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 22static uintptr_t g_flag = 0; 23 24static void __attribute__((constructor)) init_flag() { 25 g_flag = reinterpret_cast<uintptr_t>(dlsym(RTLD_DEFAULT, "dlsym")); 26} 27 28static const char* is_ctor_called() __attribute__ ((ifunc("is_ctor_called_ifun"))); 29 30extern "C" const char* foo() __attribute__ ((ifunc ("foo_ifunc"))); 31 32// Static linker creates GLOBAL/IFUNC symbol and JUMP_SLOT relocation type for plt segment 33extern "C" const char* is_ctor_called_jump_slot() __attribute__ ((ifunc("is_ctor_called_ifun"))); 34 35extern "C" const char* is_ctor_called_irelative() { 36 // Call internal ifunc-resolved function with IRELATIVE reloc 37 return is_ctor_called(); 38} 39 40extern "C" const char* var_true = "true"; 41extern "C" const char* var_false = "false"; 42 43extern "C" const char* v1 = "unset"; 44extern "C" const char* v2 = "set"; 45 46extern "C" void* is_ctor_called_ifun() { 47 return g_flag == 0 ? &var_false : &var_true; 48} 49 50extern "C" void* foo_ifunc() { 51 char* choice = getenv("IFUNC_CHOICE"); 52 return choice == NULL ? &v1 : &v2; 53} 54