1// -*- C++ -*- Allocate exception objects.
2// Copyright (C) 2001-2017 Free Software Foundation, Inc.
3//
4// This file is part of GCC.
5//
6// GCC is free software; you can redistribute it and/or modify
7// it under the terms of the GNU General Public License as published by
8// the Free Software Foundation; either version 3, or (at your option)
9// any later version.
10//
11// GCC is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15//
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25// This is derived from the C++ ABI for IA-64. Where we diverge
26// for cross-architecture compatibility are noted with "@@@".
27
28#include <bits/c++config.h>
29#include <cstdlib>
30#if _GLIBCXX_HOSTED
31#include <cstring>
32#endif
33#include <climits>
34#include <exception>
35#include "unwind-cxx.h"
36#include <ext/concurrence.h>
37#include <new>
38
39#if _GLIBCXX_HOSTED
40using std::free;
41using std::malloc;
42using std::memset;
43#else
44// In a freestanding environment, these functions may not be available
45// -- but for now, we assume that they are.
46extern "C" void *malloc (std::size_t);
47extern "C" void free(void *);
48extern "C" void *memset (void *, int, std::size_t);
49#endif
50
51using 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 !defined (_GLIBCXX_LLP64) && 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
76namespace __gnu_cxx
77{
78 void __freeres();
79}
80
81namespace
82{
83 // A fixed-size heap, variable size object allocator
84 class pool
85 {
86 public:
87 pool();
88
89 void *allocate (std::size_t);
90 void free (void *);
91
92 bool in_pool (void *);
93
94 private:
95 struct free_entry {
96 std::size_t size;
97 free_entry *next;
98 };
99 struct allocated_entry {
100 std::size_t size;
101 char data[] __attribute__((aligned));
102 };
103
104 // A single mutex controlling emergency allocations.
105 __gnu_cxx::__mutex emergency_mutex;
106
107 // The free-list
108 free_entry *first_free_entry;
109 // The arena itself - we need to keep track of these only
110 // to implement in_pool.
111 char *arena;
112 std::size_t arena_size;
113
114 friend void __gnu_cxx::__freeres();
115 };
116
117 pool::pool()
118 {
119 // Allocate the arena - we could add a GLIBCXX_EH_ARENA_SIZE environment
120 // to make this tunable.
121 arena_size = (EMERGENCY_OBJ_SIZE * EMERGENCY_OBJ_COUNT
122 + EMERGENCY_OBJ_COUNT * sizeof (__cxa_dependent_exception));
123 arena = (char *)malloc (arena_size);
124 if (!arena)
125 {
126 // If the allocation failed go without an emergency pool.
127 arena_size = 0;
128 first_free_entry = NULL;
129 return;
130 }
131
132 // Populate the free-list with a single entry covering the whole arena
133 first_free_entry = reinterpret_cast <free_entry *> (arena);
134 new (first_free_entry) free_entry;
135 first_free_entry->size = arena_size;
136 first_free_entry->next = NULL;
137 }
138
139 void *pool::allocate (std::size_t size)
140 {
141 __gnu_cxx::__scoped_lock sentry(emergency_mutex);
142 // We need an additional size_t member plus the padding to
143 // ensure proper alignment of data.
144 size += offsetof (allocated_entry, data);
145 // And we need to at least hand out objects of the size of
146 // a freelist entry.
147 if (size < sizeof (free_entry))
148 size = sizeof (free_entry);
149 // And we need to align objects we hand out to the maximum
150 // alignment required on the target (this really aligns the
151 // tail which will become a new freelist entry).
152 size = ((size + __alignof__ (allocated_entry::data) - 1)
153 & ~(__alignof__ (allocated_entry::data) - 1));
154 // Search for an entry of proper size on the freelist.
155 free_entry **e;
156 for (e = &first_free_entry;
157 *e && (*e)->size < size;
158 e = &(*e)->next)
159 ;
160 if (!*e)
161 return NULL;
162 allocated_entry *x;
163 if ((*e)->size - size >= sizeof (free_entry))
164 {
165 // Split block if it is too large.
166 free_entry *f = reinterpret_cast <free_entry *>
167 (reinterpret_cast <char *> (*e) + size);
168 std::size_t sz = (*e)->size;
169 free_entry *next = (*e)->next;
170 new (f) free_entry;
171 f->next = next;
172 f->size = sz - size;
173 x = reinterpret_cast <allocated_entry *> (*e);
174 new (x) allocated_entry;
175 x->size = size;
176 *e = f;
177 }
178 else
179 {
180 // Exact size match or too small overhead for a free entry.
181 std::size_t sz = (*e)->size;
182 free_entry *next = (*e)->next;
183 x = reinterpret_cast <allocated_entry *> (*e);
184 new (x) allocated_entry;
185 x->size = sz;
186 *e = next;
187 }
188 return &x->data;
189 }
190
191 void pool::free (void *data)
192 {
193 __gnu_cxx::__scoped_lock sentry(emergency_mutex);
194 allocated_entry *e = reinterpret_cast <allocated_entry *>
195 (reinterpret_cast <char *> (data) - offsetof (allocated_entry, data));
196 std::size_t sz = e->size;
197 if (!first_free_entry
198 || (reinterpret_cast <char *> (e) + sz
199 < reinterpret_cast <char *> (first_free_entry)))
200 {
201 // If the free list is empty or the entry is before the
202 // first element and cannot be merged with it add it as
203 // the first free entry.
204 free_entry *f = reinterpret_cast <free_entry *> (e);
205 new (f) free_entry;
206 f->size = sz;
207 f->next = first_free_entry;
208 first_free_entry = f;
209 }
210 else if (reinterpret_cast <char *> (e) + sz
211 == reinterpret_cast <char *> (first_free_entry))
212 {
213 // Check if we can merge with the first free entry being right
214 // after us.
215 free_entry *f = reinterpret_cast <free_entry *> (e);
216 new (f) free_entry;
217 f->size = sz + first_free_entry->size;
218 f->next = first_free_entry->next;
219 first_free_entry = f;
220 }
221 else
222 {
223 // Else search for a free item we can merge with at its end.
224 free_entry **fe;
225 for (fe = &first_free_entry;
226 (*fe)->next
227 && (reinterpret_cast <char *> ((*fe)->next)
228 > reinterpret_cast <char *> (e) + sz);
229 fe = &(*fe)->next)
230 ;
231 // If we can merge the next block into us do so and continue
232 // with the cases below.
233 if (reinterpret_cast <char *> (e) + sz
234 == reinterpret_cast <char *> ((*fe)->next))
235 {
236 sz += (*fe)->next->size;
237 (*fe)->next = (*fe)->next->next;
238 }
239 if (reinterpret_cast <char *> (*fe) + (*fe)->size
240 == reinterpret_cast <char *> (e))
241 // Merge with the freelist entry.
242 (*fe)->size += sz;
243 else
244 {
245 // Else put it after it which keeps the freelist sorted.
246 free_entry *f = reinterpret_cast <free_entry *> (e);
247 new (f) free_entry;
248 f->size = sz;
249 f->next = (*fe)->next;
250 (*fe)->next = f;
251 }
252 }
253 }
254
255 bool pool::in_pool (void *ptr)
256 {
257 char *p = reinterpret_cast <char *> (ptr);
258 return (p > arena
259 && p < arena + arena_size);
260 }
261
262 pool emergency_pool;
263}
264
265namespace __gnu_cxx
266{
267 void
268 __freeres()
269 {
270 if (emergency_pool.arena)
271 {
272 ::free(emergency_pool.arena);
273 emergency_pool.arena = 0;
274 }
275 }
276}
277
278extern "C" void *
279__cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
280{
281 void *ret;
282
283 thrown_size += sizeof (__cxa_refcounted_exception);
284 ret = malloc (thrown_size);
285
286 if (!ret)
287 ret = emergency_pool.allocate (thrown_size);
288
289 if (!ret)
290 std::terminate ();
291
292 memset (ret, 0, sizeof (__cxa_refcounted_exception));
293
294 return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
295}
296
297
298extern "C" void
299__cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
300{
301 char *ptr = (char *) vptr - sizeof (__cxa_refcounted_exception);
302 if (emergency_pool.in_pool (ptr))
303 emergency_pool.free (ptr);
304 else
305 free (ptr);
306}
307
308
309extern "C" __cxa_dependent_exception*
310__cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
311{
312 __cxa_dependent_exception *ret;
313
314 ret = static_cast<__cxa_dependent_exception*>
315 (malloc (sizeof (__cxa_dependent_exception)));
316
317 if (!ret)
318 ret = static_cast <__cxa_dependent_exception*>
319 (emergency_pool.allocate (sizeof (__cxa_dependent_exception)));
320
321 if (!ret)
322 std::terminate ();
323
324 memset (ret, 0, sizeof (__cxa_dependent_exception));
325
326 return ret;
327}
328
329
330extern "C" void
331__cxxabiv1::__cxa_free_dependent_exception
332 (__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
333{
334 if (emergency_pool.in_pool (vptr))
335 emergency_pool.free (vptr);
336 else
337 free (vptr);
338}
339