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//===-- Intercept.cpp - System function interception routines -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file 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 "MCJIT.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Config/config.h"
using 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.
///
static void runAtExitHandlers() {
while (!AtExitHandlers.empty()) {
void (*Fn)() = AtExitHandlers.back();
AtExitHandlers.pop_back();
Fn();
}
}
//===----------------------------------------------------------------------===//
// Function stubs that are invoked instead of certain library calls
//===----------------------------------------------------------------------===//
// Force the following functions to be linked in to anything that uses the
// JIT. This is a hack designed to work around the all-too-clever Glibc
// strategy of making these functions work differently when inlined vs. when
// not inlined, and hiding their real definitions in a separate archive file
// that the dynamic linker can't see. For more info, search for
// 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
#if defined(__linux__)
#if defined(HAVE_SYS_STAT_H)
#include <sys/stat.h>
#endif
#include <fcntl.h>
#include <unistd.h>
/* stat functions are redirecting to __xstat with a version number. On x86-64
* linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
* available as an exported symbol, so we have to add it explicitly.
*/
namespace {
class StatSymbols {
public:
StatSymbols() {
sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
}
};
}
static StatSymbols initStatSymbols;
#endif // __linux__
// jit_exit - Used to intercept the "exit" library call.
static void jit_exit(int Status) {
runAtExitHandlers(); // Run atexit handlers...
exit(Status);
}
// jit_atexit - Used to intercept the "atexit" library call.
static int jit_atexit(void (*Fn)()) {
AtExitHandlers.push_back(Fn); // Take note of atexit handler...
return 0; // Always successful
}
static int jit_noop() {
return 0;
}
//===----------------------------------------------------------------------===//
//
/// 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 *MCJIT::getPointerToNamedFunction(const std::string &Name,
bool AbortOnFailure) {
if (!isSymbolSearchingDisabled()) {
// Check to see if this is one of the functions we want to intercept. Note,
// we cast to intptr_t here to silence a -pedantic warning that complains
// about casting a function pointer to a normal pointer.
if (Name == "exit") return (void*)(intptr_t)&jit_exit;
if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
// We should not invoke parent's ctors/dtors from generated main()!
// On Mingw and Cygwin, the symbol __main is resolved to
// callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
// (and register wrong callee's dtors with atexit(3)).
// We expect ExecutionEngine::runStaticConstructorsDestructors()
// is called before ExecutionEngine::runFunctionAsMain() is called.
if (Name == "__main") return (void*)(intptr_t)&jit_noop;
const char *NameStr = Name.c_str();
// If this is an asm specifier, skip the sentinal.
if (NameStr[0] == 1) ++NameStr;
// If it's an external function, look it up in the process image...
void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
if (Ptr) return Ptr;
// If it wasn't found and if it starts with an underscore ('_') character,
// and has an asm specifier, try again without the underscore.
if (Name[0] == 1 && NameStr[0] == '_') {
Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
if (Ptr) return Ptr;
}
// Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
// are references to hidden visibility symbols that dlsym cannot resolve.
// If we have one of these, strip off $LDBLStub and try again.
#if defined(__APPLE__) && defined(__ppc__)
if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
// First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
// This mirrors logic in libSystemStubs.a.
std::string Prefix = std::string(Name.begin(), Name.end()-9);
if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
return Ptr;
if (void *Ptr = getPointerToNamedFunction(Prefix, false))
return Ptr;
}
#endif
}
/// If a LazyFunctionCreator is installed, use it to get/create the function.
if (LazyFunctionCreator)
if (void *RP = LazyFunctionCreator(Name))
return RP;
if (AbortOnFailure) {
report_fatal_error("Program used external function '"+Name+
"' which could not be resolved!");
}
return 0;
}
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