linuxdebug/fs/adfs/dir_f.c

325 lines
7.2 KiB
C
Raw Permalink Normal View History

2024-07-16 15:50:57 +02:00
// 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"
/*
* 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;
fallthrough;
case 3: val |= p[2] << 16;
fallthrough;
case 2: val |= p[1] << 8;
fallthrough;
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;
fallthrough;
case 3: p[2] = val >> 16;
fallthrough;
case 2: p[1] = val >> 8;
fallthrough;
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);\
(void *)(_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;
}
static int adfs_f_validate(struct adfs_dir *dir)
{
struct adfs_dirheader *head = dir->dirhead;
struct adfs_newdirtail *tail = dir->newtail;
if (head->startmasseq != tail->endmasseq ||
tail->dirlastmask || tail->reserved[0] || tail->reserved[1] ||
(memcmp(&head->startname, "Nick", 4) &&
memcmp(&head->startname, "Hugo", 4)) ||
memcmp(&head->startname, &tail->endname, 4) ||
adfs_dir_checkbyte(dir) != tail->dircheckbyte)
return -EIO;
return 0;
}
/* Read and check that a directory is valid */
static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
struct adfs_dir *dir)
{
const unsigned int blocksize_bits = sb->s_blocksize_bits;
int ret;
if (size && size != ADFS_NEWDIR_SIZE)
return -EIO;
ret = adfs_dir_read_buffers(sb, indaddr, ADFS_NEWDIR_SIZE, dir);
if (ret)
return ret;
dir->dirhead = bufoff(dir->bh, 0);
dir->newtail = bufoff(dir->bh, 2007);
if (adfs_f_validate(dir))
goto bad_dir;
dir->parent_id = adfs_readval(dir->newtail->dirparent, 3);
return 0;
bad_dir:
adfs_error(sb, "dir %06x is corrupted", indaddr);
adfs_dir_relse(dir);
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 adfs_direntry de;
int ret;
ret = adfs_dir_copyfrom(&de, dir, pos, 26);
if (ret)
return ret;
if (!de.dirobname[0])
return -ENOENT;
adfs_dir2obj(dir, obj, &de);
return 0;
}
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_iterate(struct adfs_dir *dir, struct dir_context *ctx)
{
struct object_info obj;
int pos = 5 + (ctx->pos - 2) * 26;
while (ctx->pos < 2 + ADFS_NUM_DIR_ENTRIES) {
if (__adfs_dir_get(dir, pos, &obj))
break;
if (!dir_emit(ctx, obj.name, obj.name_len,
obj.indaddr, DT_UNKNOWN))
break;
pos += 26;
ctx->pos++;
}
return 0;
}
static int adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
{
struct adfs_direntry de;
int offset, ret;
offset = 5 - (int)sizeof(de);
do {
offset += sizeof(de);
ret = adfs_dir_copyfrom(&de, dir, offset, sizeof(de));
if (ret) {
adfs_error(dir->sb, "error reading directory entry");
return -ENOENT;
}
if (!de.dirobname[0]) {
adfs_error(dir->sb, "unable to locate entry to update");
return -ENOENT;
}
} while (adfs_readval(de.dirinddiscadd, 3) != obj->indaddr);
/* Update the directory entry with the new object state */
adfs_obj2dir(&de, obj);
/* Write the directory entry back to the directory */
return adfs_dir_copyto(dir, offset, &de, 26);
}
static int adfs_f_commit(struct adfs_dir *dir)
{
int ret;
/* Increment directory sequence number */
dir->dirhead->startmasseq += 1;
dir->newtail->endmasseq += 1;
/* Update directory check byte */
dir->newtail->dircheckbyte = adfs_dir_checkbyte(dir);
/* Make sure the directory still validates correctly */
ret = adfs_f_validate(dir);
if (ret)
adfs_msg(dir->sb, KERN_ERR, "error: update broke directory");
return ret;
}
const struct adfs_dir_ops adfs_f_dir_ops = {
.read = adfs_f_read,
.iterate = adfs_f_iterate,
.setpos = adfs_f_setpos,
.getnext = adfs_f_getnext,
.update = adfs_f_update,
.commit = adfs_f_commit,
};