1 //===-- Intercept.cpp - System function interception routines -------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // If a function call occurs to an external function, the JIT is designed to use 11 // the dynamic loader interface to find a function to call. This is useful for 12 // calling system calls and library functions that are not available in LLVM. 13 // Some system calls, however, need to be handled specially. For this reason, 14 // we intercept some of them here and use our own stubs to handle them. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #include "MCJIT.h" 19 #include "llvm/Support/ErrorHandling.h" 20 #include "llvm/Support/DynamicLibrary.h" 21 #include "llvm/Config/config.h" 22 using namespace llvm; 23 24 // AtExitHandlers - List of functions to call when the program exits, 25 // registered with the atexit() library function. 26 static std::vector<void (*)()> AtExitHandlers; 27 28 /// runAtExitHandlers - Run any functions registered by the program's 29 /// calls to atexit(3), which we intercept and store in 30 /// AtExitHandlers. 31 /// 32 static void runAtExitHandlers() { 33 while (!AtExitHandlers.empty()) { 34 void (*Fn)() = AtExitHandlers.back(); 35 AtExitHandlers.pop_back(); 36 Fn(); 37 } 38 } 39 40 //===----------------------------------------------------------------------===// 41 // Function stubs that are invoked instead of certain library calls 42 //===----------------------------------------------------------------------===// 43 44 // Force the following functions to be linked in to anything that uses the 45 // JIT. This is a hack designed to work around the all-too-clever Glibc 46 // strategy of making these functions work differently when inlined vs. when 47 // not inlined, and hiding their real definitions in a separate archive file 48 // that the dynamic linker can't see. For more info, search for 49 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274. 50 #if defined(__linux__) 51 #if defined(HAVE_SYS_STAT_H) 52 #include <sys/stat.h> 53 #endif 54 #include <fcntl.h> 55 #include <unistd.h> 56 /* stat functions are redirecting to __xstat with a version number. On x86-64 57 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat' 58 * available as an exported symbol, so we have to add it explicitly. 59 */ 60 namespace { 61 class StatSymbols { 62 public: 63 StatSymbols() { 64 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat); 65 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat); 66 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat); 67 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64); 68 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64); 69 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64); 70 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64); 71 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64); 72 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64); 73 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit); 74 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod); 75 } 76 }; 77 } 78 static StatSymbols initStatSymbols; 79 #endif // __linux__ 80 81 // jit_exit - Used to intercept the "exit" library call. 82 static void jit_exit(int Status) { 83 runAtExitHandlers(); // Run atexit handlers... 84 exit(Status); 85 } 86 87 // jit_atexit - Used to intercept the "atexit" library call. 88 static int jit_atexit(void (*Fn)()) { 89 AtExitHandlers.push_back(Fn); // Take note of atexit handler... 90 return 0; // Always successful 91 } 92 93 static int jit_noop() { 94 return 0; 95 } 96 97 //===----------------------------------------------------------------------===// 98 // 99 /// getPointerToNamedFunction - This method returns the address of the specified 100 /// function by using the dynamic loader interface. As such it is only useful 101 /// for resolving library symbols, not code generated symbols. 102 /// 103 void *MCJIT::getPointerToNamedFunction(const std::string &Name, 104 bool AbortOnFailure) { 105 if (!isSymbolSearchingDisabled()) { 106 // Check to see if this is one of the functions we want to intercept. Note, 107 // we cast to intptr_t here to silence a -pedantic warning that complains 108 // about casting a function pointer to a normal pointer. 109 if (Name == "exit") return (void*)(intptr_t)&jit_exit; 110 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit; 111 112 // We should not invoke parent's ctors/dtors from generated main()! 113 // On Mingw and Cygwin, the symbol __main is resolved to 114 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors 115 // (and register wrong callee's dtors with atexit(3)). 116 // We expect ExecutionEngine::runStaticConstructorsDestructors() 117 // is called before ExecutionEngine::runFunctionAsMain() is called. 118 if (Name == "__main") return (void*)(intptr_t)&jit_noop; 119 120 const char *NameStr = Name.c_str(); 121 // If this is an asm specifier, skip the sentinal. 122 if (NameStr[0] == 1) ++NameStr; 123 124 // If it's an external function, look it up in the process image... 125 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr); 126 if (Ptr) return Ptr; 127 128 // If it wasn't found and if it starts with an underscore ('_') character, 129 // and has an asm specifier, try again without the underscore. 130 if (Name[0] == 1 && NameStr[0] == '_') { 131 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1); 132 if (Ptr) return Ptr; 133 } 134 135 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These 136 // are references to hidden visibility symbols that dlsym cannot resolve. 137 // If we have one of these, strip off $LDBLStub and try again. 138 #if defined(__APPLE__) && defined(__ppc__) 139 if (Name.size() > 9 && Name[Name.size()-9] == '$' && 140 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) { 141 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off. 142 // This mirrors logic in libSystemStubs.a. 143 std::string Prefix = std::string(Name.begin(), Name.end()-9); 144 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false)) 145 return Ptr; 146 if (void *Ptr = getPointerToNamedFunction(Prefix, false)) 147 return Ptr; 148 } 149 #endif 150 } 151 152 /// If a LazyFunctionCreator is installed, use it to get/create the function. 153 if (LazyFunctionCreator) 154 if (void *RP = LazyFunctionCreator(Name)) 155 return RP; 156 157 if (AbortOnFailure) { 158 report_fatal_error("Program used external function '"+Name+ 159 "' which could not be resolved!"); 160 } 161 return 0; 162 } 163
