Add support for serialized property contexts
This adds support for reading a serialized
/dev/__properties__/property_info file, which contains a
serialized trie that maps property names to the SELinux context to
which they belong.
Performance wise on walleye, this change reduces the start up cost in
libc from ~3000us to ~430us. On a benchmark that calls
__system_property_find() for each property set on the system, it
reduces the time per iteration from ~650us to ~292us.
Bug: 36001741
Test: Boot bullhead, walleye, run unit tests
Test: Benchmark initialization and lookup performance
Change-Id: I0887a3a7da88eb51b6d1bd494fa5bce593423599
diff --git a/libc/system_properties/contexts_serialized.h b/libc/system_properties/contexts_serialized.h
new file mode 100644
index 0000000..52474c3
--- /dev/null
+++ b/libc/system_properties/contexts_serialized.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef SYSTEM_PROPERTIES_CONTEXTS_SERIALIZED_H
+#define SYSTEM_PROPERTIES_CONTEXTS_SERIALIZED_H
+
+#include <property_info_parser/property_info_parser.h>
+
+#include "context_node.h"
+#include "contexts.h"
+
+class ContextsSerialized : public Contexts {
+ public:
+ virtual ~ContextsSerialized() override {
+ }
+
+ virtual bool Initialize(bool writable) override;
+ virtual prop_area* GetPropAreaForName(const char* name) override;
+ virtual prop_area* GetSerialPropArea() override {
+ return serial_prop_area_;
+ }
+ virtual void ForEach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) override;
+ virtual void ResetAccess() override;
+ virtual void FreeAndUnmap() override;
+
+ private:
+ bool InitializeContextNodes();
+ bool InitializeProperties();
+ bool MapSerialPropertyArea(bool access_rw, bool* fsetxattr_failed);
+
+ android::properties::PropertyInfoAreaFile property_info_area_file_;
+ ContextNode* context_nodes_ = nullptr;
+ size_t num_context_nodes_ = 0;
+ size_t context_nodes_mmap_size_ = 0;
+ prop_area* serial_prop_area_ = nullptr;
+};
+
+#endif