| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Defines for BOOTVARS struct used by boot menu
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| 3 | ; and drive initialization.
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| 4 | %ifndef BOOTVARS_INC
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| 5 | %define BOOTVARS_INC
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| 6 |
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| 7 |
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| 8 | BOOT_READ_RETRY_TIMES EQU 3
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| 9 |
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| 10 |
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| 11 |
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| 12 | ; Pre-boot variables. These do not exist after successful boot to OS.
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| 13 | ; Segment is always 0000h, same as BDA segment
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| 14 | struc BOOTVARS
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| 15 | resb 7C00h
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| 16 | .rgbAtaInfo: ; 7C00h, ATA Information for drive detection
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| 17 | .rgbBootSect resb 512 ; 7C00h, Boot sector
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| 18 | resb 256 ; Boot Menu stack
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| 19 | .rgbMnuStack:
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| 20 | .dwPostStack resb 4 ; POST stack pointer when entering INT 19h
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| 21 | .wMagicWord resb 2 ; I wish we didn't need this
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| 22 | .rgBootNfo: ; Array containing BOOTNFO structs
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| 23 | endstruc
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| 24 |
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| 25 | ; Magic WORD to detect when BOOTVARS is available.
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| 26 | BOOTVARS_MAGIC_WORD EQU 1110011001100111b
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| 27 |
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| 28 |
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| 29 |
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| 30 | ;--------------------------------------------------------------------
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| 31 | ; Stores POST stack pointer to BOOTVARS.
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| 32 | ;
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| 33 | ; STORE_POST_STACK_POINTER
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| 34 | ; Parameters:
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| 35 | ; ES: BDA and Interrupt Vector segment (zero)
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| 36 | ; Returns:
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| 37 | ; Nothing
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| 38 | ; Corrupts registers:
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| 39 | ; Nothing
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| 40 | ;--------------------------------------------------------------------
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| 41 | %macro STORE_POST_STACK_POINTER 0
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| 42 | mov [es:BOOTVARS.dwPostStack], sp
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| 43 | mov [es:BOOTVARS.dwPostStack+2], ss
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| 44 | %endmacro
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| 45 |
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| 46 |
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| 47 | ;--------------------------------------------------------------------
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| 48 | ; Initializes stack for boot menu usage.
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| 49 | ; POST stack is not large enough when DPTs are stored to 30:0h.
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| 50 | ;
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| 51 | ; Note regarding LOAD_BDA_SEGMENT_TO: If you force the use of SP
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| 52 | ; then you also have to unconditionally enable the CLI/STI pair.
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| 53 | ; The reason for this is that only some buggy 808x CPU:s need the
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| 54 | ; CLI/STI instruction pair when changing stacks. Other CPU:s disable
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| 55 | ; interrupts automatically when SS is modified for the duration of
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| 56 | ; the immediately following instruction to give time to change SP.
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| 57 | ;
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| 58 | ; SWITCH_TO_BOOT_MENU_STACK
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| 59 | ; Parameters:
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| 60 | ; Nothing
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| 61 | ; Returns:
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| 62 | ; SS:SP: Pointer to top of Boot Menu stack
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| 63 | ; Corrupts registers:
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| 64 | ; Nothing
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| 65 | ;--------------------------------------------------------------------
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| 66 | %macro SWITCH_TO_BOOT_MENU_STACK 0
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| 67 | %ifndef USE_186
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| 68 | cli ; Disable interrupts
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| 69 | %endif
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| 70 | LOAD_BDA_SEGMENT_TO ss, sp
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| 71 | mov sp, BOOTVARS.rgbMnuStack ; Load offset to stack
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| 72 | %ifndef USE_186
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| 73 | sti ; Enable interrupts
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| 74 | %endif
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| 75 | %endmacro
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| 76 |
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| 77 |
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| 78 | ;--------------------------------------------------------------------
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| 79 | ; Restores SS and SP to initial boot loader values.
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| 80 | ;
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| 81 | ; Note! Must return with AX=0 and CF preserved.
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| 82 | ; See Int19hMenu_JumpToBootSector_or_RomBoot.
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| 83 | ;
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| 84 | ; SWITCH_BACK_TO_POST_STACK
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| 85 | ; Parameters:
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| 86 | ; AX: BDA and Interrupt Vector segment (zero)
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| 87 | ; Returns:
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| 88 | ; SS:SP: Ptr to POST stack
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| 89 | ; Corrupts registers:
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| 90 | ; Nothing (not even FLAGS)
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| 91 | ;--------------------------------------------------------------------
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| 92 | %macro SWITCH_BACK_TO_POST_STACK 0
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| 93 | %ifndef USE_386
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| 94 | cli
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| 95 | mov ss, ax
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| 96 | mov sp, [ss:BOOTVARS.dwPostStack]
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| 97 | mov ss, [ss:BOOTVARS.dwPostStack+2]
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| 98 | sti
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| 99 | %else
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| 100 | mov ss, ax
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| 101 | lss sp, [ss:BOOTVARS.dwPostStack]
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| 102 | %endif
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| 103 | %endmacro
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| 104 |
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| 105 |
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| 106 | %endif ; BOOTVARS_INC
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