Try to fix GDT; unsuccessful
This commit just existed because of a misunderstanding leading to the belief that the GDT was finally working; it wasn't though.
This commit is contained in:
parent
4a835a0ece
commit
83eb29d55c
GPG Key ID:
1358818BAA38B104
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@ -8,13 +8,14 @@ UPPER_STACK_POINTER equ 0x100000
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LOWER_STACK_POINTER equ (UPPER_STACK_POINTER - STACK_SIZE)
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bits 16
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org 0xa000
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org 0x0000
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entry:
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mov ebx, LOWER_STACK_POINTER
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mov ss, ebx
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mov esp, STACK_SIZE
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mov ebp, STACK_SIZE
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push dx
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cli
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.check_a20:
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push ebp
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@ -25,32 +26,20 @@ entry:
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cmp eax, 1
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je .a20_is_enabled
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cli
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hlt
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.a20_is_enabled:
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; jmp .flat_gdt_loaded
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; Reset Display
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mov ah, 0x00
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mov al, 0x03
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int 0x10
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; mov ah, 0x05
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; mov al, 0
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; int 0x10
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mov ah, 0x0b
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mov bh, 0x00
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mov bl, 0
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int 0x10
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push ebp
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mov ebp, esp
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call setup_drivers
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mov esp, ebp
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pop ebp
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mov edi, ebp
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mov esi, esp
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push ebp
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@ -63,13 +52,11 @@ entry:
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mov ebp, edi
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mov esp, esi
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mov ebx, some_text
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push ebp
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mov ebp, esp
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push dword ebx
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call dword write_text
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mov esp, ebp
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pop ebp
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; push ebp
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; mov ebp, esp
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; call setup_drivers
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; mov esp, ebp
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; pop ebp
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cli
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hlt
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@ -5,7 +5,7 @@ GDT_ENTRY_SIZE equ 8
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db "gdt_set_segment"
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; [Furthest from EBP]
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; 3. Bool (Lowest Address) Task State Segment (1) or Code/Data (0)
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; 3. Bool (Lowest Address) Task State Segment (0) or Code/Data (1)
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; Bool (Second-Lowest) Executable (1) or Not (0)
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; Bool (Second-Highest) Stack (1) or Heap (0) Page
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; Bool (Highest Address) Readable AND Writeable (1) or only what's necessary (0)
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@ -19,7 +19,6 @@ gdt_set_segment:
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sub esp, 64
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mov esi, esp
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mov [esi + (64 - 4)], eax
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mov [esi + (64 - 8)], ebx
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mov [esi + (64 - 12)], ecx
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mov [esi + (64 - 16)], edx
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@ -45,12 +44,13 @@ gdt_set_segment:
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; [Lowest]
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xor al, al
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cmp [ebp - 16], byte 0
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or al, (1 << 7) ; Present-Bit
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cmp [ebp - 15], byte 0
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je .after_task_segment_bit_setter
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or al, (1 << 4)
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.after_task_segment_bit_setter:
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cmp [ebp - 15], byte 0
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cmp [ebp - 14], byte 0
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je .after_executable_bit_setter
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or al, (1 << 3)
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.after_executable_bit_setter:
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@ -69,7 +69,7 @@ gdt_set_segment:
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; [Highest]
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; 3. Address and Size Granularity (Bytes: 0, Pages: 1)
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; 2. 16-Bit or 32-Bit selector (0: 16-Bit, 1: 32-Bit)
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; 1. Long Mode / 64-Bit (
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; 1. Long Mode / 64-Bit
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; 0. Reserved, should be 0
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; [Lowest]
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mov ah, (0b00001100 << 4)
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@ -79,14 +79,14 @@ gdt_set_segment:
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mov ecx, [ebp - 12]
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shr ecx, 16
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and ecx, 0b00001111
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or al, cl
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or ah, cl
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; Store the Access Byte and the Flags into the entry.
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mov ebx, [esi]
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mov [ebx + 5], al ; Access Byte
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mov [ebx + 6], ah ; Flags + Limit
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mov eax, [ebp - 8]
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mov eax, [ebp - 8] ; Base Address
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mov [ebx + 2], ax
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shr eax, 16
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mov [ebx + 3], al
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@ -136,12 +136,12 @@ load_flat_gdt:
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push ebp
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mov ebp, esp
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push dword 1
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push dword 0xa00
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push dword 0x0a00
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push dword 0xfffff
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push byte 1
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push byte 0
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push byte 1
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push byte 0
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push byte 1
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call gdt_set_segment
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mov esp, ebp
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pop ebp
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@ -155,7 +155,7 @@ load_flat_gdt:
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push byte 1
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push byte 1
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push byte 0
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push byte 0
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push byte 1
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call gdt_set_segment
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mov esp, ebp
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pop ebp
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@ -169,34 +169,29 @@ load_flat_gdt:
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push byte 1
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push byte 0
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push byte 1
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push byte 0
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push byte 1
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call gdt_set_segment
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mov esp, ebp
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pop ebp
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; Write the GDT Descriptor
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cli
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mov [esi + 10], dword GDT_MEMORY_AREA
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mov [esi + 8], word 31
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mov eax, esi
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add ebx, 8
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lgdt [ebx]
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sti
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lgdt [.gdtr]
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mov ax, (3 << 4)
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mov ax, (3 << 3)
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ax, (2 << 4)
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mov ax, (2 << 3)
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mov ss, ax
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jmp dword (1 << 3):.epilog
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.epilog:
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mov eax, cr0
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or eax, 1
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mov cr0, eax
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jmp dword (1 << 4):.epilog
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.epilog:
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mov ebx, [esi + (64 - 8)]
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mov ecx, [esi + (64 - 12)]
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mov edx, [esi + (64 - 16)]
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@ -204,3 +199,10 @@ load_flat_gdt:
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mov esi, [esi + 20]
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jmp esi
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align 16
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.gdtr:
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.gdtr.length:
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dw 31
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.gdtr.address:
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dd GDT_MEMORY_AREA
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