Cream of the Crop 1

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Assembly Source File | 1992-06-15 | 13.1 KB | 358 lines

;dbinit.asm ;Debugger initialization routines ; .386P ;---------------------------------------------------------------------------- ;Copyright 1991, 1992 ASMicro Co. ;7/6/91 Rick Knoblaugh ;----------------------------------------------------------------------------- include dbequ.inc include dbstruc.inc include dbmac.inc include dbpdat.inc data segment para public 'data16' use16 extrn gdtl:fword, gdtlim:word, gdtadrs:dword extrn idtl:fword, idtlim:word, idtadrs:dword extrn DATA_BEG:abs, DATA_END:abs, video_seg:word data ends ;-------------------------------------------------------------- ;EXTERNALS | ;-------------------------------------------------------------- isrcode segment para public 'icode16' use16 extrn int_0:far, int_1:far, int_2:far, int_3:far, int_4:far extrn int_5:far, int_6:far, int_7:far, except_8:far extrn except_9:far, except_0ah:far, except_0bh:far extrn except_0ch:far, except_0dh:far, except_0eh:far extrn except_0fh:far, int_20h:far, int_21h:far extrn int_22h:far, int_23h:far, int_24h:far, int_25h:far extrn int_26h:far, int_27h:far, int_70h:far, int_71h:far extrn int_72h:far, int_73h:far, int_74h:far, int_75h:far extrn int_76h:far, int_77h:far isrcode ends zcode segment para public 'code16' use16 assume cs:zcode, ds:data, es:data .8086 last_code label byte sign_msg1 db 'DB Version 1.0', CR, LF, '$' sign_msg2 db 'Copyright ASMicro Co. 1991, 1992', CR, LF , CR, LF, '$' noprot_msg db 'Can not run if already in protected mode.',BEEP, CR, LF, '$' not386_msg db 'Program requires at least an 80386.', BEEP, CR, LF, '$' start proc far push ds ;save psp seg mov ax, data mov es, ax mov ds, ax call verify_cpu jnc short start_200 ;continue if 386/486 in real mode assume ds:zcode push cs pop ds ;get segment for messages mov ah, DOS_PRT_STRING int 21h mov ax, 4c01h int 21h .386P start_200: call init_gdt call init_tss mov ax, data mov ds, ax assume ds:data cli ;no ints until protected mode mov ax, gdt_seg movzx eax, ax shl eax, 4 mov gdtadrs, eax mov gdtlim, (GDT_END-GDT_BEG)-1 mov ax, idt_seg movzx eax, ax shl eax, 4 mov idtadrs, eax mov idtlim, (IDT_END-IDT_BEG)-1 call reprogram_pic lgdt gdtl lidt idtl mov dx, dbstack3 ;get stack segment mov bx, sp ;and pointer mov eax, cr0 or eax, 1 ;turn on protected mode bit mov cr0, eax ;go into protected mode ; ;jump to clear prefetch queue ; db 0eah ;far jump dw offset zcode:start_400 dw gdt_seg:sel_code start_400: mov ax, offset gdt_seg:sel_tss ltr ax xor ax, ax lldt ax ;null ldt mov ax, seg data movzx eax, ax push eax ;gs push eax ;fs push eax ;ds push eax ;es push 0 push dx ;stack segment push 0 push bx ;stack pointer push 2 ;VM bit set in upper eflags push 3000h ;NT=0, IOPL=3, CLI in lower eflags push 0 push seg zcode ;cs of where to return push 0 push offset zcode:start_500 ;ip of where to return ; ;Must ensure that Nested Task bit is not set in eflags. If it were, ;processor would attempt to switch to a task via the selector in ;the TSS backlink field. Since that field is now zero, an invalid TSS ;fault would occur. ; pushf pop ax btr ax, nest_taskf push ax popf iretd start_500: ;begin vm86 task here pop bx ;get saved psp seg sti ;interrupts ok now assume ds:zcode push cs pop ds mov dx, offset sign_msg1 mov ah, DOS_PRT_STRING int 21h mov dx, offset sign_msg2 mov ah, DOS_PRT_STRING int 21h mov dx, zcode + 1 mov ax, offset last_code shr ax, 4 add dx, ax sub dx, bx ;paragraphs to keep mov ax, (DOS_TSR_FUNC SHL 8) ;exit code 0 int 21h start endp reprogram_pic proc near in al, 21h mov ah, al mov al, 11h ;init out 20h, al mov al, 20h ;irq0 to int 20h out 21h, al jmp short $ + 2 jmp short $ + 2 mov al, 4 out 21h, al jmp short $ + 2 jmp short $ + 2 mov al, 1 out 21h, al jmp short $ + 2 jmp short $ + 2 mov al, ah out 21h, al ret reprogram_pic endp .8086 verify_cpu proc near xor ax, ax push ax popf pushf pop ax and ax, 0f000h cmp ax, 0f000h jz verify_c800 ;not 386 mov ax, 0f000h push ax popf pushf pop ax and ax, 0f000h jz verify_c800 ;not 386 mov dx, offset noprot_msg .386P smsw ax ;get pm flag into carry rcr ax, 1 jmp short verify_c999 verify_c800: mov dx, offset not386_msg stc verify_c999: ret verify_cpu endp init_gdt proc near mov ax, gdt_seg mov ds, ax assume ds:gdt_seg mov dx, tss_seg movzx edx, dx ;base data segment mov ecx, (TSS_END - TSS_BEG ) - 1 ;limit mov ah, TSS_DESC mov si, offset sel_tss call make_entry mov dx, tss_seg movzx edx, dx ;base data segment mov ecx, (TSS_END - TSS_BEG ) - 1 ;limit mov ah, RW_DATA ;alias as r/w for editing mov si, offset sel_tss_alias call make_entry mov dx, gdt_seg movzx edx, dx ;base data segment mov ecx, (GDT_END - GDT_BEG ) - 1 ;limit mov ah, RW_DATA ;alias as r/w for editing mov si, offset sel_gdt_alias call make_entry mov dx, isrcode movzx edx, dx ;base of isr code segment mov ecx, 0ffffh ;max segment size mov ah, ER_CODE mov si, offset sel_isrcode call make_entry mov dx, zcode movzx edx, dx ;base code segment mov ecx, 0ffffh ;max segment size mov ah, ER_CODE mov si, offset sel_code call make_entry xor edx, edx ;zero base mov ecx, 8fffffh ;page granularity and 4 gig limit mov ah, RW_DATA mov si, offset sel_databs call make_entry mov dx, dbstack ;PL0 stack movzx edx, dx ;base stack segment mov ecx, (STACK_END - STACK_BEG ) - 1 ;limit mov ah, RW_DATA mov si, offset sel_stack call make_entry mov dx, dbstack3 ;PL3 stack movzx edx, dx ;base stack segment mov ecx, (STACK3_END - STACK3_BEG ) - 1 ;limit mov ah, RW_DATA mov si, offset sel_stack3 call make_entry mov dx, data movzx edx, dx ;base data segment mov cx, DATA_END sub cx, DATA_BEG dec cx movzx ecx, cx mov ah, RW_DATA mov si, offset sel_data call make_entry int 11h ;equipment check mov edx, 0b800h ;color segment and al, 30h ;monitor bits cmp al, 30h ;30h=monochrome jne init_gdt500 mov edx, 0b000h ;monochrome segment init_gdt500: mov es:video_seg, dx ;save video segment mov ecx, (PAGE_SIZE * 4) - 1 mov ah, RW_DATA mov si, offset sel_video call make_entry ret init_gdt endp ;-------------------------------------------------------------- ;make_entry - Load a GDT entry from information passed as | ; follows: | ; | ; ds=gdt segent | ; si=offset of gdt entry to load | ; ah=type | dpl | ; ecx=limit (also, bits 23:20 are g, b, 0, and avl)| ; edx=base segment (convert it to linear) | ;-------------------------------------------------------------- make_entry proc near shl edx, 4 ;convert seg to linear mov [si].seg_limit_low, cx mov [si].seg_base_low, dx shr edx, 16 mov [si].seg_base_mid, dl mov [si].seg_type_dpl, ah shr ecx, 16 mov [si].seg_limit_gran, cl mov [si].seg_base_top, dh ret make_entry endp ;-------------------------------------------------------------- ;init_tss - Initilize TSS with base of I/O bit map and set | ; appropriate bits in I/O bit map per cmd line. | ; | ;-------------------------------------------------------------- init_tss proc near mov ax, tss_seg mov ds, ax assume ds:tss_seg xor si, si mov ax, offset gdt_seg:sel_stack mov [si].t_ess0, ax mov ax, offset dbstack:db_sp movzx eax, ax mov [si].t_esp0, eax lea bx, [si].t_iomap mov [si].t_iobase, bx ret init_tss endp zcode ends end start