compilers/linux86-0.16.17/libc/bios/bios.c

   1 /* Copyright (C) 1996 Robert de Bath <robert@mayday.compulink.co.uk>
   2  * This file is part of the Linux-8086 C library and is distributed
   3  * under the GNU Library General Public License.
   4  */
   5
   6 #undef AOUT_STANDALONE
   7
   8 #if !__FIRST_ARG_IN_AX__
   9 #ifdef __AS386_16__
  10 #ifdef __STANDALONE__
  11
  12 #include <bios.h>
  13 #include <fcntl.h>
  14 #include <errno.h>
  15
  16 #ifdef L_bios_start
  17
  18 char ** environ = { 0 };
  19 int errno;
  20
  21 void (*__cleanup)() = 0;
  22
  23 #asm
  24   .data
  25 export ___argr
  26 ___argr:
  27   .word 0,0,0,0,0,0,0,0 ! A struct REGS: ax, bx, cx, dx, si, di, cflag, flags
  28 defarg:
  29   .word boot_str, 0
  30 boot_str:
  31   .asciz "boot"
  32 loop_save:
  33   .word 0
  34
  35   .text
  36 export ___cstartup      ! Crt0 startup
  37 ___cstartup:
  38   cli
  39 #ifndef AOUT_STANDALONE
  40   seg   cs
  41   cmp   word ptr [0],#$20CD     ! "int 20h" at psp:  CS:0000
  42   jne   not_dos
  43
  44   ! DOS - only AX has a defined value.
  45   ! All the segment registers are pointing at the PSP
  46   ! SP points to the top of the segment so is probably useable.
  47
  48   push  ax                      ! Save AX
  49   mov   ax,cs
  50   add   ax,#$10                 ! bump CS by 0x10
  51   push  ax
  52   mov   ax,#is_dos              ! resume address
  53   push  ax
  54   retf                          ! continue at next instruction
  55 dos_flag:
  56   .word 0                       ! Set to 1 if DOS
  57 is_dos:
  58   seg   cs
  59   inc   dos_flag
  60   pop   ax                      ! restore saved AX
  61
  62 not_dos:
  63   mov   sp,cs
  64   add   sp,#__segoff
  65   mov   ds,sp
  66   mov   ss,sp
  67   mov   bp,#__heap_top
  68   mov   sp,#___argr+14
  69   seg   cs
  70   push  [dos_flag]              ! Set the carry flag if we're under DOS.
  71 #else
  72   mov   bp,sp
  73   mov   sp,#___argr+12
  74 #endif
  75   push  di
  76   push  si
  77   push  dx
  78   push  cx
  79   push  bx
  80   push  ax
  81   mov   sp,bp
  82   sti
  83
  84 zap_bss:                ! Clear the BSS
  85   push  ds
  86   pop   es              ! ES now data seg
  87   mov   di,#__edata
  88   mov   cx,#__end
  89   sub   cx,di
  90   xor   ax,ax
  91   cld
  92   rep
  93    stosb
  94
  95   !mov  bp,ax           ! Top frame pointer, only needed if we get a debugger
  96   push  [_environ]
  97   mov   ax,#defarg      ! Don`t define __mkargv, standalone programs don`t
  98   push  ax              ! get any arguments.
  99   mov   ax,#1
 100   push  ax
 101
 102   mov   bx,#auto_start  ! Pointer to first autostart function
 103 auto_run:
 104   mov   [loop_save],bx
 105   mov   bx,[bx]
 106   test  bx,bx
 107   jz    no_entry
 108   call  bx              ! Call the function
 109 no_entry:
 110   mov   bx,[loop_save]
 111   inc   bx              ! next
 112   inc   bx
 113   jmp   auto_run        ! And round for the next.
 114
 115 call_exit:              ! Last item called by above.
 116   pop   bx              ! Be tidy.
 117   push  ax              ! At the end the last called was main() push it`s
 118   call  _exit           ! return val and call exit();
 119 bad_exit:
 120   jmp   bad_exit        ! Exit returned !!
 121
 122   loc   2
 123   .word _main           ! Segment 2 is the trailing pointers, main and the
 124   .word call_exit       ! routine to call exit.
 125 data_start:
 126
 127   .text
 128 export _exit
 129 _exit:                  ! exit(rv) function
 130   mov   bx,sp
 131   push  [bx+2]          ! Copy the `rv` for the exit fuctions.
 132   mov   bx,[___cleanup] ! Call exit, normally this is `__do_exit`
 133   test  bx,bx
 134   je    no_clean        ! But it`s default is null
 135   call  bx
 136 no_clean:
 137   inc   sp
 138   inc   sp
 139
 140 export __exit
 141 __exit:
 142 #ifndef AOUT_STANDALONE
 143   seg   cs
 144   cmp   [dos_flag],#0   ! Should we do a DOS exit
 145   je    do_reboot
 146   mov   ax,#$4c00
 147   int   $21
 148 do_reboot:
 149 #endif
 150   xor   ax,ax
 151   mov   ds,ax
 152   mov   ax,cs
 153   mov   [$E6*4+2],ax
 154   mov   ax,#iret_ins
 155   mov   [$E6*4],ax
 156   mov   ax,#$FFFF
 157   int   $E6             ! Try to exit DOSEMU
 158                         ! If we get here we`re not in dosemu.
 159   mov   [$472],#$1234   ! Warm reboot.
 160   jmpi  $0000,$FFFF
 161 iret_ins:
 162   iret
 163
 164 #endasm
 165
 166 #endif
 167
 168 /****************************************************************************/
 169
 170 #ifdef L_bios_write
 171 write(fd,buf,len)
 172 int fd,len;
 173 char * buf;
 174 {
 175    register int v, c;
 176    if(fd == 1 || fd == 2)
 177    {
 178       for(v=len; v>0; v--)
 179       {
 180          c= *buf++;
 181          putch(c);
 182       }
 183       return len;
 184    }
 185    return (*__files)(CMD_WRITE, fd, buf, len);
 186 }
 187 #endif
 188
 189 /****************************************************************************/
 190
 191 #ifdef L_bios_read
 192 read(fd,buf,len)
 193 int fd,len;
 194 char * buf;
 195 {
 196    if(fd == 0) return bios_rdline(buf, len);
 197    return (*__files)(CMD_READ, fd, buf, len);
 198 }
 199 #endif
 200
 201 /****************************************************************************/
 202
 203 #ifdef L_bios_lseek
 204 long
 205 lseek(fd, offt, whence)
 206 int fd, whence;
 207 long offt;
 208 {
 209    if( fd >= 0 && fd <= 2 ) errno = ESPIPE;
 210    else
 211    {
 212       if( (*__files)(CMD_LSEEK, fd, &offt, whence) >= 0 )
 213          return offt;
 214    }
 215    return -1L;
 216 }
 217 #endif
 218
 219 /****************************************************************************/
 220
 221 #ifdef L_bios_close
 222 close(fd)
 223 int fd;
 224 {
 225    if( fd >= 0 && fd <= 2 ) errno = ENOSYS;
 226    else
 227       return (*__files)(CMD_CLOSE, fd);
 228    return -1;
 229 }
 230 #endif
 231
 232 /****************************************************************************/
 233
 234 #ifdef L_bios_nofiles
 235 int (*__files)() = __nofiles;
 236
 237 int __nofiles(cmd, fd, buf, len)
 238 int cmd, fd, len;
 239 char * buf;
 240 {
 241    errno = EBADF;
 242    return -1;
 243 }
 244
 245 #endif
 246
 247 /****************************************************************************/
 248
 249 #ifdef L_bios_isatty
 250 isatty(fd)
 251 int fd;
 252 {
 253    if( fd >= 0 && fd <= 2 ) return 1;
 254    return 0;
 255 }
 256 #endif
 257
 258 /****************************************************************************/
 259
 260 #ifdef L_bios_abort
 261 abort()
 262 {
 263    static const char msg[] = "Program aborted, press return:";
 264    write(2, msg, sizeof(msg)-1);
 265    getch();
 266    _exit(255);
 267 }
 268
 269 #endif
 270
 271 /****************************************************************************/
 272
 273 #endif
 274 #endif
 275 #endif