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Assembly Source File | 1994-12-28 | 31KB | 1,329 lines

;============================================================================== ;== ;== Project : 286 XMS driver ;== Module name : HM286.ASM (HM286.SYS) ;== Author(s) : Mark E. Huss (meh@bis.adp.com) ;== Purpose : Simplified HIMEM.SYS replacement ;== ;== Created : 11/5/90 ;== ;== Revision history ;== ================ ;== ;============================================================================== ; Notes: ; ; * Some routines (e.g. xms_move_xmem) are NOT re-entrant. ;============================================================================== page 65,132 .286 include xms.inc ;------------------------------------------------------------------------------ ABS0 segment at 0 org 4*15h int_15_vec label dword ABS0 ends ;------------------------------------------------------------------------------ CSEG segment assume cs:CSEG, ds:nothing, es:nothing segorg: ; ; stock device driver header ; dd -1 ; pointer to next device dw 8000h ; character device dw offset strategy dw offset interrupt db 'XMSXXXX0' ; 8 character name ; ; program data ; even req_ptr dd ? old_int_15 dd ? old_int_2f dd ? gate_a20 dw AT_gate_a20 ; else ps2_gate_a20 get_a20 dw test_a20 ; else ps2_get_a20 ftable label word dw xms_get_version ; 0 get XMS version dw xms_request_hma ; 1 request high mem area dw xms_release_hma ; 2 release high mem area dw xms_global_enable_A20 ; 3 global enable a20 dw xms_global_disable_A20 ; 4 global disable a20 dw xms_local_enable_A20 ; 5 local enable a20 dw xms_local_disable_A20 ; 6 local disable a20 dw xms_query_a20 ; 7 query a20 dw xms_query_xmem ; 8 query free extended mem dw xms_alloc_xmem ; 9 alloc extended mem block (EMB) dw xms_free_xmem ; A free EMB dw xms_move_xmem ; B move EMB dw xms_lock_xmem ; C lock EMB dw xms_unlock_xmem ; D unlock EMB dw xms_handle_info ; E get EMB handle info ; ; these are not yet supported ; ; dw xms_bad_fn ; F realloc EMB ; dw xms_bad_fn ; 10 request upper mem block (UMB) ; dw xms_bad_fn ; 11 release UMB ; dw xms_bad_fn ; 12 realloc UMB ftable_end label word ; These fns won't go into the table (and are also not yet supported!) ; 88 Query any free extended memory ; 89 Allocate any Extended Memory Block ; 8E Get extended EMB handle ; 8F Reallocate any Extended Memory ; ; global descriptor table for int 15h block moves ; gdt desc <0,0,0,0,0> base_desc desc <> src_desc desc <> dest_desc desc <> bios_cs desc <> bios_ss desc <> maxaddr dw 0,11h ; starts at 110000 _1024 dw 1024 ; for byte <-> kbyte conversions move_length dw 0 hm_flags db 0 int_mask db 0 .8086 ; could be anything here ;------------------------------------------------------------------------------ strategy proc far mov cs:req_ptr.lsw,bx mov cs:req_ptr.msw,es ret strategy endp ;------------------------------------------------------------------------------ interrupt proc far push ax push cx push dx push bx push si push di push ds push es mov ax,DD_CMD_ERR ; AX = error sub bx,bx ; BX = 0 (assume the worst) lds si,req_ptr cmp [si].cmd,DD_INIT jne int_exit test hm_flags,INIT_DONE jnz int_exit call initialize ; only call once! lds si,req_ptr int_exit: mov [si].stat,ax mov [si].endseg,cs ; END offset = our CS:0000 mov [si].endofs,bx ; 0 or size to keep pop es pop ds pop di pop si pop bx pop dx pop cx pop ax ret interrupt endp ;------------------------------------------------------------------------------ .286 ; processor checked from here on int_15 proc far cmp ah,87h je int_15_move cmp ah,88h je int_15_size jmp old_int_15 int_15_move: mov ah,3 ; 'gate a20 failed' error push bp mov bp,sp or byte ptr [bp+6],CARRY_FLAG jmp int_15_exit int_15_size: sub ax,ax ; indicate 0K free push bp mov bp,sp and byte ptr [bp+6],not CARRY_FLAG int_15_exit: pop bp popf_iret proc near ; popf (for B-step 286 bug) iret popf_iret endp int_15 endp ;------------------------------------------------------------------------------ int_2f proc far cmp ah,43h je do_int2f do_old_2f: jmp old_int_2f do_int2f: cmp al,0 jne try_2f_10 mov al,80h jmp short int_2f_exit try_2f_10: cmp al,10h jne do_old_2f push cs pop es mov bx,offset hm_main int_2f_exit: iret int_2f endp ;------------------------------------------------------------------------------ assume cs:CSEG, ds:CSEG, es:nothing ;------------------------------------------------------------------------------ ; hook_int_15 - ; hook int 15h and clear handle table on 1st non-version call ; ; input: ; output: ; modifies: ; AX, CX, DI, ES ; ; Note: currently MUST preserve BX, DX & SI ;------------------------------------------------------------------------------ hook_int_15 proc near pushf cli ; no ints now sub ax,ax mov es,ax assume es:ABS0 mov ax,int_15_vec.lsw ; get old vector mov old_int_15.lsw,ax mov ax,int_15_vec.msw mov old_int_15.msw,ax ; set our new int 15h vector mov int_15_vec.lsw,offset int_15 mov int_15_vec.msw,cs or hm_flags,INT15_HOOKED @popf ; ints OK sub ax,ax ; init handle table to 00 push cs pop es ; ; hose all but 1st handle to 0 ; mov cx,((MAX_HANDLES-1) * type xms_handle) shr 1 mov di,(offset handle_table - offset segorg) + type xms_handle cld rep stosw ret hook_int_15 endp ;------------------------------------------------------------------------------ ; test_a20 - see if A20 is enabled the hard way ; ; input: ; nil ; output: ; AX = 1 if A20 is enabled, ZF clear ; AX = 0 if A20 is disabled, ZF set ; modifies: ; AX ;------------------------------------------------------------------------------ test_a20 proc near push si push di push ds push es mov ax,0FFFFh mov es,ax ; ES = FFFF inc ax mov ds,ax ; DS = 0000 sub si,si mov di,10h mov cx,100h ; 0000:0000 vs. FFFF:0010 cld rep cmpsw jz ta_off ; ZF set means a20 is off inc ax ; this will keep the ZF cleared ta_off: pop es pop ds pop di pop si ret test_a20 endp ;------------------------------------------------------------------------------ ; kbd_wait - wait for keyboard controller input ready ; ; input: ; nil ; output: ; nil ; modifies: ; AL ;------------------------------------------------------------------------------ kbd_wait proc near push cx sub cx,cx kw_loop: in al,KBD_STATUS test al,KS_INPORT_FULL loopnz kw_loop ; wait 'til input bit is clear pop cx ret kbd_wait endp ;------------------------------------------------------------------------------ ; AT_gate_a20 ; ; input: ; AX = 0 --> disable ; else --> enable ; modifies: ; AX ;------------------------------------------------------------------------------ AT_gate_a20 proc near pushf cli test ax,ax ; in al,KBD_DATA mov al,0DDh jz aga_disable or al,KC_A20_BIT jmp short aga_IO aga_disable: and al,not KC_A20_BIT aga_IO: or al,KC_RESET_BIT ; don't reset the box! mov ah,al call kbd_wait jnz aga_err mov al,KC_WR_OUTPORT out KBD_COMMAND,al call kbd_wait jnz aga_err mov al,ah out KBD_DATA,al call kbd_wait aga_err: @popf ret AT_gate_a20 endp ;------------------------------------------------------------------------------ ; ps2_gate_a20 ; ; input: ; AX = 0 --> disable ; else --> enable ;------------------------------------------------------------------------------ ps2_gate_a20 proc near test ax,ax in al,SYSTEM_CONTROL_PORT_A jz pga_disable ; else fall thru to enable_a20 or al,A20_ENABLE_BIT jmp short port_a_out pga_disable: and al,not A20_ENABLE_BIT port_a_out: out SYSTEM_CONTROL_PORT_A,al ret ps2_gate_a20 endp ;------------------------------------------------------------------------------ ; enable_a20 ; disable_a20 ; ; input: ; nil ; output: ; nil ; modifies: ; AX ;------------------------------------------------------------------------------ enable_a20 proc near mov al,1 jmp gate_a20 enable_a20 endp disable_a20 proc near sub ax,ax jmp gate_a20 disable_a20 endp ;------------------------------------------------------------------------------ ; ps2_get_a20 ; ; input: ; nil ; output: ; AX = 1 if A20 is enabled, ZF clear ; AX = 0 if A20 is disabled, ZF set ; modifies: ; AX ;------------------------------------------------------------------------------ ps2_get_a20 proc near sub ax,ax in al,SYSTEM_CONTROL_PORT_A and al,A20_ENABLE_BIT shr ax,1 ; move bit to LSB & set/clear ZF ret ps2_get_a20 endp ;------------------------------------------------------------------------------ ; segoff_to_physical ; ; input: ; DX:AX = seg:ofs ; output: ; DX:AX = physical 24 bit address (DH = 00) ; modifies: ; AX, CX, DX ;------------------------------------------------------------------------------ segoff_to_physical proc near mov cx,dx sub dx,dx mov dl,ch shr dx,4 ; DX = seg MSD 000x shl cx,4 ; CX = seg 3 LSDs xxx0 add ax,cx ; AX = LSW adc dx,0 ; DX = MSW ret segoff_to_physical endp ;------------------------------------------------------------------------------ ; get_xmove_addr ; ; input: ; ES:BX -> xmem_sub_move struc ; output: ; CF = 0, DX:AX == physical addr ; CF = 1, error ; modifies: ; AX, (BL), DX ;------------------------------------------------------------------------------ get_xmove_addr proc near mov dx,es:[bx].xhandle test dx,dx jnz gxa_do_handle mov ax,es:[bx].xaddr_lo ; handle 0 means seg:ofs ptr mov dx,es:[bx].xaddr_hi call segoff_to_physical jmp gxa_exit gxa_do_handle: call check_handle jc gxa_exit mov ax,[di].xbase mul _1024 ; faster than 32 bit 10 place shift add ax,es:[bx].xaddr_lo adc dx,es:[bx].xaddr_hi gxa_exit: ret get_xmove_addr endp ;------------------------------------------------------------------------------ ; check_addr ; ; input: ; ES:SI -> xmem_move struc ; DX:AX = physical 24 bit address (DH = 00) ; if DEBUG ; CF = 1 -> fail all HIMEM addresses ; CF = 0 -> don't check for HIMEM ; output: ; CF = 0, addr ok ; CF = 1, bad addr ; modifies: ; flags only ;------------------------------------------------------------------------------ check_addr proc near push ax push dx if DEBUG jnc ca_ck_high_side cmp dx,11h ; check for himem stomp jae ca_ck_high_side cmp dx,10h jb ca_addr_ok jae ca_addr_err ca_ck_high_side: endif add ax,es:[si].length_lo adc dx,es:[si].length_hi cmp dx,maxaddr[2] ; check against maxaddr jb ca_addr_ok ja ca_addr_err cmp ax,maxaddr jb ca_addr_ok ca_addr_err: stc jc ca_exit ca_addr_ok: clc ca_exit: pop dx pop ax ret check_addr endp ;------------------------------------------------------------------------------ ; find_free_handle - find an unused handle in the handle_table ; ; input: ; CF = 0 --> first time in ; CF = 1 --> re-entering, adjust DI & CX first ; CX = remaining handle count ; DS:DI = handle to look at ; output: ; CF = 0, DI = handle ; CF = 1, DI = ??? ; modifies: ; CX, DI ;------------------------------------------------------------------------------ find_free_handle proc near jcxz ffh_error_exit ; for safety's sake jc ffh_keep_looking ffh_loop: test [di].xflags,XH_IN_USE ; in use? jnz ffh_keep_looking cmp [di].xbase,0 ; totally free handle? jz ffh_exit ; if true, CF = 0 ffh_keep_looking: add di,type xms_handle loop ffh_loop ffh_error_exit: stc ffh_exit: ret find_free_handle endp ;------------------------------------------------------------------------------ ; find_free_memory - find an unused memory block in the handle table ; ; input: ; CF = 0 --> first time in ; CF = 1 --> re-entering, adjust SI & CX first ; DX = desired memory size ; CX = remaining handle count ; DS:SI = handle to look at ; output: ; CF = 0, SI = handle ; CF = 1, SI = ??? ; modifies: ; CX, SI ;------------------------------------------------------------------------------ find_free_memory proc near jcxz ffm_error_exit ; for safety's sake jc ffm_keep_looking ffm_loop: test [si].xflags,XH_IN_USE jnz ffm_keep_looking cmp [si].xsize,dx jae ffm_exit ; CF = 0 ffm_keep_looking: add si,type xms_handle loop ffm_loop ffm_error_exit: stc ffm_exit: ret find_free_memory endp ;------------------------------------------------------------------------------ ; check_handle ; ; input: ; DX = handle ; output: ; CF = 0, DI = handle ptr ; CF = 1, BL = error code ; modifies: ; DX, DI -- must preserve BX & SI -- ;------------------------------------------------------------------------------ check_handle proc near mov di,dx sub dx,offset handle_table js bad_handle cmp dx,(MAX_HANDLES-1) * type xms_handle ja bad_handle cmp [di].xbase,0 je bad_handle clc ret bad_handle: mov bl,ERR_BAD_XHNDL stc ret check_handle endp ;------------------------------------------------------------------------------ ; ----- XMS functions ----- ;------------------------------------------------------------------------------ ; On entry, SS:[BP] -> register stack frame ; ; All functions return: ; CF=0 --> success, AX = returned AX, BL = returned BL (usually 00) ; CF=1 --> error, AX = don't care, BL = returned error code ;------------------------------------------------------------------------------ ; get XMS version number (function 00h) ;------------------------------------------------------------------------------ xms_get_version proc near mov [bp].r_dx,1 ; HMA exists mov bx,OUR_VERSION mov [bp].r_bx,bx ; BL = returned BL mov ax,XMS_VERSION clc ret xms_get_version endp ;------------------------------------------------------------------------------ ; Request High Memory Area (function 01h) ; Release High Memory Area (function 02h) ;------------------------------------------------------------------------------ xms_request_hma proc near mov bl,ERR_HMA_IN_USE test hm_flags,HMA_IN_USE jnz rhma_error_exit or hm_flags,HMA_IN_USE ; & clc jmp short rhma_good_exit xms_request_hma endp ;---------------------------------- xms_release_hma proc near mov bl,ERR_HMA_NOT_ALLOCATED test hm_flags,HMA_IN_USE jz rhma_error_exit and hm_flags,not HMA_IN_USE ; & clc rhma_good_exit: mov ax,1 mov bl,0 ret rhma_error_exit: stc ret xms_release_hma endp ;------------------------------------------------------------------------------ ; Global/Local Enable A20 (function 03h/05h) ; Global/Local Disable A20 (function 04h/06h) ;------------------------------------------------------------------------------ xms_global_enable_A20 proc near mov bl,ERR_A20_GATE test hm_flags,HMA_IN_USE ; 'global' checks for HMA user jz fa_error_exit xms_local_enable_A20: call enable_a20 jmp short fa_good_exit xms_global_enable_A20 endp ;---------------------------------- xms_global_disable_A20 proc near mov bl,ERR_A20_STILL_ENABLED test hm_flags,HMA_IN_USE jz fa_error_exit xms_local_disable_A20: call disable_a20 fa_good_exit: mov ax,1 mov bl,0 clc ret fa_error_exit: stc ret xms_global_disable_A20 endp ;------------------------------------------------------------------------------ ; Query A20 (function 07h) ;------------------------------------------------------------------------------ xms_query_a20 proc near call get_a20 sub bl,bl ; & clc ret xms_query_a20 endp ;------------------------------------------------------------------------------ ; Query Free Extended Memory (function 08h) ;------------------------------------------------------------------------------ xms_query_xmem proc near sub ax,ax ; AX = largest found sub dx,dx ; find even smallest free block sub di,di ; DI = total ( & clc) mov cx,MAX_HANDLES mov si,offset handle_table qxm_loop: call find_free_memory ; SI = memory handle jc qxm_done add di,[si].xsize ; update total cmp ax,[si].xsize ; update largest ja qxm_mine_is_bigger ; if necessary mov ax,[si].xsize qxm_mine_is_bigger: stc jmp qxm_loop qxm_done: mov [bp].r_dx,di ; return DX = total test ax,ax ; & clc jz qxm_empty mov bl,0 ; AX = largest found ret qxm_empty: mov bl,ERR_OUT_OF_XMEM stc ret xms_query_xmem endp ;------------------------------------------------------------------------------ ; Allocate Extended Memory Block (function 09h) ; DX = block size ;------------------------------------------------------------------------------ xms_alloc_xmem proc near mov cx,MAX_HANDLES mov si,offset handle_table clc ; CF = 0 --> first find_free call find_free_memory ; SI = memory handle jc axm_error_exit ; out of memory mov cx,MAX_HANDLES mov di,offset handle_table ; CF = 0 --> first find_free axm_find_handle: call find_free_handle ; DI = blank handle ; ; if memory handle is last unused handle, give ; requestor all remaining memory ; jc axm_perfect_fit ; ; make sure we have two different handles! ; cmp si,di stc ; CF = 1 --> NOT first find_free je axm_find_handle ; ; found two handles, adjust memory size of memory handle and ; use free handle for left over memory ; axm_normal_alloc: xchg [si].xsize,dx ; set size sub dx,[si].xsize ; DX = left over size jz axm_perfect_fit mov ax,[si].xbase ; old xbase + xsize add ax,[si].xsize ; = new block xbase mov [di].xbase,ax mov [di].xsize,dx ; new block size axm_perfect_fit: or [si].xflags,XH_IN_USE mov [bp].r_dx,si ; handle table offset is handle mov ax,1 sub bl,bl ; & clc ret axm_error_exit: mov bl,ERR_OUT_OF_XHNDL ; this is what HIMEM returns stc ; (even if really 'out of memory') ret xms_alloc_xmem endp ;------------------------------------------------------------------------------ ; Free Extended Memory Block (function 0Ah) ;------------------------------------------------------------------------------ xms_free_xmem proc near call check_handle jc fxm_error_exit cmp [di].xlocks,0 ; make sure its unlocked jne fxm_locked ; ; check for 0 length handle ; mov ax,[di].xsize test ax,ax jnz fxm_len_ok mov [di].xbase,ax ; 0 len, just clear & exit jmp fxm_done ; ; normal handle, check for and concatenate any contiguous free blocks ; fxm_len_ok: add ax,[di].xbase ; AX = freeing handle xbase+size sub dx,dx ; any len 0 & up OK (& CF = 0) ; ; check the high side first ; mov cx,MAX_HANDLES mov si,offset handle_table fxm_loop1: call find_free_memory ; SI = memory handle jc fxm_hi_done ; CF means no more memory handles cmp ax,[si].xbase ; free mem right above us? stc jne fxm_loop1 ; ; found one high, concat ; mov bx,[si].xsize ; add his size add [di].xsize,bx ; to ours mov [si].xbase,dx ; and hose his mov [si].xsize,dx ; fields to 0000 ; ; check the low side next ; fxm_hi_done: mov cx,MAX_HANDLES mov si,offset handle_table clc fxm_loop2: call find_free_memory ; SI = memory handle jc fxm_done ; CF means no more memory handles mov bx,[si].xsize add bx,[si].xbase cmp bx,[di].xbase ; free mem right below us? stc jne fxm_loop2 ; ; found one low, concat ; mov bx,[di].xsize ; add our size add [si].xsize,bx ; to his mov [di].xbase,dx ; and hose our mov [di].xsize,dx ; fields to 0000 fxm_done: and [di].xflags,not XH_IN_USE mov ax,1 sub bl,bl ; & clc ret fxm_locked: mov bl,ERR_BLOCK_LOCKED fxm_error_exit: stc ret xms_free_xmem endp ;------------------------------------------------------------------------------ ; Move Extended Memory Block (function 0Bh) ;------------------------------------------------------------------------------ xms_move_xmem proc near test hm_flags,IN_MOVE ; almost guarantee no re-entrancy jnz xms_move_xmem ; (tiny window of or hm_flags,IN_MOVE ; mis-opportunity here) ; ; check length info ; mov es,[bp].r_ds mov si,[bp].r_si ; ES:SI -> xmove struc mov dx,es:[si].length_hi mov ax,es:[si].length_lo shr dx,1 ; convert byte to word count jnz mxm_len_err ; must be <64K rcr ax,1 jc mxm_len_err ; len must be even cmp ax,8000h ; word count in AX jbe mxm_ok ; must be <= 64K bytes mxm_len_err: mov bl,ERR_BAD_LEN jmp mxm_error_exit mxm_ok: mov move_length,ax ; ; process source info ; lea bx,[si].source_handle call get_xmove_addr mov bl,ERR_BAD_SRC_XHNDL jc mxm_error_exit call check_addr mov bl,ERR_BAD_SRC_OFS jc mxm_error_exit mov src_desc.basel,ax mov src_desc.baseh,dl ; ; process destination info ; lea bx,[si].dest_handle call get_xmove_addr mov bl,ERR_BAD_DEST_XHNDL jc mxm_error_exit if DEBUG stc ; check HIMEM area too endif call check_addr mov bl,ERR_BAD_DEST_OFS jc mxm_error_exit mov dest_desc.basel,ax mov dest_desc.baseh,dl ; ; get machine critical ; pushf cli ; no ints here in al,PIC_MASK ; REALLY no ints here! Rest mov int_mask,al ; save current mask mov al,0FFh out PIC_MASK,al ; mask ALL ints ; ; check A20 state, then do the move ; call get_a20 push ax ; save A20 state mov cx,move_length ; word count from above push cs pop es mov si,offset gdt ; ES:SI --> GDT mov ah,87h ; move block pushf call old_int_15 ; this will disable a20 rcl cl,1 ; save carry pop ax call gate_a20 ; restore a20 cli mov al,int_mask out PIC_MASK,al ; restore int mask @popf ; re-enable ints test cl,1 ; check for int 15 CF jnz mxm_gate_exit mov ax,1 mov bl,0 and hm_flags,not IN_MOVE ; & CLC ret mxm_gate_exit: mov bl,ERR_A20_GATE mxm_error_exit: and hm_flags,not IN_MOVE stc ret xms_move_xmem endp ;------------------------------------------------------------------------------ ; Lock Extended Memory Block (function 0Ch) ;------------------------------------------------------------------------------ xms_lock_xmem proc near call check_handle jc lxm_error_exit mov bl,ERR_OUT_OF_LOCKS inc [di].xlocks jz lxm_lock_wrap mov ax,[di].xbase mul _1024 mov [bp].r_bx,ax ; return base address mov [bp].r_dx,dx ; in DX:BX mov bl,al ; because BL gets returned mov ax,1 ; in common exit routine clc ret lxm_lock_wrap: dec [di].xlocks lxm_error_exit: stc ret xms_lock_xmem endp ;------------------------------------------------------------------------------ ; Unlock Extended Memory Block (function 0Dh) ;------------------------------------------------------------------------------ xms_unlock_xmem proc near call check_handle jc uxm_error_exit mov bl,ERR_BLOCK_NOT_LOCKED cmp [di].xlocks,0 je uxm_error_exit dec [di].xlocks mov ax,1 sub bl,bl ; & clc ret uxm_error_exit: stc ret xms_unlock_xmem endp ;------------------------------------------------------------------------------ ; Get EMB Handle Information (function 0Eh) ;------------------------------------------------------------------------------ xms_handle_info proc near call check_handle jc hi_exit mov ax,[di].xsize mov [bp].r_dx,ax mov bh,[di].xlocks mov cx,MAX_HANDLES mov di,offset handle_table sub bl,bl ; CF = 0 --> first find_free hi_loop: call find_free_handle ; DI = blank handle jc hi_done inc bl ; bump free handle count stc jmp hi_loop hi_done: ; BL = # of free handles mov [bp].r_bx,bx ; (BL = returned BL) mov ax,1 clc hi_exit: ret xms_handle_info endp ;------------------------------------------------------------------------------ ; invalid/unsupported function handler ;------------------------------------------------------------------------------ if 0 xms_bad_fn proc near mov bl,ERR_BAD_FN stc ret xms_bad_fn endp endif ;------------------------------------------------------------------------------ ; main procedure - call far ;------------------------------------------------------------------------------ assume cs:CSEG, ds:nothing, es:nothing hm_main proc far jmp short silly nop nop nop silly: ; goofy recommended start for XMS drivers pusha push ds push es mov bp,sp ; [bp] -> regframe push cs pop ds assume ds:CSEG sub bx,bx mov bl,ah shl bx,1 test bx,bx jz skip_int_15_hook ; init function does not hook int 15 cmp bx,ftable_end - ftable jae hm_bad_fn test hm_flags,INT15_HOOKED ; if not already hooked.. jnz skip_int_15_hook call hook_int_15 ; ..hook int 15h skip_int_15_hook: call ftable[bx] ; dispatch function jc fn_error hm_exit: mov [bp].r_bx.lsb,bl ; always return BL mov [bp].r_ax,ax ; and AX pop es pop ds popa ret ; ; misc. exceptions/errors down here to keep 'normal' flow clean ; hm_bad_fn: mov bl,ERR_BAD_FN fn_error: sub ax,ax ; AX = 0000 jmp hm_exit hm_main endp even handle_table label byte ;============================================================================== ; init code (this is discarded after initialization) ; assume ds:CSEG, es:nothing hello db 13,10,"XMS Driver v ",AVERSION if DEBUG db " (Debug) -- entry point $" endif crlf2 db 13,10,13,10,"$" err_ db "XMS Fatal Error: $" err_re db "An XMS driver is already installed$" err_pta db "Unable to gain control of A20 line$" err_mem db "Insufficent extended memory available$" err_vd db "A VDISK device was detected$" err_cpu db " -- Processor is not an 80286 or better --" crlf db 13,10,"$" vdisk_id db "VDISK" VDISK_ID_LEN equ $ - vdisk_id ;------------------------------------------------------------------------------ if DEBUG htoa4 proc near ; print AX as ASCII hex push ax xchg al,ah call htoa2 pop ax htoa2: push ax REPT 4 shr al,1 ENDM call htoa1 pop ax htoa1: and al,0Fh add al,90h daa adc al,40h daa mov dl,al mov ah,2 int 21h ret htoa4 endp endif ;------------------------------------------------------------------------------ determine_xmemsize proc near mov ah,88h int 15h ; use BIOS - why not jc dx_exit cmp ax,MIN_XMEM jb dx_exit ; CF = 1 sub ax,64 ; reserve HIMEM area ; ; initialize first handle ; mov handle_table.xsize,ax mov handle_table.xbase,XMEM_BASE mov handle_table.xlocks,0 mov handle_table.xflags,0 ; mul _1024 add maxaddr,ax ; max allowed ext addr adc maxaddr[2],dx clc dx_exit: ret determine_xmemsize endp ;------------------------------------------------------------------------------ test_a20_port proc near pushf cli call enable_a20 call test_a20 ; see if its ON jz a20_port_failed call disable_a20 call test_a20 ; see if its OFF jnz a20_port_failed @popf clc ret a20_port_failed: @popf stc ret test_a20_port endp ;------------------------------------------------------------------------------ check_for_vdisk proc near mov ax,3519h int 21h ; get int 19h vector mov di,VDISK_OFS mov si,offset vdisk_id mov cx,VDISK_ID_LEN cld rep cmpsb ; ZF=1 if found jz cfd_found mov ax,0FFFFh ; check FFFF:0013 mov es,ax mov di,VDISK_OFS+1 mov si,offset vdisk_id mov cx,VDISK_ID_LEN cld rep cmpsb ; ZF=1 if found cfd_found: ret check_for_vdisk endp ;------------------------------------------------------------------------------ if 0 ; future expansion get_cmd_line_args proc near push ds ; ; find cmd line params ; lds si,req_ptr les di,dword ptr [si].bpbofs ; cmd line ptr mov bx,di mov cx,80 mov al,13 ; EOL cld repne scasb ; jne error_exit not cx add cx,80 ; CX = count to EOL mov di,bx mov al,'/' repne scasb ; look for separator jne no_params mov al,es:[di] or al,' ' ; tolower cmp al,'x' ; whatever jne no_params ; ( act on params ) no_params: pop ds ret get_cmd_line_args endp endif ;------------------------------------------------------------------------------ ; ; Determine CPU type ; ; Returns: ; AX = 1 -> 8086 (flags MSD always F) ; AX = 2 -> 80286 (flags MSD always 0) ; AX = 3 -> 80386 (flags MSD changable) ; get_cpu proc near mov bx,1 ; assume 8086 pushf ; save original flags pop ax push ax ; AX = original flags and ax,0FFFh ; clear bits 15..12 push ax @popf ; put AX into flags reg pushf pop ax ; AX = modified flags and ax,0F000h ; clear 3 LSDs cmp ax,0F000h je got_cpu_type inc bx ; = 2 (try 286) pop ax push ax ; AX = original flags or ax,0F000h ; try to set bits 15..12 push ax @popf ; put AX into flags reg pushf pop ax ; AX = modified flags and ax,0F000h ; are any MSD bits set? jz got_cpu_type ; if not, its a 286 inc bx ; if so, we have a 386 ( = 3) got_cpu_type: @popf ; restore original flags mov ax,bx ret get_cpu endp ;------------------------------------------------------------------------------ initialize proc near push cs pop ds assume ds:CSEG or hm_flags,INIT_DONE ; indicate init performed @Print hello if DEBUG mov ax,cs call htoa4 mov dl,':' mov ah,2 int 21h mov ax,offset hm_main call htoa4 @Print crlf2 endif mov ax,4300h int 2Fh ; check for re-install cmp al,80h jne no_xms_yet mov dx,offset err_re jmp error_exit no_xms_yet: call check_for_vdisk ; check for VDISK type allocations jnz no_vdisks mov dx,offset err_vd jmp error_exit no_vdisks: call get_cpu ; check for 80286 cmp ax,2 jae cpu_ok mov dx,offset err_cpu jmp warning_exit cpu_ok: call test_a20_port ; make sure our A20 control works jnc port_ok ; AT failed, try ps2 mov gate_a20,offset ps2_gate_a20 mov get_a20,offset ps2_get_a20 call test_a20_port jnc port_ok ; both failed, give up mov dx,offset err_pta jmp error_exit port_ok: call determine_xmemsize ; get available extended memory jnc memsize_ok mov dx,offset err_mem jmp error_exit memsize_ok: ; call get_cmd_line_args mov dx,cs mov ax,offset gdt call segoff_to_physical mov base_desc.basel,ax ; set up base_desc mov base_desc.baseh,dl mov ax,352Fh ; get old int 2f int 21h mov old_int_2f.lsw,bx mov old_int_2f.msw,es mov ax,252Fh ; set new int 2f mov dx,offset int_2f int 21h mov bx,offset handle_table ; calculate size to keep add bx,(MAX_HANDLES * type xms_handle) mov ax,DD_DONE ; tell DOS we're OK ret error_exit: push dx @Print err_ ; print error message pop dx warning_exit: @Print @Print crlf sub bx,bx ; keep offset = 0000 mov ax,DD_ERROR + DD_DONE ; return error ret initialize endp ;------------------------------------------------------------------------------ CSEG ends end