1 // -*- C++ -*- Allocate exception objects.
2 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009, 2011
3 // Free Software Foundation, Inc.
4 //
5 // This file is part of GCC.
6 //
7 // GCC is free software; you can redistribute it and/or modify
8 // it under the terms of the GNU General Public License as published by
9 // the Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 //
12 // GCC is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 // GNU General Public License for more details.
16 //
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 // This is derived from the C++ ABI for IA-64.  Where we diverge
27 // for cross-architecture compatibility are noted with "@@@".
28 
29 #include <bits/c++config.h>
30 #include <cstdlib>
31 #if _GLIBCXX_HOSTED
32 #include <cstring>
33 #endif
34 #include <climits>
35 #include <exception>
36 #include "unwind-cxx.h"
37 #include <ext/concurrence.h>
38 
39 #if _GLIBCXX_HOSTED
40 using std::free;
41 using std::malloc;
42 using std::memset;
43 #else
44 // In a freestanding environment, these functions may not be available
45 // -- but for now, we assume that they are.
46 extern "C" void *malloc (std::size_t);
47 extern "C" void free(void *);
48 extern "C" void *memset (void *, int, std::size_t);
49 #endif
50 
51 using namespace __cxxabiv1;
52 
53 // ??? How to control these parameters.
54 
55 // Guess from the size of basic types how large a buffer is reasonable.
56 // Note that the basic c++ exception header has 13 pointers and 2 ints,
57 // so on a system with PSImode pointers we're talking about 56 bytes
58 // just for overhead.
59 
60 #if INT_MAX == 32767
61 # define EMERGENCY_OBJ_SIZE	128
62 # define EMERGENCY_OBJ_COUNT	16
63 #elif LONG_MAX == 2147483647
64 # define EMERGENCY_OBJ_SIZE	512
65 # define EMERGENCY_OBJ_COUNT	32
66 #else
67 # define EMERGENCY_OBJ_SIZE	1024
68 # define EMERGENCY_OBJ_COUNT	64
69 #endif
70 
71 #ifndef __GTHREADS
72 # undef EMERGENCY_OBJ_COUNT
73 # define EMERGENCY_OBJ_COUNT	4
74 #endif
75 
76 #if INT_MAX == 32767 || EMERGENCY_OBJ_COUNT <= 32
77 typedef unsigned int bitmask_type;
78 #else
79 typedef unsigned long bitmask_type;
80 #endif
81 
82 
83 typedef char one_buffer[EMERGENCY_OBJ_SIZE] __attribute__((aligned));
84 static one_buffer emergency_buffer[EMERGENCY_OBJ_COUNT];
85 static bitmask_type emergency_used;
86 
87 static __cxa_dependent_exception dependents_buffer[EMERGENCY_OBJ_COUNT];
88 static bitmask_type dependents_used;
89 
90 namespace
91 {
92   // A single mutex controlling emergency allocations.
93   __gnu_cxx::__mutex emergency_mutex;
94 }
95 
96 extern "C" void *
97 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
98 {
99   void *ret;
100 
101   thrown_size += sizeof (__cxa_refcounted_exception);
102   ret = malloc (thrown_size);
103 
104   if (! ret)
105     {
106       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
107 
108       bitmask_type used = emergency_used;
109       unsigned int which = 0;
110 
111       if (thrown_size > EMERGENCY_OBJ_SIZE)
112 	goto failed;
113       while (used & 1)
114 	{
115 	  used >>= 1;
116 	  if (++which >= EMERGENCY_OBJ_COUNT)
117 	    goto failed;
118 	}
119 
120       emergency_used |= (bitmask_type)1 << which;
121       ret = &emergency_buffer[which][0];
122 
123     failed:;
124 
125       if (!ret)
126 	std::terminate ();
127     }
128 
129   memset (ret, 0, sizeof (__cxa_refcounted_exception));
130 
131   return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
132 }
133 
134 
135 extern "C" void
136 __cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
137 {
138   char *base = (char *) emergency_buffer;
139   char *ptr = (char *) vptr;
140   if (ptr >= base
141       && ptr < base + sizeof (emergency_buffer))
142     {
143       const unsigned int which
144 	= (unsigned) (ptr - base) / EMERGENCY_OBJ_SIZE;
145 
146       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
147       emergency_used &= ~((bitmask_type)1 << which);
148     }
149   else
150     free (ptr - sizeof (__cxa_refcounted_exception));
151 }
152 
153 
154 extern "C" __cxa_dependent_exception*
155 __cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
156 {
157   __cxa_dependent_exception *ret;
158 
159   ret = static_cast<__cxa_dependent_exception*>
160     (malloc (sizeof (__cxa_dependent_exception)));
161 
162   if (!ret)
163     {
164       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
165 
166       bitmask_type used = dependents_used;
167       unsigned int which = 0;
168 
169       while (used & 1)
170 	{
171 	  used >>= 1;
172 	  if (++which >= EMERGENCY_OBJ_COUNT)
173 	    goto failed;
174 	}
175 
176       dependents_used |= (bitmask_type)1 << which;
177       ret = &dependents_buffer[which];
178 
179     failed:;
180 
181       if (!ret)
182 	std::terminate ();
183     }
184 
185   memset (ret, 0, sizeof (__cxa_dependent_exception));
186 
187   return ret;
188 }
189 
190 
191 extern "C" void
192 __cxxabiv1::__cxa_free_dependent_exception
193   (__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
194 {
195   char *base = (char *) dependents_buffer;
196   char *ptr = (char *) vptr;
197   if (ptr >= base
198       && ptr < base + sizeof (dependents_buffer))
199     {
200       const unsigned int which
201 	= (unsigned) (ptr - base) / sizeof (__cxa_dependent_exception);
202 
203       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
204       dependents_used &= ~((bitmask_type)1 << which);
205     }
206   else
207     free (vptr);
208 }
209