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/* This file is part of the SvarCOM project and is published under the terms |
* of the MIT license. |
* |
* Copyright (C) 2021 Mateusz Viste |
* |
* Permission is hereby granted, free of charge, to any person obtaining a |
* copy of this software and associated documentation files (the "Software"), |
* to deal in the Software without restriction, including without limitation |
* the rights to use, copy, modify, merge, publish, distribute, sublicense, |
* and/or sell copies of the Software, and to permit persons to whom the |
* Software is furnished to do so, subject to the following conditions: |
* |
* The above copyright notice and this permission notice shall be included in |
* all copies or substantial portions of the Software. |
* |
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
* DEALINGS IN THE SOFTWARE. |
*/ |
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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 "rmodinit.h" |
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/* returns far pointer to rmod's settings block on success */ |
struct rmod_props far *rmod_install(unsigned short envsize, unsigned char *rmodcore, unsigned short rmodcore_len) { |
char far *myptr, far *mcb; |
unsigned short far *owner; |
const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16; |
unsigned short rmodseg = 0xffff; |
unsigned short envseg, origenvseg; |
struct rmod_props far *res; |
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/* read my current env segment from PSP and save it */ |
envseg = *((unsigned short *)0x2c); |
origenvseg = envseg; |
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/* printf("original (PSP) env buffer at %04X\r\n", envseg); */ |
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/* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */ |
if ((envseg == 0) && (envsize == 0)) envsize = 256; |
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/* 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, sizeof_rmodandprops_paras |
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(NULL); |
} |
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/* copy rmod to its destination, prefixed with a copy of my own PSP */ |
myptr = MK_FP(rmodseg, 0); |
{ |
unsigned short i; |
char *mypsp = (void *)0; |
for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i]; |
} |
myptr = MK_FP(rmodseg, 0x100); |
_fmemcpy(myptr, rmodcore, rmodcore_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 "owned by rmod" */ |
mcb = MK_FP(envseg - 1, 0); |
owner = (void far *)(mcb + 1); |
*owner = rmodseg; |
_fmemcpy(mcb + 8, "SVARENV", 8); |
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/* if env block is newly allocated, fill it with a few NULLs */ |
if (envsize != 0) { |
owner = MK_FP(envseg, 0); |
owner[0] = 0; |
owner[1] = 0; |
} |
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/* set CTRL+BREAK handler to rmod */ |
_asm { |
push ax |
push dx |
push ds |
mov ax, 0x2523 |
mov ds, rmodseg |
mov dx, RMOD_OFFSET_BRKHANDLER |
int 0x21 |
pop ds |
pop dx |
pop ax |
} |
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/* prepare result (rmod props) */ |
res = MK_FP(rmodseg, 0x100 + rmodcore_len); |
_fmemset(res, 0, sizeof(*res)); /* zero out */ |
res->rmodseg = rmodseg; /* rmod segment */ |
res->inputbuf[0] = 128; /* input buffer for INT 0x21, AH=0Ah*/ |
res->origenvseg = origenvseg; /* original environment segment */ |
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/* write env segment to rmod's PSP */ |
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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/* save my original parent in rmod's memory */ |
res->origparent = *((unsigned long *)0x0a); /* original parent seg:off is at 0x0a of my PSP */ |
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/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I |
* terminate and save the original handler in rmod's memory */ |
{ |
unsigned short *ptr = (void *)0x0a; /* int22 handler is at 0x0A of the PSP */ |
ptr[0] = RMOD_OFFSET_ROUTINE; |
ptr[1] = rmodseg; |
} |
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return(res); |
} |
|
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/* look up my parent: if it's rmod then return a ptr to its props struct, |
* otherwise return NULL */ |
struct rmod_props far *rmod_find(unsigned short rmodcore_len) { |
unsigned short *parent = (void *)0x0C; /* parent's seg in PSP[Ch] ("prev. int22 handler") */ |
unsigned short far *ptr; |
const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019}; |
unsigned char *cmdtail = (void *)0x80; |
unsigned char i; |
/* is it rmod? */ |
ptr = MK_FP(*parent, 0x100); |
for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL); |
/* match successfull (rmod is my parent) - but is it really a respawn? |
* command-line tail should contain a single character '\r' */ |
if ((cmdtail[0] != 1) || (cmdtail[1] != '\n')) return(NULL); |
cmdtail[0] = 0; |
cmdtail[1] = '\r'; |
/* */ |
return(MK_FP(*parent, 0x100 + rmodcore_len)); |
} |
|
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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_val(env_seg, "COMSPEC"); |
if (comspecfp != NULL) { |
*comspecptr = FP_OFF(comspecfp); |
} else { |
*comspecptr = 0; |
} |
} |