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