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/ErrorHandling.h"
20 #include "llvm/Support/Streams.h"
21 #include "llvm/System/DynamicLibrary.h"
22 #include "llvm/Config/config.h"
25 // AtExitHandlers - List of functions to call when the program exits,
26 // registered with the atexit() library function.
27 static std::vector<void (*)()> AtExitHandlers;
29 /// runAtExitHandlers - Run any functions registered by the program's
30 /// calls to atexit(3), which we intercept and store in
33 static void runAtExitHandlers() {
34 while (!AtExitHandlers.empty()) {
35 void (*Fn)() = AtExitHandlers.back();
36 AtExitHandlers.pop_back();
41 //===----------------------------------------------------------------------===//
42 // Function stubs that are invoked instead of certain library calls
43 //===----------------------------------------------------------------------===//
45 // Force the following functions to be linked in to anything that uses the
46 // JIT. This is a hack designed to work around the all-too-clever Glibc
47 // strategy of making these functions work differently when inlined vs. when
48 // not inlined, and hiding their real definitions in a separate archive file
49 // that the dynamic linker can't see. For more info, search for
50 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
51 #if defined(__linux__)
52 #if defined(HAVE_SYS_STAT_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.
63 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
64 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
65 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
66 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
67 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
68 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
69 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
70 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
71 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
72 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
73 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
76 static StatSymbols initStatSymbols;
79 // jit_exit - Used to intercept the "exit" library call.
80 static void jit_exit(int Status) {
81 runAtExitHandlers(); // Run atexit handlers...
85 // jit_atexit - Used to intercept the "atexit" library call.
86 static int jit_atexit(void (*Fn)(void)) {
87 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
88 return 0; // Always successful
91 //===----------------------------------------------------------------------===//
93 /// getPointerToNamedFunction - This method returns the address of the specified
94 /// function by using the dynamic loader interface. As such it is only useful
95 /// for resolving library symbols, not code generated symbols.
97 void *JIT::getPointerToNamedFunction(const std::string &Name,
98 bool AbortOnFailure) {
99 if (!isSymbolSearchingDisabled()) {
100 // Check to see if this is one of the functions we want to intercept. Note,
101 // we cast to intptr_t here to silence a -pedantic warning that complains
102 // about casting a function pointer to a normal pointer.
103 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
104 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
106 const char *NameStr = Name.c_str();
107 // If this is an asm specifier, skip the sentinal.
108 if (NameStr[0] == 1) ++NameStr;
110 // If it's an external function, look it up in the process image...
111 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
114 // If it wasn't found and if it starts with an underscore ('_') character,
115 // and has an asm specifier, try again without the underscore.
116 if (Name[0] == 1 && NameStr[0] == '_') {
117 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
121 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
122 // are references to hidden visibility symbols that dlsym cannot resolve.
123 // If we have one of these, strip off $LDBLStub and try again.
124 #if defined(__APPLE__) && defined(__ppc__)
125 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
126 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
127 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
128 // This mirrors logic in libSystemStubs.a.
129 std::string Prefix = std::string(Name.begin(), Name.end()-9);
130 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
132 if (void *Ptr = getPointerToNamedFunction(Prefix, false))
138 /// If a LazyFunctionCreator is installed, use it to get/create the function.
139 if (LazyFunctionCreator)
140 if (void *RP = LazyFunctionCreator(Name))
143 if (AbortOnFailure) {
144 llvm_report_error("ERROR: Program used external function '"+Name+
145 "' which could not be resolved!");