1 //===-- Intercept.cpp - System function interception routines -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
16 //===----------------------------------------------------------------------===//
19 #include "llvm/Support/Streams.h"
20 #include "llvm/System/DynamicLibrary.h"
21 #include "llvm/Config/config.h"
24 // AtExitHandlers - List of functions to call when the program exits,
25 // registered with the atexit() library function.
26 static std::vector<void (*)()> AtExitHandlers;
28 /// runAtExitHandlers - Run any functions registered by the program's
29 /// calls to atexit(3), which we intercept and store in
32 static void runAtExitHandlers() {
33 while (!AtExitHandlers.empty()) {
34 void (*Fn)() = AtExitHandlers.back();
35 AtExitHandlers.pop_back();
40 //===----------------------------------------------------------------------===//
41 // Function stubs that are invoked instead of certain library calls
42 //===----------------------------------------------------------------------===//
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)
55 /* stat functions are redirecting to __xstat with a version number. On x86-64
56 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
57 * available as an exported symbol, so we have to add it explicitly.
62 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
63 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
64 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
65 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
66 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
67 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
68 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
69 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
70 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
71 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
72 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
75 static StatSymbols initStatSymbols;
78 // jit_exit - Used to intercept the "exit" library call.
79 static void jit_exit(int Status) {
80 runAtExitHandlers(); // Run atexit handlers...
84 // jit_atexit - Used to intercept the "atexit" library call.
85 static int jit_atexit(void (*Fn)(void)) {
86 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
87 return 0; // Always successful
90 //===----------------------------------------------------------------------===//
92 /// getPointerToNamedFunction - This method returns the address of the specified
93 /// function by using the dynamic loader interface. As such it is only useful
94 /// for resolving library symbols, not code generated symbols.
96 void *JIT::getPointerToNamedFunction(const std::string &Name,
97 bool AbortOnFailure) {
98 if (!isSymbolSearchingDisabled()) {
99 // Check to see if this is one of the functions we want to intercept. Note,
100 // we cast to intptr_t here to silence a -pedantic warning that complains
101 // about casting a function pointer to a normal pointer.
102 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
103 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
105 const char *NameStr = Name.c_str();
106 // If this is an asm specifier, skip the sentinal.
107 if (NameStr[0] == 1) ++NameStr;
109 // If it's an external function, look it up in the process image...
110 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
113 // If it wasn't found and if it starts with an underscore ('_') character,
114 // and has an asm specifier, try again without the underscore.
115 if (Name[0] == 1 && NameStr[0] == '_') {
116 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
120 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
121 // are references to hidden visibility symbols that dlsym cannot resolve.
122 // If we have one of these, strip off $LDBLStub and try again.
123 #if defined(__APPLE__) && defined(__ppc__)
124 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
125 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
126 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
127 // This mirrors logic in libSystemStubs.a.
128 std::string Prefix = std::string(Name.begin(), Name.end()-9);
129 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
131 if (void *Ptr = getPointerToNamedFunction(Prefix, false))
137 /// If a LazyFunctionCreator is installed, use it to get/create the function.
138 if (LazyFunctionCreator)
139 if (void *RP = LazyFunctionCreator(Name))
142 if (AbortOnFailure) {
143 cerr << "ERROR: Program used external function '" << Name
144 << "' which could not be resolved!\n";