The IBM Personal Computer MACRO Assembler 12-20-86 PAGE 1-1 1 PAGE 54,130 2 ; CSYSINT - Lattice "C" interface to the world 3 ; 4 ; This program was adapted from PSYSINT, a program listed 5 ; and described by Will Fastie in SOFTALK Magazine, which 6 ; provided access to system calls from IBM Pascal programs. 7 ; It in turn was taken from George Eberhart's version for the 8 ; Computer Inovations C86 Compiler, with permission. 9 ; 10 ; Modified by T. Cox to match the Microsoft C Compiler 11 ; assembly language interface call conventions, and renamed 12 ; to CSYSINT. 13 ; 14 ; C calling sequence: 15 ; 16 ; flags = csysint(interrupt,&sreg,&rreg); 17 ; 18 ; Where sreg and rreg are structures of four words each representing 19 ; the 8088 registers AX, BX, CX, and DX. "regsetT is a structure 20 ; defining these as all the half-register names (e.g.,AL,AH). 21 ; 22 ; interrupt is the number of the system interrupt desired. 23 ; 24 ; The return value is a 16-bit unsigned integer. It contains 25 ; the machine status register. 26 ; 27 ; This C function calling sequence passes the interrupt code as a value 28 ; and the two register sets as pointers to their respective structures. 29 ; 30 ; The incoming stack looks like this in memory locations "mem". Note 31 ; that the call is a NEAR call (page 1-36 of the Microsoft C manual), 32 ; so only the return address (and not the segment address) is pushed. 33 ; 34 ; High <-- Caller's BP 35 ; mem + 06: interrupt code value 36 ; mem + 04: SREG address 37 ; mem + 02: RREG address 38 ; mem + 00: caller's saved BP 39 ; Low <-- BP, SP 40 ; 41 PGROUP GROUP PROG 42 PARAMS STRUC 43 0000 ???? OLD_BP DW ? ; Caller's BP Save 44 0002 ???? RETN DW ? ; Return address from call 45 0004 ???? ARG1 DW ? ; First arguement 46 0006 ???? ARG2 DW ? ; Second arguement 47 0008 ???? ARG3 DW ? ; Third arguement 48 000A PARAMS ENDS 49 ;  The IBM Personal Computer MACRO Assembler 12-20-86 PAGE 1-2 50 0000 PROG SEGMENT BYTE PUBLIC 'PROG' 51 ASSUME CS:PGROUP 52 PUBLIC CSYSINT 53 ; 54 0000 CSYSINT PROC NEAR 55 0000 55 PUSH BP ; save caller's frame pointer 56 0001 8B EC MOV BP,SP ; set up our frame pointer 57 ; 58 0003 E8 0006 R CALL DUMMY ; trick - push the IP 59 0006 DUMMY: 60 0006 58 POP AX ; get it 61 0007 2D 0006 R SUB AX,OFFSET DUMMY ; calculate the address of the INT 62 000A 05 001A R ADD AX,OFFSET PINT 63 000D 8B F8 MOV DI,AX ; move it to the index register 64 000F 8B 46 04 MOV AX,[BP].ARG1 ; get the desired interrupt number 65 0012 2E: 88 45 01 MOV CS:[DI+1],AL ; put it in the INT instruction 66 0016 E8 0024 R CALL REGSIN ; get the registers from SREG 67 0019 55 PUSH BP ; we'll need our own BP later 68 001A CD 00 PINT: INT 00H ; perform the requested interrupt 69 001C 5D POP BP ; get our BP back 70 001D 9C PUSHF ; hang onto the flags for the return 71 001E E8 0035 R CALL REGSOUT ; put the registers into RREG 72 0021 58 POP AX ; flags are the return value 73 0022 5D POP BP ; restore the caller's frame pointer 74 0023 C3 RET ; return to caller 75 0024 CSYSINT ENDP 76 ; 77 ; --------------------------------- 78 ; Subroutines to move the registers in and out 79 ; 80 = 0004 NRREGS EQU 4 ; this version supports only four regs 81 ; 82 0024 REGSIN PROC NEAR ; -- Move Registers In 83 0024 8B 5E 06 MOV BX,[BP].ARG2 ; get address of register set SREG 84 0027 B9 0004 MOV CX,NRREGS ; ...and how many registers to move 85 002A INLOOP: 86 002A FF 37 PUSH WORD PTR [BX] ; push one 87 002C 43 INC BX ; point to the next one 88 002D 43 INC BX 89 002E E2 FA LOOP INLOOP ; ..do it some more 90 0030 5A POP DX ; now pop them into their proper places 91 0031 59 POP CX 92 0032 5B POP BX 93 0033 58 POP AX 94 0034 C3 RET ; all done 95 0035 REGSIN ENDP 96 ; 97 0035 REGSOUT PROC NEAR ;--Move Registers Out 98 0035 52 PUSH DX ; push all the registers in reverse order  The IBM Personal Computer MACRO Assembler 12-20-86 PAGE 1-3 99 0036 51 PUSH CX 100 0037 53 PUSH BX 101 0038 50 PUSH AX 102 0039 8B 5E 08 MOV BX,[BP].ARG3 ; get the address of RREG 103 003C B9 0004 MOV CX,NRREGS ; ...and how many registers to move 104 003F LOOPOUT: 105 003F 8F 07 POP WORD PTR [BX] ; recover the register 106 0041 43 INC BX ; point to the next 107 0042 43 INC BX 108 0043 E2 FA LOOP LOOPOUT ; do it again 109 0045 C3 RET 110 0046 REGSOUT ENDP 111 ; 112 0046 PROG ENDS 113 END  The IBM Personal Computer MACRO Assembler 12-20-86 PAGE Symbols-1 Structures and records: N a m e Width # fields Shift Width Mask Initial PARAMS . . . . . . . . . . . . . 000A 0005 OLD_BP . . . . . . . . . . . . . 0000 RETN . . . . . . . . . . . . . . 0002 ARG1 . . . . . . . . . . . . . . 0004 ARG2 . . . . . . . . . . . . . . 0006 ARG3 . . . . . . . . . . . . . . 0008 Segments and groups: N a m e Size align combine class PGROUP . . . . . . . . . . . . . GROUP PROG . . . . . . . . . . . . . . 0046 BYTE PUBLIC 'PROG' Symbols: N a m e Type Value Attr CSYSINT. . . . . . . . . . . . . N PROC 0000 PROG Global Length =0024 DUMMY. . . . . . . . . . . . . . L NEAR 0006 PROG INLOOP . . . . . . . . . . . . . L NEAR 002A PROG LOOPOUT. . . . . . . . . . . . . L NEAR 003F PROG NRREGS . . . . . . . . . . . . . Number 0004 PINT . . . . . . . . . . . . . . L NEAR 001A PROG REGSIN . . . . . . . . . . . . . N PROC 0024 PROG Length =0011 REGSOUT. . . . . . . . . . . . . N PROC 0035 PROG Length =0011 Warning Severe Errors Errors 0 0