source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int19h.asm@ 597

Last change on this file since 597 was 597, checked in by Tomi Tilli, 6 years ago

Windows 95 CMOS hack now works with Award BIOSes.
Some small optimizations to INT 19h and INT 19h reset handlers.
Added menuitem to configurator for clearing BDA drive count.

File size: 8.2 KB
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1; Project name : XTIDE Universal BIOS
2; Description : Int 19h Handler (Boot Loader).
3
4;
5; XTIDE Universal BIOS and Associated Tools
6; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
7;
8; This program is free software; you can redistribute it and/or modify
9; it under the terms of the GNU General Public License as published by
10; the Free Software Foundation; either version 2 of the License, or
11; (at your option) any later version.
12;
13; This program is distributed in the hope that it will be useful,
14; but WITHOUT ANY WARRANTY; without even the implied warranty of
15; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16; GNU General Public License for more details.
17; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
18;
19
20; Section containing code
21SECTION .text
22
23;--------------------------------------------------------------------
24; Int19h_BootLoaderHandler
25; Parameters:
26; Nothing
27; Returns:
28; Never returns (loads operating system)
29;--------------------------------------------------------------------
30Int19h_BootLoaderHandler:
31 sti ; Enable interrupts
32%ifdef CLD_NEEDED
33 cld ; String instructions to increment pointers
34%endif
35%ifdef MODULE_VERY_LATE_INIT
36 LOAD_BDA_SEGMENT_TO ds, ax ; Load BDA segment (zero) to DS
37 les ax, [TEMPORARY_VECTOR_FOR_SYSTEM_INT13h*4]
38 mov [BIOS_DISK_INTERRUPT_13h*4], ax
39 mov [BIOS_DISK_INTERRUPT_13h*4+2], es
40 push ds ; BDA segment (zero)...
41 pop es ; ...to ES
42%else
43 LOAD_BDA_SEGMENT_TO es, ax ; Load BDA segment (zero) to ES
44%endif
45 ; Fall to .PrepareBootLoaderStack
46
47
48;--------------------------------------------------------------------
49; Drive detection and boot menu use lots of stack so it is
50; wise to relocate stack. Otherwise something important from
51; interrupt vectors are likely corrupted, likely our own DPTs if
52; they are located to 30:0h.
53;
54; .PrepareBootLoaderStack
55; Parameters:
56; ES: BDA and interrupt vector segment (zero)
57; Returns:
58; Never returns (loads operating system)
59;--------------------------------------------------------------------
60.PrepareBootLoaderStack:
61 STORE_POST_STACK_POINTER
62 SWITCH_TO_BOOT_MENU_STACK
63 ; Fall to .InitializeDisplay
64
65
66;--------------------------------------------------------------------
67; .InitializeDisplay
68; Parameters:
69; ES: BDA and interrupt vector segment (zero)
70; Returns:
71; Never returns (loads operating system)
72;--------------------------------------------------------------------
73.InitializeDisplay:
74 ; Change display mode if necessary
75 mov ax, [cs:ROMVARS.wDisplayMode] ; AH 00h = Set Video Mode
76 cmp al, DEFAULT_TEXT_MODE
77 je SHORT .InitializeDisplayLibrary
78 int BIOS_VIDEO_INTERRUPT_10h
79.InitializeDisplayLibrary:
80 call DetectPrint_InitializeDisplayContext
81 ; Fall to .InitializeBiosAndDetectDrives
82
83
84;--------------------------------------------------------------------
85; .InitializeBiosAndDetectDrives
86; Parameters:
87; ES: BDA and interrupt vector segment (zero)
88; Returns:
89; DS: RAMVARS segment
90;--------------------------------------------------------------------
91.InitializeBiosAndDetectDrives:
92 call Initialize_AndDetectDrives
93
94%ifdef MODULE_HOTKEYS
95 ; Last hard drive might have scrolled Hotkey Bar out of screen.
96 ; We want to display it during wait.
97 call HotkeyBar_UpdateDuringDriveDetection
98
99.WaitUntilTimeToCloseHotkeyBar:
100 call TimerTicks_ReadFromBdaToAX
101 sub ax, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeWhenDisplayed]
102 cmp ax, MIN_TIME_TO_DISPLAY_HOTKEY_BAR
103 jb SHORT .WaitUntilTimeToCloseHotkeyBar
104%endif
105 ; Fall to .ResetAllDrives
106
107
108;--------------------------------------------------------------------
109; .ResetAllDrives
110; Parameters:
111; DS: RAMVARS segment
112; ES: BDA and interrupt vector segment (zero)
113; Returns:
114; Nothing
115;--------------------------------------------------------------------
116.ResetAllDrives:
117 ; Reset all drives in the system, not just our drives.
118 xor ax, ax ; Disk Controller Reset
119 mov dl, 80h ; Reset all hard drives and floppy drives
120 int BIOS_DISK_INTERRUPT_13h
121 ; Fall to SelectDriveToBootFrom
122
123
124;--------------------------------------------------------------------
125; SelectDriveToBootFrom
126; Parameters:
127; DS: RAMVARS segment
128; ES: BDA and interrupt vector segment (zero)
129; Returns:
130; Never returns (loads operating system)
131;--------------------------------------------------------------------
132; The following macro could be easily inlined below. Why a macro? Depending on the combination
133; of MODULE_HOTKEYS or MODULE_BOOT_MENU, this code needs to either come before or after the
134; call to the boot menu.
135;
136%macro TRY_TO_BOOT_DL_AND_DH_DRIVES 0
137 push dx ; it's OK if this is left on the stack, if we are
138 ; successful, the following call does not return
139 call BootSector_TryToLoadFromDriveDL_AndBoot
140 pop dx
141 mov dl, dh
142 call BootSector_TryToLoadFromDriveDL_AndBoot
143%endmacro
144
145
146SelectDriveToBootFrom: ; Function starts here
147%ifdef MODULE_HOTKEYS
148 call HotkeyBar_UpdateDuringDriveDetection
149 mov al, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode]
150 cmp al, ROM_BOOT_HOTKEY_SCANCODE
151 je SHORT .RomBoot ; CF clear so ROM boot
152%ifdef MODULE_BOOT_MENU
153 cmp al, BOOT_MENU_HOTKEY_SCANCODE
154 je SHORT .BootMenu
155%endif ; MODULE_BOOT_MENU
156
157.TryUsingHotKeysCode:
158 call HotkeyBar_GetBootDriveNumbersToDX
159 call DriveXlate_SetDriveToSwap ; Enable primary boot device translation
160 xchg dl, dh
161 call DriveXlate_SetDriveToSwap ; Enable secondary boot device translation
162 xchg dl, dh
163 call DriveXlate_ToOrBack ; Translate now so boot device will appear as 00h or 80h to OS
164 TRY_TO_BOOT_DL_AND_DH_DRIVES
165 ;; falls through to boot menu, if it is present. If not present, falls through to rom boot.
166%endif ; MODULE_HOTKEYS
167
168
169%ifdef MODULE_BOOT_MENU
170.BootMenu:
171 call BootMenu_DisplayAndReturnDriveInDLRomBootClearCF
172 jnc SHORT .RomBoot ; CF clear so ROM boot
173
174 call DriveXlate_Reset
175%ifdef MODULE_HOTKEYS
176 jmp SHORT .TryUsingHotKeysCode ; Selected drive stored as hotkey
177%else ; Boot menu without hotkeys, secondary boot drive is always 00h or 80h
178 mov dh, dl ; Setup for secondary drive
179 not dh ; Floppy goes to HD, or vice versa
180 and dh, 80h ; Go to first drive of the floppy or HD set
181 call DriveXlate_SetDriveToSwap
182 call DriveXlate_ToOrBack
183 TRY_TO_BOOT_DL_AND_DH_DRIVES
184 jmp SHORT .BootMenu ; Show boot menu again
185%endif ; MODULE_HOTKEYS
186
187%endif ; MODULE_BOOT_MENU
188
189; No hotkeys and no boot menu means fixed "A then C" boot order
190%ifndef MODULE_HOTKEYS OR MODULE_BOOT_MENU
191 xor dl, dl ; Try to boot from Floppy Drive A
192 call BootSector_TryToLoadFromDriveDL_AndBoot
193 mov dl, 80h ; Try to boot from Hard Drive C
194 call BootSector_TryToLoadFromDriveDL_AndBoot
195%endif
196
197.RomBoot:
198%ifdef MODULE_DRIVEXLATE
199 call DriveXlate_Reset ; Clean up any drive mappings before Rom Boot
200%endif
201 stc
202 ;; fall through to Int19h_JumpToBootSectorInESBXOrRomBoot
203
204;--------------------------------------------------------------------
205; Int19h_JumpToBootSectorInESBXOrRomBoot
206;
207; Switches back to the POST stack, clears the DS and ES registers,
208; and either jumps to the MBR (Master Boot Record) that was just read,
209; or calls the ROM's boot routine on interrupt 18.
210;
211; Parameters:
212; DL: Drive to boot from (translated, 00h or 80h)
213; CF: Clear for Boot Sector Boot
214; Set for ROM Boot
215; ES:BX: (if CF clear) Ptr to boot sector (ES = zero)
216;
217; Returns:
218; Never returns
219;--------------------------------------------------------------------
220Int19h_JumpToBootSectorInESBXOrRomBoot:
221 mov ax, es ; Clear AX. NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF
222 SWITCH_BACK_TO_POST_STACK
223
224; clear segment registers before boot sector or rom call
225Int19h_JumpToBootSectorInESBXOrRomBootWithoutStackChange:
226 mov ax, es ; Clear AX and preserve CF
227 mov ds, ax
228%ifdef USE_386
229 mov fs, ax
230 mov gs, ax
231%endif
232 jc SHORT .RomBoot
233
234; jump to boot sector
235 push es ; sgment address for MBR
236 push bx ; offset address for MBR
237 retf ; NOTE: DL is set to the drive number
238
239; Boot by calling INT 18h (ROM Basic of ROM DOS)
240.RomBoot:
241 int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns
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