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421 mateuszvis 1
/* This file is part of the SvarCOM project and is published under the terms
2
 * of the MIT license.
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 *
949 mateusz.vi 4
 * Copyright (C) 2021-2022 Mateusz Viste
421 mateuszvis 5
 *
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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
22
 * DEALINGS IN THE SOFTWARE.
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 */
351 mateuszvis 24
 
25
#include <i86.h>
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#include <string.h>
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367 mateuszvis 28
#include "env.h"
369 mateuszvis 29
#include "helpers.h"
367 mateuszvis 30
 
351 mateuszvis 31
#include "rmodinit.h"
32
 
33
 
449 mateuszvis 34
/* returns far pointer to rmod's settings block on success */
479 mateuszvis 35
struct rmod_props far *rmod_install(unsigned short envsize, unsigned char *rmodcore, unsigned short rmodcore_len) {
351 mateuszvis 36
  char far *myptr, far *mcb;
37
  unsigned short far *owner;
478 mateuszvis 38
  const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16;
453 mateuszvis 39
  unsigned short rmodseg = 0xffff;
454 mateuszvis 40
  unsigned short envseg, origenvseg;
465 mateuszvis 41
  struct rmod_props far *res;
351 mateuszvis 42
 
453 mateuszvis 43
  /* read my current env segment from PSP and save it */
454 mateuszvis 44
  envseg = *((unsigned short *)0x2c);
45
  origenvseg = envseg;
351 mateuszvis 46
 
369 mateuszvis 47
  /* printf("original (PSP) env buffer at %04X\r\n", envseg); */
449 mateuszvis 48
 
49
  /* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */
50
  if ((envseg == 0) && (envsize == 0)) envsize = 256;
51
 
351 mateuszvis 52
  /* if custom envsize requested, convert it to number of paragraphs */
53
  if (envsize != 0) {
54
    envsize += 15;
55
    envsize /= 16;
56
  }
57
 
58
  _asm {
59
    /* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */
60
    mov ax, 0x5802  /* GET UMB LINK STATE */
61
    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
66
    int 0x21
67
    /* get current allocation strategy and save it in DX */
68
    mov ax, 0x5800
69
    int 0x21
70
    push ax
71
    pop dx
72
    /* set strategy to 'last fit, try high then low memory' */
73
    mov ax, 0x5801
74
    mov bx, 0x0082
75
    int 0x21
76
    /* ask for a memory block and save the given segment to rmodseg */
77
    mov ah, 0x48
449 mateuszvis 78
    mov bx, sizeof_rmodandprops_paras
351 mateuszvis 79
    int 0x21
80
    jc ALLOC_FAIL
81
    mov rmodseg, ax
82
    /* ask for a memory block for the environment and save it to envseg (only if custom size requested) */
83
    mov bx, envsize
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    test bx, bx
85
    jz ALLOC_FAIL
86
    mov ah, 0x48
87
    int 0x21
88
    jc ALLOC_FAIL
89
    mov envseg, ax
90
 
91
    ALLOC_FAIL:
92
    /* restore initial allocation strategy */
93
    mov ax, 0x5801
94
    mov bx, dx
95
    int 0x21
96
    /* restore initial UMB memory link state */
97
    mov ax, 0x5803
98
    pop bx       /* pop initial UMB link state from stack */
99
    int 0x21
100
  }
101
 
102
  if (rmodseg == 0xffff) {
369 mateuszvis 103
    outputnl("malloc error");
449 mateuszvis 104
    return(NULL);
351 mateuszvis 105
  }
106
 
459 mateuszvis 107
  /* copy rmod to its destination, prefixed with a copy of my own PSP */
351 mateuszvis 108
  myptr = MK_FP(rmodseg, 0);
459 mateuszvis 109
  {
110
    unsigned short i;
111
    char *mypsp = (void *)0;
112
    for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];
113
  }
114
  myptr = MK_FP(rmodseg, 0x100);
478 mateuszvis 115
  _fmemcpy(myptr, rmodcore, rmodcore_len);
351 mateuszvis 116
 
117
  /* mark rmod memory as "self owned" */
118
  mcb = MK_FP(rmodseg - 1, 0);
119
  owner = (void far *)(mcb + 1);
120
  *owner = rmodseg;
121
  _fmemcpy(mcb + 8, "SVARCOM", 8);
122
 
448 mateuszvis 123
  /* mark env memory as "owned by rmod" */
359 mateuszvis 124
  mcb = MK_FP(envseg - 1, 0);
125
  owner = (void far *)(mcb + 1);
126
  *owner = rmodseg;
127
  _fmemcpy(mcb + 8, "SVARENV", 8);
351 mateuszvis 128
 
449 mateuszvis 129
  /* if env block is newly allocated, fill it with a few NULLs */
130
  if (envsize != 0) {
131
    owner = MK_FP(envseg, 0);
132
    owner[0] = 0;
133
    owner[1] = 0;
134
  }
135
 
537 mateuszvis 136
  /* set CTRL+BREAK handler to rmod */
137
  _asm {
138
    push ax
139
    push dx
140
    push ds
141
    mov ax, 0x2523
142
    mov ds, rmodseg
143
    mov dx, RMOD_OFFSET_BRKHANDLER
144
    int 0x21
145
    pop ds
146
    pop dx
147
    pop ax
148
  }
149
 
449 mateuszvis 150
  /* prepare result (rmod props) */
478 mateuszvis 151
  res = MK_FP(rmodseg, 0x100 + rmodcore_len);
450 mateuszvis 152
  _fmemset(res, 0, sizeof(*res));  /* zero out */
153
  res->rmodseg = rmodseg;          /* rmod segment */
154
  res->inputbuf[0] = 128;          /* input buffer for INT 0x21, AH=0Ah*/
453 mateuszvis 155
  res->origenvseg = origenvseg;    /* original environment segment */
449 mateuszvis 156
 
459 mateuszvis 157
  /* write env segment to rmod's PSP */
351 mateuszvis 158
  owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);
159
  *owner = envseg;
160
 
366 mateuszvis 161
  /* write boot drive to rmod bootdrive field */
162
  _asm {
163
    push ax
164
    push bx
165
    push dx
166
    push ds
167
    mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */
168
    int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */
169
    add dl, 'A'-1 /* convert to a proper ASCII letter */
170
    /* set DS to rmodseg */
171
    mov ax, rmodseg
172
    mov ds, ax
173
    /* write boot drive to rmod bootdrive field */
174
    mov bx, RMOD_OFFSET_BOOTDRIVE
175
    mov [bx], dl
176
    pop ds
177
    pop dx
178
    pop bx
179
    pop ax
180
  }
181
 
450 mateuszvis 182
  /* save my original parent in rmod's memory */
183
  res->origparent = *((unsigned long *)0x0a); /* original parent seg:off is at 0x0a of my PSP */
184
 
448 mateuszvis 185
  /* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I
186
   * terminate and save the original handler in rmod's memory */
454 mateuszvis 187
  {
188
    unsigned short *ptr = (void *)0x0a; /* int22 handler is at 0x0A of the PSP */
189
    ptr[0] = RMOD_OFFSET_ROUTINE;
190
    ptr[1] = rmodseg;
351 mateuszvis 191
  }
192
 
449 mateuszvis 193
  return(res);
351 mateuszvis 194
}
195
 
196
 
449 mateuszvis 197
/* look up my parent: if it's rmod then return a ptr to its props struct,
198
 * otherwise return NULL */
479 mateuszvis 199
struct rmod_props far *rmod_find(unsigned short rmodcore_len) {
448 mateuszvis 200
  unsigned short *parent = (void *)0x0C; /* parent's seg in PSP[Ch] ("prev. int22 handler") */
201
  unsigned short far *ptr;
202
  const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};
465 mateuszvis 203
  unsigned char *cmdtail = (void *)0x80;
448 mateuszvis 204
  unsigned char i;
205
  /* is it rmod? */
459 mateuszvis 206
  ptr = MK_FP(*parent, 0x100);
449 mateuszvis 207
  for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);
465 mateuszvis 208
  /* match successfull (rmod is my parent) - but is it really a respawn?
209
   * command-line tail should contain a single character '\r' */
210
  if ((cmdtail[0] != 1) || (cmdtail[1] != '\n')) return(NULL);
211
  cmdtail[0] = 0;
212
  cmdtail[1] = '\r';
213
  /* */
478 mateuszvis 214
  return(MK_FP(*parent, 0x100 + rmodcore_len));
351 mateuszvis 215
}
367 mateuszvis 216
 
217
 
218
/* update rmod's pointer to comspec */
219
void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {
220
  unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);
439 mateuszvis 221
  char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");
367 mateuszvis 222
  if (comspecfp != NULL) {
439 mateuszvis 223
    *comspecptr = FP_OFF(comspecfp);
367 mateuszvis 224
  } else {
225
    *comspecptr = 0;
226
  }
227
}
949 mateusz.vi 228
 
229
 
230
/* allocates bytes of far memory, flags it as belonging to rmod
957 mateusz.vi 231
 * the new block can be optionally flagged as 'ident' (if not null) and zero
232
 * out the newly allocated memory.
949 mateusz.vi 233
 * returns a far ptr to the allocated block, or NULL on error */
957 mateusz.vi 234
void far *rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char *ident) {
949 mateusz.vi 235
  unsigned short far *owner;
236
  unsigned short newseg = 0;
237
 
238
  /* ask DOS for a memory block (as high as possible) */
239
  _asm {
240
    push bx /* save initial value in BX so I can restore it later */
241
 
242
    /* get current allocation strategy and save it on stack */
243
    mov ax, 0x5800
244
    int 0x21
245
    push ax
246
 
247
    /* set strategy to 'last fit, try high then low memory' */
248
    mov ax, 0x5801
249
    mov bx, 0x0082
250
    int 0x21
251
 
252
    /* ask for a memory block and save the given segment to rmodseg */
253
    mov ah, 0x48  /* Allocate Memory */
254
    mov bx, bytes
255
    add bx, 15    /* convert bytes to paragraphs */
256
    shr bx, 1     /* bx /= 16 */
257
    shr bx, 1
258
    shr bx, 1
259
    shr bx, 1
260
    int 0x21
261
 
262
    /* error handling */
263
    jc FAIL
264
 
265
    /* save newly allocated segment to newseg */
266
    mov newseg, ax
267
 
268
    FAIL:
269
    /* restore initial allocation strategy */
270
    mov ax, 0x5801
271
    pop bx
272
    int 0x21
273
 
274
    pop bx /* restore BX to its initial value */
275
  }
276
 
277
  if (newseg == 0) return(NULL);
278
 
279
  /* mark memory as "owned by rmod" */
280
  owner = (void far *)(MK_FP(newseg - 1, 1));
281
  *owner = rmod_seg;
282
 
283
  /* set the MCB description to ident, if provided */
284
  if (ident) {
285
    char far *mcbdesc = MK_FP(newseg - 1, 8);
286
    int i;
287
    _fmemset(mcbdesc, 0, 8);
288
    for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */
289
      mcbdesc[i] = ident[i];
290
    }
291
  }
292
 
957 mateusz.vi 293
  /* zero out the memory before handing it out */
294
  _fmemset(MK_FP(newseg, 0), 0, bytes);
295
 
949 mateusz.vi 296
  return(MK_FP(newseg, 0));
297
}
298
 
299
 
957 mateusz.vi 300
/* free memory previously allocated by rmod_fcalloc() */
949 mateusz.vi 301
void rmod_ffree(void far *ptr) {
302
  unsigned short ptrseg;
303
  unsigned short myseg = 0;
304
  unsigned short far *owner;
305
  if (ptr == NULL) return;
306
  ptrseg = FP_SEG(ptr);
307
 
308
  /* get my own segment */
309
  _asm {
310
    mov myseg, cs
311
  }
312
 
313
  /* mark memory in MCB as my own, otherwise DOS might refuse to free it */
314
  owner = MK_FP(ptrseg - 1, 1);
315
  *owner = myseg;
316
 
317
  /* free the memory block */
318
  _asm {
319
    push es
320
    mov ah, 0x49  /* Free Memory Block */
321
    mov es, ptrseg
322
    int 0x21
323
    pop es
324
  }
325
}
963 mateusz.vi 326
 
327
 
328
/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */
329
void rmod_free_bat_llist(struct rmod_props far *rmod) {
330
  while (rmod->bat != NULL) {
331
    struct batctx far *victim = rmod->bat;
332
    rmod->bat = rmod->bat->parent;
333
    rmod_ffree(victim);
334
  }
335
}