| 0,0 → 1,181 |
|---|
| |
| #include <i86.h> |
| #include <string.h> |
| |
| #include "env.h" |
| #include "helpers.h" |
| |
| #include "rmod.h" |
| |
| #include "rmodinit.h" |
| |
| |
| /* returns segment where rmod is installed */ |
| unsigned short rmod_install(unsigned short envsize) { |
| char far *myptr, far *mcb; |
| unsigned short far *owner; |
| unsigned int rmodseg = 0xffff; |
| unsigned int envseg = 0; |
| |
| /* read my current env segment from PSP */ |
| _asm { |
| push ax |
| push bx |
| mov bx, 0x2c |
| mov ax, [bx] |
| mov envseg, ax |
| pop bx |
| pop ax |
| } |
| |
| /* printf("original (PSP) env buffer at %04X\r\n", envseg); */ |
| /* if custom envsize requested, convert it to number of paragraphs */ |
| if (envsize != 0) { |
| envsize += 15; |
| envsize /= 16; |
| } |
| |
| |
| _asm { |
| /* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */ |
| mov ax, 0x5802 /* GET UMB LINK STATE */ |
| int 0x21 |
| xor ah, ah |
| push ax /* save link state on stack */ |
| mov ax, 0x5803 /* SET UMB LINK STATE */ |
| mov bx, 1 |
| int 0x21 |
| /* get current allocation strategy and save it in DX */ |
| mov ax, 0x5800 |
| int 0x21 |
| push ax |
| pop dx |
| /* set strategy to 'last fit, try high then low memory' */ |
| mov ax, 0x5801 |
| mov bx, 0x0082 |
| int 0x21 |
| /* ask for a memory block and save the given segment to rmodseg */ |
| mov ah, 0x48 |
| mov bx, (rmod_len + 15) / 16 |
| int 0x21 |
| jc ALLOC_FAIL |
| mov rmodseg, ax |
| /* ask for a memory block for the environment and save it to envseg (only if custom size requested) */ |
| mov bx, envsize |
| test bx, bx |
| jz ALLOC_FAIL |
| mov ah, 0x48 |
| int 0x21 |
| jc ALLOC_FAIL |
| mov envseg, ax |
| |
| ALLOC_FAIL: |
| /* restore initial allocation strategy */ |
| mov ax, 0x5801 |
| mov bx, dx |
| int 0x21 |
| /* restore initial UMB memory link state */ |
| mov ax, 0x5803 |
| pop bx /* pop initial UMB link state from stack */ |
| int 0x21 |
| } |
| |
| if (rmodseg == 0xffff) { |
| outputnl("malloc error"); |
| return(0xffff); |
| } |
| |
| /* copy rmod to its destination */ |
| myptr = MK_FP(rmodseg, 0); |
| _fmemcpy(myptr, rmod, rmod_len); |
| |
| /* mark rmod memory as "self owned" */ |
| mcb = MK_FP(rmodseg - 1, 0); |
| owner = (void far *)(mcb + 1); |
| *owner = rmodseg; |
| _fmemcpy(mcb + 8, "SVARCOM", 8); |
| |
| /* mark env memory as "self owned" */ |
| mcb = MK_FP(envseg - 1, 0); |
| owner = (void far *)(mcb + 1); |
| *owner = rmodseg; |
| _fmemcpy(mcb + 8, "SVARENV", 8); |
| |
| /* write env segment to rmod buffer */ |
| owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG); |
| *owner = envseg; |
| |
| /* write boot drive to rmod bootdrive field */ |
| _asm { |
| push ax |
| push bx |
| push dx |
| push ds |
| mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */ |
| int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */ |
| add dl, 'A'-1 /* convert to a proper ASCII letter */ |
| /* set DS to rmodseg */ |
| mov ax, rmodseg |
| mov ds, ax |
| /* write boot drive to rmod bootdrive field */ |
| mov bx, RMOD_OFFSET_BOOTDRIVE |
| mov [bx], dl |
| pop ds |
| pop dx |
| pop bx |
| pop ax |
| } |
| |
| /* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I terminate */ |
| _asm { |
| push ax |
| push bx |
| mov bx, 0x0a /* int22 handler is at 0x0A of the PSP */ |
| mov ax, RMOD_OFFSET_ROUTINE |
| mov [bx], ax /* int handler offset */ |
| mov ax, rmodseg |
| mov [bx+2], ax /* int handler segment */ |
| pop bx |
| pop ax |
| } |
| |
| return(rmodseg); |
| } |
| |
| |
| /* scan memory for rmod, returns its segment if found, 0xffff otherwise */ |
| unsigned short rmod_find(void) { |
| unsigned short i; |
| unsigned short far *ptrword; |
| unsigned char far *ptrbyte; |
| |
| /* iterate over all paragraphs, looking for my signature */ |
| for (i = 1; i != 65535; i++) { |
| ptrword = MK_FP(i, 0); |
| if (ptrword[0] != 0x1983) continue; |
| if (ptrword[1] != 0x1985) continue; |
| if (ptrword[2] != 0x2017) continue; |
| if (ptrword[3] != 0x2019) continue; |
| /* extra check: make sure the paragraph before is an MCB block and that it |
| * belongs to itself. otherwise I could find the rmod code embedded inside |
| * the command.com binary... */ |
| ptrbyte = MK_FP(i - 1, 0); |
| if ((*ptrbyte != 'M') && (*ptrbyte != 'Z')) continue; /* not an MCB */ |
| ptrword = MK_FP(i - 1, 1); |
| if (*ptrword != i) continue; /* not belonging to self */ |
| return(i); |
| } |
| return(0xffff); |
| } |
| |
| |
| /* update rmod's pointer to comspec */ |
| void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) { |
| unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR); |
| char far *comspecfp = env_lookup(env_seg, "COMSPEC"); |
| if (comspecfp != NULL) { |
| *comspecptr = FP_OFF(comspecfp) + 8; /* +8 to skip the "COMSPEC=" prefix */ |
| } else { |
| *comspecptr = 0; |
| } |
| } |