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68 lines
2.4 KiB
Plaintext
68 lines
2.4 KiB
Plaintext
/*
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This file is part of Fennix Kernel.
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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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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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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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*/
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.intel_syntax noprefix
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.code32
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.equ PAGE_TABLE_SIZE, 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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.rept 0x10000 /* 0x4000 bytes will be used in UpdatePageTable */
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.long 0
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.endr
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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, 0b11 /* 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, 0b11 /* 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, 0b10000011 /* 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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