1/* crtbegin object for windows32 targets.
2   Copyright (C) 2007-2020 Free Software Foundation, Inc.
3
4   Contributed by Danny Smith <dannysmith@users.sourceforge.net>
5
6This file is part of GCC.
7
8GCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
16for more details.
17
18Under Section 7 of GPL version 3, you are granted additional
19permissions described in the GCC Runtime Library Exception, version
203.1, as published by the Free Software Foundation.
21
22You should have received a copy of the GNU General Public License and
23a copy of the GCC Runtime Library Exception along with this program;
24see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
25<http://www.gnu.org/licenses/>.  */
26
27/* Target machine header files require this define. */
28#define IN_LIBGCC2
29
30#include "auto-host.h"
31#include "tconfig.h"
32#include "tsystem.h"
33#include "coretypes.h"
34#include "tm.h"
35#include "libgcc_tm.h"
36#include "unwind-dw2-fde.h"
37
38#define WIN32_LEAN_AND_MEAN
39#include <windows.h>
40
41#ifndef LIBGCC_SONAME
42#define LIBGCC_SONAME "libgcc_s.dll"
43#endif
44
45#if DWARF2_UNWIND_INFO
46/* Make the declarations weak.  This is critical for
47   _Jv_RegisterClasses because it lives in libgcj.a  */
48extern void __register_frame_info (__attribute__((unused)) const void *,
49				   __attribute__((unused)) struct object *)
50				   TARGET_ATTRIBUTE_WEAK;
51extern void *__deregister_frame_info (__attribute__((unused)) const void *)
52				      TARGET_ATTRIBUTE_WEAK;
53
54/* Work around for current cygwin32 build problems (Bug gas/16858).
55   Compile weak default functions only for 64-bit systems,
56   when absolutely necessary.  */
57#ifdef __x86_64__
58TARGET_ATTRIBUTE_WEAK void
59__register_frame_info (__attribute__((unused)) const void *p,
60		       __attribute__((unused)) struct object *o)
61{
62}
63
64TARGET_ATTRIBUTE_WEAK void *
65__deregister_frame_info (__attribute__((unused)) const void *p)
66{
67  return (void*) 0;
68}
69#endif
70#endif /* DWARF2_UNWIND_INFO */
71
72#if defined(HAVE_LD_RO_RW_SECTION_MIXING)
73# define EH_FRAME_SECTION_CONST const
74#else
75# define EH_FRAME_SECTION_CONST
76#endif
77
78/* Stick a label at the beginning of the frame unwind info so we can
79   register/deregister it with the exception handling library code.  */
80#if DWARF2_UNWIND_INFO
81static EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
82  __attribute__((used, section(__LIBGCC_EH_FRAME_SECTION_NAME__), aligned(4)))
83  = { };
84
85static struct object obj;
86
87/* Handle of libgcc's DLL reference.  */
88HANDLE hmod_libgcc;
89static void *  (*deregister_frame_fn) (const void *) = NULL;
90#endif
91
92#ifdef __CYGWIN__
93/* Declare the __dso_handle variable.  It should have a unique value
94   in every shared-object; in a main program its value is zero.  The
95   object should in any case be protected.  This means the instance
96   in one DSO or the main program is not used in another object.  The
97   dynamic linker takes care of this.  */
98
99#ifdef CRTSTUFFS_O
100extern void *__ImageBase;
101void *__dso_handle = &__ImageBase;
102#else
103void *__dso_handle = 0;
104#endif
105
106#endif /* __CYGWIN__ */
107
108
109/* Pull in references from libgcc.a(unwind-dw2-fde.o) in the
110   startfile. These are referenced by a ctor and dtor in crtend.o.  */
111extern void __gcc_register_frame (void);
112extern void __gcc_deregister_frame (void);
113
114void
115__gcc_register_frame (void)
116{
117#if DWARF2_UNWIND_INFO
118/* Weak undefined symbols won't be pulled in from dlls; hence
119   we first test if the dll is already loaded and, if so,
120   get the symbol's address at run-time.  If the dll is not loaded,
121   fallback to weak linkage to static archive.  */
122
123  void (*register_frame_fn) (const void *, struct object *);
124  HANDLE h = GetModuleHandle (LIBGCC_SONAME);
125
126  if (h)
127    {
128      /* Increasing the load-count of LIBGCC_SONAME DLL.  */
129      hmod_libgcc = LoadLibrary (LIBGCC_SONAME);
130      register_frame_fn = (void (*) (const void *, struct object *))
131			  GetProcAddress (h, "__register_frame_info");
132      deregister_frame_fn = (void* (*) (const void *))
133	                    GetProcAddress (h, "__deregister_frame_info");
134    }
135  else
136    {
137      register_frame_fn = __register_frame_info;
138      deregister_frame_fn = __deregister_frame_info;
139    }
140  if (register_frame_fn)
141     register_frame_fn (__EH_FRAME_BEGIN__, &obj);
142#endif
143
144#if DEFAULT_USE_CXA_ATEXIT
145  /* If we use the __cxa_atexit method to register C++ dtors
146     at object construction,  also use atexit to register eh frame
147     info cleanup.  */
148  atexit(__gcc_deregister_frame);
149#endif /* DEFAULT_USE_CXA_ATEXIT */
150}
151
152void
153__gcc_deregister_frame (void)
154{
155#if DWARF2_UNWIND_INFO
156  if (deregister_frame_fn)
157     deregister_frame_fn (__EH_FRAME_BEGIN__);
158  if (hmod_libgcc)
159    FreeLibrary (hmod_libgcc);
160#endif
161}
162