0,0 → 1,181 |
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#include <i86.h> |
#include <string.h> |
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#include "env.h" |
#include "helpers.h" |
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#include "rmod.h" |
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#include "rmodinit.h" |
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/* 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; |
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/* 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 |
} |
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/* 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; |
} |
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_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 |
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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 |
} |
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if (rmodseg == 0xffff) { |
outputnl("malloc error"); |
return(0xffff); |
} |
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/* copy rmod to its destination */ |
myptr = MK_FP(rmodseg, 0); |
_fmemcpy(myptr, rmod, rmod_len); |
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/* mark rmod memory as "self owned" */ |
mcb = MK_FP(rmodseg - 1, 0); |
owner = (void far *)(mcb + 1); |
*owner = rmodseg; |
_fmemcpy(mcb + 8, "SVARCOM", 8); |
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/* mark env memory as "self owned" */ |
mcb = MK_FP(envseg - 1, 0); |
owner = (void far *)(mcb + 1); |
*owner = rmodseg; |
_fmemcpy(mcb + 8, "SVARENV", 8); |
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/* write env segment to rmod buffer */ |
owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG); |
*owner = envseg; |
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/* 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 |
} |
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/* 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 |
} |
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return(rmodseg); |
} |
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/* 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; |
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/* 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); |
} |
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/* 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; |
} |
} |