cmain.c

有助于了解操作系统如何启动之过程

/* cmain.c - Startup code for the PowerPC.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2003,2004,2005,2006,2007,2008  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <alloca.h>
#include <stdint.h>
#include <grub/kernel.h>
#include <grub/misc.h>
#include <grub/types.h>
#include <grub/machine/kernel.h>
#include <grub/ieee1275/ieee1275.h>

int (*grub_ieee1275_entry_fn) (void *);

grub_ieee1275_phandle_t grub_ieee1275_chosen;
grub_ieee1275_ihandle_t grub_ieee1275_mmu;

static grub_uint32_t grub_ieee1275_flags;



int
grub_ieee1275_test_flag (enum grub_ieee1275_flag flag)
{
  return (grub_ieee1275_flags & (1 << flag));
}

void
grub_ieee1275_set_flag (enum grub_ieee1275_flag flag)
{
  grub_ieee1275_flags |= (1 << flag);
}

#define SF "SmartFirmware(tm)"
#define OHW "PPC Open Hack'Ware"

static void
grub_ieee1275_find_options (void)
{
  grub_ieee1275_phandle_t root;
  grub_ieee1275_phandle_t options;
  grub_ieee1275_phandle_t openprom;
  grub_ieee1275_phandle_t bootrom;
  int rc;
  int realmode = 0;
  char tmp[32];
  int is_smartfirmware = 0;
  int is_olpc = 0;

  grub_ieee1275_finddevice ("/", &root);
  grub_ieee1275_finddevice ("/options", &options);
  grub_ieee1275_finddevice ("/openprom", &openprom);

  rc = grub_ieee1275_get_integer_property (options, "real-mode?", &realmode,
					   sizeof realmode, 0);
  if (((rc >= 0) && realmode) || (grub_ieee1275_mmu == 0))
    grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_REAL_MODE);

  rc = grub_ieee1275_get_property (openprom, "CodeGen-copyright",
				   tmp,	sizeof (tmp), 0);
  if (rc >= 0 && !grub_strncmp (tmp, SF, sizeof (SF) - 1))
    is_smartfirmware = 1;

  rc = grub_ieee1275_get_property (root, "architecture",
				   tmp,	sizeof (tmp), 0);
  if (rc >= 0 && !grub_strcmp (tmp, "OLPC"))
    is_olpc = 1;

  if (is_smartfirmware)
    {
      /* Broken in all versions */
      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_BROKEN_OUTPUT);

      /* There are two incompatible ways of checking the version number.  Try
         both. */
      rc = grub_ieee1275_get_property (openprom, "SmartFirmware-version",
				       tmp, sizeof (tmp), 0);
      if (rc < 0)
	rc = grub_ieee1275_get_property (openprom, "firmware-version",
					 tmp, sizeof (tmp), 0);
      if (rc >= 0)
	{
	  /* It is tempting to implement a version parser to set the flags for
	     e.g. 1.3 and below.  However, there's a special situation here.
	     3rd party updates which fix the partition bugs are common, and for
	     some reason their fixes aren't being merged into trunk.  So for
	     example we know that 1.2 and 1.3 are broken, but there's 1.2.99
	     and 1.3.99 which are known good (and applying this workaround
	     would cause breakage). */
	  if (!grub_strcmp (tmp, "1.0")
	      || !grub_strcmp (tmp, "1.1")
	      || !grub_strcmp (tmp, "1.2")
	      || !grub_strcmp (tmp, "1.3"))
	    {
	      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_NO_PARTITION_0);
	      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_0_BASED_PARTITIONS);
	    }
	}
    }

  if (is_olpc)
    {
      /* OLPC / XO laptops have three kinds of storage devices:

	 - NAND flash.  These are accessible via OFW callbacks, but:
	   - Follow strange semantics, imposed by hardware constraints.
	   - Its ABI is undocumented, and not stable.
	   They lack "device_type" property, which conveniently makes GRUB
	   skip them.

	 - USB drives.  Not accessible, because OFW shuts down the controller
	   in order to prevent collisions with applications accessing it
	   directly.  Even worse, attempts to access it will NOT return
	   control to the caller, so we have to avoid probing them.

	 - SD cards.  These work fine.

	 To avoid brekage, we only need to skip USB probing.  However,
	 since detecting SD cards is more reliable, we do that instead.
      */

      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY);
    }

  if (! grub_ieee1275_finddevice ("/rom/boot-rom", &bootrom))
    {
      rc = grub_ieee1275_get_property (bootrom, "model", tmp, sizeof (tmp), 0);
      if (rc >= 0 && !grub_strncmp (tmp, OHW, sizeof (OHW) - 1))
	{
	  grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_BROKEN_OUTPUT);
	  grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_CANNOT_SET_COLORS);
	}
    }
}

#undef SF
#undef OHW

void cmain (void);
void
cmain (void)
{
  grub_ieee1275_finddevice ("/chosen", &grub_ieee1275_chosen);

  if (grub_ieee1275_get_integer_property (grub_ieee1275_chosen, "mmu", &grub_ieee1275_mmu,
					  sizeof grub_ieee1275_mmu, 0) < 0)
    grub_ieee1275_mmu = 0;

  grub_ieee1275_find_options ();

  /* Now invoke the main function.  */
  grub_main ();

  /* Never reached.  */
}