// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  linux/fs/adfs/dir_f.c
   *
   * Copyright (C) 1997-1999 Russell King
   *

   *  E and F format directory handling
   */

  #include "adfs.h"
  #include "dir_f.h"
  
  static void adfs_f_free(struct adfs_dir *dir);
  
  /*
   * Read an (unaligned) value of length 1..4 bytes
   */
  static inline unsigned int adfs_readval(unsigned char *p, int len)
  {
  	unsigned int val = 0;
  
  	switch (len) {
  	case 4:		val |= p[3] << 24;

  			/* fall through */

  	case 3:		val |= p[2] << 16;

  			/* fall through */

  	case 2:		val |= p[1] << 8;

  			/* fall through */

  	default:	val |= p[0];
  	}
  	return val;
  }
  
  static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
  {
  	switch (len) {
  	case 4:		p[3] = val >> 24;

  			/* fall through */

  	case 3:		p[2] = val >> 16;

  			/* fall through */

  	case 2:		p[1] = val >> 8;

  			/* fall through */

  	default:	p[0] = val;
  	}
  }

  #define ror13(v) ((v >> 13) | (v << 19))
  
  #define dir_u8(idx)				\
  	({ int _buf = idx >> blocksize_bits;	\
  	   int _off = idx - (_buf << blocksize_bits);\
  	  *(u8 *)(bh[_buf]->b_data + _off);	\
  	})
  
  #define dir_u32(idx)				\
  	({ int _buf = idx >> blocksize_bits;	\
  	   int _off = idx - (_buf << blocksize_bits);\
  	  *(__le32 *)(bh[_buf]->b_data + _off);	\
  	})
  
  #define bufoff(_bh,_idx)			\
  	({ int _buf = _idx >> blocksize_bits;	\
  	   int _off = _idx - (_buf << blocksize_bits);\
  	  (u8 *)(_bh[_buf]->b_data + _off);	\
  	})
  
  /*
   * There are some algorithms that are nice in
   * assembler, but a bitch in C...  This is one
   * of them.
   */
  static u8
  adfs_dir_checkbyte(const struct adfs_dir *dir)
  {
  	struct buffer_head * const *bh = dir->bh;
  	const int blocksize_bits = dir->sb->s_blocksize_bits;
  	union { __le32 *ptr32; u8 *ptr8; } ptr, end;
  	u32 dircheck = 0;
  	int last = 5 - 26;
  	int i = 0;
  
  	/*
  	 * Accumulate each word up to the last whole
  	 * word of the last directory entry.  This
  	 * can spread across several buffer heads.
  	 */
  	do {
  		last += 26;
  		do {
  			dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);
  
  			i += sizeof(u32);
  		} while (i < (last & ~3));
  	} while (dir_u8(last) != 0);
  
  	/*
  	 * Accumulate the last few bytes.  These
  	 * bytes will be within the same bh.
  	 */
  	if (i != last) {
  		ptr.ptr8 = bufoff(bh, i);
  		end.ptr8 = ptr.ptr8 + last - i;

  		do {

  			dircheck = *ptr.ptr8++ ^ ror13(dircheck);

  		} while (ptr.ptr8 < end.ptr8);

  	}
  
  	/*
  	 * The directory tail is in the final bh
  	 * Note that contary to the RISC OS PRMs,
  	 * the first few bytes are NOT included
  	 * in the check.  All bytes are in the
  	 * same bh.
  	 */
  	ptr.ptr8 = bufoff(bh, 2008);
  	end.ptr8 = ptr.ptr8 + 36;
  
  	do {
  		__le32 v = *ptr.ptr32++;
  		dircheck = le32_to_cpu(v) ^ ror13(dircheck);
  	} while (ptr.ptr32 < end.ptr32);
  
  	return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
  }

  /* Read and check that a directory is valid */
  static int adfs_dir_read(struct super_block *sb, u32 indaddr,
  			 unsigned int size, struct adfs_dir *dir)

  {
  	const unsigned int blocksize_bits = sb->s_blocksize_bits;
  	int blk = 0;
  
  	/*
  	 * Directories which are not a multiple of 2048 bytes
  	 * are considered bad v2 [3.6]
  	 */
  	if (size & 2047)
  		goto bad_dir;
  
  	size >>= blocksize_bits;
  
  	dir->nr_buffers = 0;
  	dir->sb = sb;
  
  	for (blk = 0; blk < size; blk++) {
  		int phys;

  		phys = __adfs_block_map(sb, indaddr, blk);

  		if (!phys) {

  			adfs_error(sb, "dir %06x has a hole at offset %d",
  				   indaddr, blk);

  			goto release_buffers;
  		}
  
  		dir->bh[blk] = sb_bread(sb, phys);
  		if (!dir->bh[blk])
  			goto release_buffers;
  	}
  
  	memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
  	memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
  
  	if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
  	    memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
  		goto bad_dir;
  
  	if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
  	    memcmp(&dir->dirhead.startname, "Hugo", 4))
  		goto bad_dir;
  
  	if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
  		goto bad_dir;
  
  	dir->nr_buffers = blk;
  
  	return 0;
  
  bad_dir:

  	adfs_error(sb, "dir %06x is corrupted", indaddr);

  release_buffers:
  	for (blk -= 1; blk >= 0; blk -= 1)
  		brelse(dir->bh[blk]);
  
  	dir->sb = NULL;
  
  	return -EIO;
  }
  
  /*
   * convert a disk-based directory entry to a Linux ADFS directory entry
   */
  static inline void

  adfs_dir2obj(struct adfs_dir *dir, struct object_info *obj,
  	struct adfs_direntry *de)

  {

  	unsigned int name_len;
  
  	for (name_len = 0; name_len < ADFS_F_NAME_LEN; name_len++) {
  		if (de->dirobname[name_len] < ' ')
  			break;
  
  		obj->name[name_len] = de->dirobname[name_len];
  	}
  
  	obj->name_len =	name_len;

  	obj->indaddr  = adfs_readval(de->dirinddiscadd, 3);

  	obj->loadaddr = adfs_readval(de->dirload, 4);
  	obj->execaddr = adfs_readval(de->direxec, 4);
  	obj->size     = adfs_readval(de->dirlen,  4);
  	obj->attr     = de->newdiratts;

  	adfs_object_fixup(dir, obj);

  }
  
  /*
   * convert a Linux ADFS directory entry to a disk-based directory entry
   */
  static inline void
  adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
  {

  	adfs_writeval(de->dirinddiscadd, 3, obj->indaddr);

  	adfs_writeval(de->dirload, 4, obj->loadaddr);
  	adfs_writeval(de->direxec, 4, obj->execaddr);
  	adfs_writeval(de->dirlen,  4, obj->size);
  	de->newdiratts = obj->attr;
  }
  
  /*
   * get a directory entry.  Note that the caller is responsible
   * for holding the relevant locks.
   */
  static int
  __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
  {
  	struct super_block *sb = dir->sb;
  	struct adfs_direntry de;
  	int thissize, buffer, offset;
  
  	buffer = pos >> sb->s_blocksize_bits;
  
  	if (buffer > dir->nr_buffers)
  		return -EINVAL;
  
  	offset = pos & (sb->s_blocksize - 1);
  	thissize = sb->s_blocksize - offset;
  	if (thissize > 26)
  		thissize = 26;
  
  	memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
  	if (thissize != 26)
  		memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
  		       26 - thissize);
  
  	if (!de.dirobname[0])
  		return -ENOENT;

  	adfs_dir2obj(dir, obj, &de);

  
  	return 0;
  }
  
  static int
  __adfs_dir_put(struct adfs_dir *dir, int pos, struct object_info *obj)
  {
  	struct super_block *sb = dir->sb;
  	struct adfs_direntry de;
  	int thissize, buffer, offset;
  
  	buffer = pos >> sb->s_blocksize_bits;
  
  	if (buffer > dir->nr_buffers)
  		return -EINVAL;
  
  	offset = pos & (sb->s_blocksize - 1);
  	thissize = sb->s_blocksize - offset;
  	if (thissize > 26)
  		thissize = 26;
  
  	/*
  	 * Get the entry in total
  	 */
  	memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
  	if (thissize != 26)
  		memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
  		       26 - thissize);
  
  	/*
  	 * update it
  	 */
  	adfs_obj2dir(&de, obj);
  
  	/*
  	 * Put the new entry back
  	 */
  	memcpy(dir->bh[buffer]->b_data + offset, &de, thissize);
  	if (thissize != 26)
  		memcpy(dir->bh[buffer + 1]->b_data, ((char *)&de) + thissize,
  		       26 - thissize);
  
  	return 0;
  }
  
  /*
   * the caller is responsible for holding the necessary
   * locks.
   */

  static int adfs_dir_find_entry(struct adfs_dir *dir, u32 indaddr)

  {
  	int pos, ret;
  
  	ret = -ENOENT;
  
  	for (pos = 5; pos < ADFS_NUM_DIR_ENTRIES * 26 + 5; pos += 26) {
  		struct object_info obj;
  
  		if (!__adfs_dir_get(dir, pos, &obj))
  			break;

  		if (obj.indaddr == indaddr) {

  			ret = pos;
  			break;
  		}
  	}
  
  	return ret;
  }

  static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
  		       struct adfs_dir *dir)

  {
  	int ret;

  	if (size != ADFS_NEWDIR_SIZE)

  		return -EIO;

  	ret = adfs_dir_read(sb, indaddr, size, dir);

  	if (ret)
  		adfs_error(sb, "unable to read directory");
  	else
  		dir->parent_id = adfs_readval(dir->dirtail.new.dirparent, 3);
  
  	return ret;
  }
  
  static int
  adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
  {
  	if (fpos >= ADFS_NUM_DIR_ENTRIES)
  		return -ENOENT;
  
  	dir->pos = 5 + fpos * 26;
  	return 0;
  }
  
  static int
  adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
  {
  	unsigned int ret;
  
  	ret = __adfs_dir_get(dir, dir->pos, obj);
  	if (ret == 0)
  		dir->pos += 26;
  
  	return ret;
  }
  
  static int
  adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
  {
  	struct super_block *sb = dir->sb;
  	int ret, i;

  	ret = adfs_dir_find_entry(dir, obj->indaddr);

  	if (ret < 0) {
  		adfs_error(dir->sb, "unable to locate entry to update");
  		goto out;
  	}
  
  	__adfs_dir_put(dir, ret, obj);
   
  	/*
  	 * Increment directory sequence number
  	 */
  	dir->bh[0]->b_data[0] += 1;
  	dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 6] += 1;
  
  	ret = adfs_dir_checkbyte(dir);
  	/*
  	 * Update directory check byte
  	 */
  	dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 1] = ret;
  
  #if 1
  	{
  	const unsigned int blocksize_bits = sb->s_blocksize_bits;
  
  	memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
  	memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
  
  	if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
  	    memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
  		goto bad_dir;
  
  	if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
  	    memcmp(&dir->dirhead.startname, "Hugo", 4))
  		goto bad_dir;
  
  	if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
  		goto bad_dir;
  	}
  #endif
  	for (i = dir->nr_buffers - 1; i >= 0; i--)
  		mark_buffer_dirty(dir->bh[i]);
  
  	ret = 0;
  out:
  	return ret;
  #if 1
  bad_dir:
  	adfs_error(dir->sb, "whoops!  I broke a directory!");
  	return -EIO;
  #endif
  }

  static int
  adfs_f_sync(struct adfs_dir *dir)
  {
  	int err = 0;
  	int i;
  
  	for (i = dir->nr_buffers - 1; i >= 0; i--) {
  		struct buffer_head *bh = dir->bh[i];
  		sync_dirty_buffer(bh);
  		if (buffer_req(bh) && !buffer_uptodate(bh))
  			err = -EIO;
  	}
  
  	return err;
  }

  static void
  adfs_f_free(struct adfs_dir *dir)
  {
  	int i;
  
  	for (i = dir->nr_buffers - 1; i >= 0; i--) {
  		brelse(dir->bh[i]);
  		dir->bh[i] = NULL;
  	}
  
  	dir->nr_buffers = 0;
  	dir->sb = NULL;
  }

  const struct adfs_dir_ops adfs_f_dir_ops = {

  	.read		= adfs_f_read,
  	.setpos		= adfs_f_setpos,
  	.getnext	= adfs_f_getnext,
  	.update		= adfs_f_update,

  	.sync		= adfs_f_sync,

  	.free		= adfs_f_free
  };