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 }