fsys_ext2fs.c

i386的bootloader源码grub

/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999, 2001, 2003  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.
 */

#ifdef FSYS_EXT2FS

#include "shared.h"
#include "filesys.h"

static int mapblock1, mapblock2;

/* sizes are always in bytes, BLOCK values are always in DEV_BSIZE (sectors) */
#define DEV_BSIZE 512

/* include/linux/fs.h */
#define BLOCK_SIZE 1024		/* initial block size for superblock read */
/* made up, defaults to 1 but can be passed via mount_opts */
#define WHICH_SUPER 1
/* kind of from fs/ext2/super.c */
#define SBLOCK (WHICH_SUPER * BLOCK_SIZE / DEV_BSIZE)	/* = 2 */

/* include/asm-i386/types.h */
typedef __signed__ char __s8;
typedef unsigned char __u8;
typedef __signed__ short __s16;
typedef unsigned short __u16;
typedef __signed__ int __s32;
typedef unsigned int __u32;

/*
 * Constants relative to the data blocks, from ext2_fs.h
 */
#define EXT2_NDIR_BLOCKS                12
#define EXT2_IND_BLOCK                  EXT2_NDIR_BLOCKS
#define EXT2_DIND_BLOCK                 (EXT2_IND_BLOCK + 1)
#define EXT2_TIND_BLOCK                 (EXT2_DIND_BLOCK + 1)
#define EXT2_N_BLOCKS                   (EXT2_TIND_BLOCK + 1)

/* include/linux/ext2_fs.h */
struct ext2_super_block
  {
    __u32 s_inodes_count;	/* Inodes count */
    __u32 s_blocks_count;	/* Blocks count */
    __u32 s_r_blocks_count;	/* Reserved blocks count */
    __u32 s_free_blocks_count;	/* Free blocks count */
    __u32 s_free_inodes_count;	/* Free inodes count */
    __u32 s_first_data_block;	/* First Data Block */
    __u32 s_log_block_size;	/* Block size */
    __s32 s_log_frag_size;	/* Fragment size */
    __u32 s_blocks_per_group;	/* # Blocks per group */
    __u32 s_frags_per_group;	/* # Fragments per group */
    __u32 s_inodes_per_group;	/* # Inodes per group */
    __u32 s_mtime;		/* Mount time */
    __u32 s_wtime;		/* Write time */
    __u16 s_mnt_count;		/* Mount count */
    __s16 s_max_mnt_count;	/* Maximal mount count */
    __u16 s_magic;		/* Magic signature */
    __u16 s_state;		/* File system state */
    __u16 s_errors;		/* Behaviour when detecting errors */
    __u16 s_pad;
    __u32 s_lastcheck;		/* time of last check */
    __u32 s_checkinterval;	/* max. time between checks */
    __u32 s_creator_os;		/* OS */
    __u32 s_rev_level;		/* Revision level */
    __u16 s_def_resuid;		/* Default uid for reserved blocks */
    __u16 s_def_resgid;		/* Default gid for reserved blocks */
    __u32 s_reserved[235];	/* Padding to the end of the block */
  };

struct ext2_group_desc
  {
    __u32 bg_block_bitmap;	/* Blocks bitmap block */
    __u32 bg_inode_bitmap;	/* Inodes bitmap block */
    __u32 bg_inode_table;	/* Inodes table block */
    __u16 bg_free_blocks_count;	/* Free blocks count */
    __u16 bg_free_inodes_count;	/* Free inodes count */
    __u16 bg_used_dirs_count;	/* Directories count */
    __u16 bg_pad;
    __u32 bg_reserved[3];
  };

struct ext2_inode
  {
    __u16 i_mode;		/* File mode */
    __u16 i_uid;		/* Owner Uid */
    __u32 i_size;		/* 4: Size in bytes */
    __u32 i_atime;		/* Access time */
    __u32 i_ctime;		/* 12: Creation time */
    __u32 i_mtime;		/* Modification time */
    __u32 i_dtime;		/* 20: Deletion Time */
    __u16 i_gid;		/* Group Id */
    __u16 i_links_count;	/* 24: Links count */
    __u32 i_blocks;		/* Blocks count */
    __u32 i_flags;		/* 32: File flags */
    union
      {
	struct
	  {
	    __u32 l_i_reserved1;
	  }
	linux1;
	struct
	  {
	    __u32 h_i_translator;
	  }
	hurd1;
	struct
	  {
	    __u32 m_i_reserved1;
	  }
	masix1;
      }
    osd1;			/* OS dependent 1 */
    __u32 i_block[EXT2_N_BLOCKS];	/* 40: Pointers to blocks */
    __u32 i_version;		/* File version (for NFS) */
    __u32 i_file_acl;		/* File ACL */
    __u32 i_dir_acl;		/* Directory ACL */
    __u32 i_faddr;		/* Fragment address */
    union
      {
	struct
	  {
	    __u8 l_i_frag;	/* Fragment number */
	    __u8 l_i_fsize;	/* Fragment size */
	    __u16 i_pad1;
	    __u32 l_i_reserved2[2];
	  }
	linux2;
	struct
	  {
	    __u8 h_i_frag;	/* Fragment number */
	    __u8 h_i_fsize;	/* Fragment size */
	    __u16 h_i_mode_high;
	    __u16 h_i_uid_high;
	    __u16 h_i_gid_high;
	    __u32 h_i_author;
	  }
	hurd2;
	struct
	  {
	    __u8 m_i_frag;	/* Fragment number */
	    __u8 m_i_fsize;	/* Fragment size */
	    __u16 m_pad1;
	    __u32 m_i_reserved2[2];
	  }
	masix2;
      }
    osd2;			/* OS dependent 2 */
  };

/* linux/limits.h */
#define NAME_MAX         255	/* # chars in a file name */

/* linux/posix_type.h */
typedef long linux_off_t;

/* linux/ext2fs.h */
#define EXT2_NAME_LEN 255
struct ext2_dir_entry
  {
    __u32 inode;		/* Inode number */
    __u16 rec_len;		/* Directory entry length */
    __u8 name_len;		/* Name length */
    __u8 file_type;
    char name[EXT2_NAME_LEN];	/* File name */
  };

/* linux/ext2fs.h */
/*
 * EXT2_DIR_PAD defines the directory entries boundaries
 *
 * NOTE: It must be a multiple of 4
 */
#define EXT2_DIR_PAD                    4
#define EXT2_DIR_ROUND                  (EXT2_DIR_PAD - 1)
#define EXT2_DIR_REC_LEN(name_len)      (((name_len) + 8 + EXT2_DIR_ROUND) & \
                                         ~EXT2_DIR_ROUND)


/* ext2/super.c */
#define log2(n) ffz(~(n))

#define EXT2_SUPER_MAGIC      0xEF53	/* include/linux/ext2_fs.h */
#define EXT2_ROOT_INO              2	/* include/linux/ext2_fs.h */
#define PATH_MAX                1024	/* include/linux/limits.h */
#define MAX_LINK_COUNT             5	/* number of symbolic links to follow */

/* made up, these are pointers into FSYS_BUF */
/* read once, always stays there: */
#define SUPERBLOCK \
    ((struct ext2_super_block *)(FSYS_BUF))
#define GROUP_DESC \
    ((struct ext2_group_desc *) \
     ((int)SUPERBLOCK + sizeof(struct ext2_super_block)))
#define INODE \
    ((struct ext2_inode *)((int)GROUP_DESC + EXT2_BLOCK_SIZE(SUPERBLOCK)))
#define DATABLOCK1 \
    ((int)((int)INODE + sizeof(struct ext2_inode)))
#define DATABLOCK2 \
    ((int)((int)DATABLOCK1 + EXT2_BLOCK_SIZE(SUPERBLOCK)))

/* linux/ext2_fs.h */
#define EXT2_ADDR_PER_BLOCK(s)          (EXT2_BLOCK_SIZE(s) / sizeof (__u32))
#define EXT2_ADDR_PER_BLOCK_BITS(s)		(log2(EXT2_ADDR_PER_BLOCK(s)))

/* linux/ext2_fs.h */
#define EXT2_BLOCK_SIZE_BITS(s)        ((s)->s_log_block_size + 10)
/* kind of from ext2/super.c */
#define EXT2_BLOCK_SIZE(s)	(1 << EXT2_BLOCK_SIZE_BITS(s))
/* linux/ext2fs.h */
#define EXT2_DESC_PER_BLOCK(s) \
     (EXT2_BLOCK_SIZE(s) / sizeof (struct ext2_group_desc))
/* linux/stat.h */
#define S_IFMT  00170000
#define S_IFLNK  0120000
#define S_IFREG  0100000
#define S_IFDIR  0040000
#define S_ISLNK(m)	(((m) & S_IFMT) == S_IFLNK)
#define S_ISREG(m)      (((m) & S_IFMT) == S_IFREG)
#define S_ISDIR(m)      (((m) & S_IFMT) == S_IFDIR)

/* include/asm-i386/bitops.h */
/*
 * ffz = Find First Zero in word. Undefined if no zero exists,
 * so code should check against ~0UL first..
 */
static __inline__ unsigned long
ffz (unsigned long word)
{
  __asm__ ("bsfl %1,%0"
:	   "=r" (word)
:	   "r" (~word));
  return word;
}

/* check filesystem types and read superblock into memory buffer */
int
ext2fs_mount (void)
{
  int retval = 1;

  if ((((current_drive & 0x80) || (current_slice != 0))
       && (current_slice != PC_SLICE_TYPE_EXT2FS)
       && (current_slice != PC_SLICE_TYPE_LINUX_RAID)
       && (! IS_PC_SLICE_TYPE_BSD_WITH_FS (current_slice, FS_EXT2FS))
       && (! IS_PC_SLICE_TYPE_BSD_WITH_FS (current_slice, FS_OTHER)))
      || part_length < (SBLOCK + (sizeof (struct ext2_super_block) / DEV_BSIZE))
      || !devread (SBLOCK, 0, sizeof (struct ext2_super_block),
		   (char *) SUPERBLOCK)
      || SUPERBLOCK->s_magic != EXT2_SUPER_MAGIC)
      retval = 0;

  return retval;
}

/* Takes a file system block number and reads it into BUFFER. */
static int
ext2_rdfsb (int fsblock, int buffer)
{
#ifdef E2DEBUG
  printf ("fsblock %d buffer %d\n", fsblock, buffer);
#endif /* E2DEBUG */
  return devread (fsblock * (EXT2_BLOCK_SIZE (SUPERBLOCK) / DEV_BSIZE), 0,
		  EXT2_BLOCK_SIZE (SUPERBLOCK), (char *) buffer);
}

/* from
  ext2/inode.c:ext2_bmap()
*/
/* Maps LOGICAL_BLOCK (the file offset divided by the blocksize) into
   a physical block (the location in the file system) via an inode. */
static int
ext2fs_block_map (int logical_block)
{

#ifdef E2DEBUG
  unsigned char *i;
  for (i = (unsigned char *) INODE;
       i < ((unsigned char *) INODE + sizeof (struct ext2_inode));
       i++)
    {
      printf ("%c", "0123456789abcdef"[*i >> 4]);
      printf ("%c", "0123456789abcdef"[*i % 16]);
      if (!((i + 1 - (unsigned char *) INODE) % 16))
	{
	  printf ("\n");
	}
      else
	{
	  printf (" ");
	}
    }
  printf ("logical block %d\n", logical_block);
#endif /* E2DEBUG */

  /* if it is directly pointed to by the inode, return that physical addr */
  if (logical_block < EXT2_NDIR_BLOCKS)
    {
#ifdef E2DEBUG
      printf ("returning %d\n", (unsigned char *) (INODE->i_block[logical_block]));
      printf ("returning %d\n", INODE->i_block[logical_block]);
#endif /* E2DEBUG */
      return INODE->i_block[logical_block];
    }
  /* else */
  logical_block -= EXT2_NDIR_BLOCKS;
  /* try the indirect block */
  if (logical_block < EXT2_ADDR_PER_BLOCK (SUPERBLOCK))
    {
      if (mapblock1 != 1
	  && !ext2_rdfsb (INODE->i_block[EXT2_IND_BLOCK], DATABLOCK1))
	{
	  errnum = ERR_FSYS_CORRUPT;
	  return -1;
	}
      mapblock1 = 1;
      return ((__u32 *) DATABLOCK1)[logical_block];
    }
  /* else */
  logical_block -= EXT2_ADDR_PER_BLOCK (SUPERBLOCK);
  /* now try the double indirect block */
  if (logical_block < (1 << (EXT2_ADDR_PER_BLOCK_BITS (SUPERBLOCK) * 2)))
    {
      int bnum;
      if (mapblock1 != 2
	  && !ext2_rdfsb (INODE->i_block[EXT2_DIND_BLOCK], DATABLOCK1))
	{
	  errnum = ERR_FSYS_CORRUPT;
	  return -1;
	}
      mapblock1 = 2;
      if ((bnum = (((__u32 *) DATABLOCK1)
		   [logical_block >> EXT2_ADDR_PER_BLOCK_BITS (SUPERBLOCK)]))
	  != mapblock2
	  && !ext2_rdfsb (bnum, DATABLOCK2))
	{
	  errnum = ERR_FSYS_CORRUPT;
	  return -1;
	}
      mapblock2 = bnum;
      return ((__u32 *) DATABLOCK2)
	[logical_block & (EXT2_ADDR_PER_BLOCK (SUPERBLOCK) - 1)];
    }
  /* else */
  mapblock2 = -1;
  logical_block -= (1 << (EXT2_ADDR_PER_BLOCK_BITS (SUPERBLOCK) * 2));
  if (mapblock1 != 3
      && !ext2_rdfsb (INODE->i_block[EXT2_TIND_BLOCK], DATABLOCK1))
    {
      errnum = ERR_FSYS_CORRUPT;
      return -1;
    }
  mapblock1 = 3;
  if (!ext2_rdfsb (((__u32 *) DATABLOCK1)
		   [logical_block >> (EXT2_ADDR_PER_BLOCK_BITS (SUPERBLOCK)
				      * 2)],
		   DATABLOCK2))
    {
      errnum = ERR_FSYS_CORRUPT;
      return -1;
    }
  if (!ext2_rdfsb (((__u32 *) DATABLOCK2)
		   [(logical_block >> EXT2_ADDR_PER_BLOCK_BITS (SUPERBLOCK))
		    & (EXT2_ADDR_PER_BLOCK (SUPERBLOCK) - 1)],
		   DATABLOCK2))
    {
      errnum = ERR_FSYS_CORRUPT;
      return -1;
    }
  return ((__u32 *) DATABLOCK2)
    [logical_block & (EXT2_ADDR_PER_BLOCK (SUPERBLOCK) - 1)];
}

/* preconditions: all preconds of ext2fs_block_map */
int
ext2fs_read (char *buf, int len)
{
  int logical_block;