git.joshuawise.com / netwatch.git / blame
| Commit | Line | Data |
|---|---|---|
| f1584bb0 JW |
1 | ; realmode.asm |
| 2 | ; Routines to return the system to real mode | |
| 3 | ; NetWatch multiboot loader | |
| 4 | ; | |
| 5 | ; Copyright (c) 2008 Jacob Potter and Joshua Wise. All rights reserved. | |
| 6 | ; This program is free software; you can redistribute and/or modify it under | |
| 7 | ; the terms found in the file LICENSE in the root of this source tree. | |
| 8 | ||
| 042eafc7 JW |
9 | [bits 32] ; Starts in 32 bit mode, then will drop back later. |
| 10 | org 0x4000 | |
| 11 | entry: | |
| 12 | cli | |
| 13 | ; clean up 32 bit regs | |
| 14 | mov eax, 0x0 | |
| 15 | mov ebx, 0x0 | |
| 16 | mov ecx, 0x0 | |
| 17 | mov edx, 0x0 | |
| 18 | mov esi, 0x0 | |
| 19 | mov edi, 0x0 | |
| 20 | mov ebp, 0x0 | |
| 21 | mov esp, 0x0 | |
| 22 | ||
| 23 | lgdt [gdtp] | |
| 24 | ||
| 25 | mov ax, 0x10 | |
| 26 | mov ds, ax | |
| 27 | mov es, ax | |
| 28 | mov fs, ax | |
| 29 | mov gs, ax | |
| 30 | mov ss, ax | |
| 31 | ||
| 32 | jmp 0x8:nextp ; Clear CS bits now too | |
| 33 | ||
| 34 | nextp: | |
| 35 | ||
| 36 | mov eax, cr0 | |
| 37 | xor eax, 0x1 ; Clear PE | |
| 38 | mov cr0, eax | |
| 39 | ||
| 40 | jmp 0x0:nowreal ; and jmp away | |
| 41 | ||
| 42 | ||
| 43 | [bits 16] | |
| 44 | nowreal: | |
| 45 | mov long eax, 0x0000 | |
| 46 | mov ds, ax | |
| 47 | mov es, ax | |
| 48 | mov fs, ax | |
| 49 | mov gs, ax | |
| 50 | mov ss, ax | |
| 51 | ||
| 52 | mov sp, 0xFFFF ; set up the stack | |
| 53 | ||
| 54 | mov al, 0xAB | |
| 55 | out 0x80, al | |
| 56 | ||
| 57 | cli | |
| 58 | lidt [idtp] | |
| 59 | ||
| 60 | mov si, RETMSG | |
| 61 | call disp | |
| 62 | ||
| 63 | int 0x19 ; warm boot without clearing RAM. | |
| 64 | call handload_drive ; hopefully shouldn't happen | |
| 65 | ; ok, we give up | |
| 66 | cli | |
| 67 | halt: hlt | |
| 68 | jmp halt | |
| 69 | ||
| 70 | disp: | |
| 71 | lodsb | |
| 72 | or al, al | |
| 73 | jz .done | |
| 74 | mov ah, 0x0E | |
| 75 | mov bx, 0x0007 | |
| 76 | int 0x10 | |
| 77 | jmp disp | |
| 78 | .done: | |
| 79 | ret | |
| 80 | ||
| 81 | ; handload_drive should be unnecessary; int 19 should take care of it for | |
| 82 | ; us... | |
| 83 | handload_drive: | |
| 84 | mov ax, 0x07C0 | |
| 85 | mov es, ax | |
| 86 | mov ax, 0x0201 ; read one sector | |
| 87 | mov bx, 0x0000 ; to the normal location | |
| 88 | mov cx, 0x0001 ; disk sector 1 | |
| 89 | mov dx, 0x0080 ; drive 0 | |
| 90 | int 0x13 | |
| 91 | jc readerr | |
| 92 | ||
| 93 | mov si, READSUCC | |
| 94 | call disp | |
| 95 | ||
| 96 | jmp 0x7C0:0x0 ; and return control to grub! | |
| 97 | readerr: | |
| 98 | mov si, READFAIL | |
| 99 | call disp | |
| 100 | ret | |
| 101 | ||
| 102 | RETMSG db "SMM installer finished, booting your system of choice.",10,13,0 | |
| 103 | READSUCC db "Read successful; rebooting into boot sector.",10,13,0 | |
| 104 | READFAIL db "Boot disk read failure; system halted.",10,13,0 | |
| 105 | ||
| 106 | ||
| 107 | idtp db 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00 | |
| 108 | ||
| 109 | gdtp dw 0x1F | |
| 110 | dd gdt | |
| 111 | ||
| 112 | gdt dd 0, 0 | |
| 113 | dd 0x0000FFFF, 0x00009e00 ; CS | |
| 114 | dd 0x0000FFFF, 0x00009300 ; DS |