dir_f.c

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/*
 *  linux/fs/adfs/dir_f.c
 *
 * Copyright (C) 1997-1999 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  E and F format directory handling
 */
#include <linux/buffer_head.h>
#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;
    case 3:     val |= p[2] << 16;
    case 2:     val |= p[1] << 8;
    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;
    case 3:     p[2] = val >> 16;
    case 2:     p[1] = val >> 8;
    default:    p[0] = val;
    }
}

static inline int adfs_readname(char *buf, char *ptr, int maxlen)
{
    char *old_buf = buf;

    while ((unsigned char)*ptr >= ' ' && maxlen--) {
        if (*ptr == '/')
            *buf++ = '.';
        else
            *buf++ = *ptr;
        ptr++;
    }

    return buf - old_buf;
}

#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, unsigned long object_id,
          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, object_id, blk);
        if (!phys) {
            adfs_error(sb, "dir object %lX has a hole at offset %d",
                   object_id, 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, "corrupted directory fragment %lX",
           object_id);
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)
{
    obj->name_len = adfs_readname(obj->name, de->dirobname, ADFS_F_NAME_LEN);
    obj->file_id  = 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;
    obj->filetype = -1;

    /*
     * object is a file and is filetyped and timestamped?
     * RISC OS 12-bit filetype is stored in load_address[19:8]
     */
    if ((0 == (obj->attr & ADFS_NDA_DIRECTORY)) &&
        (0xfff00000 == (0xfff00000 & obj->loadaddr))) {
        obj->filetype = (__u16) ((0x000fff00 & obj->loadaddr) >> 8);

        /* optionally append the ,xyz hex filetype suffix */
        if (ADFS_SB(dir->sb)->s_ftsuffix)
            obj->name_len +=
                append_filetype_suffix(
                    &obj->name[obj->name_len],
                    obj->filetype);
    }
}

/*
 * 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->file_id);
    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, unsigned long object_id)
{
    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.file_id == object_id) {
            ret = pos;
            break;
        }
    }

    return ret;
}

static int
adfs_f_read(struct super_block *sb, unsigned int id, unsigned int sz, struct adfs_dir *dir)
{
    int ret;

    if (sz != ADFS_NEWDIR_SIZE)
        return -EIO;

    ret = adfs_dir_read(sb, id, sz, 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->file_id);
    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;
}

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
};