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"
22 // AtExitHandlers - List of functions to call when the program exits,
23 // registered with the atexit() library function.
24 static std::vector<void (*)()> AtExitHandlers;
26 /// runAtExitHandlers - Run any functions registered by the program's
27 /// calls to atexit(3), which we intercept and store in
30 void VM::runAtExitHandlers() {
31 while (!AtExitHandlers.empty()) {
32 void (*Fn)() = AtExitHandlers.back();
33 AtExitHandlers.pop_back();
38 //===----------------------------------------------------------------------===//
39 // Function stubs that are invoked instead of certain library calls
40 //===----------------------------------------------------------------------===//
42 // NoopFn - Used if we have nothing else to call...
43 static void NoopFn() {}
45 // jit_exit - Used to intercept the "exit" library call.
46 static void jit_exit(int Status) {
47 VM::runAtExitHandlers(); // Run atexit handlers...
51 // jit_atexit - Used to intercept the "atexit" library call.
52 static int jit_atexit(void (*Fn)(void)) {
53 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
54 return 0; // Always successful
57 //===----------------------------------------------------------------------===//
59 /// getPointerToNamedFunction - This method returns the address of the specified
60 /// function by using the dynamic loader interface. As such it is only useful
61 /// for resolving library symbols, not code generated symbols.
63 void *VM::getPointerToNamedFunction(const std::string &Name) {
64 // Check to see if this is one of the functions we want to intercept...
65 if (Name == "exit") return (void*)&jit_exit;
66 if (Name == "atexit") return (void*)&jit_atexit;
68 // If it's an external function, look it up in the process image...
69 void *Ptr = GetAddressOfSymbol(Name);
71 std::cerr << "WARNING: Cannot resolve fn '" << Name
72 << "' using a dummy noop function instead!\n";