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Dan Gohmanf17a25c2007-07-18 16:29:46 +00001//===-- Intercept.cpp - System function interception routines -------------===//
2//
3// The LLVM Compiler Infrastructure
4//
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.
7//
8//===----------------------------------------------------------------------===//
9//
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.
15//
16//===----------------------------------------------------------------------===//
17
18#include "JIT.h"
19#include "llvm/System/DynamicLibrary.h"
20#include "llvm/Config/config.h"
21using namespace llvm;
22
23// AtExitHandlers - List of functions to call when the program exits,
24// registered with the atexit() library function.
25static std::vector<void (*)()> AtExitHandlers;
26
27/// runAtExitHandlers - Run any functions registered by the program's
28/// calls to atexit(3), which we intercept and store in
29/// AtExitHandlers.
30///
31static void runAtExitHandlers() {
32 while (!AtExitHandlers.empty()) {
33 void (*Fn)() = AtExitHandlers.back();
34 AtExitHandlers.pop_back();
35 Fn();
36 }
37}
38
39//===----------------------------------------------------------------------===//
40// Function stubs that are invoked instead of certain library calls
41//===----------------------------------------------------------------------===//
42
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)
51#include <sys/stat.h>
52#endif
53void *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
62};
63#endif // __linux__
64
Dan Gohmanf17a25c2007-07-18 16:29:46 +000065// jit_exit - Used to intercept the "exit" library call.
66static void jit_exit(int Status) {
67 runAtExitHandlers(); // Run atexit handlers...
68 exit(Status);
69}
70
71// jit_atexit - Used to intercept the "atexit" library call.
72static int jit_atexit(void (*Fn)(void)) {
73 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
74 return 0; // Always successful
75}
76
77//===----------------------------------------------------------------------===//
78//
79/// getPointerToNamedFunction - This method returns the address of the specified
80/// function by using the dynamic loader interface. As such it is only useful
81/// for resolving library symbols, not code generated symbols.
82///
83void *JIT::getPointerToNamedFunction(const std::string &Name) {
84 // Check to see if this is one of the functions we want to intercept. Note,
85 // we cast to intptr_t here to silence a -pedantic warning that complains
86 // about casting a function pointer to a normal pointer.
87 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
88 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
89
Dan Gohmanf17a25c2007-07-18 16:29:46 +000090 const char *NameStr = Name.c_str();
91 // If this is an asm specifier, skip the sentinal.
92 if (NameStr[0] == 1) ++NameStr;
93
94 // If it's an external function, look it up in the process image...
95 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
96 if (Ptr) return Ptr;
97
98 // If it wasn't found and if it starts with an underscore ('_') character, and
99 // has an asm specifier, try again without the underscore.
100 if (Name[0] == 1 && NameStr[0] == '_') {
101 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
102 if (Ptr) return Ptr;
103 }
Chris Lattner5c507602007-10-22 02:50:12 +0000104
Chris Lattner5370e622007-11-27 20:41:32 +0000105 // darwin/ppc adds $LDBLStub suffixes to various symbols like printf. These
106 // are references to hidden visibility symbols that dlsym cannot resolve. If
107 // we have one of these, strip off $LDBLStub and try again.
108#if defined(__APPLE__) && defined(__ppc__)
109 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
Chris Lattnerbe0616f2007-11-27 20:45:25 +0000110 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
111 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
112 // This mirrors logic in libSystemStubs.a.
113 std::string Prefix = std::string(Name.begin(), Name.end()-9);
114 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128"))
115 return Ptr;
Chris Lattner97449e92007-11-28 18:30:18 +0000116 if (void *Ptr = getPointerToNamedFunction(Prefix))
117 return Ptr;
Chris Lattnerbe0616f2007-11-27 20:45:25 +0000118 }
Chris Lattner5370e622007-11-27 20:41:32 +0000119#endif
120
Chris Lattner5c507602007-10-22 02:50:12 +0000121 /// If a LazyFunctionCreator is installed, use it to get/create the function.
122 if (LazyFunctionCreator)
123 if (void *RP = LazyFunctionCreator(Name))
124 return RP;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000125
126 cerr << "ERROR: Program used external function '" << Name
127 << "' which could not be resolved!\n";
128 abort();
129 return 0;
130}