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/Android.bp b/libc/Android.bp
index 3ec75ee..cba86dd 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1402,6 +1402,7 @@
"bionic/wmempcpy.cpp",
"system_properties/context_node.cpp",
"system_properties/contexts_split.cpp",
+ "system_properties/contexts_serialized.cpp",
"system_properties/prop_area.cpp",
"system_properties/prop_info.cpp",
"system_properties/system_properties.cpp",
@@ -1423,6 +1424,7 @@
cflags: ["-D__ANDROID_TREBLE__"],
},
},
+ whole_static_libs: ["libpropertyinfoparser"],
cppflags: ["-Wold-style-cast"],
local_include_dirs: ["stdio"],
include_dirs: ["bionic/libstdc++/include"],
diff --git a/libc/system_properties/context_node.h b/libc/system_properties/context_node.h
index 1c6cbbb..769b853 100644
--- a/libc/system_properties/context_node.h
+++ b/libc/system_properties/context_node.h
@@ -41,9 +41,16 @@
~ContextNode() {
Unmap();
}
+
+ ContextNode(const ContextNode&) = delete;
+ ContextNode(ContextNode&&) = delete;
+ void operator=(const ContextNode&) = delete;
+ void operator=(const ContextNode&&) = delete;
+
bool Open(bool access_rw, bool* fsetxattr_failed);
bool CheckAccessAndOpen();
void ResetAccess();
+ void Unmap();
const char* context() const {
return context_;
@@ -54,7 +61,6 @@
private:
bool CheckAccess();
- void Unmap();
Lock lock_;
const char* context_;
diff --git a/libc/system_properties/contexts_serialized.cpp b/libc/system_properties/contexts_serialized.cpp
new file mode 100644
index 0000000..117b5cf
--- /dev/null
+++ b/libc/system_properties/contexts_serialized.cpp
@@ -0,0 +1,171 @@
+/*
+ * 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.
+ */
+
+#include "contexts_serialized.h"
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <new>
+
+#include <async_safe/log.h>
+
+#include "private/bionic_prctl.h"
+#include "property_filename.h"
+
+bool ContextsSerialized::InitializeContextNodes() {
+ auto num_context_nodes = property_info_area_file_->num_contexts();
+ auto context_nodes_mmap_size = sizeof(ContextNode) * num_context_nodes;
+ // We want to avoid malloc in system properties, so we take an anonymous map instead (b/31659220).
+ void* const map_result = mmap(nullptr, context_nodes_mmap_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (map_result == MAP_FAILED) {
+ return false;
+ }
+
+ prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map_result, context_nodes_mmap_size,
+ "System property context nodes");
+
+ context_nodes_ = reinterpret_cast<ContextNode*>(map_result);
+ num_context_nodes_ = num_context_nodes;
+ context_nodes_mmap_size_ = context_nodes_mmap_size;
+
+ for (size_t i = 0; i < num_context_nodes; ++i) {
+ new (&context_nodes_[i]) ContextNode(property_info_area_file_->context(i));
+ }
+
+ return true;
+}
+
+bool ContextsSerialized::MapSerialPropertyArea(bool access_rw, bool* fsetxattr_failed) {
+ char filename[PROP_FILENAME_MAX];
+ int len = async_safe_format_buffer(filename, sizeof(filename), "%s/properties_serial",
+ property_filename);
+ if (len < 0 || len > PROP_FILENAME_MAX) {
+ serial_prop_area_ = nullptr;
+ return false;
+ }
+
+ if (access_rw) {
+ serial_prop_area_ =
+ prop_area::map_prop_area_rw(filename, "u:object_r:properties_serial:s0", fsetxattr_failed);
+ } else {
+ serial_prop_area_ = prop_area::map_prop_area(filename);
+ }
+ return serial_prop_area_;
+}
+
+bool ContextsSerialized::InitializeProperties() {
+ if (!property_info_area_file_.LoadDefaultPath()) {
+ return false;
+ }
+
+ if (!InitializeContextNodes()) {
+ FreeAndUnmap();
+ return false;
+ }
+
+ return true;
+}
+
+bool ContextsSerialized::Initialize(bool writable) {
+ if (!InitializeProperties()) {
+ return false;
+ }
+
+ if (writable) {
+ mkdir(property_filename, S_IRWXU | S_IXGRP | S_IXOTH);
+ bool open_failed = false;
+ bool fsetxattr_failed = false;
+
+ for (size_t i = 0; i < num_context_nodes_; ++i) {
+ if (!context_nodes_[i].Open(true, &fsetxattr_failed)) {
+ open_failed = true;
+ }
+ }
+ if (open_failed || !MapSerialPropertyArea(true, &fsetxattr_failed)) {
+ FreeAndUnmap();
+ return false;
+ }
+
+ return !fsetxattr_failed;
+ } else {
+ if (!MapSerialPropertyArea(false, nullptr)) {
+ FreeAndUnmap();
+ return false;
+ }
+ }
+ return true;
+}
+
+prop_area* ContextsSerialized::GetPropAreaForName(const char* name) {
+ uint32_t index;
+ property_info_area_file_->GetPropertyInfoIndexes(name, &index, nullptr);
+ if (index == ~0u || index >= num_context_nodes_) {
+ async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Could not find context for property \"%s\"",
+ name);
+ return nullptr;
+ }
+ auto* context_node = &context_nodes_[index];
+ if (!context_node->pa()) {
+ // We explicitly do not check no_access_ in this case because unlike the
+ // case of foreach(), we want to generate an selinux audit for each
+ // non-permitted property access in this function.
+ context_node->Open(false, nullptr);
+ }
+ return context_node->pa();
+}
+
+void ContextsSerialized::ForEach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
+ for (size_t i = 0; i < num_context_nodes_; ++i) {
+ if (context_nodes_[i].CheckAccessAndOpen()) {
+ context_nodes_[i].pa()->foreach (propfn, cookie);
+ }
+ }
+}
+
+void ContextsSerialized::ResetAccess() {
+ for (size_t i = 0; i < num_context_nodes_; ++i) {
+ context_nodes_[i].ResetAccess();
+ }
+}
+
+void ContextsSerialized::FreeAndUnmap() {
+ property_info_area_file_.Reset();
+ if (context_nodes_ != nullptr) {
+ for (size_t i = 0; i < num_context_nodes_; ++i) {
+ context_nodes_[i].Unmap();
+ }
+ munmap(context_nodes_, context_nodes_mmap_size_);
+ context_nodes_ = nullptr;
+ }
+ prop_area::unmap_prop_area(&serial_prop_area_);
+ serial_prop_area_ = nullptr;
+}
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
diff --git a/libc/system_properties/system_properties.cpp b/libc/system_properties/system_properties.cpp
index 89a6fe7..f67fc4d 100644
--- a/libc/system_properties/system_properties.cpp
+++ b/libc/system_properties/system_properties.cpp
@@ -59,6 +59,7 @@
#include "context_node.h"
#include "contexts.h"
#include "contexts_pre_split.h"
+#include "contexts_serialized.h"
#include "contexts_split.h"
#include "prop_area.h"
#include "prop_info.h"
@@ -71,6 +72,7 @@
static union ContextsUnion {
ContextsUnion() {}
~ContextsUnion() {}
+ ContextsSerialized contexts_serialized;
ContextsSplit contexts_split;
ContextsPreSplit contexts_pre_split;
} contexts_union;
@@ -283,11 +285,19 @@
}
contexts = nullptr;
if (is_dir(property_filename)) {
- new (&contexts_union.contexts_split) ContextsSplit();
- if (!contexts_union.contexts_split.Initialize(false)) {
- return -1;
+ if (access("/dev/__properties__/property_info", R_OK) == 0) {
+ new (&contexts_union.contexts_serialized) ContextsSerialized();
+ if (!contexts_union.contexts_serialized.Initialize(false)) {
+ return -1;
+ }
+ contexts = &contexts_union.contexts_serialized;
+ } else {
+ new (&contexts_union.contexts_split) ContextsSplit();
+ if (!contexts_union.contexts_split.Initialize(false)) {
+ return -1;
+ }
+ contexts = &contexts_union.contexts_split;
}
- contexts = &contexts_union.contexts_split;
} else {
new (&contexts_union.contexts_pre_split) ContextsPreSplit();
if (!contexts_union.contexts_pre_split.Initialize(false)) {
@@ -314,9 +324,9 @@
}
// We set this unconditionally as we want tests to continue on regardless of if this failed
// and property_service will abort on an error condition, so no harm done.
- new (&contexts_union.contexts_split) ContextsSplit;
- contexts = &contexts_union.contexts_split;
- if (!contexts_union.contexts_split.Initialize(true)) {
+ new (&contexts_union.contexts_serialized) ContextsSerialized;
+ contexts = &contexts_union.contexts_serialized;
+ if (!contexts_union.contexts_serialized.Initialize(true)) {
return -1;
}
return 0;