1 // Copyright 2015 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // This is the Android-specific Chromium linker, a tiny shared library 6 // implementing a custom dynamic linker that can be used to load the 7 // real Chromium libraries. 8 9 // The main point of this linker is to be able to share the RELRO 10 // section of libcontentshell.so (or equivalent) between the browser and 11 // renderer process. 12 13 // This source code *cannot* depend on anything from base/ or the C++ 14 // STL, to keep the final library small, and avoid ugly dependency issues. 15 16 #ifndef BASE_ANDROID_LINKER_LINKER_JNI_H_ 17 #define BASE_ANDROID_LINKER_LINKER_JNI_H_ 18 19 #include <android/log.h> 20 #include <jni.h> 21 #include <stddef.h> 22 #include <stdlib.h> 23 24 // Set this to 1 to enable debug traces to the Android log. 25 // Note that LOG() from "base/logging.h" cannot be used, since it is 26 // in base/ which hasn't been loaded yet. 27 #define DEBUG 0 28 29 #define TAG "cr_ChromiumAndroidLinker" 30 31 #if DEBUG 32 #define LOG_INFO(FORMAT, ...) \ 33 __android_log_print(ANDROID_LOG_INFO, TAG, \ 34 "%s: " FORMAT, __FUNCTION__, ##__VA_ARGS__) 35 #else 36 #define LOG_INFO(FORMAT, ...) ((void)0) 37 #endif 38 #define LOG_ERROR(FORMAT, ...) \ 39 __android_log_print(ANDROID_LOG_ERROR, TAG, \ 40 "%s: " FORMAT, __FUNCTION__, ##__VA_ARGS__) 41 42 #define UNUSED __attribute__((unused)) 43 44 // See commentary in crazy_linker_elf_loader.cpp for the effect of setting 45 // this. If changing there, change here also. 46 // 47 // For more, see: 48 // https://crbug.com/504410 49 #define RESERVE_BREAKPAD_GUARD_REGION 1 50 51 namespace chromium_android_linker { 52 53 // Larger than the largest library we might attempt to load. 54 static const size_t kAddressSpaceReservationSize = 192 * 1024 * 1024; 55 56 // Size of any Breakpad guard region. 16MB is comfortably larger than the 57 // ~6MB relocation packing of the current 64-bit libchrome.so, the largest we 58 // expect to encounter. 59 #if RESERVE_BREAKPAD_GUARD_REGION 60 static const size_t kBreakpadGuardRegionBytes = 16 * 1024 * 1024; 61 #endif 62 63 // A simple scoped UTF String class that can be initialized from 64 // a Java jstring handle. Modeled like std::string, which cannot 65 // be used here. 66 class String { 67 public: 68 String(JNIEnv* env, jstring str); 69 70 inline ~String() { ::free(ptr_); } 71 72 inline const char* c_str() const { return ptr_ ? ptr_ : ""; } 73 inline size_t size() const { return size_; } 74 75 private: 76 char* ptr_; 77 size_t size_; 78 }; 79 80 // Return true iff |address| is a valid address for the target CPU. 81 inline bool IsValidAddress(jlong address) { 82 return static_cast<jlong>(static_cast<size_t>(address)) == address; 83 } 84 85 // Find the jclass JNI reference corresponding to a given |class_name|. 86 // |env| is the current JNI environment handle. 87 // On success, return true and set |*clazz|. 88 extern bool InitClassReference(JNIEnv* env, 89 const char* class_name, 90 jclass* clazz); 91 92 // Initialize a jfieldID corresponding to the field of a given |clazz|, 93 // with name |field_name| and signature |field_sig|. 94 // |env| is the current JNI environment handle. 95 // On success, return true and set |*field_id|. 96 extern bool InitFieldId(JNIEnv* env, 97 jclass clazz, 98 const char* field_name, 99 const char* field_sig, 100 jfieldID* field_id); 101 102 // Initialize a jmethodID corresponding to the static method of a given 103 // |clazz|, with name |method_name| and signature |method_sig|. 104 // |env| is the current JNI environment handle. 105 // On success, return true and set |*method_id|. 106 extern bool InitStaticMethodId(JNIEnv* env, 107 jclass clazz, 108 const char* method_name, 109 const char* method_sig, 110 jmethodID* method_id); 111 112 // Initialize a jfieldID corresponding to the static field of a given |clazz|, 113 // with name |field_name| and signature |field_sig|. 114 // |env| is the current JNI environment handle. 115 // On success, return true and set |*field_id|. 116 extern bool InitStaticFieldId(JNIEnv* env, 117 jclass clazz, 118 const char* field_name, 119 const char* field_sig, 120 jfieldID* field_id); 121 122 // Initialize a jint corresponding to the static integer field of a class 123 // with class name |class_name| and field name |field_name|. 124 // |env| is the current JNI environment handle. 125 // On success, return true and set |*value|. 126 extern bool InitStaticInt(JNIEnv* env, 127 const char* class_name, 128 const char* field_name, 129 jint* value); 130 131 // Use Android ASLR to create a random library load address. 132 // |env| is the current JNI environment handle, and |clazz| a class. 133 // Returns the address selected by ASLR. 134 extern jlong GetRandomBaseLoadAddress(JNIEnv* env, jclass clazz); 135 136 // A class used to model the field IDs of the org.chromium.base.Linker 137 // LibInfo inner class, used to communicate data with the Java side 138 // of the linker. 139 struct LibInfo_class { 140 jfieldID load_address_id; 141 jfieldID load_size_id; 142 jfieldID relro_start_id; 143 jfieldID relro_size_id; 144 jfieldID relro_fd_id; 145 146 // Initialize an instance. 147 bool Init(JNIEnv* env) { 148 jclass clazz; 149 if (!InitClassReference( 150 env, "org/chromium/base/library_loader/Linker$LibInfo", &clazz)) { 151 return false; 152 } 153 154 return InitFieldId(env, clazz, "mLoadAddress", "J", &load_address_id) && 155 InitFieldId(env, clazz, "mLoadSize", "J", &load_size_id) && 156 InitFieldId(env, clazz, "mRelroStart", "J", &relro_start_id) && 157 InitFieldId(env, clazz, "mRelroSize", "J", &relro_size_id) && 158 InitFieldId(env, clazz, "mRelroFd", "I", &relro_fd_id); 159 } 160 161 void SetLoadInfo(JNIEnv* env, 162 jobject library_info_obj, 163 size_t load_address, 164 size_t load_size) { 165 env->SetLongField(library_info_obj, load_address_id, load_address); 166 env->SetLongField(library_info_obj, load_size_id, load_size); 167 } 168 169 void SetRelroInfo(JNIEnv* env, 170 jobject library_info_obj, 171 size_t relro_start, 172 size_t relro_size, 173 int relro_fd) { 174 env->SetLongField(library_info_obj, relro_start_id, relro_start); 175 env->SetLongField(library_info_obj, relro_size_id, relro_size); 176 env->SetIntField(library_info_obj, relro_fd_id, relro_fd); 177 } 178 179 // Use this instance to convert a RelroInfo reference into 180 // a crazy_library_info_t. 181 void GetRelroInfo(JNIEnv* env, 182 jobject library_info_obj, 183 size_t* relro_start, 184 size_t* relro_size, 185 int* relro_fd) { 186 if (relro_start) { 187 *relro_start = static_cast<size_t>( 188 env->GetLongField(library_info_obj, relro_start_id)); 189 } 190 191 if (relro_size) { 192 *relro_size = static_cast<size_t>( 193 env->GetLongField(library_info_obj, relro_size_id)); 194 } 195 196 if (relro_fd) { 197 *relro_fd = env->GetIntField(library_info_obj, relro_fd_id); 198 } 199 } 200 }; 201 202 // Variable containing LibInfo for the loaded library. 203 extern LibInfo_class s_lib_info_fields; 204 205 } // namespace chromium_android_linker 206 207 #endif // BASE_ANDROID_LINKER_LINKER_JNI_H_ 208
