forked from OSchip/llvm-project
122 lines
4.7 KiB
C++
122 lines
4.7 KiB
C++
//===-- Intercept.cpp - System function interception routines -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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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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//===----------------------------------------------------------------------===//
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#include "JIT.h"
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#include "llvm/System/DynamicLibrary.h"
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#include "llvm/Config/config.h"
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using namespace llvm;
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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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/// AtExitHandlers.
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///
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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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Fn();
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}
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}
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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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#include <sys/stat.h>
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#endif
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void *FunctionPointers[] = {
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(void *)(intptr_t) stat,
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(void *)(intptr_t) fstat,
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(void *)(intptr_t) lstat,
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(void *)(intptr_t) stat64,
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(void *)(intptr_t) fstat64,
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(void *)(intptr_t) lstat64,
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(void *)(intptr_t) atexit,
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(void *)(intptr_t) mknod
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};
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#endif // __linux__
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// __mainFunc - If the program does not have a linked in __main function, allow
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// it to run, but print a warning.
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static void __mainFunc() {
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fprintf(stderr, "WARNING: Program called __main but was not linked to "
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"libcrtend.a.\nThis probably won't hurt anything unless the "
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"program is written in C++.\n");
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}
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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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exit(Status);
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}
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// jit_atexit - Used to intercept the "atexit" library call.
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static int jit_atexit(void (*Fn)(void)) {
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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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}
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//===----------------------------------------------------------------------===//
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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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///
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void *JIT::getPointerToNamedFunction(const std::string &Name) {
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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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// If the program does not have a linked in __main function, allow it to run,
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// but print a warning.
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if (Name == "__main") return (void*)(intptr_t)&__mainFunc;
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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 (Ptr) return Ptr;
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// If it wasn't found and if it starts with an underscore ('_') character, and
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// 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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if (Ptr) return Ptr;
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}
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cerr << "ERROR: Program used external function '" << Name
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<< "' which could not be resolved!\n";
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abort();
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return 0;
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}
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