAGE_NUMBER - 1) dd 0
+    ; Create 4MB page directory entry to contain the kernel
+    dd 0x00000083
+    times (1024 - KERNEL_PAGE_NUMBER - 1) dd 0
+
+section .text
+align 4
+MultiBootHeader:
+    dd MAGIC
+    dd FLAGS
+    dd CHECKSUM
+
+; Reserve 16k for initial kernel stack space
+STACKSIZE equ 0x4000
+
+; Set up entry point for linker
+loader equ (start - 0xC0000000)
+global loader
+
 start:
-    mov esp, _sys_stack ; Points stack to stack area
-    jmp stublet
-
-; Align with 4 Bytes
-ALIGN 4
-mboot:
-    ; Multiboot macros
-    MULTIBOOT_PAGE_ALIGN equ 1<<0
-    MULTIBOOT_MEMORY_INFO equ 1<<1
-    MULTIBOOT_AOUT_KLUDGE equ 1<<16
-    MULTIBOOT_HEADER_MAGIC equ 0x1BADB002
-    MULTIBOOT_HEADER_FLAGS equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
-    MULTIBOOT_CHECKSUM	equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
-    EXTERN code, bss, end
-
-    ; GRUB Multiboot header
-    dd MULTIBOOT_HEADER_MAGIC
-    dd MULTIBOOT_HEADER_FLAGS
-    dd MULTIBOOT_CHECKSUM
-
-    ; AOUT kludge
-    dd mboot
-    dd code
-    dd bss
-    dd end
-    dd start
-
-; Endless loop
-stublet:
-    extern kernel_main
+    ; Using physical addresses for now
+    mov ecx, (BootPageDirectory - KERNEL_VIRTUAL_BASE)
+    mov cr3, ecx ; Load Page Directory Base Register
+
+    mov ecx, cr4
+    or ecx, 0x00000010 ; Set PSE in CR4 to enable 4MB pages
+    mov cr4, ecx
+
+    mov ecx, cr0
+    or ecx, 0x80000000 ; Enable paging
+    mov cr0, ecx
+
+    ; Long jump to StartInHigherHalf
+    lea ecx, [StartInHigherHalf]
+    jmp ecx
+
+StartInHigherHalf:
+    mov dword [BootPageDirectory], 0
+    invlpg [0]
+
+    mov esp, stack+STACKSIZE           ; Set up the stack
+    push eax                           ; Pass Multiboot magic number
+
+    ; Pass Multiboot info structure
+    push ebx
+    add ebx, KERNEL_VIRTUAL_BASE
+    push ebx
+
     call kernel_main
-    jmp $
+    hlt
 
 %include "src/kernel/gdt/gdt.asm"
 
@@ -45,7 +78,7 @@ stublet:
 
 %include "src/kernel/interact.asm"
 
-; Store the stack
-SECTION .bss
-    resb 8192 ; Reserve 8KiB
-_sys_stack:
\ No newline at end of file
+section .bss
+align 32
+stack:
+    resb STACKSIZE      ; reserve 16k stack on a uint64_t boundary
diff --git a/src/kernel/graphics/vga.c b/src/kernel/graphics/vga.c
index fa1f330..36f5e04 100644
--- a/src/kernel/graphics/vga.c
+++ b/src/kernel/graphics/vga.c
@@ -74,7 +74,7 @@ void terminal_initialize(void) {
     terminal_row = 0;
     terminal_column = 0;
     terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
-    terminal_buffer = (uint16_t *) 0xB8000;
+    terminal_buffer = (uint16_t *) 0xC00B8000;
     terminal_clear();
 }
 
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index dd68536..383966d 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -6,11 +6,11 @@
 #include "timer/timer.h"
 
 void init() {
-    asm volatile ("sti");
     gdt_install();
     idt_install();
     isrs_install();
     irq_install();
+    asm volatile ("sti");
     timer_install();
     terminal_initialize();
     keyboard_install();
@@ -19,9 +19,12 @@ void init() {
 
 void kernel_main(void) {
     // vbe_set_mode(0x11B);
-    set_optimal_resolution();
+    // set_optimal_resolution();
+    init();
+    keyboard_install();
 
     terminal_write_string("Melvix loaded successfully!\n");
 
     // __asm__  ("div %0" :: "r"(0)); // Exception testing x/0
+    for (;;);
 }
\ No newline at end of file
diff --git a/src/kernel/linker.ld b/src/kernel/linker.ld
index 6461b2b..3e209fc 100644
--- a/src/kernel/linker.ld
+++ b/src/kernel/linker.ld
@@ -1,25 +1,24 @@
-OUTPUT_FORMAT("binary")
 ENTRY(start)
-phys = 0x00100000;
-SECTIONS
-{
-  .text phys : AT(phys) {
-    code = .;
-    *(.text)
-    *(.rodata*)
-    . = ALIGN(4096);
-  }
-  .data : AT(phys + (data - code))
-  {
-    data = .;
-    *(.data)
-    . = ALIGN(4096);
-  }
-  .bss : AT(phys + (bss - code))
-  {
-    bss = .;
-    *(.bss)
-    . = ALIGN(4096);
-  }
-  end = .;
-}
+OUTPUT_FORMAT(elf32-i386)
+
+SECTIONS {
+   . = 0xC0100000;
+ 
+   .text : AT(ADDR(.text) - 0xC0000000) {
+       *(.text)
+       *(.rodata*)
+   }
+ 
+   .data ALIGN (0x1000) : AT(ADDR(.data) - 0xC0000000) {
+       *(.data)
+   }
+ 
+   .bss : AT(ADDR(.bss) - 0xC0000000) {
+       _sbss = .;
+       *(COMMON)
+       *(.bss)
+       _ebss = .;
+   }
+
+   end = .;
+}
\ No newline at end of file
-- 
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