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//===-- Intercept.cpp - System function interception routines -------------===//
//
// If a function call occurs to an external function, the JIT is designed to use
// dlsym on the current process 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 "Config/dlfcn.h" // dlsym access
#include <iostream>
// AtExitList - List of functions registered with the at_exit function
static std::vector<void (*)()> AtExitList;
void VM::runAtExitHandlers() {
while (!AtExitList.empty()) {
void (*Fn)() = AtExitList.back();
AtExitList.pop_back();
Fn();
}
}
//===----------------------------------------------------------------------===//
// Function stubs that are invoked instead of raw system calls
//===----------------------------------------------------------------------===//
// NoopFn - Used if we have nothing else to call...
static void NoopFn() {}
// jit_exit - Used to intercept the "exit" system call.
static void jit_exit(int Status) {
VM::runAtExitHandlers(); // Run at_exit handlers...
exit(Status);
}
// jit_atexit - Used to intercept the "at_exit" system call.
static int jit_atexit(void (*Fn)(void)) {
AtExitList.push_back(Fn); // Take note of at_exit handler...
return 0; // Always successful
}
//===----------------------------------------------------------------------===//
//
/// getPointerToNamedFunction - This method returns the address of the specified
/// function by using the dlsym function call. 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...
#if defined(i386) || defined(__i386__) || defined(__x86__)
void *Ptr = dlsym(0, Name.c_str());
#elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
void *Ptr = dlsym(RTLD_SELF, Name.c_str());
#endif
if (Ptr == 0) {
std::cerr << "WARNING: Cannot resolve fn '" << Name
<< "' using a dummy noop function instead!\n";
Ptr = (void*)NoopFn;
}
return Ptr;
}
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