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"
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 // NoopFn - Used if we have nothing else to call...
44 static void NoopFn() {}
46 // jit_exit - Used to intercept the "exit" library call.
47 static void jit_exit(int Status) {
48 runAtExitHandlers(); // Run atexit handlers...
52 // jit_atexit - Used to intercept the "atexit" library call.
53 static int jit_atexit(void (*Fn)(void)) {
54 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
55 return 0; // Always successful
58 //===----------------------------------------------------------------------===//
60 /// getPointerToNamedFunction - This method returns the address of the specified
61 /// function by using the dynamic loader interface. As such it is only useful
62 /// for resolving library symbols, not code generated symbols.
64 void *JIT::getPointerToNamedFunction(const std::string &Name) {
65 // Check to see if this is one of the functions we want to intercept...
66 if (Name == "exit") return (void*)&jit_exit;
67 if (Name == "atexit") return (void*)&jit_atexit;
69 // If it's an external function, look it up in the process image...
70 void *Ptr = GetAddressOfSymbol(Name);
72 std::cerr << "WARNING: Cannot resolve fn '" << Name
73 << "' using a dummy noop function instead!\n";