1 //===-- Intercept.cpp - System function interception routines -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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 "Support/DynamicLinker.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.cs.uiuc.edu/PR274.
50 #if defined(__linux__)
51 void *FunctionPointers[] = {
63 // NoopFn - Used if we have nothing else to call...
64 static void NoopFn() {}
66 // jit_exit - Used to intercept the "exit" library call.
67 static void jit_exit(int Status) {
68 runAtExitHandlers(); // Run atexit handlers...
72 // jit_atexit - Used to intercept the "atexit" library call.
73 static int jit_atexit(void (*Fn)(void)) {
74 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
75 return 0; // Always successful
78 //===----------------------------------------------------------------------===//
80 /// getPointerToNamedFunction - This method returns the address of the specified
81 /// function by using the dynamic loader interface. As such it is only useful
82 /// for resolving library symbols, not code generated symbols.
84 void *JIT::getPointerToNamedFunction(const std::string &Name) {
85 // Check to see if this is one of the functions we want to intercept...
86 if (Name == "exit") return (void*)&jit_exit;
87 if (Name == "atexit") return (void*)&jit_atexit;
89 // If it's an external function, look it up in the process image...
90 void *Ptr = GetAddressOfSymbol(Name);
92 std::cerr << "WARNING: Cannot resolve fn '" << Name
93 << "' using a dummy noop function instead!\n";