diff --git a/libc/system_properties/prop_info.cpp b/libc/system_properties/prop_info.cpp
new file mode 100644
index 0000000..5123f92
--- /dev/null
+++ b/libc/system_properties/prop_info.cpp
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "prop_info.h"
+
+#include <string.h>
+
+constexpr static const char kLongLegacyError[] =
+    "Must use __system_property_read_callback() to read";
+static_assert(sizeof(kLongLegacyError) < prop_info::kLongLegacyErrorBufferSize,
+              "Error message for long properties read by legacy libc must fit within 56 chars");
+
+prop_info::prop_info(const char* name, uint32_t namelen, const char* value, uint32_t valuelen) {
+  memcpy(this->name, name, namelen);
+  this->name[namelen] = '\0';
+  atomic_init(&this->serial, valuelen << 24);
+  memcpy(this->value, value, valuelen);
+  this->value[valuelen] = '\0';
+}
+
+prop_info::prop_info(const char* name, uint32_t namelen, uint32_t long_offset) {
+  memcpy(this->name, name, namelen);
+  this->name[namelen] = '\0';
+
+  auto error_value_len = sizeof(kLongLegacyError) - 1;
+  atomic_init(&this->serial, error_value_len << 24 | kLongFlag);
+  memcpy(this->long_property.error_message, kLongLegacyError, sizeof(kLongLegacyError));
+
+  this->long_property.offset = long_offset;
+}