1//===- Unix/DynamicLibrary.cpp - Unix DL Implementation ---------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file provides the UNIX specific implementation of DynamicLibrary.
10//
11//===----------------------------------------------------------------------===//
12
13#if defined(HAVE_DLFCN_H) && defined(HAVE_DLOPEN)
14#include <dlfcn.h>
15
16DynamicLibrary::HandleSet::~HandleSet() {
17  // Close the libraries in reverse order.
18  for (void *Handle : llvm::reverse(Handles))
19    ::dlclose(Handle);
20  if (Process)
21    ::dlclose(Process);
22
23  // llvm_shutdown called, Return to default
24  DynamicLibrary::SearchOrder = DynamicLibrary::SO_Linker;
25}
26
27void *DynamicLibrary::HandleSet::DLOpen(const char *File, std::string *Err) {
28  void *Handle = ::dlopen(File, RTLD_LAZY|RTLD_GLOBAL);
29  if (!Handle) {
30    if (Err) *Err = ::dlerror();
31    return &DynamicLibrary::Invalid;
32  }
33
34#ifdef __CYGWIN__
35  // Cygwin searches symbols only in the main
36  // with the handle of dlopen(NULL, RTLD_GLOBAL).
37  if (!File)
38    Handle = RTLD_DEFAULT;
39#endif
40
41  return Handle;
42}
43
44void DynamicLibrary::HandleSet::DLClose(void *Handle) {
45  ::dlclose(Handle);
46}
47
48void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
49  return ::dlsym(Handle, Symbol);
50}
51
52#else // !HAVE_DLOPEN
53
54DynamicLibrary::HandleSet::~HandleSet() {}
55
56void *DynamicLibrary::HandleSet::DLOpen(const char *File, std::string *Err) {
57  if (Err) *Err = "dlopen() not supported on this platform";
58  return &Invalid;
59}
60
61void DynamicLibrary::HandleSet::DLClose(void *Handle) {
62}
63
64void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
65  return nullptr;
66}
67
68#endif
69
70// Must declare the symbols in the global namespace.
71static void *DoSearch(const char* SymbolName) {
72#define EXPLICIT_SYMBOL(SYM) \
73   extern void *SYM; if (!strcmp(SymbolName, #SYM)) return (void*)&SYM
74
75  // If this is darwin, it has some funky issues, try to solve them here.  Some
76  // important symbols are marked 'private external' which doesn't allow
77  // SearchForAddressOfSymbol to find them.  As such, we special case them here,
78  // there is only a small handful of them.
79
80#ifdef __APPLE__
81  {
82    // __eprintf is sometimes used for assert() handling on x86.
83    //
84    // FIXME: Currently disabled when using Clang, as we don't always have our
85    // runtime support libraries available.
86#ifndef __clang__
87#ifdef __i386__
88    EXPLICIT_SYMBOL(__eprintf);
89#endif
90#endif
91  }
92#endif
93
94#ifdef __CYGWIN__
95  {
96    EXPLICIT_SYMBOL(_alloca);
97    EXPLICIT_SYMBOL(__main);
98  }
99#endif
100
101#undef EXPLICIT_SYMBOL
102
103// This macro returns the address of a well-known, explicit symbol
104#define EXPLICIT_SYMBOL(SYM) \
105   if (!strcmp(SymbolName, #SYM)) return &SYM
106
107// Under glibc we have a weird situation. The stderr/out/in symbols are both
108// macros and global variables because of standards requirements. So, we
109// boldly use the EXPLICIT_SYMBOL macro without checking for a #define first.
110#if defined(__GLIBC__)
111  {
112    EXPLICIT_SYMBOL(stderr);
113    EXPLICIT_SYMBOL(stdout);
114    EXPLICIT_SYMBOL(stdin);
115  }
116#else
117  // For everything else, we want to check to make sure the symbol isn't defined
118  // as a macro before using EXPLICIT_SYMBOL.
119  {
120#ifndef stdin
121    EXPLICIT_SYMBOL(stdin);
122#endif
123#ifndef stdout
124    EXPLICIT_SYMBOL(stdout);
125#endif
126#ifndef stderr
127    EXPLICIT_SYMBOL(stderr);
128#endif
129  }
130#endif
131#undef EXPLICIT_SYMBOL
132
133  return nullptr;
134}
135