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 {
    /* 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
  }
 
  if (rmodseg == 0xffff) {
    outputnl("malloc error");
    return(NULL);
  }
 
  /* copy my own PSP where RMOD is about to land, so it has a proper PSP as well */
  /* take care to init the JFT (20 bytes starting at offset 0x18) to 0xff, which
   * essentially means "empty JFT slot" */
  myptr = MK_FP(rmodseg, 0);
  {
    unsigned short i;
    char *mypsp = (void *)0;
    for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];
    for (i = 0x18; i < 0x18+20; i++) myptr[i] = 0xff;
  }
 
  /* 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 stacat 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 1588	Rev 1589
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	`/* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */`	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 */`	60	`mov ax, 0x5802 /* GET UMB LINK STATE */`
61	`int 0x21`	61	`int 0x21`
62	`xor ah, ah`	62	`xor ah, ah`
63	`push ax /* save link state on stack */`	63	`push ax /* save link state on stack */`
64	`mov ax, 0x5803 /* SET UMB LINK STATE */`	64	`mov ax, 0x5803 /* SET UMB LINK STATE */`
65	`mov bx, 1`	65	`mov bx, 1`
66	`int 0x21`	66	`int 0x21`
67	`/* get current allocation strategy and save it in DX */`	67	`/* get current allocation strategy and save it in DX */`
68	`mov ax, 0x5800`	68	`mov ax, 0x5800`
69	`int 0x21`	69	`int 0x21`
70	`push ax`	70	`push ax`
71	`pop dx`	71	`pop dx`
72	`/* set strategy to 'last fit, try high then low memory' */`	72	`/* set strategy to 'last fit, try high then low memory' */`
73	`mov ax, 0x5801`	73	`mov ax, 0x5801`
74	`mov bx, 0x0082`	74	`mov bx, 0x0082`
75	`int 0x21`	75	`int 0x21`
76	`/* ask for a memory block and save the given segment to rmodseg */`	76	`/* ask for a memory block and save the given segment to rmodseg */`
77	`mov ah, 0x48`	77	`mov ah, 0x48`
78	`mov bx, sizeof_rmodandprops_paras`	78	`mov bx, sizeof_rmodandprops_paras`
79	`int 0x21`	79	`int 0x21`
80	`jc ALLOC_FAIL`	80	`jc ALLOC_FAIL`
81	`mov rmodseg, ax`	81	`mov rmodseg, ax`
82	`/* ask for a memory block for the environment and save it to envseg (only if custom size requested) */`	82	`/* ask for a memory block for the environment and save it to envseg (only if custom size requested) */`
83	`mov bx, envsize`	83	`mov bx, envsize`
84	`test bx, bx`	84	`test bx, bx`
85	`jz ALLOC_FAIL`	85	`jz ALLOC_FAIL`
86	`mov ah, 0x48`	86	`mov ah, 0x48`
87	`int 0x21`	87	`int 0x21`
88	`jc ALLOC_FAIL`	88	`jc ALLOC_FAIL`
89	`mov envseg, ax`	89	`mov envseg, ax`
90		90
91	`ALLOC_FAIL:`	91	`ALLOC_FAIL:`
92	`/* restore initial allocation strategy */`	92	`/* restore initial allocation strategy */`
93	`mov ax, 0x5801`	93	`mov ax, 0x5801`
94	`mov bx, dx`	94	`mov bx, dx`
95	`int 0x21`	95	`int 0x21`
96	`/* restore initial UMB memory link state */`	96	`/* restore initial UMB memory link state */`
97	`mov ax, 0x5803`	97	`mov ax, 0x5803`
98	`pop bx /* pop initial UMB link state from stack */`	98	`pop bx /* pop initial UMB link state from stack */`
99	`int 0x21`	99	`int 0x21`
100	`}`	100	`}`
101		101
102	`if (rmodseg == 0xffff) {`	102	`if (rmodseg == 0xffff) {`
103	`outputnl("malloc error");`	103	`outputnl("malloc error");`
104	`return(NULL);`	104	`return(NULL);`
105	`}`	105	`}`
106		106
107	`/* copy my own PSP where RMOD is about to land, so it has a proper PSP as well */`	107	`/* copy my own PSP where RMOD is about to land, so it has a proper PSP as well */`
108	`/* take care to init the JFT (20 bytes starting at offset 0x18) to 0xff, which`	108	`/* take care to init the JFT (20 bytes starting at offset 0x18) to 0xff, which`
109	`* essentially means "empty JFT slot" */`	109	`* essentially means "empty JFT slot" */`
110	`myptr = MK_FP(rmodseg, 0);`	110	`myptr = MK_FP(rmodseg, 0);`
111	`{`	111	`{`
112	`unsigned short i;`	112	`unsigned short i;`
113	`char mypsp = (void )0;`	113	`char mypsp = (void )0;`
114	`for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];`	114	`for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];`
115	`for (i = 0x18; i < 0x18+20; i++) myptr[i] = 0xff;`	115	`for (i = 0x18; i < 0x18+20; i++) myptr[i] = 0xff;`
116	`}`	116	`}`
117		117
118	`/* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */`	118	`/* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */`
119	`myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */`	119	`myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */`
120	`myptr[0x17] = rmodseg >> 8;`	120	`myptr[0x17] = rmodseg >> 8;`
121		121
122	`/* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31 */`	122	`/* 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 stacat the end of the`
-		124	`* tail. E. C. Masloch kindly explained why this would be a bad idea:`
-		125	`*`
-		126	`* "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`
-		128	`* 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`
-		130	`* 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>`
-		132	`*/`
123	`myptr[0x2e] = 254; /* I abuse the PSP's command line tail as stack */`	133	`myptr[0x2e] = 192; /* middle of the command line tail area so I have 64 bytes */`
124	`myptr[0x2f] = 0;`	134	`myptr[0x2f] = 0; /* before and 64 bytes in front of me */`
125	`myptr[0x30] = rmodseg & 0xff;`	135	`myptr[0x30] = rmodseg & 0xff;`
126	`myptr[0x31] = rmodseg >> 8;`	136	`myptr[0x31] = rmodseg >> 8;`
127		137
128	`/* patch up RMOD's PSP: JFT size @ 0x32-0x33 */`	138	`/* patch up RMOD's PSP: JFT size @ 0x32-0x33 */`
129	`myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */`	139	`myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */`
130	`myptr[0x33] = 0;`	140	`myptr[0x33] = 0;`
131		141
132	`/* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */`	142	`/* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */`
133	`myptr[0x34] = 0x18; /* the JFT is in the PSP itself */`	143	`myptr[0x34] = 0x18; /* the JFT is in the PSP itself */`
134	`myptr[0x35] = 0;`	144	`myptr[0x35] = 0;`
135	`myptr[0x36] = rmodseg & 0xff;`	145	`myptr[0x36] = rmodseg & 0xff;`
136	`myptr[0x37] = rmodseg >> 8;`	146	`myptr[0x37] = rmodseg >> 8;`
137		147
138	`/* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */`	148	`/* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */`
139	`myptr[0x38] = 0;`	149	`myptr[0x38] = 0;`
140	`myptr[0x39] = 0;`	150	`myptr[0x39] = 0;`
141	`myptr[0x3A] = rmodseg & 0xff;`	151	`myptr[0x3A] = rmodseg & 0xff;`
142	`myptr[0x3B] = rmodseg >> 8;`	152	`myptr[0x3B] = rmodseg >> 8;`
143		153
144	`/* copy rmod to its destination (right past the PSP I prepared) */`	154	`/* copy rmod to its destination (right past the PSP I prepared) */`
145	`myptr = MK_FP(rmodseg, 0x100);`	155	`myptr = MK_FP(rmodseg, 0x100);`
146	`_fmemcpy(myptr, rmodcore, rmodcore_len);`	156	`_fmemcpy(myptr, rmodcore, rmodcore_len);`
147		157
148	`/* mark rmod memory (MCB) as "self owned" */`	158	`/* mark rmod memory (MCB) as "self owned" */`
149	`mcb = MK_FP(rmodseg - 1, 0);`	159	`mcb = MK_FP(rmodseg - 1, 0);`
150	`owner = (void far *)(mcb + 1);`	160	`owner = (void far *)(mcb + 1);`
151	`*owner = rmodseg;`	161	`*owner = rmodseg;`
152	`_fmemcpy(mcb + 8, "SVARCOM", 8);`	162	`_fmemcpy(mcb + 8, "SVARCOM", 8);`
153		163
154	`/* mark env memory (MCB) as "owned by rmod" */`	164	`/* mark env memory (MCB) as "owned by rmod" */`
155	`mcb = MK_FP(envseg - 1, 0);`	165	`mcb = MK_FP(envseg - 1, 0);`
156	`owner = (void far *)(mcb + 1);`	166	`owner = (void far *)(mcb + 1);`
157	`*owner = rmodseg;`	167	`*owner = rmodseg;`
158	`_fmemcpy(mcb + 8, "SVARENV", 8);`	168	`_fmemcpy(mcb + 8, "SVARENV", 8);`
159		169
160	`/* if env block is newly allocated, fill it with a few NULLs */`	170	`/* if env block is newly allocated, fill it with a few NULLs */`
161	`if (envsize != 0) {`	171	`if (envsize != 0) {`
162	`owner = MK_FP(envseg, 0);`	172	`owner = MK_FP(envseg, 0);`
163	`owner[0] = 0;`	173	`owner[0] = 0;`
164	`owner[1] = 0;`	174	`owner[1] = 0;`
165	`}`	175	`}`
166		176
167	`/* set CTRL+BREAK handler to rmod */`	177	`/* set CTRL+BREAK handler to rmod */`
168	`_asm {`	178	`_asm {`
169	`push ax`	179	`push ax`
170	`push dx`	180	`push dx`
171	`push ds`	181	`push ds`
172	`mov ax, 0x2523`	182	`mov ax, 0x2523`
173	`mov ds, rmodseg`	183	`mov ds, rmodseg`
174	`mov dx, RMOD_OFFSET_BRKHANDLER`	184	`mov dx, RMOD_OFFSET_BRKHANDLER`
175	`int 0x21`	185	`int 0x21`
176	`pop ds`	186	`pop ds`
177	`pop dx`	187	`pop dx`
178	`pop ax`	188	`pop ax`
179	`}`	189	`}`
180		190
181	`/* mark the input buffer as empty */`	191	`/* mark the input buffer as empty */`
182	`myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);`	192	`myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);`
183	`myptr[0] = 128; /* max acceptable length */`	193	`myptr[0] = 128; /* max acceptable length */`
184	`myptr[1] = 0; /* len of currently stored history string */`	194	`myptr[1] = 0; /* len of currently stored history string */`
185	`myptr[2] = '\r'; /* string terminator */`	195	`myptr[2] = '\r'; /* string terminator */`
186	`myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */`	196	`myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */`
187	`myptr[4] = 0xFE; /* 2nd byte of the signature */`	197	`myptr[4] = 0xFE; /* 2nd byte of the signature */`
188		198
189	`/* prepare result (rmod props) */`	199	`/* prepare result (rmod props) */`
190	`res = MK_FP(rmodseg, 0x100 + rmodcore_len);`	200	`res = MK_FP(rmodseg, 0x100 + rmodcore_len);`
191	`_fmemset(res, 0, sizeof(res)); / zero out */`	201	`_fmemset(res, 0, sizeof(res)); / zero out */`
192	`res->rmodseg = rmodseg; /* rmod segment */`	202	`res->rmodseg = rmodseg; /* rmod segment */`
193	`res->origenvseg = origenvseg; /* original environment segment */`	203	`res->origenvseg = origenvseg; /* original environment segment */`
194		204
195	`/* write env segment to rmod's PSP */`	205	`/* write env segment to rmod's PSP */`
196	`owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);`	206	`owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);`
197	`*owner = envseg;`	207	`*owner = envseg;`
198		208
199	`/* write boot drive to rmod bootdrive field */`	209	`/* write boot drive to rmod bootdrive field */`
200	`_asm {`	210	`_asm {`
201	`push ax`	211	`push ax`
202	`push bx`	212	`push bx`
203	`push dx`	213	`push dx`
204	`push ds`	214	`push ds`
205	`mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */`	215	`mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */`
206	`int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */`	216	`int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */`
207	`add dl, 'A'-1 /* convert to a proper ASCII letter */`	217	`add dl, 'A'-1 /* convert to a proper ASCII letter */`
208	`/* set DS to rmodseg */`	218	`/* set DS to rmodseg */`
209	`mov ax, rmodseg`	219	`mov ax, rmodseg`
210	`mov ds, ax`	220	`mov ds, ax`
211	`/* write boot drive to rmod bootdrive field */`	221	`/* write boot drive to rmod bootdrive field */`
212	`mov bx, RMOD_OFFSET_BOOTDRIVE`	222	`mov bx, RMOD_OFFSET_BOOTDRIVE`
213	`mov [bx], dl`	223	`mov [bx], dl`
214	`pop ds`	224	`pop ds`
215	`pop dx`	225	`pop dx`
216	`pop bx`	226	`pop bx`
217	`pop ax`	227	`pop ax`
218	`}`	228	`}`
219		229
220	`/* save my original parent in rmod's memory */`	230	`/* save my original parent in rmod's memory */`
221	`res->origparent = ((unsigned long )0x0a); /* original parent seg:off is at 0x0a of my PSP */`	231	`res->origparent = ((unsigned long )0x0a); /* original parent seg:off is at 0x0a of my PSP */`
222		232
223	`/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I`	233	`/* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I`
224	`* terminate and save the original handler in rmod's memory */`	234	`* terminate and save the original handler in rmod's memory */`
225	`{`	235	`{`
226	`unsigned short ptr = (void )0x0a; /* int22 handler is at 0x0A of the PSP */`	236	`unsigned short ptr = (void )0x0a; /* int22 handler is at 0x0A of the PSP */`
227	`ptr[0] = RMOD_OFFSET_ROUTINE;`	237	`ptr[0] = RMOD_OFFSET_ROUTINE;`
228	`ptr[1] = rmodseg;`	238	`ptr[1] = rmodseg;`
229	`}`	239	`}`
230		240
231	`return(res);`	241	`return(res);`
232	`}`	242	`}`
233		243
234		244
235	`/* look up my parent: if it's rmod then return a ptr to its props struct,`	245	`/* look up my parent: if it's rmod then return a ptr to its props struct,`
236	`* otherwise return NULL`	246	`* otherwise return NULL`
237	`* I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */`	247	`* I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */`
238	`struct rmod_props far *rmod_find(unsigned short rmodcore_len) {`	248	`struct rmod_props far *rmod_find(unsigned short rmodcore_len) {`
239	`unsigned short parent = (void )0x0C;`	249	`unsigned short parent = (void )0x0C;`
240	`unsigned short far *ptr;`	250	`unsigned short far *ptr;`
241	`const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};`	251	`const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};`
242	`unsigned char cmdtail = (void )0x80;`	252	`unsigned char cmdtail = (void )0x80;`
243	`unsigned char i;`	253	`unsigned char i;`
244	`/* is it rmod? */`	254	`/* is it rmod? */`
245	`ptr = MK_FP(*parent, 0x100);`	255	`ptr = MK_FP(*parent, 0x100);`
246	`for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);`	256	`for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);`
247	`/* match successfull (rmod is my parent) - but is it really a respawn?`	257	`/* match successfull (rmod is my parent) - but is it really a respawn?`
248	`* command-line tail should contain a single character '\r' */`	258	`* command-line tail should contain a single character '\r' */`
249	`if ((cmdtail[0] != 1) \|\| (cmdtail[1] != '\n')) return(NULL);`	259	`if ((cmdtail[0] != 1) \|\| (cmdtail[1] != '\n')) return(NULL);`
250	`cmdtail[0] = 0;`	260	`cmdtail[0] = 0;`
251	`cmdtail[1] = '\r';`	261	`cmdtail[1] = '\r';`
252	`/* */`	262	`/* */`
253	`return(MK_FP(*parent, 0x100 + rmodcore_len));`	263	`return(MK_FP(*parent, 0x100 + rmodcore_len));`
254	`}`	264	`}`
255		265
256		266
257	`/* update rmod's pointer to comspec */`	267	`/* update rmod's pointer to comspec */`
258	`void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {`	268	`void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {`
259	`unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);`	269	`unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);`
260	`char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");`	270	`char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");`
261	`if (comspecfp != NULL) {`	271	`if (comspecfp != NULL) {`
262	`*comspecptr = FP_OFF(comspecfp);`	272	`*comspecptr = FP_OFF(comspecfp);`
263	`} else {`	273	`} else {`
264	`*comspecptr = 0;`	274	`*comspecptr = 0;`
265	`}`	275	`}`
266	`}`	276	`}`
267		277
268		278
269	`/* allocates bytes of far memory, flags it as belonging to rmod`	279	`/* allocates bytes of far memory, flags it as belonging to rmod`
270	`* the new block can be optionally flagged as 'ident' (if not null) and zero`	280	`* the new block can be optionally flagged as 'ident' (if not null) and zero`
271	`* out the newly allocated memory.`	281	`* out the newly allocated memory.`
272	`* returns a far ptr to the allocated block, or NULL on error */`	282	`* returns a far ptr to the allocated block, or NULL on error */`
273	`void far rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char ident) {`	283	`void far rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char ident) {`
274	`unsigned short far *owner;`	284	`unsigned short far *owner;`
275	`unsigned short newseg = 0;`	285	`unsigned short newseg = 0;`
276		286
277	`/* ask DOS for a memory block (as high as possible) */`	287	`/* ask DOS for a memory block (as high as possible) */`
278	`_asm {`	288	`_asm {`
279	`push bx /* save initial value in BX so I can restore it later */`	289	`push bx /* save initial value in BX so I can restore it later */`
280		290
281	`/* get current allocation strategy and save it on stack */`	291	`/* get current allocation strategy and save it on stack */`
282	`mov ax, 0x5800`	292	`mov ax, 0x5800`
283	`int 0x21`	293	`int 0x21`
284	`push ax`	294	`push ax`
285		295
286	`/* set strategy to 'last fit, try high then low memory' */`	296	`/* set strategy to 'last fit, try high then low memory' */`
287	`mov ax, 0x5801`	297	`mov ax, 0x5801`
288	`mov bx, 0x0082`	298	`mov bx, 0x0082`
289	`int 0x21`	299	`int 0x21`
290		300
291	`/* ask for a memory block and save the given segment to rmodseg */`	301	`/* ask for a memory block and save the given segment to rmodseg */`
292	`mov ah, 0x48 /* Allocate Memory */`	302	`mov ah, 0x48 /* Allocate Memory */`
293	`mov bx, bytes`	303	`mov bx, bytes`
294	`add bx, 15 /* convert bytes to paragraphs */`	304	`add bx, 15 /* convert bytes to paragraphs */`
295	`shr bx, 1 /* bx /= 16 */`	305	`shr bx, 1 /* bx /= 16 */`
296	`shr bx, 1`	306	`shr bx, 1`
297	`shr bx, 1`	307	`shr bx, 1`
298	`shr bx, 1`	308	`shr bx, 1`
299	`int 0x21`	309	`int 0x21`
300		310
301	`/* error handling */`	311	`/* error handling */`
302	`jc FAIL`	312	`jc FAIL`
303		313
304	`/* save newly allocated segment to newseg */`	314	`/* save newly allocated segment to newseg */`
305	`mov newseg, ax`	315	`mov newseg, ax`
306		316
307	`FAIL:`	317	`FAIL:`
308	`/* restore initial allocation strategy */`	318	`/* restore initial allocation strategy */`
309	`mov ax, 0x5801`	319	`mov ax, 0x5801`
310	`pop bx`	320	`pop bx`
311	`int 0x21`	321	`int 0x21`
312		322
313	`pop bx /* restore BX to its initial value */`	323	`pop bx /* restore BX to its initial value */`
314	`}`	324	`}`
315		325
316	`if (newseg == 0) return(NULL);`	326	`if (newseg == 0) return(NULL);`
317		327
318	`/* mark memory as "owned by rmod" */`	328	`/* mark memory as "owned by rmod" */`
319	`owner = (void far *)(MK_FP(newseg - 1, 1));`	329	`owner = (void far *)(MK_FP(newseg - 1, 1));`
320	`*owner = rmod_seg;`	330	`*owner = rmod_seg;`
321		331
322	`/* set the MCB description to ident, if provided */`	332	`/* set the MCB description to ident, if provided */`
323	`if (ident) {`	333	`if (ident) {`
324	`char far *mcbdesc = MK_FP(newseg - 1, 8);`	334	`char far *mcbdesc = MK_FP(newseg - 1, 8);`
325	`int i;`	335	`int i;`
326	`_fmemset(mcbdesc, 0, 8);`	336	`_fmemset(mcbdesc, 0, 8);`
327	`for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */`	337	`for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */`
328	`mcbdesc[i] = ident[i];`	338	`mcbdesc[i] = ident[i];`
329	`}`	339	`}`
330	`}`	340	`}`
331		341
332	`/* zero out the memory before handing it out */`	342	`/* zero out the memory before handing it out */`
333	`_fmemset(MK_FP(newseg, 0), 0, bytes);`	343	`_fmemset(MK_FP(newseg, 0), 0, bytes);`
334		344
335	`return(MK_FP(newseg, 0));`	345	`return(MK_FP(newseg, 0));`
336	`}`	346	`}`
337		347
338		348
339	`/* free memory previously allocated by rmod_fcalloc() */`	349	`/* free memory previously allocated by rmod_fcalloc() */`
340	`void rmod_ffree(void far *ptr) {`	350	`void rmod_ffree(void far *ptr) {`
341	`unsigned short ptrseg;`	351	`unsigned short ptrseg;`
342	`unsigned short myseg = 0;`	352	`unsigned short myseg = 0;`
343	`unsigned short far *owner;`	353	`unsigned short far *owner;`
344	`if (ptr == NULL) return;`	354	`if (ptr == NULL) return;`
345	`ptrseg = FP_SEG(ptr);`	355	`ptrseg = FP_SEG(ptr);`
346		356
347	`/* get my own segment */`	357	`/* get my own segment */`
348	`_asm {`	358	`_asm {`
349	`mov myseg, cs`	359	`mov myseg, cs`
350	`}`	360	`}`
351		361
352	`/* mark memory in MCB as my own, otherwise DOS might refuse to free it */`	362	`/* mark memory in MCB as my own, otherwise DOS might refuse to free it */`
353	`owner = MK_FP(ptrseg - 1, 1);`	363	`owner = MK_FP(ptrseg - 1, 1);`
354	`*owner = myseg;`	364	`*owner = myseg;`
355		365
356	`/* free the memory block */`	366	`/* free the memory block */`
357	`_asm {`	367	`_asm {`
358	`push es`	368	`push es`
359	`mov ah, 0x49 /* Free Memory Block */`	369	`mov ah, 0x49 /* Free Memory Block */`
360	`mov es, ptrseg`	370	`mov es, ptrseg`
361	`int 0x21`	371	`int 0x21`
362	`pop es`	372	`pop es`
363	`}`	373	`}`
364	`}`	374	`}`
365		375
366		376
367	`/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */`	377	`/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */`
368	`void rmod_free_bat_llist(struct rmod_props far *rmod) {`	378	`void rmod_free_bat_llist(struct rmod_props far *rmod) {`
369	`while (rmod->bat != NULL) {`	379	`while (rmod->bat != NULL) {`
370	`struct batctx far *victim = rmod->bat;`	380	`struct batctx far *victim = rmod->bat;`
371	`rmod->bat = rmod->bat->parent;`	381	`rmod->bat = rmod->bat->parent;`
372	`rmod_ffree(victim);`	382	`rmod_ffree(victim);`
373	`}`	383	`}`
374	`}`	384	`}`
375		385

Subversion Repositories SvarDOS

(root)/svarcom/trunk/rmodinit.c @ 1100 – Rev 1588 → 1589