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//===-- Intercept.cpp - System function interception routines -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// If a function call occurs to an external function, the JIT is designed to use
// the dynamic loader interface to find a function to call. This is useful for
// calling system calls and library functions that are not available in LLVM.
// Some system calls, however, need to be handled specially. For this reason,
// we intercept some of them here and use our own stubs to handle them.
//
//===----------------------------------------------------------------------===//
#include "VM.h"
#include "Support/DynamicLinker.h"
#include <iostream>
namespace llvm {
// AtExitHandlers - List of functions to call when the program exits,
// registered with the atexit() library function.
static std::vector<void (*)()> AtExitHandlers;
/// runAtExitHandlers - Run any functions registered by the program's
/// calls to atexit(3), which we intercept and store in
/// AtExitHandlers.
///
void VM::runAtExitHandlers() {
while (!AtExitHandlers.empty()) {
void (*Fn)() = AtExitHandlers.back();
AtExitHandlers.pop_back();
Fn();
}
}
//===----------------------------------------------------------------------===//
// Function stubs that are invoked instead of certain library calls
//===----------------------------------------------------------------------===//
// NoopFn - Used if we have nothing else to call...
static void NoopFn() {}
// jit_exit - Used to intercept the "exit" library call.
static void jit_exit(int Status) {
VM::runAtExitHandlers(); // Run atexit handlers...
exit(Status);
}
// jit_atexit - Used to intercept the "atexit" library call.
static int jit_atexit(void (*Fn)(void)) {
AtExitHandlers.push_back(Fn); // Take note of atexit handler...
return 0; // Always successful
}
//===----------------------------------------------------------------------===//
//
/// getPointerToNamedFunction - This method returns the address of the specified
/// function by using the dynamic loader interface. As such it is only useful
/// for resolving library symbols, not code generated symbols.
///
void *VM::getPointerToNamedFunction(const std::string &Name) {
// Check to see if this is one of the functions we want to intercept...
if (Name == "exit") return (void*)&jit_exit;
if (Name == "atexit") return (void*)&jit_atexit;
// If it's an external function, look it up in the process image...
void *Ptr = GetAddressOfSymbol(Name);
if (Ptr == 0) {
std::cerr << "WARNING: Cannot resolve fn '" << Name
<< "' using a dummy noop function instead!\n";
Ptr = (void*)NoopFn;
}
return Ptr;
}
} // End llvm namespace
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