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Text File | 1995-11-01 | 28.7 KB | 971 lines

Page 60,132 ;--------------------------------------------------------------- ; BEGIN LISTING 1 ;--------------------------------------------------------------- ; ; 286LOAD.ASM Copyright (c) 1991 Robert Collins ; ; This program demonstrates various aspects of CPU ; behavior that become apparent when using LOADALL. ; ; Test 1: Checks that LOADALL loads all the general- ; purpose registers; loads the segment registers ; with values that are inconsistant to their ; respective descriptor cache registers. ; ; Test 2: Access extended memory in real mode. ; ; Test 3: Tests that the Present bit in a descriptor ; table can be loaded using LOADALL without ; generating exception 11. But when the segment ; is accessed, exception 13 is generated. ; NOTE: This test should be done in protected ; mode, but can be done in real mode. 1) In real ; mode, no error code is pushed on the stack ; (possibly due to a bug in the CPU). 2) Also ; in real mode, when this program is emulated on ; a '386, the '386 fails to set the Present bit ; when any subsequent segment in loaded. This ; latter condition is clearly a bug in the '386. ; ; This program was written for Microsoft MASM 5.1, and ; MS DOS 3.3. This program contains compiler directives ; and branching techniques that might not be available ; on previous versions of the Macro Assembler, nor in ; competitive products. If this program is executed on ; any version of DOS prior to 3.3, it will most certainaly ; cause the system to crash. No attempt is made in this ; program to be compatible with previous versions of DOS, ; but compatibility can be done, and is left as an ; exercise to the reader. ; ;--------------------------------------------------------------- ;--------------------------------------------------------------- ; Compiler directives ;--------------------------------------------------------------- Title LOADALL_286 .radix 16 .8086 ;--------------------------------------------------------------- ; Interrupt vector segment ;--------------------------------------------------------------- ABS0 segment at 0 org 06h*4 ; INT 06h vector INT_6 dd ? org 0467h ; PM Return address PM_Ret_off dw ? ; Offset PM_Ret_seg dw ? ; Segment org 800h ; LOADALL table loc'n. Loadall_Locn label word ABS0 ends ;--------------------------------------------------------------- ; Structure definitions ;--------------------------------------------------------------- Desc_cache STRUC ;; Hidden descriptor cache A15_A00 dw ? ;; format. A23_A16 db ? _Type db ? _Limit dw ? Desc_cache ENDS Loadall_struc STRUC ;; LOADALL memory image format dw 3 dup (0) _Msw dw 0 dw 7 dup (0) _Tr dw 0 _Flags dw 2 _Ip dw 0 _Ldt dw 0 _Ds dw 2222h _Ss dw 4444h _Cs dw 1111h _Es dw 3333h _Di dw 6666h _Si dw 7777h _Bp dw 5555h _Sp dw 8888h _Bx dw 2222h _Dx dw 4444h _Cx dw 3333h _Ax dw 1111h ES_Desc db 00,00,03,93h,0ffh,0ffh CS_Desc db 00,00,00,9bh,0ffh,0ffh SS_Desc db 00,00,04,93h,0ffh,0ffh DS_Desc db 00,00,02,93h,0ffh,0ffh Gdt_Desc db 00,00,00,00h,000h,000h Ldt_Desc db 00,00,06,82h,088h,000h Idt_Desc db 00,00,00,00h,0ffh,003h TSS_Desc db 00,00,05,89h,000h,008h Loadall_Struc ENDS Descriptor STRUC Seg_limit dw ? ; Segment limit Base_A15_A00 dw ? ; A00..A15 of base address Base_A23_A16 db ? ; A16..A23 of base address Access_rights db ? ; Segment access rights Limit_A19_A16 db ? ; Granularity, Op-size, ; Limit A16..A19 Base_A31_A24 db ? ; A24..A31 of base address Descriptor ENDS INT_Desc STRUC IGate_Offset dw ? ; Offset of handler CSEG_Sel dw ? ; Code segment selector db 0 db 86h ; 286 interrupt gate=16bit ; CS:IP, FLAGS Resvd dw 0 ; Reserved=0 INT_Desc ENDS ;--------------------------------------------------------------- ; Macro definitions ;--------------------------------------------------------------- FARJMP MACRO destination,selector ; dynamic JMP FAR SEG:OFF db 0eah ;; jmp instruction dw offset destination ;; offset word dw selector ;; segment selector word endm IO_DELAY MACRO out 0edh,ax endm LOADALL MACRO mov cx,ABS0 mov es,cx mov cx,(size Loadall_struc) / 2 mov si,offset Loadall_tbl mov di,800h rep movsw db 0fh,05 ENDM PRINT_STRING MACRO MSG_NAME mov ah,9 mov dx,offset MSG_NAME int 21h ENDM ;-------------------------------------------------------------- _DATA SEGMENT PARA PUBLIC 'DATA' ;--------------------------------------------------------------- ; Equates & local variables ;--------------------------------------------------------------- ; Protected mode access rights ;--------------------------------------------------------------- CS_access equ 10011011b DS_access equ 10010011b ;--------------------------------------------------------------- ; Text equates ;--------------------------------------------------------------- CRLF equ <0dh,0ah> CRLF$ equ <CRLF,'$'> INT6 equ [bp-4] ;--------------------------------------------------------------- ; Conditional compilation. Set USE_386=1 if you plan to execute ; this program on a '386 using EMULOAD. ;--------------------------------------------------------------- USE_386 equ 0 ;--------------------------------------------------------------- ; Loadall table(s) ;--------------------------------------------------------------- Loadall_tbl Loadall_struc <> Machine_State Loadall_struc <> ;--------------------------------------------------------------- ; Global Descriptor Table ;--------------------------------------------------------------- GDT_286 Descriptor <Gdt2_len-1,,,DS_access> CSEG2 Descriptor <0ffffh,,,CS_access> ; CS DSEG2 Descriptor <0ffffh,,,DS_access> ; DS Gdt2_len equ $-Gdt_286 ;--------------------------------------------------------------- ; Interrupt Descriptor Table ;--------------------------------------------------------------- IDT_286 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT00 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT01 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT02 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT03 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT04 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT05 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT06 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT07 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT08 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT09 INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT0a INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT0b INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT0c INT_Desc <Offset INT13,CSEG2-GDT_286> ; INT0d IDT2_Len equ $-IDT_286 ;--------------------------------------------------------------- ; Misc. local variables ;--------------------------------------------------------------- Mem_buffer db 400h dup (0) Results dw 0 i8259_1 db ? ; Status for master device i8259_2 db ? ; Status of slave device ;--------------------------------------------------------------- ; String Messages ;--------------------------------------------------------------- Passed db " PASSED.",CRLF$ Failed db "--> FAILED <--",CRLF$ Not_286 db "Not 80286 class computer.",CRLF$ Rmvd db "LOADALL removed from 80286 mask.",CRLF$ RFail db "Registers weren't loaded correctly." LF db CRLF$ ;--------------------------------------------------------------- ; I'm doing this wierd string definition technique to limit the ; page width to 64 characters. ;--------------------------------------------------------------- Test_1 label word db "Test 1: Testing 286 LOADALL instruction: ",24 Test_2 label word db "Test 2: Testing extended memory in real mode: ",24 Test_3 label word db "Test 3: Testing Present BIT in descriptor: ",24 _DATA ends _TEXT SEGMENT PARA PUBLIC 'CODE' ASSUME CS:_TEXT, DS:_DATA, ES:_DATA, SS:STACK .286p ;--------------------------------------------------------------- ; A little CS-relative data for the stack pointer. This is ; to avoid using other kludge techniques, caused by using ; LOADALL, that make using the data segment undesirable. ;--------------------------------------------------------------- Stack_ptr dw 0 dw 0 ;--------------------------------------------------------------- LOADALL_286 proc far ;--------------------------------------------------------------- PUSH DS ; Setup the stack to XOR AX,AX ; return to DOS PUSH AX MOV AX,_Data MOV DS,AX MOV ES,AX ;--------------------------------------------------------------- ; Check CPU type, and set up a minimal invalid opcode handler ; in case LOADALL has been removed from the CPU mask. ;--------------------------------------------------------------- IFE USE_386 Call CPU_Type ; 286, 386? cmp ax,2 ; 286? je short @F ; yep Print_String LF Print_String Not_286 retf ; go split @@: enter 4,0 ; create stack frame mov word ptr INT6,offset INT6_handler mov INT6[2],cs call set_INT6_vector ; set our INT6 handler ENDIF cli Call Save_State ; Save the current CPU Print_String LF ; state Print_String Test_1 ;--------------------------------------------------------------- ; ; TEST1: Real mode ; Test general purpose registers ; Test Segment registers ; Test Descriptor cache base address ; ; (1) Setup LOADALL structures, and pointers ; (2) Execute LOADALL ; (3) Verify results of the test ; ;--------------------------------------------------------------- mov ax,cs ; Prepare 24-bit mov es,ax ; physical address that mov si,0 ; is put in the LOADALL call Calc_pm_address ; descriptor cache mov Loadall_tbl.CS_Desc.A15_A00,ax ; entry. mov Loadall_tbl.CS_Desc.A23_A16,dl smsw ax mov Loadall_tbl._Msw,ax mov Loadall_tbl._Ip,offset Verify_State mov word ptr cs:stack_ptr,sp ; save SS:SP mov word ptr cs:stack_ptr[2],ss LOADALL ; If LOADALL is removed nop ; from the CPU mask, Print_String failed ; then fall through Print_String Rmvd ; to here. Loadall_RET: call Restore_state IFE USE_386 call set_INT6_vector ; set our INT6 handler leave ENDIF retf ;--------------------------------------------------------------- Verify_State: ; Verify that LOADALL worked ;--------------------------------------------------------------- ; This is where we land for the first test of '286 LOADALL. ; The purpose of this test is to verify that all the general ; purpose registers get loaded correctly. Specifically, we are ; testing to verify that all segment registers contain values ; that don't correspond to the memory addresses they appear to ; be pointing to. In other words, we are checking that the ; that the segment registers have one value, while their ; associated hidden descriptor cache registers have different ; values. ;--------------------------------------------------------------- cmp ax,1111h ; Test AX jne @F cmp bx,2222h ; Test BX jne @F cmp cx,3333h ; Test CX jne @F cmp dx,4444h ; Test DX jne @F cmp bp,5555h ; Test BP jne @F cmp di,6666h ; Test DI jne @F cmp si,7777h ; Test SI jne @F cmp sp,8888h ; Test SP jne short @F mov ax,cs ; Test CS cmp ax,1111h jne short @F mov ax,ds ; Test DS cmp ax,2222h jne short @F mov ax,es ; Test ES cmp ax,3333h jne short @F mov ax,ss ; Test SS cmp ax,4444h jne short @F cmp word ptr ds:[0],0202h ; Test DS Desc Cache jne short @F cmp word ptr es:[0],0303h ; Test ES Desc Cache jne short @F cmp word ptr ss:[0],0404h ; Test SS Desc Cache jne short @F mov ax,_Data mov ds,ax mov es,ax mov ax,cs:stack_ptr[2] mov ss,ax mov sp,cs:stack_ptr FARJMP <@Test1_Pass>,<seg _Text> ;--------------------------------------------------------------- ; Loadall failed the REGISTERs test. ;--------------------------------------------------------------- @@: mov ax,_Data mov ds,ax mov es,ax mov ax,cs:stack_ptr[2] mov ss,ax mov sp,cs:stack_ptr FARJMP <@F>,<seg _Text> @@: Print_String failed Print_String RFail jmp loadall_ret ;--------------------------------------------------------------- ; LOADALL passed ;--------------------------------------------------------------- @Test1_Pass: Print_String passed ;--------------------------------------------------------------- ; ; TEST2: Access extended memory while in real mode. ; ; (1) Enable A20 ; (2) Save contents of extended memory ; (3) Write data pattern in extended memory ; (4) Set IP & ES descriptor cache pointing to extended memory ; (5) LOADALL ; (6) Verify results ; (7) Restore original data in extended memory ; ;---------------------------------------------------------------- Print_String Test_2 Call Enable_Gate20 ; Enable extended memory mov bx,0ffffh ; Point to extended mem. mov ds,bx ; as FFFF:0010 mov si,10h mov di,offset Mem_buffer mov cx,400h / 2 ; 1k data block to test rep movsw ; save extended memory mov ax,5aa5h ; test pattern mov es,bx ; point to extended mem. mov cx,400h / 2 mov di,10h rep stosw ; store pattern in mem. mov ax,_data mov ds,ax mov Loadall_tbl._AX,5aa5h mov Loadall_tbl._CX,400h / 2 mov Loadall_tbl._DI,0h mov Loadall_tbl._SP,sp ; save SP mov Loadall_tbl._IP,offset @F mov Loadall_tbl.ES_Desc.A15_A00,00 mov Loadall_tbl.ES_Desc.A23_A16,10 LOADALL @@: repz scasw ; data match? lahf ; get flags mov bx,_Data mov ds,bx mov cx,0ffffh mov es,cx mov cx,400h / 2 mov si,offset Mem_buffer mov di,10h rep movsw ; restore data mov es,bx mov cx,cs:stack_ptr[2] mov ss,cx FARJMP <@F>,<seg _Text> @@: sahf ; restore flags jz @Test2_Pass PRINT_STRING failed jmp Loadall_RET @Test2_Pass: PRINT_STRING passed ;--------------------------------------------------------------- ; ; TEST3: Test that the Present bit gets loaded w/out exception, ; but when a segment is accessed INT13 get generated. ; ; If LOADALL works even remotely like we think it does, ; then this test will work in REAL MODE! And as this ; test was originally programmed, it did! However, I ; was doing my testing by emulating '286 LOADALL with ; '386 LOADALL, where I could use an ICE for debug ; purposes. The code worked on a '286, but failed on a ; '386! I found that the '386 fails to clear the ; Present bit in the descriptor cache register when a ; segment register is loaded in real mode. This is ; obviously a bug in the '386. Since the CPU is in a ; state that can never be duplicated under any program ; control, except by using LOADALL (Present=0), the bug ; will never be manifested in any production code. As a ; result, I reprogramed this example to use protected ; mode so it would work on both the '286 and '386. ; ; (1) Prepare GDT & IDT descriptor cache registers and ; descriptor tables, & segment selectors ; (2) Set protected mode bit, clear Present bit, set IP ; (3) Save the 8259 masks, set the PM return address, and set ; CMOS shutdown=5 ; (4) LOADALL ; (5) Generate the exception ; (6) Reset ES to a valid segment selector & save results of ; test. ; (7) Reset the CPU, restore 8259 masks, inhibit A20 from the ; CPU bus, restore segment registers to real mode values. ; (8) Verify the results ; ;--------------------------------------------------------------- ; Test Present bit: verify that P=0 in a descriptor cache ; register will, even in REAL MODE, will generate an exception ; 13 when trying to access memory ;--------------------------------------------------------------- Test3: Print_String Test_3 mov ax,_Data mov es,ax mov si,0 call Calc_pm_address mov DSEG2.Base_A15_A00,ax mov DSEG2.Base_A23_A16,dl add ax,offset GDT_286 adc dl,0 mov Loadall_tbl.GDT_Desc.A15_A00,ax mov Loadall_tbl.GDT_Desc.A23_A16,dl mov Loadall_tbl.GDT_Desc._Limit,GDT2_Len-1 mov si,offset IDT_286 call Calc_pm_address mov Loadall_tbl.IDT_Desc.A15_A00,ax mov Loadall_tbl.IDT_Desc.A23_A16,dl mov Loadall_tbl.IDT_Desc._Limit,IDT2_Len-1 mov ax,_TEXT mov es,ax mov si,0 call Calc_pm_address mov CSEG2.Base_A15_A00,ax mov CSEG2.Base_A23_A16,dl mov Loadall_tbl._CS,CSEG2-GDT_286 or Loadall_tbl._MSW,1 and Loadall_tbl.ES_Desc._Type,7fh ; Clear P bit mov Loadall_tbl._IP,offset @PM_286 ; Set IP Call Get_INT_Status ; save PIC masks mov ax,offset @RM_286 ; save real mode return Call SetPM_RET_addr ; address Call Set_shutdown_type ; set shutdown in CMOS LOADALL @PM_286:mov al,es:[di][2] mov ax,DSEG2-GDT_286 mov es,ax mov ES:Results,di jmp RESET_CPU @RM_286:mov ax,cs:stack_ptr[2] mov ss,ax mov sp,cs:stack_ptr mov ax,_Data mov ds,ax mov es,ax call Set_INT_Status call Shut_A20 mov di,Results ; If an exception 13 was test di,1 ; generated, then the jnz @F ; low bit of DI is set Print_String failed ; Test failed jmp Loadall_RET @@: Print_String passed ; Test passed jmp Loadall_RET LOADALL_286 endp ;--------------------------------------------------------------- ; Minimal exception 13 handler that points past a 4-byte opcode, ; and sets the lowest bit in DI before returning. ;--------------------------------------------------------------- INT13 label word push bp mov bp,sp add word ptr [bp][4],4 or di,1 pop bp add sp,2 iret ;--------------------------------------------------------------- ; Equates & local variables ;--------------------------------------------------------------- ; I/O Ports ;--------------------------------------------------------------- Mstrmsk equ 021h ; 8259 master mask addr KBC_CTL equ 060h ; 8042 control port KBC_STAT equ 064h ; 8042 status port Cmos_index equ 070h ; CMOS address port Cmos_data equ 071h ; CMOS data port Slv_msk equ 0a1h ; 8259 slave mask addr ;--------------------------------------------------------------- ; CMOS RAM ;--------------------------------------------------------------- Shut_down equ 00fh ; CMOS index for shutdwn Type5 equ 5 ; Shutdown type-5 ;--------------------------------------------------------------- ; Keyboard Controller ;--------------------------------------------------------------- inpt_buf_full equ 2 ; Input buffer full Shutdown_CMD equ 0feh ; Shutdown CMD for KBC enable_bit20 equ 0dfh ; enable A20 command disable_bit20 equ 0ddh ; disable A20 command ;---------------------------------------------------------------; RESET_CPU:; Resets the CPU by sending a shutdown command to ; the keyboard controller. ;--------------------------------------------------------------- ; Input: None ; Output: None ; Register(s) modified: Doesn't matter, the CPU is reset ;--------------------------------------------------------------- mov al,Shutdown_CMD ; get shutdown command out KBC_STAT,al ; send command to shutdown CPU cli ; disable interrupts so that ; an INT can't come through ; before the CPU resets hlt ; ;---------------------------------------------------------------; ; SETPM_RET_ADDR: Save the real-mode return address @ 40:67 ; from protected mode. ;--------------------------------------------------------------- ; Input: CS:AX = Return address from PM. ; DS = Better darn well have a PM segment selector! ; (Or else Kablooie!) ; Output: None ; Register(s) modified: None ;--------------------------------------------------------------- Setpm_ret_addr proc near ;--------------------------------------------------------------- push dx ; save it push ds mov dx,ABS0 ; mov ds,dx ASSUME DS:ABS0 mov DS:PM_Ret_off,ax mov DS:PM_Ret_seg,cs ASSUME DS:_DATA pop ds pop dx ret Setpm_ret_addr endp ;--------------------------------------------------------------- ; Get_INT_status: Saves the master and slave mask register ; contents from the 8259 interrupt controller. ;--------------------------------------------------------------- ; Input: DS = _DATA SEGMENT ; Output: i8259_1 = Status of master device ; i8259_2 = Status of slave device ; Register(s) modified: None ;--------------------------------------------------------------- Get_int_status proc near ;--------------------------------------------------------------- push ax in al,mstrmsk ; get master PIC mask mov i8259_1,al IO_Delay ; I/O delay in al,slv_msk ; get slave PIC mask mov i8259_2,al pop ax ret ; exit Get_int_status endp ;---------------------------------------------------------------; ; Set_INT_status: Restores the interrupt status of the 8259A ; programmable interrupt controller (PIC). ;--------------------------------------------------------------- ; Input: i8259_1 = Status of master device ; i8259_2 = Status of slave device ; DS = _DATA SEGMENT ; Output: None ; Register(s) modified: None ;--------------------------------------------------------------- Set_int_status proc near ;--------------------------------------------------------------- pushf ; save interrupt flag cli ; we REALLY don't want an int ; to come through while we are push ax ; reprogramming the PIC masks mov al,i8259_1 out mstrmsk,al ; restore master PIC mask IO_Delay ; I/O delay mov al,i8259_2 out slv_msk,al ; restore slave PIC mask pop ax popf ; restore interrupt flag ret ; exit Set_int_status endp ;--------------------------------------------------------------- ; SET_SHUTDOWN_TYPE: Set the processor shutdown type-5 in CMOS. ;--------------------------------------------------------------- ; Input: None ; Output: None ; Register(s) modified: None ;--------------------------------------------------------------- Set_shutdown_type proc near ;--------------------------------------------------------------- pushf ; save interrupt status cli ; disable ints so somebody else ; doesn't do this right now push ax mov al,shut_down ; Set shutdown byte out cmos_index,al ; to shut down x05. IO_Delay ; I/O delay mov al,Type5 ; out cmos_data,al ; CMOS data port pop ax popf ret set_shutdown_type endp ;--------------------------------------------------------------- ; Enable_gate20: Turn on A20, and check for errors. ;--------------------------------------------------------------- ; Input: None ; Output: CY=ERROR ; Register(s) modified: None ;--------------------------------------------------------------- Enable_gate20 proc near ;--------------------------------------------------------------- push ax mov ah,enable_bit20 ; gate address bit 20 on Call Gate_A20 or al,al ; command accepted? jz A20_OK ; go if yes stc ; set error flag A20_OK: pop ax ret ; exit Enable_gate20 endp ;--------------------------------------------------------------- ; SHUT_A20: Disable A20 from CPU address BUS. ;--------------------------------------------------------------- ; Input: None ; Output: CY=ERROR ; Register(s) modified: None ;--------------------------------------------------------------- Shut_a20 proc near ;--------------------------------------------------------------- push ax mov ah,disable_bit20 ; gate address bit 20 on Call Gate_A20 or al,al ; was command accepted? jz A20_Shut ; go if yes stc ; set error flag A20_Shut: pop ax ret ; exit Shut_a20 endp ;--------------------------------------------------------------- ; GATE_A20: This routine controls a signal which gates address ; line 20 (A20). The gate A20 signal is an output of ; of the 8042 slave processor (keyboard controller). ; A20 should be gated on before entering protected ; mode, to allow addressing of the entire 16M address ; space of the 80286, or 4G address space of the ; 80386 & 80486. It should be gated off after ; entering real mode -- from protected mode. ;--------------------------------------------------------------- ; Input: AH = DD ==> A20 gated off (A20 always 0) ; AH = DF ==> A20 gated on (CPU controls A20) ; Output: AL = 0 ==> Operation successful ; AL = 2 ==> Operation failed, 8042 can't accept cmd ; Register(s) modified: AX ;--------------------------------------------------------------- Gate_a20 proc near ;--------------------------------------------------------------- pushf ; save interrupt status cli ; disable ints while using 8042 Call Empty_8042 ; insure 8042 input buffer empty jnz A20_Fail ; ret: 8042 unable to accept cmd IO_Delay ; I/O Delay mov al,0D1h ; 8042 cmd to write output port out KBC_STAT,al ; output cmd to 8042 Call Empty_8042 ; wait for 8042 to accept cmd jnz A20_Fail ; ret: 8042 unable to accept cmd mov al,ah ; 8042 port data out KBC_CTL,al ; output port data to 8042 Call Empty_8042 ; wait for 8042 to port data push cx ; save it mov cx,14h ; @DLY: IO_Delay ; Wait for KBC to execute the loop @DLY ; command. (about 25uS) pop cx ; restore it A20_Fail: popf ; restore flags ret Gate_a20 endp ;--------------------------------------------------------------- ; EMPTY_8042: This routine waits for the 8042 buffer to empty. ;--------------------------------------------------------------- ; Input: None ; Output: AL = 0, 8042 input buffer empty: ZF ; AL = 2, Time out; 8042 buffer full: NZ ; Register(s) modified: AX ;--------------------------------------------------------------- Empty_8042 proc near ;--------------------------------------------------------------- push cx ; save CX xor cx,cx ; CX=0: timeout value Try_KBC: IO_Delay ; in al,KBC_STAT ; read 8042 status port and al,inpt_buf_full; input buffer full flag (D1) loopnz Try_KBC ; loop until input buffer empty ; or timeout pop cx ; restore CX ret Empty_8042 endp ;--------------------------------------------------------------- ; CALC_PM_ADDRESS: Calculate 32-bit protected mode address. ; Used for building descriptor tables. ;--------------------------------------------------------------- ; Input: ES:SI = Real mode address ; Output: DX:AX = 32-bit linear address ; Register(s) modified: AX, DX ;--------------------------------------------------------------- Calc_pm_address proc near ;--------------------------------------------------------------- mov ax,es ; point to control block xor dh,dh ; clear upper register mov dl,ah ; build high byte of 32-bit addr shr dl,4 ; use only high nibble from (AX) shl ax,4 ; strip high nibble from segment add ax,si ; add GDT offset for low word adc dx,0 ; adj high byte if CY from low ret ; back to calling program calc_pm_address endp ;--------------------------------------------------------------- Save_state proc near ; Save the machine state before ; ; LOADALL ;--------------------------------------------------------------- push ax push ds mov si,0 mov di,offset Machine_State.ES_Desc mov ax,3000h ; ES descriptor mov ds,ax mov bx,0303h movsw mov word ptr [si-2],bx add ax,1000h ; SS descriptor add bx,0101h mov si,0 add di,0ah mov ds,ax movsw mov word ptr [si-2],bx sub ax,2000h ; DS descriptor sub bx,0202h mov si,0 add di,4 mov ds,ax movsw mov word ptr [si-2],bx pop ds smsw ax mov Machine_State._Msw,ax pushf pop ax mov Machine_State._Flags,ax pop ax mov Machine_State._DI,di mov Machine_State._SI,si mov Machine_State._BP,bp mov Machine_State._BX,bx mov Machine_State._DX,dx mov Machine_State._CX,cx mov Machine_State._AX,ax mov ax,ds mov Machine_State._DS,ax mov ax,es mov Machine_State._ES,ax ret Save_state endp ;--------------------------------------------------------------- Restore_state proc near ; Restore the machine state ; ; after LOADALL ;--------------------------------------------------------------- mov ax,_data mov ds,ax mov ax,3000h ; ES mov es,ax mov si,offset Machine_State.DS_Desc mov di,0 movsw add ax,1000h ; SS add si,0ah mov di,0 mov es,ax movsw sub ax,2000h ; DS add si,4 mov di,0 mov es,ax movsw mov ax,Machine_State._ES mov es,ax mov ax,Machine_State._DS mov ds,ax mov ax,Machine_State._Flags push ax popf mov ax,Machine_State._Msw lmsw ax mov ax,Machine_State._AX mov cx,Machine_State._CX mov dx,Machine_State._DX mov bx,Machine_State._BX mov bp,Machine_State._BP mov si,Machine_State._SI mov di,Machine_State._DI ret Restore_State endp IFE USE_386 ;--------------------------------------------------------------- ; Include the CPU_TYPE procedure & LOADALL test ;--------------------------------------------------------------- Include CPU_TYPE.ASM ENDIF _text ends stack segment para stack 'stack' db 400h dup (0) stack ends end LOADALL_286