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 "llvm/System/DynamicLibrary.h"
21 #if defined(__linux__)
26 // AtExitHandlers - List of functions to call when the program exits,
27 // registered with the atexit() library function.
28 static std::vector<void (*)()> AtExitHandlers;
30 /// runAtExitHandlers - Run any functions registered by the program's
31 /// calls to atexit(3), which we intercept and store in
34 static void runAtExitHandlers() {
35 while (!AtExitHandlers.empty()) {
36 void (*Fn)() = AtExitHandlers.back();
37 AtExitHandlers.pop_back();
42 //===----------------------------------------------------------------------===//
43 // Function stubs that are invoked instead of certain library calls
44 //===----------------------------------------------------------------------===//
46 // Force the following functions to be linked in to anything that uses the
47 // JIT. This is a hack designed to work around the all-too-clever Glibc
48 // strategy of making these functions work differently when inlined vs. when
49 // not inlined, and hiding their real definitions in a separate archive file
50 // that the dynamic linker can't see. For more info, search for
51 // 'libc_nonshared.a' on Google, or read http://llvm.cs.uiuc.edu/PR274.
52 #if defined(__linux__)
53 void *FunctionPointers[] = {
65 // __mainFunc - If the program does not have a linked in __main function, allow
66 // it to run, but print a warning.
67 static void __mainFunc() {
68 fprintf(stderr, "WARNING: Program called __main but was not linked to "
69 "libcrtend.a.\nThis probably won't hurt anything unless the "
70 "program is written in C++.\n");
73 // jit_exit - Used to intercept the "exit" library call.
74 static void jit_exit(int Status) {
75 runAtExitHandlers(); // Run atexit handlers...
79 // jit_atexit - Used to intercept the "atexit" library call.
80 static int jit_atexit(void (*Fn)(void)) {
81 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
82 return 0; // Always successful
85 //===----------------------------------------------------------------------===//
87 /// getPointerToNamedFunction - This method returns the address of the specified
88 /// function by using the dynamic loader interface. As such it is only useful
89 /// for resolving library symbols, not code generated symbols.
91 void *JIT::getPointerToNamedFunction(const std::string &Name) {
92 // Check to see if this is one of the functions we want to intercept...
93 if (Name == "exit") return (void*)&jit_exit;
94 if (Name == "atexit") return (void*)&jit_atexit;
96 // If the program does not have a linked in __main function, allow it to run,
97 // but print a warning.
98 if (Name == "__main") return (void*)&__mainFunc;
100 // If it's an external function, look it up in the process image...
101 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(Name);
104 std::cerr << "ERROR: Program used external function '" << Name
105 << "' which could not be resolved!\n";