1 files changed, 279 insertions, 0 deletions
diff --git a/lib/sqfshelper/write_xattr.c b/lib/sqfshelper/write_xattr.c
new file mode 100644
index 0000000..2263fbe
--- /dev/null
+++ b/lib/sqfshelper/write_xattr.c
@@ -0,0 +1,279 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * write_xattr.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "meta_writer.h"
+#include "highlevel.h"
+#include "util.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+static int write_key(meta_writer_t *mw, const char *key, tree_xattr_t *xattr,
+		     bool value_is_ool)
+{
+	sqfs_xattr_entry_t kent;
+	int type;
+
+	type = sqfs_get_xattr_prefix_id(key);
+	if (type < 0) {
+		fprintf(stderr, "unsupported xattr key '%s'\n", key);
+		return -1;
+	}
+
+	key = strchr(key, '.');
+	assert(key != NULL);
+	++key;
+
+	if (value_is_ool)
+		type |= SQUASHFS_XATTR_FLAG_OOL;
+
+	kent.type = htole16(type);
+	kent.size = htole16(strlen(key));
+
+	if (meta_writer_append(mw, &kent, sizeof(kent)))
+		return -1;
+	if (meta_writer_append(mw, key, strlen(key)))
+		return -1;
+
+	xattr->size += sizeof(sqfs_xattr_entry_t) + strlen(key);
+	return 0;
+}
+
+static int write_value(meta_writer_t *mw, const char *value,
+		       tree_xattr_t *xattr, uint64_t *value_ref_out)
+{
+	sqfs_xattr_value_t vent;
+	uint32_t offset;
+	uint64_t block;
+
+	meta_writer_get_position(mw, &block, &offset);
+	*value_ref_out = (block << 16) | (offset & 0xFFFF);
+
+	vent.size = htole32(strlen(value));
+
+	if (meta_writer_append(mw, &vent, sizeof(vent)))
+		return -1;
+
+	if (meta_writer_append(mw, value, strlen(value)))
+		return -1;
+
+	xattr->size += sizeof(vent) + strlen(value);
+	return 0;
+}
+
+static int write_value_ool(meta_writer_t *mw, uint64_t location,
+			   tree_xattr_t *xattr)
+{
+	sqfs_xattr_value_t vent;
+	uint64_t ref;
+
+	vent.size = htole32(sizeof(location));
+	if (meta_writer_append(mw, &vent, sizeof(vent)))
+		return -1;
+
+	ref = htole64(location);
+	if (meta_writer_append(mw, &ref, sizeof(ref)))
+		return -1;
+
+	xattr->size += sizeof(vent) + sizeof(ref);
+	return 0;
+}
+
+static bool should_store_ool(fstree_t *fs, const char *value, size_t index)
+{
+	size_t refcount;
+
+	refcount = str_table_get_ref_count(&fs->xattr_values, index);
+	if (refcount < 2)
+		return false;
+
+	/*
+	  Storing in line needs this many bytes: refcount * len
+
+	  Storing out-of-line needs this many: len + (refcount - 1) * 8
+
+	  Out-of-line prefereable if:
+	      refcount * len > len + (refcount - 1) * 8
+	   => refcount * len - len > (refcount - 1) * 8
+	   => (refcount - 1) * len > (refcount - 1) * 8
+	   => len > 8
+
+	   Note that this only holds iff refcount - 1 != 0, i.e. refcount > 1,
+	   otherwise we would be dividing by 0 in the 3rd step.
+	 */
+	return strlen(value) > sizeof(uint64_t);
+}
+
+static int write_kv_pairs(fstree_t *fs, meta_writer_t *mw, tree_xattr_t *xattr,
+			  uint64_t *ool_locations)
+{
+	uint32_t key_idx, val_idx;
+	const char *key, *value;
+	uint64_t ref;
+	size_t i;
+
+	for (i = 0; i < xattr->num_attr; ++i) {
+		key_idx = xattr->attr[i].key_index;
+		val_idx = xattr->attr[i].value_index;
+
+		key = str_table_get_string(&fs->xattr_keys, key_idx);
+		value = str_table_get_string(&fs->xattr_values, val_idx);
+
+		if (ool_locations[val_idx] == 0xFFFFFFFFFFFFFFFF) {
+			if (write_key(mw, key, xattr, false))
+				return -1;
+
+			if (write_value(mw, value, xattr, &ref))
+				return -1;
+
+			if (should_store_ool(fs, value, val_idx))
+				ool_locations[val_idx] = ref;
+		} else {
+			if (write_key(mw, key, xattr, true))
+				return -1;
+
+			if (write_value_ool(mw, ool_locations[val_idx], xattr))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+static uint64_t *create_ool_locations_table(fstree_t *fs)
+{
+	uint64_t *table;
+	size_t i;
+
+	table = alloc_array(sizeof(uint64_t), fs->xattr_values.num_strings);
+
+	if (table == NULL) {
+		perror("allocating Xattr OOL locations table");
+		return NULL;
+	}
+
+	for (i = 0; i < fs->xattr_values.num_strings; ++i) {
+		table[i] = 0xFFFFFFFFFFFFFFFFUL;
+	}
+
+	return table;
+}
+
+int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
+		compressor_t *cmp)
+{
+	uint64_t kv_start, id_start, block, *tbl, *ool_locations;
+	size_t i = 0, count = 0, blocks;
+	sqfs_xattr_id_table_t idtbl;
+	sqfs_xattr_id_t id_ent;
+	meta_writer_t *mw;
+	tree_xattr_t *it;
+	uint32_t offset;
+
+	if (fs->xattr == NULL)
+		return 0;
+
+	ool_locations = create_ool_locations_table(fs);
+	if (ool_locations == NULL)
+		return -1;
+
+	mw = meta_writer_create(outfd, cmp, false);
+	if (mw == NULL)
+		goto fail_ool;
+
+	/* write xattr key-value pairs */
+	kv_start = super->bytes_used;
+
+	for (it = fs->xattr; it != NULL; it = it->next) {
+		meta_writer_get_position(mw, &it->block, &it->offset);
+		it->size = 0;
+
+		if (write_kv_pairs(fs, mw, it, ool_locations))
+			goto fail_mw;
+
+		++count;
+	}
+
+	if (meta_writer_flush(mw))
+		goto fail_mw;
+
+	meta_writer_get_position(mw, &block, &offset);
+	meta_writer_reset(mw);
+
+	super->bytes_used += block;
+
+	/* allocate location table */
+	blocks = (count * sizeof(id_ent)) / SQFS_META_BLOCK_SIZE;
+
+	if ((count * sizeof(id_ent)) % SQFS_META_BLOCK_SIZE)
+		++blocks;
+
+	tbl = alloc_array(sizeof(uint64_t), blocks);
+
+	if (tbl == NULL) {
+		perror("generating xattr ID table");
+		goto fail_mw;
+	}
+
+	/* write ID table referring to key value pairs, record offsets */
+	id_start = 0;
+	tbl[i++] = htole64(super->bytes_used);
+
+	for (it = fs->xattr; it != NULL; it = it->next) {
+		id_ent.xattr = htole64((it->block << 16) | it->offset);
+		id_ent.count = htole32(it->num_attr);
+		id_ent.size = htole32(it->size);
+
+		if (meta_writer_append(mw, &id_ent, sizeof(id_ent)))
+			goto fail_tbl;
+
+		meta_writer_get_position(mw, &block, &offset);
+
+		if (block != id_start) {
+			id_start = block;
+			tbl[i++] = htole64(super->bytes_used + id_start);
+		}
+	}
+
+	if (meta_writer_flush(mw))
+		goto fail_tbl;
+
+	meta_writer_get_position(mw, &block, &offset);
+	super->bytes_used += block;
+
+	/* write offset table */
+	idtbl.xattr_table_start = htole64(kv_start);
+	idtbl.xattr_ids = htole32(count);
+	idtbl.unused = 0;
+
+	if (write_data("writing xattr ID table", outfd, &idtbl, sizeof(idtbl)))
+		goto fail_tbl;
+
+	if (write_data("writing xattr ID table",
+		       outfd, tbl, sizeof(tbl[0]) * blocks)) {
+		goto fail_tbl;
+	}
+
+	super->xattr_id_table_start = super->bytes_used;
+	super->bytes_used += sizeof(idtbl) + sizeof(tbl[0]) * blocks;
+	super->flags &= ~SQFS_FLAG_NO_XATTRS;
+
+	free(tbl);
+	meta_writer_destroy(mw);
+	free(ool_locations);
+	return 0;
+fail_tbl:
+	free(tbl);
+fail_mw:
+	meta_writer_destroy(mw);
+fail_ool:
+	free(ool_locations);
+	return -1;
+}