b209403ccb
git-svn-id: http://svn.lfbs.rwth-aachen.de/svn/scc/trunk/MetalSVM@127 315a16e6-25f9-4109-90ae-ca3045a26c18
161 lines
3.2 KiB
NASM
161 lines
3.2 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. We could either call main here,
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; or we can use this to setup the stack or other nice stuff, like
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; perhaps setting up the GDT and segments. Please note that interrupts
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; are disabled at this point: More on interrupts later!
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[BITS 16]
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SECTION .text
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GLOBAL _start
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ORG 0
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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 0
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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 = Presetn , 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)
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msg db "0ello from MetalSVM bootloader!!",0
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enable_A20:
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call a20wait
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mov al,0xAD
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out 0x64,al
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call a20wait
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mov al,0xD0
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out 0x64,al
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call a20wait2
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in al,0x60
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push eax
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call a20wait
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mov al,0xD1
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out 0x64,al
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call a20wait
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pop eax
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or al,2
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out 0x60,al
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call a20wait
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mov al,0xAE
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out 0x64,al
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call a20wait
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ret
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a20wait:
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in al,0x64
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test al,2
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jnz a20wait
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ret
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a20wait2:
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in al,0x64
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test al,1
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jz a20wait2
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ret
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_realstart:
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cli
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cld
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mov [msg], BYTE 'H'
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mov ax, dummy_descriptor
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mov [gdt_ptr], ax
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mov bx, gdt_start
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lgdt [bx]
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; call enable_A20
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; switch to protected mode by setting PE bit
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; we also clear the VM bit
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mov eax, cr0
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or eax, 0x1
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and eax, 0x7FFFFFFF
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mov cr0, eax
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; far jump
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db 0x66 ; Prefix for 32-bit
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db 0xea ; Opcode for far jump
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dd _pmstart ; Offset to start, 32-bit
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dw 0x08 ; This is the selector for CODE32_DESCRIPTOR,
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; assuming that start address resides in this segment
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[BITS 32]
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_pmstart:
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; MetalSVM support Multiboot
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; => Therefore, we switch to the same machine state. Afterwards, we jump to our kernel
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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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mov eax, 0x2BAD002
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xor ebx, ebx ; => it exists n valid multiboot information structure
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jmp 0x08 : 0x100000
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TIMES 4080 - ($-$$) DB 0
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[BITS 16]
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_start:
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jmp _realstart
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TIMES 4096 - ($-$$) DB 0
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