linker/linker_config.cpp - android_bionic - Gitiles

 /*
  * 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 "linker_config.h"

 #include "linker_globals.h"
 #include "linker_debug.h"
 #include "linker_utils.h"

 #include <android-base/file.h>
 #include <android-base/properties.h>
 #include <android-base/scopeguard.h>
 #include <android-base/strings.h>

 #include <async_safe/log.h>

 #include <limits.h>
 #include <stdlib.h>
 #include <unistd.h>

 #include <string>
 #include <unordered_map>

 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
 #include <sys/_system_properties.h>

 class ConfigParser {
  public:
   enum {
     kPropertyAssign,
     kPropertyAppend,
     kSection,
     kEndOfFile,
     kError,
   };

   explicit ConfigParser(std::string&& content)
       : content_(std::move(content)), p_(0), lineno_(0), was_end_of_file_(false) {}

   /*
    * Possible return values
    * kPropertyAssign: name is set to property name and value is set to property value
    * kPropertyAppend: same as kPropertyAssign, but the value should be appended
    * kSection: name is set to section name.
    * kEndOfFile: reached end of file.
    * kError: error_msg is set.
    */
   int next_token(std::string* name, std::string* value, std::string* error_msg) {
     std::string line;
     while(NextLine(&line)) {
       size_t found = line.find('#');
       line = android::base::Trim(line.substr(0, found));

       if (line.empty()) {
         continue;
       }

       if (line[0] == '[' && line.back() == ']') {
         *name = line.substr(1, line.size() - 2);
         return kSection;
       }

       size_t found_assign = line.find('=');
       size_t found_append = line.find("+=");
       if (found_assign != std::string::npos && found_append == std::string::npos) {
         *name = android::base::Trim(line.substr(0, found_assign));
         *value = android::base::Trim(line.substr(found_assign + 1));
         return kPropertyAssign;
       }

       if (found_append != std::string::npos) {
         *name = android::base::Trim(line.substr(0, found_append));
         *value = android::base::Trim(line.substr(found_append + 2));
         return kPropertyAppend;
       }

       *error_msg = std::string("invalid format: ") +
                    line +
                    ", expected \"name = property\", \"name += property\", or \"[section]\"";
       return kError;
     }

     // to avoid infinite cycles when programmer makes a mistake
     CHECK(!was_end_of_file_);
     was_end_of_file_ = true;
     return kEndOfFile;
   }

   size_t lineno() const {
     return lineno_;
   }

  private:
   bool NextLine(std::string* line) {
     if (p_ == std::string::npos) {
       return false;
     }

     size_t found = content_.find('\n', p_);
     if (found != std::string::npos) {
       *line = content_.substr(p_, found - p_);
       p_ = found + 1;
     } else {
       *line = content_.substr(p_);
       p_ = std::string::npos;
     }

     lineno_++;
     return true;
   }

   std::string content_;
   size_t p_;
   size_t lineno_;
   bool was_end_of_file_;

   DISALLOW_IMPLICIT_CONSTRUCTORS(ConfigParser);
 };

 class PropertyValue {
  public:
   PropertyValue() = default;

   PropertyValue(std::string&& value, size_t lineno)
     : value_(std::move(value)), lineno_(lineno) {}

   const std::string& value() const {
     return value_;
   }

   void append_value(std::string&& value) {
     value_ = value_ + value;
     // lineno isn't updated as we might have cases like this:
     // property.x = blah
     // property.y = blah
     // property.x += blah
   }

   size_t lineno() const {
     return lineno_;
   }

  private:
   std::string value_;
   size_t lineno_;
 };

 static std::string create_error_msg(const char* file,
                                     size_t lineno,
                                     const std::string& msg) {
   char buf[1024];
   async_safe_format_buffer(buf, sizeof(buf), "%s:%zu: error: %s", file, lineno, msg.c_str());

   return std::string(buf);
 }

 static bool parse_config_file(const char* ld_config_file_path,
                               const char* binary_realpath,
                               std::unordered_map<std::string, PropertyValue>* properties,
                               std::string* error_msg) {
   std::string content;
   if (!android::base::ReadFileToString(ld_config_file_path, &content)) {
     if (errno != ENOENT) {
       *error_msg = std::string("error reading file \"") +
                    ld_config_file_path + "\": " + strerror(errno);
     }
     return false;
   }

   ConfigParser cp(std::move(content));

   std::string section_name;

   while (true) {
     std::string name;
     std::string value;
     std::string error;

     int result = cp.next_token(&name, &value, &error);
     if (result == ConfigParser::kError) {
       DL_WARN("%s:%zd: warning: couldn't parse %s (ignoring this line)",
               ld_config_file_path,
               cp.lineno(),
               error.c_str());
       continue;
     }

     if (result == ConfigParser::kSection || result == ConfigParser::kEndOfFile) {
       return false;
     }

     if (result == ConfigParser::kPropertyAssign) {
       if (!android::base::StartsWith(name, "dir.")) {
         DL_WARN("%s:%zd: warning: unexpected property name \"%s\", "
                 "expected format dir.<section_name> (ignoring this line)",
                 ld_config_file_path,
                 cp.lineno(),
                 name.c_str());
         continue;
       }

       // remove trailing '/'
       while (!value.empty() && value.back() == '/') {
         value.pop_back();
       }

       if (value.empty()) {
         DL_WARN("%s:%zd: warning: property value is empty (ignoring this line)",
                 ld_config_file_path,
                 cp.lineno());
         continue;
       }

       // If the path can be resolved, resolve it
       char buf[PATH_MAX];
       std::string resolved_path;
       if (access(value.c_str(), R_OK) != 0) {
         if (errno == ENOENT) {
           // no need to test for non-existing path. skip.
           continue;
         }
         // If not accessible, don't call realpath as it will just cause
         // SELinux denial spam. Use the path unresolved.
         resolved_path = value;
       } else if (realpath(value.c_str(), buf)) {
         resolved_path = buf;
       } else {
         // realpath is expected to fail with EPERM in some situations, so log
         // the failure with INFO rather than DL_WARN. e.g. A binary in
         // /data/local/tmp may attempt to stat /postinstall. See
         // http://b/120996057.
         INFO("%s:%zd: warning: path \"%s\" couldn't be resolved: %s",
              ld_config_file_path,
              cp.lineno(),
              value.c_str(),
              strerror(errno));
         resolved_path = value;
       }

       if (file_is_under_dir(binary_realpath, resolved_path)) {
         section_name = name.substr(4);
         break;
       }
     }
   }

   INFO("[ Using config section \"%s\" ]", section_name.c_str());

   // skip everything until we meet a correct section
   while (true) {
     std::string name;
     std::string value;
     std::string error;

     int result = cp.next_token(&name, &value, &error);

     if (result == ConfigParser::kSection && name == section_name) {
       break;
     }

     if (result == ConfigParser::kEndOfFile) {
       *error_msg = create_error_msg(ld_config_file_path,
                                     cp.lineno(),
                                     std::string("section \"") + section_name + "\" not found");
       return false;
     }
   }

   // found the section - parse it
   while (true) {
     std::string name;
     std::string value;
     std::string error;

     int result = cp.next_token(&name, &value, &error);

     if (result == ConfigParser::kEndOfFile || result == ConfigParser::kSection) {
       break;
     }

     if (result == ConfigParser::kPropertyAssign) {
       if (properties->find(name) != properties->end()) {
         DL_WARN("%s:%zd: warning: redefining property \"%s\" (overriding previous value)",
                 ld_config_file_path,
                 cp.lineno(),
                 name.c_str());
       }

       (*properties)[name] = PropertyValue(std::move(value), cp.lineno());
     } else if (result == ConfigParser::kPropertyAppend) {
       if (properties->find(name) == properties->end()) {
         DL_WARN("%s:%zd: warning: appending to undefined property \"%s\" (treating as assignment)",
                 ld_config_file_path,
                 cp.lineno(),
                 name.c_str());
         (*properties)[name] = PropertyValue(std::move(value), cp.lineno());
       } else {
         if (android::base::EndsWith(name, ".links") ||
             android::base::EndsWith(name, ".namespaces")) {
           value = "," + value;
           (*properties)[name].append_value(std::move(value));
         } else if (android::base::EndsWith(name, ".paths") ||
                    android::base::EndsWith(name, ".shared_libs") ||
                    android::base::EndsWith(name, ".whitelisted") ||
                    android::base::EndsWith(name, ".allowed_libs")) {
           value = ":" + value;
           (*properties)[name].append_value(std::move(value));
         } else {
           DL_WARN("%s:%zd: warning: += isn't allowed for property \"%s\" (ignoring)",
                   ld_config_file_path,
                   cp.lineno(),
                   name.c_str());
         }
       }
     }

     if (result == ConfigParser::kError) {
       DL_WARN("%s:%zd: warning: couldn't parse %s (ignoring this line)",
               ld_config_file_path,
               cp.lineno(),
               error.c_str());
       continue;
     }
   }

   return true;
 }

 static Config g_config;

 static constexpr const char* kDefaultConfigName = "default";
 static constexpr const char* kPropertyAdditionalNamespaces = "additional.namespaces";

 class Properties {
  public:
   explicit Properties(std::unordered_map<std::string, PropertyValue>&& properties)
       : properties_(std::move(properties)), target_sdk_version_(__ANDROID_API__) {}

   std::vector<std::string> get_strings(const std::string& name, size_t* lineno = nullptr) const {
     auto it = find_property(name, lineno);
     if (it == properties_.end()) {
       // return empty vector
       return std::vector<std::string>();
     }

     std::vector<std::string> strings = android::base::Split(it->second.value(), ",");

     for (size_t i = 0; i < strings.size(); ++i) {
       strings[i] = android::base::Trim(strings[i]);
     }

     return strings;
   }

   bool get_bool(const std::string& name, size_t* lineno = nullptr) const {
     auto it = find_property(name, lineno);
     if (it == properties_.end()) {
       return false;
     }

     return it->second.value() == "true";
   }

   std::string get_string(const std::string& name, size_t* lineno = nullptr) const {
     auto it = find_property(name, lineno);
     return (it == properties_.end()) ? "" : it->second.value();
   }

   std::vector<std::string> get_paths(const std::string& name, bool resolve, size_t* lineno = nullptr) {
     std::string paths_str = get_string(name, lineno);

     std::vector<std::string> paths;
     split_path(paths_str.c_str(), ":", &paths);

     std::vector<std::pair<std::string, std::string>> params;
     params.push_back({ "LIB", kLibPath });
     if (target_sdk_version_ != 0) {
       char buf[16];
       async_safe_format_buffer(buf, sizeof(buf), "%d", target_sdk_version_);
       params.push_back({ "SDK_VER", buf });
     }

     static std::string vndk_ver = Config::get_vndk_version_string('-');
     params.push_back({ "VNDK_VER", vndk_ver });
     static std::string vndk_apex_ver = Config::get_vndk_version_string('v');
     params.push_back({ "VNDK_APEX_VER", vndk_apex_ver });

     for (auto& path : paths) {
       format_string(&path, params);
     }

     if (resolve) {
       std::vector<std::string> resolved_paths;
       for (const auto& path : paths) {
         if (path.empty()) {
           continue;
         }
         // this is single threaded. no need to lock
         auto cached = resolved_paths_.find(path);
         if (cached == resolved_paths_.end()) {
           resolved_paths_[path] = resolve_path(path);
           cached = resolved_paths_.find(path);
         }
         CHECK(cached != resolved_paths_.end());
         if (cached->second.empty()) {
           continue;
         }
         resolved_paths.push_back(cached->second);
       }

       return resolved_paths;
     } else {
       return paths;
     }
   }

   void set_target_sdk_version(int target_sdk_version) {
     target_sdk_version_ = target_sdk_version;
   }

  private:
   std::unordered_map<std::string, PropertyValue>::const_iterator
   find_property(const std::string& name, size_t* lineno) const {
     auto it = properties_.find(name);
     if (it != properties_.end() && lineno != nullptr) {
       *lineno = it->second.lineno();
     }

     return it;
   }
   std::unordered_map<std::string, PropertyValue> properties_;
   std::unordered_map<std::string, std::string> resolved_paths_;
   int target_sdk_version_;

   DISALLOW_IMPLICIT_CONSTRUCTORS(Properties);
 };

 bool Config::read_binary_config(const char* ld_config_file_path,
                                       const char* binary_realpath,
                                       bool is_asan,
                                       const Config** config,
                                       std::string* error_msg) {
   g_config.clear();

   std::unordered_map<std::string, PropertyValue> property_map;
   if (!parse_config_file(ld_config_file_path, binary_realpath, &property_map, error_msg)) {
     return false;
   }

   Properties properties(std::move(property_map));

   auto failure_guard = android::base::make_scope_guard([] { g_config.clear(); });

   std::unordered_map<std::string, NamespaceConfig*> namespace_configs;

   namespace_configs[kDefaultConfigName] = g_config.create_namespace_config(kDefaultConfigName);

   std::vector<std::string> additional_namespaces = properties.get_strings(kPropertyAdditionalNamespaces);
   for (const auto& name : additional_namespaces) {
     namespace_configs[name] = g_config.create_namespace_config(name);
   }

   bool versioning_enabled = properties.get_bool("enable.target.sdk.version");
   int target_sdk_version = __ANDROID_API__;
   if (versioning_enabled) {
     std::string version_file = dirname(binary_realpath) + "/.version";
     std::string content;
     if (!android::base::ReadFileToString(version_file, &content)) {
       if (errno != ENOENT) {
         *error_msg = std::string("error reading version file \"") +
                      version_file + "\": " + strerror(errno);
         return false;
       }
     } else {
       content = android::base::Trim(content);
       errno = 0;
       char* end = nullptr;
       const char* content_str = content.c_str();
       int result = strtol(content_str, &end, 10);
       if (errno == 0 && *end == '\0' && result > 0) {
         target_sdk_version = result;
         properties.set_target_sdk_version(target_sdk_version);
       } else {
         *error_msg = std::string("invalid version \"") + version_file + "\": \"" + content +"\"";
         return false;
       }
     }
   }

   g_config.set_target_sdk_version(target_sdk_version);

   for (const auto& ns_config_it : namespace_configs) {
     auto& name = ns_config_it.first;
     NamespaceConfig* ns_config = ns_config_it.second;

     std::string property_name_prefix = std::string("namespace.") + name;

     size_t lineno = 0;
     std::vector<std::string> linked_namespaces =
         properties.get_strings(property_name_prefix + ".links", &lineno);

     for (const auto& linked_ns_name : linked_namespaces) {
       if (namespace_configs.find(linked_ns_name) == namespace_configs.end()) {
         *error_msg = create_error_msg(ld_config_file_path,
                                       lineno,
                                       std::string("undefined namespace: ") + linked_ns_name);
         return false;
       }

       bool allow_all_shared_libs = properties.get_bool(property_name_prefix + ".link." +
                                                        linked_ns_name + ".allow_all_shared_libs");

       std::string shared_libs = properties.get_string(property_name_prefix +
                                                       ".link." +
                                                       linked_ns_name +
                                                       ".shared_libs", &lineno);

       if (!allow_all_shared_libs && shared_libs.empty()) {
         *error_msg = create_error_msg(ld_config_file_path,
                                       lineno,
                                       std::string("list of shared_libs for ") +
                                       name +
                                       "->" +
                                       linked_ns_name +
                                       " link is not specified or is empty.");
         return false;
       }

       if (allow_all_shared_libs && !shared_libs.empty()) {
         *error_msg = create_error_msg(ld_config_file_path, lineno,
                                       std::string("both shared_libs and allow_all_shared_libs "
                                                   "are set for ") +
                                       name + "->" + linked_ns_name + " link.");
         return false;
       }

       ns_config->add_namespace_link(linked_ns_name, shared_libs, allow_all_shared_libs);
     }

     ns_config->set_isolated(properties.get_bool(property_name_prefix + ".isolated"));
     ns_config->set_visible(properties.get_bool(property_name_prefix + ".visible"));

     std::string allowed_libs =
         properties.get_string(property_name_prefix + ".whitelisted", &lineno);
     const std::string libs = properties.get_string(property_name_prefix + ".allowed_libs", &lineno);
     if (!allowed_libs.empty() && !libs.empty()) {
       allowed_libs += ":";
     }
     allowed_libs += libs;
     if (!allowed_libs.empty()) {
       ns_config->set_allowed_libs(android::base::Split(allowed_libs, ":"));
     }

     // these are affected by is_asan flag
     if (is_asan) {
       property_name_prefix += ".asan";
     }

     // search paths are resolved (canonicalized). This is required mainly for
     // the case when /vendor is a symlink to /system/vendor, which is true for
     // non Treble-ized legacy devices.
     ns_config->set_search_paths(properties.get_paths(property_name_prefix + ".search.paths", true));

     // However, for permitted paths, we are not required to resolve the paths
     // since they are only set for isolated namespaces, which implies the device
     // is Treble-ized (= /vendor is not a symlink to /system/vendor).
     // In fact, the resolving is causing an unexpected side effect of selinux
     // denials on some executables which are not allowed to access some of the
     // permitted paths.
     ns_config->set_permitted_paths(properties.get_paths(property_name_prefix + ".permitted.paths", false));
   }

   failure_guard.Disable();
   *config = &g_config;
   return true;
 }

 std::string Config::get_vndk_version_string(const char delimiter) {
   std::string version = android::base::GetProperty("ro.vndk.version", "");
   if (version != "" && version != "current") {
     //add the delimiter char in front of the string and return it.
     return version.insert(0, 1, delimiter);
   }
   return "";
 }

 NamespaceConfig* Config::create_namespace_config(const std::string& name) {
   namespace_configs_.push_back(std::unique_ptr<NamespaceConfig>(new NamespaceConfig(name)));
   NamespaceConfig* ns_config_ptr = namespace_configs_.back().get();
   namespace_configs_map_[name] = ns_config_ptr;
   return ns_config_ptr;
 }

 void Config::clear() {
   namespace_configs_.clear();
   namespace_configs_map_.clear();
 }
	/*
	* 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 "linker_config.h"

	#include "linker_globals.h"
	#include "linker_debug.h"
	#include "linker_utils.h"

	#include <android-base/file.h>
	#include <android-base/properties.h>
	#include <android-base/scopeguard.h>
	#include <android-base/strings.h>

	#include <async_safe/log.h>

	#include <limits.h>
	#include <stdlib.h>
	#include <unistd.h>

	#include <string>
	#include <unordered_map>

	#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
	#include <sys/_system_properties.h>

	class ConfigParser {
	public:
	enum {
	kPropertyAssign,
	kPropertyAppend,
	kSection,
	kEndOfFile,
	kError,
	};

	explicit ConfigParser(std::string&& content)
	: content_(std::move(content)), p_(0), lineno_(0), was_end_of_file_(false) {}

	/*
	* Possible return values
	* kPropertyAssign: name is set to property name and value is set to property value
	* kPropertyAppend: same as kPropertyAssign, but the value should be appended
	* kSection: name is set to section name.
	* kEndOfFile: reached end of file.
	* kError: error_msg is set.
	*/
	int next_token(std::string* name, std::string* value, std::string* error_msg) {
	std::string line;
	while(NextLine(&line)) {
	size_t found = line.find('#');
	line = android::base::Trim(line.substr(0, found));

	if (line.empty()) {
	continue;
	}

	if (line[0] == '[' && line.back() == ']') {
	*name = line.substr(1, line.size() - 2);
	return kSection;
	}

	size_t found_assign = line.find('=');
	size_t found_append = line.find("+=");
	if (found_assign != std::string::npos && found_append == std::string::npos) {
	*name = android::base::Trim(line.substr(0, found_assign));
	*value = android::base::Trim(line.substr(found_assign + 1));
	return kPropertyAssign;
	}

	if (found_append != std::string::npos) {
	*name = android::base::Trim(line.substr(0, found_append));
	*value = android::base::Trim(line.substr(found_append + 2));
	return kPropertyAppend;
	}

	*error_msg = std::string("invalid format: ") +
	line +
	", expected \"name = property\", \"name += property\", or \"[section]\"";
	return kError;
	}

	// to avoid infinite cycles when programmer makes a mistake
	CHECK(!was_end_of_file_);
	was_end_of_file_ = true;
	return kEndOfFile;
	}

	size_t lineno() const {
	return lineno_;
	}

	private:
	bool NextLine(std::string* line) {
	if (p_ == std::string::npos) {
	return false;
	}

	size_t found = content_.find('\n', p_);
	if (found != std::string::npos) {
	*line = content_.substr(p_, found - p_);
	p_ = found + 1;
	} else {
	*line = content_.substr(p_);
	p_ = std::string::npos;
	}

	lineno_++;
	return true;
	}

	std::string content_;
	size_t p_;
	size_t lineno_;
	bool was_end_of_file_;

	DISALLOW_IMPLICIT_CONSTRUCTORS(ConfigParser);
	};

	class PropertyValue {
	public:
	PropertyValue() = default;

	PropertyValue(std::string&& value, size_t lineno)
	: value_(std::move(value)), lineno_(lineno) {}

	const std::string& value() const {
	return value_;
	}

	void append_value(std::string&& value) {
	value_ = value_ + value;
	// lineno isn't updated as we might have cases like this:
	// property.x = blah
	// property.y = blah
	// property.x += blah
	}

	size_t lineno() const {
	return lineno_;
	}

	private:
	std::string value_;
	size_t lineno_;
	};

	static std::string create_error_msg(const char* file,
	size_t lineno,
	const std::string& msg) {
	char buf[1024];
	async_safe_format_buffer(buf, sizeof(buf), "%s:%zu: error: %s", file, lineno, msg.c_str());

	return std::string(buf);
	}

	static bool parse_config_file(const char* ld_config_file_path,
	const char* binary_realpath,
	std::unordered_map<std::string, PropertyValue>* properties,
	std::string* error_msg) {
	std::string content;
	if (!android::base::ReadFileToString(ld_config_file_path, &content)) {
	if (errno != ENOENT) {
	*error_msg = std::string("error reading file \"") +
	ld_config_file_path + "\": " + strerror(errno);
	}
	return false;
	}

	ConfigParser cp(std::move(content));

	std::string section_name;

	while (true) {
	std::string name;
	std::string value;
	std::string error;

	int result = cp.next_token(&name, &value, &error);
	if (result == ConfigParser::kError) {
	DL_WARN("%s:%zd: warning: couldn't parse %s (ignoring this line)",
	ld_config_file_path,
	cp.lineno(),
	error.c_str());
	continue;
	}

	if (result == ConfigParser::kSection \|\| result == ConfigParser::kEndOfFile) {
	return false;
	}

	if (result == ConfigParser::kPropertyAssign) {
	if (!android::base::StartsWith(name, "dir.")) {
	DL_WARN("%s:%zd: warning: unexpected property name \"%s\", "
	"expected format dir.<section_name> (ignoring this line)",
	ld_config_file_path,
	cp.lineno(),
	name.c_str());
	continue;
	}

	// remove trailing '/'
	while (!value.empty() && value.back() == '/') {
	value.pop_back();
	}

	if (value.empty()) {
	DL_WARN("%s:%zd: warning: property value is empty (ignoring this line)",
	ld_config_file_path,
	cp.lineno());
	continue;
	}

	// If the path can be resolved, resolve it
	char buf[PATH_MAX];
	std::string resolved_path;
	if (access(value.c_str(), R_OK) != 0) {
	if (errno == ENOENT) {
	// no need to test for non-existing path. skip.
	continue;
	}
	// If not accessible, don't call realpath as it will just cause
	// SELinux denial spam. Use the path unresolved.
	resolved_path = value;
	} else if (realpath(value.c_str(), buf)) {
	resolved_path = buf;
	} else {
	// realpath is expected to fail with EPERM in some situations, so log
	// the failure with INFO rather than DL_WARN. e.g. A binary in
	// /data/local/tmp may attempt to stat /postinstall. See
	// http://b/120996057.
	INFO("%s:%zd: warning: path \"%s\" couldn't be resolved: %s",
	ld_config_file_path,
	cp.lineno(),
	value.c_str(),
	strerror(errno));
	resolved_path = value;
	}

	if (file_is_under_dir(binary_realpath, resolved_path)) {
	section_name = name.substr(4);
	break;
	}
	}
	}

	INFO("[ Using config section \"%s\" ]", section_name.c_str());

	// skip everything until we meet a correct section
	while (true) {
	std::string name;
	std::string value;
	std::string error;

	int result = cp.next_token(&name, &value, &error);

	if (result == ConfigParser::kSection && name == section_name) {
	break;
	}

	if (result == ConfigParser::kEndOfFile) {
	*error_msg = create_error_msg(ld_config_file_path,
	cp.lineno(),
	std::string("section \"") + section_name + "\" not found");
	return false;
	}
	}

	// found the section - parse it
	while (true) {
	std::string name;
	std::string value;
	std::string error;

	int result = cp.next_token(&name, &value, &error);

	if (result == ConfigParser::kEndOfFile \|\| result == ConfigParser::kSection) {
	break;
	}

	if (result == ConfigParser::kPropertyAssign) {
	if (properties->find(name) != properties->end()) {
	DL_WARN("%s:%zd: warning: redefining property \"%s\" (overriding previous value)",
	ld_config_file_path,
	cp.lineno(),
	name.c_str());
	}

	(*properties)[name] = PropertyValue(std::move(value), cp.lineno());
	} else if (result == ConfigParser::kPropertyAppend) {
	if (properties->find(name) == properties->end()) {
	DL_WARN("%s:%zd: warning: appending to undefined property \"%s\" (treating as assignment)",
	ld_config_file_path,
	cp.lineno(),
	name.c_str());
	(*properties)[name] = PropertyValue(std::move(value), cp.lineno());
	} else {
	if (android::base::EndsWith(name, ".links") \|\|
	android::base::EndsWith(name, ".namespaces")) {
	value = "," + value;
	(*properties)[name].append_value(std::move(value));
	} else if (android::base::EndsWith(name, ".paths") \|\|
	android::base::EndsWith(name, ".shared_libs") \|\|
	android::base::EndsWith(name, ".whitelisted") \|\|
	android::base::EndsWith(name, ".allowed_libs")) {
	value = ":" + value;
	(*properties)[name].append_value(std::move(value));
	} else {
	DL_WARN("%s:%zd: warning: += isn't allowed for property \"%s\" (ignoring)",
	ld_config_file_path,
	cp.lineno(),
	name.c_str());
	}
	}
	}

	if (result == ConfigParser::kError) {
	DL_WARN("%s:%zd: warning: couldn't parse %s (ignoring this line)",
	ld_config_file_path,
	cp.lineno(),
	error.c_str());
	continue;
	}
	}

	return true;
	}

	static Config g_config;

	static constexpr const char* kDefaultConfigName = "default";
	static constexpr const char* kPropertyAdditionalNamespaces = "additional.namespaces";

	class Properties {
	public:
	explicit Properties(std::unordered_map<std::string, PropertyValue>&& properties)
	: properties_(std::move(properties)), target_sdk_version_(__ANDROID_API__) {}

	std::vector<std::string> get_strings(const std::string& name, size_t* lineno = nullptr) const {
	auto it = find_property(name, lineno);
	if (it == properties_.end()) {
	// return empty vector
	return std::vector<std::string>();
	}

	std::vector<std::string> strings = android::base::Split(it->second.value(), ",");

	for (size_t i = 0; i < strings.size(); ++i) {
	strings[i] = android::base::Trim(strings[i]);
	}

	return strings;
	}

	bool get_bool(const std::string& name, size_t* lineno = nullptr) const {
	auto it = find_property(name, lineno);
	if (it == properties_.end()) {
	return false;
	}

	return it->second.value() == "true";
	}

	std::string get_string(const std::string& name, size_t* lineno = nullptr) const {
	auto it = find_property(name, lineno);
	return (it == properties_.end()) ? "" : it->second.value();
	}

	std::vector<std::string> get_paths(const std::string& name, bool resolve, size_t* lineno = nullptr) {
	std::string paths_str = get_string(name, lineno);

	std::vector<std::string> paths;
	split_path(paths_str.c_str(), ":", &paths);

	std::vector<std::pair<std::string, std::string>> params;
	params.push_back({ "LIB", kLibPath });
	if (target_sdk_version_ != 0) {
	char buf[16];
	async_safe_format_buffer(buf, sizeof(buf), "%d", target_sdk_version_);
	params.push_back({ "SDK_VER", buf });
	}

	static std::string vndk_ver = Config::get_vndk_version_string('-');
	params.push_back({ "VNDK_VER", vndk_ver });
	static std::string vndk_apex_ver = Config::get_vndk_version_string('v');
	params.push_back({ "VNDK_APEX_VER", vndk_apex_ver });

	for (auto& path : paths) {
	format_string(&path, params);
	}

	if (resolve) {
	std::vector<std::string> resolved_paths;
	for (const auto& path : paths) {
	if (path.empty()) {
	continue;
	}
	// this is single threaded. no need to lock
	auto cached = resolved_paths_.find(path);
	if (cached == resolved_paths_.end()) {
	resolved_paths_[path] = resolve_path(path);
	cached = resolved_paths_.find(path);
	}
	CHECK(cached != resolved_paths_.end());
	if (cached->second.empty()) {
	continue;
	}
	resolved_paths.push_back(cached->second);
	}

	return resolved_paths;
	} else {
	return paths;
	}
	}

	void set_target_sdk_version(int target_sdk_version) {
	target_sdk_version_ = target_sdk_version;
	}

	private:
	std::unordered_map<std::string, PropertyValue>::const_iterator
	find_property(const std::string& name, size_t* lineno) const {
	auto it = properties_.find(name);
	if (it != properties_.end() && lineno != nullptr) {
	*lineno = it->second.lineno();
	}

	return it;
	}
	std::unordered_map<std::string, PropertyValue> properties_;
	std::unordered_map<std::string, std::string> resolved_paths_;
	int target_sdk_version_;

	DISALLOW_IMPLICIT_CONSTRUCTORS(Properties);
	};

	bool Config::read_binary_config(const char* ld_config_file_path,
	const char* binary_realpath,
	bool is_asan,
	const Config** config,
	std::string* error_msg) {
	g_config.clear();

	std::unordered_map<std::string, PropertyValue> property_map;
	if (!parse_config_file(ld_config_file_path, binary_realpath, &property_map, error_msg)) {
	return false;
	}

	Properties properties(std::move(property_map));

	auto failure_guard = android::base::make_scope_guard([] { g_config.clear(); });

	std::unordered_map<std::string, NamespaceConfig*> namespace_configs;

	namespace_configs[kDefaultConfigName] = g_config.create_namespace_config(kDefaultConfigName);

	std::vector<std::string> additional_namespaces = properties.get_strings(kPropertyAdditionalNamespaces);
	for (const auto& name : additional_namespaces) {
	namespace_configs[name] = g_config.create_namespace_config(name);
	}

	bool versioning_enabled = properties.get_bool("enable.target.sdk.version");
	int target_sdk_version = __ANDROID_API__;
	if (versioning_enabled) {
	std::string version_file = dirname(binary_realpath) + "/.version";
	std::string content;
	if (!android::base::ReadFileToString(version_file, &content)) {
	if (errno != ENOENT) {
	*error_msg = std::string("error reading version file \"") +
	version_file + "\": " + strerror(errno);
	return false;
	}
	} else {
	content = android::base::Trim(content);
	errno = 0;
	char* end = nullptr;
	const char* content_str = content.c_str();
	int result = strtol(content_str, &end, 10);
	if (errno == 0 && *end == '\0' && result > 0) {
	target_sdk_version = result;
	properties.set_target_sdk_version(target_sdk_version);
	} else {
	*error_msg = std::string("invalid version \"") + version_file + "\": \"" + content +"\"";
	return false;
	}
	}
	}

	g_config.set_target_sdk_version(target_sdk_version);

	for (const auto& ns_config_it : namespace_configs) {
	auto& name = ns_config_it.first;
	NamespaceConfig* ns_config = ns_config_it.second;

	std::string property_name_prefix = std::string("namespace.") + name;

	size_t lineno = 0;
	std::vector<std::string> linked_namespaces =
	properties.get_strings(property_name_prefix + ".links", &lineno);

	for (const auto& linked_ns_name : linked_namespaces) {
	if (namespace_configs.find(linked_ns_name) == namespace_configs.end()) {
	*error_msg = create_error_msg(ld_config_file_path,
	lineno,
	std::string("undefined namespace: ") + linked_ns_name);
	return false;
	}

	bool allow_all_shared_libs = properties.get_bool(property_name_prefix + ".link." +
	linked_ns_name + ".allow_all_shared_libs");

	std::string shared_libs = properties.get_string(property_name_prefix +
	".link." +
	linked_ns_name +
	".shared_libs", &lineno);

	if (!allow_all_shared_libs && shared_libs.empty()) {
	*error_msg = create_error_msg(ld_config_file_path,
	lineno,
	std::string("list of shared_libs for ") +
	name +
	"->" +
	linked_ns_name +
	" link is not specified or is empty.");
	return false;
	}

	if (allow_all_shared_libs && !shared_libs.empty()) {
	*error_msg = create_error_msg(ld_config_file_path, lineno,
	std::string("both shared_libs and allow_all_shared_libs "
	"are set for ") +
	name + "->" + linked_ns_name + " link.");
	return false;
	}

	ns_config->add_namespace_link(linked_ns_name, shared_libs, allow_all_shared_libs);
	}

	ns_config->set_isolated(properties.get_bool(property_name_prefix + ".isolated"));
	ns_config->set_visible(properties.get_bool(property_name_prefix + ".visible"));

	std::string allowed_libs =
	properties.get_string(property_name_prefix + ".whitelisted", &lineno);
	const std::string libs = properties.get_string(property_name_prefix + ".allowed_libs", &lineno);
	if (!allowed_libs.empty() && !libs.empty()) {
	allowed_libs += ":";
	}
	allowed_libs += libs;
	if (!allowed_libs.empty()) {
	ns_config->set_allowed_libs(android::base::Split(allowed_libs, ":"));
	}

	// these are affected by is_asan flag
	if (is_asan) {
	property_name_prefix += ".asan";
	}

	// search paths are resolved (canonicalized). This is required mainly for
	// the case when /vendor is a symlink to /system/vendor, which is true for
	// non Treble-ized legacy devices.
	ns_config->set_search_paths(properties.get_paths(property_name_prefix + ".search.paths", true));

	// However, for permitted paths, we are not required to resolve the paths
	// since they are only set for isolated namespaces, which implies the device
	// is Treble-ized (= /vendor is not a symlink to /system/vendor).
	// In fact, the resolving is causing an unexpected side effect of selinux
	// denials on some executables which are not allowed to access some of the
	// permitted paths.
	ns_config->set_permitted_paths(properties.get_paths(property_name_prefix + ".permitted.paths", false));
	}

	failure_guard.Disable();
	*config = &g_config;
	return true;
	}

	std::string Config::get_vndk_version_string(const char delimiter) {
	std::string version = android::base::GetProperty("ro.vndk.version", "");
	if (version != "" && version != "current") {
	//add the delimiter char in front of the string and return it.
	return version.insert(0, 1, delimiter);
	}
	return "";
	}

	NamespaceConfig* Config::create_namespace_config(const std::string& name) {
	namespace_configs_.push_back(std::unique_ptr<NamespaceConfig>(new NamespaceConfig(name)));
	NamespaceConfig* ns_config_ptr = namespace_configs_.back().get();
	namespace_configs_map_[name] = ns_config_ptr;
	return ns_config_ptr;
	}

	void Config::clear() {
	namespace_configs_.clear();
	namespace_configs_map_.clear();
	}