Example Special TSR Handler Stub
COMMENT @ **************************************************************************** * * The following is an example of a service handler (or special TSR). * The timer tick rupt (int 8) is chained into. This simulates an * external triggering event. The handler invokes a service request * for the linked application. The application communicates with * the service handler via a common buffer (and optionally through * the user entry far pointer). * * The service handler is initially loaded by the linked application * via a system manager call ( _m_load_TSR( *filespec) ). * * NOTE: service handlers may also be loaded during system manager startup * * * The service handler must process commands to: * * * link - Associate app with service * unlink - App no longer linked to service request * complete - App has completed service request * hook - Hook service into system (capture rupts) * unhook - Unhook service from system (free rupts) * unload - Unhook service and release memory * **************************************************************************** END COMMENT @ include spectsr.MAC include interfac.mac include event.mac include sysdefs.hhh BREAKPOINT MACRO INT 3 ENDM _TEXT SEGMENT WORD PUBLIC 'CODE' ; Code segment ASSUME cs:_TEXT, ds:_TEXT, ss:_TEXT start: ORG 0 ;All special service handlers must ;be org'd at 0 ;Only field to be inited is the offset to the initialization routine spec_tsr_hdr S_spec_TSR_hdr<init_code,,,,> PUBLIC service_ptr service_ptr dd ? ;Far ptr to allocated service entry PUBLIC global_request global_request dd ? ;Far ptr to sysmgr request flag PUBLIC service_hooked service_hooked db 0 ;Timer rupt hooked indicator PUBLIC call_count call_count dw 0 ;Number of times safe call point PUBLIC timer_rupt timer_rupt dd ? ;Original timer rupt vect PUBLIC timer_count timer_count db 0 ;Count of ticks since last service PERIOD = 10 ;Ticks per service request ;****** Safe call output (not used in this example) *********** db ' APP LOADED BACKGROUND TASK ' TEXT_SIZE EQU $ -offset call_count-2 PUBLIC test_buffer test_buffer db 80h dup('?') ;App - service shared buffer init_code: push cs pop ds push ds pop es BREAKPOINT push ds mov ax,offset global_request ;Get service entry & address push ax ;to global request flag push ds mov ax,offset service_ptr ;Location to store far ptr to push ax ;service entry. mov cx,F_M_GET_SERVICE_ENTRY ;Get a service entry from push cx ;sysmgr. call _c_service add sp,10 cmp ax,0 ;Error? jne error_logic les si,[service_ptr] ;Get pointer to service table ;Set up service structure ;********* Note in this example, the safe call point is not used **** ;Sysmgr safe callback mov word ptr es:[si].SVC_safe_entry,offset safe_call_point mov word ptr es:[si].SVC_safe_entry+2,cs ;********************************************************************** ;Application entry point mov word ptr es:[si].SVC_user_entry,offset user_entry_point mov word ptr es:[si].SVC_user_entry+2,cs mov es:[si].SVC_user_id ,'T' ;Give service a name mov es:[si].SVC_user_id+1,'S' mov es:[si].SVC_user_id+2,'R' mov es:[si].SVC_user_id+3,0 mov al,ds:[bx].TSR_hdr_parent ;Get parent value. mov es:[si].SVC_app_index,al ;Valid if invoked thru app retf ;Return to sysmgr timer_hook: cmp cs:[timer_count],0 ;Have we turned off checks? je @f ;Yes, skip period check inc cs:[timer_count] ;Increment period counter cmp cs:[timer_count],PERIOD ;Have we reached period? jz time_to_set_sema ;Yes, request service @: jmp cs:[timer_rupt] ;Chain to original rupt time_to_set_sema: push ds push si mov cs:[timer_count],0 ;Turn off timer countdown lds si,cs:[service_ptr] ;Get service entry address mov [si].SVC_request,08 ;Set request priority ;Params passed to app thru event structure mov word ptr [si].SVC_user_ptr,offset test_buffer mov word ptr [si].SVC_user_ptr+2,cs xor [si].SVC_user_type,1 ;Set CMD to app lds si,cs:[global_request] ;Get sysmgr global rqst flag mov byte ptr ds:[si],1 ;Set rqst in effect pop si pop ds jmp cs:[timer_rupt] ;Chain to original rupt error_logic: BREAKPOINT ;************** This example does not use this routine ************** safe_call_point: BREAKPOINT push cs pop ds inc [call_count] mov [timer_count],1 mov cx,TEXT_SIZE mov bx,1 mov dx,offset call_count+2 mov ah,40h int 21h retf ;********************************************************************** COMMENT @ ********************************************************************** ********* ********* Application entry point to special service handler ********* ********************************************************************** ********* NOTE: The commands serviced are required for proper system manager operation END COMMENT @ POINTER_PARAM_START equ bp+6 user_entry_point: BREAKPOINT push bp mov bp,sp sub sp,4 push ds push es push si push bx les bx,[POINTER_PARAM_START] mov al,es:[bx] ;Get Service # cmp al,CMD_SERVICE_COMPLETE ;Service complete? jne @f mov cs:[timer_count],1 ;Start another cycle jmp user_exit @: cmp al,CMD_SERVICE_LINK ;New app to be linked? jne @f mov al,es:[bx+1] ;Get new TCB to link with lds si,cs:[service_ptr] mov [si].SVC_app_index,al ;Set new link mov cs:[timer_count],1 ;Start the cycle jmp user_exit @: cmp al,CMD_SERVICE_UNLINK ;New app to be linked? jne @f mov al,es:[bx+1] ;Get new TCB to link with lds si,cs:[service_ptr] mov es:[si].SVC_app_index,0 ;Set no link mov cs:[timer_count],0 ;Turn off processing jmp user_exit @: cmp al,CMD_SERVICE_HOOK ;Establish control? jne @f call hook_timer jc user_bad_result jmp user_exit @: cmp al,CMD_SERVICE_UNHOOK ;Remove rupts? jne @f call unhook_timer jc user_bad_result jmp user_exit @: cmp al,CMD_SERVICE_UNLOAD ;Remove self completely? jne user_bad_result call unhook_timer ;Another prog chained in! jc user_bad_result ;Free service entry push cs mov ax,offset service_ptr push ax mov cx,F_M_FREE_SERVICE_ENTRY push cx call _c_service add sp,6 cmp ax,0 push cs pop ds ;Set ds to self mov ax,offset spec_tsr_hdr.TSR_hdr_init ;Pass ptr to dword push ax mov cx,F_M_FREE_STATIC_BLOCK push cx extrn _c_service:near call _c_service add sp,4 cmp ax,0 jne user_bad_result jmp user_exit user_bad_result: BREAKPOINT mov ax,0ffffh ;Error return jmp user_exitf user_exit: mov ax,0 ;Set ok return user_exitf: pop bx pop si pop es pop ds add sp,4 ;clear auto data pop bp retf ;Hook into the timer interrupt vector PUBLIC hook_timer hook_timer proc push es cmp cs:[service_hooked],1 je @f ;Already hooked mov cs:[service_hooked],1 mov ax,0 mov es,ax mov si,4*8 ;Offset to timer rupt mov ax,es:[si] ;Get original rupt mov word ptr cs:[timer_rupt],ax mov ax,es:[si+2] ;Get original rupt mov word ptr cs:[timer_rupt+2],ax cli mov es:[si],offset timer_hook mov es:[si+2],cs sti @: clc ;Good result pop es ret hook_timer endp PUBLIC unhook_timer unhook_timer proc ;Unhook timer interrupt vector push es cmp cs:[service_hooked],0 ;Has it been hooked? je get_out ;No mov ax,0 mov es,ax mov si,4*8 ;Offset to timer rupt mov ax,word ptr cs:[timer_rupt] mov dx,word ptr cs:[timer_rupt+2] ;Check for other prog hooked after we loaded! cmp es:[si],offset timer_hook jne cant_do mov cx,cs cmp es:[si+2],cx je @f cant_do: stc ;Need to unhook other first! jmp unhook_xit @: cli mov es:[si],ax ;Restore vects mov es:[si+2],dx sti mov cs:[service_hooked],0 ;Set unhooked get_out: clc ;Set success unhook_xit: pop es ret unhook_timer endp _TEXT ENDS END