loader/i386/pc/chainloader.c

   1 /* chainloader.c - boot another boot loader */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002,2004,2007  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/loader.h>
  21 #include <grub/machine/loader.h>
  22 #include <grub/machine/chainloader.h>
  23 #include <grub/file.h>
  24 #include <grub/err.h>
  25 #include <grub/device.h>
  26 #include <grub/disk.h>
  27 #include <grub/misc.h>
  28 #include <grub/types.h>
  29 #include <grub/machine/init.h>
  30 #include <grub/partition.h>
  31 #include <grub/machine/memory.h>
  32 #include <grub/dl.h>
  33 #include <grub/command.h>
  34
  35 static grub_dl_t my_mod;
  36 static int boot_drive;
  37 static void *boot_part_addr;
  38
  39 static grub_err_t
  40 grub_chainloader_boot (void)
  41 {
  42   grub_chainloader_real_boot (boot_drive, boot_part_addr);
  43
  44   /* Never reach here.  */
  45   return GRUB_ERR_NONE;
  46 }
  47
  48 static grub_err_t
  49 grub_chainloader_unload (void)
  50 {
  51   grub_dl_unref (my_mod);
  52   return GRUB_ERR_NONE;
  53 }
  54
  55 static void
  56 grub_chainloader_cmd (const char *filename, grub_chainloader_flags_t flags)
  57 {
  58   grub_file_t file = 0;
  59   grub_uint16_t signature;
  60   grub_device_t dev;
  61   int drive = -1;
  62   void *part_addr = 0;
  63
  64   grub_dl_ref (my_mod);
  65
  66   file = grub_file_open (filename);
  67   if (! file)
  68     goto fail;
  69
  70   /* Read the first block.  */
  71   if (grub_file_read (file, (char *) 0x7C00, GRUB_DISK_SECTOR_SIZE)
  72       != GRUB_DISK_SECTOR_SIZE)
  73     {
  74       if (grub_errno == GRUB_ERR_NONE)
  75         grub_error (GRUB_ERR_BAD_OS, "too small");
  76
  77       goto fail;
  78     }
  79
  80   /* Check the signature.  */
  81   signature = *((grub_uint16_t *) (0x7C00 + GRUB_DISK_SECTOR_SIZE - 2));
  82   if (signature != grub_le_to_cpu16 (0xaa55)
  83       && ! (flags & GRUB_CHAINLOADER_FORCE))
  84     {
  85       grub_error (GRUB_ERR_BAD_OS, "invalid signature");
  86       goto fail;
  87     }
  88
  89   grub_file_close (file);
  90
  91   /* Obtain the partition table from the root device.  */
  92   dev = grub_device_open (0);
  93   if (dev)
  94     {
  95       grub_disk_t disk = dev->disk;
  96
  97       if (disk)
  98         {
  99           grub_partition_t p = disk->partition;
 100
 101           /* In i386-pc, the id is equal to the BIOS drive number.  */
 102           drive = (int) disk->id;
 103
 104           if (p)
 105             {
 106               grub_disk_read (disk, p->offset, 446, 64,
 107                               (void *) GRUB_MEMORY_MACHINE_PART_TABLE_ADDR);
 108               part_addr = (void *) (GRUB_MEMORY_MACHINE_PART_TABLE_ADDR
 109                                     + (p->index << 4));
 110             }
 111         }
 112
 113       grub_device_close (dev);
 114     }
 115
 116   /* Ignore errors. Perhaps it's not fatal.  */
 117   grub_errno = GRUB_ERR_NONE;
 118
 119   boot_drive = drive;
 120   boot_part_addr = part_addr;
 121
 122   grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 1);
 123   return;
 124
 125  fail:
 126
 127   if (file)
 128     grub_file_close (file);
 129
 130   grub_dl_unref (my_mod);
 131 }
 132
 133 static grub_err_t
 134 grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
 135                       int argc, char *argv[])
 136 {
 137   grub_chainloader_flags_t flags = 0;
 138
 139   if (argc > 0 && grub_strcmp (argv[0], "--force") == 0)
 140     {
 141       flags |= GRUB_CHAINLOADER_FORCE;
 142       argc--;
 143       argv++;
 144     }
 145
 146   if (argc == 0)
 147     return grub_error (GRUB_ERR_BAD_ARGUMENT, "no file specified");
 148   else
 149     grub_chainloader_cmd (argv[0], flags);
 150
 151   return grub_errno;
 152 }
 153
 154 static grub_command_t cmd;
 155
 156 GRUB_MOD_INIT(chainloader)
 157 {
 158   cmd = grub_register_command ("chainloader", grub_cmd_chainloader,
 159                                0, "load another boot loader");
 160   my_mod = mod;
 161 }
 162
 163 GRUB_MOD_FINI(chainloader)
 164 {
 165   grub_unregister_command (cmd);
 166 }