boot.c

GRUB 0.93的源代码。有人说可以当一个很小的操作系统了

/* boot.c - load and bootstrap a kernel */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999,2000,2001,2002  Free Software Foundation, Inc.
 *
 *  This program 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 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


#include "shared.h"

#include "freebsd.h"
#include "imgact_aout.h"
#include "i386-elf.h"

static int cur_addr;
entry_func entry_addr;
static struct mod_list mll[99];
static int linux_mem_size;

/*
 *  The next two functions, 'load_image' and 'load_module', are the building
 *  blocks of the multiboot loader component.  They handle essentially all
 *  of the gory details of loading in a bootable image and the modules.
 */

kernel_t
load_image (char *kernel, char *arg, kernel_t suggested_type,
	    unsigned long load_flags)
{
  int len, i, exec_type = 0, align_4k = 1;
  entry_func real_entry_addr = 0;
  kernel_t type = KERNEL_TYPE_NONE;
  unsigned long flags = 0, text_len = 0, data_len = 0, bss_len = 0;
  char *str = 0, *str2 = 0;
  struct linux_kernel_header *lh;
  union
    {
      struct multiboot_header *mb;
      struct exec *aout;
      Elf32_Ehdr *elf;
    }
  pu;
  /* presuming that MULTIBOOT_SEARCH is large enough to encompass an
     executable header */
  unsigned char buffer[MULTIBOOT_SEARCH];

  /* sets the header pointer to point to the beginning of the
     buffer by default */
  pu.aout = (struct exec *) buffer;

  if (!grub_open (kernel))
    return KERNEL_TYPE_NONE;

  if (!(len = grub_read (buffer, MULTIBOOT_SEARCH)) || len < 32)
    {
      grub_close ();
      
      if (!errnum)
	errnum = ERR_EXEC_FORMAT;

      return KERNEL_TYPE_NONE;
    }

  for (i = 0; i < len; i++)
    {
      if (MULTIBOOT_FOUND ((int) (buffer + i), len - i))
	{
	  flags = ((struct multiboot_header *) (buffer + i))->flags;
	  if (flags & MULTIBOOT_UNSUPPORTED)
	    {
	      grub_close ();
	      errnum = ERR_BOOT_FEATURES;
	      return KERNEL_TYPE_NONE;
	    }
	  type = KERNEL_TYPE_MULTIBOOT;
	  str2 = "Multiboot";
	  break;
	}
    }

  /* Use BUFFER as a linux kernel header, if the image is Linux zImage
     or bzImage.  */
  lh = (struct linux_kernel_header *) buffer;
  
  /* ELF loading supported if multiboot, FreeBSD and NetBSD.  */
  if ((type == KERNEL_TYPE_MULTIBOOT
       || pu.elf->e_ident[EI_OSABI] == ELFOSABI_FREEBSD
       || grub_strcmp (pu.elf->e_ident + EI_BRAND, "FreeBSD") == 0
       || suggested_type == KERNEL_TYPE_NETBSD)
      && len > sizeof (Elf32_Ehdr)
      && BOOTABLE_I386_ELF ((*((Elf32_Ehdr *) buffer))))
    {
      if (type == KERNEL_TYPE_MULTIBOOT)
	entry_addr = (entry_func) pu.elf->e_entry;
      else
	entry_addr = (entry_func) (pu.elf->e_entry & 0xFFFFFF);

      if (entry_addr < (entry_func) 0x100000)
	errnum = ERR_BELOW_1MB;

      /* don't want to deal with ELF program header at some random
         place in the file -- this generally won't happen */
      if (pu.elf->e_phoff == 0 || pu.elf->e_phnum == 0
	  || ((pu.elf->e_phoff + (pu.elf->e_phentsize * pu.elf->e_phnum))
	      >= len))
	errnum = ERR_EXEC_FORMAT;
      str = "elf";

      if (type == KERNEL_TYPE_NONE)
	{
	  /* At the moment, there is no way to identify a NetBSD ELF
	     kernel, so rely on the suggested type by the user.  */
	  if (suggested_type == KERNEL_TYPE_NETBSD)
	    {
	      str2 = "NetBSD";
	      type = suggested_type;
	    }
	  else
	    {
	      str2 = "FreeBSD";
	      type = KERNEL_TYPE_FREEBSD;
	    }
	}
    }
  else if (flags & MULTIBOOT_AOUT_KLUDGE)
    {
      pu.mb = (struct multiboot_header *) (buffer + i);
      entry_addr = (entry_func) pu.mb->entry_addr;
      cur_addr = pu.mb->load_addr;
      /* first offset into file */
      grub_seek (i - (pu.mb->header_addr - cur_addr));

      /* If the load end address is zero, load the whole contents.  */
      if (! pu.mb->load_end_addr)
	pu.mb->load_end_addr = cur_addr + filemax;
      
      text_len = pu.mb->load_end_addr - cur_addr;
      data_len = 0;

      /* If the bss end address is zero, assume that there is no bss area.  */
      if (! pu.mb->bss_end_addr)
	pu.mb->bss_end_addr = pu.mb->load_end_addr;
      
      bss_len = pu.mb->bss_end_addr - pu.mb->load_end_addr;

      if (pu.mb->header_addr < pu.mb->load_addr
	  || pu.mb->load_end_addr <= pu.mb->load_addr
	  || pu.mb->bss_end_addr < pu.mb->load_end_addr
	  || (pu.mb->header_addr - pu.mb->load_addr) > i)
	errnum = ERR_EXEC_FORMAT;

      if (cur_addr < 0x100000)
	errnum = ERR_BELOW_1MB;

      pu.aout = (struct exec *) buffer;
      exec_type = 2;
      str = "kludge";
    }
  else if (len > sizeof (struct exec) && !N_BADMAG ((*(pu.aout))))
    {
      entry_addr = (entry_func) pu.aout->a_entry;

      if (type == KERNEL_TYPE_NONE)
	{
	  /*
	   *  If it doesn't have a Multiboot header, then presume
	   *  it is either a FreeBSD or NetBSD executable.  If so,
	   *  then use a magic number of normal ordering, ZMAGIC to
	   *  determine if it is FreeBSD.
	   *
	   *  This is all because freebsd and netbsd seem to require
	   *  masking out some address bits...  differently for each
	   *  one...  plus of course we need to know which booting
	   *  method to use.
	   */
	  entry_addr = (entry_func) ((int) entry_addr & 0xFFFFFF);
	  
	  if (buffer[0] == 0xb && buffer[1] == 1)
	    {
	      type = KERNEL_TYPE_FREEBSD;
	      cur_addr = (int) entry_addr;
	      str2 = "FreeBSD";
	    }
	  else
	    {
	      type = KERNEL_TYPE_NETBSD;
	      cur_addr = (int) entry_addr & 0xF00000;
	      if (N_GETMAGIC ((*(pu.aout))) != NMAGIC)
		align_4k = 0;
	      str2 = "NetBSD";
	    }
	}

      /* first offset into file */
      grub_seek (N_TXTOFF (*(pu.aout)));
      text_len = pu.aout->a_text;
      data_len = pu.aout->a_data;
      bss_len = pu.aout->a_bss;

      if (cur_addr < 0x100000)
	errnum = ERR_BELOW_1MB;

      exec_type = 1;
      str = "a.out";
    }
  else if (lh->boot_flag == BOOTSEC_SIGNATURE
	   && lh->setup_sects <= LINUX_MAX_SETUP_SECTS)
    {
      int big_linux = 0;
      int setup_sects = lh->setup_sects;

      if (lh->header == LINUX_MAGIC_SIGNATURE && lh->version >= 0x0200)
	{
	  big_linux = (lh->loadflags & LINUX_FLAG_BIG_KERNEL);
	  lh->type_of_loader = LINUX_BOOT_LOADER_TYPE;

	  /* Put the real mode part at as a high location as possible.  */
	  linux_data_real_addr
	    = (char *) ((mbi.mem_lower << 10) - LINUX_SETUP_MOVE_SIZE);
	  /* But it must not exceed the traditional area.  */
	  if (linux_data_real_addr > (char *) LINUX_OLD_REAL_MODE_ADDR)
	    linux_data_real_addr = (char *) LINUX_OLD_REAL_MODE_ADDR;

	  if (lh->version >= 0x0201)
	    {
	      lh->heap_end_ptr = LINUX_HEAP_END_OFFSET;
	      lh->loadflags |= LINUX_FLAG_CAN_USE_HEAP;
	    }

	  if (lh->version >= 0x0202)
	    lh->cmd_line_ptr = linux_data_real_addr + LINUX_CL_OFFSET;
	  else
	    {
	      lh->cl_magic = LINUX_CL_MAGIC;
	      lh->cl_offset = LINUX_CL_OFFSET;
	      lh->setup_move_size = LINUX_SETUP_MOVE_SIZE;
	    }
	}
      else
	{
	  /* Your kernel is quite old...  */
	  lh->cl_magic = LINUX_CL_MAGIC;
	  lh->cl_offset = LINUX_CL_OFFSET;
	  
	  setup_sects = LINUX_DEFAULT_SETUP_SECTS;

	  linux_data_real_addr = (char *) LINUX_OLD_REAL_MODE_ADDR;
	}
      
      /* If SETUP_SECTS is not set, set it to the default (4).  */
      if (! setup_sects)
	setup_sects = LINUX_DEFAULT_SETUP_SECTS;

      data_len = setup_sects << 9;
      text_len = filemax - data_len - SECTOR_SIZE;

      linux_data_tmp_addr = (char *) LINUX_BZIMAGE_ADDR + text_len;
      
      if (! big_linux
	  && text_len > linux_data_real_addr - (char *) LINUX_ZIMAGE_ADDR)
	{
	  grub_printf (" linux 'zImage' kernel too big, try 'make bzImage'\n");
	  errnum = ERR_WONT_FIT;
	}
      else if (linux_data_real_addr + LINUX_SETUP_MOVE_SIZE
	       > RAW_ADDR ((char *) (mbi.mem_lower << 10)))
	errnum = ERR_WONT_FIT;
      else
	{
	  grub_printf ("   [Linux-%s, setup=0x%x, size=0x%x]\n",
		       (big_linux ? "bzImage" : "zImage"), data_len, text_len);

	  /* Video mode selection support. What a mess!  */
	  /* NOTE: Even the word "mess" is not still enough to
	     represent how wrong and bad the Linux video support is,
	     but I don't want to hear complaints from Linux fanatics
	     any more. -okuji  */
	  {
	    char *vga;
	
	    /* Find the substring "vga=".  */
	    vga = grub_strstr (arg, "vga=");
	    if (vga)
	      {
		char *value = vga + 4;
		int vid_mode;
	    
		/* Handle special strings.  */
		if (substring ("normal", value) < 1)
		  vid_mode = LINUX_VID_MODE_NORMAL;
		else if (substring ("ext", value) < 1)
		  vid_mode = LINUX_VID_MODE_EXTENDED;
		else if (substring ("ask", value) < 1)
		  vid_mode = LINUX_VID_MODE_ASK;
		else if (safe_parse_maxint (&value, &vid_mode))
		  ;
		else
		  {
		    /* ERRNUM is already set inside the function
		       safe_parse_maxint.  */
		    grub_close ();
		    return KERNEL_TYPE_NONE;
		  }
	    
		lh->vid_mode = vid_mode;
	      }
	  }

	  /* Check the mem= option to limit memory used for initrd.  */
	  {
	    char *mem;
	
	    mem = grub_strstr (arg, "mem=");
	    if (mem)
	      {
		char *value = mem + 4;
	    
		safe_parse_maxint (&value, &linux_mem_size);
		switch (errnum)
		  {
		  case ERR_NUMBER_OVERFLOW:
		    /* If an overflow occurs, use the maximum address for
		       initrd instead. This is good, because MAXINT is
		       greater than LINUX_INITRD_MAX_ADDRESS.  */
		    linux_mem_size = LINUX_INITRD_MAX_ADDRESS;
		    errnum = ERR_NONE;
		    break;
		
		  case ERR_NONE:
		    {
		      int shift = 0;
		  
		      switch (grub_tolower (*value))
			{
			case 'g':
			  shift += 10;
			case 'm':
			  shift += 10;
			case 'k':
			  shift += 10;
			default:
			  break;
			}
		  
		      /* Check an overflow.  */
		      if (linux_mem_size > (MAXINT >> shift))
			linux_mem_size = LINUX_INITRD_MAX_ADDRESS;
		      else
			linux_mem_size <<= shift;
		    }
		    break;
		
		  default:
		    linux_mem_size = 0;
		    errnum = ERR_NONE;
		    break;
		  }
	      }
	    else
	      linux_mem_size = 0;
	  }
      
	  /* It is possible that DATA_LEN is greater than MULTIBOOT_SEARCH,
	     so the data may have been read partially.  */
	  if (data_len <= MULTIBOOT_SEARCH)
	    grub_memmove (linux_data_tmp_addr, buffer,
			  data_len + SECTOR_SIZE);
	  else
	    {
	      grub_memmove (linux_data_tmp_addr, buffer, MULTIBOOT_SEARCH);
	      grub_read (linux_data_tmp_addr + MULTIBOOT_SEARCH,
			 data_len + SECTOR_SIZE - MULTIBOOT_SEARCH);
	    }
	  
	  if (lh->header != LINUX_MAGIC_SIGNATURE ||
	      lh->version < 0x0200)
	    /* Clear the heap space.  */
	    grub_memset (linux_data_tmp_addr + ((setup_sects + 1) << 9),
			 0,
			 (64 - setup_sects - 1) << 9);
      
	  /* Copy command-line plus memory hack to staging area.
	     NOTE: Linux has a bug that it doesn't handle multiple spaces
	     between two options and a space after a "mem=" option isn't
	     removed correctly so the arguments to init could be like
	     {"init", "", "", NULL}. This affects some not-very-clever
	     shells. Thus, the code below does a trick to avoid the bug.
	     That is, copy "mem=XXX" to the end of the command-line, and
	     avoid to copy spaces unnecessarily. Hell.  */
	  {
	    char *src = skip_to (0, arg);
	    char *dest = linux_data_tmp_addr + LINUX_CL_OFFSET;
	
	    while (dest < linux_data_tmp_addr + LINUX_CL_END_OFFSET && *src)
	      *(dest++) = *(src++);
	
	    /* Add a mem option automatically only if the user doesn't
	       specify it explicitly.  */
	    if (! grub_strstr (arg, "mem=")
		&& ! (load_flags & KERNEL_LOAD_NO_MEM_OPTION)
		&& dest + 15 < linux_data_tmp_addr + LINUX_CL_END_OFFSET)
	      {
		*dest++ = ' ';
		*dest++ = 'm';
		*dest++ = 'e';
		*dest++ = 'm';
		*dest++ = '=';
	    
		dest = convert_to_ascii (dest, 'u', (extended_memory + 0x400));
		*dest++ = 'K';
	      }
	
	    *dest = 0;
	  }
      
	  /* offset into file */
	  grub_seek (data_len + SECTOR_SIZE);
      
	  cur_addr = (int) linux_data_tmp_addr + LINUX_SETUP_MOVE_SIZE;
	  grub_read ((char *) LINUX_BZIMAGE_ADDR, text_len);
      
	  if (errnum == ERR_NONE)
	    {
	      grub_close ();
	  
	      /* Sanity check.  */
	      if (suggested_type != KERNEL_TYPE_NONE
		  && ((big_linux && suggested_type != KERNEL_TYPE_BIG_LINUX)
		      || (! big_linux && suggested_type != KERNEL_TYPE_LINUX)))
		{
		  errnum = ERR_EXEC_FORMAT;
		  return KERNEL_TYPE_NONE;
		}
	  
	      /* Ugly hack.  */
	      linux_text_len = text_len;
	  
	      return big_linux ? KERNEL_TYPE_BIG_LINUX : KERNEL_TYPE_LINUX;
	    }
	}
    }
  else				/* no recognizable format */
    errnum = ERR_EXEC_FORMAT;

  /* return if error */
  if (errnum)
    {
      grub_close ();
      return KERNEL_TYPE_NONE;
    }

  /* fill the multiboot info structure */
  mbi.cmdline = (int) arg;
  mbi.mods_count = 0;
  mbi.mods_addr = 0;
  mbi.boot_device = (current_drive << 24) | current_partition;
  mbi.flags &= ~(MB_INFO_MODS | MB_INFO_AOUT_SYMS | MB_INFO_ELF_SHDR);
  mbi.syms.a.tabsize = 0;
  mbi.syms.a.strsize = 0;
  mbi.syms.a.addr = 0;
  mbi.syms.a.pad = 0;

  printf ("   [%s-%s", str2, str);

  str = "";

  if (exec_type)		/* can be loaded like a.out */
    {
      if (flags & MULTIBOOT_AOUT_KLUDGE)
	str = "-and-data";

      printf (", loadaddr=0x%x, text%s=0x%x", cur_addr, str, text_len);

      /* read text, then read data */
      if (grub_read ((char *) RAW_ADDR (cur_addr), text_len) == text_len)
	{
	  cur_addr += text_len;

	  if (!(flags & MULTIBOOT_AOUT_KLUDGE))
	    {
	      /* we have to align to a 4K boundary */
	      if (align_4k)
		cur_addr = (cur_addr + 0xFFF) & 0xFFFFF000;
	      else
		printf (", C");

	      printf (", data=0x%x", data_len);

	      if ((grub_read ((char *) RAW_ADDR (cur_addr), data_len)