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/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.
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
);
77 static StatSymbols initStatSymbols
;
80 // jit_exit - Used to intercept the "exit" library call.
81 static void jit_exit(int Status
) {
82 runAtExitHandlers(); // Run atexit handlers...
86 // jit_atexit - Used to intercept the "atexit" library call.
87 static int jit_atexit(void (*Fn
)()) {
88 AtExitHandlers
.push_back(Fn
); // Take note of atexit handler...
89 return 0; // Always successful
92 static int jit_noop() {
96 //===----------------------------------------------------------------------===//
98 /// getPointerToNamedFunction - This method returns the address of the specified
99 /// function by using the dynamic loader interface. As such it is only useful
100 /// for resolving library symbols, not code generated symbols.
102 void *JIT::getPointerToNamedFunction(const std::string
&Name
,
103 bool AbortOnFailure
) {
104 if (!isSymbolSearchingDisabled()) {
105 // Check to see if this is one of the functions we want to intercept. Note,
106 // we cast to intptr_t here to silence a -pedantic warning that complains
107 // about casting a function pointer to a normal pointer.
108 if (Name
== "exit") return (void*)(intptr_t)&jit_exit
;
109 if (Name
== "atexit") return (void*)(intptr_t)&jit_atexit
;
111 // We should not invoke parent's ctors/dtors from generated main()!
112 // On Mingw and Cygwin, the symbol __main is resolved to
113 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
114 // (and register wrong callee's dtors with atexit(3)).
115 // We expect ExecutionEngine::runStaticConstructorsDestructors()
116 // is called before ExecutionEngine::runFunctionAsMain() is called.
117 if (Name
== "__main") return (void*)(intptr_t)&jit_noop
;
119 const char *NameStr
= Name
.c_str();
120 // If this is an asm specifier, skip the sentinal.
121 if (NameStr
[0] == 1) ++NameStr
;
123 // If it's an external function, look it up in the process image...
124 void *Ptr
= sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr
);
127 // If it wasn't found and if it starts with an underscore ('_') character,
128 // and has an asm specifier, try again without the underscore.
129 if (Name
[0] == 1 && NameStr
[0] == '_') {
130 Ptr
= sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr
+1);
134 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
135 // are references to hidden visibility symbols that dlsym cannot resolve.
136 // If we have one of these, strip off $LDBLStub and try again.
137 #if defined(__APPLE__) && defined(__ppc__)
138 if (Name
.size() > 9 && Name
[Name
.size()-9] == '$' &&
139 memcmp(&Name
[Name
.size()-8], "LDBLStub", 8) == 0) {
140 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
141 // This mirrors logic in libSystemStubs.a.
142 std::string Prefix
= std::string(Name
.begin(), Name
.end()-9);
143 if (void *Ptr
= getPointerToNamedFunction(Prefix
+"$LDBL128", false))
145 if (void *Ptr
= getPointerToNamedFunction(Prefix
, false))
151 /// If a LazyFunctionCreator is installed, use it to get/create the function.
152 if (LazyFunctionCreator
)
153 if (void *RP
= LazyFunctionCreator(Name
))
156 if (AbortOnFailure
) {
157 report_fatal_error("Program used external function '"+Name
+
158 "' which could not be resolved!");