text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *  linux/fs/sysv/inode.c
   *
   *  minix/inode.c
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  xenix/inode.c
   *  Copyright (C) 1992  Doug Evans
   *
   *  coh/inode.c
   *  Copyright (C) 1993  Pascal Haible, Bruno Haible
   *
   *  sysv/inode.c
   *  Copyright (C) 1993  Paul B. Monday
   *
   *  sysv/inode.c
   *  Copyright (C) 1993  Bruno Haible
   *  Copyright (C) 1997, 1998  Krzysztof G. Baranowski
   *
   *  This file contains code for read/parsing the superblock.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/buffer_head.h>
  #include "sysv.h"
  
  /*
   * The following functions try to recognize specific filesystems.
   *
   * We recognize:
   * - Xenix FS by its magic number.
   * - SystemV FS by its magic number.
   * - Coherent FS by its funny fname/fpack field.
   * - SCO AFS by s_nfree == 0xffff
   * - V7 FS has no distinguishing features.
   *
   * We discriminate among SystemV4 and SystemV2 FS by the assumption that
   * the time stamp is not < 01-01-1980.
   */
  
  enum {
  	JAN_1_1980 = (10*365 + 2) * 24 * 60 * 60
  };
  
  static void detected_xenix(struct sysv_sb_info *sbi, unsigned *max_links)
  {
  	struct buffer_head *bh1 = sbi->s_bh1;
  	struct buffer_head *bh2 = sbi->s_bh2;
  	struct xenix_super_block * sbd1;
  	struct xenix_super_block * sbd2;
  
  	if (bh1 != bh2)
  		sbd1 = sbd2 = (struct xenix_super_block *) bh1->b_data;
  	else {
  		/* block size = 512, so bh1 != bh2 */
  		sbd1 = (struct xenix_super_block *) bh1->b_data;
  		sbd2 = (struct xenix_super_block *) (bh2->b_data - 512);
  	}
  
  	*max_links = XENIX_LINK_MAX;
  	sbi->s_fic_size = XENIX_NICINOD;
  	sbi->s_flc_size = XENIX_NICFREE;
  	sbi->s_sbd1 = (char *)sbd1;
  	sbi->s_sbd2 = (char *)sbd2;
  	sbi->s_sb_fic_count = &sbd1->s_ninode;
  	sbi->s_sb_fic_inodes = &sbd1->s_inode[0];
  	sbi->s_sb_total_free_inodes = &sbd2->s_tinode;
  	sbi->s_bcache_count = &sbd1->s_nfree;
  	sbi->s_bcache = &sbd1->s_free[0];
  	sbi->s_free_blocks = &sbd2->s_tfree;
  	sbi->s_sb_time = &sbd2->s_time;
  	sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd1->s_isize);
  	sbi->s_nzones = fs32_to_cpu(sbi, sbd1->s_fsize);
  }
  
  static void detected_sysv4(struct sysv_sb_info *sbi, unsigned *max_links)
  {
  	struct sysv4_super_block * sbd;
  	struct buffer_head *bh1 = sbi->s_bh1;
  	struct buffer_head *bh2 = sbi->s_bh2;
  
  	if (bh1 == bh2)
  		sbd = (struct sysv4_super_block *) (bh1->b_data + BLOCK_SIZE/2);
  	else
  		sbd = (struct sysv4_super_block *) bh2->b_data;
  
  	*max_links = SYSV_LINK_MAX;
  	sbi->s_fic_size = SYSV_NICINOD;
  	sbi->s_flc_size = SYSV_NICFREE;
  	sbi->s_sbd1 = (char *)sbd;
  	sbi->s_sbd2 = (char *)sbd;
  	sbi->s_sb_fic_count = &sbd->s_ninode;
  	sbi->s_sb_fic_inodes = &sbd->s_inode[0];
  	sbi->s_sb_total_free_inodes = &sbd->s_tinode;
  	sbi->s_bcache_count = &sbd->s_nfree;
  	sbi->s_bcache = &sbd->s_free[0];
  	sbi->s_free_blocks = &sbd->s_tfree;
  	sbi->s_sb_time = &sbd->s_time;
  	sbi->s_sb_state = &sbd->s_state;
  	sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
  	sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
  }
  
  static void detected_sysv2(struct sysv_sb_info *sbi, unsigned *max_links)
  {
  	struct sysv2_super_block *sbd;
  	struct buffer_head *bh1 = sbi->s_bh1;
  	struct buffer_head *bh2 = sbi->s_bh2;
  
  	if (bh1 == bh2)
  		sbd = (struct sysv2_super_block *) (bh1->b_data + BLOCK_SIZE/2);
  	else
  		sbd = (struct sysv2_super_block *) bh2->b_data;
  
  	*max_links = SYSV_LINK_MAX;
  	sbi->s_fic_size = SYSV_NICINOD;
  	sbi->s_flc_size = SYSV_NICFREE;
  	sbi->s_sbd1 = (char *)sbd;
  	sbi->s_sbd2 = (char *)sbd;
  	sbi->s_sb_fic_count = &sbd->s_ninode;
  	sbi->s_sb_fic_inodes = &sbd->s_inode[0];
  	sbi->s_sb_total_free_inodes = &sbd->s_tinode;
  	sbi->s_bcache_count = &sbd->s_nfree;
  	sbi->s_bcache = &sbd->s_free[0];
  	sbi->s_free_blocks = &sbd->s_tfree;
  	sbi->s_sb_time = &sbd->s_time;
  	sbi->s_sb_state = &sbd->s_state;
  	sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
  	sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
  }
  
  static void detected_coherent(struct sysv_sb_info *sbi, unsigned *max_links)
  {
  	struct coh_super_block * sbd;
  	struct buffer_head *bh1 = sbi->s_bh1;
  
  	sbd = (struct coh_super_block *) bh1->b_data;
  
  	*max_links = COH_LINK_MAX;
  	sbi->s_fic_size = COH_NICINOD;
  	sbi->s_flc_size = COH_NICFREE;
  	sbi->s_sbd1 = (char *)sbd;
  	sbi->s_sbd2 = (char *)sbd;
  	sbi->s_sb_fic_count = &sbd->s_ninode;
  	sbi->s_sb_fic_inodes = &sbd->s_inode[0];
  	sbi->s_sb_total_free_inodes = &sbd->s_tinode;
  	sbi->s_bcache_count = &sbd->s_nfree;
  	sbi->s_bcache = &sbd->s_free[0];
  	sbi->s_free_blocks = &sbd->s_tfree;
  	sbi->s_sb_time = &sbd->s_time;
  	sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
  	sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
  }
  
  static void detected_v7(struct sysv_sb_info *sbi, unsigned *max_links)
  {
  	struct buffer_head *bh2 = sbi->s_bh2;
  	struct v7_super_block *sbd = (struct v7_super_block *)bh2->b_data;
  
  	*max_links = V7_LINK_MAX;
  	sbi->s_fic_size = V7_NICINOD;
  	sbi->s_flc_size = V7_NICFREE;
  	sbi->s_sbd1 = (char *)sbd;
  	sbi->s_sbd2 = (char *)sbd;
  	sbi->s_sb_fic_count = &sbd->s_ninode;
  	sbi->s_sb_fic_inodes = &sbd->s_inode[0];
  	sbi->s_sb_total_free_inodes = &sbd->s_tinode;
  	sbi->s_bcache_count = &sbd->s_nfree;
  	sbi->s_bcache = &sbd->s_free[0];
  	sbi->s_free_blocks = &sbd->s_tfree;
  	sbi->s_sb_time = &sbd->s_time;
  	sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
  	sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
  }
  
  static int detect_xenix(struct sysv_sb_info *sbi, struct buffer_head *bh)
  {
  	struct xenix_super_block *sbd = (struct xenix_super_block *)bh->b_data;
  	if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0x2b5544))
  		sbi->s_bytesex = BYTESEX_LE;
  	else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0x2b5544))
  		sbi->s_bytesex = BYTESEX_BE;
  	else
  		return 0;
  	switch (fs32_to_cpu(sbi, sbd->s_type)) {
  	case 1:
  		sbi->s_type = FSTYPE_XENIX;
  		return 1;
  	case 2:
  		sbi->s_type = FSTYPE_XENIX;
  		return 2;
  	default:
  		return 0;
  	}
  }
  
  static int detect_sysv(struct sysv_sb_info *sbi, struct buffer_head *bh)
  {
  	struct super_block *sb = sbi->s_sb;
  	/* All relevant fields are at the same offsets in R2 and R4 */
  	struct sysv4_super_block * sbd;
  	u32 type;
  
  	sbd = (struct sysv4_super_block *) (bh->b_data + BLOCK_SIZE/2);
  	if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0xfd187e20))
  		sbi->s_bytesex = BYTESEX_LE;
  	else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0xfd187e20))
  		sbi->s_bytesex = BYTESEX_BE;
  	else
  		return 0;
  
  	type = fs32_to_cpu(sbi, sbd->s_type);
   
   	if (fs16_to_cpu(sbi, sbd->s_nfree) == 0xffff) {
   		sbi->s_type = FSTYPE_AFS;
  		sbi->s_forced_ro = 1;
   		if (!sb_rdonly(sb)) {
   			printk("SysV FS: SCO EAFS on %s detected, " 
   				"forcing read-only mode.\n", 
   				sb->s_id);
   		}
   		return type;
   	}
   
  	if (fs32_to_cpu(sbi, sbd->s_time) < JAN_1_1980) {
  		/* this is likely to happen on SystemV2 FS */
  		if (type > 3 || type < 1)
  			return 0;
  		sbi->s_type = FSTYPE_SYSV2;
  		return type;
  	}
  	if ((type > 3 || type < 1) && (type > 0x30 || type < 0x10))
  		return 0;
  
  	/* On Interactive Unix (ISC) Version 4.0/3.x s_type field = 0x10,
  	   0x20 or 0x30 indicates that symbolic links and the 14-character
  	   filename limit is gone. Due to lack of information about this
             feature read-only mode seems to be a reasonable approach... -KGB */
  
  	if (type >= 0x10) {
  		printk("SysV FS: can't handle long file names on %s, "
  		       "forcing read-only mode.\n", sb->s_id);
  		sbi->s_forced_ro = 1;
  	}
  
  	sbi->s_type = FSTYPE_SYSV4;
  	return type >= 0x10 ? type >> 4 : type;
  }
  
  static int detect_coherent(struct sysv_sb_info *sbi, struct buffer_head *bh)
  {
  	struct coh_super_block * sbd;
  
  	sbd = (struct coh_super_block *) (bh->b_data + BLOCK_SIZE/2);
  	if ((memcmp(sbd->s_fname,"noname",6) && memcmp(sbd->s_fname,"xxxxx ",6))
  	    || (memcmp(sbd->s_fpack,"nopack",6) && memcmp(sbd->s_fpack,"xxxxx\n",6)))
  		return 0;
  	sbi->s_bytesex = BYTESEX_PDP;
  	sbi->s_type = FSTYPE_COH;
  	return 1;
  }
  
  static int detect_sysv_odd(struct sysv_sb_info *sbi, struct buffer_head *bh)
  {
  	int size = detect_sysv(sbi, bh);
  
  	return size>2 ? 0 : size;
  }
  
  static struct {
  	int block;
  	int (*test)(struct sysv_sb_info *, struct buffer_head *);
  } flavours[] = {
  	{1, detect_xenix},
  	{0, detect_sysv},
  	{0, detect_coherent},
  	{9, detect_sysv_odd},
  	{15,detect_sysv_odd},
  	{18,detect_sysv},
  };
  
  static char *flavour_names[] = {
  	[FSTYPE_XENIX]	= "Xenix",
  	[FSTYPE_SYSV4]	= "SystemV",
  	[FSTYPE_SYSV2]	= "SystemV Release 2",
  	[FSTYPE_COH]	= "Coherent",
  	[FSTYPE_V7]	= "V7",
  	[FSTYPE_AFS]	= "AFS",
  };
  
  static void (*flavour_setup[])(struct sysv_sb_info *, unsigned *) = {
  	[FSTYPE_XENIX]	= detected_xenix,
  	[FSTYPE_SYSV4]	= detected_sysv4,
  	[FSTYPE_SYSV2]	= detected_sysv2,
  	[FSTYPE_COH]	= detected_coherent,
  	[FSTYPE_V7]	= detected_v7,
  	[FSTYPE_AFS]	= detected_sysv4,
  };
  
  static int complete_read_super(struct super_block *sb, int silent, int size)
  {
  	struct sysv_sb_info *sbi = SYSV_SB(sb);
  	struct inode *root_inode;
  	char *found = flavour_names[sbi->s_type];
  	u_char n_bits = size+8;
  	int bsize = 1 << n_bits;
  	int bsize_4 = bsize >> 2;
  
  	sbi->s_firstinodezone = 2;
  
  	flavour_setup[sbi->s_type](sbi, &sb->s_max_links);
  	
  	sbi->s_ndatazones = sbi->s_nzones - sbi->s_firstdatazone;
  	sbi->s_inodes_per_block = bsize >> 6;
  	sbi->s_inodes_per_block_1 = (bsize >> 6)-1;
  	sbi->s_inodes_per_block_bits = n_bits-6;
  	sbi->s_ind_per_block = bsize_4;
  	sbi->s_ind_per_block_2 = bsize_4*bsize_4;
  	sbi->s_toobig_block = 10 + bsize_4 * (1 + bsize_4 * (1 + bsize_4));
  	sbi->s_ind_per_block_bits = n_bits-2;
  
  	sbi->s_ninodes = (sbi->s_firstdatazone - sbi->s_firstinodezone)
  		<< sbi->s_inodes_per_block_bits;
  
  	if (!silent)
  		printk("VFS: Found a %s FS (block size = %ld) on device %s\n",
  		       found, sb->s_blocksize, sb->s_id);
  
  	sb->s_magic = SYSV_MAGIC_BASE + sbi->s_type;
  	/* set up enough so that it can read an inode */
  	sb->s_op = &sysv_sops;
  	if (sbi->s_forced_ro)
  		sb->s_flags |= SB_RDONLY;
  	root_inode = sysv_iget(sb, SYSV_ROOT_INO);
  	if (IS_ERR(root_inode)) {
  		printk("SysV FS: get root inode failed\n");
  		return 0;
  	}
  	sb->s_root = d_make_root(root_inode);
  	if (!sb->s_root) {
  		printk("SysV FS: get root dentry failed\n");
  		return 0;
  	}
  	return 1;
  }
  
  static int sysv_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct buffer_head *bh1, *bh = NULL;
  	struct sysv_sb_info *sbi;
  	unsigned long blocknr;
  	int size = 0, i;
  	
  	BUILD_BUG_ON(1024 != sizeof (struct xenix_super_block));
  	BUILD_BUG_ON(512 != sizeof (struct sysv4_super_block));
  	BUILD_BUG_ON(512 != sizeof (struct sysv2_super_block));
  	BUILD_BUG_ON(500 != sizeof (struct coh_super_block));
  	BUILD_BUG_ON(64 != sizeof (struct sysv_inode));
  
  	sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
  	if (!sbi)
  		return -ENOMEM;
  
  	sbi->s_sb = sb;
  	sbi->s_block_base = 0;
  	mutex_init(&sbi->s_lock);
  	sb->s_fs_info = sbi;
  	sb->s_time_min = 0;
  	sb->s_time_max = U32_MAX;
  	sb_set_blocksize(sb, BLOCK_SIZE);
  
  	for (i = 0; i < ARRAY_SIZE(flavours) && !size; i++) {
  		brelse(bh);
  		bh = sb_bread(sb, flavours[i].block);
  		if (!bh)
  			continue;
  		size = flavours[i].test(SYSV_SB(sb), bh);
  	}
  
  	if (!size)
  		goto Eunknown;
  
  	switch (size) {
  		case 1:
  			blocknr = bh->b_blocknr << 1;
  			brelse(bh);
  			sb_set_blocksize(sb, 512);
  			bh1 = sb_bread(sb, blocknr);
  			bh = sb_bread(sb, blocknr + 1);
  			break;
  		case 2:
  			bh1 = bh;
  			break;
  		case 3:
  			blocknr = bh->b_blocknr >> 1;
  			brelse(bh);
  			sb_set_blocksize(sb, 2048);
  			bh1 = bh = sb_bread(sb, blocknr);
  			break;
  		default:
  			goto Ebadsize;
  	}
  
  	if (bh && bh1) {
  		sbi->s_bh1 = bh1;
  		sbi->s_bh2 = bh;
  		if (complete_read_super(sb, silent, size))
  			return 0;
  	}
  
  	brelse(bh1);
  	brelse(bh);
  	sb_set_blocksize(sb, BLOCK_SIZE);
  	printk("oldfs: cannot read superblock\n");
  failed:
  	kfree(sbi);
  	return -EINVAL;
  
  Eunknown:
  	brelse(bh);
  	if (!silent)
  		printk("VFS: unable to find oldfs superblock on device %s\n",
  			sb->s_id);
  	goto failed;
  Ebadsize:
  	brelse(bh);
  	if (!silent)
  		printk("VFS: oldfs: unsupported block size (%dKb)\n",
  			1<<(size-2));
  	goto failed;
  }
  
  static int v7_sanity_check(struct super_block *sb, struct buffer_head *bh)
  {
  	struct v7_super_block *v7sb;
  	struct sysv_inode *v7i;
  	struct buffer_head *bh2;
  	struct sysv_sb_info *sbi;
  
  	sbi = sb->s_fs_info;
  
  	/* plausibility check on superblock */
  	v7sb = (struct v7_super_block *) bh->b_data;
  	if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
  	    fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
  	    fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
  		return 0;
  
  	/* plausibility check on root inode: it is a directory,
  	   with a nonzero size that is a multiple of 16 */
  	bh2 = sb_bread(sb, 2);
  	if (bh2 == NULL)
  		return 0;
  
  	v7i = (struct sysv_inode *)(bh2->b_data + 64);
  	if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
  	    (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
  	    (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
  	    (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
  	     sizeof(struct sysv_dir_entry))) {
  		brelse(bh2);
  		return 0;
  	}
  
  	brelse(bh2);
  	return 1;
  }
  
  static int v7_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct sysv_sb_info *sbi;
  	struct buffer_head *bh;
  
  	BUILD_BUG_ON(sizeof(struct v7_super_block) != 440);
  	BUILD_BUG_ON(sizeof(struct sysv_inode) != 64);
  
  	sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
  	if (!sbi)
  		return -ENOMEM;
  
  	sbi->s_sb = sb;
  	sbi->s_block_base = 0;
  	sbi->s_type = FSTYPE_V7;
  	mutex_init(&sbi->s_lock);
  	sb->s_fs_info = sbi;
  	sb->s_time_min = 0;
  	sb->s_time_max = U32_MAX;
  	
  	sb_set_blocksize(sb, 512);
  
  	if ((bh = sb_bread(sb, 1)) == NULL) {
  		if (!silent)
  			printk("VFS: unable to read V7 FS superblock on "
  			       "device %s.\n", sb->s_id);
  		goto failed;
  	}
  
  	/* Try PDP-11 UNIX */
  	sbi->s_bytesex = BYTESEX_PDP;
  	if (v7_sanity_check(sb, bh))
  		goto detected;
  
  	/* Try PC/IX, v7/x86 */
  	sbi->s_bytesex = BYTESEX_LE;
  	if (v7_sanity_check(sb, bh))
  		goto detected;
  
  	goto failed;
  
  detected:
  	sbi->s_bh1 = bh;
  	sbi->s_bh2 = bh;
  	if (complete_read_super(sb, silent, 1))
  		return 0;
  
  failed:
  	printk(KERN_ERR "VFS: could not find a valid V7 on %s.\n",
  		sb->s_id);
  	brelse(bh);
  	kfree(sbi);
  	return -EINVAL;
  }
  
  /* Every kernel module contains stuff like this. */
  
  static struct dentry *sysv_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	return mount_bdev(fs_type, flags, dev_name, data, sysv_fill_super);
  }
  
  static struct dentry *v7_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	return mount_bdev(fs_type, flags, dev_name, data, v7_fill_super);
  }
  
  static struct file_system_type sysv_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "sysv",
  	.mount		= sysv_mount,
  	.kill_sb	= kill_block_super,
  	.fs_flags	= FS_REQUIRES_DEV,
  };
  MODULE_ALIAS_FS("sysv");
  
  static struct file_system_type v7_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "v7",
  	.mount		= v7_mount,
  	.kill_sb	= kill_block_super,
  	.fs_flags	= FS_REQUIRES_DEV,
  };
  MODULE_ALIAS_FS("v7");
  MODULE_ALIAS("v7");
  
  static int __init init_sysv_fs(void)
  {
  	int error;
  
  	error = sysv_init_icache();
  	if (error)
  		goto out;
  	error = register_filesystem(&sysv_fs_type);
  	if (error)
  		goto destroy_icache;
  	error = register_filesystem(&v7_fs_type);
  	if (error)
  		goto unregister;
  	return 0;
  
  unregister:
  	unregister_filesystem(&sysv_fs_type);
  destroy_icache:
  	sysv_destroy_icache();
  out:
  	return error;
  }
  
  static void __exit exit_sysv_fs(void)
  {
  	unregister_filesystem(&sysv_fs_type);
  	unregister_filesystem(&v7_fs_type);
  	sysv_destroy_icache();
  }
  
  module_init(init_sysv_fs)
  module_exit(exit_sysv_fs)
  MODULE_LICENSE("GPL");
  