| 1 | ; File name : BootVars.asm
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| 2 | ; Project name : IDE BIOS
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| 3 | ; Created date : 1.4.2010
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| 4 | ; Last update : 12.4.2010
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| 5 | ; Author : Tomi Tilli
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| 6 | ; Description : Functions to access BOOTVARS struct.
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| 7 |
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| 8 | ; Section containing code
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| 9 | SECTION .text
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| 10 |
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| 11 | ;--------------------------------------------------------------------
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| 12 | ; Stores POST stack pointer to BOOTVARS.
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| 13 | ;
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| 14 | ; BootVars_StorePostStackPointer
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| 15 | ; Parameters:
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| 16 | ; DS: BDA and Interrupt Vector segment (zero)
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| 17 | ; Returns:
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| 18 | ; Nothing
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| 19 | ; Corrupts registers:
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| 20 | ; AX
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| 21 | ;--------------------------------------------------------------------
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| 22 | ALIGN JUMP_ALIGN
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| 23 | BootVars_StorePostStackPointer:
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| 24 | pop ax ; Pop return address
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| 25 | mov [BOOTVARS.dwPostStack], sp
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| 26 | mov [BOOTVARS.dwPostStack+2], ss
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| 27 | jmp ax
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| 28 |
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| 29 |
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| 30 | ;--------------------------------------------------------------------
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| 31 | ; Initializes stack for boot menu usage.
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| 32 | ; POST stack is not large enough when DPTs are stored to 30:0h.
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| 33 | ;
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| 34 | ; BootVars_SwitchToBootMenuStack
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| 35 | ; Parameters:
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| 36 | ; Nothing
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| 37 | ; Returns:
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| 38 | ; SS:SP: Pointer to top of Boot Menu stack
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| 39 | ; Corrupts registers:
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| 40 | ; AX
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| 41 | ;--------------------------------------------------------------------
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| 42 | ALIGN JUMP_ALIGN
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| 43 | BootVars_SwitchToBootMenuStack:
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| 44 | pop ax ; Pop return address
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| 45 | cli ; Disable interrupts
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| 46 | LOAD_BDA_SEGMENT_TO ss, sp
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| 47 | mov sp, BOOTVARS.rgbMnuStack ; Load offset to stack
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| 48 | sti ; Enable interrupts
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| 49 | jmp ax
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| 50 |
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| 51 |
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| 52 | ;--------------------------------------------------------------------
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| 53 | ; Restores SS and SP to initial boot loader values.
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| 54 | ;
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| 55 | ; BootVars_SwitchBackToPostStack
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| 56 | ; Parameters:
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| 57 | ; Nothing
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| 58 | ; Returns:
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| 59 | ; SS:SP: Ptr to POST stack
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| 60 | ; Corrupts registers:
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| 61 | ; AX
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| 62 | ;--------------------------------------------------------------------
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| 63 | ALIGN JUMP_ALIGN
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| 64 | BootVars_SwitchBackToPostStack:
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| 65 | pop ax ; Pop return address
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| 66 | cli ; Disable interrupts
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| 67 | LOAD_BDA_SEGMENT_TO ss, sp
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| 68 | eLSS sp, ss:BOOTVARS.dwPostStack
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| 69 | sti ; Enable interrupts
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| 70 | jmp ax
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| 71 |
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| 72 |
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| 73 | ;--------------------------------------------------------------------
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| 74 | ; Backups system INT 18h ROM Boot / Boot Failure handler and
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| 75 | ; installs our own for boot menu INT 18h callbacks.
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| 76 | ;
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| 77 | ; BootVars_StoreSystemInt18hAndInstallOurs
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| 78 | ; Parameters:
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| 79 | ; DS: BDA and Interrupt Vector segment (zero)
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| 80 | ; Returns:
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| 81 | ; Nothing
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| 82 | ; Corrupts registers:
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| 83 | ; AX, BX, ES
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| 84 | ;--------------------------------------------------------------------
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| 85 | ALIGN JUMP_ALIGN
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| 86 | BootVars_StoreSystemInt18hAndInstallOurs:
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| 87 | mov bx, INTV_BOOT_FAILURE*4 ; Offset to INT 18h vector
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| 88 | les ax, [bx] ; Load system INT 18h
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| 89 | mov [BOOTVARS.dwSys18h], ax
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| 90 | mov [BOOTVARS.dwSys18h+2], es
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| 91 | mov WORD [bx], Int18h_BootError ; Install our INT 18h
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| 92 | mov WORD [bx+2], cs
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| 93 | ret
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| 94 |
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| 95 |
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| 96 | ;--------------------------------------------------------------------
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| 97 | ; Restores system INT 18h ROM Boot or Boot Error handler.
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| 98 | ;
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| 99 | ; BootVars_RestoreSystemInt18h
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| 100 | ; Parameters:
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| 101 | ; Nothing
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| 102 | ; Returns:
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| 103 | ; Nothing
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| 104 | ; Corrupts registers:
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| 105 | ; AX, DS, ES
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| 106 | ;--------------------------------------------------------------------
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| 107 | ALIGN JUMP_ALIGN
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| 108 | BootVars_RestoreSystemInt18h:
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| 109 | LOAD_BDA_SEGMENT_TO ds, ax
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| 110 | les ax, [BOOTVARS.dwSys18h]
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| 111 | mov [INTV_BOOT_FAILURE*4], ax
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| 112 | mov [INTV_BOOT_FAILURE*4+2], es
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| 113 | ret
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