mirror of
https://github.com/Fennix-Project/Kernel.git
synced 2025-05-28 15:34:33 +00:00
62 lines
2.2 KiB
NASM
62 lines
2.2 KiB
NASM
; This file is part of Fennix Kernel.
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;
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; Fennix Kernel is free software: you can redistribute it and/or
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; modify it under the terms of the GNU General Public License as
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; published by the Free Software Foundation, either version 3 of
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; the License, or (at your option) any later version.
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;
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; Fennix Kernel is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
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[bits 32]
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PAGE_TABLE_SIZE equ 0x4
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section .bootstrap.data
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align 0x1000
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global BootPageTable
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BootPageTable:
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times (0x10000) dq 0 ; 0x4000 bytes will be used in UpdatePageTable
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section .bootstrap.text
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global UpdatePageTable
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UpdatePageTable:
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mov edi, (BootPageTable + 0x0000) ; First PML4E
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mov eax, (BootPageTable + 0x1000) ; First PDPTE
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or eax, 11b ; Bitwise OR on rax (PDPTE) with 11b (Present, Write)
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mov dword [edi], eax ; Write 11b to PML4E
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mov edi, (BootPageTable + 0x1000) ; First PDPTE
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mov eax, (BootPageTable + 0x2000) ; First PDE
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or eax, 11b ; Bitwise OR on rax (PDE) with 11b (Present, Write)
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mov ecx, PAGE_TABLE_SIZE ; For loop instruction
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mov ebx, 0x0 ; Value to store in the next 4 bytes
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.FillPageTableLevel3:
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mov dword [edi], eax ; Store modified PDE in PDPTE
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mov dword [edi + 4], ebx ; Store the rbx value in the next 4 bytes
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add eax, 0x1000 ; Increment (page size)
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adc ebx, 0 ; Add 0 to carry flag
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add edi, 8 ; Add 8 to rdi (next PDE)
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loop .FillPageTableLevel3 ; Loop until rcx is 0
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mov edi, (BootPageTable + 0x2000) ; First PDE
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mov eax, 10000011b ; Present, Write, Large Page
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mov ecx, (512 * PAGE_TABLE_SIZE) ; For loop instruction
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mov ebx, 0x0 ; Value to store in the next 4 bytes
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.FillPageTableLevel2:
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mov dword [edi], eax ; Store modified PDE in PDPTE
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mov dword [edi + 4], ebx ; Store the rbx value in the next 4 bytes
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add eax, 1 << 21 ; Increment (page size)
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adc ebx, 0 ; Add 0 (carry flag) to rbx to increment if there was a carry
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add edi, 8 ; Add 8 to rdi (next PDE)
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loop .FillPageTableLevel2 ; Loop until rcx is 0
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ret
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