attrib.c

linux 内核源代码

		unmap_extent_mft_record(ni);
	ctx->mrec = ctx->base_mrec;
	ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
			le16_to_cpu(ctx->mrec->attrs_offset));
	ctx->is_first = true;
	ctx->ntfs_ino = base_ni;
	ctx->base_ntfs_ino = NULL;
	ctx->base_mrec = NULL;
	ctx->base_attr = NULL;
	/*
	 * In case there are multiple matches in the base mft record, need to
	 * keep enumerating until we get an attribute not found response (or
	 * another error), otherwise we would keep returning the same attribute
	 * over and over again and all programs using us for enumeration would
	 * lock up in a tight loop.
	 */
	do {
		err = ntfs_attr_find(type, name, name_len, ic, val, val_len,
				ctx);
	} while (!err);
	ntfs_debug("Done, not found.");
	return err;
}

/**
 * ntfs_attr_lookup - find an attribute in an ntfs inode
 * @type:	attribute type to find
 * @name:	attribute name to find (optional, i.e. NULL means don't care)
 * @name_len:	attribute name length (only needed if @name present)
 * @ic:		IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
 * @lowest_vcn:	lowest vcn to find (optional, non-resident attributes only)
 * @val:	attribute value to find (optional, resident attributes only)
 * @val_len:	attribute value length
 * @ctx:	search context with mft record and attribute to search from
 *
 * Find an attribute in an ntfs inode.  On first search @ctx->ntfs_ino must
 * be the base mft record and @ctx must have been obtained from a call to
 * ntfs_attr_get_search_ctx().
 *
 * This function transparently handles attribute lists and @ctx is used to
 * continue searches where they were left off at.
 *
 * After finishing with the attribute/mft record you need to call
 * ntfs_attr_put_search_ctx() to cleanup the search context (unmapping any
 * mapped inodes, etc).
 *
 * Return 0 if the search was successful and -errno if not.
 *
 * When 0, @ctx->attr is the found attribute and it is in mft record
 * @ctx->mrec.  If an attribute list attribute is present, @ctx->al_entry is
 * the attribute list entry of the found attribute.
 *
 * When -ENOENT, @ctx->attr is the attribute which collates just after the
 * attribute being searched for, i.e. if one wants to add the attribute to the
 * mft record this is the correct place to insert it into.  If an attribute
 * list attribute is present, @ctx->al_entry is the attribute list entry which
 * collates just after the attribute list entry of the attribute being searched
 * for, i.e. if one wants to add the attribute to the mft record this is the
 * correct place to insert its attribute list entry into.
 *
 * When -errno != -ENOENT, an error occured during the lookup.  @ctx->attr is
 * then undefined and in particular you should not rely on it not changing.
 */
int ntfs_attr_lookup(const ATTR_TYPE type, const ntfschar *name,
		const u32 name_len, const IGNORE_CASE_BOOL ic,
		const VCN lowest_vcn, const u8 *val, const u32 val_len,
		ntfs_attr_search_ctx *ctx)
{
	ntfs_inode *base_ni;

	ntfs_debug("Entering.");
	BUG_ON(IS_ERR(ctx->mrec));
	if (ctx->base_ntfs_ino)
		base_ni = ctx->base_ntfs_ino;
	else
		base_ni = ctx->ntfs_ino;
	/* Sanity check, just for debugging really. */
	BUG_ON(!base_ni);
	if (!NInoAttrList(base_ni) || type == AT_ATTRIBUTE_LIST)
		return ntfs_attr_find(type, name, name_len, ic, val, val_len,
				ctx);
	return ntfs_external_attr_find(type, name, name_len, ic, lowest_vcn,
			val, val_len, ctx);
}

/**
 * ntfs_attr_init_search_ctx - initialize an attribute search context
 * @ctx:	attribute search context to initialize
 * @ni:		ntfs inode with which to initialize the search context
 * @mrec:	mft record with which to initialize the search context
 *
 * Initialize the attribute search context @ctx with @ni and @mrec.
 */
static inline void ntfs_attr_init_search_ctx(ntfs_attr_search_ctx *ctx,
		ntfs_inode *ni, MFT_RECORD *mrec)
{
	*ctx = (ntfs_attr_search_ctx) {
		.mrec = mrec,
		/* Sanity checks are performed elsewhere. */
		.attr = (ATTR_RECORD*)((u8*)mrec +
				le16_to_cpu(mrec->attrs_offset)),
		.is_first = true,
		.ntfs_ino = ni,
	};
}

/**
 * ntfs_attr_reinit_search_ctx - reinitialize an attribute search context
 * @ctx:	attribute search context to reinitialize
 *
 * Reinitialize the attribute search context @ctx, unmapping an associated
 * extent mft record if present, and initialize the search context again.
 *
 * This is used when a search for a new attribute is being started to reset
 * the search context to the beginning.
 */
void ntfs_attr_reinit_search_ctx(ntfs_attr_search_ctx *ctx)
{
	if (likely(!ctx->base_ntfs_ino)) {
		/* No attribute list. */
		ctx->is_first = true;
		/* Sanity checks are performed elsewhere. */
		ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
				le16_to_cpu(ctx->mrec->attrs_offset));
		/*
		 * This needs resetting due to ntfs_external_attr_find() which
		 * can leave it set despite having zeroed ctx->base_ntfs_ino.
		 */
		ctx->al_entry = NULL;
		return;
	} /* Attribute list. */
	if (ctx->ntfs_ino != ctx->base_ntfs_ino)
		unmap_extent_mft_record(ctx->ntfs_ino);
	ntfs_attr_init_search_ctx(ctx, ctx->base_ntfs_ino, ctx->base_mrec);
	return;
}

/**
 * ntfs_attr_get_search_ctx - allocate/initialize a new attribute search context
 * @ni:		ntfs inode with which to initialize the search context
 * @mrec:	mft record with which to initialize the search context
 *
 * Allocate a new attribute search context, initialize it with @ni and @mrec,
 * and return it. Return NULL if allocation failed.
 */
ntfs_attr_search_ctx *ntfs_attr_get_search_ctx(ntfs_inode *ni, MFT_RECORD *mrec)
{
	ntfs_attr_search_ctx *ctx;

	ctx = kmem_cache_alloc(ntfs_attr_ctx_cache, GFP_NOFS);
	if (ctx)
		ntfs_attr_init_search_ctx(ctx, ni, mrec);
	return ctx;
}

/**
 * ntfs_attr_put_search_ctx - release an attribute search context
 * @ctx:	attribute search context to free
 *
 * Release the attribute search context @ctx, unmapping an associated extent
 * mft record if present.
 */
void ntfs_attr_put_search_ctx(ntfs_attr_search_ctx *ctx)
{
	if (ctx->base_ntfs_ino && ctx->ntfs_ino != ctx->base_ntfs_ino)
		unmap_extent_mft_record(ctx->ntfs_ino);
	kmem_cache_free(ntfs_attr_ctx_cache, ctx);
	return;
}

#ifdef NTFS_RW

/**
 * ntfs_attr_find_in_attrdef - find an attribute in the $AttrDef system file
 * @vol:	ntfs volume to which the attribute belongs
 * @type:	attribute type which to find
 *
 * Search for the attribute definition record corresponding to the attribute
 * @type in the $AttrDef system file.
 *
 * Return the attribute type definition record if found and NULL if not found.
 */
static ATTR_DEF *ntfs_attr_find_in_attrdef(const ntfs_volume *vol,
		const ATTR_TYPE type)
{
	ATTR_DEF *ad;

	BUG_ON(!vol->attrdef);
	BUG_ON(!type);
	for (ad = vol->attrdef; (u8*)ad - (u8*)vol->attrdef <
			vol->attrdef_size && ad->type; ++ad) {
		/* We have not found it yet, carry on searching. */
		if (likely(le32_to_cpu(ad->type) < le32_to_cpu(type)))
			continue;
		/* We found the attribute; return it. */
		if (likely(ad->type == type))
			return ad;
		/* We have gone too far already.  No point in continuing. */
		break;
	}
	/* Attribute not found. */
	ntfs_debug("Attribute type 0x%x not found in $AttrDef.",
			le32_to_cpu(type));
	return NULL;
}

/**
 * ntfs_attr_size_bounds_check - check a size of an attribute type for validity
 * @vol:	ntfs volume to which the attribute belongs
 * @type:	attribute type which to check
 * @size:	size which to check
 *
 * Check whether the @size in bytes is valid for an attribute of @type on the
 * ntfs volume @vol.  This information is obtained from $AttrDef system file.
 *
 * Return 0 if valid, -ERANGE if not valid, or -ENOENT if the attribute is not
 * listed in $AttrDef.
 */
int ntfs_attr_size_bounds_check(const ntfs_volume *vol, const ATTR_TYPE type,
		const s64 size)
{
	ATTR_DEF *ad;

	BUG_ON(size < 0);
	/*
	 * $ATTRIBUTE_LIST has a maximum size of 256kiB, but this is not
	 * listed in $AttrDef.
	 */
	if (unlikely(type == AT_ATTRIBUTE_LIST && size > 256 * 1024))
		return -ERANGE;
	/* Get the $AttrDef entry for the attribute @type. */
	ad = ntfs_attr_find_in_attrdef(vol, type);
	if (unlikely(!ad))
		return -ENOENT;
	/* Do the bounds check. */
	if (((sle64_to_cpu(ad->min_size) > 0) &&
			size < sle64_to_cpu(ad->min_size)) ||
			((sle64_to_cpu(ad->max_size) > 0) && size >
			sle64_to_cpu(ad->max_size)))
		return -ERANGE;
	return 0;
}

/**
 * ntfs_attr_can_be_non_resident - check if an attribute can be non-resident
 * @vol:	ntfs volume to which the attribute belongs
 * @type:	attribute type which to check
 *
 * Check whether the attribute of @type on the ntfs volume @vol is allowed to
 * be non-resident.  This information is obtained from $AttrDef system file.
 *
 * Return 0 if the attribute is allowed to be non-resident, -EPERM if not, and
 * -ENOENT if the attribute is not listed in $AttrDef.
 */
int ntfs_attr_can_be_non_resident(const ntfs_volume *vol, const ATTR_TYPE type)
{
	ATTR_DEF *ad;

	/* Find the attribute definition record in $AttrDef. */
	ad = ntfs_attr_find_in_attrdef(vol, type);
	if (unlikely(!ad))
		return -ENOENT;
	/* Check the flags and return the result. */
	if (ad->flags & ATTR_DEF_RESIDENT)
		return -EPERM;
	return 0;
}

/**
 * ntfs_attr_can_be_resident - check if an attribute can be resident
 * @vol:	ntfs volume to which the attribute belongs
 * @type:	attribute type which to check
 *
 * Check whether the attribute of @type on the ntfs volume @vol is allowed to
 * be resident.  This information is derived from our ntfs knowledge and may
 * not be completely accurate, especially when user defined attributes are
 * present.  Basically we allow everything to be resident except for index
 * allocation and $EA attributes.
 *
 * Return 0 if the attribute is allowed to be non-resident and -EPERM if not.
 *
 * Warning: In the system file $MFT the attribute $Bitmap must be non-resident
 *	    otherwise windows will not boot (blue screen of death)!  We cannot
 *	    check for this here as we do not know which inode's $Bitmap is
 *	    being asked about so the caller needs to special case this.
 */
int ntfs_attr_can_be_resident(const ntfs_volume *vol, const ATTR_TYPE type)
{
	if (type == AT_INDEX_ALLOCATION)
		return -EPERM;
	return 0;
}

/**
 * ntfs_attr_record_resize - resize an attribute record
 * @m:		mft record containing attribute record
 * @a:		attribute record to resize
 * @new_size:	new size in bytes to which to resize the attribute record @a
 *
 * Resize the attribute record @a, i.e. the resident part of the attribute, in
 * the mft record @m to @new_size bytes.
 *
 * Return 0 on success and -errno on error.  The following error codes are
 * defined:
 *	-ENOSPC	- Not enough space in the mft record @m to perform the resize.
 *
 * Note: On error, no modifications have been performed whatsoever.
 *
 * Warning: If you make a record smaller without having copied all the data you
 *	    are interested in the data may be overwritten.
 */
int ntfs_attr_record_resize(MFT_RECORD *m, ATTR_RECORD *a, u32 new_size)
{
	ntfs_debug("Entering for new_size %u.", new_size);
	/* Align to 8 bytes if it is not already done. */
	if (new_size & 7)
		new_size = (new_size + 7) & ~7;
	/* If the actual attribute length has changed, move things around. */
	if (new_size != le32_to_cpu(a->length)) {
		u32 new_muse = le32_to_cpu(m->bytes_in_use) -
				le32_to_cpu(a->length) + new_size;
		/* Not enough space in this mft record. */
		if (new_muse > le32_to_cpu(m->bytes_allocated))
			return -ENOSPC;
		/* Move attributes following @a to their new location. */
		memmove((u8*)a + new_size, (u8*)a + le32_to_cpu(a->length),
				le32_to_cpu(m->bytes_in_use) - ((u8*)a -
				(u8*)m) - le32_to_cpu(a->length));
		/* Adjust @m to reflect the change in used space. */
		m->bytes_in_use = cpu_to_le32(new_muse);
		/* Adjust @a to reflect the new size. */
		if (new_size >= offsetof(ATTR_REC, length) + sizeof(a->length))
			a->length = cpu_to_le32(new_size);
	}
	return 0;
}

/**
 * ntfs_resident_attr_value_resize - resize the value of a resident attribute
 * @m:		mft record containing attribute record
 * @a:		attribute record whose value to resize
 * @new_size:	new size in bytes to which to resize the attribute value of @a
 *
 * Resize the value of the attribute @a in the mft record @m to @new_size bytes.
 * If the value is made bigger, the newly allocated space is cleared.
 *
 * Return 0 on success and -errno on error.  The following error codes are
 * defined:
 *	-ENOSPC	- Not enough space in the mft record @m to perform the resize.
 *
 * Note: On error, no modifications have been performed whatsoever.
 *
 * Warning: If you make a record smaller without having copied all the data you
 *	    are interested in the data may be overwritten.
 */
int ntfs_resident_attr_value_resize(MFT_RECORD *m, ATTR_RECORD *a,
		const u32 new_size)
{
	u32 old_size;

	/* Resize the resident part of the attribute record. */
	if (ntfs_attr_record_resize(m, a,
			le16_to_cpu(a->data.resident.value_offset) + new_size))
		return -ENOSPC;
	/*
	 * The resize succeeded!  If we made the attribute value bigger, clear
	 * the area between the old size and @new_size.
	 */
	old_size = le32_to_cpu(a->data.resident.value_length);
	if (new_size > old_size)
		memset((u8*)a + le16_to_cpu(a->data.resident.value_offset) +
				old_size, 0, new_size - old_size);
	/* Finally update the length of the attribute value. */
	a->data.resident.value_length = cpu_to_le32(new_size);