sample/fd.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2003-2008 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * fd.c
  15  *
  16  * Chainload a floppy disk (currently rather braindead.)
  17  */
  18
  19 #include <com32.h>
  20 #define NULL ((void *)0)
  21
  22 int printf(const char *, ...);
  23 unsigned int atou(const char *);
  24
  25 int __start(void)
  26 {
  27   int whichfd = atou(__com32.cs_cmdline);
  28   static com32sys_t inreg, outreg; /* In bss, so zeroed automatically */
  29   int retry;
  30
  31   for ( retry = 0 ; retry < 6 ; retry++ ) {
  32     printf(">");
  33     inreg.eax.w[0] = 0x0201;    /* Read one sector */
  34     inreg.ecx.w[0] = 0x0001;    /* Cyl 0 sector 1 */
  35     inreg.edx.b[1] = 0;         /* Head 0 */
  36     inreg.edx.b[0] = whichfd;   /* Drive number */
  37     inreg.es = SEG(__com32.cs_bounce); /* Read into the bounce buffer */
  38     inreg.ebx.w[0] = OFFS(__com32.cs_bounce);
  39     __com32.cs_intcall(0x13, &inreg, &outreg);
  40
  41     if ( (outreg.eflags.l & 1) == 0 )
  42       break;
  43   }
  44
  45   if ( (outreg.eflags.l & 1) == 0 ) {
  46     printf("!\n");
  47     inreg.eax.w[0] = 0x000d;
  48     inreg.edx.w[0] = 0;
  49     inreg.edi.l    = (uint32_t) __com32.cs_bounce;
  50     inreg.ecx.l    = 512;
  51     inreg.ebx.l    = whichfd & 0xff;
  52     inreg.esi.l    = 0;         /* No partitions */
  53     inreg.ds       = 0;         /* No partitions */
  54     __com32.cs_intcall(0x22, &inreg, NULL);
  55   }
  56
  57   /* If we get here, badness happened */
  58   return 255;
  59 }