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)
31      *Err = ::dlerror();
32    return &DynamicLibrary::Invalid;
33  }
34
35#ifdef __CYGWIN__
36  // Cygwin searches symbols only in the main
37  // with the handle of dlopen(NULL, RTLD_GLOBAL).
38  if (!File)
39    Handle = RTLD_DEFAULT;
40#endif
41
42  return Handle;
43}
44
45void DynamicLibrary::HandleSet::DLClose(void *Handle) { ::dlclose(Handle); }
46
47void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
48  return ::dlsym(Handle, Symbol);
49}
50
51#else // !HAVE_DLOPEN
52
53DynamicLibrary::HandleSet::~HandleSet() {}
54
55void *DynamicLibrary::HandleSet::DLOpen(const char *File, std::string *Err) {
56  if (Err)
57    *Err = "dlopen() not supported on this platform";
58  return &Invalid;
59}
60
61void DynamicLibrary::HandleSet::DLClose(void *Handle) {}
62
63void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
64  return nullptr;
65}
66
67#endif
68
69// Must declare the symbols in the global namespace.
70static void *DoSearch(const char *SymbolName) {
71#define EXPLICIT_SYMBOL(SYM)                                                   \
72  extern void *SYM;                                                            \
73  if (!strcmp(SymbolName, #SYM))                                               \
74  return (void *)&SYM
75
76  // If this is darwin, it has some funky issues, try to solve them here.  Some
77  // important symbols are marked 'private external' which doesn't allow
78  // SearchForAddressOfSymbol to find them.  As such, we special case them here,
79  // there is only a small handful of them.
80
81#ifdef __APPLE__
82  {
83    // __eprintf is sometimes used for assert() handling on x86.
84    //
85    // FIXME: Currently disabled when using Clang, as we don't always have our
86    // runtime support libraries available.
87#ifndef __clang__
88#ifdef __i386__
89    EXPLICIT_SYMBOL(__eprintf);
90#endif
91#endif
92  }
93#endif
94
95#ifdef __CYGWIN__
96  {
97    EXPLICIT_SYMBOL(_alloca);
98    EXPLICIT_SYMBOL(__main);
99  }
100#endif
101
102#undef EXPLICIT_SYMBOL
103
104// This macro returns the address of a well-known, explicit symbol
105#define EXPLICIT_SYMBOL(SYM)                                                   \
106  if (!strcmp(SymbolName, #SYM))                                               \
107  return &SYM
108
109// Under glibc we have a weird situation. The stderr/out/in symbols are both
110// macros and global variables because of standards requirements. So, we
111// boldly use the EXPLICIT_SYMBOL macro without checking for a #define first.
112#if defined(__GLIBC__)
113  {
114    EXPLICIT_SYMBOL(stderr);
115    EXPLICIT_SYMBOL(stdout);
116    EXPLICIT_SYMBOL(stdin);
117  }
118#else
119  // For everything else, we want to check to make sure the symbol isn't defined
120  // as a macro before using EXPLICIT_SYMBOL.
121  {
122#ifndef stdin
123    EXPLICIT_SYMBOL(stdin);
124#endif
125#ifndef stdout
126    EXPLICIT_SYMBOL(stdout);
127#endif
128#ifndef stderr
129    EXPLICIT_SYMBOL(stderr);
130#endif
131  }
132#endif
133#undef EXPLICIT_SYMBOL
134
135  return nullptr;
136}
137