WebSVN – SvarDOS – Diff – /svarcom/trunk/rmodinit.c


/* This file is part of the SvarCOM project and is published under the terms
 * of the MIT license.
 *
 * Copyright (C) 2021-2022 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.
 */
 
#include <i86.h>
#include <string.h>
 
#include "env.h"
#include "helpers.h"
 
#include "rmodinit.h"
 
 
/* 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;
 
  /* read my current env segment from PSP and save it */
  envseg = *((unsigned short *)0x2c);
  origenvseg = envseg;
 
  /* printf("original (PSP) env buffer at %04X\r\n", envseg); */
 
  /* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */
  if ((envseg == 0) && (envsize == 0)) envsize = 256;
 
  /* if custom envsize requested, convert it to number of paragraphs */
  if (envsize != 0) {
    envsize += 15;
    envsize /= 16;
  }
 
  _asm {
    push bx
    push cx
    push dx
 
    /* 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
 
    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
 
    pop dx
    pop cx
    pop bx
  }
 
  if (rmodseg == 0xffff) {
    outputnl("malloc error");
    return(NULL);
  }
 
  /* generate a new PSP where RMOD is about to land */
  _asm {
    push dx
    mov ah, 0x26 /* CREATE NEW PROGRAM SEGMENT PREFIX (DOS 1+) */
    mov dx, rmodseg
    int 0x21
    pop dx
  }
 
  myptr = MK_FP(rmodseg, 0);
 
  /* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */
  myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */
  myptr[0x17] = rmodseg >> 8;
 
  /* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31  --  I abuse the PSP's
   * command line tail as stack, but I do NOT set the stack at the end of the
   * tail. E. C. Masloch kindly explained why this would be a bad idea:
   *
   * "This is wrong and will potentially overwrite part of your buffers that
   * start past the PSP. This is because the dword [PSP:2Eh] is not used merely
   * to set SS:SP but rather to find the stack frame created by the int 21h
   * call. Therefore the int 21h call that terminates the child process will
   * then pop a number of registers off starting from the address stored in the
   * PSP." <https://github.com/SvarDOS/bugz/issues/38#issuecomment-1817445740>
   */
  myptr[0x2e] = 192; /* middle of the command line tail area so I have 64 bytes */
  myptr[0x2f] = 0;   /* before and 64 bytes in front of me */
  myptr[0x30] = rmodseg & 0xff;
  myptr[0x31] = rmodseg >> 8;
 
  /* patch up RMOD's PSP: JFT size @ 0x32-0x33 */
  myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */
  myptr[0x33] = 0;
 
  /* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */
  myptr[0x34] = 0x18; /* the JFT is in the PSP itself */
  myptr[0x35] = 0;
  myptr[0x36] = rmodseg & 0xff;
  myptr[0x37] = rmodseg >> 8;
 
  /* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */
  myptr[0x38] = 0;
  myptr[0x39] = 0;
  myptr[0x3A] = rmodseg & 0xff;
  myptr[0x3B] = rmodseg >> 8;
 
  /* copy rmod to its destination (right past the PSP I prepared) */
  myptr = MK_FP(rmodseg, 0x100);
  _fmemcpy(myptr, rmodcore, rmodcore_len);
 
  /* mark rmod memory (MCB) as "self owned" */
  mcb = MK_FP(rmodseg - 1, 0);
  owner = (void far *)(mcb + 1);
  *owner = rmodseg;
  _fmemcpy(mcb + 8, "SVARCOM", 8);
 
  /* mark env memory (MCB) as "owned by rmod" */
  mcb = MK_FP(envseg - 1, 0);
  owner = (void far *)(mcb + 1);
  *owner = rmodseg;
  _fmemcpy(mcb + 8, "SVARENV", 8);
 
  /* 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;
  }
 
  /* 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
  }
 
  /* mark the input buffer as empty */
  myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);
  myptr[0] = 128;  /* max acceptable length */
  myptr[1] = 0;    /* len of currently stored history string */
  myptr[2] = '\r'; /* string terminator */
  myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */
  myptr[4] = 0xFE; /* 2nd byte of the signature */
 
  /* prepare result (rmod props) */
  res = MK_FP(rmodseg, 0x100 + rmodcore_len);
  _fmemset(res, 0, sizeof(*res));  /* zero out */
  res->rmodseg = rmodseg;          /* rmod segment */
  res->origenvseg = origenvseg;    /* original environment segment */
 
  /* write env segment to rmod's PSP */
  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
  }
 
  /* save my original parent in rmod's memory */
  res->origparent = *((unsigned long *)0x0a); /* original parent seg:off is at 0x0a of my PSP */
 
  /* 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;
  }
 
  return(res);
}
 
 
/* look up my parent: if it's rmod then return a ptr to its props struct,
 * otherwise return NULL
 * I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */
struct rmod_props far *rmod_find(unsigned short rmodcore_len) {
  unsigned short *parent = (void *)0x0C;
  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));
}
 
 
/* 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;
  }
}
 
 
/* allocates bytes of far memory, flags it as belonging to rmod
 * the new block can be optionally flagged as 'ident' (if not null) and zero
 * out the newly allocated memory.
 * returns a far ptr to the allocated block, or NULL on error */
void far *rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char *ident) {
  unsigned short far *owner;
  unsigned short newseg = 0;
 
  /* ask DOS for a memory block (as high as possible) */
  _asm {
    push bx /* save initial value in BX so I can restore it later */
 
    /* get current allocation strategy and save it on stack */
    mov ax, 0x5800
    int 0x21
    push ax
 
    /* 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  /* Allocate Memory */
    mov bx, bytes
    add bx, 15    /* convert bytes to paragraphs */
    shr bx, 1     /* bx /= 16 */
    shr bx, 1
    shr bx, 1
    shr bx, 1
    int 0x21
 
    /* error handling */
    jc FAIL
 
    /* save newly allocated segment to newseg */
    mov newseg, ax
 
    FAIL:
    /* restore initial allocation strategy */
    mov ax, 0x5801
    pop bx
    int 0x21
 
    pop bx /* restore BX to its initial value */
  }
 
  if (newseg == 0) return(NULL);
 
  /* mark memory as "owned by rmod" */
  owner = (void far *)(MK_FP(newseg - 1, 1));
  *owner = rmod_seg;
 
  /* set the MCB description to ident, if provided */
  if (ident) {
    char far *mcbdesc = MK_FP(newseg - 1, 8);
    int i;
    _fmemset(mcbdesc, 0, 8);
    for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */
      mcbdesc[i] = ident[i];
    }
  }
 
  /* zero out the memory before handing it out */
  _fmemset(MK_FP(newseg, 0), 0, bytes);
 
  return(MK_FP(newseg, 0));
}
 
 
/* free memory previously allocated by rmod_fcalloc() */
void rmod_ffree(void far *ptr) {
  unsigned short ptrseg;
  unsigned short myseg = 0;
  unsigned short far *owner;
  if (ptr == NULL) return;
  ptrseg = FP_SEG(ptr);
 
  /* get my own segment */
  _asm {
    mov myseg, cs
  }
 
  /* mark memory in MCB as my own, otherwise DOS might refuse to free it */
  owner = MK_FP(ptrseg - 1, 1);
  *owner = myseg;
 
  /* free the memory block */
  _asm {
    push es
    mov ah, 0x49  /* Free Memory Block */
    mov es, ptrseg
    int 0x21
    pop es
  }
}
 
 
/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */
void rmod_free_bat_llist(struct rmod_props far *rmod) {
  while (rmod->bat != NULL) {
    struct batctx far *victim = rmod->bat;
    rmod->bat = rmod->bat->parent;
    rmod_ffree(victim);
  }
}
 

Rev 1591	Rev 1594
1	`/* This file is part of the SvarCOM project and is published under the terms`	1	`/* This file is part of the SvarCOM project and is published under the terms`
2	`* of the MIT license.`	2	`* of the MIT license.`
3	`*`	3	`*`
4	`* Copyright (C) 2021-2022 Mateusz Viste`	4	`* Copyright (C) 2021-2022 Mateusz Viste`
5	`*`	5	`*`
6	`* Permission is hereby granted, free of charge, to any person obtaining a`	6	`* Permission is hereby granted, free of charge, to any person obtaining a`
7	`* copy of this software and associated documentation files (the "Software"),`	7	`* copy of this software and associated documentation files (the "Software"),`
8	`* to deal in the Software without restriction, including without limitation`	8	`* to deal in the Software without restriction, including without limitation`
9	`* the rights to use, copy, modify, merge, publish, distribute, sublicense,`	9	`* the rights to use, copy, modify, merge, publish, distribute, sublicense,`
10	`* and/or sell copies of the Software, and to permit persons to whom the`	10	`* and/or sell copies of the Software, and to permit persons to whom the`
11	`* Software is furnished to do so, subject to the following conditions:`	11	`* Software is furnished to do so, subject to the following conditions:`
12	`*`	12	`*`
13	`* The above copyright notice and this permission notice shall be included in`	13	`* The above copyright notice and this permission notice shall be included in`
14	`* all copies or substantial portions of the Software.`	14	`* all copies or substantial portions of the Software.`
15	`*`	15	`*`
16	`* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR`	16	`* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR`
17	`* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,`	17	`* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,`
18	`* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE`	18	`* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE`
19	`* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER`	19	`* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER`
20	`* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING`	20	`* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING`
21	`* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER`	21	`* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER`
22	`* DEALINGS IN THE SOFTWARE.`	22	`* DEALINGS IN THE SOFTWARE.`
23	`*/`	23	`*/`
24		24
25	`#include <i86.h>`	25	`#include <i86.h>`
26	`#include <string.h>`	26	`#include <string.h>`
27		27
28	`#include "env.h"`	28	`#include "env.h"`
29	`#include "helpers.h"`	29	`#include "helpers.h"`
30		30
31	`#include "rmodinit.h"`	31	`#include "rmodinit.h"`
32		32
33		33
34	`/* returns far pointer to rmod's settings block on success */`	34	`/* returns far pointer to rmod's settings block on success */`
35	`struct rmod_props far rmod_install(unsigned short envsize, unsigned char rmodcore, unsigned short rmodcore_len) {`	35	`struct rmod_props far rmod_install(unsigned short envsize, unsigned char rmodcore, unsigned short rmodcore_len) {`
36	`char far myptr, far mcb;`	36	`char far myptr, far mcb;`
37	`unsigned short far *owner;`	37	`unsigned short far *owner;`
38	`const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16;`	38	`const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16;`
39	`unsigned short rmodseg = 0xffff;`	39	`unsigned short rmodseg = 0xffff;`
40	`unsigned short envseg, origenvseg;`	40	`unsigned short envseg, origenvseg;`
41	`struct rmod_props far *res;`	41	`struct rmod_props far *res;`
42		42
43	`/* read my current env segment from PSP and save it */`	43	`/* read my current env segment from PSP and save it */`
44	`envseg = ((unsigned short )0x2c);`	44	`envseg = ((unsigned short )0x2c);`
45	`origenvseg = envseg;`	45	`origenvseg = envseg;`
46		46
47	`/* printf("original (PSP) env buffer at %04X\r\n", envseg); */`	47	`/* printf("original (PSP) env buffer at %04X\r\n", envseg); */`
48		48
49	`/* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */`	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;`	50	`if ((envseg == 0) && (envsize == 0)) envsize = 256;`
51		51
52	`/* if custom envsize requested, convert it to number of paragraphs */`	52	`/* if custom envsize requested, convert it to number of paragraphs */`
53	`if (envsize != 0) {`	53	`if (envsize != 0) {`
54	`envsize += 15;`	54	`envsize += 15;`
55	`envsize /= 16;`	55	`envsize /= 16;`
56	`}`	56	`}`
57		57
58	`_asm {`	58	`_asm {`
-		59	`push bx`
-		60	`push cx`
-		61	`push dx`
-		62
59	`/* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */`	63	`/* 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 */`	64	`mov ax, 0x5802 /* GET UMB LINK STATE */`
61	`int 0x21`	65	`int 0x21`
62	`xor ah, ah`	66	`xor ah, ah`
63	`push ax /* save link state on stack */`	67	`push ax /* save link state on stack */`
64	`mov ax, 0x5803 /* SET UMB LINK STATE */`	68	`mov ax, 0x5803 /* SET UMB LINK STATE */`
65	`mov bx, 1`	69	`mov bx, 1`
66	`int 0x21`	70	`int 0x21`
67	`/* get current allocation strategy and save it in DX */`	71	`/* get current allocation strategy and save it in DX */`
68	`mov ax, 0x5800`	72	`mov ax, 0x5800`
69	`int 0x21`	73	`int 0x21`
70	`push ax`	74	`push ax`
71	`pop dx`	75	`pop dx`
72	`/* set strategy to 'last fit, try high then low memory' */`	76	`/* set strategy to 'last fit, try high then low memory' */`
73	`mov ax, 0x5801`	77	`mov ax, 0x5801`
74	`mov bx, 0x0082`	78	`mov bx, 0x0082`
75	`int 0x21`	79	`int 0x21`
76	`/* ask for a memory block and save the given segment to rmodseg */`	80	`/* ask for a memory block and save the given segment to rmodseg */`
77	`mov ah, 0x48`	81	`mov ah, 0x48`
78	`mov bx, sizeof_rmodandprops_paras`	82	`mov bx, sizeof_rmodandprops_paras`
79	`int 0x21`	83	`int 0x21`
80	`jc ALLOC_FAIL`	84	`jc ALLOC_FAIL`
81	`mov rmodseg, ax`	85	`mov rmodseg, ax`
82	`/* ask for a memory block for the environment and save it to envseg (only if custom size requested) */`	86	`/* ask for a memory block for the environment and save it to envseg (only if custom size requested) */`
83	`mov bx, envsize`	87	`mov bx, envsize`
84	`test bx, bx`	88	`test bx, bx`
85	`jz ALLOC_FAIL`	89	`jz ALLOC_FAIL`
86	`mov ah, 0x48`	90	`mov ah, 0x48`
87	`int 0x21`	91	`int 0x21`
88	`jc ALLOC_FAIL`	92	`jc ALLOC_FAIL`
89	`mov envseg, ax`	93	`mov envseg, ax`
90		94
91	`ALLOC_FAIL:`	95	`ALLOC_FAIL:`
92	`/* restore initial allocation strategy */`	96	`/* restore initial allocation strategy */`
93	`mov ax, 0x5801`	97	`mov ax, 0x5801`
94	`mov bx, dx`	98	`mov bx, dx`
95	`int 0x21`	99	`int 0x21`
96	`/* restore initial UMB memory link state */`	100	`/* restore initial UMB memory link state */`
97	`mov ax, 0x5803`	101	`mov ax, 0x5803`
98	`pop bx /* pop initial UMB link state from stack */`	102	`pop bx /* pop initial UMB link state from stack */`
99	`int 0x21`	103	`int 0x21`
-		104
-		105	`pop dx`
-		106	`pop cx`
-		107	`pop bx`
100	`}`	108	`}`
101		109
102	`if (rmodseg == 0xffff) {`	110	`if (rmodseg == 0xffff) {`
103	`outputnl("malloc error");`	111	`outputnl("malloc error");`
104	`return(NULL);`	112	`return(NULL);`
105	`}`	113	`}`
106		114
107	`/* generate a new PSP where RMOD is about to land */`	115	`/* generate a new PSP where RMOD is about to land */`
108	`_asm {`	116	`_asm {`
109	`push dx`	117	`push dx`
110	`mov ah, 0x26 /* CREATE NEW PROGRAM SEGMENT PREFIX (DOS 1+) */`	118	`mov ah, 0x26 /* CREATE NEW PROGRAM SEGMENT PREFIX (DOS 1+) */`
111	`mov dx, rmodseg`	119	`mov dx, rmodseg`
112	`int 0x21`	120	`int 0x21`
113	`pop dx`	121	`pop dx`
114	`}`	122	`}`
115		123
116	`myptr = MK_FP(rmodseg, 0);`	124	`myptr = MK_FP(rmodseg, 0);`
117		125
118	`/* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */`	126	`/* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */`
119	`myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */`	127	`myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */`
120	`myptr[0x17] = rmodseg >> 8;`	128	`myptr[0x17] = rmodseg >> 8;`
121		129
122	`/* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31 -- I abuse the PSP's`	130	`/* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31 -- I abuse the PSP's`
123	`* command line tail as stack, but I do NOT set the stack at the end of the`	131	`* command line tail as stack, but I do NOT set the stack at the end of the`
124	`* tail. E. C. Masloch kindly explained why this would be a bad idea:`	132	`* tail. E. C. Masloch kindly explained why this would be a bad idea:`
125	`*`	133	`*`
126	`* "This is wrong and will potentially overwrite part of your buffers that`	134	`* "This is wrong and will potentially overwrite part of your buffers that`
127	`* start past the PSP. This is because the dword [PSP:2Eh] is not used merely`	135	`* start past the PSP. This is because the dword [PSP:2Eh] is not used merely`
128	`* to set SS:SP but rather to find the stack frame created by the int 21h`	136	`* to set SS:SP but rather to find the stack frame created by the int 21h`
129	`* call. Therefore the int 21h call that terminates the child process will`	137	`* call. Therefore the int 21h call that terminates the child process will`
130	`* then pop a number of registers off starting from the address stored in the`	138	`* then pop a number of registers off starting from the address stored in the`
131	`* PSP." <https://github.com/SvarDOS/bugz/issues/38#issuecomment-1817445740>`	139	`* PSP." <https://github.com/SvarDOS/bugz/issues/38#issuecomment-1817445740>`
132	`*/`	140	`*/`
133	`myptr[0x2e] = 192; /* middle of the command line tail area so I have 64 bytes */`	141	`myptr[0x2e] = 192; /* middle of the command line tail area so I have 64 bytes */`
134	`myptr[0x2f] = 0; /* before and 64 bytes in front of me */`	142	`myptr[0x2f] = 0; /* before and 64 bytes in front of me */`
135	`myptr[0x30] = rmodseg & 0xff;`	143	`myptr[0x30] = rmodseg & 0xff;`
136	`myptr[0x31] = rmodseg >> 8;`	144	`myptr[0x31] = rmodseg >> 8;`
137		145
138	`/* patch up RMOD's PSP: JFT size @ 0x32-0x33 */`	146	`/* patch up RMOD's PSP: JFT size @ 0x32-0x33 */`
139	`myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */`	147	`myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */`
140	`myptr[0x33] = 0;`	148	`myptr[0x33] = 0;`
141		149
142	`/* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */`	150	`/* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */`
143	`myptr[0x34] = 0x18; /* the JFT is in the PSP itself */`	151	`myptr[0x34] = 0x18; /* the JFT is in the PSP itself */`
144	`myptr[0x35] = 0;`	152	`myptr[0x35] = 0;`
145	`myptr[0x36] = rmodseg & 0xff;`	153	`myptr[0x36] = rmodseg & 0xff;`
146	`myptr[0x37] = rmodseg >> 8;`	154	`myptr[0x37] = rmodseg >> 8;`
147		155
148	`/* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */`	156	`/* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */`
149	`myptr[0x38] = 0;`	157	`myptr[0x38] = 0;`
150	`myptr[0x39] = 0;`	158	`myptr[0x39] = 0;`
151	`myptr[0x3A] = rmodseg & 0xff;`	159	`myptr[0x3A] = rmodseg & 0xff;`
152	`myptr[0x3B] = rmodseg >> 8;`	160	`myptr[0x3B] = rmodseg >> 8;`
153		161
154	`/* copy rmod to its destination (right past the PSP I prepared) */`	162	`/* copy rmod to its destination (right past the PSP I prepared) */`
155	`myptr = MK_FP(rmodseg, 0x100);`	163	`myptr = MK_FP(rmodseg, 0x100);`
156	`_fmemcpy(myptr, rmodcore, rmodcore_len);`	164	`_fmemcpy(myptr, rmodcore, rmodcore_len);`
157		165
158	`/* mark rmod memory (MCB) as "self owned" */`	166	`/* mark rmod memory (MCB) as "self owned" */`
159	`mcb = MK_FP(rmodseg - 1, 0);`	167	`mcb = MK_FP(rmodseg - 1, 0);`
160	`owner = (void far *)(mcb + 1);`	168	`owner = (void far *)(mcb + 1);`
161	`*owner = rmodseg;`	169	`*owner = rmodseg;`
162	`_fmemcpy(mcb + 8, "SVARCOM", 8);`	170	`_fmemcpy(mcb + 8, "SVARCOM", 8);`
163		171
164	`/* mark env memory (MCB) as "owned by rmod" */`	172	`/* mark env memory (MCB) as "owned by rmod" */`
165	`mcb = MK_FP(envseg - 1, 0);`	173	`mcb = MK_FP(envseg - 1, 0);`
166	`owner = (void far *)(mcb + 1);`	174	`owner = (void far *)(mcb + 1);`
167	`*owner = rmodseg;`	175	`*owner = rmodseg;`
168	`_fmemcpy(mcb + 8, "SVARENV", 8);`	176	`_fmemcpy(mcb + 8, "SVARENV", 8);`
169		177
170	`/* if env block is newly allocated, fill it with a few NULLs */`	178	`/* if env block is newly allocated, fill it with a few NULLs */`
171	`if (envsize != 0) {`	179	`if (envsize != 0) {`
172	`owner = MK_FP(envseg, 0);`	180	`owner = MK_FP(envseg, 0);`
173	`owner[0] = 0;`	181	`owner[0] = 0;`
174	`owner[1] = 0;`	182	`owner[1] = 0;`
175	`}`	183	`}`
176		184
177	`/* set CTRL+BREAK handler to rmod */`	185	`/* set CTRL+BREAK handler to rmod */`
178	`_asm {`	186	`_asm {`
179	`push ax`	187	`push ax`
180	`push dx`	188	`push dx`
181	`push ds`	189	`push ds`
182	`mov ax, 0x2523`	190	`mov ax, 0x2523`
183	`mov ds, rmodseg`	191	`mov ds, rmodseg`
184	`mov dx, RMOD_OFFSET_BRKHANDLER`	192	`mov dx, RMOD_OFFSET_BRKHANDLER`
185	`int 0x21`	193	`int 0x21`
186	`pop ds`	194	`pop ds`
187	`pop dx`	195	`pop dx`
188	`pop ax`	196	`pop ax`
189	`}`	197	`}`
190		198
191	`/* mark the input buffer as empty */`	199	`/* mark the input buffer as empty */`
192	`myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);`	200	`myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);`
193	`myptr[0] = 128; /* max acceptable length */`	201	`myptr[0] = 128; /* max acceptable length */`
194	`myptr[1] = 0; /* len of currently stored history string */`	202	`myptr[1] = 0; /* len of currently stored history string */`
195	`myptr[2] = '\r'; /* string terminator */`	203	`myptr[2] = '\r'; /* string terminator */`
196	`myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */`	204	`myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */`
197	`myptr[4] = 0xFE; /* 2nd byte of the signature */`	205	`myptr[4] = 0xFE; /* 2nd byte of the signature */`
198		206
199	`/* prepare result (rmod props) */`	207	`/* prepare result (rmod props) */`
200	`res = MK_FP(rmodseg, 0x100 + rmodcore_len);`	208	`res = MK_FP(rmodseg, 0x100 + rmodcore_len);`
201	`_fmemset(res, 0, sizeof(res)); / zero out */`	209	`_fmemset(res, 0, sizeof(res)); / zero out */`
202	`res->rmodseg = rmodseg; /* rmod segment */`	210	`res->rmodseg = rmodseg; /* rmod segment */`
203	`res->origenvseg = origenvseg; /* original environment segment */`	211	`res->origenvseg = origenvseg; /* original environment segment */`
204		212
205	`/* write env segment to rmod's PSP */`	213	`/* write env segment to rmod's PSP */`
206	`owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);`	214	`owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);`
207	`*owner = envseg;`	215	`*owner = envseg;`
208		216
209	`/* write boot drive to rmod bootdrive field */`	217	`/* write boot drive to rmod bootdrive field */`
210	`_asm {`	218	`_asm {`
211	`push ax`	219	`push ax`
212	`push bx`	220	`push bx`
213	`push dx`	221	`push dx`
214	`push ds`	222	`push ds`
215	`mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */`	223	`mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */`
216	`int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */`	224	`int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */`
217	`add dl, 'A'-1 /* convert to a proper ASCII letter */`	225	`add dl, 'A'-1 /* convert to a proper ASCII letter */`
218	`/* set DS to rmodseg */`	226	`/* set DS to rmodseg */`
219	`mov ax, rmodseg`	227	`mov ax, rmodseg`
220	`mov ds, ax`	228	`mov ds, ax`
221	`/* write boot drive to rmod bootdrive field */`	229	`/* write boot drive to rmod bootdrive field */`
222	`mov bx, RMOD_OFFSET_BOOTDRIVE`	230	`mov bx, RMOD_OFFSET_BOOTDRIVE`
223	`mov [bx], dl`	231	`mov [bx], dl`
224	`pop ds`	232	`pop ds`
225	`pop dx`	233	`pop dx`
226	`pop bx`	234	`pop bx`
227	`pop ax`	235	`pop ax`
228	`}`	236	`}`
229		237
230	`/* save my original parent in rmod's memory */`	238	`/* save my original parent in rmod's memory */`
231	`res->origparent = ((unsigned long )0x0a); /* original parent seg:off is at 0x0a of my PSP */`	239	`res->origparent = ((unsigned long )0x0a); /* original parent seg:off is at 0x0a of my PSP */`
232		240
233	`/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I`	241	`/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I`
234	`* terminate and save the original handler in rmod's memory */`	242	`* terminate and save the original handler in rmod's memory */`
235	`{`	243	`{`
236	`unsigned short ptr = (void )0x0a; /* int22 handler is at 0x0A of the PSP */`	244	`unsigned short ptr = (void )0x0a; /* int22 handler is at 0x0A of the PSP */`
237	`ptr[0] = RMOD_OFFSET_ROUTINE;`	245	`ptr[0] = RMOD_OFFSET_ROUTINE;`
238	`ptr[1] = rmodseg;`	246	`ptr[1] = rmodseg;`
239	`}`	247	`}`
240		248
241	`return(res);`	249	`return(res);`
242	`}`	250	`}`
243		251
244		252
245	`/* look up my parent: if it's rmod then return a ptr to its props struct,`	253	`/* look up my parent: if it's rmod then return a ptr to its props struct,`
246	`* otherwise return NULL`	254	`* otherwise return NULL`
247	`* I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */`	255	`* I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */`
248	`struct rmod_props far *rmod_find(unsigned short rmodcore_len) {`	256	`struct rmod_props far *rmod_find(unsigned short rmodcore_len) {`
249	`unsigned short parent = (void )0x0C;`	257	`unsigned short parent = (void )0x0C;`
250	`unsigned short far *ptr;`	258	`unsigned short far *ptr;`
251	`const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};`	259	`const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};`
252	`unsigned char cmdtail = (void )0x80;`	260	`unsigned char cmdtail = (void )0x80;`
253	`unsigned char i;`	261	`unsigned char i;`
254	`/* is it rmod? */`	262	`/* is it rmod? */`
255	`ptr = MK_FP(*parent, 0x100);`	263	`ptr = MK_FP(*parent, 0x100);`
256	`for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);`	264	`for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);`
257	`/* match successfull (rmod is my parent) - but is it really a respawn?`	265	`/* match successfull (rmod is my parent) - but is it really a respawn?`
258	`* command-line tail should contain a single character '\r' */`	266	`* command-line tail should contain a single character '\r' */`
259	`if ((cmdtail[0] != 1) \|\| (cmdtail[1] != '\n')) return(NULL);`	267	`if ((cmdtail[0] != 1) \|\| (cmdtail[1] != '\n')) return(NULL);`
260	`cmdtail[0] = 0;`	268	`cmdtail[0] = 0;`
261	`cmdtail[1] = '\r';`	269	`cmdtail[1] = '\r';`
262	`/* */`	270	`/* */`
263	`return(MK_FP(*parent, 0x100 + rmodcore_len));`	271	`return(MK_FP(*parent, 0x100 + rmodcore_len));`
264	`}`	272	`}`
265		273
266		274
267	`/* update rmod's pointer to comspec */`	275	`/* update rmod's pointer to comspec */`
268	`void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {`	276	`void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {`
269	`unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);`	277	`unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);`
270	`char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");`	278	`char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");`
271	`if (comspecfp != NULL) {`	279	`if (comspecfp != NULL) {`
272	`*comspecptr = FP_OFF(comspecfp);`	280	`*comspecptr = FP_OFF(comspecfp);`
273	`} else {`	281	`} else {`
274	`*comspecptr = 0;`	282	`*comspecptr = 0;`
275	`}`	283	`}`
276	`}`	284	`}`
277		285
278		286
279	`/* allocates bytes of far memory, flags it as belonging to rmod`	287	`/* allocates bytes of far memory, flags it as belonging to rmod`
280	`* the new block can be optionally flagged as 'ident' (if not null) and zero`	288	`* the new block can be optionally flagged as 'ident' (if not null) and zero`
281	`* out the newly allocated memory.`	289	`* out the newly allocated memory.`
282	`* returns a far ptr to the allocated block, or NULL on error */`	290	`* returns a far ptr to the allocated block, or NULL on error */`
283	`void far rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char ident) {`	291	`void far rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char ident) {`
284	`unsigned short far *owner;`	292	`unsigned short far *owner;`
285	`unsigned short newseg = 0;`	293	`unsigned short newseg = 0;`
286		294
287	`/* ask DOS for a memory block (as high as possible) */`	295	`/* ask DOS for a memory block (as high as possible) */`
288	`_asm {`	296	`_asm {`
289	`push bx /* save initial value in BX so I can restore it later */`	297	`push bx /* save initial value in BX so I can restore it later */`
290		298
291	`/* get current allocation strategy and save it on stack */`	299	`/* get current allocation strategy and save it on stack */`
292	`mov ax, 0x5800`	300	`mov ax, 0x5800`
293	`int 0x21`	301	`int 0x21`
294	`push ax`	302	`push ax`
295		303
296	`/* set strategy to 'last fit, try high then low memory' */`	304	`/* set strategy to 'last fit, try high then low memory' */`
297	`mov ax, 0x5801`	305	`mov ax, 0x5801`
298	`mov bx, 0x0082`	306	`mov bx, 0x0082`
299	`int 0x21`	307	`int 0x21`
300		308
301	`/* ask for a memory block and save the given segment to rmodseg */`	309	`/* ask for a memory block and save the given segment to rmodseg */`
302	`mov ah, 0x48 /* Allocate Memory */`	310	`mov ah, 0x48 /* Allocate Memory */`
303	`mov bx, bytes`	311	`mov bx, bytes`
304	`add bx, 15 /* convert bytes to paragraphs */`	312	`add bx, 15 /* convert bytes to paragraphs */`
305	`shr bx, 1 /* bx /= 16 */`	313	`shr bx, 1 /* bx /= 16 */`
306	`shr bx, 1`	314	`shr bx, 1`
307	`shr bx, 1`	315	`shr bx, 1`
308	`shr bx, 1`	316	`shr bx, 1`
309	`int 0x21`	317	`int 0x21`
310		318
311	`/* error handling */`	319	`/* error handling */`
312	`jc FAIL`	320	`jc FAIL`
313		321
314	`/* save newly allocated segment to newseg */`	322	`/* save newly allocated segment to newseg */`
315	`mov newseg, ax`	323	`mov newseg, ax`
316		324
317	`FAIL:`	325	`FAIL:`
318	`/* restore initial allocation strategy */`	326	`/* restore initial allocation strategy */`
319	`mov ax, 0x5801`	327	`mov ax, 0x5801`
320	`pop bx`	328	`pop bx`
321	`int 0x21`	329	`int 0x21`
322		330
323	`pop bx /* restore BX to its initial value */`	331	`pop bx /* restore BX to its initial value */`
324	`}`	332	`}`
325		333
326	`if (newseg == 0) return(NULL);`	334	`if (newseg == 0) return(NULL);`
327		335
328	`/* mark memory as "owned by rmod" */`	336	`/* mark memory as "owned by rmod" */`
329	`owner = (void far *)(MK_FP(newseg - 1, 1));`	337	`owner = (void far *)(MK_FP(newseg - 1, 1));`
330	`*owner = rmod_seg;`	338	`*owner = rmod_seg;`
331		339
332	`/* set the MCB description to ident, if provided */`	340	`/* set the MCB description to ident, if provided */`
333	`if (ident) {`	341	`if (ident) {`
334	`char far *mcbdesc = MK_FP(newseg - 1, 8);`	342	`char far *mcbdesc = MK_FP(newseg - 1, 8);`
335	`int i;`	343	`int i;`
336	`_fmemset(mcbdesc, 0, 8);`	344	`_fmemset(mcbdesc, 0, 8);`
337	`for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */`	345	`for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */`
338	`mcbdesc[i] = ident[i];`	346	`mcbdesc[i] = ident[i];`
339	`}`	347	`}`
340	`}`	348	`}`
341		349
342	`/* zero out the memory before handing it out */`	350	`/* zero out the memory before handing it out */`
343	`_fmemset(MK_FP(newseg, 0), 0, bytes);`	351	`_fmemset(MK_FP(newseg, 0), 0, bytes);`
344		352
345	`return(MK_FP(newseg, 0));`	353	`return(MK_FP(newseg, 0));`
346	`}`	354	`}`
347		355
348		356
349	`/* free memory previously allocated by rmod_fcalloc() */`	357	`/* free memory previously allocated by rmod_fcalloc() */`
350	`void rmod_ffree(void far *ptr) {`	358	`void rmod_ffree(void far *ptr) {`
351	`unsigned short ptrseg;`	359	`unsigned short ptrseg;`
352	`unsigned short myseg = 0;`	360	`unsigned short myseg = 0;`
353	`unsigned short far *owner;`	361	`unsigned short far *owner;`
354	`if (ptr == NULL) return;`	362	`if (ptr == NULL) return;`
355	`ptrseg = FP_SEG(ptr);`	363	`ptrseg = FP_SEG(ptr);`
356		364
357	`/* get my own segment */`	365	`/* get my own segment */`
358	`_asm {`	366	`_asm {`
359	`mov myseg, cs`	367	`mov myseg, cs`
360	`}`	368	`}`
361		369
362	`/* mark memory in MCB as my own, otherwise DOS might refuse to free it */`	370	`/* mark memory in MCB as my own, otherwise DOS might refuse to free it */`
363	`owner = MK_FP(ptrseg - 1, 1);`	371	`owner = MK_FP(ptrseg - 1, 1);`
364	`*owner = myseg;`	372	`*owner = myseg;`
365		373
366	`/* free the memory block */`	374	`/* free the memory block */`
367	`_asm {`	375	`_asm {`
368	`push es`	376	`push es`
369	`mov ah, 0x49 /* Free Memory Block */`	377	`mov ah, 0x49 /* Free Memory Block */`
370	`mov es, ptrseg`	378	`mov es, ptrseg`
371	`int 0x21`	379	`int 0x21`
372	`pop es`	380	`pop es`
373	`}`	381	`}`
374	`}`	382	`}`
375		383
376		384
377	`/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */`	385	`/* 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) {`	386	`void rmod_free_bat_llist(struct rmod_props far *rmod) {`
379	`while (rmod->bat != NULL) {`	387	`while (rmod->bat != NULL) {`
380	`struct batctx far *victim = rmod->bat;`	388	`struct batctx far *victim = rmod->bat;`
381	`rmod->bat = rmod->bat->parent;`	389	`rmod->bat = rmod->bat->parent;`
382	`rmod_ffree(victim);`	390	`rmod_ffree(victim);`
383	`}`	391	`}`
384	`}`	392	`}`
385		393

Subversion Repositories SvarDOS

(root)/svarcom/trunk/rmodinit.c @ 1094 – Rev 1591 → 1594