com32/modules/ifplop.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2010 Gert Hulselmans - 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., 51 Franklin St, Fifth Floor,
   8  *   Boston MA 02110-1301, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * ifplop.c
  15  *
  16  * This COM32 module detects if the PLoP Boot Manager was used to boot a CDROM
  17  * drive or USB drive, by checking for the presence of the PLoP INT13h hook.
  18  *
  19  * Usage:    ifplop.c32 [<plop_detected>] -- [<plop_not_detected>]
  20  * Examples: ifplop.c32 menu.c32 another.cfg -- plpbt hiddenusb usb1=2
  21  *              You need to remove the ".bin" extension of the plpbt.bin file
  22  *              if you use it this way.
  23  *           ifplop.c32 plop_detected -- plop_not_detected
  24  *
  25  * A possible config file could be:
  26  *
  27  * ===========================================================================
  28  *  DEFAULT plopcheck
  29  *
  30  *  # Check for the presence of PLoP (run by default)
  31  *  #   When PLoP INT13h hook is found, run the first command (plop_detected)
  32  *  #   When PLoP INT13h hook isn't found, run the second command (plop_not_detected)
  33  *  LABEL plopcheck
  34  *      COM32 ifplop.c32
  35  *      APPEND plop_detected -- plop_not_detected
  36  *
  37  *  # When PLoP INT13h hook was found, boot the menu system.
  38  *  # PLoP can have added USB 2.0 speed, so the entries we want to boot
  39  *  # will be read from disk much faster (supposing that we have a BIOS
  40  *  # that only supports USB 1.1 speed, but a mobo with USB 2.0 controllers).
  41  *  LABEL plop_detected
  42  *      COM32 menu.c32
  43  *      APPEND another.cfg
  44  *
  45  *  # PLoP INT13h hook wasn't found, so we boot PLoP, so it can add USB 2.0 support
  46  *  # When using "LINUX plpbt.bin", you don't need to remove the .bin extension.
  47  *  LABEL plop_not_detected
  48  *      LINUX plpbt.bin
  49  *      APPEND hiddenusb usb1=2
  50  *
  51  * ===========================================================================
  52  *
  53  * Why is/can this module be useful?
  54  *
  55  * You may want to boot PLoP by default from Syslinux when you boot from your
  56  * USB stick/drive:
  57  *   1. PLoP can upgrade USB 1.1 speed offered by the BIOS to USB 2.0 speed
  58  *      if you have USB 2.0 controllers on your mobo.
  59  *   2. Some BIOSes only can access the first 128GiB (137GB) on USB drives, while
  60  *      internal hard drives don't necessarily suffer from this 128GiB problem.
  61  *      Using PLoPs USB capabilities, you can access the whole drive.
  62  *
  63  * When you select the "USB" entry in PLoP, it will boot your USB stick/drive
  64  * again and it will boot PLoP again when you have set booting PLoP as DEFAULT
  65  * boot option in your Syslinux configuration file.
  66  *
  67  * By using ifplop.c32 you can specify which action you want to do the second
  68  * time your USB stick/drive is booted. So you can load another config file or
  69  * boot a large hard disk image or whatever you want.
  70  *
  71  * PLoP Boot Manager website: http://www.plop.at/en/bootmanager.html
  72  */
  73
  74 #include <com32.h>
  75 #include <stdlib.h>
  76 #include <stdio.h>
  77 #include <string.h>
  78 #include <alloca.h>
  79 #include <console.h>
  80 #include <syslinux/boot.h>
  81
  82 static bool plop_INT13h_check(void)
  83 {
  84     com32sys_t inregs, outregs;
  85
  86     /* Prepare the register set */
  87     memset(&inregs, 0, sizeof inregs);
  88
  89     /*
  90      * Check if PLoP already has booted a CDROM or USB drive by checking
  91      * for the presence of the PLoP INT13h hook.
  92      *
  93      * The following assembly code (NASM) can detect the PLoP INT13h hook:
  94      *
  95      *   mov eax,'PoLP'  ; Reverse of 'PLoP'
  96      *   mov ebp,'DKHC'  ; Reverse of 'CHKD'
  97      *   int 13h
  98      *   cmp eax,' sey'  ; Reverse of 'yes '
  99      *   jz plop_INT13h_active
 100      */
 101
 102     inregs.eax.l = 0x504c6f50;  /* "PLoP" */
 103     inregs.ebp.l = 0x43484b44;  /* "CHKD" */
 104
 105     __intcall(0x13, &inregs, &outregs);
 106
 107     /* eax will contain "yes " if PLoP INT13h hook is available */
 108     if (outregs.eax.l == 0x79657320)
 109         return true;
 110
 111     return false;
 112 }
 113
 114 /* XXX: this really should be librarized */
 115 static void boot_args(char **args)
 116 {
 117     int len = 0, a = 0;
 118     char **pp;
 119     const char *p;
 120     char c, *q, *str;
 121
 122     for (pp = args; *pp; pp++)
 123         len += strlen(*pp) + 1;
 124
 125     q = str = alloca(len);
 126     for (pp = args; *pp; pp++) {
 127         p = *pp;
 128         while ((c = *p++))
 129             *q++ = c;
 130         *q++ = ' ';
 131         a = 1;
 132     }
 133     q -= a;
 134     *q = '\0';
 135
 136     if (!str[0])
 137         syslinux_run_default();
 138     else
 139         syslinux_run_command(str);
 140 }
 141
 142 int main(int argc, char *argv[])
 143 {
 144     char **args[2];
 145     int arg = 0;
 146
 147     if (argc)
 148         arg++;
 149     args[0] = &argv[arg];
 150     args[1] = NULL;
 151     while (arg < argc) {
 152         if (!strcmp(argv[arg], "--")) {
 153             argv[arg] = NULL;
 154             args[1] = &argv[arg + 1];
 155             break;
 156         }
 157         arg++;
 158     }
 159     if (args[1] != NULL) {
 160         boot_args(plop_INT13h_check()? args[0] : args[1]);
 161     } else {
 162         fprintf(stderr,
 163                 "Usage:   ifplop.c32 [<plop_detected>] -- [<plop_not_detected>]\n"
 164                 "Example: ifplop.c32 menu.c32 another.cfg -- plpbt hiddenusb usb1=2\n");
 165     }
 166
 167     return 0;
 168 }