| 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 | ; Boot Menu Information Table. These are generated for all XTIDE Universal
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| 12 | ; BIOS drives. Available only until boot is successfull.
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| 13 | LEN_BOOTNFO_DRV EQU 26 ; Bytes reserved for drive name
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| 14 | struc BOOTNFO
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| 15 | .twSectCnt resb 6 ; Total user addressable sectors
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| 16 | .szDrvName resb LEN_BOOTNFO_DRV+1 ; Drive name
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| 17 | resb 1 ; Alignment
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| 18 | endstruc
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| 19 |
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| 20 |
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| 21 | ; Pre-boot variables. These do not exist after successfull boot to OS.
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| 22 | ; Segment is always 0000h, same as BDA segment
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| 23 | struc BOOTVARS
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| 24 | resb 7C00h
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| 25 | .rgbAtaInfo: ; 7C00h, ATA Information for drive detection
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| 26 | .rgbBootSect resb 512 ; 7C00h, Boot sector
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| 27 | resb 256 ; Boot Menu stack
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| 28 | .rgbMnuStack:
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| 29 | .dwPostStack resb 4 ; POST stack pointer when entering INT 19h
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| 30 | .rgBootNfo: ; Array containing BOOTNFO structs
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| 31 | endstruc
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| 32 |
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| 33 |
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| 34 | ;--------------------------------------------------------------------
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| 35 | ; Stores POST stack pointer to BOOTVARS.
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| 36 | ;
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| 37 | ; STORE_POST_STACK_POINTER
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| 38 | ; Parameters:
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| 39 | ; DS: BDA and Interrupt Vector segment (zero)
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| 40 | ; Returns:
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| 41 | ; Nothing
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| 42 | ; Corrupts registers:
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| 43 | ; Nothing
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| 44 | ;--------------------------------------------------------------------
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| 45 | %macro STORE_POST_STACK_POINTER 0
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| 46 | mov [BOOTVARS.dwPostStack], sp
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| 47 | mov [BOOTVARS.dwPostStack+2], ss
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| 48 | %endmacro
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| 49 |
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| 50 |
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| 51 | ;--------------------------------------------------------------------
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| 52 | ; Initializes stack for boot menu usage.
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| 53 | ; POST stack is not large enough when DPTs are stored to 30:0h.
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| 54 | ;
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| 55 | ; Note regarding LOAD_BDA_SEGMENT_TO: If you force the use of SP
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| 56 | ; then you also have to unconditionally enable the CLI/STI pair.
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| 57 | ; The reason for this is that only some buggy 808x CPU:s need the
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| 58 | ; CLI/STI instruction pair when changing stacks. Other CPU:s disable
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| 59 | ; interrupts automatically when SS is modified for the duration of
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| 60 | ; the immediately following instruction to give time to change SP.
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| 61 | ;
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| 62 | ; SWITCH_TO_BOOT_MENU_STACK
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| 63 | ; Parameters:
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| 64 | ; Nothing
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| 65 | ; Returns:
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| 66 | ; SS:SP: Pointer to top of Boot Menu stack
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| 67 | ; Corrupts registers:
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| 68 | ; Nothing
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| 69 | ;--------------------------------------------------------------------
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| 70 | %macro SWITCH_TO_BOOT_MENU_STACK 0
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| 71 | %ifndef USE_186
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| 72 | cli ; Disable interrupts
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| 73 | %endif
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| 74 | LOAD_BDA_SEGMENT_TO ss, sp
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| 75 | mov sp, BOOTVARS.rgbMnuStack ; Load offset to stack
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| 76 | %ifndef USE_186
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| 77 | sti ; Enable interrupts
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| 78 | %endif
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| 79 | %endmacro
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| 80 |
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| 81 |
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| 82 | ;--------------------------------------------------------------------
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| 83 | ; Restores SS and SP to initial boot loader values.
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| 84 | ;
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| 85 | ; Before doing any changes, see the note regarding
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| 86 | ; LOAD_BDA_SEGMENT_TO in BootVars_SwitchToBootMenuStack
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| 87 | ;
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| 88 | ; SWITCH_BACK_TO_POST_STACK
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| 89 | ; Parameters:
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| 90 | ; Nothing
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| 91 | ; Returns:
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| 92 | ; SS:SP: Ptr to POST stack
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| 93 | ; Corrupts registers:
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| 94 | ; Nothing
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| 95 | ;--------------------------------------------------------------------
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| 96 | %macro SWITCH_BACK_TO_POST_STACK 0
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| 97 | %ifndef USE_386
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| 98 | cli ; Disable interrupts
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| 99 | LOAD_BDA_SEGMENT_TO ss, sp
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| 100 | mov sp, [ss:BOOTVARS.dwPostStack]
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| 101 | mov ss, [ss:BOOTVARS.dwPostStack+2]
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| 102 | sti ; Enable interrupts
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| 103 | %else
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| 104 | LOAD_BDA_SEGMENT_TO ss, sp
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| 105 | lss sp, [ss:BOOTVARS.dwPostStack]
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| 106 | %endif
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| 107 | %endmacro
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| 108 |
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| 109 |
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| 110 | %endif ; BOOTVARS_INC
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