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/System/DynamicLibrary.h"
20 #include "llvm/Config/config.h"
23 // AtExitHandlers - List of functions to call when the program exits,
24 // registered with the atexit() library function.
25 static std::vector<void (*)()> AtExitHandlers;
27 /// runAtExitHandlers - Run any functions registered by the program's
28 /// calls to atexit(3), which we intercept and store in
31 static void runAtExitHandlers() {
32 while (!AtExitHandlers.empty()) {
33 void (*Fn)() = AtExitHandlers.back();
34 AtExitHandlers.pop_back();
39 //===----------------------------------------------------------------------===//
40 // Function stubs that are invoked instead of certain library calls
41 //===----------------------------------------------------------------------===//
43 // Force the following functions to be linked in to anything that uses the
44 // JIT. This is a hack designed to work around the all-too-clever Glibc
45 // strategy of making these functions work differently when inlined vs. when
46 // not inlined, and hiding their real definitions in a separate archive file
47 // that the dynamic linker can't see. For more info, search for
48 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
49 #if defined(__linux__)
50 #if defined(HAVE_SYS_STAT_H)
54 /* stat functions are redirecting to __xstat with a version number.
55 * On x86-64 linking with libc_nonshared.a and -Wl,--export-dynamic
56 * doesn't make 'stat' available as an exported symbol, so we have to add it explicitely.*/
60 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
61 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
62 sys::DynamicLibrary::AddSymbol("fstatat", (void*)(intptr_t)fstatat);
63 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
64 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
65 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
66 sys::DynamicLibrary::AddSymbol("fstatat64", (void*)(intptr_t)fstatat64);
67 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
68 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
69 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
70 sys::DynamicLibrary::AddSymbol("mknodat", (void*)(intptr_t)mknodat);
73 static StatSymbols initStatSymbols;
76 // jit_exit - Used to intercept the "exit" library call.
77 static void jit_exit(int Status) {
78 runAtExitHandlers(); // Run atexit handlers...
82 // jit_atexit - Used to intercept the "atexit" library call.
83 static int jit_atexit(void (*Fn)(void)) {
84 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
85 return 0; // Always successful
88 //===----------------------------------------------------------------------===//
90 /// getPointerToNamedFunction - This method returns the address of the specified
91 /// function by using the dynamic loader interface. As such it is only useful
92 /// for resolving library symbols, not code generated symbols.
94 void *JIT::getPointerToNamedFunction(const std::string &Name) {
95 // Check to see if this is one of the functions we want to intercept. Note,
96 // we cast to intptr_t here to silence a -pedantic warning that complains
97 // about casting a function pointer to a normal pointer.
98 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
99 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
101 const char *NameStr = Name.c_str();
102 // If this is an asm specifier, skip the sentinal.
103 if (NameStr[0] == 1) ++NameStr;
105 // If it's an external function, look it up in the process image...
106 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
109 // If it wasn't found and if it starts with an underscore ('_') character, and
110 // has an asm specifier, try again without the underscore.
111 if (Name[0] == 1 && NameStr[0] == '_') {
112 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
116 // darwin/ppc adds $LDBLStub suffixes to various symbols like printf. These
117 // are references to hidden visibility symbols that dlsym cannot resolve. If
118 // we have one of these, strip off $LDBLStub and try again.
119 #if defined(__APPLE__) && defined(__ppc__)
120 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
121 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
122 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
123 // This mirrors logic in libSystemStubs.a.
124 std::string Prefix = std::string(Name.begin(), Name.end()-9);
125 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128"))
127 if (void *Ptr = getPointerToNamedFunction(Prefix))
132 /// If a LazyFunctionCreator is installed, use it to get/create the function.
133 if (LazyFunctionCreator)
134 if (void *RP = LazyFunctionCreator(Name))
137 cerr << "ERROR: Program used external function '" << Name
138 << "' which could not be resolved!\n";