1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <dlfcn.h> 18 #include <stdint.h> 19 #include <stdio.h> 20 #include <stdlib.h> 21 22 static uintptr_t g_flag = 0; 23 24 static void __attribute__((constructor)) init_flag() { 25 g_flag = reinterpret_cast<uintptr_t>(dlsym(RTLD_DEFAULT, "dlsym")); 26 } 27 28 static const char* is_ctor_called() __attribute__ ((ifunc("is_ctor_called_ifun"))); 29 30 extern "C" const char* foo() __attribute__ ((ifunc ("foo_ifunc"))); 31 32 // Static linker creates GLOBAL/IFUNC symbol and JUMP_SLOT relocation type for plt segment 33 extern "C" const char* is_ctor_called_jump_slot() __attribute__ ((ifunc("is_ctor_called_ifun"))); 34 35 extern "C" const char* is_ctor_called_irelative() { 36 // Call internal ifunc-resolved function with IRELATIVE reloc 37 return is_ctor_called(); 38 } 39 40 extern "C" const char* var_true = "true"; 41 extern "C" const char* var_false = "false"; 42 43 extern "C" const char* v1 = "unset"; 44 extern "C" const char* v2 = "set"; 45 46 extern "C" void* is_ctor_called_ifun() { 47 return g_flag == 0 ? &var_false : &var_true; 48 } 49 50 extern "C" void* foo_ifunc() { 51 char* choice = getenv("IFUNC_CHOICE"); 52 return choice == NULL ? &v1 : &v2; 53 } 54
