1 //===-- Intercept.cpp - System function interception routines -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // If a function call occurs to an external function, the JIT is designed to use
11 // the dynamic loader interface to find a function to call. This is useful for
12 // calling system calls and library functions that are not available in LLVM.
13 // Some system calls, however, need to be handled specially. For this reason,
14 // we intercept some of them here and use our own stubs to handle them.
16 //===----------------------------------------------------------------------===//
19 #include "llvm/System/DynamicLibrary.h"
20 #include "llvm/Config/config.h"
23 // AtExitHandlers - List of functions to call when the program exits,
24 // registered with the atexit() library function.
25 static std::vector<void (*)()> AtExitHandlers;
27 /// runAtExitHandlers - Run any functions registered by the program's
28 /// calls to atexit(3), which we intercept and store in
31 static void runAtExitHandlers() {
32 while (!AtExitHandlers.empty()) {
33 void (*Fn)() = AtExitHandlers.back();
34 AtExitHandlers.pop_back();
39 //===----------------------------------------------------------------------===//
40 // Function stubs that are invoked instead of certain library calls
41 //===----------------------------------------------------------------------===//
43 // Force the following functions to be linked in to anything that uses the
44 // JIT. This is a hack designed to work around the all-too-clever Glibc
45 // strategy of making these functions work differently when inlined vs. when
46 // not inlined, and hiding their real definitions in a separate archive file
47 // that the dynamic linker can't see. For more info, search for
48 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
49 #if defined(__linux__)
50 #if defined(HAVE_SYS_STAT_H)
53 void *FunctionPointers[] = {
54 (void *)(intptr_t) stat,
55 (void *)(intptr_t) fstat,
56 (void *)(intptr_t) lstat,
57 (void *)(intptr_t) stat64,
58 (void *)(intptr_t) fstat64,
59 (void *)(intptr_t) lstat64,
60 (void *)(intptr_t) atexit,
61 (void *)(intptr_t) mknod
65 // __mainFunc - If the program does not have a linked in __main function, allow
66 // it to run, but print a warning.
67 static void __mainFunc() {
68 fprintf(stderr, "WARNING: Program called __main but was not linked to "
69 "libcrtend.a.\nThis probably won't hurt anything unless the "
70 "program is written in C++.\n");
73 // jit_exit - Used to intercept the "exit" library call.
74 static void jit_exit(int Status) {
75 runAtExitHandlers(); // Run atexit handlers...
79 // jit_atexit - Used to intercept the "atexit" library call.
80 static int jit_atexit(void (*Fn)(void)) {
81 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
82 return 0; // Always successful
85 //===----------------------------------------------------------------------===//
87 /// getPointerToNamedFunction - This method returns the address of the specified
88 /// function by using the dynamic loader interface. As such it is only useful
89 /// for resolving library symbols, not code generated symbols.
91 void *JIT::getPointerToNamedFunction(const std::string &Name) {
92 // Check to see if this is one of the functions we want to intercept. Note,
93 // we cast to intptr_t here to silence a -pedantic warning that complains
94 // about casting a function pointer to a normal pointer.
95 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
96 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
98 // If the program does not have a linked in __main function, allow it to run,
99 // but print a warning.
100 if (Name == "__main") return (void*)(intptr_t)&__mainFunc;
102 const char *NameStr = Name.c_str();
103 // If this is an asm specifier, skip the sentinal.
104 if (NameStr[0] == 1) ++NameStr;
106 // If it's an external function, look it up in the process image...
107 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
110 // If it wasn't found and if it starts with an underscore ('_') character, and
111 // has an asm specifier, try again without the underscore.
112 if (Name[0] == 1 && NameStr[0] == '_') {
113 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
117 cerr << "ERROR: Program used external function '" << Name
118 << "' which could not be resolved!\n";