81d0b19726
git-svn-id: http://svn.lfbs.rwth-aachen.de/svn/scc/trunk/MetalSVM@347 315a16e6-25f9-4109-90ae-ca3045a26c18
105 lines
2.3 KiB
NASM
105 lines
2.3 KiB
NASM
;
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; Copyright 2010 Stefan Lankes, Chair for Operating Systems,
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; RWTH Aachen University
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;
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; Licensed under the Apache License, Version 2.0 (the "License");
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; you may not use this file except in compliance with the License.
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; You may obtain a copy of the License at
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;
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; http://www.apache.org/licenses/LICENSE-2.0
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;
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; Unless required by applicable law or agreed to in writing, software
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; distributed under the License is distributed on an "AS IS" BASIS,
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; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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; See the License for the specific language governing permissions and
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; limitations under the License.
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;
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; This file is part of MetalSVM.
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; This is the kernel's entry point for the application processors. We switch to the
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; protected mode and jump to our MetalSVM kernel.
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[BITS 16]
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SECTION .text
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GLOBAL _start
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ORG 0x10000
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_start:
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jmp _realstart
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struc GDT_STR
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s0_15: resw 1
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b0_15: resw 1
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b16_23: resb 1
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flags: resb 1
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access: resb 1
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b24_31: resb 1
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endstruc
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gdt_start dw gdt_size
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gdt_ptr dd dummy_descriptor
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dummy_descriptor: istruc GDT_STR
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at s0_15, dw 0
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at b0_15, dw 0
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at b16_23, db 0
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at flags, db 0
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at access, db 0
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at b24_31, db 0
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iend
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; 4GB 32-bit code , 9ah = 10011010b = Present, DPL 00,No System, Code Exec/Read.
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code32_descriptor: istruc GDT_STR
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at s0_15, dw 0x0ffff
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at b0_15, dw 0
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at b16_23, db 0
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at flags, db 0x9a
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at access, db 0xcf
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at b24_31, db 0
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iend
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; 4GB 32-bit data, 92h = 10010010b = Present, DPL 00, No System, Data Read/Write
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data32_descriptor: istruc GDT_STR
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at s0_15, dw 0x0ffff
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at b0_15, dw 0
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at b16_23, db 0
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at flags, db 0x92
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at access, db 0xcf
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at b24_31, db 0
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iend
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gdt_size equ $ - (dummy_descriptor) - 1
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_realstart:
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lgdt [gdt_start]
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; switch to protected mode by setting PE bit
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mov eax, cr0
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or al, 0x1
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mov cr0, eax
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; far jump to the 32bit code
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jmp dword 0x08 : _pmstart
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[BITS 32]
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_pmstart:
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cli
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xor eax, eax
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mov ax, 0x10
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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 ss, ax
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; enable cache and turn on FPU exceptions
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mov eax, cr0
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and eax, 0x9fffffff
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or eax, 0x20
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mov cr0, eax
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; clear the current pgd entry
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xor eax, eax
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mov cr3, eax
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; set stack pointer
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mov esp, 0xDEADBEEF
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xor eax, eax
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xor ebx, ebx
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jmp 0x08 : 0xDEADC0DE
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