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mateuszvis |
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/* This file is part of the SvarCOM project and is published under the terms
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* of the MIT license.
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*
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mateusz.vi |
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* Copyright (C) 2021-2022 Mateusz Viste
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mateuszvis |
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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mateuszvis |
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#include <i86.h>
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#include <string.h>
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mateuszvis |
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#include "env.h"
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mateuszvis |
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#include "helpers.h"
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mateuszvis |
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mateuszvis |
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#include "rmodinit.h"
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mateuszvis |
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/* returns far pointer to rmod's settings block on success */
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mateuszvis |
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struct rmod_props far *rmod_install(unsigned short envsize, unsigned char *rmodcore, unsigned short rmodcore_len) {
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mateuszvis |
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char far *myptr, far *mcb;
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unsigned short far *owner;
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mateuszvis |
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const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16;
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mateuszvis |
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unsigned short rmodseg = 0xffff;
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mateuszvis |
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unsigned short envseg, origenvseg;
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mateuszvis |
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struct rmod_props far *res;
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mateuszvis |
42 |
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mateuszvis |
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/* read my current env segment from PSP and save it */
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mateuszvis |
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envseg = *((unsigned short *)0x2c);
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origenvseg = envseg;
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mateuszvis |
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mateuszvis |
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/* printf("original (PSP) env buffer at %04X\r\n", envseg); */
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mateuszvis |
48 |
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/* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */
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if ((envseg == 0) && (envsize == 0)) envsize = 256;
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mateuszvis |
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/* if custom envsize requested, convert it to number of paragraphs */
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if (envsize != 0) {
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envsize += 15;
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envsize /= 16;
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}
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_asm {
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/* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */
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mov ax, 0x5802 /* GET UMB LINK STATE */
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int 0x21
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xor ah, ah
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push ax /* save link state on stack */
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mov ax, 0x5803 /* SET UMB LINK STATE */
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mov bx, 1
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int 0x21
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/* get current allocation strategy and save it in DX */
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mov ax, 0x5800
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int 0x21
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push ax
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pop dx
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/* set strategy to 'last fit, try high then low memory' */
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mov ax, 0x5801
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mov bx, 0x0082
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int 0x21
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/* ask for a memory block and save the given segment to rmodseg */
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mov ah, 0x48
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mateuszvis |
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mov bx, sizeof_rmodandprops_paras
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mateuszvis |
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int 0x21
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jc ALLOC_FAIL
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mov rmodseg, ax
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/* ask for a memory block for the environment and save it to envseg (only if custom size requested) */
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mov bx, envsize
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test bx, bx
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jz ALLOC_FAIL
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mov ah, 0x48
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int 0x21
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jc ALLOC_FAIL
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mov envseg, ax
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ALLOC_FAIL:
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/* restore initial allocation strategy */
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mov ax, 0x5801
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mov bx, dx
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int 0x21
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/* restore initial UMB memory link state */
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mov ax, 0x5803
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pop bx /* pop initial UMB link state from stack */
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int 0x21
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}
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if (rmodseg == 0xffff) {
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mateuszvis |
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outputnl("malloc error");
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mateuszvis |
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return(NULL);
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mateuszvis |
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}
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mateusz.vi |
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/* copy my own PSP where RMOD is about to land, so it has a proper PSP as well */
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/* take care to init the JFT (20 bytes starting at offset 0x18) to 0xff, which
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* essentially means "empty JFT slot" */
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mateuszvis |
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myptr = MK_FP(rmodseg, 0);
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mateuszvis |
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{
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unsigned short i;
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char *mypsp = (void *)0;
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for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];
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mateusz.vi |
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/* for (i = 0x18; i < 0x18+20; i++) myptr[i] = 0xff; */ /* do NOT close file handlers, RMOD's children might need stdin/stdout/etc */
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mateuszvis |
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}
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mateusz.vi |
117 |
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/* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */
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myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */
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myptr[0x17] = rmodseg >> 8;
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121 |
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mateusz.vi |
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/* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31 -- I abuse the PSP's
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mateusz.vi |
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* command line tail as stack, but I do NOT set the stack at the end of the
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mateusz.vi |
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* tail. E. C. Masloch kindly explained why this would be a bad idea:
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*
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* "This is wrong and will potentially overwrite part of your buffers that
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* start past the PSP. This is because the dword [PSP:2Eh] is not used merely
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* to set SS:SP but rather to find the stack frame created by the int 21h
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* call. Therefore the int 21h call that terminates the child process will
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* then pop a number of registers off starting from the address stored in the
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* PSP." <https://github.com/SvarDOS/bugz/issues/38#issuecomment-1817445740>
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*/
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myptr[0x2e] = 192; /* middle of the command line tail area so I have 64 bytes */
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myptr[0x2f] = 0; /* before and 64 bytes in front of me */
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mateusz.vi |
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myptr[0x30] = rmodseg & 0xff;
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myptr[0x31] = rmodseg >> 8;
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/* patch up RMOD's PSP: JFT size @ 0x32-0x33 */
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mateusz.vi |
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myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */
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mateusz.vi |
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myptr[0x33] = 0;
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/* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */
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myptr[0x34] = 0x18; /* the JFT is in the PSP itself */
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myptr[0x35] = 0;
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myptr[0x36] = rmodseg & 0xff;
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myptr[0x37] = rmodseg >> 8;
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/* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */
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myptr[0x38] = 0;
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myptr[0x39] = 0;
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myptr[0x3A] = rmodseg & 0xff;
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myptr[0x3B] = rmodseg >> 8;
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/* copy rmod to its destination (right past the PSP I prepared) */
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mateuszvis |
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myptr = MK_FP(rmodseg, 0x100);
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mateuszvis |
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_fmemcpy(myptr, rmodcore, rmodcore_len);
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mateuszvis |
157 |
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mateusz.vi |
158 |
/* mark rmod memory (MCB) as "self owned" */
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mateuszvis |
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mcb = MK_FP(rmodseg - 1, 0);
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owner = (void far *)(mcb + 1);
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*owner = rmodseg;
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_fmemcpy(mcb + 8, "SVARCOM", 8);
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mateusz.vi |
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/* mark env memory (MCB) as "owned by rmod" */
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mateuszvis |
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mcb = MK_FP(envseg - 1, 0);
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owner = (void far *)(mcb + 1);
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*owner = rmodseg;
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_fmemcpy(mcb + 8, "SVARENV", 8);
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mateuszvis |
169 |
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mateuszvis |
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/* if env block is newly allocated, fill it with a few NULLs */
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if (envsize != 0) {
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owner = MK_FP(envseg, 0);
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owner[0] = 0;
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owner[1] = 0;
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}
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mateuszvis |
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/* set CTRL+BREAK handler to rmod */
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_asm {
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push ax
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push dx
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push ds
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mov ax, 0x2523
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mov ds, rmodseg
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mov dx, RMOD_OFFSET_BRKHANDLER
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int 0x21
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pop ds
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pop dx
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pop ax
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}
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mateusz.vi |
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/* mark the input buffer as empty */
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myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);
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mateusz.vi |
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myptr[0] = 128; /* max acceptable length */
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myptr[1] = 0; /* len of currently stored history string */
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myptr[2] = '\r'; /* string terminator */
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myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */
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myptr[4] = 0xFE; /* 2nd byte of the signature */
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mateusz.vi |
198 |
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mateuszvis |
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/* prepare result (rmod props) */
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mateuszvis |
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res = MK_FP(rmodseg, 0x100 + rmodcore_len);
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mateuszvis |
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_fmemset(res, 0, sizeof(*res)); /* zero out */
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res->rmodseg = rmodseg; /* rmod segment */
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mateuszvis |
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res->origenvseg = origenvseg; /* original environment segment */
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mateuszvis |
204 |
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mateuszvis |
205 |
/* write env segment to rmod's PSP */
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mateuszvis |
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owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);
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*owner = envseg;
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mateuszvis |
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/* write boot drive to rmod bootdrive field */
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_asm {
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push ax
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push bx
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push dx
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push ds
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mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */
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int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */
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add dl, 'A'-1 /* convert to a proper ASCII letter */
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/* set DS to rmodseg */
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mov ax, rmodseg
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mov ds, ax
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/* write boot drive to rmod bootdrive field */
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mov bx, RMOD_OFFSET_BOOTDRIVE
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mov [bx], dl
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pop ds
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pop dx
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pop bx
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pop ax
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}
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mateuszvis |
230 |
/* save my original parent in rmod's memory */
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res->origparent = *((unsigned long *)0x0a); /* original parent seg:off is at 0x0a of my PSP */
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mateuszvis |
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/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I
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* terminate and save the original handler in rmod's memory */
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mateuszvis |
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{
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unsigned short *ptr = (void *)0x0a; /* int22 handler is at 0x0A of the PSP */
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ptr[0] = RMOD_OFFSET_ROUTINE;
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ptr[1] = rmodseg;
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mateuszvis |
239 |
}
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mateuszvis |
241 |
return(res);
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mateuszvis |
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}
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mateuszvis |
245 |
/* look up my parent: if it's rmod then return a ptr to its props struct,
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mateusz.vi |
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* otherwise return NULL
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mateusz.vi |
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* I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */
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mateuszvis |
248 |
struct rmod_props far *rmod_find(unsigned short rmodcore_len) {
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mateusz.vi |
249 |
unsigned short *parent = (void *)0x0C;
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mateuszvis |
250 |
unsigned short far *ptr;
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const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};
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mateuszvis |
252 |
unsigned char *cmdtail = (void *)0x80;
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mateuszvis |
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unsigned char i;
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/* is it rmod? */
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mateuszvis |
255 |
ptr = MK_FP(*parent, 0x100);
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mateuszvis |
256 |
for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);
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mateuszvis |
257 |
/* match successfull (rmod is my parent) - but is it really a respawn?
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* command-line tail should contain a single character '\r' */
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if ((cmdtail[0] != 1) || (cmdtail[1] != '\n')) return(NULL);
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cmdtail[0] = 0;
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cmdtail[1] = '\r';
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/* */
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mateuszvis |
263 |
return(MK_FP(*parent, 0x100 + rmodcore_len));
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mateuszvis |
264 |
}
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mateuszvis |
265 |
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266 |
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267 |
/* update rmod's pointer to comspec */
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268 |
void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {
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269 |
unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);
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mateuszvis |
270 |
char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");
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mateuszvis |
271 |
if (comspecfp != NULL) {
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mateuszvis |
272 |
*comspecptr = FP_OFF(comspecfp);
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mateuszvis |
273 |
} else {
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274 |
*comspecptr = 0;
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275 |
}
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276 |
}
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949 |
mateusz.vi |
277 |
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278 |
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279 |
/* allocates bytes of far memory, flags it as belonging to rmod
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957 |
mateusz.vi |
280 |
* the new block can be optionally flagged as 'ident' (if not null) and zero
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281 |
* out the newly allocated memory.
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949 |
mateusz.vi |
282 |
* returns a far ptr to the allocated block, or NULL on error */
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957 |
mateusz.vi |
283 |
void far *rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char *ident) {
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949 |
mateusz.vi |
284 |
unsigned short far *owner;
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285 |
unsigned short newseg = 0;
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286 |
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287 |
/* ask DOS for a memory block (as high as possible) */
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288 |
_asm {
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289 |
push bx /* save initial value in BX so I can restore it later */
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290 |
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291 |
/* get current allocation strategy and save it on stack */
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292 |
mov ax, 0x5800
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293 |
int 0x21
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294 |
push ax
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295 |
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296 |
/* set strategy to 'last fit, try high then low memory' */
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297 |
mov ax, 0x5801
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298 |
mov bx, 0x0082
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299 |
int 0x21
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300 |
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301 |
/* ask for a memory block and save the given segment to rmodseg */
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302 |
mov ah, 0x48 /* Allocate Memory */
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303 |
mov bx, bytes
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304 |
add bx, 15 /* convert bytes to paragraphs */
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305 |
shr bx, 1 /* bx /= 16 */
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306 |
shr bx, 1
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307 |
shr bx, 1
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308 |
shr bx, 1
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309 |
int 0x21
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310 |
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311 |
/* error handling */
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312 |
jc FAIL
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313 |
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314 |
/* save newly allocated segment to newseg */
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315 |
mov newseg, ax
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316 |
|
|
|
317 |
FAIL:
|
|
|
318 |
/* restore initial allocation strategy */
|
|
|
319 |
mov ax, 0x5801
|
|
|
320 |
pop bx
|
|
|
321 |
int 0x21
|
|
|
322 |
|
|
|
323 |
pop bx /* restore BX to its initial value */
|
|
|
324 |
}
|
|
|
325 |
|
|
|
326 |
if (newseg == 0) return(NULL);
|
|
|
327 |
|
|
|
328 |
/* mark memory as "owned by rmod" */
|
|
|
329 |
owner = (void far *)(MK_FP(newseg - 1, 1));
|
|
|
330 |
*owner = rmod_seg;
|
|
|
331 |
|
|
|
332 |
/* set the MCB description to ident, if provided */
|
|
|
333 |
if (ident) {
|
|
|
334 |
char far *mcbdesc = MK_FP(newseg - 1, 8);
|
|
|
335 |
int i;
|
|
|
336 |
_fmemset(mcbdesc, 0, 8);
|
|
|
337 |
for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */
|
|
|
338 |
mcbdesc[i] = ident[i];
|
|
|
339 |
}
|
|
|
340 |
}
|
|
|
341 |
|
957 |
mateusz.vi |
342 |
/* zero out the memory before handing it out */
|
|
|
343 |
_fmemset(MK_FP(newseg, 0), 0, bytes);
|
|
|
344 |
|
949 |
mateusz.vi |
345 |
return(MK_FP(newseg, 0));
|
|
|
346 |
}
|
|
|
347 |
|
|
|
348 |
|
957 |
mateusz.vi |
349 |
/* free memory previously allocated by rmod_fcalloc() */
|
949 |
mateusz.vi |
350 |
void rmod_ffree(void far *ptr) {
|
|
|
351 |
unsigned short ptrseg;
|
|
|
352 |
unsigned short myseg = 0;
|
|
|
353 |
unsigned short far *owner;
|
|
|
354 |
if (ptr == NULL) return;
|
|
|
355 |
ptrseg = FP_SEG(ptr);
|
|
|
356 |
|
|
|
357 |
/* get my own segment */
|
|
|
358 |
_asm {
|
|
|
359 |
mov myseg, cs
|
|
|
360 |
}
|
|
|
361 |
|
|
|
362 |
/* mark memory in MCB as my own, otherwise DOS might refuse to free it */
|
|
|
363 |
owner = MK_FP(ptrseg - 1, 1);
|
|
|
364 |
*owner = myseg;
|
|
|
365 |
|
|
|
366 |
/* free the memory block */
|
|
|
367 |
_asm {
|
|
|
368 |
push es
|
|
|
369 |
mov ah, 0x49 /* Free Memory Block */
|
|
|
370 |
mov es, ptrseg
|
|
|
371 |
int 0x21
|
|
|
372 |
pop es
|
|
|
373 |
}
|
|
|
374 |
}
|
963 |
mateusz.vi |
375 |
|
|
|
376 |
|
|
|
377 |
/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */
|
|
|
378 |
void rmod_free_bat_llist(struct rmod_props far *rmod) {
|
|
|
379 |
while (rmod->bat != NULL) {
|
|
|
380 |
struct batctx far *victim = rmod->bat;
|
|
|
381 |
rmod->bat = rmod->bat->parent;
|
|
|
382 |
rmod_ffree(victim);
|
|
|
383 |
}
|
|
|
384 |
}
|